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Radiographic evaluation of developing instability of the Mecron cementless, threaded acetabular prostheses
J L Seelen1, J D Bruijn, L M Kingma
1Department of Diagnostic Radiology, Maria Hospital, Tilburg, The Netherlands.
Purpose:
To evaluate radiographically the history of the Mecron acetabular prosthesis.
Material And 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.