Intervertebral Sizing Instrument with Independent Height and Angle Adjustment
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Solution Overview
Problem
Current methods for determining the height and lordotic angle of intervertebral devices during spinal fusion procedures often result in a loss of correspondence between sizing trials and the actual implanted device, affecting the efficacy of the spinal fusion.
Innovation Solution
A sizing instrument with first and second arms that allow independent movement to adjust the separation and angle of superior and inferior endplates, enabling precise determination of the desired height and angle within the intervertebral space, which can then be used to select a corresponding core for implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If trial intervertebral devices with surface markings are used for height and angle trials, then sizing can be performed, but the trial devices cannot be used for implantation due to unsuitable structure and markings
Solution Approach 1:
The intervertebral device is divided into separate components: a reusable trial assembly with height and angle adjustment mechanisms, and a separate implantable core. The trial assembly can be removed after sizing and a different assembly used for implantation, allowing the trial function and implantation function to be separated.
Solution Approach 2:
A trial assembly acts as an intermediary tool between sizing and implantation. This assembly includes the endplates and adjustment mechanisms that allow precise height and angle determination, but is not itself implanted. Instead, it guides the selection and positioning of the implantable core.
2Measurement precision
If multiple trial devices are changed to find appropriate height and angle, then sizing can be performed, but time is lost in repeated trials
Solution Approach 1:
The trial assembly incorporates dynamic adjustment mechanisms that allow height and angle to be changed continuously and independently during a single trial. The second arm can be moved along different paths to adjust height via height adjustment controls or angle via trigger mechanisms, eliminating the need to change entire trial devices.
Solution Approach 2:
The system allows independent adjustment of height and angle parameters during the trial process. Height can be adjusted by moving the second arm along specific paths while angle is adjusted by moving the second arm along different paths, enabling precise parameter optimization without repeated device changes.
3Device complexity
If a unitary trial device is used for both trial and implantation, then device simplicity is maintained, but sizing accuracy is compromised due to inability to make precise adjustments
Solution Approach 1:
The device is segmented into a trial assembly with complex adjustment capabilities and a simpler implantable core. The trial assembly's complexity is justified only during the sizing phase, after which the simpler core is implanted, resolving the contradiction between trial precision and implant simplicity.
Data Source
AI summary
An assembly for determining height and angle of an intervertebral device to be implanted in an intervertebral space. The assembly comprises a sizing instrument (12) comprising a support (18) attached to first and second arms (20), (22) which extend in generally a same direction from the support. The assembly also comprises superior and inferior endplates (14), (16) of the intervertebral device to be implanted. One of the superior and inferior endplates (14), (16) engages with a distal end of the first arm (20) and the other of the superior and inferior endplates (14), (16) engages with a distal end of the second arm (22), the superior and inferior endplates opposing each other when they are engaged with their respective arms. The distal end of the second arm (22) performs first and second forms of movement relative to the distal end of the first arm (20), the first and second forms of movement being independent of each other, the distal end of the second arm moving along different respective paths in the first and second forms of movement, the first form of movement changing separation between the superior and inferior endplates (14), (16), and the second form of movement changing an angle between the superior and inferior endplates (14), (16). The support (18) comprises a user control which is mechanically coupled to at least the second arm (22) of the first and second arms to provide upon user operation of the user control each of the first and second forms of movement of the distal end of the second arm.