title: Poor results from the isoelastic total hip replacement: 14-17-year follow-up of 149 cementless prostheses.
abstract: BACKGROUND
  To overcome the mismatch between a stiff stem and the more elastic bone, the concept of isoelasticity was introduced in the 1970s. This concept was based on the assumption that the implant and the bone should deform as one unit to avoid stress shielding. The Robert Mathys (RM) cementless total hip replacement (THR) was one of the earliest isoelastic designs.
  
  
  METHODS
  From 1984 to 1987, we performed 149 total hip replacements in 135 patients (92 women, mean age 47 (21-72) years) using third-generation Mathys isoelastic polyacetal stem with stainless-steel heads and polyethylene cementless acetabular cups. 11 patients died before revision or before the examination for this study, and 14 were lost to follow-up. Average follow-up time for the remaining 110 patients was 15 (14-17) years.
  
  
  RESULTS
  To date, 69 hips (64 patients) have been revised, 5 due to infection. The 10-year survival rate for any reason was 70% (66-74). In the 46 remaining patients (53 hips), the average HHS was 80 (39-100) points. 13 of these were regarded as radiographic failures, with an average HHS of 75 points.
  
  
  CONCLUSIONS
  The performance of this prosthesis was unacceptably poor. Higher debris production and poor primary fixation are believed to be the main reason for the high failure rate.
authors.affiliation: Valdoltra Orthopaedic Hospital, Jadranska c. 31, 6280 Ankaran, Slovenia. rihard.trebse@ob-valdoltra.si
authors.forename: Rihard
authors.initials: R
authors.lastname: Trebse
authors.forename: Ingrid
authors.initials: I
authors.lastname: Milosev
authors.forename: Simon
authors.initials: S
authors.lastname: Kovac
authors.forename: Martin
authors.initials: M
authors.lastname: Mikek
authors.forename: Venceslav
authors.initials: V
authors.lastname: Pisot
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging; D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods / Q000401:mortality; D001843:Bone Cements; D005260:Female; D005500:Follow-Up Studies; D006621:Hip Joint / Q000000981:diagnostic imaging; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis / Q000401:mortality; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016459:Prosthesis-Related Infections / Q000209:etiology / Q000601:surgery; D011859:Radiography; D012086:Reoperation; D016896:Treatment Outcome
chemical_list: D001843:Bone Cements