Composition dependent mechanical behaviour of S53P4 bioactive glass putty for bone defect grafting.

To improve the handling properties of S53P4 bioactive glass granules for clinical applications, bioactive glass putty formulations were developed. These formulations contain both granules and a synthetic binder to form an injectable material that is easy to shape. To explore its applicability in load-bearing bone defect grafting, the relation between the putty composition and its mechanical behaviour was assessed in this study. Five putty formulations with variations in synthetic binder and granule content were mechanically tested in confined compression. The results showed that the impaction strains significantly decreased and the residual strains significantly increased with an increasing binder content. The stiffness of all tested formulations was found to be in the same range as the reported stiffness of cancellous bone. The measured creep strains were low and no significant differences between formulations were observed. The stiffness significantly increased when the samples were subjected to a second loading stage. The residual strains calculated from this second loading stage were also significantly different from the first loading stage, showing an increasing difference with an increasing binder content. Since residual strains are detrimental for graft layer stability in load-bearing defects, putty compositions with a low binder content would be most beneficial for confined, load-bearing bone defect grafting.

Mechanical behaviour of Bioactive Glass granules and morselized cancellous bone allograft in load bearing defects.

Bioactive Glass (BAG) granules are osteoconductive and possess unique antibacterial properties for a synthetic biomaterial. To assess the applicability of BAG granules in load-bearing defects, the aim was to compare mechanical behaviour of graft layers consisting of BAG granules and morselized cancellous bone allograft in different volume mixtures under clinically relevant conditions. The graft layers were mechanically tested, using two mechanical testing modalities with simulated physiological loading conditions: highly controllable confined compression tests (CCT) and more clinically realistic in situ compression tests (ISCT) in cadaveric porcine bone defects. Graft layer impaction strain, residual strain, aggregate modulus, and creep strain were determined in CCT. Graft layer porosity was determined using micro computed tomography. The ISCT was used to determine graft layer subsidence in bone environment. ANOVA showed significant differences (p<0.001) between different graft layer compositions. True strains absolutely decreased for increasing BAG content: impaction strain -0.92 (allograft) to -0.39 (BAG), residual strain -0.12 to -0.01, and creep strain -0.09 to 0.00 respectively. Aggregate modulus increased with increasing BAG content from 116 to 653MPa. Porosity ranged from 66% (pure allograft) to 15% (pure BAG). Subsidence was highest for allograft, and remarkably low for a 1:1 BAG-allograft volume mixture. Both BAG granules and allograft morsels as stand-alone materials exhibit suboptimal mechanical behaviour for load-bearing purpose. BAG granules are difficult to handle and less porous, whereas allograft subsides and creeps. A 1:1 volume mixture of BAG and allograft is therefore proposed as the best graft material in load-bearing defects.

Clinical Applications of S53P4 Bioactive Glass in Bone Healing and Osteomyelitic Treatment: A Literature Review.

Nowadays, S53P4 bioactive glass is indicated as a bone graft substitute in various clinical applications. This review provides an overview of the current published clinical results on indications such as craniofacial procedures, grafting of benign bone tumour defects, instrumental spondylodesis, and the treatment of osteomyelitis. Given the reported results that are based on examinations, such as clinical examinations by the surgeons, radiographs, CT, and MRI images, S53P4 bioactive glass may be beneficial in the various reported applications. Especially in craniofacial reconstructions like mastoid obliteration and orbital floor reconstructions, in grafting bone tumour defects, and in the treatment of osteomyelitis very promising results are obtained. Randomized clinical trials need to be performed in order to determine whether bioactive glass would be able to replace the current golden standard of autologous bone usage or with the use of antibiotic containing PMMA beads (in the case of osteomyelitis).