Summary

A matched control study with minimum 2-year outcomes demonstrating equivalent improvements between hip arthroscopy patients with acetabular overcoverage and controls with normal acetabular coverage, with the hypothesis that the inferior overcoverage outcomes described in previous studies may be associated with excessive rim resections that increase contact pressures through the hip joint.

Abstract

Background

Patients with pincer-type femoroacetabular impingement are now routinely treated with hip arthroscopy to correct osseous deformities and treat symptomatic labral tears. A recent publication demonstrated inferior outcomes in patients with acetabular overcoverage compared with controls with normal acetabular coverage. Casual observation of our long term prospective database suggested equivalent improvements following arthroscopy between these two groups. This prompted a similar matched analysis, with the hypothesis that excess rim resection in patients with pincer-type morphology may increase loads through the hip joint and lead to lesser improvements, even when post-operative acetabular coverage remains within the normal range.

Purpose

To compare minimum 2-year outcomes of hip arthroscopic surgery in patients with acetabular over-coverage and matched controls with normal acetabular coverage.

Methods

Data collected prospectively from patients receiving primary hip arthroscopy between January 2010 and July 2016 by a single surgeon were reviewed to identify those with pincer-type morphology, defined by a lateral centre angle (LCEA) of >40°. This group was matched according to sex, age within 5 years, degree of chondral damage or osteoarthritic progression and surgery date in a 1:1 ratio with controls with a LCEA between 25° and 40°. Exclusion criteria included any previous hip surgery or hip conditions. Radiographic measurements of coverage, intra-operative findings and procedures, and minimum 2-year outcomes were recorded, including the 12-item International Hip Outcome Tool (IHOT12), Non-Arthritic Hip score (NAH), Hip Osteoarthritis Outcome Score (HOOS), visual analogue scale (VAS) for pain, patient satisfaction, and rates of revision hip arthroscopy and conversion to total hip arthroplasty (THA).

Results

A total of 159 hips (129 patients) met the inclusion criteria for the pincer (overcoverage) group and 942 hips (787 patients) met the inclusion criteria for the control (normal coverage) group. The pincer group (aged 33.5 ± 11.8 years) did not differ in age from controls before matching and had significant pre-operative radiological overcoverage compared to the control group: LCEA 44.5°±3.5° compared with LCEA 32.9°±4.1° respectively (P < .001). A greater proportion of pincer hips showed severe chondral damage compared to all eligible control hips (21.4% versus 13.8%; P = .002), but this was equalized in the matching process. No differences in improvement in patient-reported outcomes were observed between matched groups: IHOT12 improved by 35 points in both groups (P = .9 for ANOVA interaction, indicating no between-group difference in change) and NAH by 22 points in the pincer group and 21 points in the control group (P = .6). There was no difference in patient satisfaction between the groups: 86% of the pincer group definitely or probably would have the surgery again versus 90% of the control group (P =.2). Revision and conversion to THA did not differ between pincer hips and eligible or matched controls: a total of 11 (6.9%) pincer hips required subsequent revision surgery and 2 (1.3%) required THA.

Conclusion

There were no differences in any hip arthroscopy outcomes for pincer-type morphology compared to normal acetabular coverage, and both are associated with significant improvements in outcomes at minimum 2-year follow up.