The collateral ligaments of the canine elbow joint: morphometric and structural examination.

摘要

The aim of this study was to describe the morphological differences between the lateral collateral ligament (LCL) and the medial collateral ligament (MCL) of the canine elbow joint. A total of 40 forelimbs from 22 dogs (adult German Shepherd and Shepherd mongrels) were dissected. The length and width of specific segments of the ligaments (total length, areas of origin and insertion, free part, humeral part and antebrachial part) were measured in extension (160 degrees ) and flexion (30 degrees ). In addition, the collateral ligaments of five Shepherd mongrels were studied histologically. The LCL differs from the MCL in the following morphological items: (a) The lateral ligament is bigger than the medial one, its areas of origin and insertion are larger and as a consequence, its free part is shorter; (b) the caudal crus of the LCL is fan-shaped with a long insertion area at the ulna whereas the caudal crus of the MCL remains slim and inserts caudolaterally at the radius; (c) in the LCL, the humeral part varies in length depending on extended or flexed position of the joint; this is due to the spiral outline of the capitulum humeri; (d) the microscopic structure of the LCL is organized less tightly; the collagen fibre bundles cross in varying angles. The following conclusions were drawn: Due to the weaker osseus connection between the humerus and radius, a stronger lateral collateral ligament is necessary to prevent lateral opening of the elbow joint. Crossing the spatium interosseum and inserting laterally at the radius, the caudal part of the MCL restrains a lateral luxation of the forearm. This explains why in most cases of lateral luxation of the antebrachial bones, the MCL will be damaged. Due to the caudolateral insertion of the MCL, the radius is forced to move into a slight supination during flexion of the elbow joint. The cranial crus of the LCL allows and limits this slight rotation of the forearm. This asymmetrical arrangement of the collateral ligaments is of clinical importance..