Calcium phosphate cements (CPC) are used as biocompatible and bioactive bone void fillers. Ideally, the mechanical properties of these cements should match those of the surrounding bone. The knowledge of the real mechanical properties of the material is important in the decision-making process regarding possible use of the CPCs in different anatomical sites. Although it is generally recognized that these cements are stiffer and more brittle than desired, there is a limited amount of data about the possible deformation of this class of material before failure. The focus of this study was to determine these properties of injectable CPCs. Two different types of self-setting CPCs were investigated in this study: i) hydroxyapatite (HA), that historically has been the most widely studied CPC; ii) brushite, that recently has attracted attention due to its faster resorption than that of HA in vivo. Specimens of both cement types were prepared by mixing a powder phase with a liquid phase that were left to harden in phosphate buffered saline at 37°C. Once set, the specimens underwent a quasi-static compressive test to determine the compressive strength, the elastic modulus and the maximum deformation of the two materials. The material testing machine was equipped with a digital image correlation system, which allows accurate measurement of material deformation directly on the specimen surface. Brushite was found to be significantly more stiff (+80%) and resistant (+84%) than HA. Similar findings were found for the energy needed to create a first crack on the specimen surface. However, the first crack appeared on the specimen surface at the same low deformation level (∼0.15%) independently of the type of material tested. Complete failure of both materials occurred, on average, before reaching 0.25%. It has been demonstrated that the compressive behaviour of CPCs depends on their composition and porosity [1]. One of the main reasons for the high strength and stiffness of the brushite studied here was its low porosity (∼12%). However, the maximum deformation is not positively affected by this decrease in porosity. In fact, both materials show the same brittle behaviour, i.e. they undergo comparably little deformation before they break. Under these conditions, increasing the compressive strength may not always be beneficial clinically, e.g. in the treatment of vertebral compression fractures, where the high stiffness of the bone cements used has been identified as a risk factor for adjacent-level fractures [2]. However, it is not clear whether a 20-fold higher stiffness than the trabecular bone would give a different clinical outcome than a 10-fold higher stiffness. These high-strength, high-stiffness cements may also be used as a basis for further biomaterial development, e.g. in the creation of macro-porous scaffolds, which is usually challenging due to the commonly low mechanical properties of the base CPC material

Purpose. Gustilo type III open fractures are associated with high infection rates in spite of instituting a standard of care (SOC) consisting of intravenous antibiotics, irrigation and debridement (I&D), and delayed wound closure. Locally-delivered antibiotic has been proven to assist in reducing infection in open fractures. The aims of this study are to determine the effectiveness and safety of a new implantable and biodegradable antibacterial product. 1. in preventing bacterial infections and initiating bone growth in open fractures. Methods. The osteoconductive antibacterial BonyPid. TM. used is a synthetic bone void filler (comprised of ≤1 mm β-tricalcium phosphate granules) coated by a thin layer (≤20 µm) of PolyPid nanotechnology formulation. −. Upon implantation, the coating releases doxycycline at a constant rate for a predetermined period of 30 days. One BonyPid. TM. vial of 10 grams contains 65 mg of formulated doxycycline. After approval, sixteen subjects with Gustilo type III open tibia fractures, were implanted with the BonyPid. TM. immediately on the first surgical intervention (I&D), followed by external fixation. Patients had periodic laboratory, bacteriology and radiology follow-up. Results. Six months results showed that no infection developed and only one BonyPid. TM. implantation was needed with no subsequent I&D, in the target tibia fracture. Immediate soft wound closure was done in 6/16 subjects following implantation. Out of 10 remaining subjects, 3 needed soleus muscle transfer-skin grafting and 7 required delayed primary closure; by skin grafting (5) or suturing (2). Early callus formation was seen at 8–12 weeks post-surgery, followed by bone healing seen from 16 weeks onwards. Safety of implantation was remarkable, with only one deep infection at a fibular open fracture without BonyPid. TM. implantation. One BonyPid. TM. -related adverse event caused delay in skin healing due to excessive granules in the superficial soft tissues. Conclusion. BonyPid. TM. is effective in reducing bone infection and promoting early callus formation, resulting in early bone healing. BonyPid. TM. is safe for immediate implantation into contaminated/infected severe open-bone fractures. Results support that one month release of doxycycline in a controlled manner provides an effective way for treating open fractures. This new local antibiotic delivery system is applicable in unmet medical situations associated with localised infections