RESTORATION OF THE JOINT LINE IN COMPUTER NAVIGATED TOTAL KNEE ARTHROPLASTY

Abstract

Introduction: One of the four pillars of successful total knee arthroplasty (TKA) is restoration of the joint line. In conventional TKA the surgeon does not have a tool to control the accuracy of joint line restoration intraoperatively. The present study investigates if the preoperative joint line can be restored using an optical navigation system for TKA.

Materials and methods: Patients from two Orthopedic Centers (Istituto Orthopedico Rizzoli Bologna, 51 patients; Orthopädie Samedan, 42 patients) received computer assisted TKA (Stryker Scorpio) using the Stryker Knee navigation system. Using the software delivered with the navigation system depth of femoral and tibial medial and lateral osteotomies were recorded. After definite prosthesis implantation medial and lateral femoral condyle height as well as tibial length including polyethylene inlay were also recorded. Varus/valgus alignment was additionally recorded before and after prosthesis implantation.

Results: After femoral osteotomie varus/valgus alignment was 0 degrees (Stdv. 0.6 degrees). Lateral and medial osteotomies were performed with a depth of 8.2 and 8.8 mm respectively. Tibial osteotomie was performed with 0 degrees of varus/valgus (stdv. 0.7 degrees). Lateral and medial tibial osteotomies were performed with a depth of 7.5 and 4.8 mm respectively. After definite prosthesis implantation femoral and tibial varus/valgus alignment was 0.2 degrees of varus (stdv. 0.8 degrees) and 0.1 degrees of varus (stdv. 0.8 degrees) respectively. The femur was lengthened by 0.2 mm (stdy. 3 mm) medially and 1.1 mm (stdy. 3.1 mm) laterally. The tibia was shortened after component implantation by 1.5 mm (stdy. 3.4 mm) medially and 1.1 mm (stdv 3.1 mm) laterally.

Discussion: With the use of the Stryker Knee Navigation System, we can reconstruct the preoperative joint line with reproducible accuracy after a TKA. When prosthesis component and polyethylene inlay thickness are known, osteotomies may be performed and corrected intraoperatively to restore the joint line.