Radiographic evaluation of developing instability of the Mecron cementless, threaded acetabular prostheses.
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.
Seelen
J L
JL
Department of Diagnostic Radiology, Maria Hospital, Tilburg, The Netherlands.
Bruijn
J D
JD
Kingma
L M
LM
Bernoski
F P
FP
Bloem
J L
JL
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