2016 年 35 巻 4 号 p. 445-450
Objective: The Triathlon® cruciate-substituting (CS) insert has a 2.54 mm anterior elevated lip and the same posterior geometry as the cruciate-retaining (CR) insert. Manufacturers claim that the insert can provide excellent posterior stabilization without decreasing rotational freedom and can be used with either posterior cruciate ligament (PCL) retention or sacrifice. The purpose of this study was to evaluate range of motion (ROM) and anteroposterior stability in the CS insert in comparison with those in the CR insert for the same total knee arthroplasty (TKA) with PCL sacrifice.
Methods: Intraoperative measurements were performed using the Stryker knee navigation system® in 15 osteoarthritic knees in 15 patients (2 male and 13 female; mean age, 74 years). Operation was performed under general anesthesia by using the navigation system. The PCL was sacrificed in all knees. After implantation of all the components, either a CR or CS trial insert was inserted. Following this, ROM was measured using gravity after transient capsular suture. Next, the anterior and posterior displacements between the centers of the femoral and tibial components were measured in manual stress testing at 90° of flexion. The posterior displacement was also measured by applying 5 kg of weight at the proximal tibia.
Results: The ROM was similar between the CR and CS inserts. During manual stress testing, maximal posterior displacement was significantly smaller with the CS insert than with the CR insert (10.6±2.5 mm vs. 11.3±2.8 mm, P=0.0104). The maximal anteroposterior displacement was significantly smaller with the CS insert than with the CR insert (13.1±4.4 mm vs. 15.9±5.0 mm, P=0.0002). The maximal posterior displacement with the weight was also significantly smaller with the CS insert than with the CR insert. However, the average difference was 1.0 mm.
Conclusion: Our results show that intraoperative ROM was similar between the CR and CS inserts in TKA with PCL sacrifice. The anteroposterior stability at 90° of flexion was significantly greater with the CS insert than with the CR insert. However, posterior stabilization was poor with the CS insert. We do not recommend use of the CS insert in TKA with PCL sacrifice.
