ACCURACY AND BENEFIT FROM MINIMAL INVASIVE COMPUTER-ASSISTED TOTAL KNEE ARTHROPLASTY

Abstract

Introduction: Computer-assisted minimal invasive total knee arthroplasty (MIS-TKA) provides the patient with the advantages of computer navigated total knee arthroplasty (CN-TKA) and early mobilization and progressive rehabilitation because of minor soft tissue injury. Since conventional landmarks are not visible for the surgeon throughout the operation, he must rely on the data displayed by the computer navigation system. This study was designed to assure that MIS-TKA reveals identical mechanical accuracy as conventional computer navigated TKA while reducing rehabilitation time.

Materials and methods: The Stryker knee navigation system was used intraoperatively. There were forty patients included in this study: 20 consecutive patients received computer navigated TKA (Scorpio) and 20 consecutive patients received MIS-TKA (Stryker-MIS Scorpio). Preoperatively and 6 months after the operation all patients received orthoradiograms and a CT-scan of the knee to determine mechanical and rotational alignment. Intraoperatively data shown by the navigation system was recorded. The HSS knee score was recorded preoperatively and 6 months postoperatively. Length of skin incision, length of hospital stay and postoperative range of motion were also determined.

Results: Analysis showed that the mechanical axis improved in both groups to less than 1° of varus. Rotational alignment of the femoral component showed reproducible values of less than 2° of rotation without significant differences between the two groups. Also, ligament laxity was almost identical preoperatively and postoperatively in 0°, 45° and 90° of knee flexion. Length of skin incision was significantly shorter in MIS-TKA. HSS knee score improved from a mean of 76 points (range 57–96) preoperatively to a mean of 92 points (range 64–100) 6 months postoperatively for both groups. Patients from the MIS-TKA group revealed a quicker recovery time than patients from the CN-TKA group. ROM improved sooner after the operation in the MIS-TKA group, however after 6 months both systems reached the same ROM. The length of hospital stay was significantly reduced by the MIS-TKA group.

Discussion: The Stryker knee navigation system aids the surgeon to precisely optimize mechanical and rotational alignment and to avoid malrotation and axial malalignment not only in CN-TKA but also in MIS-TKA. We have found no significant differences in preoperative and postoperative ligament laxity between the two groups. The advantages of minimal soft tissue damage in MIS-TKA can be achieved without loss of accuracy and with a great benefit for the patient.