Pullout Strength of Pedicle Screws Following Redirection After Lateral or Medial Wall Breach. Issue 17 (1st September 2018)

• Record Type: Journal Article
• Authors: Maeda, Toru; Higashino, Kosaku; Manabe, Hiroaki; Yamashita, Kazuta; Hayashi, Fumio; Goda, Yuichiro; Tsuruo, Yoshihiro; Sairyo, Koichi
• Is Part Of: Spine. Volume 43:Issue 17(2018)
• Publication Date: 2018-09-01
• Subjects: larger screw -- malpositioned screw -- pedicle screw -- pullout strength -- redirection -- thoracolumbar spine; Spine -- Abnormalities -- Periodicals; Spine -- Diseases -- Periodicals; Spine -- Surgery -- Periodicals; 616.73005
• DOI: 10.1097/BRS.0000000000002611
• Languages: English
• ISSNs: 0362-2436

Abstract

Abstract : Study Design: A cadaveric biomechanical study designed to test the pullout strength of pedicle screws. Objective: To evaluate the pullout strength of redirected pedicle screws with a larger diameter following lateral wall breach, redirected pedicle screws of the same diameter following medial wall breach, and redirected pedicle screws with a larger diameter following medial wall breach. Summary of Background Data: Screw malposition is one of the main pitfalls of inserting pedicle screws. Intraoperatively a malpositioned screw is redirected and inserted along the correct axis. Methods: Forty-seven vertebrae (T9-L5) were harvested from eight fresh cadaveric spines. The 18 pedicle screws that breached the lateral wall were then removed and redirected using a pedicle screw of 1 mm larger in diameter. The 16 pedicle screws that had breached the medial wall were then removed and redirected using a pedicle screw of the same diameter. The other 13 pedicle screws that had breached the medial wall were then removed and redirected using a pedicle screw of 1 mm larger in diameter. The pullout strength was measured. Results: Following lateral wall breach, mean pullout strength for the larger redirected screws was 46.9% greater than that of the correctly aligned screws. Following medial wall breach, mean pullout strength for the redirected screws of the same diameter was 20.6% less than that of the correctly aligned screws. Mean pullout strength for the larger pedicle screws following medial wall breach was 27.3% more than that of the correctly aligned screws. Conclusion: Redirected pedicle screws of larger diameter after a lateral or medial pedicle breach show recovery of pullout strength. However, the pullout strength of redirected pedicle screws of the same diameter after a medial pedicle breach is significantly less than that of correctly aligned screws. Level of Evidence: 1