Alpha angle correction in femoroacetabular impingement.

PURPOSE

The predictive value of the alpha angle, currently the most validated magnetic resonance imaging parameter for CAM-impingement FAI, remains to be systematically evaluated in the orthopaedic literature. A systematic review was conducted to determine whether alpha angle correction influences clinical outcomes in patients with FAI.

METHODS

We searched three databases (MEDLINE, EMBASE and PubMed) for English clinical studies published up to August 2012, reporting surgical correction of the alpha angle in patients with a primary diagnosis of FAI. Two independent assessors reviewed eligible studies. Where applicable, the Newcastle-Ottawa Scale was used to perform a quality assessment. Descriptive statistics are presented.

RESULTS

Of the 1,103 studies initially retrieved, 14 fulfilled our eligibility criteria. Majority of studies (86 %) were case-control designs, with no randomized controlled trials. Variability existed in the surgical techniques and modalities used to measure pre- and post-operative alpha angles. All 14 studies reported a mean measured post-operative restoration of a normal alpha angle (equal to or less than 55°). Failure due to inadequate osseous correction was cited in 3/14 included studies. Correction resulted in significant improvements in range of motion and patient Visual Analog Scales, non-arthritic hip scores, Harris Hip Scores and the short-form-12.

CONCLUSION

Based on this review, there is evidence supporting that precise surgical restoration of the alpha angle in CAM-type FAI to a minimum of less than 55° will lead to improved patient outcomes. The alpha angle is a good predictor of outcome and represents a simple, reproducible and inexpensive guide that can be used intra-operatively and post-operatively.