title: Evaluation of periprosthetic bone-remodeling after cementless total hip arthroplasty. The influence of the extent of porous coating.
abstract: BACKGROUND
  Total hip arthroplasty changes the levels of stress within the proximal part of the femur, and the femur remodels adjacent to the prosthesis. The stem size and the initial bone-mineral density around the distal portion of the stem affect postoperative bone-remodeling after the insertion of a fully porous-coated metal-cancellous prosthesis. The purpose of this study was to evaluate the influence of the extent of porous coating of this prosthesis on femoral bone-remodeling.
  
  
  METHODS
  A longitudinal examination of sixty-one hips in fifty-four patients was performed. Thirty-one hips in twenty-seven patients with a fully porous-coated stem (Group A) and thirty hips in twenty-seven patients with a proximally porous-coated stem (Group B) were followed for twenty-four to thirty months. Periprosthetic bone-mineral density was measured with dual-energy x-ray absorptiometry at specific intervals after the operation.
  
  
  RESULTS
  In both groups, the greatest loss of bone-mineral density, compared with the initial (three-week) value, was approximately 20 percent in zone 7 at twelve to eighteen months. In other zones, bone-remodeling appeared to cease by twelve months. At the last follow-up evaluation, the loss of bone-mineral density in the distal and middle regions in Group A was significantly greater than that in Group B (p < 0.01 for zone 3 and p < 0.05 for zone 6). In contrast, with the numbers available, there were no significant differences in loss of bone-mineral density in the proximal regions (zones 1 and 7) between the two groups at any follow-up period.
  
  
  CONCLUSIONS
  The extent of porous coating affects bone-remodeling in the distal periprosthetic region rather than in the proximal region. The results in the present report are specific to the particular implants that were studied.
authors.affiliation: Department of Orthopaedic Surgery, Osaka University Medical School, Suita, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: K
authors.initials: K
authors.lastname: Masuhara
authors.forename: K
authors.initials: K
authors.lastname: Ohzono
authors.forename: N
authors.initials: N
authors.lastname: Sugano
authors.forename: T
authors.initials: T
authors.lastname: Nishii
authors.forename: T
authors.initials: T
authors.lastname: Ochi
mesh_terms: D015502:Absorptiometry, Photon; D019644:Arthroplasty, Replacement, Hip; D015519:Bone Density; D016723:Bone Remodeling; D016022:Case-Control Studies; D002484:Cementation; D020099:Coated Materials, Biocompatible; D005260:Female; D005269:Femur / Q000502:physiology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D016062:Porosity; D011474:Prosthesis Design; D013997:Time Factors
chemical_list: D020099:Coated Materials, Biocompatible