O3273: Strength Recovery Patterns in Pediatric Patellofemoral Instability Following MPFL Reconstruction With and Without Tibial Tubercle Osteotomy

Background: Patellofemoral instability (PFI) is a prevalent condition in pediatric populations, often resulting in pain and functional limitations. Surgical stabilization is frequently required in cases of recurrent instability, most commonly medial patellofemoral ligament reconstruction (MPFLR) with or without tibial tubercle osteotomy (TTO). Strength restoration is a key component of functional recovery after surgical intervention and permits appropriate guidance regarding the return to activity. However, patterns of strength recovery remain poorly understood, particularly in pediatric patients with PFI. The objective of this study was to quantify isokinetic strength recovery following PFI surgery in pediatric patients treated with MPFLR with or without TTO.

Methods: This retrospective cohort study included pediatric patients who underwent MPFLR with or without TTO for PFI at a single tertiary care institution between 2011-2022 with available postoperative isokinetic strength testing. Isokinetic strength was measured using the Biodex dynamometer measured at 180 degrees/second, assessing extension peak torque limb symmetry index (LSI) and flexion peak torque LSI. Peak torque represents the maximal strength capacity measured by the maximum rotational force generated by a muscle group over a single repetition. Evaluations were performed at 3, 6, and 12 months, postoperatively. Descriptive and univariate analyses were conducted to summarize the cohort and assess predictors of strength recovery after adjustment with the Bonferroni correction.

Results: A total of 105 patients were included, with 70 undergoing MPFLR only and 35 undergoing MPFLR with concomitant TTO. The MPFL+TTO group had a higher proportion of females (74.3% vs. 51.4%, P=0.024), older age (15.7 vs. 15.3 years, P=0.038), and lower rates of sports participation (25.7% vs. 58.6%, P=0.005). In the MPFLR only group, significant improvements were observed in extension peak torque LSI (from 55.0 at 3 months to 78.7 at 12 months, P=0.003). However, no differences were found in the flexion peak torque LSI across timepoints (P=0.583). In the MPFL+TTO group, extension peak torque LSI improved from 52.0 at 3 months to 79.1 at 12 months (P=0.006). Flexion peak torque LSI also increased over the one-year period from 85.6 at 3 months to 92.9 at 12 months (P=0.015).

Conclusion: Isokinetic strength recovery following MPFLR with and without TTO demonstrated progressive improvements over time, with TTO patients demonstrating lower initial extensor function but achieving comparable metrics by one year postoperatively. Mean extension LSI metrics for both procedures were below the 90% threshold often used to guide return to sport following other knee procedures even at 1 year postoperatively. These findings provide a better understanding of postoperative isokinetic strength recovery in pediatric PFI patients and may serve to guide rehabilitation protocols and inform return-to-activity decision-making.