Next Steps for Persistent Hip Pain After Total Hip Arthroplasty
For a 70-year-old patient with ongoing hip pain 15 years post-arthroplasty with normal X-rays and failed physical therapy, an MRI without contrast is the most appropriate next diagnostic step to evaluate the cause of persistent pain.
Diagnostic Algorithm for Post-THA Pain
Initial Imaging Assessment
The normal X-ray findings in this case require further investigation, as X-rays alone cannot detect many causes of persistent pain after total hip arthroplasty. According to the ACR Appropriateness Criteria for chronic hip pain, when radiographs are negative, equivocal, or nondiagnostic, MRI without IV contrast is the most appropriate next step with a rating of 9/9 1.
Potential Causes of Pain to Investigate
When evaluating persistent pain after THA with normal radiographs, consider:
Extra-articular soft tissue abnormalities:
- Tendinopathy (particularly iliopsoas impingement)
- Bursitis
- Soft tissue adhesions
Intra-articular issues:
- Component loosening not visible on X-ray
- Polyethylene wear
- Osteolysis in early stages
- Infection (low-grade)
Referred pain sources:
- Spine pathology
- Vascular issues
- Neurogenic causes
Specific MRI Considerations
MRI without contrast is superior to CT for detecting soft tissue abnormalities that may be causing pain 1. MRI can identify:
- Tendon lesions (tendinopathy or tears)
- Bursitis
- Pseudotumors
- Early osteolysis that may not be visible on plain radiographs
Additional Diagnostic Options
If MRI is Contraindicated or Inconclusive
Ultrasound of the hip (rating 7/9) can be considered for evaluating extra-articular soft tissue abnormalities such as tendinitis 1.
Image-guided diagnostic injection (rating 5/9) can help determine if pain is originating from the hip joint itself or surrounding structures 1.
Bone SPECT/CT may be useful if MRI is inconclusive, particularly for identifying loosening or non-hip causes of pain (such as referred pain from the spine) 1.
Common Pitfalls to Avoid
Assuming pain is always from the prosthesis: Pain after THA can originate from sources unrelated to the prosthesis itself, including the spine, surrounding soft tissues, or vascular structures.
Overlooking infection: Even with normal X-rays and laboratory values, low-grade infection should remain in the differential diagnosis.
Premature revision surgery: Identifying the specific cause of pain is crucial before considering revision surgery, as many causes can be treated non-surgically.
Inadequate evaluation of component positioning: Component malposition may not be obvious on standard radiographs but can cause impingement and pain.
Treatment Considerations
Treatment should be guided by the specific diagnosis found on advanced imaging:
For soft tissue pathology: Targeted physical therapy, corticosteroid injections, or arthroscopic intervention may be appropriate 2.
For component issues: Revision surgery may be necessary if loosening, wear, or osteolysis is identified.
For infection: Appropriate antibiotic therapy or surgical intervention based on organism identification and sensitivity.
For referred pain: Treatment directed at the primary source (spine, etc.).
The diagnostic pathway should be systematic and thorough to identify the specific cause of pain, as this will guide the most appropriate treatment approach to improve the patient's morbidity, mortality, and quality of life outcomes.