What is the management plan for a patient with Avascular Necrosis (AVN) in the lower part of the femur, who is also being treated for Systemic Lupus Erythematosus (SLE) with Mycophenolate Mofetil and Hydroxychloroquine, and Prednisolone?

Management of Avascular Necrosis in the Lower Femur in an SLE Patient on Immunosuppression

For AVN of the distal femur in an SLE patient on mycophenolate mofetil, hydroxychloroquine, and prednisolone, core decompression with cancellous bone grafting should be performed if the lesion is detected early (before significant collapse), while continuing hydroxychloroquine through any surgical intervention and temporarily withholding mycophenolate mofetil one week prior to surgery if the SLE is not severe. 1, 2, 3

Immediate Assessment and Staging

• Obtain MRI of the affected distal femur immediately, as MRI is the most sensitive diagnostic imaging procedure for AVN and allows accurate staging to guide treatment 4
• Stage the AVN using the ARCO classification system, which is widely accepted in Europe and determines treatment approach 4
• Assess whether the SLE is "severe" (currently treated for lupus nephritis, CNS lupus, severe hemolytic anemia, vasculitis, or other organ-threatening manifestations) versus "not severe" 1

Medical Management Strategy

Corticosteroid Optimization

• Reduce prednisolone to the lowest effective dose to prevent progression of AVN, as corticosteroids are a primary risk factor for AVN development and progression 5, 2
• Work with the patient's rheumatologist to taper steroids while maintaining SLE disease control 1

Perioperative Immunosuppression Management (If Surgery Required)

For Not-Severe SLE:

• Withhold mycophenolate mofetil 1 week prior to any surgical intervention 1
• Continue hydroxychloroquine through surgery without interruption 1
• Continue the current daily dose of prednisolone perioperatively rather than stress-dosing 1

For Severe SLE:

• Continue mycophenolate mofetil through surgery to prevent organ-threatening flares 1
• Continue hydroxychloroquine and prednisolone through surgery 1

Surgical Treatment Algorithm

Early Stage AVN (Stages I-II, Before Collapse)

Primary Treatment: Core Decompression with Cancellous Bone Grafting

• Perform core decompression using an 8-mm trephine inserted from below the greater trochanter into the center of the necrotic lesion to within 5 mm of the articular surface 2
• Create two additional trephine tracts with 5-mm or 6-mm trephines 2
• Pack cancellous bone graft (harvested from normal intertrochanteric bone) loosely into the central decompression channel 2
• This approach yields 73% good-to-excellent results at 11-year follow-up for distal femur AVN, with 74% survival rate versus only 23% with conservative management 3

Expected Outcomes:

• Core decompression prevents radiographic progression in 46% of hips versus only 19% with conservative management 2
• Only 7% of patients with small necrotic lesions require total joint replacement after decompression 2
• Even when core decompression ultimately fails, it extends the symptom-free interval by more than 5 years in many patients 3

Advanced Stage AVN (Stages III-IVA, With Collapse)

When Significant Collapse Has Occurred:

• Total knee arthroplasty is the treatment of choice when pain and disability are sufficient to require intervention 6
• Core decompression may still be considered to delay arthroplasty, as it can extend the asymptomatic period even in advanced disease 3

Postoperative Management

Medication Restart Protocol

• Restart mycophenolate mofetil once the wound shows evidence of healing (typically ~14 days), all sutures/staples are removed, there is no significant swelling, erythema, or drainage, and there is no ongoing infection 1
• Monitor closely for SLE flare in the immediate postoperative period, particularly if mycophenolate was withheld 1

Protected Weightbearing

• Institute protected weightbearing for minimum 3 months after core decompression 3
• Conservative management with protected weightbearing alone (without surgery) yields only 11 months average asymptomatic period and 82% proceed to total knee replacement within 6 years 3

Critical Pitfalls to Avoid

• Do not delay surgical intervention once AVN is diagnosed, as earlier treatment yields substantially better results 6, 2
• Do not use conservative management alone (rest and protected weightbearing without surgery), as this has only 18% success rate versus 73% with core decompression 2, 3
• Do not withhold hydroxychloroquine perioperatively, as it should be continued through surgery regardless of SLE severity 1
• Do not stress-dose corticosteroids perioperatively, as continuing the current daily dose is preferred 1
• Avoid extrapolating perioperative medication guidelines to non-arthroplasty procedures, though the principles regarding infection risk versus flare risk remain relevant 1

Long-term Monitoring

• Obtain serial radiographs to monitor for progression, as AVN can progress despite intervention 2, 4
• Maintain close rheumatology follow-up to optimize immunosuppression and minimize corticosteroid exposure 1
• Screen the contralateral limb, as AVN is often bilateral in patients with corticosteroid-associated disease 6