Comprehensive biomechanical analysis of three reconstruction techniques following total sacrectomy: an in vitro human cadaveric model

Mohamed Macki, Rafael De la Garza-Ramos, Ashley A. Murgatroyd, Kenneth P. Mullinix, Xiaolei Sun, Bryan W. Cunningham, Brandon A. McCutcheon, Mohamad Bydon, Ziya L. Gokaslan

Research output: Contribution to journalArticle

Abstract

OBJECTIVE Aggressive sacral tumors often require en bloc resection and lumbopelvic reconstruction. Instrumentation failure and pseudarthrosis remain a clinical concern to be addressed. The objective in this study was to compare the biomechanical stability of 3 distinct techniques for sacral reconstruction in vitro. METHODS In a human cadaveric model study, 8 intact human lumbopelvic specimens (L2-pelvis) were tested for flexion-extension range of motion (ROM), lateral bending, and axial rotation with a custom-designed 6-df spine simulator as well as axial compression stiffness with the MTS 858 Bionix Test System. Biomechanical testing followed this sequence: 1) intact spine; 2) sacrectomy (no testing); 3) Model 1 (L3-5 transpedicular instrumentation plus spinal rods anchored to iliac screws); 4) Model 2 (addition of transiliac rod); and 5) Model 3 (removal of transiliac rod; addition of 2 spinal rods and 2 S-2 screws). Range of motion was measured at L4-5, L5-S1/cross-link, L5-right ilium, and L5-left ilium. RESULTS Flexion-extension ROM of the intact specimen at L4-5 (6.34° ± 2.57°) was significantly greater than in Model 1 (1.54° ± 0.94°), Model 2 (1.51° ± 1.01°), and Model 3 (0.72° ± 0.62°) (p < 0.001). Flexion-extension at both the L5-right ilium (2.95° ± 1.27°) and the L5-left ilium (2.87° ± 1.40°) for Model 3 was significantly less than the other 3 cohorts at the same level (p = 0.005 and p = 0.012, respectively). Compared with the intact condition, all 3 reconstruction groups statistically significantly decreased lateral bending ROM at all measured points. Axial rotation ROM at L4-5 for Model 1 (2.01° ± 1.39°), Model 2 (2.00° ± 1.52°), and Model 3 (1.15° ± 0.80°) was significantly lower than the intact condition (5.02° ± 2.90°) (p < 0.001). Moreover, axial rotation for the intact condition and Model 3 at L5-right ilium (2.64° ± 1.36° and 2.93° ± 1.68°, respectively) and L5-left ilium (2.58° ± 1.43° and 2.93° ± 1.71°, respectively) was significantly lower than for Model 1 and Model 2 at L5-right ilium (5.14° ± 2.48° and 4.95° ± 2.45°, respectively) (p = 0.036) and L5-left ilium (5.19° ± 2.34° and 4.99° ± 2.31°) (p = 0.022). Last, results of the axial compression testing at all measured points were not statistically different among reconstructions. CONCLUSIONS The addition of a transverse bar in Model 2 offered no biomechanical advantage. Although the implementation of 4 iliac screws and 4 rods conferred a definitive kinematic advantage in Model 3, that model was associated with significantly restricted lumbopelvic ROM.

Original languageEnglish (US)
Pages (from-to)570-577
Number of pages8
JournalJournal of neurosurgery. Spine
Volume27
Issue number5
DOIs
StatePublished - Nov 1 2017

Keywords

  • biomechanics
  • BMD = bone mineral density
  • EZ = elastic zone
  • Galveston L-rod
  • LED = light-emitting diode
  • lumbopelvic
  • MGR = modified Galveston reconstruction
  • NZ = neutral zone
  • ROM = range of motion
  • sacral reconstruction
  • sacrectomy
  • sacrum
  • SIJ = sacroiliac joint
  • TFR = triangular frame reconstruction

ASJC Scopus subject areas

  • Surgery
  • Neurology
  • Clinical Neurology

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    Macki, M., De la Garza-Ramos, R., Murgatroyd, A. A., Mullinix, K. P., Sun, X., Cunningham, B. W., McCutcheon, B. A., Bydon, M., & Gokaslan, Z. L. (2017). Comprehensive biomechanical analysis of three reconstruction techniques following total sacrectomy: an in vitro human cadaveric model. Journal of neurosurgery. Spine, 27(5), 570-577. https://doi.org/10.3171/2017.2.SPINE161128