title: Effect of femoral head size on polyethylene wear and synovitis after total hip arthroplasty: a sonographic and radiographic study of 39 patients.
abstract: OBJECTIVE
  The role of synovitis and high fluid pressure in the loosening process after total hip arthroplasty has gained increasing attention. We investigated the correlation between head size, polyethylene wear, and capsular distention.
  
  
  METHODS
  We analyzed 39 unrevised, radiographically stable hips that had been operated with 28 or 32 mm femoral heads 10 years earlier because of osteoarthritis. We evaluated radiographic signs of loosening, linear and volumetric polyethylene wear, body mass index, activity level, and age. Sonographic examination was performed to measure capsular distance i.e. the distance between the prosthetic femoral neck and the anterior capsule.
  
  
  RESULTS
  Linear wear was 0.09 mm/year and 0.18 mm/year in the 28 mm and 32 mm groups, respectively (p < 0.001). The volumetric wear was 51 mm(3)/year and 136 mm(3)/year (p < 0.001) and the capsular distance was 13 mm and 17 mm, respectively (p < 0.001). There was a correlation between linear wear (r = 0.54), volumetric wear (r = 0.62), and capsular distance (p < 0.001).
  
  
  CONCLUSIONS
  Wear was greater for the larger femoral head and was correlated to capsular distension.
authors.affiliation: Department of Orthopedics, Kaunas Medical University, Kaunas, Lithuania. sarunas.tarasevicius@gmail.com
authors.forename: Sarunas
authors.initials: S
authors.lastname: Tarasevicius
authors.forename: Otto
authors.initials: O
authors.lastname: Robertsson
authors.forename: Uldis
authors.initials: U
authors.lastname: Kesteris
authors.forename: Romas Jonas
authors.initials: RJ
authors.lastname: Kalesinskas
authors.forename: Hans
authors.initials: H
authors.lastname: Wingstrand