记忆合金椎间融合器对腰椎节段稳定性的生物力学研究

Biomechanical evaluation of lumbar spine segmental stability after inserting of shape memory alloy interbody fusion cage

目的 :评价植入记忆合金椎间融合器 (SMAcage)后腰椎节段的即时稳定性。方法 :8具青年男性新鲜尸体脊柱腰 3、4节段标本 ,制成包括正常腰椎、SMAcage和其它 3种不同类型椎间融合器在内的5种状态的试验模型。测试其前屈 ,后伸 ,左右侧屈和左右旋转方向的运动范围 (ROM )。结果 :植入SMAcage后各向ROM值分别为完整状态的 66%、84%、65 %和 12 5 %,在前屈和侧屈方向上较正常腰椎的稳定性明显提高 (P <0 .0 0 1) ;后伸方向一致 (P =0 .117) ;旋转方向则降低 (P <0 .0 0 1)。与其它 3种融合器的稳定性相比 ,在前屈、后伸方向一致 (P >0 .0 5 ) ;侧屈方向与 2种方形融合器无明显差别 (P =0 .12 2 ) ,高于螺纹状融合器 (P =0 .0 0 4) ;旋转方向与螺纹状融合器一致 (P =0 .861) ,高于 2种方形融合器(P <0 .0 5 )。结论 :SMAcage具有独特的构型和稳定机制 ,其生物力学稳定性高于一般螺纹状和方椎间融合器。

Objective: To evaluate the biomechanical stability of lumbar functional segment unit after insertion with a newly designed shape memory alloy cage(SMAcage) and compare with different lumbar interbody fusion cage. Methods: Eight young male cadavers' lumbar spine specimens(L3/4) was used to detect the range of motion(ROM) of SMAcage with three differential cages .The specimens were divided into five groups: ⑴control (intact); ⑵SMAcage; ⑶threaded cage ;⑷hollow rectangle cage; ⑸solid rectangle cage. Different cages were inserted randomly. All groups were tested using a spinal three dimensional anlysis system. Results: The average ROM of SMAcage were 6.2°,4.6°,12.8°and 9.6°in flexion, extension, lateral bending and torsion, respectively. The SMAcages group significantly decreased the intervertebral movement in flexion and lateral bending with a ROM of 66% and 65% to intact model( P <0.05 ). The median cage movement of extension were 84% of intact movement which was not a significant difference( P =0.117 ). The range of motion in torsion increased 25% to intact , which was significantly different from control group( P <0.05 ). SMAcage had an equal ROM in flexion and extension with three different cages( P <0.05 ). The stability of SMAcage in lateral bending was higher than that of threaded cage, while the stability in torsion was higher than that of rectangle cages. Conclusion: The SMAcage has a good biomechanical stability because its unique design and special stability mechanism. It can be apply to clinical in the view of its biomechanical characters.