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