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Cementless hemispheric porous-coated sockets implanted with press-fit technique without screws: average ten-year
Pacharapol Udomkiat1, Lawrence D Dorr, Zhinian Wan
1Orthopaedic Research Institute at Good Samaritan Hospital, Los Angeles, CA, USA.
Background:
Press-fit implantation of a porous-coated hemispheric acetabular component without screws is an option for primary total hip replacement. The purpose of the present study was to evaluate the results of this technique after an average duration of follow-up of ten years to determine if there was any loss of fixation or increase in osteolysis over time.
Methods:
From June 1988 to November 1990, 132 primary total hip replacements were performed with a porous-coated socket that was implanted with use of a press-fit technique. Twenty-two hips were excluded because the patient had died or had been lost to follow-up, leaving 110 hips (103 patients) available for inclusion in the study after an average duration of follow-up of 10.2 +/- 1.0 years. The average age of the patients at the time of operation was 60.7 years (range, 23.7 to 86.2 years). Radiographs were evaluated with regard to initial gaps, radiolucent lines, migration, polyethylene wear, and osteolysis. Kaplan-Meier survivorship analysis was performed to calculate the rate of survival of the acetabular component.
Results:
One hip (0.9%) had revision of the socket because of aseptic loosening, and four hips (4%) had revision of a stable socket. With the numbers available, the presence of gaps on the initial postoperative radiographs was not associated with the occurrence of radiolucent lines (p = 0.039). Pelvic osteolysis was seen in four hips, with an average time to radiographic appearance of six years. Increased wear was directly related to an abduction angle of >40 degrees. The twelve-year survival rate was 99.1% with revision because of failure of fixation of the metal shell as the end point, 95.3% with revision for any reason as the end point, and 79.6% with exchange of the liner as the end point.
Conclusions:
The fixation of this press-fit socket did not deteriorate over time and was associated with a low rate of osteolysis. The most common reasons for reoperation were wear and dissociation of the polyethylene insert.