Biomechanical evaluation of a simulated T-9 burst fracture of the thoracic spine with an intact rib cage

Laboratory investigation

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  • 1 Spine Research Lab, Lutheran Hospital; and
  • | 2 Center for Spine Health, Neurological Institute, and
  • | 3 Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio
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Object

Classic biomechanical models have used thoracic spines disarticulated from the rib cage, but the biomechanical influence of the rib cage on fracture biomechanics has not been investigated. The well-accepted construct for stabilizing midthoracic fractures is posterior instrumentation 3 levels above and 2 levels below the injury. Short-segment fixation failure in thoracolumbar burst fractures has led to kyphosis and implant failure when anterior column support is lacking. Whether shorter constructs are viable in the midthoracic spine is a point of controversy. The objective of this study was the biomechanical evaluation of a burst fracture at T-9 with an intact rib cage using different fixation constructs for stabilizing the spine.

Methods

A total of 8 human cadaveric spines (C7–L1) with intact rib cages were used in this study. The range of motion (ROM) between T-8 and T-10 was the outcome measure. A robotic spine testing system was programmed to apply pure moment loads (± 5 Nm) in lateral bending, flexion-extension, and axial rotation to whole thoracic specimens. Intersegmental rotations were measured using an optoelectronic system. Flexibility tests were conducted on intact specimens, then sequentially after surgically induced fracture at T-9, and after each of 4 fixation construct patterns. The 4 construct patterns were sequentially tested in a nondestructive protocol, as follows: 1) 3 above/2 below (3A/2B); 2) 1 above/1 below (1A/1B); 3) 1 above/1 below with vertebral body augmentation (1A/1B w/VA); and 4) vertebral body augmentation with no posterior instrumentation (VA). A repeated-measures ANOVA was used to compare the segmental motion between T-8 and T-10 vertebrae.

Results

Mean ROM increased by 86%, 151%, and 31% after fracture in lateral bending, flexion-extension, and axial rotation, respectively. In lateral bending, there was significant reduction compared with intact controls for all 3 instrumented constructs: 3A/2B (−92%, p = 0.0004), 1A/1B (−63%, p = 0.0132), and 1A/1B w/VA (−66%, p = 0.0150). In flexion-extension, only the 3A/2B pattern showed a significant reduction (−90%, p = 0.011). In axial rotation, motion was significantly reduced for the 3 instrumented constructs: 3A/2B (−66%, p = 0.0001), 1A/1B (−53%, p = 0.0001), and 1A/1B w/VA (−51%, p = 0.0002). Between the 4 construct patterns, the 3 instrumented constructs (3A/2B, 1A/1B, and 1A/1B w/VA) showed comparable stability in all 3 motion planes.

Conclusions

This study showed no significant difference in the stability of the 3 instrumented constructs tested when the rib cage is intact. Fractures that might appear more grossly unstable when tested in the disarticulated spine may be bolstered by the ribs. This may affect the extent of segmental spinal instrumentation needed to restore stability in some spine injuries. While these initial findings suggest that shorter constructs may adequately stabilize the spine in this fracture model, further study is needed before these results can be extrapolated to clinical application.

Abbreviations used in this paper:

PLC = posterior ligamentous complex; ROM = range of motion; VA = vertebral augmentation; 1A/1B = 1 above/1 below; 1A/1B w/VA = 1 above/1 below with vertebral augmentation; 3A/2B = 3 above/2 below.

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  • 1

    Acosta FL Jr, , Buckley JM, , Xu Z, , Lotz JC, & Ames CP: Biomechanical comparison of three fixation techniques for unstable thoracolumbar burst fractures. Laboratory investigation. J Neurosurg Spine 8:341346, 2008

    • Search Google Scholar
    • Export Citation
  • 2

    Alanay A, , Acaroglu E, , Yazici M, , Oznur A, & Surat A: Shortsegment pedicle instrumentation of thoracolumbar burst fractures: does transpedicular intracorporeal grafting prevent early failure?. Spine (Phila Pa 1976) 26:213217, 2001

    • Search Google Scholar
    • Export Citation
  • 3

    An HS, , Singh K, , Vaccaro AR, , Wang G, , Yoshida H, & Eck J, et al.: Biomechanical evaluation of contemporary posterior spinal internal fixation configurations in an unstable burst-fracture calf spine model: special references of hook configurations and pedicle screws. Spine (Phila Pa 1976) 29:257262, 2004

    • Search Google Scholar
    • Export Citation
  • 4

    Baaj AA, , Reyes PM, , Yaqoobi AS, , Uribe JS, , Vale FL, & Theodore N, et al.: Biomechanical advantage of the index-level pedicle screw in unstable thoracolumbar junction fractures. Laboratory investigation. J Neurosurg Spine 14:192197, 2011

    • Search Google Scholar
    • Export Citation
  • 5

    Berg EE: The sternal-rib complex. A possible fourth column in thoracic spine fractures. Spine (Phila Pa 1976) 18:19161919, 1993

  • 6

    Brasiliense LBC, , Lazaro BCR, , Reyes PM, , Dogan S, , Theodore N, & Crawford NR: Biomechanical contribution of the rib cage to thoracic stability. Spine (Phila Pa 1976) 36:E1686E1693, 2011

    • Search Google Scholar
    • Export Citation
  • 7

    Busscher I, , van der Veen AJ, , van Dieën JH, , Kingma I, , Verkerke GJ, & Veldhuizen AG: In vitro biomechanical characteristics of the spine: a comparison between human and porcine spinal segments. Spine (Phila Pa 1976) 35:E35E42, 2010

    • Search Google Scholar
    • Export Citation
  • 8

    Gurr KR, , McAfee PC, & Shih CM: Biomechanical analysis of anterior and posterior instrumentation systems after corpectomy. A calf-spine model. J Bone Joint Surg Am 70:11821191, 1988

    • Search Google Scholar
    • Export Citation
  • 9

    Kallemeier PM, , Beaubien BP, , Buttermann GR, , Polga DJ, & Wood KB: In vitro analysis of anterior and posterior fixation in an experimental unstable burst fracture model. J Spinal Disord Tech 21:216224, 2008

    • Search Google Scholar
    • Export Citation
  • 10

    Liao JC, , Fan KF, , Chen WJ, , Chen LH, & Kao HK: Transpedicular bone grafting following short-segment posterior instrumentation for acute thoracolumbar burst fracture. Orthopedics 32:493, 2009

    • Search Google Scholar
    • Export Citation
  • 11

    Mageswaran P, , McLain RF, , Colbrunn R, , Bonner T, , Hothem E, & Bartsch A: Plate fixation in the cervical spine: traditional paramedian screw configuration compared with unique unilateral configuration. Laboratory investigation. J Neurosurg Spine 18:575581, 2013

    • Search Google Scholar
    • Export Citation
  • 12

    Mageswaran P, , Techy F, , Colbrunn RW, , Bonner TF, & McLain RF: Hybrid dynamic stabilization: a biomechanical assessment of adjacent and supraadjacent levels of the lumbar spine. Laboratory investigation. J Neurosurg Spine 17:232242, 2012

    • Search Google Scholar
    • Export Citation
  • 13

    Mahar A, , Kim C, , Wedemeyer M, , Mitsunaga L, , Odell T, & Johnson B, et al.: Short-segment fixation of lumbar burst fractures using pedicle fixation at the level of the fracture. Spine (Phila Pa 1976) 32:15031507, 2007

    • Search Google Scholar
    • Export Citation
  • 14

    McLain RF: The biomechanics of long versus short fixation for thoracolumbar spine fractures. Spine (Phila Pa 1976) 31:11 Suppl S70S79, 2006

    • Search Google Scholar
    • Export Citation
  • 15

    McLain RF, , Sparling E, & Benson DR: Early failure of short-segment pedicle instrumentation for thoracolumbar fractures. A preliminary report. J Bone Joint Surg Am 75:162167, 1993

    • Search Google Scholar
    • Export Citation
  • 16

    Mermelstein LE, , McLain RF, & Yerby SA: Reinforcement of thoracolumbar burst fractures with calcium phosphate cement. A biomechanical study. Spine (Phila Pa 1976) 23:664671, 1998

    • Search Google Scholar
    • Export Citation
  • 17

    Oda I, , Abumi K, , Cunningham BW, , Kaneda K, & McAfee PC: An in vitro human cadaveric study investigating the biomechanical properties of the thoracic spine. Spine (Phila Pa 1976) 27:E64E70, 2002

    • Search Google Scholar
    • Export Citation
  • 18

    Parker JW, , Lane JR, , Karaikovic EE, & Gaines RW: Successful short-segment instrumentation and fusion for thoracolumbar spine fractures: a consecutive 4 1/2-year series. Spine (Phila Pa 1976) 25:11571170, 2000

    • Search Google Scholar
    • Export Citation
  • 19

    Stambough JL: Posterior instrumentation for thoracolumbar trauma. Clin Orthop Relat Res 335 7388, 1997

  • 20

    Techy F, , Mageswaran P, , Colbrunn RW, , Bonner TF, & McLain RF: Properties of an interspinous fixation device (ISD) in lumbar fusion constructs: a biomechanical study. Spine J 13:572579, 2013

    • Search Google Scholar
    • Export Citation
  • 21

    Verlaan JJ, , Dhert WJ, , Verbout AJ, & Oner FC: Balloon vertebroplasty in combination with pedicle screw instrumentation: a novel technique to treat thoracic and lumbar burst fractures. Spine (Phila Pa 1976) 30:E73E79, 2005

    • Search Google Scholar
    • Export Citation
  • 22

    Wahba GM, , Bhatia N, , Bui CN, , Lee KH, & Lee TQ: Biomechanical evaluation of short-segment posterior instrumentation with and without crosslinks in a human cadaveric unstable thoracolumbar burst fracture model. Spine (Phila Pa 1976) 35:278285, 2010

    • Search Google Scholar
    • Export Citation
  • 23

    Watkins R IV, , Watkins R III, , Williams L, , Ahlbrand S, , Garcia R, & Karamanian A, et al.: Stability provided by the sternum and rib cage in the thoracic spine. Spine (Phila Pa 1976) 30:12831286, 2005

    • Search Google Scholar
    • Export Citation

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