Summary

This study reports a surgical failure rate for patellofemoral stabilization of 4.8%, with the sole risk factor statistically associated with graft failure being generalized ligamentous laxity.

Abstract

Background

Recurrent patellofemoral instability is a common knee problem for which medial patellofemoral ligament (MPFL) reconstruction with or without concomitant procedures has been shown to effectively and consistently improve function and quality of life outcomes. Management of patellofemoral instability is difficult due to the varying combinations of demographic and pathoanatomic risk factors that present and the controversy regarding the thresholds used to determine the need for concomitant procedures. Examination of surgical failures in this complex patient population is necessary to guide surgical management and develop an understanding of the interplay of these anatomic and biomechanical risk factors.

Purpose

The purpose of this study was to report and analyze the surgical failure rates for patellofemoral stabilization in a large patient cohort. The secondary purpose was to compare the presence of risky demographic and pathoanatomic risk factors in the surgical failures compared with successful stabilizations. Finally, cases of re-dislocation were analyzed to identify the most probable cause for failure.

Methods

This is a prospective case series of 590 knees with symptomatic recurrent patellofemoral instability that underwent a surgical patellofemoral stabilization between June 2008 and February 2017. All patients received an MPFL reconstruction with concomitant procedures performed when indicated to address significant pathoanatomic risk factors. Surgical failure was defined as re-dislocation of the patella. Patients with a successful stabilization procedure were compared to those with a surgical failure using Chi-squared or t-tests for demographic and pathoanatomic variables. The surgical failures were analyzed to determine the probable cause of failure.

Results

A total of 590 patellar stabilization procedures with a minimum follow-up of 24 months (range 24-137) were assessed. There were 28 re-dislocations of the patella for a surgical failure rate of 4.8%. The only risk factor associated with failure was generalized joint hypermobility (Beighton score >5 (2.8) compared to <4 (2.9); p<0.01). The probable causes of failure were generalized joint hypermobility and trochlear dysplasia. The most common revision procedures were isolated MPFL reconstruction revision, MPFL reconstruction revision with tibial tubercle osteotomy, and MPFL reconstruction revision with trochleoplasty.

Conclusions

This study reports a surgical failure rate for patellofemoral stabilization of 4.8% in a large single surgeon cohort. The only risk factor statistically associated with graft failure was generalized joint hypermobility. Overall, patellofemoral stabilization procedures provide good clinical results with very low failure rates. This information may be used to guide surgical decision-making and patient education in this complex patient population.