Today's News

Saturday, February 15, 1997

New hip cementing techniques do not stop aseptic failure

Cemented total hip arthroplasty (THA) provides predictable pain relief, improvement in function and outstanding survival for at least 10 years to middle-aged patients with osteoarthritis. However, rates of aseptic failure of both femoral and acetabular components increase between 10 and 15 years despite the use of improved cementing techniques.

Between 1978 and 1985, 76 patients between the ages of 40 and 60 years (median age: 36) with primary or secondary coxarthrosis and who underwent THA were studied. The two main diagnoses were primary osteoarthrosis, 67.8 percent and developmental dysplasia of the hip, 20.8 percent.

All of the 88 hips treated received implants with a rounded rectangular cross section and medial collar. Cemented acetabular components were used (15 metal-backed and 73 all polyethylene). Femoral head sizes ranged from 22 to 32 millimeters.

After initial post operative follow-up, patients were followed for one to 15 years. Data was collected from questionnaires, radiographs and hip scores.

The study, presented Friday in scientific paper 238 by Michael P. Muldoon, MD, lieutenant commander of the Naval Medical Center, San Diego, Calif., demonstrated excellent durability of the prosthesis at 10 years-94.5 percent of the patients did not require revision due to aseptic loosening

"We found that loosening occurred more frequently with acetabular rather than femoral components on young patients during the first 10 years, however the durability of both components appears to reduce more rapidly than expected in the second decade of service," Dr. Muldoon said.

"The majority of femoral and acetabular revisions in our series occurred between 10 and 15 years," Dr. Muldoon said. "Increased radiographic loosening rates of both components also were noted after 10 years. However, the number of patients with radiographic and clinical follow-up after 10 years is not sufficient enough to statistically validate these observations."

The quality of cement mantle of the femoral components was the most critical identifiable factor in early survivorship and was associated with all early femoral failures. Failures after 10 years however, were not limited to those with unsatisfactory cement technique.

The diagnosis of dysplasia versus primary osteoarthritis was statistically related to increased incidence of clinical and radiographic failure of the acetabular component.

"The middle-aged population of patients with hip osteoarthrosis makes up approximately 15 to 20 percent of the patients treated at our clinic, so we are concerned that cases of aseptic loosening causing femoral failure will approach 20 percent by the 15-year mark, despite our use of contemporary cement techniques," Dr. Muldoon said. "Our study shows us that middle-aged patients with coxarthrosis should continue to be cautioned about component survivability in preoperative counseling sessions."

Co-authors of the study are W. Scott Harmsen, MS, consultant in orthopaedic surgery at the Mayo Clinic and assistant professor of orthopaedic surgery at the Mayo Medical School, as well as Daniel J. Berry, MD, statistician, Mayo Clinic, both in Rochester, Minn.