Recently, total hip arthroplasty has become popular method of treatment of hip lesion. But aseptic loosening remains the leading cause of faiure of cemented total hip arthroplastics.
The loosening tend to decrease with time for femoral components. Whereas, the loosening tends to increase for acetabular components.
This has prompted change in cup design, improvement in cementing techniques, and use of cementless acetabular components.
The threaded acetabular component design gains initial purchase by threaded engagement and provides long term macro-imterlock fixation. But there was a little clinical information about cup mig?ation and loosening of cementless threaded
acetabular
components.
Since 1983, we have used P-M pattern prosthesis, which consist of cementless threaded acetabular component and anatomically adapted femoral stem. We have studied 31 patient (39 hips) about incidence of clinical and radiographic sign of
implant
instability (migration and radiolucency around prosthesis) at the department of orthopaedic surgery, Inje University Medical College, Seoul Paik Hospital during Jan. 1984to dec. 1989.
The follow up periods ranged from 2 to 5 years, with an average of 3 year and 8 months.
@ES the results were as follows:
1. The average Harris hip score was improved from 45.8 to 87.7 after operation.
2. Over the 3 years follow-up, the number of cases which showed radiolucency around the cup 1.5mm or more were 5(38%). and those of correspondant lesions around stem were 6(38%) in 18 cases.
3. Over the 3years follow-up, the number of cases thich showed vertical migration of cup 3mm or more were 3(37%) and the number of cases which showed horizotal migation of cup 3mm or more were 2(11%) in 18 cases.
4. Over the 3 years follo-up, the number of cases which showed vertical migration of femoral steum 5mm or more were 4(22%) in 18 cases.
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