Failure of a metal-on-metal total hip arthroplasty from progressive osteolysis

Abstract: Uhra-high-molecular weight polyethylene (UHMWPE) wear, debrisinduced osteolysis is a frequent cause of failure of total hip arthroplasty. Metal-onmetal total hip arthroplasty eliminates the generation of UHMWPE particulate debris. Although the volumetric wear of a metal-on-metal articulation may be lower than a metal-UHMWPE articulation, the number of particles may be higher. Osteolysis can deve|op in response to metallic and UHMWPE debris. The following case of massive osteolysis associated with large amounts of cobalt-chrome wear debris shows adhesive and abrasive wear mechanisms, as well as wear caused by third-body cobalt-chrome debris and impingement of the femoral component against the rim of the acetabular cup, which led to failure of a metal-on-metal total hip arthroplasty. Key words: wear, metal, hip, arthroplasty, cobalt-chrome. Polyethylene wear and osteolysis can limit the longevity of total hip arthroplasty (THA). It has been suggested that metal-on-metal articulations may generate less wear and perform more favorably than metal-on-polyethylene articulations Case Report A 76-year-old man complained of left hip pain i4 years after THA with a Sivash metal-on-metal prosthesis (Joint Medical Products, Port Washington, NY) 87

Fatigue fracture of a cemented Omnifit CoCr femoral stem: implant and failure analysis

A cemented, cast CoCr alloy, Omnifit Plus femoral stem was retrieved following mid-stem fracture after 24 years in vivo. The patient was an active 55-year-old male with a high body mass index (31.3) and no traumatic incidents before stem fracture. Fractographic and fatigue-based failure analyses were performed to illuminate the etiology of fracture and retrospectively predict the device lifetime. The fracture surfaces show evidence of a coarse grain microstructure, intergranular fracture, and regions of porosity. The failure analysis suggests that stems with similar metallurgical characteristics, biomechanical environments, and in vivo durations may be abutting their functioning lifetimes, raising the possibility of an increased revision burden. Keywords: Fatigue fracture, Total hip arthroplasty, Stem fractur