Relatively Loose Flexion Gap Improves Patient-Reported Clinical Scores in Cruciate-Retaining Total Knee Arthroplasty

Although appropriate soft tissue balancing is well recognized as essential procedure in total knee arthroplasty (TKA), poor relationship between intraoperative soft tissue balance and physician-reported clinical outcomes was reported. Since physician-derived scores are reported to be poorly related to patient-reported scores, patient-derived outcome scales have received a great deal of attention and have become increasingly important. Thus, it should be clarified whether intraoperative soft tissue balance influences patient-reported clinical outcomes. Therefore, the purpose of this study was to investigate the relationship between intraoperative soft tissue balance and patient-reported clinical outcomes in TKA. A total of 35 TKAs were performed in patients with varus-type osteoarthritis, using the tibia first technique with a navigation system. Soft tissue balance (joint component gap and varus/valgus ligament balance) with femoral component placement and temporarily repaired patellofemoral joint were intraoperatively assessed with an offset-type tensor under 40 lb of joint distraction force. Measurements were performed at 0, 10, 30, 60, 90, and 120 degrees of knee flexion. Subjective clinical outcomes were assessed using the 2011 Knee Society score, which consists of objective knee indicators, patient satisfaction, patient expectations, and functional activities at the minimum 1-year follow-up. The relationship between each parameter in soft tissue balance and subjection clinical score was assessed using a simple linear regression model. Objective knee indicators, especially patient-reported symptoms, showed positive correlations with joint component gap difference of 90 to 0 and 120 to 0 degrees. Patient satisfaction and expectations also exhibited positive correlations with joint component gap difference of 90 to 0 and 120 to 0 degrees. There were no correlations among any parameters of soft tissue balance and functional activities. The other parameters, including varus/valgus ligament balance, showed no statistical correlations with clinical scores. In conclusion, intraoperative soft tissue balance influenced the postoperative clinical outcomes, where a relatively loose flexion gap resulted in higher scores for the parameters of pain, patient satisfaction, and patient expectations.