Centre for Biomedical Engineering, Indian Institute of Technology Delhi, New Delhi, 110016, India.
Centre for Biomedical Engineering, Indian Institute of Technology Delhi, New Delhi, 110016, India; Department of Biomedical Engineering, All India Institute of Medical Sciences, New Delhi, 110029, India.
Comput Methods Programs Biomed. 2022 Sep;224:106994. doi: 10.1016/j.cmpb.2022.106994. Epub 2022 Jul 3.
The ankle and foot are among the most critical load-bearing joints in the human anatomy. Anatomically accurate human body models are imperative to understanding the mechanics of injury and musculoskeletal disorders. A typical human ankle-foot anatomy consists of 25 DOFs, 112 dense connective tissues (DCTs) (92 ligaments, one capsule and 19 fasciae), 30 tendons, and 65 muscles. Existing models possess less than half of the DOFs and physiological elements. In this work, we have developed an ankle-foot joint complex musculoskeletal model for the OpenSim® platform by incorporating 24 degrees of freedom (DOF) comprising of 66 DCTs (46 ligaments, one 1 capsule and 19 fasciae), 30 tendons, and 65 muscles.
Computed tomography (CT) data of human ankle joint-foot complex was segmented using Mimics ® (Version 17.0, Materialise, Belgium) to obtain models of the cartilages and bones of the ankle joint-foot complex. The position and resting lengths of the DCTs were attained from the MRI data and literature. Five joints, namely, tibiotalar, subtalar, chopart, tarsometatarsal (TMT), and metatarsophalangeal (MTP) joints and their joint axes were formulated to yield 24 DOFs. A forward simulation was carried out at each joint of the ankle-foot complex within their respective range of motions. The strains, instantaneous strain rates, and forces developed in the ligaments during the simulation were studied.
During plantar-dorsiflexion of the tibiotalar joint, the anterior tibio-talar ligament (aTTL) yielded the maximum strain compared to all other ligaments. Anterior tibio-fibular ligament (aTFL) experienced extreme strain during subtalar inversion. Hence, the coupled kinematics of subtalar inversion and plantar flexion are failure-prone activities for aTFL. The chopart, TMT, and MTP joints yielded maximum strains or forces for several bundles at the extremes of the range of motion. This signifies that rotations of these joints to their extreme range of motion are prone to failure for the bundles attached to the joint complex.
The results illustrate the potential application of the proposed OpenSim® ankle-foot model in understanding the ligament injury mechanism during sports activity and its prevention. Researchers can use the proposed model or customise it to study complex kinematics, understanding injury mechanisms, testing fixtures, orthosis or prosthesis, and many more in the domain of musculoskeletal research.
踝关节和足部是人身体中最重要的承重关节之一。准确的人体解剖模型对于理解损伤和肌肉骨骼疾病的力学机制至关重要。一个典型的人类踝关节-足部解剖结构由 25 个自由度、112 个致密结缔组织（DCT）（92 条韧带、一个囊和 19 个筋膜）、30 条肌腱和 65 条肌肉组成。现有的模型只包含不到一半的自由度和生理元素。在这项工作中，我们通过纳入包含 24 个自由度（DOF）的踝关节-足部关节复合体运动学模型，为 OpenSim®平台开发了一个踝关节-足部关节复合体运动学模型，该模型包含 66 个 DCT（46 条韧带、一个囊和 19 个筋膜）、30 条肌腱和 65 条肌肉。
使用 Mimics ®（版本 17.0，Materialise，比利时）对人类踝关节-足部复合体的 CT 数据进行分割，以获得踝关节-足部复合体的软骨和骨骼模型。DCT 的位置和静息长度是从 MRI 数据和文献中获得的。五个关节，即距下关节、距下关节、跗跖关节、跗跖关节（TMT）和跖趾关节（MTP）及其关节轴被制定，以产生 24 个自由度。在踝关节-足部复合体的每个关节的各自运动范围内进行了正向模拟。研究了在模拟过程中韧带产生的应变、瞬时应变率和力。
在距下关节的跖屈-背屈过程中，与所有其他韧带相比，前距下胫腓韧带（aTTL）产生的应变最大。在距下关节内翻时，前胫腓骨韧带（aTFL）经历了极端的应变。因此，距下关节内翻和跖屈的耦合运动是 aTFL 易发生故障的活动。跗跖关节、TMT 和 MTP 关节在运动范围的极限处为多个束产生最大应变或力。这意味着这些关节旋转到其极限运动范围时，附着在关节复合体上的束容易发生故障。
结果表明，所提出的 OpenSim®踝关节模型可用于理解运动过程中韧带损伤的机制及其预防。研究人员可以使用所提出的模型或对其进行定制，以研究复杂的运动学、理解损伤机制、测试夹具、矫形器或假体等，这些都是肌肉骨骼研究领域的内容。
