Effect of tibial cut angle in gap balanced LCS total knee replacement on postoperative knee funcion: A retrospective comparison study

Abstract

Background: Although total knee arthroplasty (TKA) is one of the most successful operations in orthopaedic surgery, still approximately 20% of these patients have chronic unexplained pain which affect their life’s quality and post-operative expectations. The New Jersey low contact stress (LCS) knee system (LCS; DePuy Orthopaedics Inc., Warsaw, IN, USA) is one of the most effective knee designs with a well-known long track record. The surgical technique used is a gap balance technique which references the femoral component rotation to a well-designed tibial cut while maintaining soft tissue balance via appropriate tensioning of collateral ligaments. Aim of this study is to look at any relationship between tibial cut coronal orientation on x-rays and patients satisfaction in relation to pain and function using the validated Oxford Knee Score (OKS). Hypothesis: A varus tibial cut >3? in LCS TKA can result in femoral component internal rotation, patellar maltracking and chronic knee pain with suboptimal functional results. Methods: A single surgeon’s TKA cohort using the LCS system was retrospectively evaluated from March 2017 to March 2020. We identified two cohorts of patients, one with a tibial cut angle on x-rays 3? (41 TKAs). They received LCS TKA for right or left knee symptomatic end stage arthritis. We measured the tibial cut angle on antero-posterior (AP) x-rays and we obtained updated OKS by discussion over telephone (due to COVID-19 restrictions) with patients. We analysed our data for the two patient cohorts to look for any statistically significant functional difference. Results: 100 patients coronal x-rays were finally included in the study. 59 patients were identified to have tibial cut angle 3?. The average age of the patients was 69.45(53-81 years), average time since surgery 19.4 months (7-41months), and average OKS of 45.88. There was statistically significant difference in OKSs with females scoring less than males, with the former avera