Objectives. We aimed to further evaluate the biomechanical characteristics
of two locking screws versus three standard bicortical
screws in synthetic models of normal and osteoporotic bone. Methods. Synthetic tubular
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
Aim. To investigate the biomechanical behaviours of the TL-Hex & Taylor Spatial Frame (TSF) Hexapod external fixators, with comparison to traditional ring-fixator constructs. Methods. Standardised four-ring TL-Hex and TSF constructs, as well as matched ilizarov threaded-rod constructs for each set of components, were tested alone and mounted with an acrylic
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
Simulation in surgical training has become a key component of surgical training curricula, mandated by the GMC, however commercial tools are often expensive. As training budgets become increasingly pressurised, low-cost innovative simulation tools become desirable. We present the results of a low-cost, high-fidelity simulator developed in-house for teaching fluoroscopic guidewire insertion. A guidewire is placed in a 3d-printed plastic bone using simulated fluoroscopy. Custom software enables two inexpensive web cameras and an infra-red led marker to function as an accurate computer navigation system. This enables high quality simulated fluoroscopic images to be generated from the original CT scan from which the
Postoperative malalignment of the femur is one of the main complications in distal femur fractures. Few papers have investigated the impact of intraoperative malalignment on postoperative function and bone healing outcomes. The aim of this study was to investigate how intraoperative fracture malalignment affects postoperative bone healing and functional outcomes. In total, 140 patients were retrospectively identified from data obtained from a database of hospitals participating in a trauma research group. We divided them into two groups according to coronal plane malalignment of more than 5°: 108 had satisfactory fracture alignment (< 5°, group S), and 32 had unsatisfactory alignment (> 5°, group U). Patient characteristics and injury-related factors were recorded. We compared the rates of nonunion, implant failure, and reoperation as healing outcomes and Knee Society Score (KSS) at three, six, and 12 months as functional outcomes. We also performed a sub-analysis to assess the effect of fracture malalignment by plates and nails on postoperative outcomes.Aims
Methods
Introduction. Conventional screws achieve sufficient insertion torque in healthy bone. In poor bone screw stripping can occur prior to sufficient torque generation. It was hypothesized that a screw with a larger major/minor diameter ratio would provide improved purchase in poor bone as compared to conventional screws. We evaluated the mechanical characteristics of such a screw using multiple poor
External fixators are the traditional fixation method of choice for contaminated open fractures. However, patient acceptance is low due to the high profile and therefore physical burden of the constructs. An externalised locking compression plate is a low profile alternative. However, the biomechanical differences have not been assessed. The objective of this study was to evaluate the axial and torsional stiffness of the externalised titanium locking compression plate (ET-LCP), the externalised stainless steel locking compression plate (ESS-LCP) and the unilateral external fixator (UEF). A fracture gap model was created to simulate comminuted mid-shaft tibia fractures using synthetic composite bones. Fifteen constructs were stabilised with ET-LCP, ESS-LCP or UEF (five constructs each). The constructs were loaded under both axial and torsional directions to determine construct stiffness.Objectives
Methods
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.
The use of two implants to manage concomitant ipsilateral femoral
shaft and proximal femoral fractures has been indicated, but no
studies address the relationship of dynamic hip screw (DHS) side
plate screws and the intramedullary nail where failure might occur
after union. This study compares different implant configurations
in order to investigate bridging the gap between the distal DHS
and tip of the intramedullary nail. A total of 29 left synthetic femora were tested in three groups:
1) gapped short nail (GSN); 2) unicortical short nail (USN), differing
from GSN by the use of two unicortical bridging screws; and 3) bicortical
long nail (BLN), with two angled bicortical and one unicortical bridging
screws. With these findings, five matched-pairs of cadaveric femora
were tested in two groups: 1) unicortical long nail (ULN), with
a longer nail than USN and three bridging unicortical screws; and
2) BLN. Specimens were axially loaded to 22.7 kg (50 lb), and internally
rotated 90°/sec until failure.Objectives
Methods
Because of the contradictory body of evidence related to the
potential benefits of helical blades in trochanteric fracture fixation,
we studied the effect of bone compaction resulting from the insertion
of a proximal femoral nail anti-rotation (PFNA). We developed a subject-specific computational model of a trochanteric
fracture (31-A2 in the AO classification) with lack of medial support
and varied the bone density to account for variability in bone properties
among hip fracture patients.Objectives
Methods
The objective of this study was to determine if a synthetic bone
substitute would provide results similar to bone from osteoporotic
femoral heads during Pushout studies were performed with the dynamic hip screw (DHS)
and the DHS Blade in both cadaveric femoral heads and artificial
bone substitutes in the form of polyurethane foam blocks of different
density. The pushout studies were performed as a means of comparing
the force displacement curves produced by each implant within each
material.Introduction
Methods