Effect of a ß-TCP collagen composite bone substitute on healing of drilled bone voids in the distal femoral condyle of rabbits.

In this study, we tested the performance and biocompatibility of a composite of ß-tricalcium phosphate (ß-TCP) to collagen as a bone void filler (Cerasorb(®) Ortho Foam) in a rabbit distal femoral condyle model. ß-TCP is a completely resorbable synthetic calcium phosphate and the addition of a collagen matrix couples the osteoconductive effects of the two components. Furthermore, the malleable properties of the implant material during surgical applications for shape control will be enhanced. A critical size defect of 6 mm in diameter and 10 mm in depth was drilled into each distal femur of the rabbits. One hole was filled with the test substance and the other was left empty for control. After 1, 3, and 6 months the animals were killed and the degree of bone healing analyzed. In total, 18 animals were investigated. When the ß-TCP composite was used, histological, histomorphometric, and biomechanical evaluations revealed significantly better bone healing in terms of quantity and quality of the newly formed bone. Moreover, no signs of inflammation were observed in the animals and no allergic or foreign body reaction was noted. This suggests high biocompatibility and osteoconductivity of the investigated material to a bone void in an immune responsive species.

Augmentation of intertransverse process lumbar fusion.

Spinal fusion surgery for alleviation of intractable lower back pain in humans is currently a primary therapeutic technique, with failure rates averaging between 5 to 35%. Implanted and external source-based electrical stimulation devices have been investigated in an attempt to increase osteogenesis at the fusion site in an attempt to reduce spinal fusion failure rates. The purpose of our study was to evaluate the efficacy of two co-processor systems and an additional system with an SIS generation field at 15.8 mA (rms) using biomechanical, dual-energy X-ray absorptiometry (DXA), and histomorphometric analyses, in rabbits following dorsolateral (= posteriolateral [in humans]) spinal fusion. Fifty-six male New Zealand White underwent bilateral lumbar spinal fusion by performing decortication of the transverse processes of lumbar vertebrae four and five with placement of autogenic cancellous bone graft harvested from the ilial wings. Four study groups were designated based on the type of IES device used for stimulation or as a control. Eight weeks after surgery all subjects were sacrificed and the quality and strength of the fusion masses were compared using radiographic, biomechanical, histomorphometry, and qualitative histological evaluation. While some variation existed within and between groups, Group 2 showed a significant improvement in all parameters measured as compared to the control group (P < 0.05). The use of adjunct non-invasive surface IES for improving bony fusion rates for patients undergoing lumbar spinal fusion is supported by this study.