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New approaches to proven technology: Force control posterior thoracolumbar fusion with an innovative pedicle screw system

Abdalla Y, Hajdari S

Highlights

  • Both the screw-related and patient-related screw loosening rates (2.3% and 8.9%) are statistically significantly lower than the pooled rates of the current literature search (3.8% and 15.1%).
  • Since implant-related failures include screw loosening as well as screw fractures, rod fractures, and disassembly of the construct – the latter were each 0 % in the present study – it can be assumed that the number of implant failures must also be considerably lower.
  • A low rate of deep surgical site infections, 1,3% (2/150) .

Abstract

Objective

Despite continuous advancements, posterior thoracolumbar fusion with pedicle screw systems (PSS)  has failed to reduce the rate of reoperation over recent decades. Implant failure, including screw pullout or loosening, implant breakage, and disassembly, is the leading cause for hardware-related reoperations. Since mechanical failure is due to overloading, efforts must be made to eliminate avoidable stresses. The study aim is to compare the results of a novel force-controlled PSS with literature.

Methods

This retrospective, consecutive cohort includes 150 patients who received the Neo Pedicle Screw System™ for single- or multilevel thoracolumbar fusion. Fusion rate, VAS back pain, reoperations, screw loosening, and surgical site infections (SSI) were evaluated. A structured literature search was performed specifically on screw loosening. Statistical significance was assumed at p < 0.05.

Results

Indications were mainly trauma (62,7%) and degeneration (34,0%), and mean age was 66 years. Overall fusion or fracture healing rate was 93,8% (CI 89,3%-98,3%), mean VAS back pain improvement 6,2 (p < 0,001), overall reoperation rate 16,7%, (CI 10,7%–22,7%), including 8,7% (CI 4,2%-13,2%) re-interventions involving the implant system, patient-based screw loosening rate 8,9% (CI 3,9%-13,9%) and screw-based loosening rate 2,3% (CI 1,3%-3,3%), SSI rate 2,7% (CI 0,1%-5,3%). No implant breakages occurred. The literature search revealed screw loosening rates of 15,1% (CI 14,2%-16,0%) patient-based and 3.8 % (CI 3,5%-4,1%) screw-based, which were statistically significantly higher than in the study.

Conclusion

By controlling the forces applied intraoperatively, the surgeon can avoid unintended spinal stresses and better consider the patient’s individual anatomical and biomechanical balance. The results suggest that the principle of force-control can be effective.

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