Purpose. To compare postoperative clinical outcomes between posterior cruciate ligament (PCL) retaining and resecting total knee arthroplasty (TKA) using same cruciate-substituting (CS) inserts, and to elucidate the clinical relevance of the residual PCL in cruciate-retaining TKA, considering intraoperative influence factors, such as the posterior tibial slope, posterior condylar offset, joint gap, joint balance, and joint laxity. Methods. A total of 64 consecutive knees (44 patients) were enrolled in this study and divided into following two groups: 39 knees underwent PCL-retaining TKA group (CR group), and 25 underwent PCL-resecting TKA group (CS group). Preoperative patients’ demographic data and one-year postoperative clinical outcomes including range of motion, the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Japanese Orthopaedic Association (JOA) score, and Forgotten Joint Score-12 (FJS-12) were compared between two groups. Results. Regarding range of motion, the average preoperative ROM was -14.3/120.0 degrees in the CR group and improved to -2.4/118.9 degrees postoperatively. In the CS group, the average preoperative ROM was -7.5/130 degrees and changed to -2.2/122.4 degrees postoperatively. There was no significant difference in the postoperative ROM between the groups (P=0.16). The KOOS (from 47.1 to 69.5 in CR group; from 41.1 to 70.8 in CS group) and JOA scores (from 59.2 to 76.9 in CR group; from 55.6 to 80.8 in CS group) were significantly improved postoperatively in both groups (P < 0.01). However, there was no significance in these postoperative scores between two groups (P = 0.09). There was also no significance in FJS-12 between two groups (70.3 in CR group and 66.9 in CS group; P=0.53). Conclusions. Residual PCL in TKA with a CS insert would not impact one-year postoperative clinical outcomes including KOOS, JOA, and FJS-12

Achieving deep flexion after total knee replacement remains a challenge. In this study we compared the soft-tissue tension and tibiofemoral force in a mobile-bearing posterior cruciate ligament-sacrificing total knee replacement, using equal flexion and extension gaps, and with the gaps increased by 2 mm each. The tests were conducted during passive movement in five cadaver knees, and measurements of strain were made simultaneously in the collateral ligaments. The tibiofemoral force was measured using a customised mini-force plate in the tibial tray. Measurements of collateral ligament strain were not very sensitive to changes in the gap ratio, but tibiofemoral force measurements were. Tibiofemoral force was decreased by a mean of 40% (sd 10.7) after 90° of knee flexion when the flexion gap was increased by 2 mm. Increasing the extension gap by 2 mm affected the force only in full extension. Because increasing the range of flexion after total knee replacement beyond 110° is a widely-held goal, small increases in the flexion gap warrant further investigation.