Comparison of Radiologic Measurements of Total Knee Replacement using Computer-assisted Navigation System and Conventional System in Varus Deformity of the Knee / 대한정형외과학회잡지

ABSTRACT

PURPOSE: To compare the radiologic measurements of the mechanical axis and the implant position of Total Knee Arthroplasty (TKA) using a computer-assisted navigation system with those using conventional TKA in varus deformity. MATERIALS AND METHODS: From January 2004 to January 2005, 49 TKAs using a CT-free navigation system (Vector Vision(R), BrainLab, Heirnstetten, Germany) (Group I) and 24 TKAs using the conventional technique (Group II) were performed on patients who had a preoperative varus deformity>10degrees. The patients were also subdivided into two groups, patients with a varus deformity 20degrees (group B). The PFC Sigma implants were used in both groups. The mechanical axis and implant position were measured by 2 observers according to the reontgenographic evaluation system of the American Knee Society. RESULTS: There was no significant difference in alpha, beta, delta angle and mechanical axis between group I and II. There was a significant difference in the gamma angle between group I and II (p20degrees tended to have more postoperative varus mechanical alignment than those with a preoperative varus deformity between 10degrees and 20degrees after TKA. More careful attention during the registration of the femoral mechanical axis should be paid in patients with a larger varus deformity in TKA using a computer-assisted navigation system. On the other hand, a reasonable mechanical valgus angle should be considered in femoral bone cutting for a varus deformity of the distal femur in conventional TKA. In addition, inadequate positioning of intramedullary rod should be recognized in conventional TKA.