Low-Profile Spinal Fixation Anchor with Offset Head
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Solution Overview
Problem
Existing pedicle screw systems for spinal fixation are bulky, difficult to assemble, and pose challenges during installation, especially in smaller vertebral regions like the cervical spine, due to their size and complexity, leading to increased tissue damage and potential misalignment during surgical procedures.
Innovation Solution
A low-profile coupling device with a pivotable anchor member and a tulip-shaped assembly that allows independent locking of the anchor and elongate members, featuring a spherical head and offset shank configuration, enabling greater angular adjustment and secure fixation with a reduced profile, facilitating easier installation and reduced tissue trauma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional pedicle screw systems are used for spinal fixation, then secure fixation can be achieved, but the assemblies become bulky and difficult to install, especially in smaller vertebral regions
Solution Approach 1:
The pedicle screw system is divided into separate modular components: an anchor member with spherical head, a coupling device with rod-receiving portion, and a rod. This segmentation allows each component to be optimized independently and assembled in a compact configuration that reduces overall size while maintaining fixation security.
Solution Approach 2:
The anchor member is received within the coupling device, creating a nested configuration. The spherical head of the anchor member fits into a receiving cavity of the coupling device, with the shank portion extending through a passage, effectively nesting one component within another to reduce bulk.
2Reliability
If traditional pedicle screw systems are used, then fixation can be achieved, but tissue damage increases during installation due to bulkier assemblies
Solution Approach 1:
By nesting the anchor member within the coupling device and using a compact configuration where the spherical head receives the anchor and the shank extends through a passage, the overall assembly size is reduced. This minimized profile allows installation through smaller incisions and reduces tissue trauma during surgical procedures.
Solution Approach 2:
The offset configuration of the anchor member, where the head portion is offset from the shank portion axis, allows for greater angular adjustment and compact positioning. This dimensional arrangement enables the assembly to achieve fixation security in a smaller spatial envelope, reducing the footprint during installation.
3Adaptability or versatility
If polyaxial pedicle screw systems are used to accommodate extreme angles in cervical spine, then adaptability improves, but assembly complexity and difficulty increase
Solution Approach 1:
The coupling device includes a pivotable connection between the anchor member and rod-receiving portion, allowing dynamic adjustment of angles. The anchor member can be pivoted relative to the coupling device, and the rod-receiving portion can be adjusted independently, providing polyaxial flexibility for accommodating extreme angles in the cervical spine without increasing assembly complexity.
Solution Approach 2:
The system is segmented into independently adjustable components: the anchor member with spherical head for bone anchoring, the coupling device with rod-receiving portion for rod attachment, and the pivotable connections between them. This segmentation allows each component to be optimized for its specific function while providing overall angular adaptability through independent adjustment of segments.
4Reliability
If larger anchor members are used to ensure secure fixation, then reliability improves, but the profile size increases making installation more difficult
Solution Approach 1:
The anchor member is nested within the coupling device structure. The spherical head of the anchor member fits into a receiving cavity, and the shank portion extends through a passage in the coupling device. This nesting arrangement allows the anchor member to be compact and low-profile while maintaining sufficient size for secure bone fixation, as the critical anchoring portion is contained within the overall assembly footprint.
Data Source
AI summary
A coupling device for securing an elongate member to the spine is provided. The coupling device comprises a compressible inner member that secures an anchor member therein when the inner member is axially shifted within an outer member. The elongate member is retained within the device by an axially inserted locking member, and may be secured independently of the anchor member. The coupling device and anchor may be configured to provide increased angulation of the anchor with respect to the coupling device. For instance, anchor member may have an offset head portion in order to provide normal pivoting of the coupling device when the anchor is attached to bone at an angle.