title: The effects of a new shape-memory alloy interspinous process device on the distribution of intervertebral disc pressures in vitro.
abstract: This study was designed to measure the pressure distribution of the intervertebral disc under different degrees of distraction of the interspinous process, because of a suspicion that the degree of distraction of the spinous process may have a close relationship with the disc load share. Six human cadaver lumbar spine L2-L5 segments were loaded in flexion, neutral position, and extension. The L3-L4 disc load was measured at each position using pressure measuring films. Shape-memory interspinous process implants (SMID) with different spacer heights, ranging in size from 10 to 20 mm at 2 mm increments, were used. It was found that a SMID with a spacer height equal to the distance of the interspinous process in the neutral position can share the biomechanical disc load without a significant change of load in the anterior annulus. An interspinous process stabilizing device (IPD) would not be appropriate to use in those cases with serious spinal stenosis because the over-distraction of the interspinous process by the SMID would lead to overloading the anterior annulus which is a recognized cause of disc degeneration.
authors.affiliation: Department of Orthopaedics, Nanjing First Hospital Affiliated to Nanjing Medical University,Nanjing 210029,Jiangsu Province, China;
authors.forename: Shengnai
authors.initials: S
authors.lastname: Zheng
authors.forename: Qingqiang
authors.initials: Q
authors.lastname: Yao
authors.forename: Li
authors.initials: L
authors.lastname: Cheng
authors.forename: Yan
authors.initials: Y
authors.lastname: Xu
authors.forename: Peng
authors.initials: P
authors.lastname: Yuan
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Zhang
authors.forename: Xiangwen
authors.initials: X
authors.lastname: Liao
authors.forename: Liming
authors.initials: L
authors.lastname: Wang
keywords: Lumbar spine; biomechanics; disc pressure; interspinous process device
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