Tibiofemoral Kinematics following Successful Anterior Cruciate Ligament Reconstruction Using Dynamic Multiple Resonance Imaging

Background The aim of anterior cruciate ligament reconstruction is to reduce excess joint laxity, hoping to restore normal tibiofemoral kinematics and therefore improve joint stability. It remains unclear if successful ACL reconstruction restores normal tibiofemoral kinematics and whether it is this that is associated with a good result. Study Case series. Purpose To assess the kinematics of the anterior cruciate ligament-reconstructed knee using open-access MRI. Methods Tibiofemoral motion was assessed using open-access MRI, weightbearing through the arc of flexion from 0° to 90° in 10 patients with isolated reconstruction of the anterior cruciate ligament (hamstring autograft) in one knee and a normal contralateral knee. Midmedial and midlateral sagittal images were analyzed in all positions of flexion in both knees to assess the tibiofemoral relationship. Sagittal laxity was also assessed by performing the Lachman test while the knees were scanned dynamically using open-access MRI. Results The amount of excursion between the tibial and femoral joint surfaces was similar between the normal and reconstructed knees, but the relationship of tibia to femur was always different for each position of knee flexion assessed—the lateral tibia being about 5 mm more anterior in the anterior cruciate ligament-reconstructed knees. This anterior tibial position is statistically significantly different at 0° (P < .0006), 20° (P = .0004), 45° (P = .002), and 90° of flexion (P < .006). Anteroposterior laxity was similar between normal and anterior cruciate ligament-reconstructed knees. Conclusion Anterior cruciate ligament reconstruction reduces sagittal laxity to within normal limits but does not restore normal tibiofemoral kinematics despite a successful outcome.