Elsie Damien

A comparative study on the in vivo behavior of hydroxyapatite and silicon substituted hydroxyapatite granules

Phase pure hydroxyapatite (HA) and a 0.8 wt % silicon substituted hydroxyapatite (SiHA) were prepared by aqueous precipitation methods. Both HA and SiHA were processed into granules 0.5–1.0 mm in diameter and sintered at 1200 °C for 2 h. The sintered granules underwent full structural characterization, prior to implantation into the femoral condyle of New Zealand White rabbits for a period of 23 days. The results show that both the HA and SiHA granules were well accepted by the host tissue, with no presence of any inflammatory cells. New bone formation was observed directly on the surfaces and in the spaces between both HA and SiHA granular implants. The quantitative histomorphometry results indicate that the percentage of bone ingrowth for SiHA (37.5%±5.9) was significantly greater than that for phase pure HA (22.0%±6.5), in addition the percentage of bone/implant coverage was significantly greater for SiHA (59.8%±7.3) compared to HA (47.1%±3.6). These findings indicate that the early in vivo bioactivity of hydroxyapatite was significantly improved with the incorporation of silicate ions into the HA structure, making SiHA an attractive alternative to conventional HA materials for use as bone substitute ceramics.

Changes in distant organs in response to local osteogenic growth factors delivered by intraosseous implants: a histological evaluation

Osteogenic growth factors are added to enhance osteointegration and os teogenesis of synthetic bone substitutes to improve clinical outcome. Reactions to par ticles of wear debris from implanted material could lead to bone resorption similar to resorption around a total joint prosthesis and also to inflammatory responses in distant organs. Porous hydroxyapati te (HA) scaffolds pretreated with insulin like growth factor (IGF) -I (0.5 (LD) or 3.0 (HD) μg/implant) and IGF-II (0.5 μg/implant) were implanted in vivo in rabbit femur to enhance their bioactivity and bone bonding properties. Heart, kidney, liver, lung, lymph nodes and spleen were collect ed during systematic postmortem examination at 1, 3 and 5 weeks postimplantation for quantitati ve and qualitative analysis. Local wound healing of the periprosthetic bone and the responses in th distant internal organs were characterised using light microscopy and electron microscopy. All tissues from implanted groups except heart and kidneys exhibited an increase in the cellularity at week 1 and 3. In the lung, there was also evidence of lympho-proliferation and aggregation in the IGF groups and presence of exudates in the IGF-1 HD group. The hypertrophy and hyperplasia appeared to be growth factor, dose and time dependent with IGF-1 LD <IG F-II <IGF-1 HD. At 5 weeks the tissues appeared as regenerated to the normal level wi th regression of the lymphocytic infiltration. We report for the first time, that local delivery of IGF-I and -II by intraosseous HA implant to enhance osteointegration produced no adverse persistent effect s in important internal organs.

In Vivo Characterisation of a Novel Hydrophilic Composite for Total Intervertebral Disc Substitution

Intervertebral disc (IVD) damage due to degeneration, trauma or inflammation is the main cause for lower back pain leading to morbidity and loss of function of the spinal column. Until recently the state of the art treatment for degenerative disc disease (DDD) was arthrodesis. Developments in vertebral arthroplasty enable degenerated disc to be replaced with prosthetic IVD devices while maintaining motion at the affected part. The ability of the intervertebral device to support the in vivo loading environment is critical for the clinical success of such devices. However, such properties are depended on the location and structure of IVD, as the mechanical properties of IVD change locally [1]. The objective of this study was to evaluate the in vivo tissue compatibility of a novel composite, made with poly 2-hydroxyethyl methacrylate (pHEMA), poly ε-caprolactone (PCL) and poly ethylene terephthalate (PET) in an animal model. In vivo qualitative and quantitative results at 6 weeks post intraosseous implantation in rabbit femur revealed that this hydrogel, in contact with bone tissue, showed no tissue damage at the implant-bone interface. This novel composite disc prosthetic material is biocompatible as bone growth was observed into the implant and there was no evidence of toxicity to bone or inflammatory responses at the peri-implant tissue.