Group 2 had significantly better clinical outcomes than Group 1 at one year (p = 0.0001) and at two years (p = 0.01). According to the system of Streck13 for grading the overall Merle d'Aubigné score, 28% (seven) of the twenty-five hips in Group 1 had an excellent result at two years, 48% (twelve) had a good result, 20% (five) had a moderate result, and 4% (one) had a poor result, whereas 80% of the thirty-five hips in Group 2 had an excellent result, 14% had a good result, and 6% had a moderate result at two years. There were no poor results at two years in Group 2. The increase in the overall Merle d'Aubigné score was 15% in Group 1 but twice that (30%) in Group 2 (p = 0.001). The average pain score was improved by 59% in Group 1 and by 73% in Group 2 (p = 0.0009). In both groups, there was a high correlation between pain and the overall clinical outcome (r = 0.85; p < 0.0001). There were no surgical complications in either group.
Group 2 had significantly less radiographic evidence of progression of osteoarthritis at one year (p = 0.02) and two years (p = 0.009). In Group 1, the average Tönnis grade doubled from 0.6 preoperatively to 1.2 at one year (p = 0.002) and remained nearly the same (1.3) at two years (p = 0.01) (Table I). In Group 2, the Tönnis grade at one year was the same as the preoperative value (0.5) but the score progressed slightly to 0.8 at two years (p = 0.0027). No significant correlation was found between the Tönnis grade and the overall Merle d'Aubigné score (r = 0.3; p = 0.4) or between the Tönnis grade and the Merle d'Aubigné pain score (r = 0.3; p = 0.78). All patients were seen radiographically to have a normalized acetabular orientation and depth and a restored femoral head-neck offset at one and two years postoperatively.
Labral tears have been described in association with hip dysplasia, with trauma, and, most recently, with femoro-acetabular impingement. In dysplastic hips, labral tears result from high shear stresses caused by the anterolateral migration of the femoral head from the deficient acetabular coverage24,27. Labral injuries can also occur as a result of acute hip trauma12,28. More recently, the concept of femoro-acetabular impingement has been proposed as a potential cause of labral damage in the nondysplastic hip14,21. With both cam-type and pincer-type femoro-acetabular impingement, motion-induced damage at the anterosuperior aspect of the acetabular rim21,29-32 is initiated at the junction between the labrum and the adjacent acetabular cartilage. Recently, Ito et al.11 reported that the tip of the labrum remains intact in most hips with femoro-acetabular impingement, even in the presence of osteoarthritis.
The acetabular labrum functions as a shock absorber and effects proper joint lubrication and pressure distribution34,35. Biomechanical studies performed by Ferguson et al.36-38 revealed that hydrostatic fluid pressurization within the joint space is greater in the presence of an intact labrum, which may enhance joint lubrication. Hydrostatic pressurization was impaired in hips without an acetabular labrum. Absence of this fluid seal resulted in higher joint loads on force transmission and poorer joint lubrication. Thus, the labrum acts like a seal that prevents fluid loss from the joint and protects articular cartilage35. In addition, Kim and Azuma34 investigated the innervations of the acetabular labrum that provide nociception and proprioception and concluded that the labrum functions as a “sensible shock absorber” of the hip. These biomechanical and physiologic functions of the labrum can be preserved to some extent if the labrum can be reattached and heals.
In this study, patients treated with labral refixation (Group 2) recovered earlier and had superior clinical and radiographic results when compared with patients who had had resection of the torn labrum (Group 1). Improvements in hip scores were mostly attributable to improvements in pain scores. The findings of our study are supported by the results reported by Ferguson et al.36. However, we must emphasize that our short-term results must be evaluated after a longer period of follow-up to better understand the ultimate effect of this new approach.
Weaknesses of this study include its retrospective nature and its lack of randomization. In addition, the Tönnis radiographic grading system14 and the Merle d'Aubigné clinical score lack sufficient sensitivity to assess subtle changes associated with early osteoarthritis secondary to femoro-acetabular impingement. Most patients with femoro-acetabular impingement experience intermittent pain, sometimes only during athletic activities, but have no substantial functional loss. As Groups 1 and 2 were sequential, not simultaneous, cohorts, some of the improvement in outcome in Group 2 could be attributed to improved surgical technique, which is inevitable with greater experience. However, because the groups were similar in terms of pathological findings, age, and sex, we believe that they were comparable.
Femoro-acetabular impingement may be an important factor in the pathogenesis of osteoarthritis of the hip, particularly in hips currently considered to have an “idiopathic” etiology2,5,16,39-41. In light of reports of encouraging results after the treatment of femoro-acetabular impingement2,16,40,42, these new data on the effect of labral refixation may be important as preservation of the intact portion of the labrum yielded better early results. On the basis of the results of this study, we consider refixation of an intact portion of the labrum to be superior to labral resection. Long-term follow-up will be necessary to assess whether use of this technique results in improved functional outcomes and a reduction in the prevalence of symptomatic osteoarthritis in affected patients.
Tables showing the Merle d'Aubigné score and the Tönnis osteoarthritis classification score and a figure depicting an intraoperative map are available with the electronic versions of this article, on our web site at jbjs.org (go to the article citation and click on “Supplementary Material”) and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM). ▪
A commentary is available with the electronic versions of this article, on our web site () and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM).
The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
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