Suh Paul B, Puttlitz Christian, Lewis Chad, Bal B Sonny, McGilvray Kirk
From the Orthopaedic Specialists of North Carolina, Raleigh, NC (Dr. Suh); the Orthopaedic Bioengineering Research Laboratory, Department of Mechanical Engineering, and School of Biomedical Engineering, Colorado State University, Fort Collins, CO (Dr. Puttlitz and Dr. McGilvray); Amedica, Salt Lake City, UT (Dr. Lewis and Dr. Bal); and the Department of Orthopaedic Surgery, University of Missouri, Columbia, MO (Dr. Bal).
J Am Acad Orthop Surg. 2017 Feb;25(2):160-168. doi: 10.5435/JAAOS-D-16-00390.
Interbody cages used in spinal fusion surgery can subside into the adjacent vertebral bodies after implantation, leading to loss of spinal height, malalignment, and possible radicular symptoms. Several factors may contribute to cage subsidence.
This in vitro investigation examined the possible contribution of substrate density, cage contact area (ie, cage footprint), cage filling, cage end plate surface texture, and cage material composition on the magnitude of subsidence. Commercially available cervical interbody cages of two sizes (16 × 12 mm and 17 × 14 mm) were implanted between foam blocks of two different densities and were cyclically loaded. Cages were made of titanium alloy (Ti4Al6V), silicon nitride ceramic (Si3N4), or polyether ether ketone (n = 8 cages of each material type). Additional testing was performed on Si3N4 cages of the smaller size with nontextured surfaces and with filled cores.
Subsidence measurements showed that lower foam density had the greatest influence on subsidence, followed by smaller cage footprint. Cage material had no effect on subsidence. In the additional testing of small-footprint Si3N4 cages, the cages in which the core was filled with a load-bearing porous material had less subsidence in lower-density foam than the cages with an empty core had, whereas cage end plate surface texture had no effect on subsidence.
Ranking of the relative impact of these factors indicated that substrate density had the greatest contribution to the measured subsidence (approximately 1.7 times and approximately 67 times greater than the contributions of cage footprint area and material, respectively). The contribution of cage footprint area to subsidence was found to be 40 times greater than the contribution of cage material to subsidence.
脊柱融合手术中使用的椎间融合器在植入后可能会下沉到相邻椎体中，导致脊柱高度丢失、排列不齐以及可能出现神经根症状。有几个因素可能导致融合器下沉。
本体外研究考察了底物密度、融合器接触面积（即融合器底面面积）、融合器填充物、融合器终板表面纹理以及融合器材料成分对下沉程度的可能影响。将两种尺寸（16×12毫米和17×14毫米）的市售颈椎椎间融合器植入两种不同密度的泡沫块之间，并进行循环加载。融合器由钛合金（Ti4Al6V）、氮化硅陶瓷（Si3N4）或聚醚醚酮制成（每种材料类型的融合器n = 8个）。对较小尺寸、表面无纹理且芯部填充的Si3N4融合器进行了额外测试。
下沉测量结果表明，较低的泡沫密度对下沉影响最大，其次是较小的融合器底面面积。融合器材料对下沉没有影响。在对小底面面积Si3N4融合器的额外测试中，芯部填充有承重多孔材料的融合器在低密度泡沫中的下沉比空芯融合器小；而融合器终板表面纹理对下沉没有影响。
这些因素相对影响的排序表明，底物密度对测量到的下沉贡献最大（分别约为融合器底面面积和材料贡献的1.7倍和约67倍）。发现融合器底面面积对下沉的贡献是融合器材料对下沉贡献的40倍。
