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Low revision rates associated with tapered rectangular hip stem
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Femoral fixation of a cementless total hip arthroplasty using a tapered, rectangular stem made of titanium-aluminum-niobium alloy continues to be secure at 20-years follow-up, according to a recently presented study.
“The most important result of study is the low rate of revisions of the femoral component, with 97% survivorship,” Alexander Kolb, MD, said during his presentation at the 12th EFORT Congress 2011. “The low rate of femoral osteolysis in the medial and distal Gruen zones proves the stability of the osseous integration of the stems at follow up.”
Kolb, of the department of orthopedics and orthopedic surgery at Medical University of Vienna, and colleagues evaluated the stability of the Zweymüller (Zimmer) stem for cementless total hip arthroplasty.
From October 1986 and November 1987, the researchers evaluated 200 patients aged 22 years to 84 years. The group had a mean age of 66 years and 40% were men.
Patient conditions consisted of osteoarthrosis (69%), hip dysplasia (18%), osteonecrosis (5%), post-traumatic arthritis (5%), rheumatoid arthritis (4%), ankylosis (2%), infection (2%) and others (5%), according to Kolb.
During the 20-year follow-up period, 115 patients died and 12 were lost to follow-up, leaving 73 patients. Of the remaining patients, 24 were unable to attend the outpatient clinic. However, they completed the study via standard telephone interview.
Results showed that the probability of survival of the stem with revision for any reason as the end point was 0.97 at 20 years.
Probability of survival of the acetabular component excluding revisions of the polyethylene liner with revision for any reason at the endpoint was 0.88, including the polyethylene liner (0.67). Probability of survival for the stem and acetabular component with revision for any reason as the endpoint was 0.65.
When patients were asked about their experience with the procedure, 87.7% said they were very satisfied or satisfied, 2.8% were rather satisfied or dissatisfied with the outcome of the operation, and 9.6% did not respond.
“We found various degrees of osteolysis and radiolucent lines around the acetabular and proximal femoral component in 61.7% of the patients. We did not find any in the distal femoral zones and no stem was deemed at risk for loosening at the 20-year follow-up mark,” Kolb said.
Reference:
- Kolb A, Chiari C, Kaider A, et al. Cementless total hip arthroplasty with the tapered rectangular titanium Zweymüller stem. A minimum 20-year follow-up. Presented at the 12th EFORT Congress 2011. Copenhagen, Denmark. June 1-4, 2011.