There remains a lack of definitive evidence regarding the etiology of pars defects, though evidence is mounting in favor of micro-trauma. Approximation of the articular facets, as occurs in subjects with increased sacral base angles, may result in greater stress to this area, leading to the development of pars defects. Alternatively, pars defects may facilitate approximation of the articular facets, resulting in a higher sacral base angle. The purpose of this study was to determine whether persons with spondylolysis have greater sacral base angles compared to persons without spondylolysis. The sacral base, sacrovertebral, and lumbosacral disc angles were measured on 30 subjects with radiographic evidence of spondylolysis at L5, and on 95 radiographically normal subjects. A 26% difference in the sacral base angle between spondylolytic and normal males was discovered. The results for females were inconclusive due to the sample size. Baseline data for the sacral base, sacrovertebral and lumbosacral disc angles were established for both normal and spondylolytic males and females. No relationship was found between spondylolysis and these two angles.
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