This CT study asked whether the shape of the posterior glenoid rim can help diagnose recurrent atraumatic posterior shoulder instability. It compared 15 posterior instability shoulders with 15 anterior instability and 15 stable shoulders, all with surgical confirmation. The focus was on the presence and craniocaudal length of posteroinferior rim deficiency and on glenoid version.
When a young patient reports posterior shoulder symptoms with no history of trauma, the diagnosis is clinically difficult and the usual imaging clues are often absent. This paper gives you a concrete radiographic anchor: measure the craniocaudal length of any posteroinferior glenoid rim deficiency on CT. A length of 12 mm or more supports the diagnosis (sensitivity 86.7%, specificity 83.3%).
The key teaching point is that a deficiency was common even in stable shoulders, so its mere presence is not diagnostic. The LENGTH is what separates unstable from stable, reflecting how much posterior articular surface remains to resist translation.
Remember that reversed Hill-Sachs lesions and labral tears are rare in the atraumatic form, unlike locked posterior dislocation. Increased retroversion supports the diagnosis but is not reliable on its own. Treat the 12 mm cutoff as a supportive clue requiring clinical correlation, not a final rule, given the small sample.
This CT study asked whether the shape of the posterior glenoid rim can help diagnose recurrent atraumatic posterior shoulder instability. It compared 15 posterior instability shoulders with 15 anterior instability and 15 stable shoulders, all with surgical confirmation. The focus was on the presence and craniocaudal length of posteroinferior rim deficiency and on glenoid version.
When a young patient reports posterior shoulder symptoms with no history of trauma, the diagnosis is clinically difficult and the usual imaging clues are often absent. This paper gives you a concrete radiographic anchor: measure the craniocaudal length of any posteroinferior glenoid rim deficiency on CT. A length of 12 mm or more supports the diagnosis (sensitivity 86.7%, specificity 83.3%).
The key teaching point is that a deficiency was common even in stable shoulders, so its mere presence is not diagnostic. The LENGTH is what separates unstable from stable, reflecting how much posterior articular surface remains to resist translation.
Remember that reversed Hill-Sachs lesions and labral tears are rare in the atraumatic form, unlike locked posterior dislocation. Increased retroversion supports the diagnosis but is not reliable on its own. Treat the 12 mm cutoff as a supportive clue requiring clinical correlation, not a final rule, given the small sample.