title: The effect of orientation of the acetabular component on outcome following total hip arthroplasty with small diameter hard-on-soft bearings.
abstract: We assessed the orientation of the acetabular component in 1070 primary total hip arthroplasties with hard-on-soft, small diameter bearings, aiming to determine the size and site of the target zone that optimises outcome. Outcome measures included complications, dislocations, revisions and ΔOHS (the difference between the Oxford Hip Scores pre-operatively and five years post-operatively). A wide scatter of orientation was observed (2sd 15°). Placing the component within Lewinnek's zone was not associated withimproved outcome. Of the different zone sizes tested (± 5°, ± 10° and ± 15°), only ± 15° was associated with a decreased rate of dislocation. The dislocation rate with acetabular components inside an inclination/anteversion zone of 40°/15° ± 15° was four times lower than those outside. The only zone size associated with statistically significant and clinically important improvement in OHS was ± 5°. The best outcomes (ΔOHS > 26) were achieved with a 45°/25° ± 5° zone. This study demonstrated that with traditional technology surgeons can only reliably achieve a target zone of ±15°. As the optimal zone to diminish the risk of dislocation is also ±15°, surgeons should be able to achieve this. This is the first study to demonstrate that optimal orientation of the acetabular component improves the functional outcome. However, the target zone is small (± 5°) and cannot, with current technology, be consistently achieved.
authors: University of Oxford, Windmill Road, Oxford OX3 7LD, UK.
authors: G
authors: G
authors: Grammatopoulos
authors: University of Oxford, Windmill Road, Oxford OX3 7LD, UK.
authors: G E R
authors: GE
authors: Thomas
authors: University of Oxford, Windmill Road, Oxford OX3 7LD, UK.
authors: H
authors: H
authors: Pandit
authors: University of Oxford, Windmill Road, Oxford OX3 7LD, UK.
authors: D J
authors: DJ
authors: Beard
authors: University of Bath, Claverton Down, Bath BA2 7AY, UK.
authors: H S
authors: HS
authors: Gill
authors: University of Oxford, Windmill Road, Oxford OX3 7LD, UK.
authors: D W
authors: DW
authors: Murray
mesh_terms: D000077:Acetabulum; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery; D011474:Prosthesis Design; D016896:Treatment Outcome
keywords: Cup orientation; Dislocation; Hip arthroplasty; OHS; Outcome; acetabular anteversion; acetabular inclination