How to manage avascular necrosis of the hip in a patient with tuberous sclerosis and a recent renal transplant?

Management of Avascular Necrosis of Hip in a Patient with Tuberous Sclerosis and Recent Renal Transplant

The management of avascular necrosis (AVN) of the hip in a patient with tuberous sclerosis complex (TSC) and recent renal transplant should prioritize nephron-sparing approaches while addressing the AVN, with mTORC1 inhibitor therapy being the cornerstone of treatment due to its dual benefits for both conditions. 1, 2

Initial Assessment and Multidisciplinary Approach

• A multidisciplinary team approach involving nephrology, orthopedics, and transplant specialists is essential for coordinated care in this complex case 1
• Complete assessment should include:
  • Staging of AVN (radiographic evaluation with MRI preferred) 3
  • Current kidney graft function (creatinine, eGFR, proteinuria) 1
  • Current immunosuppressive regimen evaluation 2

Management Algorithm for AVN in TSC Post-Transplant

Step 1: Optimize Immunosuppression

• Consider switching to an mTORC1 inhibitor-based immunosuppressive regimen (e.g., rapamycin/sirolimus) 2
  • mTORC1 inhibitors provide dual benefits:
    • Effective immunosuppression for the transplanted kidney 2
    • Therapeutic effect on TSC manifestations by targeting the underlying pathophysiology 4, 2
  • Monitor for proteinuria which may develop or worsen with mTORC1 inhibitor therapy 1

Step 2: Conservative Management for Early AVN

• For stage I-II AVN, conservative management may be sufficient 5
  • Limited weight-bearing with assistive devices 3
  • Physical therapy to maintain range of motion 5
  • Pain management with non-nephrotoxic analgesics 5
• Conservative management can be successful in controlling symptoms in approximately 40% of renal transplant patients with AVN of the hip 5

Step 3: Surgical Interventions (if conservative management fails)

• Core decompression for early-stage AVN (stage I-II) 3

  • Performed under diascopic guidance with cannulated drill 3
  • Postoperative protocol: early verticalization with crutches for 6 weeks 3
  • Timely intervention can eliminate pain and prevent or delay bone destruction 3

• For advanced AVN (stage III-IV):

  • Consider joint-preserving procedures in younger patients 3
  • Total hip arthroplasty for end-stage disease with significant pain and disability 6
  • Surgical planning must account for long-term immunosuppression and potential for impaired healing 6

Special Considerations for TSC with Renal Transplant

• Avoid nephrotoxic medications that could compromise graft function 4
• Regular monitoring of kidney graft function is essential as kidney disease is the most common cause of death in adults with TSC 1
• Annual standardized blood pressure measurements and kidney function tests 1
• Continue surveillance for TSC manifestations in native kidneys if not previously removed 7

Pitfalls and Caveats

• AVN in transplant patients is often related to corticosteroid use - consider minimizing steroid exposure if possible 3, 6
• Pain from AVN may present later than radiographic changes - maintain high suspicion even with minimal symptoms 3
• When clinical signs of AVN arise but standard imaging is negative, consider advanced imaging (SPECT or contrast MRI) 3
• Delayed diagnosis and treatment of AVN can lead to progressive joint destruction requiring more invasive procedures 3
• In patients with bilateral nephrectomy prior to transplant, mTORC1 inhibitors remain beneficial for non-renal TSC manifestations 2, 7

Follow-up Protocol

• Regular orthopedic evaluation every 3-6 months to assess AVN progression 3
• Transplant nephrology follow-up to monitor graft function and adjust immunosuppression 1
• Imaging surveillance:
  • MRI for AVN progression assessment 3
  • Kidney/abdominal imaging for TSC manifestations if native kidneys remain 1