title: Radiographic evaluation of developing instability of the Mecron cementless, threaded acetabular prostheses.
abstract: OBJECTIVE
  To evaluate radiographically the history of the Mecron acetabular prosthesis.
  
  
  METHODS
  The pelvic radiographs of 350 consecutive patients with a smooth threaded acetabular prosthesis type Mecron were retrospectively evaluated (follow-up 1 to 6 years, mean 4 years). A demarcation zone seen at the medial side of the prosthesis was graded from 0 (absent) to 3 (severe). Prostheses with grades 0 and 1 were considered stable and those with grade 3 with or without migration were presumed to be unstable.
  
  
  RESULTS
  At five years, 62 (62%) of the cups were unstable and only 23 (23%) were stable. The rate of migration was unacceptably high, and seen in 43 (43%) patients. Migration was only seen in prosthesis with a grade 3 demarcation.
  
  
  CONCLUSIONS
  Demarcation visible on radiographs is an important sign of instability of the prosthesis. With the grading system it is possible to evaluate radiographically the history of the prosthesis.
authors.affiliation: Department of Diagnostic Radiology, Maria Hospital, Tilburg, The Netherlands.
authors.forename: J L
authors.initials: JL
authors.lastname: Seelen
authors.forename: J D
authors.initials: JD
authors.lastname: Bruijn
authors.forename: L M
authors.initials: LM
authors.lastname: Kingma
authors.forename: F P
authors.initials: FP
authors.lastname: Bernoski
authors.forename: J L
authors.initials: JL
authors.lastname: Bloem
mesh_terms: D000077:Acetabulum; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005069:Evaluation Studies as Topic; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011475:Prosthesis Failure; D011859:Radiography; D012189:Retrospective Studies; D013997:Time Factors