Insertional torque and pullout strength of pedicle screws versus titanium suture Anchors: Towards development of a novel proximal junctional kyphosis prevention technique

Abstract

Proximal junctional kyphosis (PJK) is a common and devastating complication after spinal deformity surgery with a high need for revision surgery. PJK often leads to poor patient outcomes and large societal costs, which has led to the development of multiple prophylactic methods which have yet to eliminate PJK. A novel method for PJK prevention includes placing suture anchors, rather than pedicle screws, above the spinal construct to function as a tether. This biomechanical investigation examined the insertional torque and pullout strength of pedicle screws compared to suture anchors on 6 cadaveric vertebrae (12 pedicles). The mean insertional torque was 0.802 ± 0.477 N*m for pedicle screws and 0.368 ± 0.310 N*m for suture anchors (p = 0.047). The mean pullout strength was 973.16 ± 202.03 N for pedicle screws and 206.94 ± 181.78 N for suture anchors (p < 0.01). This study demonstrated that suture anchors had both less insertional torque and pullout strength compared to pedicle screws and may provide a more physiologic stress taper at the upper instrumented vertebrae of long-segment spinal constructs to help prevent proximal junctional kyphosis or catastrophic proximal junctional failure. Further research is needed to examine the biomechanics of this in long-segment constructs as well as in vivo performance of suture anchors as proximal junctional kyphosis prophylaxis.

Keywords

• Adult spinal deformity
• Proximal junctional kyphosis
• Suture anchor
• Tethering