The Change of the Posterior Tibial Slope after Cruciate Retaining Total Knee Arthroplasty

Abstract

Purpose: To analyze the preand postoperative posterior tibial slope angle (PSA) of performing cruciate-retaining total knee arthroplasty (TKA) and to identify the ideal value of the PSA in relation to the clinical results. Materials and Methods: From June 1999 to May 2005, 202 TKA with a NexGenR cruciate-retaining knee were performed in 160 patients. The mean follow-up period was 39.8 months. The preand postoperative PSA referenced by the proximal tibial medullary canal (PSA-A) and the proximal tibial anterior cortex (PSA-B) were measured by two independent observers. The knee and function scoring system of the American Knee Society and the range of motion of the knee at the last follow-up were evaluated as the clinical results. Results: The mean PSA-A was 11.4±4.8 preoperatively and 6.0±2.8 postoperatively, and the mean PSA-B was 13.6±4.9 preoperatively and 8.1±2.9 postoperatively. The difference between the preand postoperative PSA increased as the preoperative PSA-A changed from 6.0 and the PSA-B changed from 8.1; these findings showed statistical significance based on a simple linear regression (PSA-A: r= 0.837, p=0.000; PSA-B: r=0.834, p=0.000). The knee and function score of American Knee Society improved respectively from 62.9 and 55.8, preoperatively, to 97.4 and 89.7 respectively, at the last follow-up. The range of motion of the knee joint was 128.0 preoperatively and 129.7 at the last follow-up. Conclusion: In cruciate retaining total knee arthroplasty, PSA-A is mostly distributed within 3.2-8.8, and a reasonable range of PSA-A is 6.0±2.8.