Hebrew University Medical School, Tzameret, Ein Kerem, Jerusalem, Israel.
Department of Orthopaedics, Assaf HaRofeh Medical Center, Zerifin, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
Clin Biomech (Bristol). 2020 Dec;80:105146. doi: 10.1016/j.clinbiomech.2020.105146. Epub 2020 Aug 16.
Tibial stress fractures in military recruits occur beginning with the fourth week of training. In and ex vivo tibial strain experiments indicate that the repetitive mechanical loading during this time may not alone be sufficient to cause stress fracture. This has led to the hypothesis that the development of tibial stress fracture is mediated by the bone remodeling response to high repetitive strains. This study assesses the differences in the strain and angle of the principal strain during military field activities versus common civilian activities.
In vivo strain measurements were made from a rosette strain gauge bonded to the midshaft of the medial tibia. Measurements of principal strains and their angles were made while performing level and inclined walking and running on an asphalt surface, while fast walking up and down stairs, while performing a standing vertical jump and while zig-zag running up and down a 30° inclined dirt hill.
The angle of the principal strain varied little (5.40° to +2.74°) during activities performed on engineered surfaces. During zig-zag running on a dirt hill the strain levels were higher (maximum shear = 4290 με). At the pivot points of zig-zag running the angle of the principal strain varied between -115° to -123° downhill and between -32.8° to -51° uphill.
Activities that mimic those performed by infantry recruits on irregular hilly surfaces result in higher tibial strains and have more variation in principal strain angles than activities of ordinary civilian life performed on engineered surfaces.
新兵在训练的第四周开始出现胫骨应力性骨折。在体内和体外胫骨应变实验中表明，在此期间重复的机械加载可能不足以单独导致应力性骨折。这导致了这样的假设，即胫骨应力性骨折的发展是由高重复应变引起的骨重塑反应介导的。本研究评估了军事野外活动与普通民用活动中主应变的应变和角度的差异。
通过粘合在内侧胫骨中段的花键应变计进行体内应变测量。在沥青表面上进行水平和倾斜行走和跑步、快速上下楼梯、进行站立垂直跳跃以及在 30°倾斜土丘上进行之字形跑步时，测量主应变及其角度。
在工程表面上进行的活动中，主应变的角度变化很小（5.40°至+2.74°）。在土丘上之字形跑步时，应变水平更高（最大剪应变=4290με）。在之字形跑步的枢轴点，主应变的角度在下山时变化范围为-115°至-123°，在上山时变化范围为-32.8°至-51°。
模仿步兵新兵在不规则丘陵地形上进行的活动会导致胫骨的应变更高，并且主应变角度的变化比在工程表面上进行的普通平民生活活动更多。
