Data from: Achilles tendon moment arm in humans is not affected by inversion/eversion of the foot: a short report

The triceps surae primarily acts as plantarflexor of the ankle joint. However, the group also causes inversion and eversion at the subtalar joint. Despite this, the Achilles tendon moment arm is generally measured without considering the potential influence of inversion/eversion of the foot during plantarflexion. This study investigated the effect of foot inversion and eversion on the plantarflexion Achilles tendon moment arm. Achilles tendon moment arms were determined using the centre-of-rotation method in MR images of the left ankle of 11 participants. The foot was positioned at 15° dorsiflexion, 0° or 15° plantarflexion using a Styrofoam wedge. In each of these positions the foot was either 10° inverted, neutral or 10° everted using an additional Styrofoam wedge. Achilles tendon moment arm in neutral foot position was 47.93 ± 4.54 mm and did not differ significantly when the foot was positioned in 10° inversion and 10° eversion. Hence, inversion/eversion position of the foot may not considerably affect the length of the Achilles tendon moment arm. This information could be useful in musculoskeletal models of the human lower leg and foot and when estimating Achilles tendon forces during plantarflexion with the foot positioned in inversion or eversion.

小腿三头肌（triceps surae）主要作为踝关节的跖屈肌发挥功能，但该肌群同时可介导距下关节（subtalar joint）的内翻（inversion）与外翻（eversion）运动。然而，当前跟腱（Achilles tendon）力矩臂（moment arm）的常规测量通常未考虑跖屈（plantarflexion）过程中足部内翻/外翻带来的潜在影响。本研究探究了足部内翻与外翻状态对跖屈时跟腱力矩臂的影响。研究通过11名受试者左侧踝关节的磁共振成像（MR images），采用旋转中心法计算跟腱力矩臂：受试者足部被固定于15°背屈（dorsiflexion）、0°或15°跖屈体位，借助泡沫塑料楔块实现上述角度设置；在此基础上，通过额外的泡沫塑料楔块将足部调整至10°内翻、中立位或10°外翻体位。足部处于中立位时，跟腱力矩臂为47.93±4.54 mm，当足部处于10°内翻或10°外翻状态时，该数值无显著统计学差异。因此，足部内翻/外翻体位或许不会对跟腱力矩臂的长度产生显著影响。该研究结果可为人类小腿及足部的肌肉骨骼模型（musculoskeletal models）构建，以及在足部处于内翻或外翻体位时估算跖屈过程中的跟腱力提供参考依据。