The prevalence of cam-type deformity of the hip joint: A survey of 4151 subjects of the copenhagen osteoarthritis study

Background: Cam deformity is a preosteoarthritic malformation causing premature hip-joint degeneration. While the pathogenetic pathway from deformity to osteoarthrosis (OA) has been well established, almost nothing is known of the malformation's epidemiology. Purpose: To determine the distribution of cam deformity in a large, unselected cohort from standardized anteroposterior (AP) pelvic radiographs. Material and Methods: The distribution of cam deformity was assessed in 3202 (1184 male, 2018 female) standardized AP pelvic radiographs using the triangular index (TI) and the angle. The relationships between cam malformation and self-reported hip pain were evaluated, and the relative importance of known risk factors for cam malformation estimated. Results: We found a pronounced sex-related difference in cam-deformity distribution. The overall prevalence of cam deformity was approximately 17% in men and 4% in women. The distribution of cam deformity was unaltered in subjects with normal joint-space width or other features of hip-joint degeneration. We found no significant association with self-reported hip pain, nor did we find any relative importance of possible risk factors for hip deformity, such as body-mass index (BMI), occupational exposure to heavy workloads, or concomitant acetabular dysplasia. Conclusion:The results lend support to the thesis that cam deformity represents a silent slipped capital epiphysis, predominantly in men, and that it is a far from uncommon deformity in subjects with no apparent evidence of hip-joint osteoarthritis.