Spondylolysis in the lower thoracic–upper lumbar spine in a British medieval population

Spondylolysis is generally a condition of the lower lumbar spine, but occasionally it is observed at cranial to L4. It is generally agreed that spondylolysis in the lower lumbar spine represents fatigue failure of the neural arch. However, whether a biomechanical explanation is adequate to explain lesions cranial to L4 is disputed. Morphological aspects of spondylolysis at T12–L3 (five cases) are compared with those of lesions at L4–L6 (24 cases) in a mediaeval English skeletal series with the aim of shedding light upon any differences in aetiology of lesions at the two sites. It was found that spondylolysis at T12–L3 was more often unilateral than in L4–L6. In T12–L3, clefts more often took an angulated, dog‐leg course across the pars interarticularis, whereas most in L4–L6 were fairly straight and had an oblique orientation. In T12–L3, clefts often had facetted opposing surfaces suggestive of a diarthrodial joint, but this was only seen once in L4–L6. It is suggested on morphological grounds that facetted defects are more likely congenital than acquired. The need for consideration of factors in addition to activity regimes when interpreting spondylolysis in earlier populations is emphasised. Copyright © 2007 John Wiley & Sons, Ltd.