A Toggling Resistant In-Pedicle Expandable Anchor: A Preliminary Study

Area of Science:

• Spinal Surgery
• Biomedical Engineering
• Orthopedic Research

Background:

• Pedicle screw loosening is a significant complication in spinal fusion surgery.
• Osteoporotic bone exacerbates pedicle screw toggling and fixation failure.
• This compromises surgical outcomes and necessitates revision procedures.

Purpose of the Study:

• To explore an in-pedicle expandable anchor concept for enhanced spinal bone anchor fixation.
• To investigate the potential of increased anchor-bone contact area to improve toggling resistance.
• To address the challenge of pedicle screw loosening, particularly in osteoporotic bone.

Main Methods:

• A scaled-up, two-dimensional prototype of an in-pedicle expandable anchor was designed.
• The prototype utilized a bolt-tensioned system with ten stainless steel wedges for expansion.
• Preliminary experiments were conducted using a 5 PCF cancellous bone phantom (Sawbones).

Main Results:

• The expandable anchor prototype successfully compressed the cancellous bone phantom during expansion.
• The design aims to increase the contact area between the anchor and cortical bone.
• This preliminary data suggests feasibility for improved toggling resistance.

Conclusions:

• An expandable in-pedicle anchor shows promise for increasing toggling resistance in spinal bone anchors.
• This technology could be particularly beneficial for patients with osteoporotic bone.
• Further research is warranted to validate the clinical efficacy of this novel anchor design.