Femoral Head Penetration Rate Research Articles

Long-term results of uncemented acetabular cups with an ACS polyethylene liner. A 14–16-year follow-up study

We assessed the clinical and radiographic results of 40 porous-coated acetabular cups with an Acetabular Cup System polyethylene liner over a minimum 14-year follow-up. Femoral head penetration was estimated using a software package. Fifteen cups were revised, 11 due to polyethylene liner rupture. All cups but two were radiographically stable, and 11 hips showed acetabular osteolysis. The overall femoral head penetration rate in hips without liner fracture with reference to the early penetration point was 0.1188+/-0.070 mm per year. Polyethylene liner fractures were associated with higher early femoral head penetration (P<0.0001) and a vertical cup position (P=0.0016). The 14-year survival without cup revision for any reason was 63.9%, 71.8% with no ACS polyethylene liner fracture and 65.3% with no acetabular osteolysis. Most cups showed a good clinical outcome in general, but major Acetabular Cup System liner failure and osteolysis were frequent. Patients with the ACS cups still in place should be monitored closely.

Five-year Experience with Crossfire?? Highly Cross-linked Polyethylene

Our purpose was to compare the clinical wear performance of highly cross-linked (Crossfire) polyethylene with conventional (N2Vac) polyethylene total hip bearings. We implanted 56 hips (47 patients) with Crossfire acetabular bearing liners and compared their wear performance with 53 conventional polyethylene inserts. Wear and clinical data were collected retrospectively at a minimum 4-year and average 5-year followup. The linear femoral head penetration rate measured from plain radiographs was 0.055 mm/year +/- 0.022 mm/year for the Crossfire polyethylene and 0.138 mm/year +/- 0.073 mm/year for the control, a reduction of 60% for the Crossfire components. Calculated annual wear was 0.036 mm/year for the Crossfire components and 0.131 mm/year for the controls, a reduction of 72%. Radiographic review at most recent followup showed a reduction in erosive osteolytic lesions of the proximal femur for the Crossfire components compared with controls, also suggesting a reduction in debris release for the Crossfire components. Complications leading to revision were not seen in the Crossfire or control groups. These clinical findings suggest that this particular highly cross-linked polyethylene can provide wear reduction and an alternate bearing surface for active patient populations. Therapeutic study, Level III (retrospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.

Early Femoral Head Penetration of a Highly Cross-Linked Polyethylene Liner vs a Conventional Polyethylene Liner: A Case-Controlled Study

Forty highly cross-linked, polyethylene-liner primary total hip arthroplasties were matched by sex, age, and body mass index with 40 conventional polyethylene primary total hip arthroplasties to compare femoral head penetration rates. Both inserts were 10° liners manufactured by the same company and packaged in a nitrogen/vacuum atmosphere. Identical acetabular components and a 28-mm cobalt chrome femoral head were used in all cases. The mean femoral head penetration rate for the highly cross-linked and conventional polyethylene was 0.05 (range, 0.01-0.09) and 0.12 (range, 0.02-0.29) mm/y, respectively, a 58.33% reduction in femoral head penetration ( P < .001). In this short-term follow-up study (mean, 47.73 months), both reduced “bedding-in” and reduced wear may contribute to the observed decrease in femoral head penetration.

Comparison of femoral head penetration rates between cementless acetabular components with 22-mm and 28-mm heads

Between April 1993 and July 1994, the senior author (R.C.J.) performed 151 consecutive primary total hip arthroplasties using a Harris-Galante II acetabular component and a polished Iowa femoral component. In 105 hips, 22-mm head components were used, and in 46 hips, 28-mm head components were used. Femoral head penetration into the acetabular shell was measured using digital edge detection techniques. The group average penetration for the initial 2-year bedding-in period was 0.35 mm/y for the 22-mm and 0.31 mm/y for the 28-mm head components. The long-term rate of penetration into the shell was 0.11 mm/y for the 22-mm heads and 0.17 mm/y for the 28-mm heads, a significant difference (P=.029). The dislocation rate was significantly higher, however, with the 22-mm heads (P=.001). The 22-mm components showed significantly less wear but at the expense of an increase in the prevalence of dislocation.