OrthoNet

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