Dual-Driver Fastener Locking for Surgical Retractor Stability
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Solution Overview
Problem
Existing surgical instruments lack effective mechanisms to prevent accidental disassembly of polyaxial joint components during procedures, which can compromise the stability and functionality of retractor assemblies, particularly in spinal fusion surgeries.
Innovation Solution
A backout prevention mechanism is introduced, allowing a fastener to be adjusted using two different drivers: a first driver for complete removal and a second driver for adjustment, with a locking body that interferes with a flange to prevent accidental disassembly during procedures, while enabling separate sterilization of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single driver is used for both complete removal and adjustment of the fastener, then the device is simpler to operate, but accidental disassembly cannot be prevented during adjustment
Solution Approach 1:
The driver system is segmented into two distinct drivers: a first driver with a first drive portion for complete removal of the fastener, and a second driver with a second drive portion for adjustment only. This segmentation allows the system to differentiate between removal and adjustment operations, preventing accidental disassembly during adjustment while maintaining operational simplicity through dedicated tools.
Solution Approach 2:
The locking body acts as an intermediary mechanism that responds differently to the two drivers. When the second driver is used, the locking body engages to prevent complete removal. When the first driver is used, the locking body disengages to allow complete removal. This intermediary mechanism mediates between the two operational modes to ensure safety during adjustment.
2Reliability
If the fastener is securely locked to prevent accidental disassembly, then reliability is improved, but separate sterilization of components becomes difficult
Solution Approach 1:
The locking mechanism is dynamic rather than static. The locking body can transition between locked and unlocked states based on which driver is used. During the surgical procedure, the mechanism remains locked for security. After the procedure, using the first driver unlocks the mechanism, allowing complete disassembly for separate sterilization of the fastener and housing components.
Solution Approach 2:
The system is designed to maintain the locked state as the preliminary condition during the surgical procedure, ensuring secure assembly. After the procedure completes, the locking mechanism can be deliberately unlocked using the first driver, allowing components to be separated for sterilization. This preliminary locking followed by deliberate unlocking resolves the contradiction between security and sterilization accessibility.
3Ease of operation
If the fastener allows free adjustment during procedure, then ease of operation is improved, but accidental disassembly becomes a risk
Solution Approach 1:
The two drivers are asymmetric in their interaction with the fastener head. The second driver has a drive portion that engages the upper socket but is blocked by the locking body from achieving complete removal. The first driver has a drive portion that can overcome or disengage the locking body to achieve complete removal. This asymmetry in driver design allows free adjustment with the second driver while preventing accidental disassembly, as the locking mechanism only engages with specific driver geometries.
Data Source
AI summary
A driver-specific back-out prevention mechanism is disclosed that includes a screw and a body. A first driver can be used for coupling and decoupling the screw with the body, and a second driver can only be used for adjusting the position of the screw in the receiving body. The body includes a cavity for receiving a head of the screw, with the cavity having an inward flange. The screw includes upper and lower sockets, with a channel extending though the head from the lower socket and a lock body disposed in the channel. Engagement with the first driver allows the locking body to move such that the fastener can be inserted and removed from the body. Engagement with the second driver displaces the locking body such that the locking body interferes with the flange such that screw fastener cannot be removed from the body by the second driver.