Pedicle Screw Assembly Segmented Housing for Low Torque Locking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current pedicle screw systems require complex assembly steps, high tightening torque, and often result in disruption or fracture at the screw-bone interface due to splaying of the receiving element during securement, which increases manufacturing costs and intraoperative difficulties.
Innovation Solution
A pedicle screw assembly featuring a novel receiving housing/locking member/collet and compression member arrangement that reduces splaying forces, allowing for secure fixation without compromising the bone-bone screw interface, even under high torque loads, and enabling a lower outside profile for the receiving housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a threaded set-screw or cap is used to lock the rod into the receiving element, then the rod can be secured to the bone screw, but the receiving element may splay or separate when the set-screw is threaded in to apply adequate load
Solution Approach 1:
The receiving element is divided into multiple segments or lobes that can independently deform. When the set-screw is tightened, these segments are forced together radially inward, clamping the rod securely without causing the entire receiving element to splay outward. This segmentation allows the locking mechanism to generate clamping force without compromising the screw-bone interface.
Solution Approach 2:
Instead of the set-screw pushing the receiving element outward to lock the rod (which causes splaying), the set-screw pushes the segmented receiving element inward to clamp the rod. This inverted mechanism achieves securement by compressing the receiving element radially inward rather than expanding it outward, thereby preventing interface disruption.
2Reliability
If a high tightening torque is applied to achieve adequate lock on the bone screw implants, then the rod can be securely locked, but larger implant profiles are necessary to withstand the resultant loads
Solution Approach 1:
The segmented receiving element distributes the locking torque across multiple contact points between the segments and the rod. This segmentation allows the same locking torque to be achieved with a smaller overall implant profile, as the force is distributed rather than concentrated, reducing the required size of the receiving element and bone screw.
Solution Approach 2:
The invention changes the mechanical parameter of force distribution by using segmented geometry. Instead of a single large-contact-area interface requiring high torque, multiple smaller contact areas work together to achieve the same locking effect with lower torque requirements and smaller implant profiles.
3Adaptability or versatility
If current pedicle screw system designs are used to address vertebral size and anatomic differences, then various vertebral configurations can be accommodated, but complex assembly steps are required which increase manufacturing cost and intraoperative difficulty
Solution Approach 1:
The segmented receiving element design serves multiple functions: it accommodates various vertebral sizes and anatomies through its deformable structure, provides secure rod locking through radial compression, and simplifies assembly by eliminating the need for complex multi-step procedures. This universal design can be adapted to different vertebral configurations while maintaining a consistent, simple assembly process.
Solution Approach 2:
The segmented receiving element is self-adjusting and self-locking. When the set-screw is tightened, the segments automatically deform and clamp the rod without requiring additional assembly steps or adjustments. This self-service mechanism reduces intraoperative complexity while maintaining adaptability to different vertebral anatomies.
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 solution reduces manufacturing costs, decreases in vivo locking torque requirements, minimizes torsional stresses on the bone-bone screw site, and decreases component size profiles, thereby reducing soft tissue complications and enhancing surgical efficiency.
Implementation Method 1
a compression member having a cylindrical outer surface and a conical inner surface... a locking member having an outer surface adapted to mate with the conical inner surface of the compression member
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A pedicle screw assembly (100, 200) and method of assembly (500) are disclosed. The pedicle screw assembly (100, 200) includes a bone fastener (170, 270) having a head (171, 271) at a proximal end (173, 273) and a threaded portion (172, 272) extending between the proximal end (173, 273) and a distal end (174, 274). The assembly (100, 200) also includes a compression member (130, 230) having a conical inner surface (136, 236) and a locking member (140) having an outer surface (142, 242) adapted to mate with the conical inner surface (136, 236) of the compression member (130, 230). The assembly (100, 200) may also have an elongated member (120) and a set screw (110, 210) that has a threaded portion (113, 213). The assembly (100, 200) may also have a receiving housing (150, 250) having a central bore (151, 251) extending from a threaded proximal end (152, 252) to a distal end (153, 252) and a U-shaped cavity (160, 260) positioned perpendicular to the central bore (151, 251) and configured to receive the elongated member (120).