比较脊髓损伤及制动后大鼠骨密度与生物力学变化的差异

背景：脊髓损伤及制动均可导致骨质疏松的发生。 目的：建立胸髓横断大鼠动物模型,建立大鼠失用性萎缩模型，观察及比较大鼠胸髓损伤大鼠和失用性骨质疏松大鼠的骨密度及生物力学改变。 设计、时间及地点： 随机对照动物实验，于2008-08/11在解放军第四军医大学骨科研究所实验室完成。 材料：将48只4月龄雌性大鼠分为3组：对照组(假手术组)、制动组、脊髓损伤组。 方法：脊髓损伤组及对照组大鼠麻醉后行T10椎板切除，脊髓损伤组用锐刀横切脊髓，对照组则仅进行椎板切除术而不干预脊髓，制动组大鼠左下肢用小夹板固定后绷带悬吊，室温下分笼饲养，标准大鼠饲料，自由饮水、摄食。 主要观察指标：术后3，6周检测大鼠腰4椎体、肱骨近端、股骨远端、骨盆 骨密度及生物力学变化。 结果：与对照组比较，术后3周，脊髓损伤组大鼠股骨远端骨密度显著下降(P < 0.05)；术后6 周，股骨远端、骨盆骨密度显著下降(P < 0.01，P < 0.05)，两组肱骨近端、腰椎骨密度无明显差异。与对照组比较，术后3周，制动组大鼠股骨远端、腰椎骨密度较对照组下降，差异无显著性意义；术后6 周，股骨远端、腰椎骨密度降低(P < 0.05)。制动组与对照组肱骨近端、骨盆骨密度差异无显著性意义。术后6周，脊髓损伤组骨盆、股骨远端骨密度低于制动组 (P < 0.05)，腰椎骨密度高于制动组 (P < 0.05)。术后3周，脊髓损伤组及制动组大鼠腰椎、肱骨近端及骨盆最大载荷、结构刚度与对照组差异无显著性意义。术后3，6周，脊髓损伤组股骨远端最大载荷、结构刚度均低于对照组 (P < 0.05，P < 0.01)，肱骨近端及腰椎差异无显著性意义。 结论：脊髓损伤及制动均可导致骨质疏松的发生，但骨密度及生物力学变化不同，即两种骨质疏松所发生的部位不同，即使同一部位发生骨质疏松，发生的程度也不相同。

Differences of bone density and biomechanics changes after spinal cord injury and immobilization in rats

BACKGROUND: Both spinal cord injury (SCI) and immobilization can result in osteoporosis. OBJECTIVE: Rats models with both SCI and disuse atrophy were established, so as to make an observation and comparison on bone density and biomechanics changes after both SCI and osteoporosis due to immobilization. DESIGN, TIME AND SETTING: A randomized control animal trial was conducted in the laboratory of Institute of Orthopaedics, Fourth Military Medical University of Chinese PLA from August to November in 2008. MATERIALS: A total of 48 female rats of 4 months were randomly divided into three groups, namely, the control group (sham operation group), the immobilization group and the SCI group. METHODS: After anesthesia, T10 vertebrae plate resection was performed to rats in both the SCI group and the control group, with spinal cords transected only in the former group; rats in the immobilization group were hang with bandages, with their lower left limb fixed with small splints. All rats were housed separately in the normal room temperature, with free access to water and standard rat feeds. MAIN OUTCOME MEASURES: A detection of both bone density and biomechanics was performed to the L4 vertebral body, the proximal humerus, the distal femur and the pelvis of rats 3 and 6 weeks following operation respectively. RESULTS: Compared with the control group, bone density in the distal femur of rats in the SCI group deceased dramatically 3 weeks postoperatively (P < 0.05); bone density in both distal femur and pelvis in the SCI group deceased dramatically 6 weeks postoperatively (P < 0.01, P < 0.05). No bone density difference of significance was found in the proximal humerus and the lumbar vertebra between the two groups. In the immobilization group, bone density in the distal femur and the lumbar vertebra decreased 3 weeks postoperatively compared with that of the control group, but the difference was of no significance; while 6 weeks postoperatively, the significantly decreased bone density was detected in both distal femur and lumbar vertebra in comparison with the control group(P < 0.05). There was no bone density difference of significance in either proximal humerus or pelvis between the two groups. Six weeks postoperatively, bone density in the pelvis and the distal femur of the SCI group was lower than that of the immobilization group (P < 0.05), and in the lumbar vertebra it was higher (P < 0.05). Compared with the control group, no significant difference of maximum load and structural rigidity existed in either proximal humerus or lumbar vertebra or pelvis in both the SCI and the immobilization group 3 weeks postoperatively. However, lower maximum load and structural rigidity showed in the distal femur in the SCI group both 3 and 6 weeks postoperatively compared with the control group (P < 0.05, P < 0.01). The difference in the proximal humerus and the lumbar vertebra was of no significance. CONCLUSION: Both SCI and immobilization can result in osteoporosis, but with different bone density and biomechanical changes, namely, the osteoporosis in different parts or in the same parts but of different degree.