Biomechanical Comparison between Isobar and Dynamic-Transitional Optima (DTO) Hybrid Lumbar Fixators: A Lumbosacral Finite Element and Intersegmental Motion Analysis

Figure 8

Schematic diagrams illustrated the performances of dynamic hybrid fixators. (a) Dynesys cord pretension made spacer-screw contact but induced high stress at pedicle screw-bone junction. (b) Isobar integral damper provided axial rotation and distraction coupling to afford stress-shielding and reduce loading on the facet joint and pedicle screw. (c) A 70-year-old male patient received Isobar hybrid fixation at L3-4-5 and got back pain at 8 months postoperatively due to screw loosening at L3 (arrow). (d) Subsequently, radicular pain was noticed at four years due to adjacent segment disease at L2-3 (arrow).

(a)

(b)

(c)

(d)