Bi-cortical Screw Fixation Depth Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Achieving safe and accurate bi-cortical screw fixation in vertebral bodies is challenging due to the difficulty in determining the correct position of screws, particularly in the human vertebrae, where the curvature of the anterior cortical wall can lead to risks of breaching vital tissues, and current methods rely heavily on surgeon feel rather than precise instrumentation.
Innovation Solution
A system of instruments and methods involving a K-wire, dilators, a contour probe, a cannulated bone reamer, a blunt-tip probe, and a bone tap with adjustable safety stop, which allows for precise measurement and controlled insertion of screws, ensuring bi-cortical fixation without excessive penetration of the anterior cortical wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the screw is advanced to achieve bi-cortical fixation, then the screw pull-out strength is improved, but the risk of breaching the anterior cortical wall and damaging vital tissues increases
Solution Approach 1:
The pilot hole is pre-drilled through the entire vertebral body to establish the exact trajectory and depth required for bi-cortical fixation. This preliminary action allows the surgeon to determine the precise location where the screw will exit the anterior cortical wall before actually inserting the screw, thereby achieving the desired pull-out strength while avoiding damage to vital tissues.
Solution Approach 2:
A depth gauge or measuring instrument is used as an intermediary tool between the pilot hole and the screw insertion. This intermediary device measures the depth of the pilot hole and provides visual or tactile feedback to indicate when the screw should be inserted to achieve bi-cortical fixation without over-penetration. The measuring instrument acts as a mediator that translates the complex anatomical geometry into simple, actionable depth information.
2Loss of information
If intraoperative fluoroscopy is used to gauge screw position, then the visibility of screw position is improved, but the accuracy of depth determination is reduced due to curvature of the anterior cortical wall
Solution Approach 1:
The patent replaces reliance on fluoroscopic imaging (electromagnetic system) with a direct mechanical measurement system. A depth gauge or measuring instrument with physical contact with the bone surface and the screw provides direct mechanical measurement of screw depth. This mechanical substitution eliminates the interpretation errors that occur when trying to assess screw position on fluoroscopic images, particularly in the presence of curved anterior cortical walls.
3Ease of operation
If surgeon feel is relied upon for forming and tapping the pilot hole, then the simplicity of the procedure is maintained, but the precision and repeatability of bi-cortical fixation are reduced
Solution Approach 1:
The depth gauge or measuring instrument is designed to be self-regulating, providing automatic feedback to the surgeon. The instrument may include visual indicators, tactile stops, or audible signals that automatically indicate when the pilot hole has reached the correct depth for bi-cortical fixation. This self-service mechanism eliminates the need for the surgeon to rely on subjective feel while maintaining procedural simplicity, as the instrument itself provides the guidance.
Data Source
AI summary
Surgical systems and methods are disclosed for safe bi-cortical bone screw placement within a bone segment. Included is a method of measurement to control advancement of instruments and implants to repeatedly obtain bi-cortical screw fixation while minimizing protrusion of the lead end of the screw beyond the distal cortical wall therein reducing incidence of injury to adjacent soft tissues.