title: Large femoral bone loss after hip revision using the uncemented proximally porous-coated Bi-Metric prosthesis: 22 hips followed for a mean of 6 years.
abstract: OBJECTIVE
  Periprosthetic bone loss after uncemented femoral hip revision is a matter of concern. We have used a proximally porous- and hydroxyapatite-coated prosthesis (Bi-Metric) in revision since 1989 and now we report the bone changes. This prosthesis is intended to distribute the forces more evenly and to avoid proximal femoral unloading.
  
  
  METHODS
  22 patients were unilaterally reoperated because of aseptic loosening. Only patients with a healthy contralateral hip were included. Mean age at revision was 69 (55-80) years. Bone defects were graded by Gustilo-Pasternak and Endo-Klinik classifications. Clinical assessment was performed with Harris hip score. We used radiographs and dual-energy X-ray absorptiometry to evaluate migration, femoral remodeling, and bone mineral density after 72 (30-158) months.
  
  
  RESULTS
  The mean Harris hip score was 74 (30-100) points at follow-up. Mild thigh discomfort was present in 1 patient and moderate thigh pain in 3 patients. There was no loosening or subsidence. Osteolysis seen at revision had diminished in 19 of the 22 hips at follow-up. We noted a large reduction in bone mineral density. It was most pronounced in Gruen regions 1, 2, 6, and 7.
  
  
  CONCLUSIONS
  Revision with this stem is a reliable procedure; however, we noted a large degree of proximal bone loss that could lead to later mechanical complications or fractures.
authors.affiliation: Department of Clinical Sciences at Danderyd Hospital, Karolinska Institutet, Stockholm, Sweden. per.adolphson@ds.se
authors.forename: Per Y
authors.initials: PY
authors.lastname: Adolphson
authors.forename: Mats O F
authors.initials: MO
authors.lastname: Salemyr
authors.forename: Olof G
authors.initials: OG
authors.lastname: Sköldenberg
authors.forename: Henrik S G
authors.initials: HS
authors.lastname: Bodén
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods; D001672:Biocompatible Materials; D015519:Bone Density / Q000502:physiology; D001862:Bone Resorption / Q000000981:diagnostic imaging / Q000209:etiology*; D017886:Durapatite; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D005500:Follow-Up Studies; D006622:Hip Prosthesis / Q000009:adverse effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D012086:Reoperation
chemical_list: D001672:Biocompatible Materials; D017886:Durapatite