Nordsletten L, Kaastad T S, Obrant K J, Skjeldal S, Kirkeby O J, Stokke O, Ekeland A
Institute for Surgical Research, Rikshospitalet (National Hospital), Oslo, Norway.
J Bone Miner Res. 1994 May;9(5):679-85. doi: 10.1002/jbmr.5650090513.
The increase in structural capacity due to muscle contraction in the lower leg was investigated in osteopenic and normal rats. Osteopenia was induced by ovariectomy combined with a low-calcium diet (0.01%). The control rats were sham operated and fed a diet containing 1.1% calcium. After 7 weeks the right lower leg of all animals were fractured in three-point ventral cantilever bending during muscle contraction induced by electrical stimulation of the ischiatic nerve. The left tibiae were resected and fractured as each animal's control. During muscle contraction in vivo, the ultimate bending moment, energy absorption, bending stiffness, and deflection were significantly lower in the osteopenic than in the sham-operated animals. However, the increase in mechanical parameters due to muscle contraction comparing the in vivo and resected tibiae in each animal were equally high in the osteopenic and sham-operated animals. Ultimate bending moment in the resected tibiae was 10% higher in the sham-operated animals compared with the ovariectomized, proving mechanically weaker tibiae in the osteopenic rats. In accordance with this, the medullary area of the osteopenic rats was 46% larger in the distal tibial diaphysis, and the ultimate stress the tibiae could withstand was 15% lower in the osteopenic compared with the sham-operated rats. The trabecular bone volume in the distal tibial metaphysis of the osteopenic rats was reduced by 70% compared with the sham operated. This study shows that muscle protection against fracture can be substantial in osteopenic tibia and that it is of the same magnitude as in rats with normal bone mass.
在骨质疏松大鼠和正常大鼠中研究了小腿肌肉收缩导致的结构能力增加情况。通过卵巢切除术联合低钙饮食（0.01%）诱导骨质疏松。对照大鼠进行假手术，并喂食含1.1%钙的饮食。7周后，在坐骨神经电刺激诱导的肌肉收缩过程中，通过三点腹侧悬臂弯曲对所有动物的右小腿进行骨折。切除左胫骨并使其骨折作为每只动物的对照。在体内肌肉收缩过程中，骨质疏松大鼠的极限弯矩、能量吸收、弯曲刚度和挠度显著低于假手术动物。然而，在骨质疏松动物和假手术动物中，每只动物体内和切除胫骨后因肌肉收缩导致的力学参数增加同样高。假手术动物切除胫骨后的极限弯矩比去卵巢动物高10%，这证明骨质疏松大鼠的胫骨在力学上较弱。据此，骨质疏松大鼠胫骨远端骨干的髓腔面积大46%，与假手术大鼠相比，骨质疏松大鼠胫骨能够承受的极限应力低15%。与假手术大鼠相比，骨质疏松大鼠胫骨远端干骺端的小梁骨体积减少了70%。这项研究表明，肌肉对骨质疏松性胫骨骨折的保护作用可能很大，且与正常骨量大鼠的保护作用程度相同。
