What are the differential diagnoses for a patient with severe hip pain after a traumatic injury, negative X-ray, and ineffective conservative treatment with naproxen (nonsteroidal anti-inflammatory drug)?

Differential Diagnoses for Severe Hip Pain After Trauma with Negative X-ray

The most critical concern is an occult hip fracture, which occurs in 24-39% of patients with negative radiographs but persistent clinical suspicion for fracture, and requires urgent advanced imaging with either CT or MRI to prevent devastating complications like osteonecrosis. 1

Immediate Priority: Rule Out Occult Fracture

Obtain CT hip without IV contrast as the next imaging study if rapid diagnosis is needed, or MRI hip without IV contrast if time permits and comprehensive soft tissue evaluation is desired. 1

Why Occult Fracture Must Be Excluded First:

• 39% of patients with negative radiographs but clinical suspicion have surgical hip fractures when evaluated with MRI as reference standard 1
• CT detects occult fractures in 24.1% of cases with negative X-rays and changes management in 20% 1
• CT sensitivity is 94% and specificity is 100% for occult hip fractures 1
• MRI approaches 100% sensitivity for fracture detection 1
• Delayed diagnosis increases risk of osteonecrosis and prolonged immobility 1

Specific Fracture Types to Consider:

• Nondisplaced femoral neck fractures - most common occult fracture 1
• Intertrochanteric fractures with radiographically occult extension - isolated greater trochanter fractures on X-ray frequently have intertrochanteric extension on MRI 1
• Basicervical femoral neck fractures 2
• Stress fractures 2

Additional Differential Diagnoses After Fracture Excluded

Soft Tissue Injuries (Require MRI Without Contrast):

If MRI shows no fracture, evaluate for these soft tissue pathologies which are highly prevalent in trauma patients with negative radiographs: 1, 2

• Muscle/tendon tears - particularly gluteal tendons, iliopsoas, or hip flexors 2
• Trochanteric bursitis - inflammation of bursa over greater trochanter 1, 2
• Iliopsoas tendinopathy or bursitis 2
• Labral tears - though typically require MR arthrography for definitive diagnosis if specifically suspected 1, 2
• Ligamentous injuries - including hip capsule disruption 2

Nerve Compression/Injury:

Consider nerve pathology if numbness or radiating pain is present: 2

• Obturator nerve compression 2
• Lateral femoral cutaneous nerve injury (meralgia paresthetica) 2
• Sciatic nerve compression - particularly if pain radiates down leg 2

Referred Pain Sources:

Lumbar spine pathology must be considered if hip imaging is unrevealing: 2

• Lumbar radiculopathy - L2-L4 nerve roots can present as hip pain 2
• Lumbar facet arthropathy 2
• Sacroiliac joint dysfunction 2

Pelvic Fractures:

38% of patients with acute hip pain and negative hip radiographs have extrafemoral pelvic fractures: 1

• Pubic rami fractures 1
• Sacral fractures 1
• Acetabular fractures 1

Diagnostic Algorithm

1. If excruciating pain persists after negative X-ray, obtain CT hip without IV contrast immediately (faster) or MRI hip without IV contrast (more comprehensive) 1

2. If CT is negative but clinical suspicion remains high, proceed to MRI - CT has 50 documented false-negatives in meta-analysis 1

3. If MRI shows no fracture, the same MRI evaluates soft tissue pathology including tendon tears, bursitis, muscle injuries, and nerve compression 1, 2

4. Consider image-guided diagnostic hip joint injection if pain source remains unclear - helps differentiate intra-articular from extra-articular pathology 2

5. If hip imaging is completely negative, obtain lumbar spine MRI to evaluate for referred pain 2

Critical Pitfalls to Avoid

• Never assume negative X-ray excludes fracture in trauma patients with severe persistent pain - up to 39% have occult fractures 1
• Do not delay advanced imaging beyond 2-3 days if pain worsens - occult fractures may require urgent surgical intervention 2
• Do not proceed directly to MR arthrography - this is only for suspected labral tears, not acute trauma evaluation 1, 2
• Avoid bone scan - insufficient evidence and inferior to CT/MRI 1
• Do not use CT with IV contrast - provides no additional benefit for fracture or soft tissue evaluation 1

Pain Management Considerations

While pursuing diagnosis, acetaminophen is non-inferior to NSAIDs for minor musculoskeletal trauma and may be safer, particularly if patient has cardiovascular risk factors or is elderly 1. However, since naproxen has already failed, consider opioid analgesia for severe pain while diagnostic workup proceeds, recognizing increased side effect profile. 1