Background The mechanical response of the spinal cord during burst fracture was seldom quantitatively addressed and only few studies look into the internal strain of the white and grey matters within the spinal cord during thoracolumbar burst fracture (TLBF). The aim of the study is to investigate the mechanical response of the spinal cord during TLBF and correlate the percent canal compromise (PCC) with the strain in the spinal cord. Methodology/Principal Findings A three-dimensional (3D) finite element (FE) model of human T12-L1 spinal cord with visco-elastic property was generated based on the transverse sections images of spinal cord, and the model was validated against published literatures under static uniaxial tension and compression. With the validated model, a TLBF simulation was performed to compute the mechanical strain in the spinal cord with the PCC. Linear regressions between PCC and strain in the spinal cord show that at the initial stage, with the PCC at 20%, and 45%, the corresponding mechanical strains in ventral grey, dorsal grey, ventral white, dorsal white matters were 0.06, 0.04, 0.12, 0.06, and increased to 0.14, 0.12, 0.23, and 0.13, respectively. At the recoiled stage, when the PCC was decreased from 45% to 20%, the corresponding strains were reduced to 0.03, 0.02, 0.04 and 0.03. The strain was correlated well with PCC. Conclusions/Significance The simulation shows that the strain in the spinal cord correlated well with the PCC, and the mechanical strains in the ventral regions are higher than those in the dorsal regions of spinal cord tissue during burst fracture, suggesting that the ventral regions of the spinal cord may susceptible to injury than the dorsal regions.
References
[1]
Wood K, Buttermann G, Mehbod A, Garvey T, Jhanjee R, et al. (2003) Operative compared with nonoperative treatment of a thoracolumbar burst fracture without neurological deficit. A prospective, randomized study. J Bone Joint Surg Am 85-A: 773–781.
[2]
Bain AC, Meaney DF (2000) Tissue-level thresholds for axonal damage in an experimental model of central nervous system white matter injury. J Biomech Eng 122: 615–622.
[3]
Zhang L, Yang KH, King AI (2004) A proposed injury threshold for mild traumatic brain injury. J Biomech Eng 126: 226–236.
[4]
LeMay DR, Gehua L, Zelenock GB, D'Alecy LG (1988) Insulin administration protects neurologic function in cerebral ischemia in rats. Stroke 19: 1411–1419.
[5]
Rasmussen PA, Rabin MH, Mann DC, Perl JR 2nd, Lorenz MA, et al. (1994) Reduced transverse spinal area secondary to burst fractures: is there a relationship to neurologic injury? J Neurotrauma 11: 711–720.
[6]
Zhao X, Fang XQ, Zhao FD, Fan SW (2010) Traumatic canal stenosis should not be an indication for surgical decompression in thoracolumbar burst fracture. Med Hypotheses 75: 550–552.
[7]
Hashimoto T, Kaneda K, Abumi K (1988) Relationship between traumatic spinal canal stenosis and neurologic deficits in thoracolumbar burst fractures. Spine (Phila Pa 1976) 13: 1268–1272.
[8]
Fontijne WP, de Klerk LW, Braakman R, Stijnen T, Tanghe HL, et al. (1992) CT scan prediction of neurological deficit in thoracolumbar burst fractures. J Bone Joint Surg Br 74: 683–685.
[9]
Panjabi MM, Oxland TR, Lin RM, McGowen TW (1994) Thoracolumbar burst fracture. A biomechanical investigation of its multidirectional flexibility. Spine (Phila Pa 1976) 19: 578–585.
[10]
Wilcox RK, Boerger TO, Allen DJ, Barton DC, Limb D, et al. (2003) A dynamic study of thoracolumbar burst fractures. J Bone Joint Surg Am 85-A: 2184–2189.
[11]
Dai LY, Wang XY, Jiang LS (2008) Evaluation of traumatic spinal canal stenosis in thoracolumbar burst fractures. A comparison of three methods for measuring the percent canal occlusion. Eur J Radiol 67: 526–530.
[12]
Boerger TO, Limb D, Dickson RA (2000) Does ‘canal clearance’ affect neurological outcome after thoracolumbar burst fractures? J Bone Joint Surg Br 82: 629–635.
[13]
Mikles MR, Stchur RP, Graziano GP (2004) Posterior instrumentation for thoracolumbar fractures. J Am Acad Orthop Surg 12: 424–435.
[14]
Tencer AF, Allen BL Jr, Ferguson RL (1985) A biomechanical study of thoracolumbar spine fractures with bone in the canal. Part III. Mechanical properties of the dura and its tethering ligaments. Spine (Phila Pa 1976) 10: 741–747.
[15]
Greaves CY, Gadala MS, Oxland TR (2008) A three-dimensional finite element model of the cervical spine with spinal cord: an investigation of three injury mechanisms. Ann Biomed Eng 36: 396–405.
[16]
Li XF, Dai LY (2009) Three-dimensional finite element model of the cervical spinal cord: preliminary results of injury mechanism analysis. Spine (Phila Pa 1976) 34: 1140–1147.
[17]
Sparrey CJ, Manley GT, Keaveny TM (2009) Effects of white, grey, and pia mater properties on tissue level stresses and strains in the compressed spinal cord. J Neurotrauma 26: 585–595.
[18]
Shirado O (1993) [Thoracolumbar burst fractures; an experimental study on cadaveric spines and finite element method]. Nippon Seikeigeka Gakkai Zasshi 67: 644–654.
[19]
Wilcox RK, Allen DJ, Hall RM, Limb D, Barton DC, et al. (2004) A dynamic investigation of the burst fracture process using a combined experimental and finite element approach. Eur Spine J 13: 481–488.
[20]
Qiu TX, Tan KW, Lee VS, Teo EC (2006) Investigation of thoracolumbar T12-L1 burst fracture mechanism using finite element method. Med Eng Phys 28: 656–664.
[21]
Drake, Richard L (2010) Gray's anatomy for students, 2nd edition. Philadelphia, Churchill Livingstone/Elsevier
[22]
Ko HY, Park JH, Shin YB, Baek SY (2004) Gross quantitative measurements of spinal cord segments in human. Spinal Cord 42: 35–40.
[23]
Schoenen J, Faull RLM (2004) Spinal cord: cyto and chemoarchitecture, in: The human nervous system, 2nd edition. Boston, Elsevier Academic press.
[24]
Tan SH, Teo EC, Chua HC (2002) Quantitative three-dimensional anatomy of lumbar vertebrae in Singaporean Asians. Eur Spine J 11: 152–158.
[25]
Panjabi MM, Goel V, Oxland T, Takata K, Duranceau J, et al. (1992) Human lumbar vertebrae. Quantitative three-dimensional anatomy. Spine (Phila Pa 1976) 17: 299–306.
[26]
Ozawa H, Matsumoto T, Ohashi T, Sato M, Kokubun S (2004) Mechanical properties and function of the spinal pia mater. J Neurosurg Spine 1: 122–127.
[27]
Bilston LE, Thibault LE (1996) The mechanical properties of the human cervical spinal cord in vitro. Ann Biomed Eng 24: 67–74.
[28]
Wilcox RK, Bilston LE, Barton DC, Hall RM (2003) Mathematical model for the viscoelastic properties of dura mater. J Orthop Sci 8: 432–434.
[29]
Hung TK, Lin HS, Albin MS, Bunegin L, Jannetta PJ (1979) The standardization of experimental impact injury to the spinal cord. Surg Neurol 11: 470–477.
[30]
Hung TK, Lin HS, Bunegin L, Albin MS (1982) Mechanical and neurological response of cat spinal cord under static loading. Surg Neurol 17: 213–217.
[31]
Clarke EC, Cheng S, Bilston LE (2009) The mechanical properties of neonatal rat spinal cord in vitro, and comparisons with adult. J Biomech 42: 1397–1402.
[32]
Ichihara K, Taguchi T, Shimada Y, Sakuramoto I, Kawano S, et al. (2001) Gray matter of the bovine cervical spinal cord is mechanically more rigid and fragile than the white matter. J Neurotrauma 18: 361–367.
[33]
Coats B, Margulies SS (2006) Material properties of porcine parietal cortex. J Biomech 39: 2521–2525.
[34]
Sparrey CJ, Manley GT, Keaveny TM (2009) Effects of white, grey, and pia mater properties on tissue level stresses and strains in the compressed spinal cord. J Neurotrauma 26: 585–595.
[35]
Mohanty SP, Bhat NS, Abraham R, Ishwara Keerthi C (2008) Neurological deficit and canal compromise in thoracolumbar and lumbar burst fractures. J Orthop Surg (Hong Kong) 16: 20–23.
[36]
Shuman WP, Rogers JV, Sickler ME, Hanson JA, Crutcher JP, et al. (1985) Thoracolumbar burst fractures: CT dimensions of the spinal canal relative to postsurgical improvement. AJR Am J Roentgenol 145: 337–341.
[37]
Limb D, Shaw DL, Dickson RA (1995) Neurological injury in thoracolumbar burst fractures. J Bone Joint Surg Br 77: 774–777.
[38]
Meves R, Avanzi O (2006) Correlation among canal compromise, neurologic deficit, and injury severity in thoracolumbar burst fractures. Spine (Phila Pa 1976) 31: 2137–2141.
[39]
Christ AF, Franze K, Gautier H, Moshayedi P, Fawcett J, et al. (2010) Mechanical difference between white and gray matter in the rat cerebellum measured by scanning force microscopy. J Biomech 43: 2986–2992.
