Abelin-Genevois Kariman, Estivalezes Erik, Briot Jerome, Sévely Annick, Sales de Gauzy Jerome, Swider Pascal
Department of Spine Surgery, CMCR des Massues, Croix Rouge Française, 92 rue Edmond Locard, 69322, Lyon Cedex 05, France,
Eur Spine J. 2015 Jun;24(6):1183-90. doi: 10.1007/s00586-015-3875-4. Epub 2015 Apr 2.
To analyze the disc hydration and volumetric changes of the intervertebral disc after scoliosis surgery depending on the sagittal spino-pelvic organization.
We conducted a prospective MRI study in 45 patients with surgically treated adolescent idiopathic scoliosis (AIS) with a minimum 2-year follow-up. Fusion ended at L1 (n = 13), L2 (n = 14), L3 (n = 11) or L4 (n = 7). Total disc (Vd) and nucleus volumes (Vn) were extrapolated from 3D reconstruction using a custom-made image processing software (Biomechlab, Toulouse, France). Nucleus and external disc contours were semi-automatically detected on turbo spin echo T2-weighted sequence joined 3-mm sagittal cuts. Disc hydration was extrapolated from the nucleus-disc volume ratio (Vn/Vd). Radiographic sagittal parameters were measured pre- and post-operatively on full spine standing views (pelvic incidence, sacral slope, L1S1 lumbar lordosis). Lumbo-pelvic congruity was calculated by the ratio LL/SS according to Stagnara.
Mean PI of the cohort was 55° (34°-85°). After surgical correction, lumbar lordosis was slightly increased by 3° (p = 0.02) decreasing lumbo-pelvic congruity from 1.37 to 1.27 (p < 0.01). When pelvic incidence was less than 55° (mean PI 46°), nucleus volumes have increased on average by 30 % compared to the preoperative status in the unfused lumbar discs, while the total disc volumes has remained stable. Five-year follow-up (n = 13) confirmed the constant improvement of the disc hydration ratio. When PI was high (mean PI 64°), volumetric changes were very mild and significant changes in nucleus volumes and disc hydration ratio concerned only the intermediate lumbar levels (L2L3, L3L4 and L4L5).
This prospective MRI study showed a significant and sustainable improvement in T2 hypersignal of the disc, indirectly indicating improvement of disc hydration content after AIS surgery. Analysis of disc volumetric changes according to the pelvic incidence suggests that these changes are under the influence of the sagittal spino-pelvic alignment. PI seems to play a key role in the homeostasis of the discs under fusion and should be taken into account for preoperative planning. The restoration of the lumbo-pelvic congruence may help to limit early degenerative changes in the free-motion segment discs after AIS surgery. Hydration content was less sensitive to surgery when PI was high, suggesting higher shear stress in the lower discs. Longer follow-up is required to confirm this hypothesis.
根据矢状位脊柱-骨盆结构分析脊柱侧弯手术后椎间盘的水合作用及体积变化。
我们对45例接受手术治疗的青少年特发性脊柱侧弯（AIS）患者进行了一项前瞻性MRI研究，随访时间至少为2年。融合终止于L1（n = 13）、L2（n = 14）、L3（n = 11）或L4（n = 7）。使用定制的图像处理软件（Biomechlab，法国图卢兹）从三维重建中推断出椎间盘总体积（Vd）和髓核体积（Vn）。在3毫米矢状位切割的快速自旋回波T2加权序列上半自动检测髓核和椎间盘外部轮廓。通过髓核-椎间盘体积比（Vn/Vd）推断椎间盘水合作用。在全脊柱站立位X线片上术前和术后测量矢状位影像学参数（骨盆入射角、骶骨斜率、L1S1腰椎前凸）。根据Stagnara法通过LL/SS比值计算腰骶骨盆协调性。
该队列的平均骨盆入射角为55°（34° - 85°）。手术矫正后，腰椎前凸略有增加3°（p = 0.02），腰骶骨盆协调性从1.37降至1.27（p < 0.01）。当骨盆入射角小于55°（平均骨盆入射角46°）时，未融合腰椎间盘的髓核体积相比术前平均增加了30%，而椎间盘总体积保持稳定。五年随访（n = 13）证实了椎间盘水合比持续改善。当骨盆入射角较高（平均骨盆入射角64°）时，体积变化非常轻微，髓核体积和椎间盘水合比的显著变化仅涉及中腰椎节段（L2L3、L3L4和L4L5）。
这项前瞻性MRI研究显示椎间盘T2高信号有显著且持续的改善，间接表明AIS手术后椎间盘水合含量有所改善。根据骨盆入射角分析椎间盘体积变化表明，这些变化受矢状位脊柱-骨盆排列的影响。骨盆入射角似乎在融合节段椎间盘的稳态中起关键作用，术前规划时应予以考虑。恢复腰骶骨盆协调性可能有助于限制AIS手术后活动节段椎间盘的早期退变改变。当骨盆入射角较高时，水合含量对手术的敏感性较低，提示下腰椎间盘的剪切应力较高。需要更长时间的随访来证实这一假设。
