Vastus medialis onset activation in patients who underwent medial patellofemoral ligament reconstruction with and without tibial tubercular osteotomy.

BACKGROUND

Medial patellofemoral ligament reconstruction (MPFLR) and tibial tubercular osteotomy (TTO) are common surgical treatments for patellar dislocation. However, the impact of isolated MPFLR and MPFLR combined with TTO (MPFLR+TTO) on vastus medialis oblique (VMO) onset activation remains unclear. This study investigated the VMO onset activation relative to the vastus lateralis (VL) among patients undergoing isolated MPFLR, MPFLR+TTO, and healthy controls during maximum voluntary isometric knee extension.

METHODS

This study included 25 patients who underwent MPFLR, divided into two groups: isolated MPFLR (n = 12, age: 22.6 ± 11.9, follow-up time: 24.0 ± 16.8 months) and MPFLR+TTO (n = 15, age: 28.2 ± 12.8, follow-up time: 25.2 ± 15.6 months). A control group of 11 healthy adults (22 knees, age: 28.4 ± 1.3) was also included. Electromyographic (EMG) activities of the VMO and VL muscles were recorded during maximal voluntary isometric knee extensions at 30°, 60°, and 90° of flexion. Differences in VMO onset activation relative to VL (VMO-VL) were analyzed.

RESULTS

At 30° knee flexion, the MPFLR group showed a significant delay in VMO activation compared to healthy controls (p < 0.001). In contrast, the MPFLR+TTO group exhibited no significant differences in VMO activation relative to healthy controls. No significant differences were observed at 60° and 90° flexion among all groups.

CONCLUSION

Isolated MPFLR delayed VMO activation relative to VL. In contrast, MPFLR+TTO balanced the onset activation between VMO and VL. These findings highlight the need for targeted rehabilitation programs to address delayed VMO activation in patients undergoing isolated MPFLR.