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The porous-coated anatomic total hip prosthesis: failure of the metal-backed acetabular component
D J Astion1, P Saluan, B N Stulberg
1Hospital for Special Surgery, New York, N.Y. 10021, USA.
Insights
Early porous-coated anatomic acetabular components showed a 12% failure rate due to migration or osteolysis. Design and material factors contributed to the failure of these total hip arthroplasty implants.
Area of Science:
- Orthopedic Surgery
- Biomaterials Science
- Medical Device Engineering
Background:
- The initial design of porous-coated anatomic acetabular components was used in total hip arthroplasty (THA) between 1983 and 1987.
- These components featured a metal-backed polyethylene device with sintered beads for bone ingrowth and pegs for fixation.
Purpose of the Study:
- To evaluate the failure modes and long-term outcomes of the initial porous-coated anatomic acetabular components in THA.
- To identify factors contributing to the failure of these acetabular components.
Main Methods:
- Retrospective review of 199 THAs performed in 173 patients.
- Radiographic analysis to assess osteolysis and component migration.
- Examination of retrieved acetabular components for material and design-related damage.
Main Results:
- A 12% failure rate (23 of 199 components) was observed, attributed to migration or severe osteolysis.
- Osteolysis prevalence correlated positively with implant duration (p < 0.001) and was higher in components with smaller outer diameters (≤55 mm) (p = 0.03).
- Retrieved components showed significant polyethylene damage, including cracks and deformation, suggesting material-related issues.
Conclusions:
- The initial porous-coated anatomic acetabular components demonstrated a notable failure rate.
- Both design flaws and material properties contributed to the observed failures, including osteolysis and component revision.
- Findings highlight the importance of material integrity and design optimization in THA components.
Abstract:
One hundred and ninety-nine total hip arthroplasties were performed, between 1983 and 1987, in 173 patients by three surgeons using the initial design of the porous-coated anatomic prosthesis. The acetabular component was a preassembled, metal-backed polyethylene device, with beads sintered to the metal backing to allow bone ingrowth and two pegs for initial fixation. Twenty-three acetabular components (12 percent) failed because of either migration or severe osteolysis. The radiographic appearance of osteolysis was positively associated with the duration that the implant had been in situ (p < 0.001). The prevalence of osteolysis was also significantly greater in acetabular components with an outer diameter of fifty-five millimeters or less (a polyethylene thickness of 8.5 millimeters or less) (p = 0.03). Thirteen hips were revised at a mean of 69.5 months (range, thirty-three to ninety-one months) after the index operation. Examination of the retrieved acetabular components revealed extensive polyethylene damage on the articular and back surfaces of the liners. Cracks in the polyethylene rim of the liner and deformation of the anti-rotation notch in the polyethylene rim were common findings. The density of the polyethylene was greater than expected, and more particles than anticipated had not fused with the surrounding polyethylene. The results of this study suggest that factors related to both the design and the material contributed to the failure of these porous-coated anatomic acetabular components.