Surgical Screw Recess Geometry for Secure Driver Engagement
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Solution Overview
Problem
Existing screw elements for spinal, orthopaedic, or trauma surgery face challenges in handling precision and secure tightening, particularly in minimally invasive procedures where space is limited.
Innovation Solution
A screw element with a recessed drive portion featuring protrusions and drive grooves designed for enhanced engagement with a screwdriver, manufactured using additive manufacturing techniques, allowing for improved clamping and efficient force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the screw element is made small for minimally invasive surgery, then the invasiveness is reduced, but the handling precision and risk of loss increase
Solution Approach 1:
The drive portion incorporates protrusions that extend radially from the main contour, adding a dimensional feature that increases the effective engagement surface area without increasing the overall screw size. This allows better screwdriver engagement and reduced radial play while maintaining the small form factor needed for minimally invasive surgery
Solution Approach 2:
The drive portion is segmented into multiple protrusions spaced circumferentially around the screw axis, creating discrete engagement points that collectively provide enhanced clamping and force distribution, improving handling precision of the small screw element
2Ease of manufacture
If the drive portion has a simple contour, then the manufacturing is easier, but the clamping of the screwdriver is insufficient
Solution Approach 1:
The protrusions are positioned at specific locations on the drive portion wall where they provide localized enhancement of screwdriver engagement. This allows the majority of the drive portion to maintain a simple, easily manufactured contour while specific local regions provide the necessary clamping features
3Ease of operation
If there is radial play between the screwdriver and drive portion, then the insertion is easier, but the force application efficiency is reduced
Solution Approach 1:
The protrusions are designed with dimensions that allow initial radial play for easy insertion, but which engage to reduce play during force application. The protrusion height and radial extent are optimized to provide progressive engagement that transitions from easy insertion to efficient force transfer
Data Source
AI summary
A screw element for use in spinal, orthopaedic, or trauma surgery, has a screw axis, a screw thread, and a drive portion including a wall that defines an axially extending recess for engaging a tool. The recess has a cross-sectional profile that extends from a first end to a second end in a direction of the screw axis. The cross-sectional profile has a first portion positioned closest radially to the screw axis and a plurality of drive grooves that extend radially away from the first portion and that are spaced apart from each other in a circumferential direction around the screw axis. A portion of the wall includes a protrusion that protrudes laterally away from the wall into the recess. The protrusion is spaced apart axially from the first and second ends of the recess.