Yves Ntilikina, Yann Philippe Charles, Sylvain Persohn, Wafa Skalli


December 2020, Volume 29, Issue 12, pp 2980 - 2989 Original Article Read Full Article 10.1007/s00586-020-06594-2

First Online: 16 September 2020

Purpose

This in vitro biomechanical study compares residual lumbar range of motion (ROM) and rod strain after lumbopelvic instrumentation using 2 rods, 4 rods and interbody cages.

Methods

Seven human cadaveric specimens were instrumented from L1 to sacrum, and pelvic screws were implanted. The pelvis was constrained and moments up to 7.5 Nm were applied to T12. Segmental L1–S1 ROM was analyzed by tracking radiopaque balls implanted in each vertebra using biplanar radiographs. Deformation within principal rods was measured by strain gauges. Four configurations were compared: 2 rods (2R), 4 rods (4R), 4 rods + ALIF at L4–L5 and L5–S1 (4R + ALIF), 2 rods + ALIF (2R + ALIF).

Results

Intact average global L1–S1 ROM was 42.9° (27.9°–66.0°) in flexion–extension (FE), 35.2° (26.8°–51.8°) in lateral bending (LB), 18.6° (6.7°–47.8°) in axial rotation (AR). In FE, average ROM was 1.9° with both 4-rod configurations versus 2.5° with 2R and 2.8° with 2R + ALIF (p 

Conclusions

Double rods and interbody cages decrease residual ROM in FE and AT. Double rods seem efficient in limiting strain in principal rods. The use of single rods with cages at the lumbosacral junction increases strain at the first adjacent level without cage.


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