Background. A large proportion of the expense incurred due to hip fractures arises due to secondary factors such as duration of hospital stay and additional theatre time due to surgical complications. Studies have shown that the use of intramedullary (IM) nail fixation presents a statistically higher risk of re-fracture than plating, which has been attributed to the stress riser at the end of the nail. It is not clear, however, if this situation also applies to unstable fractures, for which plating has a higher fixation failure rate. Moreover, biomechanical studies to date have not considered newer designs of IM nails which have been specifically designed to better distribute weight-bearing loads. This aim of this experimental study was to evaluate the re-fracture risk produced by a newer type of nailing system compared to an equivalent plate. Methods. Experimental testing was conducted using fourth generation Sawbones composite femurs and X-Bolt IM hip nail (n=4) and fracture plate (n=4) implants. An unstable pertrochanteric fracture pattern was used (AO classification: 31-A1 / 31-A2). Loading was applied along the peak loading vector experienced during walking, up to a maximum load of 500N. The risk of re-fracture was evaluated from equivalent strains measured using four rosette strain gauges on the surface of the bone at known stress riser locations. Results. Strain gauge readings determined that the equivalent strains in the femoral diaphysis were approximately 25% larger for the nail than the plate (p < 0.005). The strain levels at the location coinciding with the end of the plate were also larger for the nail, but not significantly (p > 0.26). Conclusions. Although the risk of re-fracture for displaced tronchantaric fractures was found to be larger for nailing than plating, measured strains were substantially lower than the failure strain of cortical bone (even when scaled for full weight-bearing loads of 1800N). This indicates that fracture risk is not present in either implant for bone of healthy quality, but may still become problematic in highly osteoporotic patients. Level of Evidence. IIb - Evidence from at least one well designed experimental trial

Finite element modelling is being extensively used to evaluate the biomechanical behaviour of fractured bone treated with fixation devices. Appropriate modelling of the bone-implant interface is key to quality biomechanical prediction. The present study considers this interface modelling in the context of locking plates. A majority of previous studies assume the interface to be represented by a tied constraint or a fully bonded interface. Many other studies incorporate a frictional interface but ignore screw threads. This study compares the various interface modelling strategies. An interface with screw threads explicitly included is also considered. The study finds that interface modelling has significant impact on both the global and local behaviour. Globally, the load-deflection behaviour shows considerable difference depending on the interface model. Locally, the stress-strain environment within the bone close to the screws is significantly altered. The results show that the widely used tie constraint can overestimate stiffness of a construct which must be correctly predicted to avoid non-union or periprosthetic re-fracture, especially in osteoporotic bone. In addition, the predictions of screw loosening, bone damage and stress shielding are very different when screw threads are included in the model

Objectives

The purpose of this study was to compare the results and complications of tibial lengthening over an intramedullary nail with treatment using the traditional Ilizarov method.