- polyethylene liner: (traditional design)
- references:
- Effect of femoral head size on wear of the polyethylene acetabular component.
- Independent contribution of elevated-rim acetabular liner and femoral head size to the stability of total hip implants.
- 22 mm head
- produces too much linear wear or creep;
- smaller diameter head (22 mm) allow less stress/torque but may result in increased central acetabular wear and dislocation;
- 28 mm head:
- less acetabular strain and lower revision rates are associated w/ use of a twenty-six or 28 mm head;
- smaller diameter head (22-28 mm) allow less stress/torque but may result in increased central acetabular wear / dislocation;
- ref: Dislocation rate after hip arthroplasty within the first postoperative year: 36 mm versus 28 mm femoral heads.
- 32 mm head:
- 32 mm allow increased ROM before it impinges against acetabulum, and therefore theoretically has less dislocation;
- main disadvantage is that it has less net wall thickness, and produces too large a volume of wear debris;
- 36 mm head and larger;
- larger head sizes (32-36 mm) allow increased ROM and reduced dislocation, but have less net wall thickness for
long term wear (unless the liner is lateralized);
- psoas tendonitis
- references:
- Is There a Benefit to Head Size Greater Than 36 mm in Total Hip Arthroplasty?
- No functional benefit of larger femoral heads and alternative bearings at 6 months following primary hip replacement
- Large diameter heads: is bigger always better?
- Dislocation rate after hip arthroplasty within the first postoperative year: 36 mm versus 28 mm femoral heads.
- metal on metal designs begin at 36 mm and go upto greater than 50 mm;
- the larger femoral head size allows for increased stability and less impingement;
- references:
- Why large-head metal-on-metal hip replacements are painful: the anatomical basis of psoas impingement on the femoral head-neck junction.
- references:
- Size of the femoral head and acetabular revision in total hip-replacement arthroplasty.
- Range of Motion and Stability in Total Hip Arthroplasty With 28-, 32-, 38-, and 44-mm Femoral Head Sizes.
- Effect of Femoral Head Diameter and Operative Approach on Risk of Dislocation After Primary Total Hip Arthroplasty.
- Relationship of femoral head and acetabular size to the prevalence of dislocation.