Injectable calcium phosphate cement for augmentation around cancellous bone screws. In vivo biomechanical studies

Abstract

a b s t r a c tIn lower cancellous apparent bone density, it can be difficult to achieve adequate screw fixation and hence stable fracture fixation. Different strategies have been proposed, one of them is through augmentation using calcium phosphate cement in the region at or close to the screw thread itself. To support the hypothesis of an improved screw fixation technique by augmentation of the bone surrounding the implanted screw, in vivo biomechanical and densitometric studies are performed on rabbit specimen where normal and simulated weak bone quality are considered. In particular, the evolution of screw stability till 12 weeks following the implantation is quantified. A statistical significance in the pull out force for augmented versus non-augmented screws was found for the shorter time periods tested of r 5 days whilst the pull out force was found to increase with time for both augmented and non-augmented screws during the 12 week course of the study. The results of the study demonstrate that the use of an injectable calcium phosphate cement which sets in vivo can significantly improve screw pull out strength at and after implantation for normal and simulated weak bone quality.

Heat-shock-induced cellular responses to temperature elevations occurring during orthopaedic cutting

“…Unfavourable outcomes include connective tissue formation around the implant, which can affect the long-term anchorage of the implant by delaying formation of a mature bone interface [5,7,17,18]. To date, the optimal cutting criteria to minimize thermal necrosis and apoptosis and to synergistically enhance tissue regeneration by inducing mineralization are unknown.…”

Variability of the pullout strength of cancellous bone screws with cement augmentation

“…The nature of these results led to a re-examination of data already published (Larsson et al, 2012) for an in vivo animal study. This study has shown the general advantage of using calcium phosphate cement in screw augmentation in animals, but further analysis revealed individual results, at 1, 5 and 10 days, that again contradicted the general result.…”

“…It is generally regarded as beneficial in its use with both cancellous and cortical screws (Gefen, 2002;Gausepohl et al, 2001). Particularly, Larsson et al (2012) have shown that bone augmentation using calcium phosphate cements in a lapine in vivo model gives significantly improved pullout strength. As a result it might be expected that augmentation with cement should always improve fixation, and consequently improve surgical outcome.…”

The relevance of biomaterials to the prevention and treatment of osteoporosis

“…Besides bone augmentation, ceramic cements have also been used for screw augmentation [99][100][101][102]. Some results are very promising [103,104], but more data are needed to assess the long-term success of this approach.…”