Morphometric and Structural Examination of the Collateral Ligaments of the Canine Elbow Joint

The aim of this study was to describe morphological differences between the lateral collateral ligament (LCL) and the medial collateral ligament (MCL) of the canine elbow joint. Forty forelimbs of 22 dogs (adult German shepherd dogs and shepherd mongrels) were dissected. The length and width of defined segments of the ligaments (i. e. total length, areas of origin and insertion, 'free part', 'humeral part', 'antebrachial part') were measured in extension (160°) and flexion (30°). Statistical analyses of the data were performed using the data analysis software SAS 8.0. In addition the collateral ligaments of ten forelimbs of five shepherd mongrels were studied histologically. The LCL differs from the MCL in the following morphological items: a) the areas of origin and insertion are larger and in consequence the 'free part' of the lateral ligament is shorter; b) the caudal crus of the LCL is fan-shaped with a broad insertion area at the ulna whereas the caudal crus of the MCL remains slim; c) in the LCL the 'humeral part' varies in length depending on extended or flexed position of the joint, which is due to the spiral shape of the capitulum humeri; d) the microscopical structure of the LCL is organized less tightly; the collagen fibre bundles cross in varying angles. Referring to these details the LCL seems to allow and to limit a slight rotation of the forearm when the elbow joint is extremely flexed.