Outcomes of metal-on-metal-backed polyethylene cemented hip replacements: an 11-year prospective study
Lazennec JY*; Boyer P*; Poupon J**; Rousseau MA *; Ravaud P***; Catonné Y*
*Department of Orthopaedic Surgery
La Pitié-Salpétrière hospital Paris
**Laboratory of toxicology
Lariboisière hospital Paris
***Statistic department
Bichat hospital Paris
Background and purpose: The long-term outcomes of cemented metal-on-metal hip arthroplasties have not been studied. The purpose of this study was to evaluate a consecutive series of metal-on-metal polyethylene-backed cemented hip arthroplasties implanted in patients under 60 years of age.
Methods: A mean of 9 years after arthroplasty, 109 patients with a total of 134 joint replacements were followed prospectively. The evaluation included clinical score,radiological assessment, and blood sampling for ion level determination.
Results: At the final review, twelve hips were revised, mainly because of aseptic loosening of the socket. Using revision for aseptic loosening as the end point, the survival rate at 9 years was 91.8% for the cup and 97.7% for the stem. In addition, 35 hips showed radiolucent lines at the bone-cement interface of the acetabulum and some were associated with osteolysis. The median serum cobalt level was relatively constant overtime, and was much higher than the detection limit throughout the study period. The level was 1.5 µg/L one year after implantation, and 1.44 µg/L nine years after implantation.
Interpretation: Revisions for aseptic loosening and radiographic findings in the sockets led us to halt metal-on-metal-backed polyethylene cemented hip arthroplasty procedures. In addition to constraints at the bone-cement interface, excessive metal ion and particle release may have contributed to cup failure. Further investigation is required to confirm this hypothesis and to determine whether subluxation, microseparation, and hypersensitivity also play a role.
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