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ADVANCED METAL-CERAMIC JOINING TECHNIQUES TO OPTIMIZE LOW-FRICTION KNEE PROSTHESE

Objective


According to the milestones scheduled in the project workprogramme, the following objectives have been achieved:

- a new composite femoral knee prosthesis, made of titanium alloy on the bone interface and with ceramic sliding surfaces, has been designed;
- a new biocompatible brazing alloy, able to join the titanium parts of the knee prosthesis to the ceramic ones, has been developed and its strength well tested;
- some batches of knee prosthesis prototypes have been produced on industrial scale; the following mechanical, fatigue and wear tests performed on them have demonstrated their strength, their long-life characteristics and consequently the validity and the sufficient margin of safety of the product proposed;
- the implantation equipment has been discussed with the surgeons and has been designed and manufactured to fulfill their suggestions and to be used and clinically tested during the first implantation of the AJOP knee prosthesis.
To date the most widely employed materials in orthopaedics have been metals and polymers. Their utilisation however has given rise to a problem: ultra-high-molecular-weight-poly-ethylene (UHMWPE) wear, causing polymeric debris release into surrounding tissues, chronic inflammatory process and consequent prosthesis mobilisation. Due to the unsatisfactory performances of UHMWPE low-friction components in knee implants and owing to the paramount importance to reduce the amount of friction and wear rate the possible use of ceramics has been evaluated. But ceramics are brittle materials, and the tests on femural knee prosthesis components totally made with ceramics have shown its unreliability, owing to mechanical problems. In fact their shape must be very complicated, with variable thicknesses and sharp edges, which easily induce failure due to dynamic or fatigue loads. For this reason, the main objective of the proposed research activity consists in the design, assessment and production of an innovative composite knee prosthesis femural component, whose sliding surface is made with ceramics and the structural part is made with titanium alloys. So doing, two main advantages can be reached, i.e. the UHMWPE wear, erosion and debris release would be roughly halved (and prostheses endurance consequently doubled), while bone re-growth would be enhanced. In particular, the present project intends to develop an advanced active vacuum brazing joining technique for the fabrication of such type of hybrid knee implants. The activity intends to cover the steps related to clinical and mechanical requirement emission: ceramics and powders formulation; vacuum brazing and active fillers development, preliminary prosthesis design; in vitro biocompatibility and mechanical testing on specimens; joining techniques industrialisation; prostheses prototypes definite design, production and assembling; prototypes mechanical testing; prototypes in vivo clinical testing; final production costs analysis and costs/benefits ratio evaluation.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Lima Lto SpA
Address
Via E. Fermi 44
20090 Assago Milano
Italy

Participants (6)

AACHEN UNIVERSITY OF TECHNOLOGY
Germany
Address
Jülicher Str.344a
52056 Aachen
LASINDUSTRIA SA
Portugal
Address
Rua Francisco Antonio Da Silva
2780 Oieras
METSEARCH BV
Netherlands
Address
Reelaan, 11
7522 LR Enschede
Morgan Matroc Ltd
United Kingdom
Address
Central Avenue
KT8 2QZ West Molesey
Sintea Compositi Srl
Italy
Address
Via Burlamacchi 3
20135 Milano
Università Cattolica del Sacro Cuore
Italy
Address
Largo Agostino Gemelli 8
00168 Roma