INTRODUCTION
Postoperative range of motion (ROM) is one of the most important factors influencing patient satisfaction after total knee arthroplasty (TKA). Patients planning to undergo TKA, especially in non-western cultures, usually expect that he or she will be able to sit cross-legged or kneel with ease after the operation; however, these activities require deep knee flexion.1 Predicting postoperative ROM is complicated, as the results can be affected by multiple factors such as the patient's age, gender, diagnosis, preoperative ROM, the surgeon's skill, the design of the prosthesis, postoperative rehabilitation, etc.2-4 While most of these factors are not easily modifiable, the selection of the prosthesis is mostly dependent upon the surgeon's discretion. Accordingly, there have been many attempts to improve postoperative ROM by modifying the prosthetic design. The high-flexion total knee system is one among the more recently introduced prostheses. Therein, thickened and round posterior femoral condyles of the prosthesis are able to increase the articular contact area and prevent posterior impingement of the femur at a high flexion angle. Consequently, increased ROM and diminished contact stress were expected. Both cruciate-retaining (CR) and posterior-stabilized (PS) type TKAs are available with the high-flexion type total knee system. A few comparison studies on the CR-Flex and PS-Flex type TKAs regarding postoperative outcomes or in vivo kinematics have been reported. Sharma, et al.5 and Seon, et al.6 reported in their in vivo kinematic studies, that the PS-Flex type TKAs showed weight-bearing knee flexion and posterior femoral roll-back, while Cates, et al.7 reported no difference in weight-bearing knee flexion, but rather more consistent axial rotation in the CR-Flex type TKAs. Kim, et al.,8 on the other hand, reported, in a study of bilateral simultaneous TKAs of CR-Flex type TKA on one side and PS-Flex type TKA on the other side, that no difference in knee flexion and functional outcomes between the two groups after 2-year postoperative follow-up. However, there is no general consensus regarding the postoperative range of motion or the functional outcomes between the CR- and PS-type high-flexion TKAs as of now. Therefore, the purpose of this study was to compare the postoperative ROMs and functional outcomes in patients who underwent TKA utilizing either the CR- or PS-type high-flexion total knee system. We hypothesized that the postoperative ROM would be slightly better in the PS-Flex type TKAs and that the postoperative functional outcomes would be similar between the two groups.
แนะนำPostoperative range of motion (ROM) is one of the most important factors influencing patient satisfaction after total knee arthroplasty (TKA). Patients planning to undergo TKA, especially in non-western cultures, usually expect that he or she will be able to sit cross-legged or kneel with ease after the operation; however, these activities require deep knee flexion.1 Predicting postoperative ROM is complicated, as the results can be affected by multiple factors such as the patient's age, gender, diagnosis, preoperative ROM, the surgeon's skill, the design of the prosthesis, postoperative rehabilitation, etc.2-4 While most of these factors are not easily modifiable, the selection of the prosthesis is mostly dependent upon the surgeon's discretion. Accordingly, there have been many attempts to improve postoperative ROM by modifying the prosthetic design. The high-flexion total knee system is one among the more recently introduced prostheses. Therein, thickened and round posterior femoral condyles of the prosthesis are able to increase the articular contact area and prevent posterior impingement of the femur at a high flexion angle. Consequently, increased ROM and diminished contact stress were expected. Both cruciate-retaining (CR) and posterior-stabilized (PS) type TKAs are available with the high-flexion type total knee system. A few comparison studies on the CR-Flex and PS-Flex type TKAs regarding postoperative outcomes or in vivo kinematics have been reported. Sharma, et al.5 and Seon, et al.6 reported in their in vivo kinematic studies, that the PS-Flex type TKAs showed weight-bearing knee flexion and posterior femoral roll-back, while Cates, et al.7 reported no difference in weight-bearing knee flexion, but rather more consistent axial rotation in the CR-Flex type TKAs. Kim, et al.,8 on the other hand, reported, in a study of bilateral simultaneous TKAs of CR-Flex type TKA on one side and PS-Flex type TKA on the other side, that no difference in knee flexion and functional outcomes between the two groups after 2-year postoperative follow-up. However, there is no general consensus regarding the postoperative range of motion or the functional outcomes between the CR- and PS-type high-flexion TKAs as of now. Therefore, the purpose of this study was to compare the postoperative ROMs and functional outcomes in patients who underwent TKA utilizing either the CR- or PS-type high-flexion total knee system. We hypothesized that the postoperative ROM would be slightly better in the PS-Flex type TKAs and that the postoperative functional outcomes would be similar between the two groups.
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