Sammendrag
Background: Complications with metal-on-metal (MoM) hip arthroplasties have been known for several years. Increased cobalt and chromium levels and soft-tissue reactions known as pseudotumors have been revealed in an increasing amount of patients with MoM hip arthroplasties. Pseudotumors damage both soft-tissue and bone surrounding the prosthesis. We have followed a group of patients with MoM hip resurfacing arthroplasties in Norway to reveal complications and treat these adequatelly. Material and method: 36 patients (27 men) after MoM resurfacing hip arthroplasties were examined for hip function and whole-blood levels of cobalt and chromium at a mean of 4 and 5,4 years after surgery. Hip function were assessed with Harris Hip Score, UCLA Activity Score and Hip disability and Osteoarthritis Outcome Score. 19 patients were examined using MARS-MRI. Results: No significant reduction in hip function was found in the group with complications. Women had significantly higher levels of cobalt (p=0,030) and chromium (p=0,037). Four patients had pseudotumors (3 women) and the incidense was higher in women (p=0,011). Pseudotumors were also associated with increased levels of cobalt (p=0,026) and chromium (p=0,019) at 5,4 years. Formation of pseudotumors correlated with smaller femoral components (r=-0,520; p=0,016). Five patients were revised giving a cumulative survival rate of 92,9% and 82,6% at five and eight years. Conclusion: The functional outcome of MoM hip resurfacing is generally good, but does not justify the risk of severe complications. Regular postoperative observation of patients with MoM articulations is necessary because of pseudotumores without symptoms. Comparable clinical results have been shown in recent studies with alternative articulations eliminating the risk of adverse effects caused by metal particles. We therefore do not recommend to continue MoM resurfacing as standard treatment for primary arthritis.
Background: Complications with metal-on-metal (MoM) hip arthroplasties have been known for several years. Increased cobalt and chromium levels and soft-tissue reactions known as pseudotumors have been revealed in an increasing amount of patients with MoM hip arthroplasties. Pseudotumors damage both soft-tissue and bone surrounding the prosthesis. We have followed a group of patients with MoM hip resurfacing arthroplasties in Norway to reveal complications and treat these adequatelly. Material and method: 36 patients (27 men) after MoM resurfacing hip arthroplasties were examined for hip function and whole-blood levels of cobalt and chromium at a mean of 4 and 5,4 years after surgery. Hip function were assessed with Harris Hip Score, UCLA Activity Score and Hip disability and Osteoarthritis Outcome Score. 19 patients were examined using MARS-MRI. Results: No significant reduction in hip function was found in the group with complications. Women had significantly higher levels of cobalt (p=0,030) and chromium (p=0,037). Four patients had pseudotumors (3 women) and the incidense was higher in women (p=0,011). Pseudotumors were also associated with increased levels of cobalt (p=0,026) and chromium (p=0,019) at 5,4 years. Formation of pseudotumors correlated with smaller femoral components (r=-0,520; p=0,016). Five patients were revised giving a cumulative survival rate of 92,9% and 82,6% at five and eight years. Conclusion: The functional outcome of MoM hip resurfacing is generally good, but does not justify the risk of severe complications. Regular postoperative observation of patients with MoM articulations is necessary because of pseudotumores without symptoms. Comparable clinical results have been shown in recent studies with alternative articulations eliminating the risk of adverse effects caused by metal particles. We therefore do not recommend to continue MoM resurfacing as standard treatment for primary arthritis.