Role of the tendons of the biceps brachii and infraspinatus muscles and the medial glenohumeral ligament in the maintenance of passive shoulder joint stability in dogs.
OBJECTIVE
To objectively evaluate the effect of transecting the tendon of the biceps brachii muscle (BBT), tendon of the infraspinatus muscle (IFS), or medial glenohumeral ligament (MGHL) on shoulder joint stability in canine cadavers.


METHODS
81 forelimbs from mature dogs.


METHODS
Cadaver forelimbs were placed in a testing frame and axially preloaded with 4 kg of weight. Shoulder joint stability was tested in neutral joint position, flexion, and extension before and after transection of the BBT (n = 37), IFS (37), or MGHL (7). Humeral translation relative to the glenoid was induced by applying a 3-kg load in each of 3 directions (cranial, lateral, and medial) and quantitatively measured by use of an electromagnetic motion tracking system. Peak translational data were compared in each joint position before and after transection of the BBT, IFS, or MGHL.


RESULTS
When tested in neutral position, the cranial, lateral, and medial translation of the humerus was significantly increased after BBT transection. In the flexed position, translation of the humerus in the cranial and lateral directions was significantly increased after BBT transection. In the extended position, the medial translation of the humerus was significantly increased after BBT transection. Complete medial luxation of all humeral heads occurred following transection of the MGHL.


CONCLUSIONS
The BBT contributes to passive shoulder joint stability in dogs, particularly in the neutral and flexed positions. It also provides medial stability during shoulder joint extension. Complete luxation of the joint occurs when the MGHL is transected.
Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762-6100, USA.
Brian K
BK
Sidaway
Ron M
RM
McLaughlin
Steven H
SH
Elder
Carolyn R
CR
Boyle
Edward B
EB
Silverman
D000818:Animals; D001696:Biomechanical Phenomena; D004285:Dogs / Q000502:physiology*; D007593:Joint Instability / Q000503:physiopathology*; D008023:Ligaments, Articular / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*; D013708:Tendon Injuries / Q000503:physiopathology* / Q000601:surgery; D013710:Tendons / Q000502:physiology*; D016474:Weight-Bearing