Kuzhupilly Ranjith R, Lieberman Isador H, McLain Robert F, Valdevit Antonio, Kambic Helen, Richmond Bradford J
Department of Spine Surgery, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Spine (Phila Pa 1976). 2002 May 1;27(9):923-8. doi: 10.1097/00007632-200205010-00007.
Mechanical testing of human lumbar functional spine units was carried out after instrumenting the disc space with femoral ring allografts (FRAs) with and without integrated crossed anterior screws applied into the adjacent bodies.
To assess the stability of FRA construct with and without the integrated crossed anterior screws and to compare that with the intact specimen.
Most modern methods of achieving anterior lumbar intervertebral fusion rely on the use of interbody spacers to restore and maintain intervertebral height, overall alignment, and stability while facilitating arthrodesis. The FRAs have the advantage of biologic compatibility but may not have enough stability when used as stand-alone devices. FRA spacers alone are less stiff in torsion and extension compared with other instrumented constructs. Increased motion could lead to higher failure rates because of graft migration and pseudarthrosis. This makes the use of supplementary anterior or posterior fixation necessary. The current authors hypothesized that the addition of anterior integrated crossed screws applied through the FRA spacer into the adjacent vertebral bodies would increase the stability of the FRA spacer in extension and torsion in the absence of further posterior instrumentation.
Seven fresh-frozen human cadaveric lumbar spine functional spine units were tested applying cantilever bending moments in flexion, lateral bending, torsion, and extension. The specimens were tested in the following sequence: intact, with FRA spacer alone and with FRA spacer and integrated crossed screws. The stiffness of each construct was then compared with the intact specimen. Specimens with obvious deformity on radiographs or dual-energy radiograph absorptiometry t score values <-1.2 were excluded.
The addition of the integrated crossed metal screw system improved the stiffness of the construct by 53% over the intact (P = 0.02) and by 31% over the FRA alone in extension (P = 0.01), whereas it improved the stiffness by 40% over the intact (P = 0.03) and by 18% over the FRA alone in torsion (P = 0.21). The crossed screw system did not improve the stiffness compared with intact in either flexion or lateral bending modes.
Although there is a trend toward improved stability of the FRA spacers in torsion with the addition of the metal screws, this is not statistically significant. The integrated crossed anterior metal screw system significantly improves the stability of the FRA spacers in extension when used for anterior lumbar interbody fusion.
在用带或不带一体式交叉前路螺钉植入相邻椎体的情况下，使用同种异体股骨环（FRA）对人腰椎功能脊柱单元进行器械植入后，进行力学测试。
评估带和不带一体式交叉前路螺钉的FRA结构的稳定性，并将其与完整标本进行比较。
大多数现代实现前路腰椎椎间融合的方法依靠使用椎间融合器来恢复和维持椎间高度、整体对线和稳定性，同时促进关节融合。FRA具有生物相容性的优势，但单独使用时可能没有足够的稳定性。与其他器械化结构相比，单独的FRA融合器在扭转和伸展时刚度较小。由于移植物迁移和假关节形成，运动增加可能导致更高的失败率。这使得有必要使用辅助性前路或后路固定。当前作者假设，通过FRA融合器将前路一体式交叉螺钉添加到相邻椎体中，在没有进一步后路器械植入的情况下，将增加FRA融合器在伸展和扭转时的稳定性。
对7个新鲜冷冻的人尸体腰椎脊柱功能脊柱单元进行测试，在屈曲、侧弯、扭转和伸展时施加悬臂弯矩。标本按以下顺序进行测试：完整、仅使用FRA融合器、使用FRA融合器和一体式交叉螺钉。然后将每个结构的刚度与完整标本进行比较。排除在X线片上有明显畸形或双能X线吸收法t评分值<-1.2的标本。
添加一体式交叉金属螺钉系统后，该结构在伸展时的刚度比完整标本提高了53%（P = 0.02），比仅使用FRA时提高了31%（P = 0.01）；而在扭转时，其刚度比完整标本提高了40%（P = 0.03），比仅使用FRA时提高了18%（P = 0.21）。与完整标本相比，交叉螺钉系统在屈曲或侧弯模式下均未提高刚度。
虽然添加金属螺钉后FRA融合器在扭转时稳定性有提高的趋势，但这在统计学上并不显著。用于前路腰椎椎间融合时，一体式交叉前路金属螺钉系统显著提高了FRA融合器在伸展时的稳定性。
