THR: Femoral Head Size

- Discussion:
       - 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.





Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Saturday, February 27, 2016 10:07 am