Metallurgy of the ReCap Hip Resurfacing System

Biomet has been designing and manufacturing modern metal on metal hip articulations since 1995.

Metal on metal articulations provide extremely low wear rates and avoid the problems caused by polyethylene debris generated in metal - UHMWPE articulations.

The ReCap femoral resurfacing head and acetabular components are made from “as cast” cobalt chrome. Recap ‘as-cast’ CoCrMo has a high carbon content (>0.2%). It consists of large carbides particles embedded in a softer metal matrix. Large carbides volume fractions have abrasive wear resistance properties. They reinforce and protect the softer metal matrix.

                              

Depending upon the CoCrMo manufacturing processes, the level or carbides will vary. Post cast thermal treatments reduce carbide size and their distribution within the material. Post cast thermal processes are: Hot isostatic pressing (HIP), Solution heat treatment (HT), Wrought Forging metallurgy, Sintering.

No subsequent heat treatment of the ReCap/M2a-Magnum device takes place; therefore it remains a true ‘as-cast’ device, retaining the high carbide content qualities.

     

                 “As-Cast”                                                “Cast+HT”

Recent work has shown that “As-cast” CoCrMo provide superior wear resistance.

“As-cast materials were determined to have greater abrasive wear resistance when compared to single or multiple heat treated materials.”

"A Tribological study of CoCrMo alloys used in metal-on-metal resurfacing hip arthroplasty,"
J. Cawley, J.E.P. Metcalf, A.H. Jones, T.J. Band and D.S. Skupien, Wear 255 (2003), 999-1006
 

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