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Updated: Aug 10, 2026
An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model
Published on: May 31, 2017
A biomechanical comparison of sacral pedicle screw salvage techniques
Bonaventure B Ngu1, Stephen M Belkoff, Daniel E Gelb
1Department of Orthopaedic Surgery, University of Maryland School of Medicine, Baltimore, MD, USA.
Study Design:
Biomechanical cadaver study.
Objectives:
The purpose of our study was to compare the pullout strength of standard, expandable, and cement-augmented pedicle screws.
Summary Of Background Data:
Salvage procedures are needed to restore the stability of lumbosacral arthrodesis when pedicle screw fixation in the sacrum fails.
Methods:
Thirteen pairs of sacral (S1) pedicles were implanted initially with 7-mm tapped monoaxial stainless steel pedicle screws (Moss Miami, Depuy Spine, Raynham, MA) inserted under fluoroscopy with bicortical purchase. The screws were distracted axially at a rate of 6 mm/min to measure pullout strength. One pedicle of each pair was assigned randomly to be revised with an expandable pedicle screw (omega-21 Spinal Fixation System, EBI Medical Systems, Parsippany, NJ); the contralateral pedicle was revised with a screw augmented with polymethylmethacrylate (Simplex P, Howmedica, Mahwah, NJ). The screws then were retested as before to measure pullout strength.
Results:
Expandable screws (391 +/- 28 N) and polymethylmethacrylate-augmented screws (599 +/- 28 N) exhibited significantly greater pullout strength than their respective initial standard pedicle screws (145 +/- 28 N and 156 +/- 28 N).
Conclusions:
Our results suggest that expandable pedicle screws may provide sufficient fixation, but these results need clinical verification.
