Ratcheted Spinal Device with Variable-Length Rod
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Solution Overview
Problem
Current spinal implant procedures for scoliosis often fail to perfectly correct spinal deformity and require long-term fusion, which is not desirable, and are prone to failures due to limitations in rod length adjustment and stability.
Innovation Solution
A ratcheted spinal device with a variable-length member and a ratchet mechanism that can be configured for lengthening, shortening, or locking, using polyaxial-joint attachment members and a controller to manage the ratchet mechanism, allowing for precise adjustment and stability through various operative configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a long fusion rod is used to force the deformed spine into a healthy position, then spinal deformity correction is achieved, but the procedure requires long-term fusion which is not desirable and has severe shortcomings
Solution Approach 1:
The spinal rod is designed with a ratchet mechanism that allows it to transition from a static, fixed-length structure to a dynamic, adjustable-length structure. The rod can be incrementally lengthened or shortened by rotating the adjustment mechanism, enabling dynamic correction of spinal deformity without requiring permanent long-term fusion. This dynamic capability allows the spine to be gradually guided into proper alignment while maintaining the option to adjust the correction over time.
Solution Approach 2:
The spinal rod is segmented into adjustable sections with a variable-length member that can be independently modified. The ratchet mechanism divides the adjustment process into discrete incremental steps, allowing precise control over the rod length. This segmentation enables the surgeon to make small, controlled adjustments rather than committing to a single fixed length, thereby reducing the need for extensive long-term fusion.
2Ease of manufacture
If the rod length is fixed during surgery, then the procedure is simpler, but the deformation is rarely perfectly corrected and failures are not uncommon
Solution Approach 1:
The rod incorporates a ratchet mechanism with pawls and teeth that allows post-installation adjustment of rod length. The mechanism maintains structural integrity while enabling incremental length changes through controlled pawl rotation. This dynamic adjustment capability provides precision in deformity correction without significantly complicating the initial surgical procedure, as the rod can be initially installed and then fine-tuned afterward.
Solution Approach 2:
The rod's length parameter can be changed after implantation by rotating the adjustment mechanism. The ratchet mechanism allows the rod length to be modified in discrete increments, enabling precise adjustment to achieve optimal spinal alignment. This parameter change capability transforms the rod from a fixed-dimensional component to an adjustable one, improving correction precision while maintaining procedural simplicity.
3Manufacturing precision
If a ratchet mechanism is added to allow rod length adjustment, then deformity correction precision is improved, but the device complexity increases
Solution Approach 1:
The ratchet mechanism is merged with the rod structure itself, with the variable-length member integrated into the rod body. The pawls and teeth are incorporated as part of the rod's internal architecture rather than separate components. This merging reduces overall device complexity by eliminating the need for additional adjustment mechanisms while still providing precise length adjustment capability through the integrated ratchet system.
Solution Approach 2:
The ratchet mechanism serves multiple functions: it enables rod length adjustment, provides locking capability to maintain selected length, and allows for incremental positioning. The same mechanism that enables precision adjustment also provides structural integrity and stability. This multi-functionality reduces the need for separate components, thereby managing device complexity while achieving precise deformity correction.
4Adaptability or versatility
If the ratchet mechanism is activated to change rod length, then adaptability to different spinal configurations is improved, but the stability of the rod system may be compromised
Solution Approach 1:
The ratchet mechanism incorporates a locking feature with pawls that engage with teeth on the rod body. This locking mechanism acts as a cushion or safeguard that prevents unintended rod length changes while allowing deliberate adjustments. The pawls are positioned to automatically lock the rod at each incremental position, providing stability before and after adjustment. This beforehand cushioning ensures that the rod remains stable during normal use while maintaining adaptability when adjustment is intentionally initiated.
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 enables precise correction of spinal deformity by allowing incremental length adjustments and stability, reducing the need for long-term fusion and minimizing failure rates by providing flexible and secure attachment to the spine.
Implementation Method 1
a ratchet mechanism that has an operative configuration that allows a change in length of the variable-length member in one direction and prevents a change in length of the variable-length member in an opposite direction
Implementation Method 2
at least one of the polyaxial-joint attachment members includes a ball-and-socket joint
Implementation Method 3
polyaxial-joint attachment members for attachment to bone, which permit pivoting movement of the attachment members about more than one pivoting axis
Implementation Method 4
the worm gear can be activated by a shaft, through a percutaneous procedure
Implementation Method 5
a biasing device is operative to apply an urging force on the variable-length member
Data Source
AI summary
A ratcheted spinal device including a variable-length member including a ratchet mechanism that has an operative configuration that allows a change in length of the variable-length member in one direction and prevents a change in length of the variable-length member in an opposite direction, wherein the variable-length member includes polyaxial-joint attachment members for attachment to bone, which permit pivoting movement of the attachment members about more than one pivoting axis.