Biomechanical Analysis of Pedicle Screw Fixation for Thoracolumbar Burst Fractures

Orthopedics. 2016 May 1;39(3):e514-8. doi: 10.3928/01477447-20160427-09. Epub 2016 May 2.


Treatment of unstable thoracolumbar burst fractures remains controversial. Long-segment pedicle screw constructs may be stiffer and impart greater forces on adjacent segments compared with short-segment constructs, which may affect clinical performance and long-term out come. The purpose of this study was to biomechanically evaluate long-segment posterior pedicle screw fixation (LSPF) vs short-segment posterior pedicle screw fixation (SSPF) for unstable burst fractures. Six unembalmed human thoracolumbar spine specimens (T10-L4) were used. Following intact testing, a simulated L1 burst fracture was created and sequentially stabilized using 5.5-mm titanium polyaxial pedicle screws and rods for 4 different constructs: SSPF (1 level above and below), SSPF+L1 (pedicle screw at fractured level), LSPF (2 levels above and below), and LSPF+L1 (pedicle screw at fractured level). Each fixation construct was tested in flexion-extension, lateral bending, and axial rotation; range of motion was also recorded. Two-way repeated-measures analysis of variance was performed to identify differences between treatment groups and functional noninstrumented spine. Short-segment posterior pedicle screw fixation did not achieve stability seen in an intact spine (P<.01), whereas LSPF constructs were significantly stiffer than SSPF constructs and demonstrated more stiffness than an intact spine (P<.01). Pedicle screws at the fracture level did not improve either SSPF or LSPF construct stability (P>.1). Long-segment posterior pedicle screw fixation constructs were not associated with increased adjacent segment motion. Al though the sample size of 6 specimens was small, this study may help guide clinical decisions regarding burst fracture stabilization. [Orthopedics. 2016; 39(3):e514-e518.].

MeSH terms

  • Aged
  • Biomechanical Phenomena
  • Cadaver
  • Female
  • Fracture Fixation, Internal / instrumentation*
  • Humans
  • Lumbar Vertebrae / injuries*
  • Male
  • Middle Aged
  • Pedicle Screws*
  • Range of Motion, Articular
  • Spinal Fractures / diagnosis
  • Spinal Fractures / physiopathology
  • Spinal Fractures / surgery*
  • Spinal Fusion / methods*
  • Thoracic Vertebrae / injuries*