Meardon Stacey A, Edwards Brent, Ward Erin, Derrick Timothy R
Des Moines University, Post Professional Doctorate of Physical Therapy, 3200 Grand Ave., Des Moines, IA 50312, USA.
Foot Ankle Int. 2009 Oct;30(10):998-1004. doi: 10.3113/FAI.2009.0998.
Stress fractures of the lower extremity are common in military and running populations. Research on the effectiveness of orthotics in modifying bone strain is limited. Our hypothesis was that custom and semi-custom foot orthotics would equally decrease bone strain of the second metatarsal.
Eight cadaver specimens were cast for two types of orthotics, a custom and semi-custom device, using neutral plaster casts. Cadaver specimens, mounted to a dynamic gait simulator, walked over a force platform while force and bone strain data were collected. Peak bone strains, strain rates and tendon forces during the stance phase for each condition were analyzed using repeated measures analysis of variance and effect sizes.
Condition effects were present for tension strain, shear strain, compression rate and shear rate. Specifically, custom orthotics significantly decreased the aforementioned bone strains and strain rates (< or = 0.01 for all) and the semi-custom orthotic decreased tension strains and shear strain rates (p = 0.05 and 0.03, respectively). The effect of custom and semi-custom devices only differed significantly for compression and shear strain (p= 0.04 and 0.02, respectively) with custom orthotics having a greater effect.
Both custom and semi-custom orthotics modified the second metatarsal bone strain and strain rate. The use of custom orthotics during simulated walking decreased second metatarsal bone strains and strain rates more effectively than semi-custom orthotics.
Orthotics may minimize the strain magnitudes and rates of the second metatarsal in walking and therefore are a feasible treatment option for the treatment and prevention of stress injury to the second metatarsal.
下肢应力性骨折在军人和跑步人群中很常见。关于矫形器改变骨应变有效性的研究有限。我们的假设是定制和半定制足部矫形器能同等程度地降低第二跖骨的骨应变。
使用中性石膏模型为八个尸体标本制作两种矫形器，即定制和半定制装置。将尸体标本安装到动态步态模拟器上，在测力平台上行走，同时收集力和骨应变数据。使用重复测量方差分析和效应量分析每种情况下站立期的峰值骨应变、应变率和肌腱力。
在拉伸应变、剪切应变、压缩率和剪切率方面存在条件效应。具体而言，定制矫形器显著降低了上述骨应变和应变率（所有p值均≤0.01），半定制矫形器降低了拉伸应变和剪切应变率（分别为p = 0.05和0.03）。定制和半定制装置的效果仅在压缩应变和剪切应变方面有显著差异（分别为p = 0.04和0.02），定制矫形器的效果更大。
定制和半定制矫形器均能改变第二跖骨的骨应变和应变率。在模拟行走过程中使用定制矫形器比半定制矫形器更有效地降低第二跖骨的骨应变和应变率。
矫形器可能会使行走时第二跖骨的应变大小和应变率最小化，因此是治疗和预防第二跖骨应力性损伤的一种可行治疗选择。
