title: Stable fixation of an osseointegated implant system for above-the-knee amputees: titel RSA and radiographic evaluation of migration and bone remodeling in 55 cases.
abstract: OBJECTIVE
  Rehabilitation of patients with transfemoral amputations is particularly difficult due to problems in using standard socket prostheses. We wanted to assess long-term fixation of the osseointegrated implant system (OPRA) using radiostereometric analysis (RSA) and periprosthetic bone remodeling.
  
  
  METHODS
  51 patients with transfemoral amputations (55 implants) were enrolled in an RSA study. RSA and plain radiographs were scheduled at 6 months and at 1, 2, 5, 7, and 10 years after surgery. RSA films were analyzed using UmRSA software. Plain radiographs were graded for bone resorption, cancellization, cortical thinning, and trabecular streaming or buttressing in specifically defined zones around the implant.
  
  
  RESULTS
  At 5 years, the median (SE) migration of the implant was -0.02 (0.06) mm distally. The rotational movement was 0.42 (0.32) degrees around the longitudinal axis. There was no statistically significant difference in median rotation or migration at any follow-up time. Cancellization of the cortex (plain radiographic grading) appeared in at least 1 zone in over half of the patients at 2 years. However, the prevalence of cancellization had decreased by the 5-year follow-up.
  
  
  CONCLUSIONS
  The RSA analysis for the OPRA system indicated stable fixation of the implant. The periprosthetic bone remodeling showed similarities with changes seen around uncemented hip stems. The OPRA system is a new and promising approach for addressing the challenges faced by patients with transfemoral amputations.
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, USA.
authors.forename: Audrey
authors.initials: A
authors.lastname: Nebergall
authors.forename: Charles
authors.initials: C
authors.lastname: Bragdon
authors.forename: Anne
authors.initials: A
authors.lastname: Antonellis
authors.forename: Johan
authors.initials: J
authors.lastname: Kärrholm
authors.forename: Rickard
authors.initials: R
authors.lastname: Brånemark
authors.forename: Henrik
authors.initials: H
authors.lastname: Malchau
mesh_terms: D000328:Adult; D000368:Aged; D000671:Amputation, Surgical / Q000295:instrumentation* / Q000379:methods; D000674:Amputees; D001186:Artificial Limbs; D016723:Bone Remodeling / Q000502:physiology*; D001862:Bone Resorption / Q000503:physiopathology; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery*; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D016348:Osseointegration / Q000502:physiology*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D059869:Radiostereometric Analysis; D012189:Retrospective Studies