Systemic Lupus Erythematosus - Musculoskeletal

Musculoskeletal complaints are the most common reason a patient with SLE first presents to a clinician, and they remain the leading cause of morbidity through the disease course. The orthopaedic surgeon encounters SLE in three principal scenarios: a hand deformity that mimics rheumatoid arthritis (Jaccoud arthropathy), avascular necrosis of the femoral head in a young patient on steroids, and the perioperative management of an SLE patient listed for arthroplasty or fracture fixation. Each scenario has a defined evidence base and a checklist that examiners love to test.

SLE is one of the classic causes of multifocal AVN. A young patient on steroids with one painful joint should trigger MRI of at least both hips and both knees; some centres add shoulders and ankles. The detection of pre-collapse disease changes management from arthroplasty to joint-preserving core decompression. Missing the contralateral lesion is a recurring exam pitfall.

Q: What is the structural basis of Jaccoud arthropathy? A: Capsuloligamentous laxity without bony erosion. Chronic synovitis in SLE weakens the MCP volar plate, collateral ligaments, and extensor hood, allowing tendon subluxation and reducible deformity. The articular cartilage is preserved - this is the key distinction from RA, where the deformity is fixed and erosive on X-ray.

Q: What is the dominant modifiable risk factor for AVN in SLE? A: Cumulative corticosteroid dose. The risk rises sharply with cumulative prednisolone greater than 3-5 g, daily doses greater than 20 mg, and pulse methylprednisolone. Non-modifiable contributors include Raynaud phenomenon, vasculitis, and antiphospholipid antibodies. Steroid-sparing strategies (azathioprine, MMF, belimumab) are central to AVN prevention.

Q: What is the most appropriate imaging for suspected AVN of the femoral head in a young SLE patient with normal X-rays? A: MRI of both hips and the knees. MRI is the gold standard for pre-collapse AVN, demonstrating bone marrow oedema and the pathognomonic double-line sign on T2. Bilateral imaging is mandatory because 30-50% of SLE AVN is multifocal; contralateral disease is often asymptomatic at presentation.

Q: A patient on 8 mg/day prednisolone is listed for total hip arthroplasty. What is your steroid plan? A: Stress-dose hydrocortisone cover. Continue the morning dose; give 50 mg IV hydrocortisone at induction, then 25 mg IV every 8 hours for 24-48 hours, then taper back to the oral dose. Abrupt withdrawal risks adrenal crisis. Do not stop hydroxychloroquine - it reduces post-operative flare and thrombosis risk.

Q: When is perioperative bridging anticoagulation indicated in SLE? A: Definite antiphospholipid syndrome with prior thrombosis. A single positive aPL test without clinical events is not APS. For patients with lupus anticoagulant, anti-cardiolipin, or anti-beta2 GPI on two occasions 12 weeks apart AND a history of thrombosis, surgery is a high-risk trigger for catastrophic APS and extended anticoagulation (often 4-6 weeks or longer) is indicated. Liaise with haematology.