Abstract
Background: Successful total knee arthroplasty requires component alignment according to the mechanical axes and restoration of ideal knee kinematics. This requires adequate ligament balancing, stable tibia-femoral and patello-femoral joints, and a non-restricted range of motion.
We developed a computer assisted total knee arthroplasty system to help the surgeon achieving more intra-operative accuracy.
Material and methods: An OPTOTRAK camera is used to track relative motions between femur, tibia, and instruments. In contrast to other systems we avoid fixation of reference bases onto acetabulum and foot. The surgeon generates a representation of the patient’s anatomy using the technique of “surgeon defined anatomy”. Based on recorded landmarks the system calculates the femoral and tibial mechanical axes, the position of the knee joint line, the level of the defects on femoral and tibial side, the anatomically best fitting femoral component size, the femoral ventral level, and the natural tibial rotation. These values enable an initial planning situation, which features alignment of the tibial and femoral distal resection planes according to the mechanical axes as well as the definition of the anterior and posterior femoral resection planes with respect to the ventral cortex and the prosthesis design. To consider soft-tissue behaviour the surgeon loads both collateral ligaments in extension and flexion, a
Results: During a clinical study we performed thirteen total knee arthroplasties. Postoperatively passive extension was 0.8-4.2° (mean 1.9°) in the coronal plane and 0.2-3.9° (mean 1.8°) in the sagittal plane. Varus-valgus instability was 7.2°. The results of the subsequent patients of this ongoing study will be available during the conference.
The abstracts were prepared by Nico Verdonschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, University Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
