A femoral neck fracture model in rabbits.
ABSTRACT A technique was developed to create a reproducible femoral neck fracture in vitro using 5-month-old JW/CSK series male rabbits. Force attenuation of a newly developed damping material was also evaluated using this model. Ten pairs of the femora with smaller deviations in length and weight were harvested and cleaned of soft tissue. Either a right or left of each pair of the specimens was randomly selected and put into either the control or the experimental group, both of which contained equal numbers of the right and left femora. The specimens were attached to an L-shaped plate and embedded in a resin from the proximal diaphysis to the distal end so as to maintain a consistent position of the femora. They were mounted and fixed on a pedestal slanted in the coronal plane at 20 degrees. The impact load testing was conducted using an impact mallet dropped from a height of 3 cm. The impact load was applied onto the femoral head. To the specimens in the experimental group, attenuated impact forces were loaded through the damping material, but those in the control group were subjected to forces directly transmitted without the material. All the impact testing was performed in a temperature and humidity controlled chamber. All of the femoral specimens exposed to the direct impact forces (controlled group) sustained fracture at the neck. The fracture line passed from the base of the femoral head laterally and to the calcar area just proximal to the minor trochanter medially. The location of each fracture line was almost identical among the specimens. None of the specimens that were exposed to the impact force through the damping material (experimental group) sustained fracture macroscopically and roentgenographically.
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ABSTRACT: Both genetic and environmental factors are known to influence the structure of bone, contributing to its mechanical behavior during, and adaptive response to, loading. We introduce a novel approach to simultaneously address the genetically mediated, exercise-related effects on bone morphometrics and strength, using mice that had been selectively bred for high levels of voluntary wheel running (16 generations). Female mice from high running and control lines were either allowed (n=12, 12, respectively) or denied (n=11, 12, respectively) access to wheels for 20 months. Femoral shaft, neck, and head were measured with calipers and via micro-computed tomography. Fracture characteristics of the femoral head were assessed in cantilever bending. After adjusting for variation in body mass by two-way analysis of covariance, distal width of the femur increased as a result of selective breeding, and mediolateral femoral diameter was reduced by wheel access. Cross-sectional area of the femoral mid-shaft showed a significant linetype x activity effect, increasing with wheel access in high-running lines but decreasing in control lines. Body mass was significantly positively correlated with many of the morphometric traits studied. Fracture load of the femoral neck was strongly positively predicted by morphometric traits of the femoral neck (r2>0.30), but no significant effects of selective breeding or wheel access were found. The significant correlations of body mass with femoral morphometric traits underscore the importance of controlling for body size when analyzing the response of bone size and shape to experimental treatments. After controlling for body mass, measures of the femoral neck remain significant predictors of femoral neck strength.Zoology 02/2008; 111(2):135-47. · 1.47 Impact Factor
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ABSTRACT: Significant difficulties are caused by the delayed union of femoral neck fractures. To address this issue, we designed a new device that applies recombinant human bone morphogenetic protein-2 (rhBMP-2) to promote fracture union. A cannulated screw with holes was used to deliver rhBMP-2 to the fracture site. Fibrin glue was used as an adhesive agent to hold rhBMP-2 in the vicinity of fracture. RhBMP-2 was protected with polylactide-glycolide acid microspheres. RhBMP-2 release was evaluated to determine the effect of the improved screws. When polylactide-glycolide acid microspheres were used, 3.65% of the rhBMP-2 was released in the first 2 h, 5.17% was released within 8 h, and 8.95% was released within 24 h. In the microsphere + fibrin glue group, 1.15% of the rhBMP-2 was released in the first 2 h, 1.75% was released within 8 h, and 6.68% was released within 24 h. Over 42 days, about 76.75% of the rhBMP-2 was released when using fibrin glue, which was lower than the amount released using microspheres alone (91.75%). In dog, a faster repair rate was observed on the side with the improved screw than on the side with traditional screw. The directional release system described here can improve the process of fracture healing and is a promising technique for repairing femoral neck fracture.Tissue Engineering Part A 12/2009; 15(12):3971-8. · 4.64 Impact Factor