Cohen Tamara L, Altiok Haluk, Wang Mei, McGrady Linda M, Krzak Joseph, Graf Adam, Tarima Sergey, Smith Peter A, Harris Gerald F
Orthopaedic and Rehabilitation Engineering Center-OREC, Marquette University-MCW, Milwaukee, WI 53233, USA.
Proc Inst Mech Eng H. 2013 Aug;227(8):919-27. doi: 10.1177/0954411913485044. Epub 2013 Apr 26.
The Ponseti method is a widely accepted and highly successful conservative treatment of pediatric clubfoot involving weekly manipulations and cast applications. Qualitative assessments have indicated the potential success of the technique with cast materials other than standard plaster of Paris. However, guidelines for clubfoot correction based on the mechanical response of these materials have yet to be investigated. The current study sought to characterize and compare the ability of three standard cast materials to maintain the Ponseti-corrected foot position by evaluating cast creep response. A dynamic cast testing device, built to model clubfoot correction, was wrapped in plaster of Paris, semi-rigid fiberglass, and rigid fiberglass. Three-dimensional motion responses to two joint stiffnesses were recorded. Rotational creep displacement and linearity of the limb-cast composite were analyzed. Minimal change in position over time was found for all materials. Among cast materials, the rotational creep displacement was significantly different (p < 0.0001). The most creep displacement occurred in the plaster of Paris (2.0°), then the semi-rigid fiberglass (1.0°), and then the rigid fiberglass (0.4°). Torque magnitude did not affect creep displacement response. Analysis of normalized rotation showed quasi-linear viscoelastic behavior. This study provided a mechanical evaluation of cast material performance as used for clubfoot correction. Creep displacement dependence on cast material and insensitivity to torque were discovered. This information may provide a quantitative and mechanical basis for future innovations for clubfoot care.
庞塞蒂方法是一种广泛接受且非常成功的小儿马蹄内翻足保守治疗方法，包括每周进行手法治疗和打石膏。定性评估表明，该技术使用标准巴黎石膏以外的其他石膏材料也可能取得成功。然而，基于这些材料力学响应的马蹄内翻足矫正指南尚未得到研究。本研究旨在通过评估石膏蠕变响应，来表征和比较三种标准石膏材料维持庞塞蒂矫正后足部位置的能力。一个用于模拟马蹄内翻足矫正的动态石膏测试装置，分别用巴黎石膏、半刚性玻璃纤维和刚性玻璃纤维包裹。记录了对两种关节刚度的三维运动响应。分析了肢体 - 石膏复合材料的旋转蠕变位移和线性度。发现所有材料随时间的位置变化都很小。在石膏材料中，旋转蠕变位移有显著差异（p < 0.0001）。蠕变位移最大的是巴黎石膏（2.0°），其次是半刚性玻璃纤维（1.0°），然后是刚性玻璃纤维（0.4°）。扭矩大小不影响蠕变位移响应。归一化旋转分析显示为准线性粘弹性行为。本研究对用于马蹄内翻足矫正的石膏材料性能进行了力学评估。发现蠕变位移取决于石膏材料且对扭矩不敏感。这些信息可能为未来马蹄内翻足护理创新提供定量和力学基础。
