A wise man once said, the only constant is change. So, is it time to review the role of cross-link instrumentation for posterior decompression of highly unstable vertebral segments? A new study revisits this important question and has some surprising conclusions.
In “Posterior spinal instrumentation and decompression with or without cross-link?,” the researchers evaluated the impact of cross-link augmentation on single-level lumbar instrumentation stiffness after gradual decompression procedures.
The findings are published in the December 2021 issue of the North American Spine Society Journal.
“Posterior lumbar instrumentation requires sufficient primary stiffness to ensure bony fusion and to avoid pseudarthrosis, screw loosening, or implant failure. To enhance primary construct stiffness, transverse cross-link connectors attached to the vertical rods can be used. Their effect on the stability of a spinal instrumentation with simultaneous decompression is yet not clear,” the researchers wrote.
Seventeen vertebral segments (6 L1/2, 6 L3/4, 5 L5/S1) of 12 fresh-frozen human cadavers were instrumented with a transpedicular screw-rod construct following the traditional pedicle screw trajectory.
Range of motion of the segments was sequentially recorded before and after four procedures:
Each test was performed with and without cross-link augmentation.
The researchers then measured the motion between the cranial and caudal vertebrae in all six major loading directions: flexion/extension, lateral bending, lateral shear, anterior shear, axial rotation, and axial compression/distraction.
Range of motion was significantly reduced with cross-link augmentation in axial rotation by Δ0.03–0.18° (7–12%) with a significantly higher range of motion reduction after more extensive decompression.
Slight reductions in flexion/extension and lateral bending were also observed. These reached statistical significance for flexion/extension after facetectomy and transforaminal lumbar interbody fusion insertion only (Δ0.15; 3%).
“Cross-link augmentation may be warranted for highly unstable vertebral segments rather than for standard single-level posterior spinal fusion and decompression,” the study authors wrote.
Study authors include Marco D. Burkhard, Frederic Cornaz, Jose Miguel Spirig, Florian Wanivenhaus, Rafael Loucas, Marie-Rosa Fasser, Jonas Widmer, and Mazda Farshad, al of the Balgrist University Hospital, University of Zurich, Switzerland.
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