L. Sedel et al., BIOMATERIALS ORTHOPEDIC APPLICATION PRECL INICAL AND CLINICAL-EVALUATION, Bulletin de l'Academie nationale de medecine, 179(3), 1995, pp. 497-506
It is very challenging to insure long term security and effectiveness
for joint arthroplasties, artificial ligaments, extensive bone replace
ment and some other orthopaedic biomaterials. How can we predict the l
ong term security and efficacy of such an implant ? Only an interdisci
plinary approach can provide a satisfactory answer. The surgeon must d
efine the needs, he must find the appropriate surgical techniques and
conduct the clinical trial. The material scientist must elaborate safe
and secure materials with regards to their biotolerance and mechanica
l resistance. This has to be performed in close connection with the bi
omechanics lab. Biomechanic Science must predict the expected stresses
. It has to design special simulator to quantify in vitro material tou
ghness, wear characteristics, lubrication, behaviour and surface defor
mation. Biological and mechanical standardized tests have to be carrie
d on. Then it is possible to conduct a clinical trial, prospectively i
n comparison to another already developed material. Clinical studies c
ould serve to measure efficacy and radiological modification. After fa
ilure, it is possible to analyse retrieved specimen, to measure the ma
terial degradation in real environment, to perform biological studies
on retrieved tissues ie : macrophagic activities, tissue response, bon
e ingrowth, inflammatory or immulogical reaction. For more than twenty
years we worked on alumina against alumina total hips. The idea was t
o develop a low debris system to enhance long term longevity of the pr
osthesis. The Charnley design has proven its effectiveness for more th
an fifteen years, but polyethylene wear is responsible for late failur
es. This is specially crucial for young patients, male sex and high ac
tivity level patients. At the beginning, biological studies and mechan
ical tests were performed, it appeared that the biological tolerance o
f alumina ceramic was excellent, the fracture thoughness was adequate,
but there were some problems related to alumina fixation in the body
and also alumina head fixation on metallic stem. Alumina material impr
oved with time. It was possible to diminish the fracture risks and to
increase the safety. Parallel information from the first period was us
ed to increase the material quality, the surgical techniques and also
to define indication in the use of such material. It is now clear and
it also has been published that alumina against alumina system has pro
ved to be as safe as Charnley total hips. It has been proved to give b
etter results in the young age population. Then it is now possible to
operate on very young patients, to allow these patients to perform hea
vy work, sports and regular daily activity for their demand. In conclu
sion, long terme evaluation of orthopaedic implants has to be carried
on with very scientific bases. Prospective tests must mimic a in-livin
g system, but the clinical trial is the only way to really get the ans
wer for the very long term.