Complications

Vascular Injury

  • Causes:
    • Cement removal
    • Screw placement
    • Retractor use

Zones for Screw Placement

  • Safe Zone: Posterior Superior (minimal danger to sciatic and superior gluteal vessels & nerves)
  • Danger Zones:
    • Anterior Superior: Danger to external iliac vessels and medial to iliopsoas
    • Anterior Inferior: Obturator vessels, behind quadrilateral plate and obturator foramen
    • Posterior Inferior: Safe for screws <20mm; at risk for pudendal and inferior gluteal vessels, sciatic and inferior gluteal nerves

Management of Hemorrhage

  • Management Options:
    • Pack areas of bleeding
    • Products: Tranexamic acid, transfusion, FFP
    • If severe, call the vascular team, perform retroperitoneal approach and clamping of common iliac artery.
    • Consider pre-operative angiography/vascular standby if cup migration is chronic.

Nerve Injury

Aetiology

  • Sciatic Nerve Injury: 80%
  • Femoral Nerve Injury: 20%
  • Other Nerves: <1%

Sciatic Nerve Injury

  • Risk Factors:
    • Revision surgery
    • Females
    • Lengthening >4cm
  • Causes:
    • Retractor placement posterior inferior to acetabulum
    • Haematoma, cement, cages, screws, direct laceration (uncommon)
    • Most injuries involve the peroneal branch (more lateral, closer to retractors)
    • 20% of cases are complete palsy
  • Management:
    • Foot drop splint, physio to maintain joint motion.
    • If nerve is intact, avoid exploration.
    • If unsure of completeness, explore early if no improvement after 6 weeks.
    • Prognosis:
      • Good indicators: improvement within 3 weeks, delayed symptom onset, incomplete palsy.

Femoral Nerve Injury

  • Less Common:
    • Often caused by retractors not positioned within the capsule.
    • Management involves physiotherapy and knee braces for quads recovery.

Obturator Nerve Injury

  • Uncommon:
    • Caused by deep retractors in obturator foramen or cement extrusion.
    • Main symptom is groin pain.

Superior Gluteal Nerve Injury

  • Risk:
    • Mainly occurs if muscle split in gluteus medius exceeds 5cm.

Leg Length Discrepancy

  • True Lengthening: More common than shortening; usually better tolerated if <1cm; >2.5cm poorly tolerated.
  • Intraoperative Checks:
    • Matching neck cut to templating
    • Shuck test, soft tissue tension, kick-back test, knee palpation, markers with measuring devices.
  • Classification:
    • True: Due to surgical error (e.g., inferior cup placement, inappropriate neck length).
    • Apparent: Due to contracture pre- or post-op.
  • Management:
    • Apparent: Reassurance and physiotherapy for stretching.
    • True: Identify and correct significant issues; shoe raise for minor discrepancies (<2cm).

Fat Embolus Syndrome

  • In THR: Most common in cemented stems in elderly patients.
  • In TKR: Related to intramedullary referencing; risk increases with number of intramedullary rods used.

Pathophysiology of Fat Embolus in THR

  • Cause: Pressurization of canal during stem insertion causes fat and cement embolization, occluding capillaries in the lungs.
  • Symptoms:
    • Rapid hypotension (within 30 minutes)
    • Hypoxia
    • Petechial hemorrhages

Why It’s Worse in Elderly:

  • Osteoporotic bone increases fat dissemination under pressurization.
  • Underlying comorbidities (e.g., chronic pulmonary disease) exacerbate the effects of embolization.

Management

  • Supportive Care:
    • Oxygen
    • Fluids
    • Vasopressors
    • Ventilation if necessary
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