University of Bologna, Bologna, Italy.
II Orthopaedic and Traumatologic Clinic, IRCCS Istituto Ortopedico Rizzoli, Lab. di Biomeccanica via di Barbiano 1/10, 40136, Bologna, Italy.
Knee Surg Sports Traumatol Arthrosc. 2019 Apr;27(4):1049-1056. doi: 10.1007/s00167-018-5243-5. Epub 2018 Oct 27.
To assess, using model-based dynamic radiostereometric analysis (RSA), the biomechanical behaviour of a new design posterior-stabilized (PS) fixed-bearing (FB) total knee arthroplasty (TKA) in vivo while patients performing two common motor tasks. The hypothesis was that model-based dynamic RSA is able to detect different behaviour of the implant under weight-bearing and non-weight-bearing conditions.
A cohort of 15 non-consecutive patients was evaluated by dynamic RSA 9 months after TKA implantation. The mean age of patients was 73.4 (65-72) years. The kinematic evaluations were performed using an RSA device (BI-STAND DRX 2) developed in our Institute. The patients were asked to perform two active motor tasks: sit-to-stand in weight-bearing condition; range of motion (ROM) while sitting on the chair. The motion parameters were evaluated using the Grood and Suntay decomposition and the low-point kinematics methods.
The dynamic RSA evaluation showed a significant difference (p < 0.05) between the biomechanical behaviour of the prosthesis during the two motor tasks. When subjected to the patient weight (in the sit-to-stand) the low point of the medial compartment had a shorter motion (5.7 ± 0.2 mm) than the lateral (11.0 ± 0.2 mm). This realizes a medial pivot motion as in the normal knee. In the ROM task, where the patient had no weight on the prosthesis, this difference was not present: the medial compartment had a displacement of 12.7 ± 0.2 mm, while the lateral had 17.3 ± 0.2 mm.
Model-based RSA proved to be an effective tool for the evaluation of TKA biomechanics. In particular, it was able to determine that the fixed-bearing posterior-stabilized TKA design evaluated in this study showed a medial pivoting movement under weight-bearing conditions that was not present when load was not applied. Under loading conditions what drives the pattern of movement is the prosthetic design itself. By the systematic use of this study protocol future comparisons among different implants could be performed, thus contributing significantly to the improvement of TKA design.
IV.
使用基于模型的动态放射立体测量分析（RSA）评估一种新型后稳定（PS）固定轴承（FB）全膝关节置换（TKA）的生物力学行为，同时患者执行两项常见的运动任务。假设是基于模型的动态 RSA 能够检测到在负重和非负重条件下植入物的不同行为。
对 15 名非连续患者进行了队列评估，他们在 TKA 植入后 9 个月接受了动态 RSA 检查。患者的平均年龄为 73.4（65-72）岁。运动评估使用我们研究所开发的 RSA 设备（BI-STAND DRX 2）进行。要求患者执行两项主动运动任务：负重坐下站起；坐在椅子上时的运动范围（ROM）。使用 Grood 和 Suntay 分解和低点运动学方法评估运动参数。
动态 RSA 评估显示，在两项运动任务中，假体的生物力学行为存在显著差异（p<0.05）。当承受患者体重（坐下站起时）时，内侧间室的低点运动距离较短（5.7±0.2 毫米），而外侧间室为 11.0±0.2 毫米。这实现了类似于正常膝关节的内侧枢轴运动。在 ROM 任务中，患者在假体上没有重量，这种差异不存在：内侧间室的位移为 12.7±0.2 毫米，而外侧间室为 17.3±0.2 毫米。
基于模型的 RSA 被证明是评估 TKA 生物力学的有效工具。特别是，它能够确定在这项研究中评估的固定轴承后稳定 TKA 设计在负重条件下表现出内侧枢轴运动，而在没有施加负载时则不存在。在加载条件下，驱动运动模式的是假体设计本身。通过系统使用本研究方案，未来可以对不同植入物进行比较，从而显著促进 TKA 设计的改进。
IV。
