The association of bone morphogenetic proteins (BMPs) with calcium phosphate bioceramics is known to confer them osteoinductive properties. The aim of this study was to evaluate the surface properties, especially regarding recombinant human BMP-2 (rhBMP-2) adsorption and release, of commercial sintered biphasic calcium phosphate ceramics after coating with biomimetic nanocrystalline apatite. The raw and coated ceramics exhibited similar macroporous structures but different nanometer-sized pores contents. Both types of ceramics showed Langmuir-type adsorption isotherms of rhBMP-2. The coating noticeably increased the rate of adsorption and the total amount of growth factor taken up, but the maximum coverage per surface area unit as well as the affinity constant appeared lower for coated ceramics compared with raw ceramic surfaces. The limited advantage gained by coating the ceramics can be assigned to a lower accessibility of the surface adsorption sites compared with the raw ceramics. The quantity of rhBMP-2 spontaneously released in cell culture medium during the first weeks was lower for coated samples than for uncoated ceramics and represented a minor fraction of the total adsorbed amount. In conclusion, the nanocrystalline apatite coating was found to favor the adsorption of rhBMP-2 while providing a mean to fine tune the release of the growth factor.

The quality of the fixation orthopaedic implant to its surrounding bone determines its clinical longevity. Up to 20% of hip replacement operations are currently revisions for aseptic loosening. While this fixation quality is determined primarily by the bone and tissue anchoring the implant, conditions influencing bone growth in the early post-operative period include the surgical technique and coupled mechanical and biochemical factors. The aim of the study was to propose an original mechano-biological formulation of the healing process of periprosthetic tissue. The multiphasic porous model involved the solid osseous matrix, the extracellular fluid phase, the osteoblastic cellular phase responsible from the bone formation and the growth factor phase promoting the cellular activity. To derive the non-linear convective-diffuse governing equations, mass balance was associated to cell active haptotactic and chemotactic migration, growth factor diffusion, cell proliferation (logistic law) and bone formation (reactive medium). The in-vivo application concerned a canine axisymmetric implant which was stable and mechanically unloaded. Predictive numerical results were compared to ex-vivo data from a histologic study. The generic healing pattern involving two main oscillations of the radial bone formation was well predicted. In the future, the model could assist in evaluating the role of growth factor concentrations and their temporal delivering as far as the role of pertinent sources such as bioactive coating or additional biomaterials.

The biomechanical properties of each potential ALL graft can be factored in when deciding which type of graft to use.

A Finite Element model of the face soft tissue is proposed to simulate the morphological outcomes of maxillofacial surgery. Three modelling options are implemented: a linear elastic model with small and large deformation hypothesis, and an hyperelastic Mooney-Rivlin model. An evaluation procedure based on a qualitative and quantitative comparison of the simulations with a post-operative CT scan is detailed. It is then applied to one clinical case to evaluate the differences between the three models, and with the actual patient morphology. First results shows in particular that for a "simple" clinical procedure where stress is less than 20%, a linear model seams sufficient for a correct modelling.

There are no published studies describing the strength quadrupled gracilis tendon alone and quadrupled semitendinosus tendon alone in the configuration used for anterior cruciate ligament (ACL) reconstruction. The primary objective was to compare the mechanical properties of grafts used for ACL reconstruction during a tensile failure test. The secondary objective was to evaluate the effect of uniform suturing on graft strength. Fifteen pairs of knees were used. The mechanical properties of five types of ACL grafts were evaluated: patellar tendon (PT), sutured patellar tendon (sPT), both hamstring tendons (GST4), quadrupled semitendinosus (ST4), and quadrupled gracilis (G4). Validated methods were used to perform the tensile tests to failure and to record the results. Student's t-test was used to compare the various samples. The maximum load to failure was 630.8N (AE 239.1) for the ST4, 473.5N (AE 176.9) for the GST4, 413.3N (AE 120.4) for the sPT, and 416.4N (AE 187.7) for the G4 construct. Only the ST4 had a significantly higher failure load than the other grafts. The sPT had a higher failure load than the PT. The ST4 construct had the highest maximum load to failure of all the ACL graft types in the testing performed here. Uniform suturing of the grafts improved their ability to withstand tensile loading. Keywords: biomechanical; graft; ACL; knee The choice of grafts for anterior cruciate ligament (ACL) reconstruction is not without consequences. One of the advantages of using the hamstring tendonsgracilis (G) and semitendinosus (ST)-is that harvesting these tendons leads to lower morbidity than harvesting a bone-patellar tendon-bone graft. Use of the these tendons provides sufficient strength, limits extensor mechanism weakening and lessens anterior knee pain. 1-7 However, harvesting the G and ST reduces flexion strength and control over internal rotation. 8,9 Recent studies have shown the ST alone can be used as a graft. [10][11][12] However, the ST muscletendon unit controls knee rotation in full extension. 13 Using the gracilis tendon only should reduce the morbidity induced by harvesting both hamstring tendons and preserve the semitendinosus.Zamarra et al. 14 evaluated the potential of using quadrupled gracilis alone or tripled semitendinosus alone to reconstruct the ACL. Authors demonstrated that semitendinosus or gracilis tendon for ACL reconstruction could satisfactorily restore knee kinematics and the in situ forces to those for the intact ACL. Nonetheless, Abramowitch et al, demonstrated differences between the semitendinosus and gracilis tendons in terms of their quasi-static mechanical and non-linear viscoelastic properties. 15 These results were not unexpected given that Kilger et al, in a biomechanical cadaveric study had already showed that gracilis has a higher modulus than the semi tendinosus. 16 Among those studies, several others studies have reported on the strength of each individual tendon [17][18][19] but none has determined graft strength in the configuration used for ACL reco...

The results from this animal study showed that the central zone of the vertebral endplate was more permeable than the periphery and the flow-out permeability was up to 35% greater than the flow-in permeability. Increase of permeability with decrease of cartilage thickness was noticed within the same age group. We also found a statistically significant decrease of the macroscopic permeability correlated with the tissue maturity.

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