Biomechanical Analysis of Pedicle Screw Fixation for Thoracolumbar Burst Fractures

Abstract

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.].

Extent and location of fixation affects the biomechanical stability of short- or long-segment pedicle screw technique with screwing of fractured vertebra for the treatment of thoracolumbar burst fractures

“…Many studies had compared the biomechanical characteristics and clinical results of SSPF constructs and LSPF constructs without fixation of the fractured level. [ 16 – 21 ] However, no studies have compared the biomechanical characteristics of posterior intermediate screw fixation techniques with SSPF and LSPF with regard to the ROM and VMS of the instrumentations, and no studies have shown the extent and location of fixation. In the present study, fixation models showed significantly less ROM than the intact normal spine model, but there was no significant difference in the mean ROM of all states of motion between the M3-L1 model and the other fixation models except for M5-L2.…”

“…There are many studies that compare the biomechanical characteristics and clinical results of SSPF constructs and long-segment pedicle screw fixation (LSPF) constructs without fixation of the fracture level (2 levels above and below of the fractured vertebra). [ 16 – 21 ] Fixation of the fracture level in an SSPF for thoracolumbar fractures yields similar results as LSPF, such as kyphosis correction and maintenance of the sagittal alignment. This technique saves more vertebral motion segments for the patients.…”

Spinal Reconstruction Techniques for Traumatic Spinal Injuries: A Systematic Review of Biomechanical Studies

“…Two computational biomechanical analysis studies, 6,7 3 biomechanical studies using human spine specimens, 8 -10 2 studies using fresh-frozen bovine spine specimens, 11,12 and 1 study using fresh-frozen porcine spine specimens 13 are included in this analysis. Tables 1 and 2 illustrate the summary of the 8 studies and their significant results.…”

Clinical efficacy and outcome of intelligently inflatable reduction in conjunction with percutaneous pedicle screw fixation for treating thoracolumbar burst fractures

“… 1 Pedicle screw fixation has become a conventional treatment approach for thoracolumbar burst fractures because it provides immediate stability of the three axes of the spinal column after the operation and is associated with fewer complications involving the blood vessels and nerves. 2 , 3 However, operative procedures using pedicle screws in traditional open surgery lead to frequent complications, such as higher bleeding volumes and a longer hospitalization time, because of the need for extensive dissection of the surrounding muscles, fascia, and ligaments. Additionally, they often affect the daily life and work of the patient because of persistent back pain, spinal stiffness, and similar complications.…”