[show abstract][hide abstract] ABSTRACT: The first publication of the work  did not present one of the authors' names. Kunalan Ganthel has now been added to the author list. In addition, Habib Sherkat has been added to the Acknowledgements, with thanks for providing help with the use of hyperelastic module of Abaqus Software.
[show abstract][hide abstract] ABSTRACT: Effective fixation of fracture requires careful selection of a suitable implant to provide stability and durability. Implant with a feature of locking plate (LP) has been used widely for treating distal fractures in femur because of its favourable clinical outcome, but its potential in fixing proximal fractures in the subtrochancteric region has yet to be explored. Therefore, this comparative study was undertaken to demonstrate the merits of the LP implant in treating the subtrochancteric fracture by comparing its performance limits against those obtained with the more traditional implants; angle blade plate (ABP) and dynamic condylar screw plate (DCSP).
Nine standard composite femurs were acquired, divided into three groups and fixed with LP (n = 3), ABP (n = 3) and DCSP (n = 3). The fracture was modeled by a 20 mm gap created at the subtrochanteric region to experimentally study the biomechanical response of each implant under both static and dynamic axial loading paradigms. To confirm the experimental findings and to understand the critical interactions at the boundaries, the synthetic femur/implant systems were numerically analyzed by constructing hierarchical finite element models with nonlinear hyperelastic properties. The predictions from the analyses were then compared against the experimental measurements to demonstrate the validity of each numeric model, and to characterize the internal load distribution in the femur and load bearing properties of each implant.
The average measurements indicated that the constructs with ABP, DCPS and LP respectively had overall stiffness values of 70.9, 110.2 and 131.4 N/mm, and exhibited reversible deformations of 12.4, 4.9 and 4.1 mm when the applied dynamic load was 400 N and plastic deformations of 11.3, 2.4 and 1.4 mm when the load was 1000 N. The corresponding peak cyclic loads to failure were 1100, 1167 and 1600 N. The errors between the displacements measured experimentally or predicted by the nonlinear hierarchical hyperelastic model were less than 18 %. In the implanted femur heads, the principal stresses were spatially heterogeneous for ABP and DCSP but more homogenous for LP, meaning LP had lower stress concentrations.
When fixed with the LP implant, the synthetic femur model of the subtrochancteric fracture consistently exceeds in the key biomechanical measures of stability and durability. These capabilities suggest increased resistance to fatigue and failure, which are highly desirable features expected of functional implants and hence make the LP implant potentially a viable alternative to the conventional ABP or DCSP in the treatment of subtrochancteric femur fractures for the betterment of clinical outcome.
[show abstract][hide abstract] ABSTRACT: The use of bicortical screws to fix metacarpal fractures has been suggested to provide no added biomechanical advantage over unicortical screw fixation. However, this was only demonstrated in static loading regimes, which may not be representative of biological conditions. The present study was done to determine whether similar outcomes are obtained when cyclic loading is applied. Transverse midshaft osteotomies were created in 20 metacarpals harvested from three cadavers. Fractures were stabilised using 2.0 mm mini fragment plates fixed with either bicortical or unicortical screw fixation. These fixations were tested to failure with a three-point bending cyclic loading protocol using an electromechanical microtester and a 1 kN load cell. The mean load to failure was 370 N (SD 116) for unicortical fixation and 450 N (SD 135) for bicortical fixation. Significant differences between these two constructs were observed. A biomechanical advantage was found when using bicortical screws in metacarpal fracture plating.
The Journal of hand surgery, European volume. 10/2011; 37(5):396-401.