Complete and Selective Resection of the Posterior Cruciate Ligament Reduces Contact Forces Asymmetrically in Cruciate-Retaining Total Knee Arthroplasty: A Computational Study.

Abstract

Assessing intraoperative ligament balance in the posterior cruciate ligament (PCL)-retaining total knee arthroplasty (TKA) can be achieved by quantifying tibio-femoral contact forces. Ligament balancing may involve selectively releasing PCL fibers; however, the effects of the extent and location of PCL release on compartmental contact forces are not well understood. To investigate these effects, we developed a computational model to quantify changes in medial and lateral contact forces resulting from targeted PCL fiber release. Computational models of 10 cadaver knees (five men and five women with a mean age of 63 years) were virtually implanted with a cruciate-retaining TKA. Passive knee flexion was simulated under three PCL conditions: all PCL fibers retained, all PCL fibers resected, and only the central PCL fibers released. Tibio-femoral contact forces in the medial and lateral compartments at 90° of flexion were measured for each PCL condition. Resecting the PCL resulted in a reduction of contact forces by a median of 24.2 N (P ≤ 0.01) medially and a median of 11.1 N (P ≤ 0.01) laterally. Selective release of only the central PCL fibers reduced medial and lateral contact forces by medians of 11.5 N (P ≤ 0.05) and 4.5 N (P ≤ 0.05), representing 47 and 50% of the reduction observed with complete PCL resection, respectively. Resecting the PCL asymmetrically impacts compartmental contact forces, with a greater reduction observed in the medial compartment. Given the contribution of the releasing PCL's central portion to the reduction in compartmental contact forces, surgeons may consider first focusing on this region when conducting intraoperative releases to achieve ligament balance via PCL resection in cruciate-retaining TKA.