Post-Reduction Imaging for Posterior Shoulder Dislocation
An axillary or scapular Y view is absolutely essential to confirm successful reduction of a posterior shoulder dislocation, as anteroposterior (AP) views alone miss over 60% of posterior dislocations. 1
Required Radiographic Views
Post-reduction imaging must include a minimum three-view series 1:
- AP view in internal rotation - provides baseline assessment but is insufficient alone 1
- AP view in external rotation - adds complementary information but still inadequate as sole view 1
- Axillary or scapular Y view - this is the critical view that definitively confirms reduction status 1
Why the Axillary/Y View is Non-Negotiable
The axillary or scapular Y view is vital because glenohumeral dislocations are routinely misclassified on AP views alone, with posterior dislocations being misdiagnosed in over 60% of cases initially 1, 2. On these orthogonal views, you can directly visualize whether the humeral head has returned to its normal anatomic position relative to the glenoid 1.
Modified Axillary Techniques for Trauma Patients
If the patient cannot tolerate the standard axillary view due to pain or limited range of motion 3, 4:
- Modified axillary view - performed with the patient standing upright and bending forward with 30-45 degrees craniocaudal tube angulation, which is less painful while still providing adequate visualization 3
- Modified trauma axial (MTA) - an alternative that does not require patient movement and is suitable for trauma patients 4
- Tangential scapula view - can substitute when axillary views are not feasible 2
Post-Reduction Assessment Goals
Beyond confirming reduction, these post-reduction radiographs serve to 1:
- Identify fractures obscured by the dislocation - particularly the reverse Hill-Sachs defect (anteromedial humeral head compression fracture characteristic of posterior dislocations) 1
- Evaluate for neurovascular compromise - critical assessment following any reduction attempt 1
- Detect associated injuries - especially rotator cuff tears in older patients 1
When to Escalate to CT
CT without contrast should be obtained if 1:
- Radiographs are equivocal despite proper views
- Symptoms persist after apparent reduction
- You need better characterization of the reverse Hill-Sachs defect, as CT is superior to radiography for identifying this injury 1
- Complex fracture patterns require surgical planning 1
Critical Pitfall to Avoid
Never rely on AP views alone to confirm successful reduction of a posterior dislocation - this is the single most common reason these injuries are missed, with failure to obtain proper orthogonal views leading to delayed diagnosis that averages 66 days and significantly worsens outcomes 2, 5, 6. The correlation between time to correct diagnosis and clinical outcome is substantial, with early diagnosis being essential for optimal results 6.