THA – Approach to Dislocating THA

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