Spratley E M, Matheis E A, Hayes C W, Adelaar R S, Wayne J S
Orthopaedic Research Laboratory, Departments of Biomedical Engineering and Orthopaedic Surgery, Virginia Commonwealth University, P.O. Box 843067, Richmond, VA, 23284-3067, USA.
Ann Biomed Eng. 2015 Aug;43(8):1947-56. doi: 10.1007/s10439-014-1195-1. Epub 2014 Dec 3.
A cohort of adult acquired flatfoot deformity rigid-body models was developed to investigate the effects of isolated tendon transfer with successive levels of medializing calcaneal osteotomy (MCO). Following IRB approval, six diagnosed flatfoot sufferers were subjected to magnetic resonance imaging (MRI) and their scans used to derive patient-specific models. Single-leg stance was modeled, constrained solely through physiologic joint contact, passive soft-tissue tension, extrinsic muscle force, body weight, and without assumptions of idealized mechanical joints. Surgical effect was quantified using simulated mediolateral (ML) and anteroposterior (AP) X-rays, pedobarography, soft-tissue strains, and joint contact force. Radiographic changes varied across states with the largest average improvements for the tendon transfer (TT) + 10 mm MCO state evidenced through ML and AP talo-1st metatarsal angles. Interestingly, 12 of 14 measures showed increased deformity following TT-only, though all increases disappeared with inclusion of MCO. Plantar force distributions showed medial forefoot offloading concomitant with increases laterally such that the most corrected state had 9.0% greater lateral load. Predicted alterations in spring, deltoid, and plantar fascia soft-tissue strain agreed with prior cadaveric and computational works suggesting decreased strain medially with successive surgical repair. Finally, joint contact force demonstrated consistent medial offloading concomitant with variable increases laterally. Rigid-body modeling thus offers novel advantages for the investigation of foot/ankle biomechanics not easily measured in vivo.
建立了一组成人获得性平足畸形刚体模型，以研究单纯肌腱转移联合不同程度的跟骨内移截骨术（MCO）的效果。经机构审查委员会（IRB）批准，对6名确诊的平足患者进行了磁共振成像（MRI）检查，并利用其扫描结果建立了患者特异性模型。模拟了单腿站立状态，仅通过生理关节接触、被动软组织张力、外在肌肉力量和体重进行约束，且不假定理想化的机械关节。使用模拟的内外侧（ML）和前后位（AP）X线片、足压力描记法、软组织应变和关节接触力对手术效果进行量化。不同状态下的影像学变化各不相同，肌腱转移（TT）+10 mm MCO状态的平均改善最大，通过ML和AP距骨-第一跖骨角得以证明。有趣的是，14项测量指标中有12项在仅进行TT后显示畸形增加，不过随着MCO的加入，所有增加均消失。足底力分布显示前足内侧负荷减轻，同时外侧负荷增加，使得矫正程度最高的状态外侧负荷增加9.0%。预测的弹簧、三角肌和足底筋膜软组织应变变化与先前的尸体研究和计算研究结果一致，表明随着连续手术修复，内侧应变降低。最后，关节接触力显示内侧持续卸载，同时外侧有不同程度的增加。因此，刚体建模为研究足/踝关节生物力学提供了新的优势，这些生物力学在体内不易测量。
