Metal On Metal Surface Arthroplasties

THE JOHN CHARNLEY AWARD: A Study of Implant Failure in Metal-on-Metal Surface Arthroplasties.

Clin Orthop Relat Res. 2006 Aug 10

Campbell P,

Beaule PE,

Ebramzadeh E,

Leduff M,

De Smet K,

Lu Z,

Amstutz HC.

The reintroduction of surface arthroplasty of the hip with metal-on-metal bearings has the potential to eliminate or substantially reduce long-term wear-induced osteolysis as the major cause of failure. To determine important modes of failure, implant retrieval analysis was done on 98 failed surface arthroplasty components from different manufacturers. Analysis involved sectioning the components, measuring cement mantle thickness and the depth of penetration, histopathology, and measurement of the bearing wear. A finite element model was constructed to examine cement thermal necrosis. Femoral neck fracture and femoral loosening were the main causes of failure. The finite element model showed thermal necrosis could occur when cysts were filled with cement. Histologic observations verified necrosis of interfacial bone, although adaptive remodeling was commonly seen. The amount of cement varied considerably with implant type, and failure mode and was greater in loosened components. Although implant failure is multifactorial, these observations should be a cause for concern in current cementing techniques in which controlling mantle thickness and extent of penetration may be difficult. Optimizing cement technique to avoid leaving the component proud, and to avoid extensive cementation of the femoral head, may be important in reducing some modes of failure.