Poorer Arthroscopic Outcomes of Mild Dysplasia With Cam Femoroacetabular Impingement Versus Mixed Femoroacetabular Impingement in Absence of Capsular Repair
Purpose: To compare outcomes of mild dysplasia with cam femoroacetabular impingement (FAI) vs mixed FAI with hip arthroscopy without capsular repair. Methods: A retrospective review of a 2009 to 2010 multicenter prospective outcome study was performed comparing a cohort with mild dysplasia and cam femoroacetabular impingement (cohort D) to a cohort with mixed FAI (cohort M). Outcome measures included Nonarthritic Hip Score (NAHS) and satisfaction with minimum 2-year follow-up. Results: Of 150 patients/159 hips enrolled in the initial prospective outcome study, 10 patients/10 hips had acetabular dysplasia and 8 patients met the inclusion criteria. Cohort D had 8 patients (5 female) of mean age 49.6 years with mean lateral center-edge angle (LCEA) of 19° (range, 16°-24°) demonstrating a mean change in NAHS of +20.00 at 3 months (P = .25), +14.33 at 12 months (P = .03), and -0.75 at 24 months (P = .74). Mean satisfaction was 2.88 out of 5. Cohort M had 69 patients (32 female) of mean age 38.6 years with a mean LCEA of 33° (range, 25°-38°) demonstrating a mean change in NAHS of +12.09 at 3 months (P < .0001), + 20.39 at 12 months (P < .0001), and +21.99 at 24 months (P < .0001). Mean satisfaction was 3.58 out of 5. Cohort D demonstrated significantly less improvement in NAHS (P = .002) and a difference of -31.06 points compared to cohort M at minimum 2-year follow-up. Dysplasia was the only statistically significant predictor of poorer outcomes. Conclusion: The common combination of mild dysplasia and cam FAI has poorer outcomes than mixed FAI following arthroscopic surgery without capsular repair.
Limitations include the small number of study patients, the retrospective study design (using prospectively collected data), and the isolated use of LCEA to define dysplasia. Pereira and colleagues23 recommended using LCEA with Tönnis angle to define minor dysplasia. Although dysplasia cannot be precisely defined with only this radiographic measurement, LCEA has been shown to be a reliable, clinically relevant measure.24 In addition, LCEA has been used in most reports on arthroscopic management of dysplastic hips and thus allows for comparison. Furthermore, other studies have used LCEA of <15° as a threshold between mild and severe dysplasia, and we did as well. This broad inclusion criterion allowed for heterogeneity in our mild dysplasia cohort and was a study limitation. Interobserver reliability of measured LCEA was not assessed and is another limitation.
The initial prospective study (2009) did not record α angles to quantify cam FAI. This is a study limitation. However, the surgical range-of-motion endpoints considered sufficient for cam decompression were the same in both cohorts. In addition, femoral version was not assessed in the original database (2009-2010), as this aspect of hip anatomy was not thought significant during initial data collection. These areas of interest merit further investigation.
Use of a focal pincer cohort may be challenged as a suboptimal control group. However, there were very few completely normal acetabulae with pure cam FAI in the original prospective study, and the focal pincer cohort was used as a control cohort in previous studies.25
Conclusion
The common combination of mild dysplasia and cam FAI has poorer outcomes than mixed FAI after arthroscopic surgery without capsular repair.
Am J Orthop. 2017;46(1):E47-E53. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.
