Chatzistergos Panagiotis E, Eddison Nicola, Theodorakos Ilias, Chockalingam Nachiappan
School of Science and Engineering, University of Dundee, Dundee, UK.
Centre for Biomechanics and Rehabilitation Technologies, Staffordshire University, Stoke-On-Trent, UK; The Royal Wolverhampton NHS Trust, New Cross Hospital, Wednesfield Road, Wolverhampton, UK.
Med Eng Phys. 2025 Oct;144:104404. doi: 10.1016/j.medengphy.2025.104404. Epub 2025 Jul 28.
Drape-forming is a cost-effective method used worldwide to manufacture bespoke ankle foot orthoses (AFOs). It involves draping a heated polymer material sheet over a positive cast of the user's limb. Previous research has shown that the manual nature of drape-forming can influence the thickness of the final AFO and even lead to structures that are inadequately rigid to be clinically effective. This study assesses the difference between the prescribed and the final thickness of AFOs meant for use by UK's National Health Service (NHS) and estimates its potential impact on AFO rigidity.
A clinically relevant method to measure AFO thickness as part of the manufacturing process was developed and validated. This method was used by three major UK manufacturers for all bespoke rigid AFOs they provided to the NHS within a predefined period. A validated finite element model was used to estimate the impact of the observed difference between prescribed and final thickness on AFO stiffness.
86 AFOs were assessed in total. Final thickness was between 4.0% and 35.5% lower than the prescribed one (median thickness reduction= 17.4%). This discrepancy in thickness led to a relative reduction in AFO stiffness ranging between 7.0% and 80.0% (median stiffness reduction= 30.7%).
The adequacy of AFO thickness cannot be judged based on prescription thickness. Measurements of final thickness as part of standard practice should be considered to enhance the provision of bespoke AFOs. Further research is needed to establish thresholds of acceptable manufacturing-induced deviation from the prescribed AFO thickness.
draping成型是一种在全球范围内用于制造定制踝足矫形器（AFO）的具有成本效益的方法。它涉及将加热的聚合物材料片覆盖在使用者肢体的阳模上。先前的研究表明，draping成型的手工性质会影响最终AFO的厚度，甚至会导致结构刚度不足而无法达到临床效果。本研究评估了英国国家医疗服务体系（NHS）使用的AFO规定厚度与最终厚度之间的差异，并估计了其对AFO刚度的潜在影响。
开发并验证了一种在制造过程中测量AFO厚度的临床相关方法。英国的三家主要制造商在预定义的时间段内为NHS提供的所有定制刚性AFO都使用了该方法。使用经过验证的有限元模型来估计规定厚度与最终厚度之间观察到的差异对AFO刚度的影响。
总共评估了86个AFO。最终厚度比规定厚度低4.0%至35.5%（厚度降低中位数 = 17.4%）。这种厚度差异导致AFO刚度相对降低7.0%至80.0%（刚度降低中位数 = 30.7%）。
不能根据处方厚度来判断AFO厚度是否合适。作为标准操作的一部分，应考虑测量最终厚度，以提高定制AFO的供应。需要进一步研究来确定可接受的制造引起的与规定AFO厚度偏差的阈值。
