Dislocating THA
Approach to the Dislocating Total Hip Arthroplasty
Patient Factors:
Age
Sex – Female > Male
Non-compliance – ETOH, dementia, stupidity
Etiology Factors:
Dysplasia – weak abductors
Fracture – dislocation is much higher in femoral neck fractures treated with primary THA
Surgery Factors:
1. Sepsis
2. Approach – Posterior vs anterior
3. Malposition of components
A. Acetabulum – excessive retroversion – posterior dislocation
– excessive anteversion – anterior dislocation
B. Femur- excessive retroversion – posterior dislocation
– excessive anteversion – anterior dislocation
4. Component Factors
Head Size – the larger the more stable
Acetabular Rim Elevation – may increase posterior stability, but may impinge and cause dislocation out the front
Offset – the more offset, presumably the more tension on the abductors and the more stable the component will be
The �Head : Neck Ratio� – the ratio of the head diameter and the neck diameter – if the neck diameter is enlarged secondary to a skirt, the head/neck ratio decreases, and the component is more apt to impinge and dislocate
5. Soft Tissue Factors
– impingement – from soft tissue scar or heterotopic ossification
– abductor strength
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