Effects of Femorotibial and Tibiotarsal Joint Ranges of Motion on the Gastrocnemius Muscle-Tendon Working Length in the Canine Cadaveric Limb.

Abstract

OBJECTIVE: &#x2003;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: &#x2003;This is ankinematic study. ANIMALS: &#x2003;Canine cadaveric pelvic limbs (&#x2009;=&#x2009;11). PROCEDURES: &#x2003;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: &#x2003;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&#x2009;>&#x2009;135&#x2009;degrees and the TTJ was&#x2009;<&#x2009;125&#x2009;degrees, compared with when the FTJ was <135&#x2009;degrees and the TTJ was >125&#x2009;degrees in all groups. CONCLUSIONS: &#x2003;Thirty degrees of free range of motion of the TTJ between 140 and 170&#x2009;degrees did not elongate MF-C in this cadaveric limb study. CLINICAL RELEVANCE: &#x2003;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.