Press-Fit Pedicle Screw Coupling for Low-Profile Spinal Fixation
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Solution Overview
Problem
Conventional surgical and pedicle screw coupling systems are bulky, causing tissue damage and irritation, difficult to install, require simultaneous locking of components, and lack flexibility in rod stiffness, complicating minimally invasive procedures and fusion extensions.
Innovation Solution
A pedicle screw coupling assembly that allows for a rigid fixed attachment between a pedicle screw and a member extending between adjacent screws via a press fit, enabling full insertion of the screw against the bone while maintaining the ability to apply force for attachment, with features like partially spherical surfaces and varying diameters to accommodate various insertion angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coupling assemblies are used, then bone stabilization is achieved, but the system becomes bulky and causes increased tissue damage and irritation
Solution Approach 1:
The coupling assembly is divided into separate components: a pedicle screw with head, a rod, and a coupling device that connects them. This segmentation allows each component to be optimized independently, resulting in a smaller overall profile that reduces tissue damage while maintaining stabilization function.
Solution Approach 2:
The coupling device features a rod-receiving cavity that nests the rod within its structure. The rod is inserted into the coupling device after screw insertion, creating a compact nested configuration that minimizes the external profile and reduces tissue irritation while preserving the bone stabilization function.
2Ease of operation
If conventional coupling systems with pre-attached rods are used, then assembly is simplified, but surgical maneuverability is reduced and inventory costs increase
Solution Approach 1:
The pedicle screw is inserted into the bone first, establishing the foundational position. The rod is then subsequently inserted into the coupling device's rod-receiving cavity. This sequential preliminary action allows surgeons to perform interbody work and other maneuvers before final rod attachment, enhancing surgical flexibility while maintaining assembly simplicity.
3Stability of the object's composition
If traditional coupling systems are used, then fixed attachment is achieved, but the ability to compress the coupling system along the rod is prevented
Solution Approach 1:
The coupling device incorporates a dynamic compression mechanism where the rod can be compressed along its longitudinal axis. This compression is transmitted through the coupling device to the pedicle screw, allowing dynamic adjustment and compression capability while maintaining stable fixed attachment. The system transitions from a static rigid connection to a dynamically adjustable connection that preserves both stability and compressibility.
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 low-profile implantation with reduced tissue damage, facilitates easier installation, allows for flexible rod stiffness, and supports fusion extensions without requiring complete removal or cutting of existing rods, enhancing surgical maneuverability and reducing stress on bones.
Implementation Method 1
Insertion of the protrusion into the bore may be made possible by an application of force that forces a point of maximum diameter of the protrusion fully within the bore. When the protrusion is received within the proximally oriented bore, a press fit is created between the protrusion and the head portion.
Data Source
AI summary
Variations on improved pedicle screw coupling assemblies, along with methods for use of such assemblies provide improved functional characteristics over existing devices. A coupling assembly is capable of providing rigid fixed attachment between a pedicle screw fully seated to underlying bone and a member extending between adjacent pedicle screws. The coupling assembly includes a pedicle screw having a threaded shaft and a head portion. The head portion includes a driving feature and a proximally oriented bore having a bore diameter. In one version, the coupling assembly includes a member adapted to extend between adjacent pedicle screws. The member includes a protrusion adapted for insertion into the bore of the pedicle screw, the protrusion having a protrusion diameter that is larger than the bore of the pedicle screw head portion. In another version, the coupling assembly includes a spherical bore in the screw head.