Assessing changes in wrist biomechanics during ageing and optimal design of total wrist arthroplasty and assistive rehabilitation devices

手腕是一个高度复杂的解剖关节，由桡骨、腕骨和掌骨的相对运动组成。手腕关节炎和损伤可以通过关节融合术(融合术)进行手术治疗，这种手术可以缓解疼痛，但限制或消除关节的运动。因此，为了维持患者的关节功能，越来越多的人尝试进行保留运动的手术，如全腕关节置换术(TWA)。Motec手腕是一种球套式TWA假体，它取代了手腕上的所有解剖关节。虽然对MOTEC患者的随访研究是积极的，但对术后活动范围(ROM)和疗效的详细评估仍有待进行。尤其是那些研究周转和功能上重要的飞镖投掷者运动(DTM)的人。因此，本项目有以下目标。首先比较TWA手术前后腕关节的功能活动度和运动效率。第二，研究Motec旋转中心(COR)在腕关节间隙内的最佳位置。第三，比较手术前后横过关节的肌肉手臂的瞬间。由于侵入性的外科和实验技术，我们采取了身体入路。设计了一种主动手腕运动模拟器，通过驱动5个主动肌腱来移动身体手腕。通过施加相同的肌腱位移来实现不同手术条件之间的控制，并记录肌腱力作为运动效率的衡量标准。在对模拟器的评估中，使用了双平面X射线视频摄影(BPVR)和X射线运动形态重建(XROMM)来测量Motec手术前后6个身体腕关节的整体运动。在这两种情况下，都成功地模拟了屈伸、尺偏、DTM和外旋。此外，模拟的腕角和肌腱力在单个样本内是可重复的，但在不同样本之间不能重复。评估表明，模拟的手腕运动可以在不同的手术条件下进行比较，以确定手术的潜在机械效应。使用身体模拟器进行了两组实验，在此期间，记录了七种运动模式下的腕角和肌腱力。第一组研究TWA前和TWA后的手腕(n=14)。第二组研究了Motec腕关节，包括6个不同的COR位置和TWA前的状态(n=6)。这两组实验都测量肌腱力量作为腕部运动效率的指标，使用BPVR捕捉模拟运动，并使用XROMM动画测量手腕角度。在该项目的最后阶段，将创建生物力学腕关节模型，以估计解剖腕和Motec腕的肌力矩臂。虽然这项工作尚未完成，但TWA手术前后的比较显示，在屈曲、伸展和放射尺偏斜的范围，或在外展区域，没有明显的差异。重要的是，Motec手腕能够产生DTM。在屈曲时，Motec腕关节屈肌腱的最大力显著降低，其他方面与TWA前的情况并无差异。除了术后尺侧腕伸肌力在伸展过程中有所下降外，最大伸肌腱张力没有显著差异。在第二组实验中收集的数据尚未完全处理。我们的目标是确定是否存在一个Motec核心位置，在该位置上可以实现最优的ROM值和运动效率。Motec核心的位置也将与解剖腕核心的最佳位置进行比较。到目前为止的结果表明，Motec Twas具有以与手术前相似的效率重建功能性腕部运动的潜力。需要进一步的研究来确定这些结论是否在体内得到支持。

The wrist is a highly complex anatomical joint comprising relative motion of the radius, carpals and metacarpals. Wrist arthritis and injury can be treated surgically with arthrodesis (fusion), which relieves pain but restricts or eliminates motion at the joint. Therefore, motion preserving procedures, e.g. total wrist arthroplasty (TWA), are increasingly being attempted to maintain patients' joint function. The Motec wrist is a ball and socket style TWA prosthesis which replaces all anatomical articulations at the wrist. While follow-up studies of Motec patients have been positive, detailed assessments of post-operative range of motion (ROM) and efficiency are yet to be performed. Particularly those investigating circumduction and the functionally important Dart Thrower's Motion (DTM). Hence, this project has the following objectives. First to compare functional ROM and efficiency of motion in pre- and post- TWA wrists. Second to investigate optimal placement of the Motec centre of rotation (COR) within the wrist joint space. Third to compare pre- and post- operative moment arms of muscles crossing the joint.Due to invasive surgical and experimental techniques, a cadaveric approach was taken. An active wrist motion simulator was designed to move cadaveric wrists by actuating five agonist tendons. Control between different surgical conditions was achieved by applying identical tendon displacements, and tendon forces were recorded as a measure of motion efficiency. In an evaluation of the simulator, biplanar X-ray videoradiography (BPVR) and X-ray reconstruction of moving morphology (XROMM) were used to measure the overall wrist motions of six cadaveric wrists before and after a Motec surgery. Flexion/extension, radioulnar deviation, DTM and circumduction were successfully simulated in both conditions. Additionally, simulated wrist angles and tendon forces were repeatable within single specimens but not between different specimens. The evaluation suggested that simulated wrist motions could be compared between surgical conditions to determine potential mechanical effects of the surgery. Two sets of experiments were performed using the cadaveric simulator, during which wrist angles and tendon forces were recorded throughout seven motion patterns. The first set studied pre- and post-TWA wrists (n = 14). The second set studied the Motec wrist with six different COR positions as well as a pre-TWA condition (n = 6). Both sets of experiments measured tendon forces as an indicator of wrist motion efficiency, captured simulated motions using BPVR and measured wrist angles using XROMM animations. In the final stage of the project, biomechanical wrist joint models will be created to estimate muscle moment arms in anatomical and Motec wrists. Although this work is yet to be completed.Pre/post-TWA comparison revealed no significant differences in ranges of flexion, extension and radioulnar deviation, or in the area of circumduction. Importantly, the Motec wrist was able to produce DTM. Peak flexor tendon forces were significantly lower in Motec wrists during flexion and did not otherwise differ from the pre-TWA condition. Peak extensor tendon forces did not significantly differ apart from a post-TWA decrease in extensor carpi ulnaris force during extension. Data collected during the second set of experiments is yet to be fully processed. We are aiming to determine whether there is a Motec COR position in which the most optimal ROM and efficiency of motion are achieved. Position of the Motec COR will also be compared with the best-fit location of the anatomical wrist COR. Results thus far suggest that Motec TWAs have the potential to recreate functional wrist motion with similar efficiency to the pre-surgical state. Further studies are required to determine whether these conclusions are supported in vivo.