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Abstract: This paper outlines the basic knowledge that should form an integral component of a training programme in basic biomechanics and biomaterials for orthopaedic residents. For a comprehensive learning package the reader is directed to the substantive textbooks listed in the suggested reading section. [Copyright &y& Elsevier]

Abstract: The influence of four variables on various properties of a Mg-substituted calcium phosphate cement (CPC) was investigated. The variables were the heat treatment temperature of the precipitated powders, the composition of the setting liquid, the liquid-to-powder ratio (LPR), and the time over which hardened specimens were cured in air. The properties analysed were the phase composition of the starting powder, the initial setting time, the evolution of the storage shear modulus (G′) and the loss shear modulus (G″) with the cement paste curing time (t), and the compressive strength. The presence of α-TCP in CPC facilitated the setting and hardening properties due to its progressive dissolution and the formation of brushite crystals. As far as the liquid composition is concerned, in cases where citric acid was used, adding a rheology modifier (10wt.% polyethylene glycol or 0.5wt.% hydroxyl propylmethylcellulose) to the acid led to an increase in the initial setting time, while an increase in the acid concentration led to a decrease in the initial setting time. The initial setting time showed to be very sensitive towards the LPR. The evolution of G′ and G″ with curing time reflected the internal structural changes of cement pastes during the setting process. The compressive strength of the wet-hardened cement specimens with and without Mg increased with curing time increasing, being slightly higher in the case of Mg-substituted CPC. The results suggest that Mg-substituted CPC holds a promise for uses in orthopaedic and trauma surgery such as for filling bone defects. [Copyright &y& Elsevier]

Abstract: This paper outlines the basic knowledge that should form an integral component of a training programme in basic biomechanics and biomaterials for orthopaedic residents. For a comprehensive learning package the reader is directed to the substantive textbooks listed in the suggested reading section. [Copyright &y& Elsevier]

Abstract: Background: The expansion in joint arthroplasty surgery in the 1970s has resulted in a large group of patients who require revision arthroplasty for aseptic loosening. Impaction bone grafting to deal with bone stock loss has become an increasingly popular procedure in revision hip surgery. The results of this revision surgery are variable and very much dependent on the grafting techniques adopted at the time of surgery. In vitro testing of impaction bone grafting methods can constitute an important tool to improve long-term clinical results. The increasing clinical demand for human allograft limits its availability for use in in vitro laboratory studies therefore suitable experimental alternatives are required. Methods: Human, porcine and ovine cancellous bone grafts were morsellised and prepared for in vitro laboratory testing following a standard operative technique. Each graft type was compressed using a die plunger test. After compression to a predetermined level the graft was left to relax for 120s. A comparison of the compression moduli and of the relaxation characteristics for each graft preparation was performed. In addition, the effects of washing the graft and of cartilage removal from the graft mixture were investigated. Results: This study has demonstrated that there is no statistical difference in the compression modulus or relaxation percentage between human and ovine graft preparations. The effect of removing cartilage and washing the graft mixtures were inconsistent with regard to alterations in the viscoelastic properties of the grafts. Interpretation: On the basis of the experiments performed we recommend the use of ovine bone graft as a suitable substitute for human allograft for in vitro testing of impaction bone grafting methods. The properties of ovine graft were similar for both compression moduli and relaxation properties to human allograft. [Copyright &y& Elsevier]

Abstract: Impaction grafting using morsellised bone chips is widely used during surgery to mitigate the effects of bone loss. The technique typically involves the packing of morsellised allograft cancellous bone into bone defects, and has found extensive application in revision hip and knee surgery. In the ideal situation, the presence of the bone graft prevents subsidence of the revised prosthesis in the short term, and integrates with the host bone in the longer term. However, the configuration of particles within the graft remains to be optimised, and is highly likely to vary across potential sites and loading conditions. Human bone, for use in experimental investigation, is often difficult to obtain with properties that are relevant from a clinical point of view. This study, therefore, has explored the mechanical response of a Sawbones based experimental substitute. An established confined compression technique was used to characterise the morsellised Sawbones material. Comparison of the results with published values for bovine and human bone indicate that the mechanical response of the morsellised Sawbones material map well onto the elastic and viscoelastic response of bone of a biological origin. [Copyright &y& Elsevier]

Abstract: Measurements have been performed on Sawbones® and bovine cortical bone samples at 200 kHz using an axial transmission technique to investigate the factors that determine how ultrasonic waves propagate across a simulated fracture. The peak amplitude of the first arrival signal (FAS) was studied. Results taken from intact specimens were compared with those produced when a simple transverse fracture was introduced. These fracture simulation experiments were found to be consistent with Finite Difference modelling of the experimental conditions. The peak amplitude showed a characteristic variation across the fracture caused by interference between reradiated and scattered/diffracted waves at the fracture site and a net Fracture Transmission Loss (FTL). For small fracture gaps, the change in amplitude was sensitive to the presence of the fracture. This sensitivity suggests that this parameter could be a good quantitative indicator for the fracture healing process assuming the relative change in this parameter brought about by healing is measurable. [Copyright &y& Elsevier]