Finite-element analysis of a novel posterior atlantoaxial restricted non-fusion fixation system

doi:10.3969/j.issn.2095-4344.2017.03.011

Abstract

Abstract:

BACKGROUND: Atlantoaxial fusion is currently the main surgical treatment of atlantoaxial dislocation, but the premise is at the expense of atlantoaxial range of motion, especially the rotation motion. Restricted non-fusion fixation is a method that can maintain the atlantoaxial stability, while retain the atlantoaxial range of motion. Further research should be performed to compare the biomechanical characteristics between the two methods.

OBJECTIVE: To develop a three-dimensional finite element model of atlantoaxial instability, compare and determine the biomechanical properties of posterior atlantoaxial restricted non-fusion fixation system and posterior atlantoaxial screw-rod fixation system.

METHODS: A verified intact finite element upper cervical (C₀-C₃) model was established and analyzed by Simpleware 3.0, Geomagic 8.0, Hypermesh 10.0, Abaqus 6.9, and Rhino 4.0 softwares based on the CT data collected from a 31-year-old healthy male volunteer. The moment couple of 1.5 N•m was loaded, which made the model movement in flexion-extension, lateral bending, and rotating direction, respectively. The range of motion was recorded and compared with the in vitro biomechanical experimental data to verify the effectiveness of the model. The ranges of motion of the posterior atlantoaxial restricted non-fusion fixation system model and the posterior atlantoaxial screw-rod fixation system model were analyzed using the finite element method under flexion, extension, lateral bending, and axial rotation; meanwhile, stress nephograms of the posterior atlantoaxial restricted non-fusion fixation system model were observed.

RESULTS AND CONCLUSION: (1) There were 206 747 elements and 72 500 nodes in the intact model of upper cervical spine (C₀-C₃) in this experiment, and the range of motion of intact model validated with the reported cadaveric experimental data. (2) The range of motion of the posterior atlantoaxial restricted non-fusion fixation system group was similar to which of the posterior atlantoaxial screw-rod fixation system group in flexion-extension direction. (3) In lateral bending direction, the range of motion of the posterior atlantoaxial restricted non-fusion fixation system model was obviously limited, respectively. The range of motion of the posterior atlantoaxial restricted non-fusion fixation system model was larger than that of the atlantoaxial dislocation model and basically same as that of the normal atlantoaxial model. (4) As to the rotating direction, the range of motion of the posterior atlantoaxial restricted non-fusion fixation system mainly disappeared at the atlantoaxial segment; by contrast, a majority of rotating motion was still retained in the posterior atlantoaxial restricted non-fusion fixation system group. (5) The stress concentration occurred in the contact part between the screw and the connecting rod in posterior atlantoaxial restricted non-fusion fixation system model. (6) Results suggest that posterior atlantoaxial restricted non-fusion fixation system is effective and useful for atlantoaxial fixation. It not only restricted atlantoaxial flexion-extension, but also preserved axial rotation and lateral bending at the atlantoaxial joint.

中国组织工程研究杂志出版内容重点：人工关节；骨植入物；脊柱；骨折；内固定；数字化骨科；组织工程

Key words: Axis, Cervical Vertebrae, Internal Fixators, Biomechanics , Finite Element Analysis, Tissue

CLC Number:

R318

Du Shi-yao, Zhou Feng-jin, Ni Bin, Chen Bo, Chen Jin-shui. Finite-element analysis of a novel posterior atlantoaxial restricted non-fusion fixation system[J]. Chinese Journal of Tissue Engineering Research, 2017, 21(3): 383-389.

Figures/Tables 3

2.1 三维有限元模型的有效性验证正常寰枢椎几何实体模型、韧带加载及网格划分后的上颈椎有限元模型包括206 747单元，72 500个节点，外观逼真，几何相似性好(图2，3)。经验证：模型中各功能单位的活动度与Panjabi等[17，22-23]的实验结果相符合(表4)，三维有限元应力云图与临床实际相符合。寰枢椎脱位模型及寰枢椎传统钉棒内固定系统的有限元模型均得到验证[14]。新型寰枢椎非融合限制性内固定系统的各个部件的节点和单元数见表5。 2.2 不同情况下寰枢椎运动节段的活动度比较正常寰枢椎模型屈伸活动度是20.4°，单侧左右侧屈活动度是3.6°，单侧轴向旋转活动度是33.9°(表6)，可见寰枢椎脱位模型的前屈后伸、左右侧屈及轴向旋转的活动度明显增加。限制性非融合内固定系统模型的寰枢椎前屈、后伸的活动度与寰枢椎传统钉棒系统的结果接近，均较正常寰枢椎和寰枢椎脱位模型明显缩小(图4A，B)；传统钉棒系统模型的侧向屈曲活动度明显减少，而限制性非融合内固定系统的侧向屈曲活动度较寰枢椎脱位模型稍增加，但与正常模型相近(图4C，D)；而在轴向旋转工况下，传统钉棒内固定系统模型的寰枢椎轴向旋转活动度基本为零，而限制性非融合内固定系统模型的轴向旋转活动度虽然比正常模型稍减少，仍保留大部分活动度(图4E，F)。 2.3 非融合内固定的应力云图在前屈工况下，应力集中于双侧寰枢椎椎弓根螺钉尾部与寰枢椎交界面处及万向固定杆腹侧与寰椎横向连接棒交接处(图5)。在后伸工况下，应力主要集中于双侧寰枢椎椎弓根螺钉尾部与寰枢椎交界面处(图6)，部分应力集中于寰枢椎椎弓根与其相应连接棒的连接处。在左右侧屈工况下，应力集中部位在于屈曲侧枢椎椎弓根螺钉和连接棒连接处及C2-3侧块关节(图7)。在左右轴向旋转工况下，应力主要集中于双侧寰椎椎弓根螺钉的头端(图8)。 "

References

[1] Robertson PA, Tsitsopoulos PP, Voronov LI, et al. Biomechanical investigation of a novel integrated device for intra-articular stabilization of the C1-C2 (atlantoaxial) joint. Spine J. 2012;12: 136-142.

[2] Roy AK, Miller BA, Holland CM, et al. Magnetic resonance imaging of traumatic injury to the craniovertebral junction: a case-based review. Neurosurg Focus. 2015;38: E3.

[3] Elliott RE, Tanweer O, Boah A, et al. Atlantoaxial fusion with screw-rod constructs: meta-analysis and review of literature. World Neurosurg. 2014;81: 411-421.

[4] Ryang YM, Torok E, Janssen I, et al. Early Morbidity and Mortality in 50 Very Elderly Patients After Posterior Atlantoaxial Fusion for Traumatic Odontoid Fractures. World Neurosurg. 2016;87: 381-391.

[5] Du JY, Aichmair A, Kueper J, et al. Biomechanical analysis of screw constructs for atlantoaxial fixation in cadavers: a systematic review and meta-analysis. J Neurosurg Spine. 2015; 22: 151-161.

[6] Bhowmick DA, Benzel EC. Posterior atlantoaxial fixation with screw-rod constructs: safety, advantages, and shortcomings. World Neurosurg. 2014;81: 288-289.

[7] Ni B, Guo Q, Lu X, et al. Posterior reduction and temporary fixation for odontoid fracture: a salvage maneuver to anterior screw fixation. Spine (Phila Pa 1976). 2015;40: E168-174.

[8] Lubelski D, Benzel EC. C1-C2 fusion: promoting stability, reducing morbidity. World Neurosurg. 2014;82: 1052-1054.

[9] Lenehan B, Guerin S, Street J, et al. Lateral C1-C2 dislocation complicating a type II odontoid fracture. J Clin Neurosci. 2010;17: 947-949.

[10] Bogduk N, Mercer S. Biomechanics of the cervical spine. I: Normal kinematics. Clin Biomech (Bristol, Avon). 2000;15: 633-648.

[11] Kumaresan S, Yoganandan N, Pintar FA. Finite element analysis of anterior cervical spine interbody fusion. Biomed Mater Eng. 1997;7: 221-230.

[12] Ng HW, Teo EC. Nonlinear finite-element analysis of the lower cervical spine (C4-C6) under axial loading. J Spinal Disord. 2001;14: 201-210.

[13] Zhang QH, Teo EC, Ng HW, et al. Finite element analysis of moment-rotation relationships for human cervical spine. J Biomech. 2006; 39: 189-193.

[14] 陈金水,倪斌,陈博,等.寰枢椎脱位三维非线性有限元模型的建立和分析[J].中国脊柱脊髓杂志,2010,20(9):749-753.

[15] 郭群峰,陈方经,倪斌,等.带有颅底的全颈椎三维有限元模型的建立及分析[J]. 中国脊柱脊髓杂志,2014,24(6): 550-554.

[16] Hu Y, Dong WX, Hann S, et al. Construction of Finite Element Model for an Artificial Atlanto-Odontoid Joint Replacement and Analysis of Its Biomechanical Properties. Turk Neurosurg. 2016;26: 430-436.

[17] Brolin K, Halldin P. Development of a finite element model of the upper cervical spine and a parameter study of ligament characteristics. Spine (Phila Pa 1976). 2004;29: 376-385.

[18] El-Rich M, Arnoux PJ, Wagnac E, et al. Finite element investigation of the loading rate effect on the spinal load-sharing changes under impact conditions. J Biomech. 2009;42: 1252-1262.

[19] Zhang B, Liu H, Cai X, et al. Biomechanical Comparison of Modified TARP Technique Versus Modified Goel Technique for the Treatment of Basilar Invagination: A Finite Element Analysis. Spine (Phila Pa 1976). 2016;41: E459-466.

[20] Tan M, Wang H, Wang Y, et al. Morphometric evaluation of screw fixation in atlas via posterior arch and lateral mass. Spine (Phila Pa 1976). 2003;28: 888-895.

[21] Ebraheim N, Rollins JR Jr, Xu R, et al. Anatomic consideration of C2 pedicle screw placement. Spine (Phila Pa 1976). 1996;21: 691-695.

[22] Panjabi M, Dvorak J, Crisco JJ 3rd, et al. Effects of alar ligament transection on upper cervical spine rotation. J Orthop Res. 1991;9: 584-593.

[23] Zhang H, Bai J. Development and validation of a finite element model of the occipito-atlantoaxial complex under physiologic loads. Spine (Phila Pa 1976). 2007;32: 968-974.

[24] Goel A, Nadkarni T, Shah A, et al. Radiologic Evaluation of Basilar Invagination Without Obvious Atlantoaxial Instability (Group B Basilar Invagination): Analysis Based on a Study of 75 Patients. World Neurosurg. 2016;95: 375-382.

[25] Huang DG, Hao DJ, He BR, et al. Posterior atlantoaxial fixation: a review of all techniques. Spine J. 2015;15: 2271-2281.

[26] Lopez AJ, Scheer JK, Leibl KE, et al. Anatomy and biomechanics of the craniovertebral junction. Neurosurg Focus. 2015;38: E2.

[27] Huang DG, Hao DJ, Li GL, et al. C2 nerve dysfunction associated with C1 lateral mass screw fixation. Orthop Surg. 2014;6: 269-273.

[28] 马向阳,杨进城,尹庆水,等.后路寰枢椎钉棒固定非融合治疗新鲜Ⅱ型齿状突骨折保留寰枢椎旋转功能的临床初探[J].中国脊柱脊髓杂志, 2013, 23(5): 411-415.

[29] 周风金,倪斌,刘洪超,等.一种后路寰枢椎动态内固定系统的研制及其解剖学研究[J].脊柱外科杂志,2011,9(3): 183-187.

[30] Cai X, He X, Li H, et al. Total atlanto-odontoid joint arthroplasty system: a novel motion preservation device for atlantoaxial instability after odontoidectomy. Spine (Phila Pa 1976).2013;38: E451-457.

[31] Kato K, Yokoyama T, Ono A, et al. Novel motion preservation device for atlantoaxial instability. J Spinal Disord Tech. 2013;26: E107-111.

[32] Chen J, Zhou F, Ni B, et al. New Posterior Atlantoaxial Restricted Non-Fusion Fixation for Atlantoaxial Instability: A Biomechanical Study. Neurosurgery. 2016;78: 735-741.

[33] Ji W, Zheng M, Kong G, et al. Computed Tomographic Morphometric Analysis of Pediatric C1 Posterior Arch Crossing Screw Fixation for Atlantoaxial Instability. Spine (Phila Pa 1976). 2016;41: 91-96.

[34] Yu HM, Malhotra K, Butler JS, et al. Anterior and posterior fixation for delayed treatment of posterior atlantoaxial dislocation without fracture. BMJ Case Rep. 2015;2015. pii: bcr2015212436.

[35] Srivastava SK, Aggarwal RA, Nemade PS, et al. Single-stage anterior release and posterior instrumented fusion for irreducible atlantoaxial dislocation with basilar invagination. Spine J. 2016;16: 1-9.

[36] Platzer P, Thalhammer G, Krumboeck A, et al. Plate fixation of odontoid fractures without C1-C2 arthrodesis: practice of a novel surgical technique for stabilization of odontoid fractures, including the opportunity to extend the fixation to C3. Neurosurgery. 2009;64: 726-733; discussion 733.

[37] Lu B, He X, Zhao CG, et al. Biomechanical study of artificial atlanto-odontoid joint. Spine (Phila Pa 1976). 2009;34: 1893-1899.

[38] Ma X, Peng X, Xiang H, et al. A finite element modeling of posterior atlantoaxial fixation and biomechanical analysis of C2 intralaminar screw fixation. Chin Med J (Engl). 2014;127: 1266-1271.

[39] Cai X, Yu Y, Liu Z, et al. Three-dimensional finite element analysis of occipitocervical fixation using an anterior occiput-to-axis locking plate system: a pilot study. Spine J. 2014;14: 1399-1409.

[40] Zhang BC, Liu HB, Cai XH, et al. Biomechanical comparison of a novel transoral atlantoaxial anchored cage with established fixation technique - a finite element analysis. BMC Musculoskelet Disord. 2015;16: 261.