Joint endoprosthesis with Al2 O3 ceramic head and a composite socket and process for making it

Claim 1

A process for manufacturing a joint endoprosthesis having an Al 2 O 3 ceramic head and a composite socket comprising the steps: (a) fusing an inorganic mixture of a first component mixture and a second component to form a ceramic, glass ceramic or sintered glass ceramic material having apatite and/or wollastonite crystal phases, wherein the first component mixture comprises, in percent by mass of the first component mixture, ______________________________________ 31-34% CaO 10-12% P.sub.2 O.sub.5 43-46% SiO.sub.2 3-5% Na.sub.2 O 2-3.5% MgO 3-5% CaF.sub.2 ______________________________________ and the second component comprises 0.5 to 11%, relative to the mass of the first component mixture, of a compound selected from the group consisting of Al 2 O 3 , ZrO 2 , TiO 2 and mixtures thereof, with the proviso that TiO 2 be present in the inorganic mixture at no more than 5% of the first component mixture; (b) cooling and comminuting the ceramic material such that the comminuted ceramic material has a grain size distribution of: ______________________________________ 200-500 microns less than 10% 160-200 microns 15 to 25% 125-160 microns 40 to 50% 100-125 microns 20 to 30% less than 100 microns less than 20% less than 10 microns less than 0.1%; ______________________________________ (c) introducing the comminuted ceramic material into a polymeric matrix comprising polyurethane or an epoxy resin to prepare a composite of ceramic material and matrix; (d) curing the composite resulting from step (c) to provide a composite socket; and (e) combining the composite socket with an Al 2 O 3 ceramic head such that the difference between the radius of the socket and the radius of the head lies within the range of 25 to 350 microns, and the radius of the socket and the radius of the head deviate from an ideal spherical shape by 30 microns or less.