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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.

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