(ii) The classification of shoulder instability: new light through old windows!

Anterior Shoulder Instability Is Associated With an Underlying Deficiency of the Bony Glenoid Concavity

“…This finding is likely explained by the fact that the transition between traumatic and atraumatic shoulder instability comprises a large gray area and a clear distinction between the groups is not always possible. 8 In general, the deficiency of glenoid concavity appears to be more pronounced in patients with atraumatic instability than patients with traumatic instability. 8 The introduction of the BSSR allows for quantification of the passive bony stabilizers of the shoulder.…”

“…8 In general, the deficiency of glenoid concavity appears to be more pronounced in patients with atraumatic instability than patients with traumatic instability. 8 The introduction of the BSSR allows for quantification of the passive bony stabilizers of the shoulder. The BSSR is a theoretical percentage predicting the stability of a glenohumeral joint based on CT measurements of its bony configuration by determining the maximum translational force against which a shoulder can be stabilized by a given concavity-compression force.…”

Comparison of two patient-based outcome measures for shoulder instability after nonoperative treatment

“…1 The classification of instability is complex and multifaceted, and placing patients in particular groups is not always clear cut. 23,38 In this study, dislocation was defined as an instability event, with dislocation confirmed by radiographs. Best practice advocates surgical intervention following recurrent, traumatic, unidirectional dislocations, particularly in younger patients.…”

The clinical assessment and classification of shoulder instability

“…Patient presentations are grouped into 3 polar classes: Type I (true TUBS), Type II (true AMBRI), or Type III (muscle patterning or habitual non-structural disorders). In recognition of the continuity between groups, a triangular model was proposed in which a degree of polarity may be tailored to each presentation 53 (Fig. 6).…”

“…Stanmore triangle (developed by Bayley et al, 1986e2004; adapted from Lewis et al53 ). The triangular polarities represent extreme types of instability.…”