You Should Obtain Plain Radiographs
Despite the seemingly low-energy mechanism, plain radiographs of the shoulder/scapular region are indicated in this patient given his multiple risk factors for occult fracture.
Clinical Reasoning
Your patient has three critical risk factors that substantially elevate fracture risk even with minor trauma:
1. Spinal Muscular Atrophy (SMA) on Risdiplam
- SMA causes progressive muscle weakness and atrophy, resulting in abnormal biomechanics and reduced protective muscular support around joints 1
- Chronic muscle weakness leads to altered force distribution across bones during even minor trauma
- While risdiplam stabilizes motor function in adults with SMA 2, 3, it does not reverse pre-existing muscle weakness or restore normal protective mechanisms
2. Unknown Form of Dwarfism
- Skeletal dysplasias frequently involve abnormal bone architecture, altered bone density, and atypical fracture patterns
- Without knowing the specific diagnosis, you cannot assume normal bone quality or typical fracture thresholds
- Many forms of dwarfism predispose to fractures from minimal trauma that would not injure typical bone
3. Scapular Location
- Scapular fractures are frequently missed on initial clinical examination 1
- CT studies show scapular fractures are "frequently missed on radiographs, especially when they are nondisplaced" 1
- The scapula's complex three-dimensional anatomy makes clinical assessment unreliable
Guideline-Based Approach
The 2025 ACR Appropriateness Criteria explicitly state that radiographs are the preferred initial diagnostic modality in cases of acute shoulder pain because they can delineate shoulder malalignment and most shoulder fractures 1. The guidelines emphasize that:
- A standard trauma series should include minimum 3 views: AP views in internal and external rotation plus an axillary or scapula-Y view 1
- These orthogonal views are "vital in evaluating traumatic shoulder injuries" as pathology "can be misclassified on AP views" 1
- Radiographs provide the necessary bony anatomy assessment "which are the 2 primary concerns in management of acute traumatic shoulder pain" 1
Critical Pitfalls to Avoid
Do not rely on mechanism alone in patients with underlying bone or neuromuscular disease. The "low-energy" mechanism that seems reassuring in a healthy 21-year-old becomes potentially significant when:
- Baseline muscle weakness cannot absorb or distribute forces normally
- Bone quality may be compromised
- Protective reflexes are impaired
Do not assume clinical examination can exclude fracture in the scapular region. Even experienced clinicians miss nondisplaced scapular fractures on physical exam, and these injuries require imaging for detection 1.
What to Look For on Examination
Before imaging, assess for:
- Point tenderness over the scapular body, spine, acromion, or coracoid process
- Visible deformity or asymmetry comparing both scapulae
- Pain with active or passive range of motion, particularly abduction and forward flexion
- Crepitus with scapular movement
- Neurovascular status of the upper extremity
However, even if examination seems reassuring, proceed with radiographs given this patient's risk profile.
If Radiographs Are Normal But Clinical Suspicion Persists
Should initial radiographs be negative or indeterminate but pain persists:
- CT without IV contrast is the most useful modality for detecting scapular fractures, especially nondisplaced ones 1
- CT "is advantageous over radiography in identifying subtle nondisplaced fractures" 1
- MRI without contrast can identify bone marrow edema/contusion if CT is negative 1
The combination of SMA, unknown skeletal dysplasia, and scapular pain location creates sufficient fracture risk to warrant initial imaging regardless of mechanism 1.