Vet Comp Orthop Traumatol 2019; 32(06): v-vi
DOI: 10.1055/s-0039-1700556
Georg Thieme Verlag KG Stuttgart · New York

Diagnosis of Medial Shoulder Instability

Samuel P. Franklin
1  Colorado Canine Orthopedics and Rehab, Colorado Springs, Colorado, United States
› Author Affiliations
Further Information

Publication History

Publication Date:
13 November 2019 (online)

Medial shoulder instability is typically attributed to injury of the medial glenohumeral ligament, subscapularis tendon and/or medial joint capsule resulting in laxity or instability of the shoulder joint. The gold standard for assessing the aforementioned anatomic structures and making a clinical diagnosis of medial shoulder instability is arthroscopy. However, arthroscopy is relatively invasive and expensive when used solely as a diagnostic tool and so there is a need to establish a less involved method for diagnosing medial shoulder instability. To this end, a series of seminal studies suggested that measurement of shoulder abduction angles with physical examination can be repeatable and clinically useful.[1] [2] [3] [4] Conversely, another study failed to demonstrate that increased shoulder abduction angles are specific to damage to the medial glenohumeral ligament or subscapularis tendon.[5] Accordingly, it has remained a little unclear how repeatable and accurate this physical examination manoeuvre is among a larger group of practitioners, and whether additional diagnostic techniques could help diagnose medial shoulder instability.

Two studies[6] [7] in this this issue of VCOT had observers measure shoulder abduction angles on cadaveric specimens that were normal and following transection of either the medial glenohumeral ligament alone or the medial glenohumeral ligament plus the subscapularis tendon. Both studies compared the goniometrically measured abduction angles to those obtained using stress radiography or stress fluoroscopy. The studies failed to demonstrate that goniometry consistently provided the same values as those obtained using stress radiography or fluoroscopy. Furthermore, one study[6] showed poor inter-observer repeatability of goniometric measurement of shoulder abduction angles. The other study[7] also showed good inter- and intra-observer repeatability of their stress radiographic technique. Accordingly, both studies question whether palpation with goniometry provides sufficient accuracy, and one study suggests that the described radiographic technique could potentially be developed into a clinically relevant alternative. However, it should also be mentioned that both studies provided data that could be interpreted as supporting goniometry as being useful. In one study, goniometry was significantly different between shoulders that did and did not have the medial glenohumeral ligament transected and correlation between the goniometric and radiographic measures was very good.[7] In the other study, the one board-certified surgeon produced repeatable values and such values were, on average, only 2.9° different than those obtained fluoroscopically.[6]

These studies are particularly valuable in highlighting that we should question whether published results in the hands of other veterinarians are representative of those we would obtain ourselves in clinical practice. It would be ideal if we all perform some self-assessment, preferably that is quantitative in nature, when it comes to how we assess increased shoulder abduction and make a diagnosis of medial shoulder instability. The stress radiographic technique that is described by Livet and colleagues[7] may provide another technique to help meet these objectives.