What is the preferred imaging modality, ultrasound (US) or Magnetic Resonance Imaging (MRI), for diagnosing small greater trochanteric bursitis?

Ultrasound vs MRI for Diagnosis of Small Greater Trochanteric Bursitis

Ultrasound is the preferred imaging modality for diagnosing small greater trochanteric bursitis due to its accuracy, cost-effectiveness, and ability to evaluate superficial structures like the trochanteric bursa. 1, 2

Advantages of Ultrasound for Greater Trochanteric Bursitis

• Ultrasound is a noninvasive, radiation-free technique that can effectively evaluate specific superficial structures such as the trochanteric bursa and abductor tendons 1
• Ultrasound can reliably detect trochanteric bursitis, joint effusions, bursal collections, capsular and bursal thickening, and synovitis 1
• Ultrasound allows for dynamic assessment, which is particularly useful for evaluating the relationship between structures during movement 1
• Ultrasound can be used to guide therapeutic injections, providing both diagnostic information and potential treatment in the same session 1
• Ultrasound has demonstrated high accuracy in detecting trochanteric bursitis with 92% accuracy in cadaveric studies 3

Limitations of Ultrasound

• Ultrasound is user-dependent, requiring skilled operators for optimal results 1
• Differentiation between bursitis and gluteus medius tendinosis may be difficult with ultrasound, and these conditions may coexist 1
• In cases of extreme obesity, ultrasound may have limitations in visualizing deeper structures 4

Role of MRI in Greater Trochanteric Bursitis

• MRI can assess peritrochanteric structures including the gluteus minimus and medius muscles, abductor tendons, and the trochanteric bursa 1
• MRI is particularly useful when there is suspicion of associated pathologies such as abductor tendon tears or fatty atrophy of the gluteus muscles 1
• MRI with STIR (Short Tau Inversion Recovery) sequences has been shown to demonstrate abnormal increased signal in trochanteric bursae, which may not be visible on standard T1 or T2 sequences 5
• Non-contrast MRI is generally sufficient; there is no relevant literature documenting additional benefit of MRI with IV contrast for evaluating trochanteric bursitis 1

Clinical Implications and Decision-Making

• Radiographs should be obtained first in most cases to rule out other causes of hip pain, such as arthritis or bone tumors 1, 6
• Ultrasound should be considered the first-line imaging modality after radiographs when trochanteric bursitis is suspected 1, 2
• MRI should be reserved for cases where:
  • Ultrasound findings are equivocal 1
  • There is suspicion of deeper pathology not well visualized on ultrasound 1
  • Associated abductor tendon pathology needs to be evaluated 1

Important Clinical Considerations

• Greater trochanteric pain syndrome is often misattributed solely to bursitis; studies show that only 20.2% of patients with greater trochanteric pain have true bursitis on ultrasound 2
• The majority of patients with greater trochanteric pain have pathology involving the gluteus medius and minimus tendons (49.9% with tendinosis) and/or the iliotibial band (28.5% with thickening) 2
• Ultrasound can help differentiate between these conditions, guiding more appropriate treatment 2
• For therapeutic injections, ultrasound guidance improves accuracy and outcomes at 6 months compared to landmark-guided injections 4, 7

Practical Approach to Imaging Selection

1. Begin with radiographs to rule out bony abnormalities 1, 6
2. If trochanteric bursitis is suspected, proceed with ultrasound as the first advanced imaging modality 1, 2
3. Consider MRI only if:
   • Ultrasound is inconclusive 1
   • There is suspicion of deeper pathology 1
   • Associated tendon or muscle pathology needs detailed evaluation 1
   • Patient factors limit ultrasound visualization 4