Background Context: Spinal fusion with pedicle screw fixation is widely used for stabilization, yet its long-term success is often limited by mechanical complications such as screw loosening and pull-out. Purpose: Pedicle screw loosening and pull-out are major complications of instrumented spinal fusions, biomechanically caused mainly by excessive flexion moments. A “safety sling” (a textile band looped around the spinous processes) could prevent excessive loading on pedicle screws during flexion. The goal of this study is to examine the biomechanical effectiveness of the safety sling concept on construct strength during simulated lumbar flexion in human spinal segments. Study Design: Biomechanical cadaveric study. Materials and Methods: Twenty-four human lumbar segments were biomechanically tested under simulated flexion loads using an established biomechanical setup. Four groups (n=6 each) were compared: (1) pedicle screw instrumentation alone, (2) instrumentation with a dorsally attached safety sling (consisting of a 10 mm textile band around the segmental spinal processes), (3) instrumentation with midline decompression, and (4) instrumentation with midline decompression plus safety sling. All specimens underwent increasing flexion loads until failure to assess the safety sling’s effect on construct resilience. Results: The safety sling demonstrated a significant improvement in flexion moment resilience: Median failure load increased by factor 2.06 with an intact midline (60.6 Nm (47.2; 85.2) with safety sling versus 29.4 Nm (21.4; 32.9) without, P =0.026) and by factor 2.60 in decompressed segments (75.7 Nm (53.4; 76.5) with safety sling versus 29.1 Nm (25.6; 43.1) without, P =0.026). Conclusion: The concept of a “safety sling” (looping a band around the segment’s spinal processes) is a highly effective supplementary measure for enhancing primary construct strength during spinal flexion in pedicle screw constructions. By reducing the load on the screw-bone interface, this approach represents a promising strategy to reduce flexion-induced loading at the screw-bone interface. Clinical Significance: Incorporating a safety sling into pedicle screw constructs may reduce flexion-induced mechanical loading of pedicle screw constructs in the early postoperative period. Level of Evidence: According to the Oxford Centre for Evidence-Based Medicine 2011 Levels of Evidence, this biomechanical cadaveric study provides Level 5 evidence.
Schuler et al. (Thu,) studied this question.