Coxa profunda: is the deep acetabulum overcovered?

BACKGROUND: Coxa profunda, or a deep acetabular socket, is often used to diagnose pincer femoroacetabular impingement (FAI). Radiographically, coxa profunda is the finding of an acetabular fossa medial to the ilioischial line. However, the relative position of the acetabular fossa to the pelvis may not be indicative of acetabular coverage. QUESTIONS/PURPOSES: We therefore determined the incidence of coxa profunda and evaluated associations between coxa profunda and other radiographic parameters of acetabular coverage commonly used to diagnose pincer FAI and acetabular dysplasia.
METHODS: We evaluated the radiographs of three cohorts for coxa profunda, lateral center edge (LCE) angle, acetabular index, posterior wall sign, and crossover sign. Data from 67 collegiate football players were collected prospectively (Cohort 1). We identified two patient cohorts through retrospective review of all 179 hips undergoing hip preservation surgery from 2002 to 2008 (83 periacetabular osteotomies [Cohort 2] and 96 surgical dislocation and osteochondroplasties [Cohort 3]).
RESULTS: In all three cohorts, we detected no difference in the LCE angle or acetabular index between hips with and without coxa profunda. Coxa profunda existed in hips representing the spectrum of acetabular coverage measured by LCE angle (-18° to 60°) and acetabular orientation determined by the crossover sign.
CONCLUSIONS: Coxa profunda was a common radiographic finding in both symptomatic patients and asymptomatic football players. Coxa profunda existed in hips representing the spectrum of acetabular coverage and was not associated with an overcovered acetabulum. We conclude coxa profunda is unrelated to overcoverage and suggest its use in diagnosis of pincer FAI be abandoned in favor of other determinants of focal or general overcoverage. LEVEL OF EVIDENCE: Level III, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.