Initial Diagnostic Test for Elbow Dislocation
Plain radiographs of the elbow are the initial and essential diagnostic test for suspected elbow dislocation. 1
Radiographic Protocol
Standard views to obtain:
- Anteroposterior (AP) view of the elbow 1
- Lateral view of the elbow 1
- External oblique view 2
- Consider radial head-capitellum view for subtle fractures, particularly of the posterior radial head, capitellum, and coronoid process 2
The American College of Radiology explicitly states that conventional radiographs are the first-line imaging modality to exclude fracture or dislocation in acute elbow trauma. 1
Key Radiographic Findings to Assess
Look for these specific features on initial films:
- Joint alignment and presence of dislocation (most commonly posterolateral) 3, 4
- Elbow joint effusion indicated by posterior and anterior fat pad elevation, which implies occult fracture even if no obvious fracture line is visible 1
- Associated fractures: radial head (most common, 50% of adult elbow fractures), coronoid process, olecranon, or medial/lateral epicondyles 1
- Avulsion fractures at tendon and ligament attachment sites 1
Post-Reduction Imaging
After closed reduction, perform stress fluoroscopy immediately to quantify stability: 5
- Test at full extension, 30° of flexion, and with varus/valgus stress in pronation and supination 1, 5
- <10° of joint widening = slight instability (conservative management) 1, 5
10° of joint widening = moderate instability (worse outcomes) 1, 5
- Frank redislocation on stress testing = gross instability requiring surgical fixation 1, 5
Advanced Imaging Indications
CT without contrast is indicated when:
- Radiographs are equivocal or indeterminate for fracture 1
- Coronoid fractures are suspected (these indicate prior dislocation and severe instability) 1, 5
- Complex fracture-dislocation patterns require surgical planning 1, 3
- Need to assess fracture fragment size, displacement, or angulation that affects surgical options 1
The ACR guidelines explicitly state there is no role for CT with contrast, MRI, bone scan, or ultrasound as initial imaging for acute elbow dislocation. 1
Critical Pitfalls
Do not assume stability after reduction - patients with >10° widening on stress fluoroscopy have significantly worse Mayo Elbow Performance Scores (52.6% vs 77.6%, P=0.043). 1, 5
Do not miss coronoid fractures - these are sequelae of dislocation and indicate severe instability requiring CT for full characterization. 1, 5
Do not delay finger motion exercises - initiate active finger exercises immediately post-reduction to prevent functionally disabling hand stiffness. 5