Complications of Arthroplasty

PJI - Septic Sabotage

• Infection of prosthetic joint & periprosthetic tissues; biofilm formation is key.
• Classification by Onset:
  • Early (<3 months): Acute symptoms; often S. aureus.
  • Delayed (3-12 months): Subtle; CoNS, P. acnes.
  • Late (>12 months): Hematogenous seeding.
• Diagnosis: 📌 MSIS Criteria (2018 update).
  • Major Criteria (1 needed): Sinus tract OR 2+ positive cultures (same organism).
  • Minor Criteria (Score ≥6 for PJI):
    • Elevated ESR (>30mm/hr) & CRP (>10mg/L).
    • Synovial WBC >3000/µL or ++Leukocyte Esterase.
    • Synovial PMN% >80%.
    • Positive histology (>5 PMNs/HPF).
    • Single positive culture.
    • Elevated synovial Alpha-Defensin.
• Management:
  • DAIR (Debridement, Antibiotics, Implant Retention): Early PJI, stable implant.
  • Exchange Arthroplasty: 1-stage or 2-stage (gold standard for chronic).

⭐ The Musculoskeletal Infection Society (MSIS) criteria are paramount for diagnosing PJI.

VTE & Bleeds - Clots & Crimson Tides

• VTE (DVT/PE): Major risk post-arthroplasty. 📌 VIRCHOW's triad (Stasis, Hypercoagulability, Endothelial injury).
  • Prophylaxis: Crucial. Mechanical (Graduated Compression Stockings - GCS, Intermittent Pneumatic Compression - IPC) & Pharmacological: LMWH (e.g., Enoxaparin 40mg OD), DOACs (e.g., Rivaroxaban 10mg OD), Warfarin (target INR 2-3). Duration typically 10-35 days.
  • Diagnosis: DVT (Ultrasound Doppler), PE (CT Pulmonary Angiography - CTPA).
  • Management: Therapeutic anticoagulation.
• Bleeding/Hematoma:
  • Risk factors: Anticoagulants, surgical technique, patient factors.
  • Signs: Localized swelling, pain, ecchymosis, wound drainage.
  • Management: Observation, compression dressing. Surgical evacuation if large, rapidly expanding, neurovascular compromise, or suspected infection. Tranexamic acid (TXA) use can ↓ blood loss.

⭐ Routine VTE prophylaxis is mandatory for lower limb arthroplasty unless contraindicated.

Mechanical Failures - Loose, Worn & Broken

• Aseptic Loosening:
  • Most common late failure. Patho: Wear particle-induced osteolysis (macrophage activation → cytokines → osteoclasts).
  • X-ray: Progressive radiolucent lines >2mm at implant-bone/cement-bone interface. Zones: Gruen (femur), DeLee & Charnley (acetabulum).
• Wear & Osteolysis ("Particle Disease"):
  • Particle generation (polyethylene, metal, ceramic, cement) is key.
  • Types of wear: Adhesive (most common), Abrasive (3rd body), Fatigue, Corrosive (metals).
  • Leads to periprosthetic bone loss.
• Implant Fracture/Breakage:
  • Rare. Risk factors: ↑BMI, high activity, implant design/malposition.
  • Common sites: Femoral stem (esp. modular necks), tibial tray, polyethylene liner.

Wear Particle Types & Osteolysis

Neurovascular & HO - Zaps, Pipes & Extra Bone

• Neurovascular Injury:
  • Nerve Palsy:
    • THR: Sciatic n. (esp. posterior approach), Femoral n.
    • TKR: Common Peroneal n. (most frequent), Tibial n., Saphenous n.
    • Risks: limb lengthening, direct trauma, pre-existing neuropathy.
  • Vascular Injury: Femoral/Popliteal arteries most common.
    • Signs: ↓ pulses, expanding hematoma, pallor.
    • Action: Immediate surgical repair.
• Heterotopic Ossification (HO):
  • Pathological extra-articular bone.
  • Classified by Brooker Classification (Grade I-IV).
  • Prophylaxis: NSAIDs (e.g., Indomethacin), single low-dose radiation (700-800 cGy).
  • Treatment: Surgical excision for mature, symptomatic HO.

⭐ The common peroneal nerve is the most frequently injured nerve during Total Knee Arthroplasty, while the sciatic nerve is most at risk during posterior approach Total Hip Arthroplasty.

High‑Yield Points - ⚡ Biggest Takeaways

• PJI (Periprosthetic Joint Infection): Most feared complication; Staph aureus is common. Diagnose with synovial fluid analysis.
• Aseptic Loosening: Most common long-term reason for failure, resulting from polyethylene wear leading to osteolysis.
• DVT/PE (Deep Vein Thrombosis/Pulmonary Embolism): Significant risk post-arthroplasty; early mobilization and prophylaxis are essential.
• Dislocation: Frequent in THR (Total Hip Arthroplasty); risk factors include surgical approach and component positioning.
• Periprosthetic Fractures: Classified by Vancouver classification (femur); can occur intra- or post-operatively.
• Nerve Injury: Specific to joint (e.g., sciatic/common peroneal nerve in THR; axillary nerve in shoulder arthroplasty).