Papers by Author: Ronan Cognet

Abstract: The aim of this study was to evaluate the capacity of the association of calcium phosphate cement with collagen membrane for large segmental bone defect. Six adult beagle dog underwent defect creation in the ulna and was reconstructed with combination of macroporous calcium phosphate cement MCPC® and resorbable collagen membrane EZ Cure®. After 6 months of implantation, the samples were analyzed with Micro CT, light microscopy and SEM using BSE. Bridging of the defect with a lamellar and well organized bone was achieved in all animals. MCPC granules resorption was increased at the extremities of the implant. Collagen membrane at the expense of the implant was replaced by periosteum-like formation. The results demonstrate the ability of the composite to reconstruct large segmental and critical size defect in long bone.

Abstract: Surface roughness modulates the osseointegration of orthopaedic and dental titanium implants. High surface roughness is currently obtained by blasting of titanium implants with silica or aluminium abrasive particles. This process includes into the surface abrasive particles and may cause the release of cytotoxic silica or aluminium ions in the peri implant tissue. To overcome this drawback, we currently develop an innovative gridblasting process using Biphasic Calcium Phosphate (BCP) particles (RBBM Resorbable and Biocompatible Blast Media) to generate biocompatible roughened titanium surface. This work present the technique of blasting using RBBM particles to provide a roughened surface which does not release cytotoxic elements and (ii) to assess the effects of such a roughened surface for bone osteointegration in critical size rabbit defect. Our results demonstrate that resorbable biphasic calcium phosphate abrasive particles can be used to create titanium surface roughness. This grid blasting process increases surface roughness of titanium implants and offers a non cytotoxic surface for rapid and efficient osteointegration.

Abstract: The aim of this study was to study bone marrow quality from various location and species for reconstruction of segmental critical size defect in irradiated weigh bearing bone. Sample of bone marrow aspirates from rabbits and Beagle dog were analyzed. Rabbits were implanted with a composite associating resorbable collagen membrane plus micro macroporous biphasic calcium phosphate (MBCP®) and autologous bone marrow (BM) injected after irradiation. Bone marrow samples were found to be significantly less rich in tibia than in humerus and ilium in Dog and less rich in Dog than in Rabbit (p<0,05). Successful osseous colonization bridging of the defect were obtain at 16 weeks in all animals. Identical repartition of bone ingrowth and residual ceramic at the different levels of the implant suggest an osteoinduction role of the bone marrow graft in the center of the defect. This model succeeded in reconstruct a large segmental defect in weight bearing and irradiated bone in rabbit.

Abstract: We have performed and evaluated a composite combining PL DLLA and PCa able to have a better control of the hydrolysis and maintain of the mechanical property on time, until wound healing was achieved. Bioabsorbable osteoconductive composite is devoted to the development of resorbable osteosynthesis for spine and osteoarticular surgeries. Such resorbable osteosynthesis will be associated to new bone substitute having high osteogenic property but without initial mechanical property. The purpose of this study was to evaluate the resorption kinetic of a composite using PL DLLA (Poly [L-Lactide-co-D,L-Lactide] acide) charged with PCa granules and the interaction with injectable bioceramic without self hardening. MBCP gel® is a composite associating a mineral phase of an intimate nanoscale melting of hydroxyapatite and beta tri calcium phosphate and an aqueous phase containing a synthetic polymer derived from cellulose HPMC (hydroxyl propyl methyl cellulose).

Abstract: Resorbable osteosynthesis based on PLLA and derivatives will be associated to bone substitute for bone reconstruction. We have performed rand evaluated a composite combining PL DLLA and Biphasic calcium phosphate able to have a), a better controlled hydrolysis in the purpose to preserve on time the mechanical property, and b), for long term efficiency, bone ingrowth at the expense of the osteosynthesis and the associated bone substitute. A new calcium phosphate cement MCPC® was tested with such composite. The novel macroporous calcium phosphate cement MCPC sets to poorly crystalline apatite after mixing the powder component and an aqueous solution. Interconnective macroporosity was induced on time by resorption of one part of the MCPC®. The multiphasic calcium phosphate components in the cement, are resorbed at different rates allowing the replacement by newly formed bone. This study reports the biocompatibility and the interactions of a composite using PL DLLA (Poly [L-Lactide-co-D,L-Lactide] acid) charged with biphasic calcium phosphate granules and a self setting calcium phosphate cement of new generation.

Abstract: We performed vertebroplasty on goat model by injecting a new macroporous calcium phosphate cement MCPC®. The mechanical property of the cement is about 12MPa after 24 hours (compression test). The cement matrix is totally transformed into poorly crystallized apatite in 48 hours. This study demonstrates that MCPC cement was suitable and efficient for a spine application. Its injectability allows to be used in mini invasive surgery and its mechanical properties are compatible to support spine strength. In addition, a bone ingrowth onto the BCP granules occurred with time.