Expandable Locking Screwdriver for Secure Bone Anchor Retention
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Solution Overview
Problem
Small bone screws often become disengaged from driving instruments during insertion or removal in patients, leading to potential loss and complications due to the size and design of retention sleeves on driving instruments, which can obscure the surgeon's view and interfere with the procedure.
Innovation Solution
A locking screwdriver with an expandable distal end and a sliding member that can be longitudinally translated to create a secure lock with the bone screw, using a combination of tapered surfaces and expansion segments to ensure a stable interface without increasing the diameter of the driving instrument shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If retention sleeves or other structures are mounted on the shafts of driving instruments to secure small bone screws, then the reliability of bone screw retention is improved, but the shaft diameter becomes too large for desired applications and the surgeon's view is obscured
Solution Approach 1:
The expansion member is nested within the shaft, allowing it to be stored in a compact state during insertion. When activated, it expands outward to engage the bone screw, providing secure retention without permanently increasing the shaft diameter. This nested configuration resolves the contradiction between reliable retention and compact shaft size.
Solution Approach 2:
The driving instrument transitions from a static shaft structure to a dynamic system where the expansion member can change its radial dimension. The shaft remains compact during insertion but dynamically expands to engage and retain the bone screw, then contracts for removal. This dynamic behavior allows the instrument to adapt its size for different operational phases.
2Reliability
If retention structures are added to the driving instrument shaft, then the security of bone anchor engagement is improved, but the surgeon's view of the bone screw and target location is obscured
Solution Approach 1:
The expansion member is concealed within the shaft during the approach phase, maintaining an unobstructed surgical field and clear view for the surgeon. Only when engagement is required does the expansion member deploy outward, providing security without compromising visibility during critical visualization phases.
Solution Approach 2:
The retention structure dynamically appears and disappears based on operational needs. During insertion and visualization, the shaft maintains its compact profile for optimal viewing. When engagement is needed, the expansion member deploys to provide secure retention, then retracts to restore clear visibility for the surgical field.
3Reliability
If the distal end of the shaft is expanded to lock with the bone anchor, then the reliability of the lock is improved, but the ability to insert and remove the bone screw is compromised
Solution Approach 1:
The locking mechanism is designed to be dynamically controllable through actuator operation. The expansion member can be deployed to create a secure lock during the driving phase, then retracted to enable easy removal after the bone screw is set. This dynamic control allows the system to transition between locked and unlocked states as needed.
Solution Approach 2:
The expansion member is positioned and prepared within the shaft before engagement occurs. The actuator is pre-configured to deploy the expansion member at the appropriate moment, ensuring reliable locking exactly when needed. After the bone screw is driven into position, the actuator can then retract the expansion member to facilitate removal, making the entire process more controllable and easier to operate.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The locking screwdriver effectively prevents the loss of bone screws by providing a secure, releasable lock that maintains a clear surgical field and ensures precise control during bone anchor insertion and removal, enhancing procedural safety and efficiency.
Implementation Method 1
ramps configured to cause at least a portion of the sliding member to be displaced radially outward when the sliding member translates along the shaft
Data Source
AI summary
An interlock driving instrument is configured to be releasably lockable to a fastener, such as a bone anchor. A bone anchor can be locked to the interlock driving instrument by inserting an expandable distal end of the shaft of the interlock driving instrument into the driving opening of the bone anchor and expanding the distal end within the driving opening by translating an expansion member into the expandable distal end. Alternatively, the bone anchor can be locked to the interlock driving instrument by inserting the distal end of the shaft of the interlock driving instrument into the driving opening of the bone anchor and translating a sliding member along a sloped surface defined in a channel extending into the shaft.