Optimal Treatment of Cam Morphology May Change the Natural History of Femoroacetabular Impingement

Abstract

Background: There is debate in the literature whether cam morphology is associated with increased risk for hip osteoarthritis. The capability of femoroplasty to alter the natural history of cam morphology is still in question.

Purpose: To (1) investigate the correlation between cam morphology and damage to the articular cartilage and (2) assess whether correction of the cam morphology affects survivorship of the joint, progression to arthroplasty, and functional patient-reported outcome scores.

Study design: Cohort study; Level of evidence, 3.

Methods: Data were prospectively collected for patients presenting for hip arthroscopy between February 2008 and April 2017. Cases were divided into 3 groups: control group with an alpha angle <50° pre- and postoperatively, treated group with an alpha angle >55° preoperatively and <50° postoperatively, and a group with an alpha angle >55° pre- and postoperatively. All patients had minimum 2-year postoperative follow-up for the modified Harris Hip Score, the Non-arthritic Hip Score, and visual analog scale for pain. Conversion to total hip arthroplasty was recorded.

Results: A 1:1:1 match successfully yielded 98 hips for each group. Follow-up time was 50.77 ± 24.60 months (mean ± SD). The pre- and postoperative mean alpha angles were 45.2°± 3.4° and 40.6°± 4.3° in the control group, respectively; 66.2°± 8.4° and 42.3°± 5.9° in the treated group; and 68.5°± 9.4° and 61.4°± 7.6° in the alpha >55° group. Intraoperatively, the alpha >55° and treated groups had greater acetabular cartilage damage than the control group (P = .0245 and P = .0036, acetabular labrum articular disruption, respectively; P = .0347 and P = .0211, acetabular Outerbridge). The alpha >55° group achieved the patient acceptable symptomatic state for the modified Harris Hip Score (58.2%) significantly less than the treated (75.5%; P = .0100) and control (73.5%; P = .0239) groups. Progression to arthroplasty was significantly higher in the alpha >55° group (n = 17) when compared with the control (n = 8) and treated (n = 10) groups (P = .0034 and P = .0338, respectively).

Conclusion: Cam deformity was associated with higher-grade damage of the acetabular articular cartilage. An alpha angle >55° after surgery was associated with lower native hip joint survivability and less successful functional outcomes when compared with that of treated cam deformity as well as no deformity. These data suggest that correcting the cam deformity may positively affect the natural history of these patients.

Keywords: cam lesion; femoroacetabular impingement; femoroplasty; hip arthroscopy; osteoarthritis; total hip arthroplasty.