Chamoli Uphar, Chen Alan S, Diwan Ashish D
Spine Service, Department of Orthopaedic Surgery, St. George & Sutherland Clinical School, University of New South Wales, Kogarah, Sydney, NSW 2217, Australia; School of Mechanical and Manufacturing Engineering, University of New South Wales, Kensington campus, Sydney, NSW 2052, Australia.
Spine Service, Department of Orthopaedic Surgery, St. George & Sutherland Clinical School, University of New South Wales, Kogarah, Sydney, NSW 2217, Australia.
Clin Biomech (Bristol). 2014 Dec;29(10):1108-15. doi: 10.1016/j.clinbiomech.2014.10.002. Epub 2014 Oct 12.
A spondylolytic defect in lumbar vertebra is a common condition during early childhood and adolescence, and is considered a precursor to spondylolisthesis. This study examined whether a bilateral spondylolytic defect in lumbar spine intrinsically results in increased intervertebral translations during different bending motions.
Seven fresh frozen cadaveric kangaroo lumbar (L1-L6) spine specimens were tested in a kinematic spine simulator; first in their intact state, followed by creating a bilateral spondylolytic defect at L4 and retesting. In addition to recording global and segmental range of motions, the pedicles at L3, L4, and L5 vertebrae were digitized bilaterally and virtually tracked throughout testing. Interpedicular kinematic metrics were employed to capture any changes in translatory motions during flexion-extension, bilateral bending, and axial torsion testing modes.
Following the defect, range of motion at the defect level (L4-L5) increased significantly in all the three motion planes. At L4-L5, normalized interpedicular displacement increased significantly in flexion-extension (median change +156%) and bilateral bending (median change +58%) motions, but changes in bending-plane and out-of-plane intervertebral translations were not significant in any of the testing modes.
In the absence of any significant changes in bending-plane and out-of-plane intervertebral translations at L4-L5, changes in interpedicular displacement would directly correspond with the stretching of posterior annulus of the L4-L5 intervertebral disc. A bilateral spondylolytic defect at L4 may result in significant overstretching of the posterior annulus of the L4-L5 disc during flexion-extension and bilateral bending motions.
腰椎峡部裂缺损在儿童早期和青少年时期较为常见，被认为是腰椎滑脱的先兆。本研究旨在探讨腰椎双侧峡部裂缺损是否会在不同弯曲运动中导致椎间平移增加。
对7个新鲜冷冻的袋鼠腰椎（L1-L6）脊柱标本在脊柱运动模拟器中进行测试；首先测试其完整状态，然后在L4处制造双侧峡部裂缺损并重新测试。除了记录整体和节段性运动范围外，在测试过程中对L3、L4和L5椎体的双侧椎弓根进行数字化处理并进行虚拟跟踪。采用椎弓根间运动学指标来捕捉屈伸、双侧弯曲和轴向扭转测试模式下平移运动的任何变化。
制造缺损后，缺损节段（L4-L5）在所有三个运动平面上的运动范围均显著增加。在L4-L5节段，屈伸（中位数变化+156%）和双侧弯曲（中位数变化+58%）运动中，标准化椎弓根间位移显著增加，但在任何测试模式下，弯曲平面和平面外椎间平移的变化均不显著。
在L4-L5节段弯曲平面和平面外椎间平移无任何显著变化的情况下，椎弓根间位移的变化将直接对应于L4-L5椎间盘后环的拉伸。L4处的双侧峡部裂缺损可能会在屈伸和双侧弯曲运动中导致L4-L5椎间盘后环过度拉伸。
