Treatment of chronic patellar dislocation with a modified Elmslie-Trillat procedure

Background: This paper describes a modification of the Elmslie-Trillat procedure that is usually performed in severe cases of habitual or recurrent patellar instability. Methods: Eighteen knees (7 men and 8 women) treated for recurrent or habitual patellar dislocation were evaluated clinically and radiographically at a mean follow-up of 5 years (range 24 months to 9 years). The mean age at follow-up was 26.3 years (range 17-44 years). The IKDC and Kujala and Tegner scores were used for the clinical evaluation. Anteroposterior, lateral and Merchant views were done for radiographic monitoring. When the patella was still unstable during dynamic evaluation after execution of the Elmslie-Trillat procedure, the medial third of the patellar tendon was isolated and harvested with a corresponding 1 cm long and 0.5 cm wide bone plug, maintaining its insertion to the inferior medial side of the patella. This ligament was medialized and put under tension, trying to find a medial insertion that guaranteed patellar stability throughout the full range of motion. Results: IKDC classified 11 knees as A (normal), 4 knees as B (almost normal), 2 knees as C (abnormal) and 1 knee as D (severely abnormal). The Kujala score showed excellent results in 16 knees, 1 fair and 1 poor knee. The mean Tegner score rose from 2 preoperatively to 5 at follow-up. The poor knee presented an over-correction of the congruence angle on radiography. On follow-up radiographs, the parameters were almost completely corrected. Statistical analysis showed a significant correction of radiograph parameters, and significantly worse results in patients who underwent trochleoplasty. Conclusion: The technique described tries to achieve a dynamic stability of the patella throughout the full range of motion in severe patellar instability where the Elmslie-Trillat procedure is insufficient. No recurrence of patellar instability has been observed. The stability must be obtained with dynamic control in the initial degrees of flexion, trying to avoid an excessive patellar medialization.