Summary

Pediatric patients who underwent a medial patellofemoral ligament reconstruction (MPFLR) for treatment of patellar instability have thicker lateral patellar retinacula (LPR) and greater patellar tilt compared to a control cohort.

Abstract

Introduction

Pediatric and adolescent patients who undergo a medial patellofemoral ligament (MPFL) reconstruction for surgical treatment of patellar instability often undergo a concomitant release of the lateral patellar retinaculum (LPR). Releasing the LPR improves patella alignment and positioning in the trochlear groove. As patellar tilt is also a commonly used radiograph measure of assessing patellar instability, we were interested in assessing the relationship between patellar tilt and LPR thickness. Few prior studies have described the exact indications for LPR release. The purpose of this study was to examine the thickness of the LPR and patellar tilt in pediatric and adolescent patients who undergo an MPFL reconstruction. We hypothesize that patients undergoing MPFL reconstruction will have a thicker LPR and increased patellar tilt when compared to a comparison cohort.

Methods

Preoperative magnetic resonance imaging (MRI) of patients ≤18 years old who underwent an MPFL reconstruction between 2016 and 2022 were retrospectively reviewed. Patients were included if they had a proton density preoperative axial MRI performed internally at our institution and excluded if they had a history of previous ipsilateral knee surgery or were syndromic and/or obligatory dislocators. Included patients were matched to a comparison cohort based on age within 1.5 years at time of imaging, sex, and laterality. LPR thickness and patellar tilt were measured on an axial proton density preoperative MRI. Demographic and surgical data was collected for all included MPFL reconstruction patients. An Independent Samples Mann-Whitney U Test was performed to compare LPR thickness and patellar tilt between the MPFL cohort and the comparison cohort.

Results

A total of 363 patients were identified. 145 participants were successfully matched to the comparison cohort. The mean age of the 145 participants in the MPFL cohort was 14.4 ± 2.1 years and 68% were female. The LPR thickness in the MPFL cohort was significantly greater than the LPR thickness in the comparison cohort (2.2 ± 0.8 mm vs. 1.9 ± 0.6 mm, p<0.001). The patellar tilt was significantly greater in the MPFL cohort compared to the control cohort (17.8 ± 8.5 degrees vs. 7.2 ± 5.2 degrees, p<0.001). There was no statistically significant difference in the occurrence of a lateral release/lengthening procedure in patients who underwent MPFL compared with those who did not.

Conclusion

This study demonstrated that the LPR was significantly thicker on preoperative MRI in patients undergoing MPFL reconstruction compared to a comparison cohort, indicating that increased LPR thickness is a radiographic association for patients with patellofemoral instability. Patellar tilt is also directly correlated with increased LPR thickness.