Objective This study aimed to describe changes in the length of the gastrocnemius muscle-tendon unit between the medial fabella and the calcaneus (MF-C) at different femorotibial joint (FTJ) and tibiotarsal joint (TTJ) angle combinations in the canine limb.

Study Design This is an ex vivo kinematic study.

Animals Canine cadaveric pelvic limbs (n = 11).

Procedures One cadaveric pelvic limb was dissected to identify the anatomical origin and insertion of the gastrocnemius muscle-tendon unit for the radiographic landmark determination. The radiographic landmarks of the FTJ and TTJ were identified by lateral view radiographs. A series of lateral radiographs were evaluated to measure the linear MF-C at all combinations of the FTJ and TTJ angles. A mathematical model was defined for MF-C.

Results The MF-C is associated with the FTJ and TTJ by a linear trigonometric relationship. Higher rate of increase in the MF-C was observed when the FTJ was > 135 degrees and the TTJ was < 125 degrees, compared with when the FTJ was <135 degrees and the TTJ was >125 degrees in all groups.

Conclusions Thirty degrees of free range of motion of the TTJ between 140 and 170 degrees did not elongate MF-C in this cadaveric limb study.

Clinical Relevance Some degrees of free range of motion may be possible in the TTJ during tendon healing based on our cadaveric study without causing excessive change in the MF-C, although this concept should not be applied until isometric contractions of muscles are clearly understood. The relationship between the MF-C and tension at tenorrhaphy should be evaluated.

目的 本研究旨在描述犬肢不同股胫关节（FTJ）和胫跗关节（TTJ）角度组合下内侧小腿和跟骨（MF-C）之间腓肠肌肌腱单位长度的变化。

研究设计 这是一项离体运动学研究。

动物 犬尸体骨盆四肢 ( n  = 11)。

程序 解剖一具尸体骨盆肢体以确定解剖学起源和腓肠肌肌腱单元的插入，用于放射学标志确定。FTJ 和 TTJ 的 X 线标志是通过侧位 X 线片确定的。评估了一系列横向 X 光片以测量所有 FTJ 和 TTJ 角组合的线性 MF-C。为 MF-C 定义了一个数学模型。

结果 MF-C 通过线性三角关系与 FTJ 和 TTJ 相关联。与FTJ <135度且TTJ>125度时相比，FTJ>135度且TTJ<125度时MF-C的增加率更高。

结论 在这项尸体肢体研究中，TTJ 在 140 到 170 度之间的 30 度自由运动范围不会延长 MF-C。

临床相关性 根据我们的尸体研究，在肌腱愈合期间，TTJ 可能有一定程度的自由运动范围，而不会导致 MF-C 过度变化，尽管在清楚了解肌肉的等长收缩之前不应应用此概念。应评估 MF-C 与腱膜张力之间的关系。