Physical Therapy and Rehabilitation Science, Carver College of Medicine, The University of Iowa, Iowa City, IA 52242-1190, USA.
Osteoporos Int. 2012 Sep;23(9):2335-46. doi: 10.1007/s00198-011-1879-4. Epub 2011 Dec 21.
People with spinal cord injury (SCI) lose bone and muscle integrity after their injury. Early doses of stress, applied through electrically induced muscle contractions, preserved bone density at high-risk sites. Appropriately prescribed stress early after the injury may be an important consideration to prevent bone loss after SCI.
Skeletal muscle force can deliver high compressive loads to bones of people with spinal cord injury (SCI). The effective osteogenic dose of load for the distal femur, a chief site of fracture, is unknown. The purpose of this study is to compare three doses of bone compressive loads at the distal femur in individuals with complete SCI who receive a novel stand training intervention.
Seven participants performed unilateral quadriceps stimulation in supported stance [150% body weight (BW) compressive load-"High Dose" while opposite leg received 40% BW-"Low Dose"]. Five participants stood passively without applying quadriceps electrical stimulation to either leg (40% BW load-"Low Dose"). Fifteen participants performed no standing (0% BW load-"Untrained") and 14 individuals without SCI provided normative data. Participants underwent bone mineral density (BMD) assessment between one and six times over a 3-year training protocol.
BMD for the High Dose group significantly exceeded BMD for both the Low Dose and the Untrained groups (p < 0.05). No significant difference existed between the Low Dose and Untrained groups (p > 0.05), indicating that BMD for participants performing passive stance did not differ from individuals who performed no standing. High-resolution CT imaging of one High Dose participant revealed 86% higher BMD and 67% higher trabecular width in the High Dose limb.
Over 3 years of training, 150% BW compressive load in upright stance significantly attenuated BMD decline when compared to passive standing or to no standing. High-resolution CT indicated that trabecular architecture was preserved by the 150% BW dose of load.
本研究旨在比较三种不同剂量的骨压缩负荷对接受新型站立训练干预的完全性脊髓损伤（SCI）个体的股骨远端的影响。
7 名参与者在支撑位进行单侧股四头肌刺激[150%体重（BW）压缩负荷-“高剂量”，同时对侧腿接受 40% BW-“低剂量”]。5 名参与者在不向任何一条腿施加股四头肌电刺激的情况下被动站立（40% BW 负荷-“低剂量”）。15 名参与者不进行站立（0% BW 负荷-“未训练”），14 名无 SCI 的个体提供了参考数据。参与者在 3 年的训练方案中接受了 1 到 6 次骨密度（BMD）评估。
高剂量组的 BMD 显著高于低剂量组和未训练组（p<0.05）。低剂量组和未训练组之间没有显著差异（p>0.05），表明进行被动站立的参与者的 BMD 与不进行站立的个体没有差异。一名高剂量组参与者的高分辨率 CT 成像显示，高剂量肢体的 BMD 增加了 86%，小梁宽度增加了 67%。
在 3 年的训练中，与被动站立或不站立相比，直立位的 150% BW 压缩负荷显著减缓了 BMD 的下降。高分辨率 CT 表明，150% BW 剂量的负荷保持了小梁结构的完整性。
