Purpose: Quadriceps strength and activation may play an important role in the recovery from ACL revision surgery. The purpose of this study was to describe quadriceps strength and central activation ratio (CAR) and correlate with radiographic findings in patients with ACL revision surgery.
Methods: Twenty-one patients who were on average 47.5 ± 21.1 months [range: 14-85 months] post-revision ACL reconstruction. We performed knee joint physical examination and radiographic evaluation. Quadriceps strength testing consisted of maximal voluntary isometric contractions (MVIC) with the knee bent to 90-degrees bilaterally. We calculated quadriceps central activation ratio using the superimposed burst technique. Radiographs (bilateral standing antero-posterior in knee flexion and lateral in full extension) were evaluated by a fellowship-trained orthopedic surgeon using the International Knee Documentation Committee (IKDC) grading system.
Results: Mean CAR was 83.9 ± 12.0% on the reconstructed limb and 85.5 ± 9.5% on the contralateral limb. Average, normalized MVIC torque was 2.5 ± 1.0 Nm/kg on the reconstructed limb and 2.7 ± 1.0 N m/kg for the contralateral limb. Patient age at the time of follow-up evaluation was related to severity of knee joint degeneration, particularly the medial, anterior and patellofemoral compartments. Younger patients with lower CARs tended to have more severe degeneration in the patellofemoral joint. Older patients with lower normalized MVIC torque values tended to exhibit more severely graded degeneration in the patellofemoral joint.
Conclusion: Bilateral quadriceps central activation deficits and radiographic osteoarthritis are evident in patients with revision ACL reconstruction.