Summary
The aim was to determine the relative contribution of the glenohumeral ligaments/joint
capsule complex and the limited joint volume/adhesion-cohesion (LJV/AC) mechanisms
to the static stability of the canine glenohumeral joint (GHJ). The GHJ of 32 complete
cadaver specimens were manipulated to determine the presence of gross laxity (>2mm
translation) at joint angles of 150°, 135° and 90°. Following the removal of the peri-articular
muscles, laxity was measured by applying a 15N force to the scapula in a variety of
directions whilst the humerus was fixed to a jig. This was repeated for the abovementioned
angles in intact joints and after venting and flushing to eliminate the LJV/AC mechanisms.
Results of clinical palpation and biomechanical studies were compared. Manipulation
revealed a marked variation between joints although there was a tendency for progressive
laxity as the joint was flexed. This finding was supported by the biomechanical study
that also demonstrated no significant difference between intact and vented joints
except in a cranio-caudal direction at 135° and 90°, and in a medial/lateral direction
at 135°. Static stabilisers permitted a wide range of motion. Individual clinical
palpations did not correlate well with biomechanical findings. Manipulation was difficult
to perform and is unlikely to be a reliable method for determining subtle joint laxity.
The static stabilisers do not appear to play a significant role in providing joint
constraint during normal range of motion (except extension). Diagnoses of pathological
laxity attributable to the static stabilisers should be made with caution and surgical
treatments should take cognizance of the above-mentioned biomechanical features.
Keywords
Glenohumeral joint - dog - shoulder - static stabilisers - limited joint volume