Objectives. The purpose of this study was to refine an accepted contaminated
rat femur defect model to result in an infection rate of approximately
50%. This threshold will allow examination of treatments aimed at
reducing infection in open fractures with less risk of type II error. Methods . Defects were created in the stablised femurs of anaethetised
rats, contaminated with Staphylococcus aureus and
then debrided and irrigated six hours later. After 14 days, the
bone and implants were harvested for separate microbiological analysis.
This basic model was developed in several studies by varying the
quantity of bacterial inoculation, introducing various doses of
systemic antibiotics with and without local antibiotics. Results . The bacterial inoculation associated with a 50% infection rate
was established as 1 × 10. 2. colony forming units (CFU). With
an initial bacterial inoculum of 1 × 10. 5. CFU, the dose
of systemic antibiotics associated with 50% infection was 5 mg/Kg
of cafazolin injected sub-cutaneously every 12 hours, starting at
the time of the first debridment and continuing for 72 hours (seven
doses). The systemic dose of cafazolin was lowered to 2 mg/Kg when
antibiotic polymethyl methacrylate beads were used concurrently
with the same amount of bacterial inoculation. Conclusion. This model of open fracture infection has been further refined
with potential for local and systemic antibiotics. This is a versatile
model and with the
One commonly used rat fracture model for bone and mineral research
is a closed mid-shaft femur fracture as described by Bonnarens in
1984. Initially, this model was believed to create very reproducible
fractures. However, there have been frequent reports of comminution
and varying rates of complication. Given the importance of precise
anticipation of those characteristics in laboratory research, we
aimed to precisely estimate the rate of comminution, its importance and
its effect on the amount of soft callus created. Furthermore, we
aimed to precisely report the rate of complications such as death
and infection. We tested a rat model of femoral fracture on 84 rats based on
Bonnarens’ original description. We used a proximal approach with
trochanterotomy to insert the pin, a drop tower to create the fracture
and a high-resolution fluoroscopic imager to detect the comminution.
We weighed the soft callus on day seven and compared the soft callus
parameters with the comminution status.Objectives
Methods
Osteochondral injuries, if not treated adequately, often lead
to severe osteoarthritis. Possible treatment options include refixation
of the fragment or replacement therapies such as Pridie drilling,
microfracture or osteochondral grafts, all of which have certain
disadvantages. Only refixation of the fragment can produce a smooth
and resilient joint surface. The aim of this study was the evaluation
of an ultrasound-activated bioresorbable pin for the refixation of
osteochondral fragments under physiological conditions. In 16 Merino sheep, specific osteochondral fragments of the medial
femoral condyle were produced and refixed with one of conventional
bioresorbable pins, titanium screws or ultrasound-activated pins.
Macro- and microscopic scoring was undertaken after three months. Objectives
Methods
We aimed to further evaluate the biomechanical characteristics
of two locking screws Synthetic tubular bone models representing normal bone density
and osteoporotic bone density were used. Artificial fracture gaps
of 1 cm were created in each specimen before fixation with one of
two constructs: 1) two locking screws using a five-hole locking
compression plate (LCP) plate; or 2) three non-locking screws with
a seven-hole LCP plate across each side of the fracture gap. The
stiffness, maximum displacement, mode of failure and number of cycles
to failure were recorded under progressive cyclic torsional and
eccentric axial loading.Objectives
Methods
