Several bisphosphonates are now available for the treatment of osteoporosis. Porous hydroxyapatite/collagen (HA/Col) composite is an osteoconductive bone substitute which is resorbed by osteoclasts. The effects of the bisphosphonate alendronate on the formation of bone in porous HA/Col and its resorption by osteoclasts were evaluated using a rabbit model. Porous HA/Col cylinders measuring 6 mm in diameter and 8 mm in length, with a pore size of 100 μm to 500 μm and 95% porosity, were inserted into a defect produced in the lateral femoral condyles of 72 rabbits. The rabbits were divided into four groups based on the protocol of alendronate administration: the control group did not receive any alendronate, the pre group had alendronate treatment for three weeks prior to the implantation of the HA/Col, the post group had alendronate treatment following implantation until euthanasia, and the pre+post group had continuous alendronate treatment from three weeks prior to surgery until euthanasia. All rabbits were injected intravenously with either saline or alendronate (7.5 μg/kg) once a week. Each group had 18 rabbits, six in each group being killed at three, six and 12 weeks post-operatively. Alendronate administration suppressed the resorption of the implants. Additionally, the mineral densities of newly formed bone in the alendronate-treated groups were lower than those in the control group at 12 weeks post-operatively. Interestingly, the number of osteoclasts attached to the implant correlated with the extent of bone formation at three weeks. In conclusion, the systemic administration of alendronate in our rabbit model at a dose-for-weight equivalent to the clinical dose used in the treatment of osteoporosis in Japan affected the mineral density and remodelling of bone tissue in implanted porous HA/Col composites.
Aims. The aim of this study was to determine the immediate post-fixation stability of a distal tibial fracture fixed with an intramedullary nail using a biomechanical model. This was used as a surrogate for immediate weight-bearing postoperatively. The goal was to help inform postoperative protocols. Methods. A biomechanical model of distal metaphyseal tibial fractures was created using a fourth-generation composite
We hypothesised that the anterior and posterior
walls of the body of the first sacral vertebra could be visualised with
two different angles of inlet view, owing to the conical shape of
the sacrum. Six dry male cadavers with complete pelvic rings and
eight dry sacrums with K-wires were used to study the effect of
canting (angling the C-arm) the fluoroscope towards the head in
5° increments from 10° to 55°. Fluoroscopic images were taken in
each position. Anterior and posterior angles of inclination were
measured between the upper sacrum and the vertical line on the lateral
view. Three authors separately selected the clearest image for overlapping
anterior cortices and the upper sacral canal in the cadaveric models.
The dry bone and K-wire models were scored by the authors, being
sure to check whether the
K-wire was in or out. In the dry
The augmentation of fixation with bone cement
is increasingly being used in the treatment of severe osteoporotic fractures.
We investigated the influence of bone quality on the mechanics of
augmentation of plate fixation in a distal femoral fracture model
(AO 33 A3 type). Eight osteoporotic and eight non-osteoporotic femoral
models were randomly assigned to either an augmented or a non-augmented
group. Fixation was performed using a locking compression plate.
In the augmented group additionally 1 ml of bone cement was injected
into the screw hole before insertion of the screw. Biomechanical
testing was performed in axial sinusoidal loading. Augmentation significantly
reduced the cut-out distance in the osteoporotic models by about
67% (non-augmented mean 0.30 mm ( Cite this article:
We investigated the static and cyclical strength of parallel and angulated locking plate screws using rigid polyurethane foam (0.32 g/cm3) and bovine cancellous bone blocks. Custom-made stainless steel plates with two conically threaded screw holes with different angulations (parallel, 10° and 20° divergent) and 5 mm self-tapping locking screws underwent pull-out and cyclical pull and bending tests. The bovine cancellous blocks were only subjected to static pull-out testing. We also performed finite element analysis for the static pull-out test of the parallel and 20° configurations. In both the foam model and the bovine cancellous bone we found the significantly highest pull-out force for the parallel constructs. In the finite element analysis there was a 47% more damage in the 20° divergent constructs than in the parallel configuration. Under cyclical loading, the mean number of cycles to failure was significantly higher for the parallel group, followed by the 10° and 20° divergent configurations. In our laboratory setting we clearly showed the biomechanical disadvantage of a diverging locking screw angle under static and cyclical loading.