Postoperative Knee Extensor Strength After Medial Patellofemoral Ligament Reconstruction Using Superficial Slip of the Quadriceps Tendon and the Factors That Affect Strength Recovery.

BACKGROUND

Medial patellofemoral ligament reconstruction (MPFLR) using the quadriceps tendon can avoid complications related to the fixation of other graft types to the patella. However, there is concern about postoperative loss of knee extensor muscle strength because of harvesting a portion of the quadriceps tendon.

HYPOTHESIS

Knee extensor muscle strength after superficial slip of the quadriceps tendon MPFLR (SQ-MPFLR) decreases postoperatively, and there are specific factors that effect knee extensor muscle strength recovery.

STUDY DESIGN

Case series study; Level of evidence 4.

METHODS

A total of 26 patients who underwent unilateral primary SQ-MPFLR were enrolled. Clinical and functional outcomes were evaluated using the Kujala score and Tegner activity score preoperatively and 12 months postoperatively. Knee extensor muscle strength was examined preoperatively and 6 and 12 months postoperatively using the Biodex dynamometer. The knee muscle strength of the operated leg was compared with that of the contralateral leg using the limb symmetry index (LSI). The associations of sex, body mass index, and daily sports activity level with knee extensor muscle strengths at 6 and 12 months postoperatively were investigated and compared between the 2 groups.

RESULTS

The preoperative mean Kujala score was 65.0 and significantly improved to 94.7 at 12 months after surgery ( < .001). The preoperative Tegner activity score was 5.6, and the 12-month postoperative score was 5.8. The knee extensor LSI increased from 69.2% preoperatively to 82.0% at 12 months postoperatively. The patient group with a high sports activity level had a significant higher knee extensor muscle LSI (mean, 87.8%) than the group with a low sports activity level at 12 months postoperatively ( = .003).

CONCLUSION

The knee extensor LSI of patients who underwent SQ-MPFLR increased from 69.2% preoperatively to 82.0% postoperatively at 12 months. The patient group with a high sports activity level had a significantly higher knee extensor LSI than the group with a low sports activity level at 12 months after SQ-MPFLR surgery.