Increased Prevalence of Posterior Cruciate Ligament Dysfunction Noted With 3-Dimensional Intraoperative Kinematic Evaluation in Total Knee Arthroplasty

Background: Poor restoration of cruciate-driven kinematics after total knee arthroplasty may result from technical difficulties, but the ligament may also be functionally compromised by the presence of arthritis. We asked whether the function of the posterior cruciate ligament (PCL) could be assessed intraoperatively to predict the quality of the resulting posterior cruciate kinematics.

Methods: PCL integrity was assessed using intraoperative infrared trackers to monitor knee kinematics in 73 patients. Three-dimensional images of the femur and tibia were projected onto a screen, allowing the surgeon to visualize kinematic relationships in real time. We measured femoral rollback (distance of femoral contact as a percentage of antero-posterior tray width) from images captured by the robotic system during initial kinematic assessment, gap balancing, and assessment of the final construct and from lateral flexion radiographs obtained 2 years after surgery. Associations were characterized using Pearson's correlation and graphical methods.

Results: Thirty-six knees (49%) showed rollback <60% during gap balancing, indicative of PCL insufficiency. The rollback during gap balancing was positively correlated with that seen in the final cruciate retaining constructs (r = 0.60, P < .001), which in turn predicted rollback 2 years after surgery on lateral flexion X-rays (r = 0.50, P = .006).

Conclusion: Intraoperative functional evaluations can allow the surgeon to identify cases where rollback is not consistent with desirable knee kinematics, and posterior stabilization may lead to a better outcome for those patients.