| Anotomic Basis and Biomechanical Evaluation of Distractive Laminoplasty for Lumbar Spinal StenosisLumbar spinal stenosis is a common cause of low back and low extremity pain, particularly in elderly population. Although traditional laminectomy can effectively decompress the stenosis canal and achieve good results, associated problems, such as creation of large dead space, possible instability and epidural adhesion, occurred. To overcome these complications and conincide with the trend of minimally invasive surgery techniques, laminoplasty have evolved to adequately decompress the stenosis of the spine while the structural preservation is maximized. Distractive laminoplasty (DLP), which is devised to overcome shortcomings of previous operatve methods of same type, is a novel approach introduced recently. Our aim in this study was to testify the feasibility of DLP in clinical anotomic aspect and to evaluate the multidirectional mechanical stability after DLP and tradional laminectomy. Modification of DLP and preliminary clinical results was also reported.1. The Quantitative Anatomy of Adult Lumbar Spinal Laminas, Spinal Process, Spinal Canal and Observation of Spinal Nerve RootTo study the anotomic basis of distractive laminoplasty, laminas and spinal process from L1-5 of 24 adult cadaver specimens, with formalin fixed, was quantitatively measured. The evaluation included (1) laminar height, width, thickness; (2) spinal process height and width; (3) spinal canal saggital and transverse diameter; (4) nerve root to laminae lower edge distance. Compressive condition and orientation of nerve root was also observed. The results demonstrated that laminar height gradually decreased from L1 to L5 while laminar width increased form L1 to L5. Significant difference was found between the thickness of lower and upper laminar edge. The greatest height of spinal process was at L3 and L4, and the least was at L5. For a certain spinal process, the cephalad edge height was greater than the caudad edge. The greatest width was at L3 and the least was at L5. L1 had the greatest spinal canal saggital diameter while L3 and L4 showed the least saggital diameter. The transverse diameter of spinal canal increased from L1 to L5. For a certain vertebrae, the caudad level of canal showed the greater saggital diameter than the caudad level. In this study, no compression was founded in L3 root. 11 of 48 (18.7%) L4 roots, total of 14 points, were found compressed, including 6 (42.9%) intraspinal (IS) compression, 7 (50%) intraforaminal (IF) compression and 1 (7.1%) extraforaminal (EF) compression. 13 of 48 (27.1%) L5 nerve roots, total of 16 points, were found compressed, including 8 (50%) IS compression, 5 (31.3%) IF compression and 3 (18.7%) EF compression. The angle between nerve root and dura decreased as the level lowered, especially for the L5 nerve root, which showed significant difference (p<0.05) when compared withother nerve root. The nerve root to laminae lower edge distance gradually decreased from L2 to L5, no significant difference was found between different levels.2. Dynamic Measurement of Lumbar Interlaminar DistractionTo testify the feasibility of distractive technique between lumbar laminas, 3 fresh human cadaver body and 4 fresh-frozen cadaver specimens from L1 to Sacrum were studied. The results showed that interlaminar working space typically can be distracted an average of 0.93±0.24cm (0.52-1.29). The increment of interlaminar distance post distraction in 3 fresh human cadaver body was 0.52-1.15. L3-4 and L4-5 were easier to be distracted compared with L5-S1 (p<0.01), with an average increment of 1.04 (76%), 1.03 (72%), 0.56 (40%) cm respectively. Measurement of 4 fresh-frozen lumbar specimens showed a similar pattern as mentioned above, except for the slightly high degree of distraction, but no statistically significant difference was observed. The average interlaminar distance increment post distraction was 1.08cm (75%) for L3-4, 1.13cm (79.5%) for L4-5 and 0.7cm (48.5%) for L5-S1. The motion was o...
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