Variations in the prevalence of spondylolysis in early British populations.

Crude prevalence rates of spondylolysis were estimated in skeletal populations from various periods. There was a steady increase in prevalence from 3.74% in Romano-British to 5.08% in medieval populations, but the rate fell considerably to 1.42% in a population from an 18th/19th century context. This trend was not statistically significant, however. The male/female ratio was approximately unity until the 18th/19th century when the expected male excess appeared. The lesions predominantly affected L5 and all were isthmic in type. Of the total of 52 cases, only four were unilateral. One occurred in the fourth cervical vertebra. There were few complications; spondylolisthesis was noted in four cases and in three there were osteoarthritic changes on the superior margin of the displaced lamina.