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Bone Benefits of 3D Printing

24 Mar

Recently there has been some extraordinarily interesting articles in the press on the value of 3D printing in surgical procedures.  In particular the United Kingdom seems to be leading the way in producing and using 3D printed implants for use in reconstructive surgeries, as recent articles in the BBC, the Daily Telegraph and The Independent publications highlight.

Mr Craig Gerrand, a consultant orthopaedic surgeon in an NHS hospital in Newcastle-Upon-Tyne, England, recently announced the success of producing and fitting half of a 3D printed titanium hip into an unnamed patient who was suffering from chondrosarcoma.  Chondrosarcoma is a cancer of the cartilage cells and typically tends to affect the axial skeleton.  In this case the unnamed patient suffered severe damage to one half of his hip due to the effect of the destructive cancer.  In an effort to stop the spread of the cancer, which rarely responds to radiotherapy or chemotherapy, the surgeon was forced to remove half of the patient’s hip (termed an hemipelvectomy, which can be external or internal dependent on if the leg is to be amputated as well).

Before this, however, Mr Gerrand was able to construct and print a 3D titanium half model of the patient’s  hip which, along with the added attachment of a hip socket replacement, he was then able to implant into the patient following the removal of the chondrosarcoma affected bone.  The fake hip was based on scans and x-rays of the patient’s own hip for anatomical reasons and was fully produced using a 3D printer.  The printer used lasers to fuse together titanium powder, which slowly built up a model of the hip layer by layer.  The fake hip was then coated in a mineral into which the remaining bone in the patient’s healthy hip could fuse with, providing long-term stability during recovery and mobility.  Although the news articles on the case were only recently produced, the actual surgery itself was carried out over 3 years ago.  Wonderfully the patient continues to manage to walk with mobility aids, something that would be unthinkable if the surgeon had not been able to print and implant the titanium hip.

In other news recently, as reported by the BBC, the Welsh victim of a vicious motorcycle accident was able to benefit from the 3D printing of custom parts for use in maxillofacial reconstruction.  The use of 3D printing was used at each stage of the procedure, including the planning of the surgery and the reconstruction itself, by using titanium parts to stabilise or replace parts of the patient’s own facial bones.

Following the motorcycle accident, which severely damaged both of the patient’s zygomatic bones as well as sustaining damage to the maxilla, frontal and nasal bones, the patient’s face was reconstructed in a series of operations.  To achieve the aim of improving the patient’s face to almost pre-accident standards the surgeons scanned the skull of the individual using a CT scanner and printed the results using a 3D printer, the results of which helped to produce a symmetrical model of his skull to help plan the surgery in detail.  By using cutting guides and by being able to measure the facial skeletal anatomy directly, they managed to print titanium plates to match the symmetry of the patient’s face originally, and likely minimised the time the patient spent under anesthetic.  In the article the patient, from the city of Cardiff in Wales, movingly states how he now looks as he did before the motorcycle accident, adding that he was able to go out in public once again following the reconstructive surgery.

titaniummodelskullprinted

A model example of how the surgeons helped plan the surgery to improve the motorcycle accident man’s face with 3D printed titanium implants. The image shows the left zygomatic arch with the titanium implants in white against the model of the cranium. (Image credit: The BBC 2014).

The two innovative procedures above are fine examples of the value of integrating the latest technology into the operating theatre, but they also highlight some themes of the body and surgical intervention that interest me.  The benefits of being able to 3D print specific and specially made parts offer a ‘continuation’ for the patient of their own bodies, even with the distinct disconnect (and often intrusive procedures) between the effect of the trauma or disease process and the reconstructive attempts at re-structuring the body, as highlighted in the above orthopaedic cases.

3D printing is a fast-moving technology in the medical world, where even the possibility of being able to bioprint human organs and tissue is fast becoming a possibility for the future.  Perhaps most significantly it offers the option for the patient to use their own bodies (or, more specifically, their cells) to help cultivate a ‘second chance’ organ or tissue in the lab using artificial scaffolds to grow the tissue needed.  To a small degree this has already been carried out with certain tissues, but further work is needed to be able to bioprint human organs properly.  But back to the use of 3D printing in orthopaedic surgery.

Reconstructive orthopaedic surgery generally aims to improve the quality of life for the individual through physical manipulation and internal or external fixation of an implant onto, or into, the bone directly.  The benefits of this are not just anatomical but often also psychological, perhaps more so in maxillofacial procedures.  The patient may feel that their appearance has improved dramatically, or that they have been made to look more normal.  This can increase the positive social perception of the patient themselves and boost self-confidence.  Of course there are always risks associated with reconstructive orthopaedic surgery, the first and foremost being the fact that more damage may occur as a result of the often intrusive procedures, particularly the risk of implant fatigue and possibility of macro/micro fracture of surrounding bone material.

Internal and external fixations also often run the risk of infection, more so when there is the risk of repeated surgical interventions.  Internal fixation (such as intramedullary rodding) has the possibility of deep bone infection, whilst external fixation (such as the use of the Ilizarov frame) often results in small localised infections.  Nevertheless the risk of infection by implant is often controlled for by using clean surgical rooms, sterilised medical equipment and the infusion of antibiotics during and post-surgery.  Further to this, antibiotic laden cement is also often used during the surgical fixation of an implant as an added protector against infection through the introduction of foreign bodies.

I am also interested in the after effects of surgery in the perception of the self.  Titanium implant parts are typically manufactured for general use, although there is a dizzying variety of screws, plates and rods available to the orthopaedic surgeon.   Of course they are also shaped and made to fit the patient to a certain degree.  Titanium is a fairly hefty metal, with the patient often being able to tell that something heavy has been implanted into the body upon awakening from surgery.  It also often hammered or screwed into the bone, sometimes causing the bone to fracture or microfracture during the process, or afterwards as the patient starts to weightbear.  (As a side note orthopaedic surgeons are often built like rugby players because of the demanding physical aspect of orthopaedic surgery).

The new generation of 3D printed parts are often made of different materials than purely consisting of titanium.  Importantly there is the option to help improve the post surgical integration of existing bone and ceramic implants (such as hip replacements, which often use ceramic femoral heads) through the ability to print intricate designs to help meld with bone, and the ability to seed the ceramic scaffolds with the patients own cultured cells to promote  healthy bone growth (Seitz et al. 2005).  This is purely speculation and conjecture, but I wonder if the newer materials used, are of a much lighter material than titanium and are, as a result, less intrusive to the person undergoing the surgery?

What the 3D printing of implants offer is the opportunity to make identical and specifically made models of the  patient for their own use (Fedorovich et al. 2011), by either basing the custom build on an existing bone of the patient or by specifically making a part to improve what has either been lost to a disease process or a traumatic incident, to name the two main causes for orthopaedic reconstructive surgery.  There are also opportunities to help promote wound healing and prevent infection during and post-surgery (Lee et al. 2012), a step that is needed considering the rise of drug resistant germs, the general decline in pharmaceutical companies producing new antibiotics, and the widespread misuse of antibiotics in general (Mayo Clinic release).  3D printing then, I believe, is an important step in advancing and improving the techniques, approaches and materials used in orthopaedic surgery.

Learn More

  • Watch Ben Garrod’s Secrets of Bones BBC TV series to learn more about just how wonderful the skeleton is.  Learn more about the remarkable 3D print of his skull here.
  • Kristina Killgrove, over at Powered by Osteons, has a series of posts on her attempts to integrate 3D printing with teaching human osteology, check it out here.
  • The frankly amazing news of the Netherlands surgeons who were able to produce a 3D model of a patient’s cranium which was then successfully implanted can be found here, although there has been a lack of evidence for this procedure in other mainstream or medical publications.

Bibliography

Fedorovich, N. E., Alblas, J., Hennink, W. E., Oner, F. C. & Dhert, W. J. A. 2011. Organ Printing: The Future of Bone Regeneration? Trends in Biotechnology29 (12): 601-606.

Lee, J-H., Gu, Y. Wang, H. & Lee, W. Y. 2012. Microfluidic 3D Bone Tissue model for High-Throughput Evaluation of Wound-Healing and Infection-Preventing Biomaterials. Biomaterials. 33 (4): 999-1006.

Seitz, H., Rieder, W., Irsen, S., Leukers, B. & Tille, C. 2005. Three-Dimensional Printing of Porous Ceramic Scaffolds for Bone Tissue Engineering. Journal of Biomedical Materials Research Part B: Applied Biomaterials. 74B (2): 782-788.

Interview with Lorna Tilley: The ‘Bioarchaeology of Care’ Methodology

10 Sep

Lorna Tilley has just completed her PhD studies in the School of Archaeology and Anthropology at the Australian National University in Canberra.  Her PhD thesis focused on the behavioral and social responses to the individual experience of disability in prehistoric communities.  Lorna has developed a methodology titled the ‘bioarchaeology of care’ that contextualises, identifies and interprets care-giving in the archaeological record.  Lorna can be contacted at lorna.tilley@anu.edu.au.


These Bones of Mine: Hello Lorna and welcome to These Bones of Mine! Firstly could you tell us a little about yourself and your research interests? 

Lorna Tilley: Hello David – and thanks for having me.

I’m a latecomer to archaeology.  Ten years ago I decided I needed a change in life direction, so I returned to university to  indulge a long-held passion for prehistory.  I studied for a Graduate Diploma in Archaeology at the Australian National University (this was a ‘bridging course’ for people with qualifications in another field), and was then awarded a scholarship to undertake the PhD research which resulted in the bioarchaeology of care approach.

Stepping back, my first degree (1981) was in behavioural and social psychology – in other words, a focus on the study of human behaviour in the present, which from the very beginning provided an invaluable perspective for addressing questions about behaviour in the past – because, for me, archaeology is fundamentally about understanding people and their agency.  My background in psychology made a major contribution to constructing the conceptual foundations for the bioarchaeology of care.

I’ve had the usual range of mundane to exotic jobs, all of which are part of the life history I bring to interpreting evidence from the past.  But it’s my work in the healthcare sector that’s most immediately relevant to my archaeological research into the implications of healthcare provision in prehistory.

For example, after leaving school and through part of my first go at university I did quite a bit of nursing – in public and private hospitals and in nursing homes, including work in general nursing, care of the intellectually disabled, rehabilitation and aged care.  While I didn’t go on to qualify as a registered nurse, this hands-on experience clearly helped to inform development of aspects of the bioarchaeology of care methodology.

I’ve also helped develop public health policies and programs, and for almost a decade before beginning archaeological studies my job included advising on, monitoring and disseminating research on health outcomes assessment and health status measurement. All this fed into my work in developing a bioarchaeology of care methodology that, while qualitative and – inevitably – restricted to individual cases of care-giving, nonetheless provides a level of standardisation that allows review and replication by others.

My PhD thesis is titled Towards a Bioarchaeology of Care: A contextualised approach for identifying and interpreting health-related care provision in prehistory, so it’s fairly obvious where my research focus lies – the provision and receipt of health-related care in prehistory, and what such instances of care can reveal about both the community in which care occurred and the agency and identity of those involved in the care-giving relationship.

Being insatiably curious, however, my interests are even wider – any evidence of superficially anomalous behaviour in the past grabs my attention.  Why did the people of this community make pots in this way rather than that?  Why are people in one cemetery buried in seemingly random orientations and positions, when people in a contemporary neighbouring cemetery are all buried supine, extended and with heads to the east?  Why are stone tools found in a certain site made from materials sourced over a hundred miles away, when there is perfectly serviceable stone available in the immediate vicinity?  And so on.

TBOM: Could you explain your methodology, the ‘bioarchaeology of care’, and a bit of background as to why you thought it was necessary to produce such a method?

Lorna: Firstly, the methodology itself.  I won’t go into a lot of detail here (this would take pages), but for readers wanting more I’m attaching the text version of an invited article describing the bioarchaeology of care approach for the theme issue ‘New Directions in Bioarchaeology’, published in the Society of American Archaeologists’ journal The Archaeological Record, May 2012

In brief, the bioarchaeology of care is an original, fully-theorised and contextualised case study-based approach for identifying and interpreting disability and health-related care practices within their corresponding lifeways.  Its goal is to reveal elements of past social relations, socioeconomic organisation and group and individual identity which might otherwise slip below the radar.  And that would be our loss.

Before describing the applied methodology, some scene-setting is necessary.

In archaeology, the experience of pathology during life may be expressed in human remains through anomalies in either bone or preserved soft tissue.  Health-related care provision is inferred from physical evidence that an individual survived with, or recovered from, a disease or injury likely to have resulted in serious disability.

Following from this, I define ‘care’ as the provision of assistance to an individual experiencing pathology who would otherwise have been unlikely to survive to achieved age-of-death.  This care-giving may have taken the form of ‘direct support’ (such as nursing, physical therapy, provisioning) or ‘accommodation of difference’ (such as strategies to enable participation in social and economic activity) or a mixture of both.

I use the term ‘disability’ in the same way as the World Health Organisation – to refer to a state (temporary or longer-term) arising from an impairment in body function or structure that is associated with activity limitations and/or participation restrictions, and – very importantly – given meaning in relation to the lifeways in which it is experienced.

The central principle driving the bioarchaeology of care approach is that caring for a person with a health-related disability is a conscious, purposive interaction involving caregiver(s) and care-recipient(s).  Care is not a default behaviour – care giving and care-receiving constitute expressions of agency.

Neither does care take place in a void – understanding the context of care provision is absolutely essential in trying to understand (i) what constitutes ‘health’, ‘disease’ and ‘disability’ in the first place; (ii) the options available for care and the options selected; and (iii) what the likely choices made in relation to care reveal about the players involved.  If we can deconstruct the evidence for care within this framework, then we may be able to achieve some insights into aspects of culture, values, skills, knowledge and access to resources of the society in which care-giving occurred.  And if we can draw out some understanding of how the person at the receiving end of the care equation responded to their experience of disability we can even, perhaps, achieve some feel for aspects of this individual’s identity.

If you think this sounds deceptively easy, you’re right.  There are important caveats, and some of these are identified in the attached article.

The bioarchaeology of care methodology comprises four stages of analysis: description and diagnosis; establishing disability impact and determining the case for care; deriving a ‘model of care’; and interpreting the broader implications of care given.  Each stage builds on the contents of preceding ones.

Stage 1 is triggered by human remains showing evidence of living with, or following, a serious pathology.  It records every aspect of the remains, the pathology, and the contemporary lifeways.

Stage 2 considers the likely clinical and functional impacts of the pathology on the subject.  Modern clinical sources are used to consider likely clinical impacts.  This is legitimate because human biology is a constant; tuberculosis, for example, would elicit the same potential range of physiological responses in the past and present (it’s important to remember that each individual with this disease will respond in their own way, and that we can never recover this level of individual detail).

Estimating functional impacts involves considering likely demands, obstacles and opportunities in the contemporary lifeways environment, and evaluating the probable effects of clinical symptoms on the subject’s ability to cope with these.  For example, could the individual have carried out the most basic tasks necessary for personal survival – such as feeding or toileting themselves – often referred to as ‘activities of daily living’?  Or an individual may have been independent in this regard, but could they have fulfilled all the requirements of a ‘normal’ role (whatever that might have been for someone of their demographic) in their community?

The second stage establishes whether, on balance of probability, the individual experienced a disability requiring either ‘direct support’ or ‘accommodation’.  If the answer is ‘yes’, then we infer care.

Stage 3 identifies what – in broad terms – this care likely comprised, producing a ‘model of care’ within the parameters of the possible and the probable in the contemporary context.  The fine details of care will always be inaccessible, but basic practices – such as provisioning, staunching bleeding, massage and manipulation – don’t change.  Sometimes there may be evidence of treatment intervention in the remains themselves, but most often the practical components of treatment will be deduced from knowledge of the likely clinical and functional impacts.

Stage 4 unpacks and interprets the model of care developed over the first three stages.  It explores what the constituent elements of care-giving – singly or in combination – suggest both about contemporary social practice and social relations and about group and individual (care-recipient) identity.

I’ve presented the case of the Burial 9 (M9) so frequently over the last few years that I almost feel I know him personally – M9 was the young man from Neolithic Vietnam who lived for around a decade with total lower body paralysis and limited upper limb mobility following complications of a congenital condition (Klippel-Feil Syndrome).  His survival with (partial) quadriplegia for approximately 10 years, under very physically and psychologically challenging conditions, provides an indisputable example of past health-related care. There is simply no way that he could have survived without constant and often intensive care provision.

In the graphic that follows I’ve mapped the analysis of M9’s experience against the four stages of the bioarchaeology of care methodology described above.  More detailed information can be found in ‘Tilley, L. and Oxenham, M.F.  2011  Survival against the odds: modeling the social implications of care provision to seriously disabled individuals.  International Journal of Paleopathology 1:35-42.’ (anyone having difficulty obtaining the article can email me).

bioarchofcare

Source: Tilley (2013: 3).

You also asked me why I thought it necessary to develop the bioarchaeology of care approach.

Researching my thesis I found at least 35 publications, dating back over more than 30 years, that explicitly identify the ‘likelihood of care provision’ in respect of archaeologically-recovered individuals.  But none has analysed the evidence for care in a structured, systematic manner capable of providing access to the sort of information illustrated in the case study of M9.  It was obvious to me – particularly given my pre-archaeology experience – that a very rich source of information was being overlooked.  True, the bioarchaeology of care only allows us to look at individual instances of care-giving (this is elaborated in the attached article) – but this case study focus provides a very intimate look at broader aspects of past lifeways.  Not quantity, perhaps, but quality.

TBOM: Are there any boundaries as to when the ‘bioarchaeology of care’ model can and can’t be applied to individuals in the archaeological record?  Could you apply it to historic and prehistoric contexts, or is it mainly a tool for prehistoric cultures and periods?

Lorna: In developing the bioarchaeology of care I concentrated exclusively on evidence for health-related care-giving in small groups up to, and around, the period of the ‘early Neolithic’ – in other words, the time before the establishment of larger, more socially and economically complex, settlements.  This was entirely pragmatic – to make my task simpler, I wanted to deal with lifeways contexts in which it would be justifiable to assume that an individual with a disability would likely be known to all community members, and where it would also be justifiable to assume that, if care provision entailed substantial cost, that cost was likely to have been an impost born by the group as a whole.  This made it easier to figure out how analysis and interpretation might work.

I don’t see any reason why the bioarchaeology of care couldn’t be applied to later prehistoric and even historic settings – and actually, I’d love to do this.  It would obviously involve looking at some additional and/or different questions – for example, how might individual status within the group be related to need for, and receipt of, care?  What happens to care-giving when healthcare provision is outsourced to ‘specialist’ carers?  And how do documented approaches to healthcare (particularly in early historic periods) tally with what the archaeological evidence suggests?  Exploring such questions will be a lot more complicated than I’ve made it sound here.  But how challenging to look for possible answers!

TBOM: As stated in your 2011 article in the International Journal of Palaeopathology, the ‘bioarchaeology of care’ models the social implications of disability for the impact on not just the individual afflicted but the society as a whole, why is that such an important part of the model?

Lorna: I hope that I’ve already answered this question – at least implicitly – in what I’ve written above.  Perhaps it would be acceptable to limit bioarchaeology of care analysis to teasing out the impact of disability on the individual alone, but it would only be part of the story – and it seems to me that to stop at this point would be a criminal waste of the sparse evidence we have about  past lives and lifeways.

I think it’s quite possible that some archaeologists dealing with evidence of likely care-giving may have to stop at Stage 3 of the methodology, because not enough is known about the social, cultural and physical environment in which care was provided to enable an attempt at further interpretation.  That’s fair enough.  However, I also think that some researchers may be so uncomfortable in attempting the interpretive analysis demanded in Stage 4 that they’ll decline to do so, on the grounds that such analysis is merely ‘speculation’.  I think that’s a shame.

I don’t think there’s ever 100% certainty in archaeological interpretation. But what matters is that we approach the task of interpretation systematically, rigorously and transparently, presenting arguments in such a way that others can follow the steps taken and, where appropriate, challenge both the evidence and the reading of the evidence – refining and even recasting conclusions reached.

Even putting forward possibilities later shown to be improbable opens our minds to considering a broader vision of the past.  This sounds a bit abstract, I know – but I’d invite readers to return to the graphic summarising the bioarchaeology of care analysis of M9’s experience.  M9 comes from the Man Bac community.  Before the bioarchaeology of care analysis we knew quite a lot about how this group lived in general terms – their diet, economy, demography and mortuary customs.  But we didn’t know anything about who they were – and now I think we do.  I think the bioarchaeology of care analysis revealing the agency of caregiving can pay rich dividends.

Man Bac Burial 9 in situ

An in-situ photograph from the early Vietnamese Neolithic site of Man Bac displaying the individual known as M9 immediately before removal. Man Bac burials were typically supine and extended, but M9 was buried in a flexed position – this may reflect muscle contracture experienced in life and unbroken in death, or a deliberate mark of difference in mortuary treatment. M9’s gracile limbs show extreme disuse atrophy, a product of quadriplegia resulting from complications of Klippel-Feil Syndrome (Tilley & Oxenham 2011: 37).

TBOM: Dettwyler, in her 1991 article ‘Can palaeopathology provide evidence for compassion?’, questioned the assumptions underlying the inferences of archaeologists and human osteologists, and famously stated “what, then, can we learn of compassion from a study of bones and artifacts?” The answer must be, “practically nothing”.  How does your own methodology change or challenge this view?

Lorna: While it’s true that the title of Katherine Dettwyler’s article is ‘Can paleopathology provide evidence for compassion?’, the real argument in this article is that archaeology can tell nothing meaningful about individual experience of disability in its entirety.  The author questions whether archaeological evidence for disease can be used to infer a disability requiring care in the first place, and uses ethnographic analogy to support this position.  I’ve probably said enough about the bioarchaeology of care approach to make it clear how strongly I oppose this view.

While I greatly admire Dettwyler’s passionate support for the modern disability rights agenda – which I see as the sub-text of her writing – I disagree with almost every point she makes in her article about archaeology’s (lack of) ability to identify care and compassion in the past.  I’ll just make a couple of general observations here.

I think one of the most fundamental problems with this paper is that it doesn’t provide clear definitions of concepts central to its argument.  Disability (or ‘handicap’, a more commonly used term twenty years ago) is referred to as a purely social construct throughout, and this allows the proposition that what constituted disability in prehistory must forever be unknowable because the social values that determined disability are inaccessible through archaeological analysis.  But this ignores the reality of the at least partially ‘knowable’ clinical and functional impacts that people with health-related disabilities also have to manage in their lives.  Discerning social disadvantage may be problematic, although arguably not always completely impossible, but – as demonstrated by the bioarchaeology of care methodology – given adequate contextual information it’s possible to identify some of the likely barriers to participation in cultural, economic and physical activities that required a care-giving response.

The paper also conflates ‘care-giving’, which is a behaviour, and ‘compassion’, which is a motivation, and fails to define either.  This is of significant concern, because these terms have very different meanings.  It is undeniably easier to infer the likely provision of care-giving from physical evidence in human remains than it is to identify the motivation(s) underlying this care, which are always going to be multiple and messy – because this is simply how life is.  I believe that this semantic confusion, allied with a lack of consideration of the clinical and functional implications of disease, invalidates both the five ‘implicit assumptions’ presented by the author as underlying archaeological interpretations of disability and the paper’s criticisms of the three studies (Shanidar 1, Romito 2 and the Windover Boy) used to illustrate supposed deficiencies in archaeological claims for care.

Katherine Dettwyler’s 1991 article has had a powerful negative influence on archaeological research into health-related care-giving, and it’s widely cited in explaining why such research is ‘impossible’.

I think the bioarchaeology of care approach shows the exact opposite – not only is research into past care-giving eminently possible, but in terms of getting an insight into complex, interpersonal dynamics operating in prehistory it’s potentially one of the most rewarding areas of focus available.

TBOM: Having now completed your PhD study at the Australian National University, what is the next step for yourself and your research?  Are you continuing projects in South East Asia, with on-going excavations in Vietnam?

Lorna: I’ve got a couple of projects in mind.

Firstly, I’m hoping to turn ‘Towards a bioarchaeology of care’ into a book.  There’s already been some interest in my dissertation from (bio)archaeologists as well as from researchers in other disciplines, so I’m hoping that such a book would have an audience.  Anyone interested in exactly what my thesis covers can email me (lorna.tilley@anu.edu.au), and I’ll send you my thesis abstract.

Secondly, my thesis introduces the Index of Care, which is a non-prescriptive, computer-based instrument intended to support ‘thinking through’ the application of the four stages of the bioarchaeology of care methodology.  I describe the Index as a cross between a prompt and an aide-mémoire, and I’m planning to develop it as a web-based application freely available to anyone who wants to use it.  The present Index is in the very early beta version stage – I’m responsible for the content and interface design, and I’m open in saying that these require a lot more work!  (My partner did the actual IT production, so I take no credit for this aspect – which actually works!)  I’ll be calling for volunteers interested in helping to test and provide feedback on the Index in the near future, and I’d love to hear from anyone interested in learning more about this project.

Regarding excavations – well, immediately after submitting my thesis for examination I went out to dig for four weeks in the Northern Vietnamese pre-Neolithic site of Con Co Ngua (~6000BP).  It was great to get my hands in the dirt again after the extended dissertation-writing vigil in front of the computer!  However, analysing the over 140 remains recovered from this site will likely take years – so, even as we speak, I’m chasing up other options for expanding on the bioarchaeology of care work done to date.

The Man Bac landscape looking southwest - excavations centre right

The Man Bac excavation site in Vietnam where the individual M9 was found and excavated. The archaeological site can be seen centre right, whilst a modern cemetery takes precedence in the foreground.

TBOM: That brings us to the end of the interview Lorna, so I just want to say thank you very much for your time!

Lorna: David – and any readers that have made it this far – thank you for asking me along and for being interested.  I can’t sign off without saying how much I value this website – it is dangerously seductive in coverage and content.

Select Bibliography:

Dettwyler, K. A. 1991. Can Palaeopathology Provide Evidence for “Compassion”? American Journal of Physical Anthropology84: 375-384.

Tilley, L. & Oxenham, M. F. 2011. Survival Against the Odds: Modelling the Social Implications of Care Provision to the Seriously DisabledInternational Journal of Palaeopathology1 (1): 35-42.

Tilley, L. 2012. The Bioarchaeology of Care. The SAA Archaeological Record: New Directions in Bioarchaeology, Part II12 (3): 39-41.

For further Information on SE Asian Archaeology and it’s Bioarchaeology:

Oxenham, M. & Tayles, N. G. (Eds.) 2006. Bioarchaeology of Southeast Asia. Cambridge: Cambridge University Press.

Oxenham, M., Matsumura, M., & Nguyen, D. Kim. (Eds.) 2011. Man Bac: The Excavation of Neolithic Site in Northern Vietnam (Terra Australis 33). Canberra: Australian National University E Press.

Skeletal Series 11: The Human Foot

4 Sep

The human foot is as distinctive and as complex as the human hand (D’Août et al.  2010).  The foot, or Pes, forms the distal terminus of the leg.  It helps to perform the two basic important functions of shock absorption and propulsion during bipedal locomotion, both of which require a high degree of stability.  The foot bones are the serial homologs of the hand bones an each foot individually is comprised of 26  individual skeletal elements as opposed to the hand’s 27  individual skeletal elements, indicative of the differing evolutionary roles of both limbs with the digits undergoing reduction and modification in mammals (White & Folkens 2005: 225).

As White & Folkens (2005: 292) note, the ‘human foot has changed dramatically during its evolution from a grasping organ to a structure adapted to bipedal locomotion’, where ‘mobility, flexibility and grasping ability has been lost’.  As humans are bipedal walkers the feet must take the full weight of the body during locomotion and this is reflected in hard and soft tissue anatomy (D’Août et al. 2008, D’Août et al. 2010, Gosling et al. 2008, Jarmey 2003).  The diagram below demonstrates the robust and compact nature of the pes elements.

Foooooot

The human foot, highlighting the articulated individual skeletal elements in dorsal and lateral view. Note the arch of the foot, the size of the calcaneus and general robusticity of the bones in comparison to the hand bones (Image credit: WebMD 2013).

Excavation

The excavation of the human skeleton should, where possible, be conducted with patience and great care for the recovery of all skeletal material possible (Brothwell 1981).  The elements that make up the foot, a total of 26 individual bones altogether (see below), are sturdy and largely compact bones, although it is likely that there will not be complete recovery of the distal phalanges due to their smaller size.  In supine and crouched burials the foot bones are likely to survive, although care must be taken when excavating at an unknown burial depth (Larsen 1997).  In cremation remains of individuals from archaeological sites it is still possible for certain elements to be recognised and described, especially in the case of the compact tarsal bones (Mays 1999).  In crowded burial grounds where the body is laid out in a supine position (lying flat on the back), as n the photograph below, burials often intersect each other, cutting off the lower part of the legs (Mays 1999).  This is a common feature in crowded burial grounds, and care must be taken when excavating and assigning individual skeletal elements to specific individual skeleton’s (Brothwell 1981).

bones brodsworth 07pic3 - Copy

A photograph of a Medieval burial ground near Brodsworth, Yorkshire, UK, from the 2007 excavation. Note the orientation and sequential laying of supine burials, and how the lower portion of the legs have been covered or destroyed by other burials. Courtesy of the University of Hull and the Brodsworth project.

Basic Musculature and Skeletal Anatomy

There are 26 bones in the human foot which are grouped into 7 tarsals, 5 metatarsals and 14 phalanges, for a total of 33 joints, of which 20 are actively articulated (See image below for skeletal elements in articulation, and Gosling et al. 2008, Mays 1999, White & Folkens 2005, for further reference).  The main joints of the foot itself include the transverse tarsal joint and tarsometatarsal joint (see figure below).  The talocrural (ankle) joint, the articulation between the leg and the foot, forms an important part of the stability of the foot, one of the main differences behind the pes and the manus (the wrist is extremely movable and flexible in comparison to the ankle).  Unlike the hand the foot cannot grasp and is not capable of fine motor movement, however the adipose tissue and plantar fascia (or aponeurosis) is tightly packed underneath the heel (calcaneus bone) for shock absorption during locomotion (Gosling et al. 2008: 304).  The stability of the ankle joint is strengthened by the wedge shaped articulation of the talus and calcaneus bones and by the strong collateral ligaments helping to tightly pack the anatomy during movement (Gosling et al. 2008: 304-305).

footbones

The individual sections and bones of a right sided human foot, which includes the tarsals, metatarsals, and phalanges from proximal to distal (Image credit: Encyclopedia Britannia 2007).

It is important to note here the two main arches of the human foot, the transverse arches and the medial and lateral longitudinal arches.  The functional anatomy of the arches allows the foot to remain stable during the pressures and energy exertion of locomotion but also retain flexibility so that it can grip different surfaces whilst enhancing forward propulsion (Gosing et al. 2008: 309).  The transverse arch is located along the cuneiforms, the cuboid bone and all of the metatarsal bases, and simply forms a domed shaped which strengthens the foot during locomotion.  The medial longitudinal arch is the highest of the arches and runs along the instep of the foot, alongside the calcaneus, talus, navicular, and cuneiform bones and up to the first three metatarsals (Gosling et al. 2008: 309).  The lateral longitudinal arch is lower and flatter than the media arch and runs alongside the calcaneus, the cuboid, and the fourth and fifth metatarsals (Gosling et al. 2008: 2010).

The arches are supported in their skeletal frame by a complex arrangement of extrinsic and intrinsic muscles, ligaments and tendons.  The sole of the foot contains numerous intrinsic muscles which mimic the muscles found in the hand, which include digitorum (flexor/abductor) and lumbrical muscles, whilst the plantar view houses the inter-osseus planar muscles (Gosling et al. 2008: 284).  It is worth remembering that the majority of the larger muscles that articulate and move the foot are located in the leg itself (soleus, gastrocnemius, and the anterior/posterior tibial muscles).  Although I will not discuss the soft tissues further, I highly recommend the ‘Human Anatomy Colour Atlas and Textbook’ by Gosling et al. (2008) as a key reference source.  The book has a high number of quality dissection photographs and anatomical diagrams clearly highlighting the different muscle, ligament and tendon structures.

Skeletal Elements: Tarsals

The 7 tarsal bones of the foot help to form the longitudinal and transverse arches of the foot, which is often called the tarsus.  The talus articulates superiorly with the distal tibia and fibula, the calcaneus forms the heel of the foot and supports the talus (White & Folkens 2005: 291).  The navicular sites between the 3 cuneiforms and the head of the talus (White & Folkens 2005: 292).  The 3 cuneiforms and the cuboid act as a second row of tarsal bones and articulate with the proximal heads of the 5 metatarsals.

tarsals_labeled

Dorsal view of the tarsal elements and proximal metatarsals (Image credit: University of Cincinnati).

The Talus

The talus (astragalus in animals) is the 2nd largest tarsal and sits atop of the calcaneus, between the tibia and the fibula.  It is distinct in it’s saddle shape, with a head (that sides medially when viewed from above) and a body that forms the posterior portion of the bone.

The Calcaneus

The largest tarsal, forming the heel bone, the calcaneus is located inferior of the talus and supports the distal portion of the foot.  An intact calcaneus is extremely distinct, and can be sided by placing the ‘heel’ away from you and the articular surfaces superiorly, and the shelf (sustentaculum tali) should point the side it is from.

The Cuboid

The cuboid is located on the lateral side of the foot, between the calcaneus and the 4th and 5th metatarsals.  It is distinct in appearance because of its large size with a cuboidal body.  There is no articular surface on the lateral side of the bone, and the inferior surface has a pronounced cuboid tuberosity.

The Naviculuar

The navicular sits snugly between the talus and the cuneiform elements, and has a distinct concave proximal surface.  A tubercle points medially when viewed from the view of the talus.  It is similar in shape to the scaphoid carpal.

The Cuneiforms:

Medial

The medial cuneiform is the largest of the three cuneiforms, sitting between the navicular and base of the first metatarsal.  It is less of a wedge shape than the other two cuneiforms, and distinguished by it’s ‘kidney-shaped facet for the base of the first metatarsal’ (White & Folkens 2005: 298).

Intermediate

This cuneiform is the smallest of the cuneiforms and is located between navicular and the 2nd metatarsal base.  It articulates on either side with the lateral and medial cuneiforms.  The non-articular dorsal surface is key for siding, with a projecting surface points towards the side it comes from when the concave facet is pointed away from the holder (White & Folkens 2005: 298).

Lateral

Located at the centre of the foot, and intermediate in size between the intermediate and medial cuneiform, the lateral cuneiform sits at the base of the foot.  It articulates distally with the 2nd, 3rd and fourth metatarsal bases, proximally with the navicular, medially with the intermediate cuneiform and laterally the cuboid (White & Folkens 2005: 299).

Metatarsals

The 5 rays of the metatarsals are typically labelled as MT 1-5, with MT1 representing the hallux, or the big toe (as the thumb is named the pollex).  The metatarsals are all ‘tubular bones with rounded distal articular facets (heads) and more squarish proximal ends (bases)’ (White & Folkens 2005: 300).  They are more easily sided by the morphology of their bases.  It is important to note that each of the tarsals in the distal row (either of the 3 cuneiforms or the cuboid above) articulates with one or more of the metatarsal bases (White & Folkens 2005: 300).  The first metatarsal is the most massive and squat, whilst all non hallucial metatarsals articulate with each other.  The fifth metatarsal bears a distinctive blunt styloid process on it’s lateral side that makes it fairly identifiable.

metatarsal-phalangeal-joint

A basic dorsal view of the metatarsal and phalangeal bones in the right foot. Note that the hallux (first digit medially) has only a proximal and a distal phalanx whilst the other digits have a proximal, intermediate and distal phalanx (Source).

Phalanges

The foot phalanges are the same in design as the hand phalanges with heads, bases and shafts but are much shorter and squatter than the hand phalanges.  Again they come  in three rows, with 5 proximal phalanges4 intermediate phalanges and 5 distal phalanges;  it should be noted that the MT1 hallux has, as does the thumb (pollex), only the proximal and distal phalanges with no intermediate phalanx, and is remarkably more chunkier then either of the other four rays.

Each Proximal Phalanx displays a ‘single, concave proximal facet for the metatarsal head and a spool-shaped surface distally’ (White & Folkens 2005: 306).

Each Intermediate Phalanx displays a ‘double proximal articular facet for the head of the proximal phalanx’, and again have a trochlea shaped distal articular facet (White & Folkens 2005: 306).

Each Distal Phalanx displays a double articular proximal facet for the head of the intermediate phalanx and a terminal tip of the bone, resulting in a non-articular pad (White & Folkens 2005: 307).

These phalanges are all much shorter than their companions in the hand, with the foot phalanges having a more circular shaft cross section compared to the D shape  shaft of the hand phalanges.  Foot phalanges generally display a more constrictive shaft than hand phalanges, although it can be difficult to side them and it is best done with a full replica or whole specimens for comparative analysis (White & Folkens 2005: 308).  

Further Online Sources

  • A detailed map of each element and the surrounding musculature (as well as relaxing classical music!) can be found on the website of the UMFT Department of Anatomy and Embryology site.  Be aware there are detailed anatomical prosection and dissection diagrams, but it is a free, fascinating and wonderful source (and with the music especially relaxing!).
  • A number of websites have detailed diagrams and photographs of the foot from a medial/lateral and a dorsal/planar view, including this site and this one.
  • Finally, do you know your tarsal bones? Test yourself here!

Bibliography

Brothwell, D. R. 1981. Digging Up Bones: The Excavation, Treatment and Study of Human Skeletal Remains.  Ithica: Cornell University Press.

D’Août, K., Pataky T.C., De Clercq, D. & Aerts, P. 2009. The Effects of Habitual Footwear Use: Foot Shape and Function in Native Barefoot Walkers. Footwear Science1 (2): 81. doi:10.1080/19424280903386411 

D’Août, K., Meert, L., Van Gheluwe, B., De Clercq, D. & Aerts, P. 2010. Experimentally Generated Footprints in Sand: Analysis and Consequences for the Interpretation of Fossil and Forensic Footprints. American Journal of Physical Anthropology141: 515–525. doi: 10.1002/ajpa.21169

Gosling, J. A., Harris, P. F., Humpherson, J. R., Whitmore I., & Willan P. L. T. 2008. Human Anatomy Color Atlas and Text Book. Philadelphia: Mosby Elsevier.

Jarmey, C. 2003. The Concise Book of Muscles. Chichester: Lotus Publishing. 

Jurmain, R. Kilgore, L. & Trevathan, W.  2011. Essentials of Physical Anthropology International Edition. London: Wadworth.

Larsen, C. 1997. Bioarchaeology: Interpreting Behaviour From The Human Skeleton. Cambridge: Cambridge University Press.

Marsland, D. & Kapoor, S. 2008. Rheumatology and Orthopaedics. London: Mosby Elsevier.

Mays, S. 1999. The Archaeology of Human Bones. Glasgow: Bell & Bain Ltd.

White, T. & Folkens, P. 2005. The Human Bone Manual. London: Elsevier Academic Press.

Documentary on Fibrodysplasia Ossificans Progressiva

24 Nov

There was recently a documentary on Channel 4 (in Britain) that highlighted an individual with Fibrodysplasia Ossificans Progressiva (FOP), a progressive bone disease in which the bodies natural repair mechanism causes fibrous tissues (including ligaments, tendons and muscles) to become ossified when damaged or hurt.  Typically lumbered with the name Stone Man Syndrome, the genetic disease itself is thankfully very rare with a rough prevalence of around 1 in every 2 million people.  A total of 700 cases have thus far been confirmed out of presumed 2500 cases worldwide at the current time.  The disease is ultimately devastating for the individual affected as it can lead to full ossification of every joint in the body, whilst the ossification of the fibrous tissues is typically a very painful process.  A full introduction to the disease can be found here on the emedicine website.

The program, entitled ‘The Human Mannequin‘, dealt with teenager Louise Wedderburn’s attempts to break into the fashion industry, despite her having this terrible disease.  The information byline for the show asked if the ‘notoriously image conscious fashion industry (would) accept her?’.  However, as the program progressed, it was clear to see that Louise had the tenacity necessary and had started to make clear progress towards her ideal career by gaining work placements at well recognised fashion magazines, and by starting to make her name known in the industry through her fighting spirit.

This program clearly was not about the disease itself, but about one person realising their dreams despite the disease.  As such, there was minimal background information regarding the history of the disease or of the prognosis of Fibrodysplasia Ossificans Progressiva.  Instead this program helped to raise of the profile of a dynamic young individual who, despite having this disease, is determined to make the most of her life.  The viewer was allowed access into what life is like for a person suffering this disease, both for the drawbacks and the numerous hospital visits, but also for the everyday glimpses of how you can still live your life and make a positive impact.  I would wholeheartedly recommend watching the program if you have the chance.

Perhaps the most famous sufferer of FOP is a person called Harry Eastlack (1933-1973), who bequeathed his skeleton to medical science whilst he was alive in the hope that his bones may one day help future researchers uncover a cure or help ease the pain of fellow sufferers.  Dying just short of his 40th birthday through complications arising via FOP, Harry Eastlack had became entombed within his own skeleton towards the end of his life as every joint ossified and fused completely, leaving only his lips free to move.

A photo of Harry Eastlack’s back and ribcage, with evidence of excess bone growth and ossification of the muscles, tendons and ligaments (via IFOPA).

Today researchers and medical staff at the College of Physicians in Philadelphia and the Mutter Medical Museum use his skeleton to help test and compare lab results and learn and study about the effects of FOP via his remains; Harry’s skeleton is only one of the few existing skeletons in the world with FOP and provides a very important source of knowledge, both for the medical world and the general public.

There are no known instances of FOP disease in the archaeological record, likely because it is so rare and the fact that prehistoric/historic individuals would not have likely survived as long as individuals do today with the condition.  However it is worth reading up on the disease just in case, and I would, once again, recommend watching the program.  As so often in the fields of archaeology and human osteology, we only get to investigate the bones of the dead themselves, they cannot tell us directly their lives or suffering so we must, as osteoarchaeologists, beware of what the bones can tell us.

Further sites of interest:

Skeletal Series Part 9: The Human Hip

22 Jan
In this post I shall be discussing and looking at the three main elements that make up the human pelvis (or the pelvic girdle, a homology to the shoulder girdle).  The bones that make up the pelvis are the Ischium, Ilium & the Pubis.  The Sacrum has been discussed in an earlier post on the spine.  During the development of the hip, these three elements remain singular, fusing together during adolescence to become one single unit during early maturity to become the Os Coxa (White & Folkens 2005: 246).

The main elements in the human hip, and as a whole Referred to as the Os Coxa. NB acetabulum faces laterally.

The hip is a fantastic wealth of skeletal knowledge.  The two most basic and fundamental traits of the person, the age and biological sex of the individual, can be found in articles by Brooks & Suchey (1990) and by Patriquin et al. (2005), which both use morphological features of the pelvis to estimate sex and age of the individual under study.  Many muscles also insert and attach along the borders, rims and edges of the pelvis, especially anchoring those that are key in movement during bipedal locomotion (Schwartz 2007: 147).  The hip, and its component parts, are most distinctive in shape and size.  Odd looking, hard to figure out at first, and looking like nothing else (a top heavy hourglass is one view), the Os Coxa can can be hard to identify and orientate, especially in smaller fragments.

Juvenile ilium (top), ischium (bottom right) and pubis (bottom left) (Image credit: Bone Clones 2006).

 
Excavation
 
Unfortunately during excavation, the first thing that the pick ax, spade or trowel is likely to hit is the most anterior part of the hip, the pubic symphysis, as in most human burials the body lies prone and face up, in a supine burial (see Brothwell: 3 for other burial positions).  This can lead to destruction of this joint, which can lead to loss of information on age and sex of the individual.  However, during normal inhumation excavation the grave cut can be clearly distinguished, and a pattern of working from top to bottom or bottom to top can help limit the amount of damage during excavation (White & Folkens 2005).

The author excavating a Medieval skeleton in Germany in 2011. Note the damaged anterior aspect of the Pubic Symphysis, which is outlined in red.

 
Pelvic Anatomy and Elements:
 
Acetabulum
 
The acetabulum  makes up the socket to receive the head of the femur (thigh), and is equally made up of a portion of the three elements of the hip which fuse during early adolescence.  This joint is necessarily much more stable then the non-weight bearing shoulder joint- it is much deeper, has the ligamentum teres (a ligament that attaches to the femoral head and the hip) and is covered by much stronger and denser musculature (White & Folkens 2005: 246).  As the main weight bearing joint, the bone is also much denser with thicker cortical bone.
 
Ilium
 
The ilium is the largest of the three parts of the os coxa, and sits superiorly above the ischium and pubis, and it is often described as ‘blade like’ (Schwartz 2007: 148) as it is a thin but strong plate of curved bone.  On the lateral side of the blade, three gluteal lines (anterior, inferior & posterior) are visible which are the muscle attachment sites for the large gluteal muscles.  The main landmarks along the upper ridge is the iliac crest, which can be felt on yourself, and begins anteriorly with the anterior superior iliac spine and ends in the posterior superior iliac spine (White & Folkens 2005: 247).  The auricular surface of the medial ilium articulates with the sacrum (and is a very useful age estimator- Buckberry & Chamberlain 2002).  The greater sciatic notch is also generally a good indicator of the biological sex of the individual.

Anatomical landmarks on the right hip (Image credit: Pearson Education 2010).

Ischium
 
The ischium is the butt bone, literally the bone which takes the weight whilst we are sitting on a chair!  The key features of this element of the hip is that a lot of muscles attach to the posterior ischial tuberosity.  The ischial tuberosity muscle attachments include the origins of the hamstring muscles (semimembranosus, semitendinosus, adductor magnus & biceps femoris) (White & Folkens 2005).  Alongside the pubic bone, the ischium also includes the obturator foramen, a gap (in life covered by a membrane) where a number of internal gluteal muscles converge and provide stability for the hip.
 
Pubis
 
The pubic bone makes up the anterior part of the hip as a whole and includes a cartilaginous joint, just above the genitalia in living individuals.  The pubic symphysis, as this joint is called, is also a good indicator of biological sex because of the shape below it (the  pubic arch) and also age because of age related changes in the bony surface of the pubic symphysis (Schwartz 2007: 230).  The pubic bone also includes a superior and inferior pubic ramus, literally the corpus of the bone, which help support numerous muscle attachments, namely the adductors (adductor brevislongus & magnus) of the medial compartment of the thigh.
 

The  major landmarks of the pelvic bones in anatomical position.

Discussion

For the discussion on the hip we shall talk about septic arthritis (SA).  SA is mostly common in the hip and knee, and rarely presents in the elbow or shoulder.  Although it is rare in the archaeological record, it is nonetheless recorded in a number of examples (i.e. Yukon individuals in the Natural Museum of National History in Washington, US), and it pays to be able to recognise it (Roberts & Manchester 2010: 154).  The condition is fairly uncommon, and the aetiology of SA is when an infection reaches a joint, normally through one of three means- i) the haematogenous route (most common), ii) a penetrating injury or iii) its spread from metaphysis (Marsland & Kapoor 2008).  The bacteria, or germ, normally infects the synovial fluid which may be inflamed from disease or trauma, and ‘proliferation of bacteria cause an inflammatory response by the host with numerous leucocytes migrating into the joint’ (Marsland & Kapoor 2008: 136).

Main outcome of septic arthritis (Image credit: http://www.aidmyarthritis.com).

At this point the variety of enzymes and breakdown products that are produced helps to damage the articular cartilage very quickly, and if left will produce permanent damage (Waldron 2009: 89).  The prognosis is good if treated promptly, however in the archaeological record this is quite unlikely due to the high risks of re-infection and complications such as joint destruction, avascular necrosis (mostly at the hip) & the ‘seeding of infection’ to other places (Marsland & Kapoor 2008: 137).  Again, the diagnosis of septic arthritis in the archaeological record is hindered by confusion with similarities to tuberculous infection, and difficulties in diagnosing multiple diseases that may present themselves on any one individual (Roberts & Manchester 2010: 154).  In the hip, the surface and surrounding area (lunate surface) of the acetabulum would be highly damaged, with a rough appearance and feeling as the bony lytic destruction took hold (Waldron 2009).

Bibliography

Brooks, S. & Suchey, J. M. 1990. Skeletal age determination based on the os pubis: a comparison of the Acsádi-Nemeskéri and Suchey-Brooks methods. Human Evolution 5– N.3: 227-238.

Brothwell, D. R. 1981. Digging Up Bones: The Excavation, Treatment and Study of Human Skeletal Remains.  Ithica: Cornell University Press.

Buckberry, J.L. & Chamberlain, A.T.  2002.  Age estimation from the auricular surface of the ilium: a revised methodAmerican Journal of Physical Anthropology 119: 231-239.

Larsen, C. 1997. Bioarchaeology: Interpreting Behaviour From The Human Skeleton. Cambridge: Cambridge University Press.

Marsland, D. & Kapoor, S. 2008. Rheumatology and Orthopaedics. London: Mosby Elsevier.

Mays, S. 1999. The Archaeology of Human Bones. Glasgow: Bell & Bain Ltd.

Patriquin, M.L., Steyn, M. & Loth, S.R. 2005.  Metric analysis of sex differences in South African black and white pelvesForensic Science International 147: 119-127.

Roberts, C. & Manchester, K. 2010. The Archaeology of Disease Third Edition. Stroud: The History Press.

Schwartz, J. H. 2007. Skeleton Keys: An Introduction to Human Skeletal Morphology. New York: Oxford University Press.

Waldron, T. 2009. Palaeopathology: Cambridge Manuals in Archaeology. Cambridge: Cambridge University Press.

White, T. & Folkens, P. 2005. The Human Bone Manual. London: Elsevier Academic Press.

An Introduction to Fibrous Dysplasia & McCune-Albright Syndrome

28 Oct

Definition of Fibrous Dysplasia: ‘Fibrous dysplasia is a non-inherited metabolic bone disease in which abnormal differentiation of osteoblast maturation (which) leads to replacement of normal marrow and cancellous bone by immature bone and fibrous stroma’ (Fitzpatrick et al 2004: 1389).  Fibrous Dsyplasia (FD) can be described as either monostotic (one) or polyostotic (many), depending on how many bones are affected by the disease.  Fibrous Dysplasia lesions are often displayed as having a ‘ground glass‘ appearance on x-rays and are a distinctive radiographic feature of the disease, although it is not pathognomonic of it (Waldron 2009).  It is also noted that pathological fractures are a key defining feature of polyostotic Fibrous Dysplasia (Marsland & Kapoor 2008).  FD is described as a rare disease, with the monostotic form being more prevalent than the polyostotic form.

Definition of McCune-Albright Syndrome:  McCune-Albright Syndrome (MAS) was originally typically diagnosed and recognised when a person had any of the two of the triad of the following symptoms: polyostotic Fibrous Dysplasia, Cafe-au-lait marks and/or precocious puberty.  However it was later recognised that ‘endocrinopathies, including hyperthyroidism, growth hormone excess, renal phosphate wasting with or without rickets/osteomalacia, and Cushing Syndrome’  could be found in association with the original triad (Dumitrescu & Collins 2008: 1).  In all three systems (skin, skeletal & endocrine), the presentation and abnormality can be highly variable from person to person depending on the tissues involved and the extent of the involvement (OMIM-see below).  Estimated prevalence is 1/100,000 to 1/1,000,000, it is such a wide margin because no thorough prevalence study has been carried out in recent times (Dumitrescu & Collins 2008: 1).

————————————————————————————————————————————————–

As a person who happens to have McCune Albright syndrome, to have known to have it from the first years of life, I have become somewhat forgetful of its origin: that somewhere in the early postzygotic  divisions of my life, the disease appeared and became a part of me.  Although I am aware each day of the ramifications that the mutation of the GNAS1 gene has caused I often consider myself lucky.  Lucky in the fact that in my case it has only led to broken bones and various surgeries rather than the full expression of the endocrinopathies that can occur.  I use a wheelchair for everyday mobility with limited use of crutches, mostly used for aiding inside mobility (and sometimes excavations!).

In my personal case, the disease has most affected the main weight-bearing bones of the lower limbs (fairly typical as they are the stress bearing bones, prone to fracture from weakened bone architecture).  Generally speaking,the long bones of the appendicular skeleton tend to be bowed naturally with a pathological weakness due to the lack of normal bone density and high bone cell turnover, with the aforementioned bone lesions occurring spontaneously which sometimes lead to fracture.  This includes the bilateral deformity of the femora with which I’ve had numerous pathological fractures (Five natural transverse fractures, five elective surgery initiated) on both the left and right sides, alongside a number of fractures of the right tibia and fibula (including both transverse and hairline fractures), two on the right humerus and the 5th metatarsal in the right foot.  The shepherd’s crook deformity is the common bowing deformity with varus angulation of the proximal femur (Fitzpatrick et al 2004: online).

As stated the primary bones affected by the MAS pathological fractures are typically located in the appendicular skeleton and include the following bones in order of prevalence first:  a) femur, b) tibia, c) fibula, d) humerus and e) the ribs.  It can also affect the craniofacial skeleton with distinct abnormalities in the amount of bone growth and deformity; however this tends to lessen with age after the primary and secondary growth periods (adolescence and sexual maturity), or ‘burn out’ as it is often called by medical specialists (Dumitrescu & Collins 2008: 8).

‘An example of the shepherds crook’ deformity of the femoral neck (coxa vara) with internal fixation.

My experiences of living with McCune Albright syndrome has included numerous hospitalizations due to fractured bones and planned corrective surgeries.  This has also included large amounts of time stuck in my old friend the Thomas Splint in bed bound traction, alongside enduring a host of various corrective surgical procedures to improve the angulation of both femoral necks.  Although the initial idea following a number of fractures was to treat the femoral deformities with an Ilizarov apparatus by manipulating the bone growth every day, it was quickly decided that an intramedullary rod (nicknamed the Sheffield Rod), carried out in conjunction with osteotomies to correct the femoral neck angle during surgery, would be a much safer and further reaching goal in stabilising both femoral necks in the long term.  (A rather wonderful digital video of a rod being inserted/hammered in can be viewed here).  Five major elective intramedullary rod surgeries later (3 for the left femur and 2 for the right femur!), and it seems as if they have thus far stabilised each femoral shaft/neck enough for them not to fracture again.  However this is also due to using the wheelchair much more extensively than before!

I also have had surgery to stabilise the right tibia and fibula.  This was decided after having undergone three accidental fractures of the right tibia and fibula with a space of 5 years (when the tibia breaks the fibula often follows because of their connection via the interosseous membrane), with each fracture requiring many months in plaster in order for the bone to heal.  Again this surgery included osteotomies of the tibia and fibula to improve the angle of the bone (and thus improve the bio-mechanical loading of the lower leg) and included the fixation of the tibia by means of a titanium plate.  It was hoped that an intramedullary rod could be inserted into the tibia after the tibial osteotomy but the risk of massive blood loss (an outcome of the porous bone and increased heartbeat/blood flow) and the presence of porous cortical bone meant that the tibia was probably unlikely to be able to ‘hold’ the rod in place.

I have also fractured the right humerus twice, with the second transverse fracture resulting in the fixation of the humerus with a permanent titanium plate and associated screws.  This is similar to my right tibia which has a permanent titanium plate and screws to fixate the bone and alleviate some of the pressure of walking.

I have undertaken treatment using biphosphonphates (in my case the drug pamidronate) to increase the bone density itself over a number of years in the past when I was a teenager, but the resultant bone density scans (taken at intervals before, during and after the treatment) showed little improvement and treatment was subsequently stopped.  Upon further reading into this it seems there are possible problems for long term users of biphosphonates.   This can include the higher risk of fracture after long term use due to the bodies inability to metabolize the drug and the natural effect of the biphosphonate inhibition on the bone cell turnover rate (Ott 2005: 31897).  There are many cases though where drug treatment has proved beneficial; however each case should be merited individually and each person monitored as appropriate.  I will stress here that there are many different types of biphosphonates available and that McCune Albright Syndrome varies in its intensity.

X ray of my left femur and hip with a locking intramedullary rod and screws.  Although please note that two of the femoral neck screws have now been taken out.

Although this is just a short post on the introduction to the disease that is sharing life with me it can also be found in the archaeological record.  Waldron (2009: 214) points out that Fibrous Dysplasia is often best diagnosed in an archaeological skeleton by the noting of either a shepherd’s crook deformity, healed fractures and findings of expansile swellings on one or more bones.  Subjecting the suspected sample to X-ray should show ‘lucent areas with endosteal scalloping and sometimes a thick sclerotic border’  (Waldron 2009: 215).  Unlike today’s vast array of modern medical treatment and surgical procedures, people in the past largely had to make do and mend.

As Roberts & Manchester (2010) discuss in their book, fracture treatment in the medieval age and before was fairly adept at helping in supporting and stabilising the fracture site.  However with repeated breaks in the main weight supporting bones, it is doubtful whether one could have led a normal life if the fractures were not reduced properly or repeatedly after continual breaks (Oakley 2007).  It also should be noted here that due to the nature of McCune Albright Syndrome it is unlikely to be described in the archaeology record as human skin rarely preserves.  It is far more likely that Fibrous Dysplasia is diagnosed based on the skeletal remains.

In the archaeological record Fibrous Dysplasia remains a rare and elusive disease to diagnose, whilst is has actively been described and documented in more recent human remains (Nerlich et al. 1991).  The following two case studies highlight individual cases of where Fibrous Dysplasia has been documented in archaeological material.

A recent case study presented by Craig & Craig (2011) discusses a juvenile skeleton with evidence of polyostotic Fibrous Dysplasia.  The skeletal remains of a child aged 7 years presents with Fibrous Dysplasia with evidence of involvement most noticeable with large bone expansion on the left mandible alongside involvement of the temporal, maxilla, parietal and frontal craniofacial bones.  A review of the burial context of the skeleton and of the Anglo-Saxon cemetery population that the child comes from shows no differentiation between this and other burials, indicating no differentiation in the disposition of this child’s body or associated grave goods.  Craig & Craig (2011) also cite further Ango-Saxon literature to suggest that it is highly unlikely that the child was stigmatized due to his disability, although we can never know for sure.

Recent evidence in a 120,000 year old Neandertal individual from the Upper Pleistocene site of Krapina in present day Croatia highlights the likely evidence for Fibrous Dysplasia presence in a small rib fragment (Monge et al. 2013).  This is extremely rare to find a bone lesion or tumour  in skeletal material from such a period and it is extremely exciting.  The rib was allocated original as a faunal remain when the site was initially excavated, but the rib was recognised for being of Neandertal origin by sharp eyed human osteology legend Tim D. White (Monge et al. 2013).

X ray of the transverse fracture of my right tibia and fibula in the summer of 2009.  This was the first of three transverse fractures of the right tibia and fibula that followed in quick succession over a short number of years, and resulted in the fixation of the tibia with a permanent titanium plate.

Below are some medical and non-medical sources of information on the various aspects of both Fibrous Dysplasia & McCune Albright Syndrome (FD and MAS). This includes a few recent palaeopathology articles that are freely available, medical articles discussing both FD and MAS, core palaeopathology textbooks and support groups in the US and UK for sufferers of the bone disease.  Although the disease is not headline grabbing news, the lack of research into the socio-economic aspects of the disease is distinctly lacking, as is the number of foundations or adult support services for sufferers with the disease.

I am thankful for the support of my friends, family & my consultant in the treatment of this syndrome and for continued support given.

N.B. The origin of the Ilizarov frame is particularly interesting.  It was first used in the 1950s in the USSR, with Dr Gavril Ilizarov originally using bicycle wheel spokes to fixate, support and lengthen badly fractured bones.  It was only introduced to the West in the 1980’s as a direct result of Ilizarov’s corrective surgery on a patient in Italy when all other options had failed in healing the patient’s fractures.  So far I have managed to avoid having the frame but it is still a standard procedure for badly fragmented fractures, in particular it is often used after motorbike accidents or reconstructing limb angulation/length.

Bibliography and Further Sources:

Fibrous Dysplasia:

Medical Articles:

  • Lee, J. S. FItzgibbon, E. J., Chen, Y. R., Kim, H. J., Lustig, L. R., Akintoye, S. O., Collins, M. T. & Kaban, L. B. 2012. Clinical Guidelines for the Management of Craniofacial Fibrous Dysplasia. Orphanet Journal of Rare Disease. 7 (1): 1-19..
  • Marsland, D. & Kapoor, S. 2008. Rheumatology and Orthopaedics. London: Mosby Elsevier.

McCune-Albright Syndrome:

Medical Articles:

Palaeopathology:
  • Aufderheide, A. C. & Rodríguez-Martín. C. 1998. Cambridge: Cambridge University Press. (pg.420-421).
  • Roberts, C. & Manchester, K. 2010. The Archaeology of Disease Third Edition. Stroud: The History Press.
  • Waldron, T. 2009. Palaeopathology: Cambridge Manuals in Archaeology. Cambridge: Cambridge University Press.
General Medical
  • Pub Med, a US National Library of Medicine website.

Skeletal Series Part 3: The Human Skull

22 Apr

In this post I will be discussing the basics of the human skull; its anatomical features, number of elements, terminology, key functions and how to handle a skull.  Alongside the earlier blog on variations in human skeleton and the ethics that should be considered, this should prepare the user for interaction and identification of physical remains.

A skull in situ. From the Gadot archaeological site in Israel.

Individual elements found in the human skull, individual elements discussed below (Pearson Education 2000).

 The human skull is one of the most complex structures in the human skeleton.  It houses the foundations for the sense of smell, sight, taste & hearing, alongside the housing of the brain.  It also provides the framework for the first processes of digestion by mastication of food with the use of the teeth anchored in mandible and maxilla bones (White & Folkens 2005: 75).  White & Folkens (2005) go on to note that it is of value that the key anatomical landmarks of the skull are noted.  These include the Orbits of the eye sockets, the Anterior Nasal Aperture (nose hole), External Auditory Meati (ear canals), the Zygomatic Arches (cheek bones) along with the Foramen Magnum (base of the skull).  It is by these landmarks that we can orientate the skeletal elements if they are disarticulated or have been broken (White & Folkens 2005: 75).

Excavation

Particular care should be taken when excavating the skull, or any human skeletal element.  Careful consideration should be made of its location, burial type, any nearby skeletons, and of course any different stratigraphic (colour/cut/fill) features present should be noted (Mays 1999).  As this is the only chance to lift the skeleton since deposition, careful notes should be made on first impression and any post depositional changes that can be immediately identified.  Careful sieving of the soil matrix around the skull should take place, to help retain any small fragments of bone or lose teeth (whole and partial fragments) (Mays 1999).  Differential preservation, dependent on deposition & burial environment conditions, will mean that it is likely sections of the skull will not survive.  These are often the small, delicate bones located inside the cranial-facial portion of the skull.  The likeliest to survive portions are the mandible and the cranial plate elements because of their tough biological nature.

Handling

When handling the skull it should be noted of the above major landmarks.  For example, you will not damage the skull whilst carefully holding it in both your hands but if you hold it by the orbits you are liable to damage the surrounding bone.  The foramen magnum is usually stable and strong it to withstand creeping fingers as a hold place.  Whilst studying the skull on a desk, a padded surface should be provided for it to rest upon.  Care should be taken when handling the mandible, and temptation should be resisted in testing the mechanical properties of the surrounding bone (Mays 1999).

Anatomical Planes

For use between comparative material, it is useful to use a standardized set of viewing planes.  The human skull is often viewed via the Frankfurt Horizontal (White & Folkens 2005).  The FH is a plane of three osteometric points conceived in 1884 (see above link).  The skull is normally viewed from six standard perspectives.  These include norma verticalis (viewed from above), norma lateralis (viewed from either side), norma occipitalis (viewed from behind), norma basilaris (viewed from underneath) and norma frontalis (viewed from the front). Thus, when considered with osteometric points, measurements can be taken and compared and contrasted (White & Folkens 2005: 86).

Cranial Terminology and Elements

  1. The Skull refers to the entire framework including the lower jaw.
  2. The Mandible is the lower jaw.
  3. The Cranium is the skull without the mandible.
  4. The Calvaria is the cranium without the face portion.
  5. The Calotte is the calvaria without the base of the skull.
  6. The Splanchnocranium is the facial skeleton.
  7. The Neurocranium is the braincase.

The skull in infants is made up of 45 separate elements but as an adult it is normally made up of 28 elements (including the ear ossicles) (White & Folkens 2005: 77).  The Hyoid bone (the ‘voice box’ bone) is generally not included in the count of skull bones.  The identification of the elements can be made hard as idiosyncratic differences, and fusion between plates of the cranium, can lead to differences.  A number of elements in the human skull are paired elements; simply that they are part of two identical bones in the skull.  Alongside this there are also separate elements.  The list is below-

Paired Elements

  1.  Parietal bones- Located form the side and roof of the cranial vault.
  2. Temporal bones- Located laterally and house the Exterior and Interior Auditory Meatus.  They also include the Temporomandibular Joint (TMJ for short), the
  3. Auditory Ossicles– The malleus, incus and stapes (6 bones altogether) are located in both of the ears, very near the temporal bones (Very often never recovered in archaeological samples).
  4. Maxillae bones- Located proximal to the mandile, houses the upper jaw.
  5. Palatine bones- Located inside the mouth and forms the hard palate and part of the nasal cavity.
  6. Inferior Nasal Conchae bones- Located laterally inside the nasal cavity.
  7. Lacrimal bones- Located medially in the orbits.
  8. Nasal bones- Located distally to the frontal bone, helping to form the upper nose.
  9. Zygomatic bones- They are the cheekbones.

‘Norma Lateralis’ view of the human skull (Pearson Education 2000).

Single Elements

  1. Frontal bone- Located anterior, it is the brow of the skull.
  2. Occipital bone- Located to the rear of the skull, houses the Foramen Magnum.
  3. Vomer bone- Located in the splanchnocranium, and divides the nasal cavity.
  4. Ethmoid bone- A light and spongy bone located between the orbits.
  5. Sphenoid bone- Located inside the front of the splanchnocranium, a very complex bone.
  6. Mandible bone- The lower jaw.

‘Norma Frontalis’ view of the human skull, note the large orbits (Pearson Education 2000).

‘Norma Basilaris’ view of the human skull, note the foramen magnum where the spinal chord enters the skulls to connect with the brain (Pearson Education 2000).

‘Intracranial Superior’ view of the human skull, again note the foramen magnum where the spinal chord enters the skull to join the brain and the thickness of the outer and inner cortical bones of the skull (Pearson Education 2000).

General Discussion

The human skull is a complex part of the body.  It is key in identification of sex by the size of the Mastoid Process, Supraorbital Torus, tooth size, and the squareness of the mandible amongst others; it can also be used in describing age at death by tooth wear, Cranial Suture closure and general porosity of the bone (Roberts & Manchester 2010, White & Folkens 2005, Jurmain et al 2011).  A later post will detail exactly how in further detail.

It has also changed as our species, Homo Sapiens, evolved from earlier hominids.  The morphology of the human skull has certainly become more gracile, and as an indicator and outcome of the agricultural revolution, it seems our mandibular size and muscle robusticity has slowly become less pronounced (Larsen 1999: 230, Jurmain et al 2011).  As Larsen remarks (1999: 226), it is the influence of environment and mechanical behaviour that helps determine the morphology of the skull, alongside considered genetic factors.  It is important we keep this in mind as we look at archaeological material.  Studying population trends in both temporal, cultural and geographic contexts can have important results and can also highlight long term trends.

One such trend is the discussion that a change to a more ‘globular cranial change in the Holocene represents a compensatory response to decrease in functional demands as foods become softer’ (Larsen 1999: 268).  This is underscored in archaeological populations worldwide that consumed abrasive foods with populations that consumed non abrasive foods.  By being affected by food production processes & the nature of the food itself, the morphology of the cranial facial biomechanics has changed to adjust to differing food sources.  This change has influenced cranio-facial size and morphology, occlusal abnormalities, tooth size, dental trauma, and gross wear from masticatory and non-masticatory functions (Larsen 1999: 269, Waldron 2009).

Case Study: A Mesolithic-Neolithic population trend in Ancient Japan

One example of the importance of cranial studies, and of the skull in general in archaeology, is the discussion of population change during the end of the Jomon period of Japan.  Lasting roughly from 14,000 BC to 300 BC, the Jomon culture has evidence for the earliest use of pottery in the world, and made extensive use of the large variety of environments in the Japanese archipelago (Mithen 2003).  This culture has been classed as largely hunter-gather-forager in lifestyle, until roughly the Yayoi period around 300 BC; when the adoption to agriculture was fully implemented with intensive rice agriculture, weaving and the introduction of metallurgy (Mays 1998: 90).

The evidence suggests that the Yayoi were settlers from mainland Asia, with the evidence from craniometric studies and dental studies of both Jomon and Yayoi populations, alongside a comparative study with the modern day aboriginal Ainu people who inhabit the island of Hakkaido, north of mainland Japan.  The Ainu population themselves maintain that they are the descendents of the Jomon people, and with the skeletal data of skull morphology in the modern population compared to the Jomon archaeological data set, the evidence seems to match (Mays 1998: 92).  Population pressures during the end of the Jomon period and movement of the Jomon culture is therefore suggested as a geographic movement.  The skeletal data from the modern day Ainu population, concentrated in Hokkaido, provide evidence of a Jomon movement north due to pressure, as mainland Japanese modern population cranial measurements shows a mix of origin (Mays 1998: 90).

The importance of this work highlights the movement of the adaptation of agriculture in a relatively late time frame, in comparison to mainland Asia and Europe.  The palaeoenvironmental evidence suggests the richness and diversity of the Japanese archipelago, with heavy densities of the Jomon population in 3500 BC located in central and eastern Japan (Kaner & Ishikawa 2007: 2).

Stable village sites with pits dwellings, storage areas and burial facilities have been excavated and studied, yet there is only a hint of cultivating nuts and plants.  Ongoing date conflicts with AMS results from human and animal bone have suggested the impact of the Yayoi culture to be pushed back to 1000 BC or 900 BC.  However the results could be contaminated with the ‘marine radiocarbon reservoir effect’, a natural distortion of dates and thus a possible need to recalibrate existing dates (Kaner & Ishikawa 2007: 4).  The outcome of the timing of adoption of agriculture in the Late Jomon/Yayoi period is still hotly debated. Yet the archaeological and osteoarchaeological evidence presents a hunter gather society managing to thrive without agriculture in diverse environments until later cultures and migrations of people came into contact with the Jomon culture (Mays 1998).

Further Information

Bibliography

Jurmain, R. Kilgore, L. & Trevathan, W.  2011. Essentials of Physical Anthropology International Edition. London: Wadworth.

Kaner, S. and Ishikawa, T. 2007. ‘Reassessing the concept of ‘Neolithic’ in the Jomon of Western Japan’. Documenta Preahistorica. 2007. 1-7.

Larsen, C. 1997. Bioarchaeology: Interpreting Behaviour From The Human Skeleton. Cambridge: Cambridge University Press.

Mays, S. 1999. The Archaeology of Human Bones. Glasgow: Bell & Bain Ltd.

Mithen, S. 2003. After The Ice: A Global Human History, 20,000-5000 BC.London: Weidenfeld & Nicolson.

Roberts, C. & Manchester, K. 2010. The Archaeology of Disease Third Edition. Stroud: The History Press.

Waldron, T. 2009. Palaeopathology: Cambridge Manuals in Archaeology. Cambridge: Cambridge University Press.

White, T. & Folkens, P. 2005. The Human Bone Manual. London: Elsevier Academic Press.

Skeletal Series Part 1: Bone Variation & Biomechanics

10 Apr

In the following series of blog posts I aim to cover each of the main skeletal elements.  Each post will have a single focus on a bony element, from the skull down to the bones of the foot.  Firstly though we must deal with the variation that human osteologists and bioarchaeologists will see in individual skeletons, and in a population series.  It is both useful and informative to learn the differences and the effects caused by the 4 main variation factors in the morphology of human bones.  As it is by ascertaining the degree of influences that the variation factors can cause that we can begin to understand the individual, and the skeletal series of a population, in a more informative and considered way.  The second part of this entry will focus on the basics of biomechanics, and the influences certain lifeways can have on bone.

The basic biology of bones was previously discussed in this post here, and of teeth here.  Bone in its natural state must be recognised as a changing living organism throughout life that responds to stress, both nutritional and mechanical, and remodels accordingly.  It is also must be remembered that bone is a composite material, and is able to heal itself.

Variation 1 : Ontogeny

Ontogeny is simply growth and development of an organism, in this case Homo sapiens.  The archaeological record of skeleton remains include unborn individuals right through to individuals in their 70th year and beyond.  Typically there are 7 classification groups of human age groups.  They run from Fetus (before birth), Infant (0-3 years), Child (3-12 years), Adolescent (12-20 years), Young Adult (20-35 years), Middle Adult (35-50 years), and Old Adult (50+ years) (White & Folkens 2005: 364).  Differences in bone structure, and in the growth of different bone elements often manifest themselves in changes in size and shape.

Adult with Two Juvenile Remains, From Southern Sahara

Basic Growth Profile for Homo Sapiens, Notice the Large Cranium and the Way the Body Catches Up.

Variation 2: Sexual Dimorphism

Humans are sexually dimorphic, that is there are differences between the female and male body size.  Although not as distinct between our cousins such as the gorillas, female human skeletal remains are relatively smaller in both bones and teeth size (Jurmain et a 2010).  Such skeletal variation is also manifest in the requirement of reproductive functions in the female skeleton, thus we are also often able to tell sex from skeletal remains (White & Folkens 2005: 32).

Generalised Male:Female Sexual Dimorphism

Variation 3: Idiosyncractic Differences

The idiosyncratic  (or individual) differences found in skeletons are simply natural variations, in the understanding that every body is different, and rarely are people exactly the same (identical twins excluded).  Idiosyncratic differences in bone affect the size and shape of the bone, and the topography of the bone surface.  Again, such variation is very common in human skeletal remains (White & Folkens 2005: 32).

Disarticulated human bone from the site of Armana, ancient Egypt.

Variation 4: Geographic or Population-Based

As White & Folkens point out ‘different human groups can differ in many skeletal and dental characteristics’ (2005: 32).  Thus this geographic variation can be employed to assess population affinities between skeletal series.  This trait can be quite useful in determining commingling of certain populations in prehistoric skeletal series as certain environmental and genetic traits can be passed on.

Biomechanic Basics

So these are the four main variations we should be aware of when we are looking and studying individual skeletons or a series of a population.  By considering these four main variations we can study the individual’s life pathway alongside other lines of investigation.  What we must also take into account next are the basics of biomechanics.  Biomechanics is the application of engineering principles to biological materials, whilst remembering that bone can remodel and change according to pressures put upon the bone.  As Larsen states that ‘the density of bone tissue differs within the skeleton and within individual bones in response to the varying mechanical demands’ (1997: 197).  It must be remembered that the response of human bone to ‘increased loading is in the distribution of bone (geometric) rather than density or any other intrinsic material property of bone’ (Larsen 1997: 197).

Importantly it is noted that Human bone is anisotropic, meaning its mechanical properties vary according to the direction of the load.  Importantly, Wolff’s Law highlights how bone replaces itself in the direction of functional demand.  A classic example of the remodelling capabilities of bone is that of the tennis player who has thicker cortical bone in their dominant arm.  This manifests itself in thicker cortical bone alongside hypertrophy of the muscle attachment sites.  One study carried out found that ‘males have a 35% increase in the cortical bone in the distal humerus of the playing arm vs the non-playing arm’, helping to exemplify Wolff’s Law (Larsen 1997: 196).  That study was an example of bilateral asymmetry humeral loading.  Alongside, it is the action of the main forces acting on human bone that help to change the bone, these  include a) compression, b) tension, c) shear, d) torsion & E) compression + tension+ bending.

Wolff’s law states that healthy load bearing bone (LBB) responds to strain by ‘placing or displacing themselves (at a mechanical level) in the direction of the functional pressure, & increase or decrease their mass to reflect the amount of functional pressure’, often muscular strain and/or weight bearing pressures (Mays 1999: 3).  As a part of this Frost (2004: 3) argues that the ‘mechanostat’, a tissue level negative feedback system, involves ‘two thresholds that make a bone’s strains determine its strength by switching on and off the biologic mechanisms that increase or decrease its strength’.  However, Skerry (2006: 123) has argued that there are many ‘mechanostats’ operating on the LBB and that different elements throughout the skeleton require different strain magnitudes for maintenance. Furthermore Skerry (2006: 126) also notes that differences are apparent between the sexes, and that genetic constitution, concomitant disease, exercise & activity patterns must be considered.

A recent article has also highlighted how the femoral neck width of obese people changes to accommodate the added weight.  In this case the width of the femoral neck has increased to dissipate weight throughout the bony area by increasing surface area and strength through redistribution of bone.  This is an example of active bone remodelling adapting to changes that the person has gone through in life.

An archaeological example of the above will now be taken from Larsen 1997.  ‘In the Pickwick Basin of northwestern Alabama, analysis carried out on both femora and humeri cross-sectional geometry has helped to reveal a number of differences between earlier Archaic Period hunter-gatherers and later Mississippian Period agriculturalists‘ (1997: 213).  From the femora measurements it seems that the both female and male agriculturalists had a greater bone strength, whilst analysis of male humeri shows little difference between the two series.  This has helped to show that activity levels increased for males but only in the lower limbs, as evidenced by the cross-section geometry.  However, for females of both time periods both humeri and femora strengths increased.  The article cited in Larsen (1997), Bridge 1991b, findings indicate that changes are from a greater range of activity undertaken by females than males.  With palaeopathological signs of osteoarthritis, it is concluded that the shift to food production,in particular maize production, may have had a relatively greater impact physically on women in this setting.

The next post will focus on ethics in human osteology, and from there we will consider each of the anatomical skeletal elements in context of their relative limb.

Bibliography

Frost, H. M. 2004. (A 2003). Update on Bone Physiology and Wolff’s law for Clinicians. Angle Orthodontist.  February 2004. 74 (1): 1-15.

Jurmain, R. Kilgore, L. & Trevathan, W.  2011. Essentials of Physical Anthropology International Edition. London: Wadworth.

Larsen, C. 1997. Bioarchaeology: Interpreting Behaviour From The Human Skeleton. Cambridge: Cambridge University Press.

Mays, S. 1999. The Archaeology of Human Bones.Glasgow: Bell & Bain Ltd.

Skerry, T. M. 2006. One Mechanostat or Many? Modifications of the Site-Specific Response of Bone to Mechanical Loading by Nature and Nurture. Journal of Musculoskeletal & Neuronal Interaction. 6 : 122-127. (Open Access).

White, T. & Folkens, P. 2005. The Human Bone Manual. London: Elsevier Academic Press.