Torqueless Spinal Rod Fixation via Linear Compression
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Solution Overview
Problem
Existing spinal stabilization systems require additional torque to secure rods to bone screws, which can strip the purchase between the bone and the screw threads, necessitating the use of anti-torque tools and complex coordination by surgeons.
Innovation Solution
A linear locking set screw system that uses compressive forces instead of torque to secure a rod to an embedded bone screw, featuring a clamp body with a spherical head receptacle and a compression ring that applies linear movement to immobilize the rod and bone screw connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If threaded nuts are used to secure rods to connectors with torque, then the connector/rod construct is firmly secured, but the bone screw threads may be stripped and the purchase between bone and screw is compromised
Solution Approach 1:
The invention extracts the torque application function from the bone screw-rod connection system. By using a separate torqueless connector that receives the rod and applies locking force independently of the bone screw, the harmful torque is removed from the bone-screw interface while maintaining secure rod attachment
Solution Approach 2:
The torqueless connector acts as an intermediary between the bone screw and the rod. It receives the rod and applies locking forces through set screws or compression mechanisms, mediating the connection without transferring torque to the bone screw threads
2Manufacturing precision
If torque wrench and anti-torque device are used to secure the connector/rod construct, then the required torques are achieved, but the procedure becomes complex and dependent on surgeon skill
Solution Approach 1:
The torqueless connector system is self-contained and self-explanatory. The set screws or compression mechanisms naturally apply appropriate locking forces without requiring external torque measurement devices or anti-torque tools, making the system self-sufficient and easier to use
Solution Approach 2:
The invention removes the torque wrench and anti-torque device from the surgical procedure. By eliminating the need for these specialized tools, the system becomes simpler and less dependent on surgeon experience with complex tool coordination
3Strength
If additional torque is applied to tighten and lock the rod to bone screws, then the connection is secured, but the thread purchase between bone and screw may be stripped
Solution Approach 1:
The invention converts the potentially harmful effect of torque into a beneficial design feature by creating a separate torque application path. The locking mechanism applies force in a direction that secures the connection without creating harmful lateral or rotational stresses on the bone screw threads
Solution Approach 2:
The harmful torque component is extracted from the bone screw-rod connection by using a torqueless connector design that applies locking forces through set screws or compression mechanisms that do not rotate or apply lateral stress to the bone screw threads
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
Enables precise and reproducible linear engagement and disengagement of the rod to the bone screw, eliminating the need for rotational torque and reducing the risk of thread stripping, thus simplifying the stabilization process and enhancing surgical efficiency.
Implementation Method 1
A compression ring is placed around the clamp body. The clamps are tightened to hold the rod to the bone screws in a pre-selected position by linear movement of the compression ring.
Data Source
AI summary
A low profile orthopedic device is used to fix and stabilize bones to correct anomalies in skeletal structure occurring naturally or by trauma. Bone screws are screwed into bones by application of torque. Connectors are attached to the anchored bone screws. Each connector includes a clamp and a compression ring. A connecting rod connects several connectors together. The clamps are tightened to hold the rod to the bone screws in a pre-selected position by linear movement of the compression ring.