Arthroscopic medial retinacular repair after patellar dislocation with and without underlying trochlear dysplasia: a preliminary report.

PURPOSE: This study was undertaken to evaluate the influence of underlying trochlear dysplasia (TD) on clinical outcomes of arthroscopic medial retinacular repair.

METHODS

Between January 2000 and October 2004, a total of 91 patients underwent arthroscopic medial retinacular repair. Inclusion criteria for this study included an arthroscopic medial retinacular repair, a follow-up time of 12 months, and trochlear grading based on axial computed tomography (CT) scans (n = 48). TD, if present, was graded as types A through D, and patients were separated into group I (no or low-grade type A TD) and group II (types B through D TD). Redislocation was recorded, and Tegner, Lysholm, and International Knee Documentation Committee (IKDC) scores were determined.

RESULTS

No or grade A TD was detected in 26 knees (group I), and TD of grade B or C was found in 22 knees (group II). Type D TD was not observed. At a follow-up time of 12 months, 4 redislocations had been noted, all belonging to group II. Neither the Tegner nor the Lysholm score reached preinjury levels, but in a comparison with preoperative status, we could find a significant increase in all scores in both groups. Group I reached a significantly better postoperative outcome than was attained by group II.

CONCLUSIONS

Arthroscopic repair of the medial retinaculum is an effective technique by which patellofemoral instability can be addressed when normal or nearly normal trochlear geometry is present. In patients with underlying TD, patellofemoral stability cannot be completely restored, and clinical results are less successful. Precise preoperative radiologic determination of trochlear geometry may help the clinician to predict short-term outcomes in patients with patellofemoral instability.

LEVEL OF EVIDENCE: Level III, retrospective comparative therapeutic study.