Abstract: Objective To observe the effect of low frequency vibration (LFV) on bone metabolism, bone mass density (BMD), bone histomorphometric and biomechanical characterization in rats with secondary osteoporosis (OP) after spinal cord injury (SCI).MethodsSCI model was established with 50 SD rats by transecting spinal cord completely at the level of tenth thoracic vertebra, and the animals were randomly divided into 5 groups: SCI 6-week control group, SCI 12-week control group, vibration 6-week (Vi 6w) group, vibration 12-week (Vi 12w) group and vibration 6-12 week (Vi 6-12w) group. All rats of vibration groups accepted LFV (frequency=20 Hz, acceleration=0.15 g) with 10 minutes once, twice per day, and 6 days per week. The LFV was given from the forth day postoperation to the end of the sixth week in Vi 6w group, and to the end of twelfth week in Vi 12w group, while from the seventh week postoperation to the end of twelfth week in Vi 6-12w group. All animals were sacrificed when LFV test finishied. The serum alkaline phosphatase (ALP), bone glaprotein (BGP) and serum calcium (Ca2+)/BMD of femur and the fifth lumbar vertebra (L5)/bone histomorphometric characterization of tibia/bone biomechanical characterization of femur and L5 were measured.ResultsCompared with control groups, the serum Ca2+ and BMD of promixal femur improved significantly in rats of Vi 6w group ( P<0.05), while the maximal load of L5 increased significantly in rats of Vi 12 group ( P<0.05). There were no changes in rats of Vi 6-12w group ( P>0.05).ConclusionThe early treatment of LFV may improve the secondary OP of rats with SCI, but the effect is different in different sites of rats' body. The late treatment of LFV can't improve the secondary OP, but may keep rats with SCI from deteriorating.

Key words: spinal cord injury, osteoporosis, low frequency vibration, bone metabolism, bone mass