MRI Pelvis Can Detect Both ASIS Avulsion Fractures and Apophysitis
Yes, MRI of the pelvis is highly effective at detecting both avulsion fractures and apophysitis of the anterior superior iliac spine (ASIS) and anterior inferior iliac spine (AIIS), with near 100% sensitivity for pelvic fractures and excellent visualization of associated soft-tissue inflammation.
Diagnostic Performance of MRI
MRI demonstrates 99% sensitivity for both proximal femoral fractures and fractures of the pelvis, including avulsion injuries 1. The imaging modality excels at detecting:
- Acute avulsion fractures with bone marrow edema and fracture lines clearly visible
- Apophysitis showing inflammation and increased signal at the apophyseal growth plate
- Associated soft-tissue injuries including muscle edema and tendon pathology 2
Multiple case reports confirm MRI successfully identifies AIIS avulsion fractures and apophysitis in adolescent athletes 2, 3, 4, 5. One study specifically demonstrated MRI visualization of "significant inflammation" associated with AIIS avulsion fractures, which correlated with clinical findings 2.
Optimal MRI Protocol
The most efficient and accurate approach uses:
- Coronal STIR (short tau inversion-recovery) sequence - 99-100% sensitivity as a standalone sequence
- Coronal T1 sequence - adds specificity and confidence to the diagnosis 1
This two-sequence protocol balances diagnostic accuracy with scan time, particularly important for adolescent patients who may have difficulty tolerating prolonged imaging.
Clinical Context and Advantages
MRI provides several critical advantages over other modalities:
- Detects radiographically occult fractures when plain films are negative but clinical suspicion remains high 1
- Characterizes fracture morphology including displacement and fragment size, which guides treatment decisions 4
- Visualizes inflammation using both MRI and complementary Doppler ultrasound to track healing 2
- Identifies differential diagnoses including pseudotumors from chronic avulsion injuries that may mimic neoplasms decades after initial trauma 3
Important Caveat
While MRI excels at detecting the presence of AIIS pathology, MRI is unreliable for classifying AIIS morphology compared to 3D CT, showing poor inter-rater agreement (kappa = 0-0.163) 6. If precise morphological classification is needed for surgical planning, particularly for subspinal impingement concerns, 3D CT should be obtained as the reference standard 6.
Practical Algorithm
When evaluating suspected pelvic avulsion or apophysitis:
- Start with plain radiographs - may show obvious displaced fractures
- If radiographs negative but clinical suspicion high (localized tenderness, inability to bear weight, mechanism consistent with avulsion) → obtain MRI pelvis with coronal STIR and T1 sequences 1
- If surgical fixation considered for displaced AIIS fractures → add 3D CT for accurate morphological assessment 6
The ACR Appropriateness Criteria specifically recommend MRI pelvis as the next imaging study after negative radiographs when fracture is suspected 1, and this applies equally to apophyseal injuries in adolescents as it does to proximal femoral fractures in older adults.