Morphologic and Kinematic Adaptations of the Subtalar Joint after Ankle Fusion Surgery in Patients with Varus-type Ankle Osteoarthritis

项目摘要 胫距关节融合术，或“踝关节融合术”，是创伤后踝关节的金标准手术治疗 骨关节炎（OA）。踝关节融合至少在短期内可以缓解疼痛;然而， 胫距关节对距下关节提出了新的要求，这可能超过软骨的极限， 继发性OA大多数接受踝关节融合手术的患者术前对线畸形 胫距关节和距下关节值得注意的是，60%的踝关节OA患者存在踝关节内翻对线不良， 胫距关节最近发现同侧距下关节呈代偿性外翻 在大约一半的内翻型踝关节OA患者中，对侧内翻-外翻畸形 倾向于中和腿和后足的整体对齐，使其在大体临床上看起来正常。 检查不幸的是，虽然目前踝关节融合术的手术建议提供了明确的指导， 如何矫正胫距关节内翻对线不良，对代偿性外翻未作规定 距下关节对线我们最近完成的R21项目的结果说明了外科医生的潜力 对踝关节融合进行策略性调整，以控制术后活动、关节间隙距离和一致性 的距下关节，这反过来又可能介导继发性OA。尽管如此，踝关节融合手术的具体效果 对距下关节的形态和功能的影响尚未在体内进行纵向评价。我们的总体目标是 确定导致踝关节融合后患者预后较差的机械和结构因素。R01 本文提出的解决这一目标，通过定量，纵向表征踝关节的影响， 融合手术对活体距下关节形态和功能的影响。在这里，我们采取集中，机械的外观 将踝关节内翻OA患者分为两个相等的组（伴和不伴代偿性外翻） 距下关节对齐;每组n = 24）。根据我们的初步数据，我们假设患者 距下关节术前代偿性对线的患者发生形态改变的风险更大- 踝关节融合术后24个月时的功能关系和不良结局。目标1将量化如何 踝关节融合改变了距下关节的排列和形态， 由承重计算机断层扫描构建的模型。目标2将量化踝关节融合 在行走、上楼梯和下楼梯过程中，使用双 荧光透视。目的3将综合这些数据，以确定和隔离的作用，术前对线的距下 关节对距下关节形态、体内运动和患者结局的影响。如果成功，该项目将提供 第一次也是唯一一次对踝关节融合效果的机械理解。我们预计，完成这些 aims还将为我们进行未来的干预性研究提供先决条件， 评价在手术时考虑外翻补偿是否会产生更好的结局。

PROJECT SUMMARY Tibiotalar arthrodesis, or ‘ankle fusion’, is the gold standard surgical treatment for posttraumatic ankle osteoarthritis (OA). Ankle fusion brings pain relief, at least in the short term; however, elimination of motion at the tibiotalar joint imposes new demands at the subtalar joint, which may exceed the limit of cartilage and result in secondary OA. Most patients undergoing ankle fusion surgery have preoperative deformities in the alignment of the tibiotalar and subtalar joints. Notably, 60% of all patients with ankle OA have varus malalignment of the tibiotalar joint. Recently, it was discovered that the ipsilateral subtalar joint adopts ‘compensatory’ valgus alignment in approximately half of those patients with varus-type ankle OA. Opposing varus-valgus deformities tend to neutralize the overall alignment of the leg and hindfoot, making it appear normal on gross clinical inspection. Unfortunately, while current surgical recommendations for ankle fusion provide clear guidance for how to correct varus malalignment of the tibiotalar joint, they make no stipulation for compensatory valgus alignment of subtalar joint. Results from our recently completed R21 project illustrate the potential for surgeons to strategically align the ankle fusion to control for postoperative motion, joint space distance, and congruency of the subtalar joint, which could in turn mediate secondary OA. Still, the specific effects of ankle fusion surgery on the form and function of the subtalar joint have not been evaluated longitudinally in-vivo. Our broad goal is to identify mechanical and structural factors that lead to inferior patient outcomes after ankle fusion. The R01 proposed herein addresses this goal through quantitative, longitudinal characterization of the effects of ankle fusion surgery on the form and function of the subtalar joint in-vivo. Here, we take a focused, mechanistic look at patients with varus ankle OA that are subdivided into two equal groups (with and without compensatory valgus alignment of the subtalar joint; n = 24 per group). Guided by our preliminary data, we hypothesize that patients with preoperative compensatory alignment of the subtalar joint are at greater risk of experiencing altered form- function relationships and inferior outcomes at 24 months post ankle fusion surgery. Aim 1 will quantify how ankle fusion changes the alignment and morphology of the subtalar joint from longitudinal statistical shape models constructed from weight-bearing computed tomography scans. Aim 2 will quantify how ankle fusion changes the in vivo kinematics of the subtalar joint during walking, stair ascent, and stair descent using dual fluoroscopy. Aim 3 will synthesize these data to identify and isolate the role preoperative alignment of the subtalar joint has on subtalar joint morphology, in vivo motion, and patient outcomes. If successful, this project will provide the first and only mechanistic understanding of the effects of ankle fusion. We anticipate that completion of these aims will also provide prerequisite information for us to pursue a future interventional study, where we would evaluate whether accounting for valgus compensation at the time of surgery yields better outcomes.