Hip internal rotation is correlated to radiographic findings of cam femoroacetabular impingement in collegiate football players

Purpose: The objective of this study was to determine whether physical examinations (flexion-abduction-external rotation [FABER], impingement, range-of-motion profiles) could be used to detect the bony abnormalities of femoroacetabular impingement (FAI) in an athletic population.

Methods: We performed a prospective study of 65 male collegiate football players. Both hips were evaluated by 2 orthopaedic surgeons for radiographic signs of FAI. The alpha angle and head-neck offset were measured on frog-leg lateral films. The center-edge angle, acetabular index, crossover sign, and alpha angle were measured on anteroposterior films. Measurements were averaged for both observers. Maximum hip range of motion in flexion (supine) and internal/external rotation (supine, sitting, and prone) was measured with a goniometer. Pain provoked by the impingement and FABER tests was also recorded. Examinations were completed at 2 of 4 stations (2 duplicates), each staffed by 2 clinicians (1 examined and 1 measured). The relation between each range-of-motion and radiographic measure was determined. Data from each station were assessed separately. Only those regressions significant (P < .05) for paired stations were considered clinically significant.

Results: The alpha angle and head-neck offset measured on the frog-leg lateral films were significantly correlated (all P < .01) to supine, sitting, and prone internal rotation for all stations. Correlation coefficients ranged from -0.59 to -0.35 for alpha angle and 0.42 to 0.57 for head-neck offset. Although 95% of the hips had at least 1 radiographic sign of FAI, pain was reported in only 8.5% and 2.3% during the impingement and FABER tests, respectively.

Conclusions: Internal rotation correlates to radiographic measures of cam FAI in this cohort of collegiate football players. Football players with diminished internal rotation in whom hip pain develops should be evaluated for underlying cam FAI abnormalities.

Level of evidence: Level IV, therapeutic case series.