多轴向应力在婴幼儿马蹄内翻足跗软骨间运动耦合关系中生物力学研究

It is known that the coupling kinematic relationship between the tarsal bones is the core principle of Ponseti management for clubfoot. The question was proposed that the explanation of coupling kinematic relationship was based on the pathoanatomy of knowledge of adult skeletal foot model, and the biomechanical mechanism between the tarsal bones was poorly reported in the published papers. On the basis of previous investigations, we found that there was close relationship between tarsal coupling kinematic relationship and important elements, such as stress direction, Achilles tendon, equinus, ankle hindfoot joints and tibiofibular syndesmosis, and leading to the realignment and reconstruction of tarsal bones. So, we proposed that multiaxial stress induced the realignment and reconstruction of tarsal bones through the coupling kinematic relationship between the tarsal bones. We will further investigate the biomechanical mechanism of coupling kinematic relationship between the tarsal bones through the biomechanical testing of cadaver specimen, foot finite element foot model based on Chinese digital human girl No.1 (CDH-G1) image database, and high simulation model of clubfoot, and aim to demonstrated how stress direction, Achilles tendon and equinus influence the coupling kinematic relationship between the tarsal bones, and illustrate the correlation between foot ankle joint, tibiofibular syndesmosis and the joints between cuneiforms during the coupling kinematic process. This study is of great significance to the further in-depth understanding of the principle of Ponseti method in correcting the clubfoot deformity as well as of preventive measures of clubfoot recurrence after correction.

Ponseti方法治疗马蹄内翻足的核心原则是利用跗软骨间的运动耦合机制，问题是目前针对该机制的研究基于成人骨骼模型的病理解剖学知识，而对于畸形矫正过程中跗软骨间运动耦合的生物力学机制未见报道。本课题前期预实验发现：畸形矫正过程中应力方向、跟腱、跖屈畸形、踝后足四关节、胫腓下联合与跗软骨间运动耦合关系密切，并最终导致跗软骨形态学重塑。因此，我们提出畸形矫正过程中多轴向应力介导跗软骨间运动耦合关系引起跗软骨对应关系及形态学改变。本项目拟进一步通过人体标本生物力学测试、足踝部数字人有限元模型建立以及马蹄内翻足高仿真模型构建，模拟畸形矫正具体过程并进行生物力学分析，旨在回答畸形矫正过程中应力加载大小、跟腱、跖屈畸形如何影响跗软骨间运动耦合关系，明确踝后足四关节、胫腓下联合、楔骨间关节运动耦合情况及相关性大小。本项目对深入认识Ponseti方法畸形矫正原理、预防治疗后畸形复发具有重要意义。

项目背景：马蹄内翻足畸形矫正过程中，相关跗软骨间运动耦合的解释基于病理解剖学层面，而对于畸形矫正过程中的生物力学机制尚不清楚，且文献中缺乏踝后足四关节、楔骨间关节、下胫腓联合参与运动耦合关系量化研究。.主要研究内容：①借助医学软件图像分割技术，明确各跗骨关节形态及对位关系；②构建足踝部三维可视化数字模型，揭示跟腱挛缩、跖屈畸形与跗软骨间运动耦合关系；③利用三维有限元分析法，阐明踝后足四关节、楔骨间关节、踝周韧带与跗软骨间运动耦合关系。.重要结果：①MRI形态学显示，经治后舟骨存在楔形变，楔舟关节对位欠佳、存在畸形矫正后过度外展情况；②跟腱挛缩程度对跗骨间运动耦合关系影响不大，而跖屈畸形程度影响较大；③所有跗骨间关节均参与畸形矫正过程中运动耦合关系，且距舟、距下、跟骰、舟楔关节耦合效应最大，但舟楔关节（舟骨-内侧楔骨）处于始动地位；④畸形矫正过程中，胫舟、距舟、跟舟韧带牵伸最为强烈。.关键数据及其科学意义：①运动耦合强度：跟腱刚度在40N/mm，80N/mm，200N/mm，400N/mm、1000N/mm未见明显差异，而踝关节在跖屈20°耦合效应最强，其次中立位0°，最小为背伸20°，提示对于严重的马蹄内翻足患者早期行经皮切断术有利于畸形矫正。②跗骨间关节运动耦合关系：距舟关节平均位移变化为12.01mm，舟楔关节为10.50mm，跟骰关节为7.97mm，距下关节为6.99mm，内中楔骨间关节为5.32mm，外侧楔骰关节为3.39mm，中外楔骨间关节为1.19mm；距骨与舟骨节律比约为1:12，跟骨与骰骨约为1:2，距骨与跟骨约为1:7，舟骨与内侧楔骨节律比约为1:1.6，内中外侧楔骨约为2:1.6:1.7，外侧楔骨和骰骨节律比约为1.2:1；提示畸形矫正过程中应重视舟楔关节重要性。③踝周韧带牵伸结果：胫舟韧带约为27.99mm，距舟韧带约为21.03mm、跟舟韧带约为19.18mm，提示胫舟韧带、距舟韧带以及跟舟韧带的挛缩程度与畸形矫正成功与否密切相关。本研究项目对充分认识Ponseti方法畸形矫正原理、明确马蹄内翻足病理解剖学基础提供重要的内容补充，指导临床医生诊疗难治性马蹄内翻足提供理论基础。