Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association
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Micromovement at fracture sites is known to promote callus formation and bridging of the bony fragments. The present study was conducted to identify the suitable amount of micromovement, and to analyze the location and timing of callus proliferation. A standardized transverse osteotomy, in the right metatarsus of 32 sheep, was used as a fracture model. ⋯ Stimulation of new bone formation by micromovement was mainly effective in the early healing phase (4 weeks postoperatively). Large gaps showed the least new bone formation at the fracture site and the lowest flexural rigidity. From the histological analysis, it was found that the flexural rigidity correlated with the new bone area in the periosteal region.
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We investigated the regenerative capacity of motor nerves repaired by end-to-side or end-to-end neurorrhaphy, using choline-acetyltransferase (ChAT) activity measurement or histological analysis. The right medial gastrocnemius nerves (MGNs) of 62 male Fisher strain rats were transected and divided into three groups. In group 1, the distal ends of the MGN were coapted to the side of the lateral gastrocnemius nerve, using a Y-shaped silicone tube in end-to-side neurorrhaphy. ⋯ Axonal regeneration of MGN and the recovery of MGM to nearly normal histology and weight were observed in groups 1 and 2 3 months postoperatively. Although there were no significant differences in ChAT values between groups 1 and 2, the values were significantly larger than that of group 3 3 months postoperatively. These findings suggested that end-to-side neurorrhaphy would be an alternative treatment for peripheral nerve injury in certain clinical situations.
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In this experimental study, the influence of flexible nailing in the later phase of femoral fracture healing was investigated. Sixty rats were randomly assigned to three groups. In 20 rats no intervention was performed, and they served as a control group. ⋯ All values for biomechanical characteristics were reduced at 60 and 90 days in flexibly nailed bones compared with intact femurs, while in the rigid nailing group, bending load and fracture energy were similar to those in intact bones at 90 days. Bone mineral content in the callus segment and diaphysis was greater in the rigidly nailed bones than in the flexible nailing group at 60 days, while at 90 days, no differences were detected. In conclusion, this animal study indicates that: (1) flexible nailing in the later phase of fracture healing increases callus formation, while (2) the quality of bone healing is reduced.
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We made an animal model of cervical spinal cord injury in a cat and performed electrophysiological, histological, and bechavioral studies. The cervical spinal cord injury model was made by inserting a screw through the fourth cervical vertebral body of the cat. After the injury, muscle tonus of the limbs and trunk diminished. ⋯ There was demyelination and gliosis in the ventral funiculus and in part of the ventrolateral funiculus at or near the injured site. Electrophysiological and histological findings were in good agreement with the behavioral ones. Behavioral studies seem useful for evaluating the function of the spinal cord, especially for assessing the injured system in the spinal cord.