Dislocation
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 -Acetab. Position
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 Intra-op- Fractures 
 Cement Herniation
Follow-up Study
 Bony Abnormalities
 Fracture
 Heterotopic Bone
 Non Union
 Hardware Failure
 -Polyethylene Wear
 -Dislocation
 Osteolysis
 Loosening
 Infection
Arthrography
CT and MRI
References

Dislocation

Incidence:

  • 1-3% for primary total hip arthroplasties (Ali Khan, Lewinnek)
  • 16% for revision arthroplasties (Manaster)
  • Usually occurs early in convalescence
  • Patients must avoid hip flexion greater than 90 degrees (shoes and socks must be put on with adaptive equipment, and any hip adduction (no crossing of legs).

Etiology

  • Inadequate adjustment of soft tissue tension at time of surgery leading to instability
  • Loss of abductor mechanism, usually due to detachment of the greater trochanter
  • Shortening of limb with short femoral neck and high acetabular component
  • Malpositioned prosthetic components
    • Optimal acetabular component positioning
      • Anteversion 15 +/- 10 degrees
      • Lateral inclination 40 +/- 10 degrees. 
    • Malpositioned acetabular component
      • Steep lateral inclination is associated with superior dislocation
      • Retroverted cup is associated with posterior dislocation (Coventry)
      • Anteverted cup is associated with anterior dislocation (Lewinnek)

 


Dislocated total hip replacement


Dislocated femoral component secondary to loose acetabular cup with reverse acetabular inclination


Dislocated bipolar hemiarthroplasties in 2 different patients.


 

Dislocated femoral component secondary to steep acetabular cup inclination, pre and post revision. Note constraining ring about femoral head, which helps maintain head in cup


Dislocated femoral component related to non union of greater trochanteric osteotomy. Post operative radiograph with constraining ring about femoral head, which helps maintain head in cup. Greater trochanter resected.


Dislocated acetabular cup and femoral component


Dislocated femoral component and acetabular cup in grossly loose arthroplasty. CT guided aspiration to rule out infection.


 

 

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