Vertebral Body Replacement Device With Rotational Adjustment
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Solution Overview
Problem
Current spinal implants lack adjustability, leading to torsional forces during lengthening, improper sizing, limited access for height manipulation, and inadequate endplate angulation, which can result in neurologic injury and improper spinal alignment.
Innovation Solution
A vertebral body replacement device with a central rod member and end members that inhibit rotational movement, allowing for 360-degree adjustment to maintain optimal spacing between vertebral bodies, featuring threaded portions for axial movement and a footplate member for secure engagement with vertebral bodies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If spinal implants are designed with fixed overall length and implanted without adjustment capability, then device simplicity is maintained, but improper sizing and inadequate adaptability to clinical space occur
Solution Approach 1:
The spinal implant incorporates a dynamic adjustment mechanism that allows the overall length to be modified in situ. The device includes threaded rod members that can be rotated to advance or retract end members, thereby adjusting the implant length to match the specific clinical space requirements without requiring multiple fixed-size implants.
Solution Approach 2:
The implant enables parameter changes by allowing adjustment of the overall length through rotational movement of the central rod member. This changes the dimensional parameter of the implant to adapt to different vertebral body dimensions and spinal column requirements, improving versatility while maintaining a relatively simple device structure.
2Adaptability or versatility
If spinal implants are lengthened in vivo by rotary motion, then adaptability to clinical space is improved, but torsional forces are applied to the implant risking neurologic injury
Solution Approach 1:
The implant is segmented into distinct functional components: a body member, a separate central rod member with threaded portions, and end members. This segmentation allows the adjustment mechanism to be isolated within the body member while the end members remain stable, reducing torsional forces transmitted to the spinal column during lengthening.
Solution Approach 2:
The threaded rod member acts as an intermediary mechanism that converts rotational motion into linear displacement of the end members. By using the threading mechanism as a mediator, the adjustment is achieved through controlled engagement of threads rather than direct rotary motion of the end members, thereby minimizing torsional forces applied to the implant-vertebral body interface.
3Ease of operation
If spinal implants have limited device access ports for height manipulation, then device simplicity is maintained, but ease of operation for lengthening and shortening is reduced
Solution Approach 1:
The body member serves multiple functions: it acts as the structural core of the implant, provides the adjustment mechanism through internal threaded rod members, and incorporates access ports for tool insertion. The access ports enable surgeons to insert tools through the body member to rotate the central rod member and adjust the implant length, providing ease of operation without significantly increasing device complexity.
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 device eliminates torsional forces, ensures precise height maintenance, and provides comprehensive access for length adjustment, reducing the risk of neurologic injury and improving spinal alignment.
Implementation Method 1
The vertebral body replacement device also includes a central rod member that has two threaded portions; the central rod member is configured to be operatively associated within the body member
Data Source
AI summary
The vertebral body replacement device includes a body member and a central rod member that has two threaded portions and is configured to be operatively associated with the body member. The device also includes a first end member and a second end member with the end members being configured to threadingly engage the threaded portions of the central rod member. The body member and the two end members are further constructed to inhibit rotational movement of the two end members when the device is positioned within a space within a spine as the two end members will engage the adjacent respective vertebral bodies following rotational actuation of the central rod member causing the end members to move in an axial direction relative to the body member, thereby allowing the two end members to apply a force to the two vertebral bodies. A surgical method using the device is also disclosed.