SLAP Lesion Diagnosis
MR arthrography is the gold standard imaging modality for diagnosing suspected SLAP tears, with sensitivity of 80-95% and specificity of 85-91%. 1, 2
Diagnostic Algorithm
Step 1: Initial Imaging
- Start with plain radiographs (AP views in internal/external rotation plus axillary or scapula-Y view) to exclude fractures, dislocations, and other bony pathology 1
- Radiographs are typically noncontributory for labral pathology but are essential to rule out alternative diagnoses
Step 2: Advanced Imaging Selection
If radiographs are normal and physical exam suggests labral tear:
MR arthrography is the preferred study 1, 3:
- Sensitivity: 80.4-95.6% for SLAP tears 2, 4
- Specificity: 85.7-90.7% 2, 4
- Superior to nonenhanced MRI, which has only 63% sensitivity 2
- 3-T MRI (with or without contrast) is superior to 1.5-T imaging 2
Alternative options when MR arthrography unavailable:
- CT arthrography: Comparable to MR arthrography for SLAP detection but inferior for partial rotator cuff tears 1, 3
- Use only if MRI contraindicated
- Noncontrast MRI: May be preferred in acute traumatic settings when joint effusion already present (acts as natural contrast) 1, 3
Age-Based Considerations
- Patients <35 years: MR arthrography generally recommended as instability predominantly labral-related 5
- Patients >35 years: Consider that rotator cuff pathology becomes more common; MR arthrography still superior for detecting both labral and partial cuff tears 5
Physical Examination Correlation
While imaging is definitive, physical exam findings support diagnosis:
- O'Brien's (active compression) test: 90% sensitivity 6
- Mayo dynamic shear test: 80% sensitivity 6
- Jobe's relocation test: 76% sensitivity 6
- Any one positive test: 100% sensitivity 6
Critical caveat: Physical examination alone cannot definitively diagnose SLAP tears—imaging confirmation is essential before surgical planning 7
Imaging Interpretation Requirements
MR arthrography must be performed and interpreted by experienced musculoskeletal radiologists 1. Studies show significant variability:
- Surgeon interpretation: 72% sensitivity
- Radiologist interpretation: 50% sensitivity (when not specialized) 6
- This expertise-dependence is critical for accurate diagnosis
Modalities to Avoid
Ultrasound has no role in SLAP diagnosis 1, 3:
- Cannot adequately visualize superior labrum
- Inferior to MRI for all intra-articular pathology
CT without contrast is not appropriate 1:
- Cannot assess labral soft tissue
- Reserved only for bone loss assessment when MRI unavailable
Key Clinical Pitfalls
Selection bias in studies: Published MR arthrography sensitivities may be inflated; one study of clinically unstable shoulders found only 65% sensitivity 1, suggesting real-world performance may be lower than reported
False negatives occur: Even with MR arthrography, 4-15% false positive rate and 4% false negative rate exist 4
Type I SLAP lesions: Often not clinically relevant and should be considered negative findings 8
Arthroscopy remains the definitive diagnostic standard when imaging is equivocal and clinical suspicion remains high 7