Polyaxial Vertebral Fixation Assembly for Spinal Alignment
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Solution Overview
Problem
Existing vertebral fixation methods, such as translaminar facet screws and pedicle screws, face challenges in aligning and securely attaching adjacent vertebral bodies without causing misalignment or twisting, particularly due to the difficulty in inserting rods and the counterproductive lag force introduced by threading translaminar facet screws into pedicle screws.
Innovation Solution
A vertebral fixation assembly featuring a polyaxial head with three rotational degrees of freedom, allowing for a ball-and-socket joint connection between a pedicle screw and a translaminar facet anchor, which is inserted through a predrilled hole in the lamina and secured with a set screw, maintaining natural spinal alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rod is inserted to connect pedicle screws, then vertebral bodies can be fixed, but the procedure becomes time-consuming and requires larger incisions
Solution Approach 1:
The fixation system is divided into separate components: a pedicle screw with polyaxial head in one vertebra, and a translaminar facet screw in another vertebra. These segments connect through facet joint anatomy rather than requiring a continuous rod, simplifying the connection process and reducing surgical time.
Solution Approach 2:
The facet joint serves as an intermediary structure that naturally connects the two vertebral bodies. By utilizing the existing facet joint anatomy as the connection pathway, the system eliminates the need for complex rod-linking procedures while maintaining fixation stability.
2Ease of manufacture
If translaminar facet screw is threaded into pedicle screw head, then connection is achieved, but alignment precision is compromised and vertebral twisting occurs
Solution Approach 1:
The polyaxial head of the pedicle screw features a spherical or rounded geometry that accommodates the translaminar facet screw at multiple angles. This spheroidal design allows the facet screw to connect without requiring perfect alignment, preventing vertebral twisting while maintaining connection ease.
Solution Approach 2:
The connection system incorporates rotational degrees of freedom, allowing the facet screw to dynamically adjust its angle relative to the pedicle screw. This dynamic capability enables the system to adapt to anatomical variations and maintain precise vertebral alignment during the connection process.
Data Source
AI summary
An apparatus configured to attach a first vertebral body and a second vertebral body is disclosed. The apparatus includes a fastener including an anchor and a polyaxial head rotatably attached to the anchor, the anchor configured to be fastened to the first vertebral body, and an anchor assembly configured to be received in an aperture of the second vertebral body. The anchor assembly is configured to be received in a head aperture of the polyaxial head. The polyaxial head has three rotational degrees of freedom relative to the anchor based on the rotatable attachment of the polyaxial head to the anchor.