Management of Acetabular Bone Loss

CAUSES of Bone Loss

  • Osteolysis
    • Wear debris induced (most common)
    • Implant migration – traumatic/atraumatic
    • Infection
  • Fracture
  • Iatrogenic (intra-operative)
  • Stress Shielding

DIAGNOSIS

  • Plain XR
  • Judet views
  • CT scan

STAGING/CLASSIFICATION – PAPROSKY

Depends on: 1. Degree of bone loss 2. Degree of migration 3. Maintenance of acetabular rim

  • TYPE 1
    • Minimal bone loss
    • No migration
    • Intact rim
  • TYPE 2
    • <50% bone loss
    • <3cm migration
    • Intact rim
  • TYPE 3

    • 50% bone loss

    • 3cm migration

    • Loss of rim

(These are subdivided into a, b, c depending on position of bone loss – ischial loss being worst and position of migration)

MANAGEMENT OPTIONS

IMPACTION GRAFTING

  • Morcelised graft impacted by reverse reaming
  • Cup can be cemented but usually uncemented in situ
  • Supplement with screws and use large (jumbo) cups if necessary
  • Needs an intact rim in place

JUMBO CUPS + IMPACTION GRAFTING

  • For larger defects
  • Needs >50% intact host bone
  • Supplement with screws and graft
  • Cups are porous/trabecular metal/HA coated
  • (More often than not, the above 2 methods will suffice)

ANTIPROTRUSIO CAGES

  • Indicated when there is extensive bone loss and no intact rim
  • Require use of cement, therefore longevity in question
  • Are placed over impaction grafting – work by spreading the load of the cup over a wider area
  • Require greater dissection ∴ dislocation risk increased

STRUCTURAL ALLOGRAFTS +/- CAGE

  • Use large grafts to fill defects then cages and cement as necessary
  • For severe defects in the hands of experts only

HIGH HIP CENTRE

  • Placement of cup about 3.5 cm above teardrop
  • Utilises host bone BUT:
    • Shortens leg
    • Decreases abductor lever arm
  • Therefore, use long neck/trochanteric slide/high offset stem, etc.
  • Not a recommended practice but is an option
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