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

Abstract

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 α 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.