Spinal Derotation Apparatus Force Distribution
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Solution Overview
Problem
Current derotation systems for spinal irregularities, such as scoliosis, face challenges in securely connecting to multiple implants and efficiently distributing correction forces, leading to potential bone fastener breaching and loss of fixation, which can result in paralysis and further degenerative changes in the spine.
Innovation Solution
A derotation apparatus comprising a tube assembly with an inner and outer sleeve, a ball joint assembly, and a handle assembly, allowing secure attachment to implants and efficient coupling of multiple derotation apparatuses through a coupling rod, distributing forces across multiple screws to reduce the risk of breaching and improve fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current derotation systems use tubes that slot over implants to apply counter torque, then vertebral rotation can be corrected, but high forces are applied to individual screws which can lead to bone fastener breaching and loss of fixation
Solution Approach 1:
The system segments the force application by using multiple tubes (at least two) that can be connected together, distributing the corrective force across multiple bone fasteners rather than concentrating it on a single screw, thereby reducing the risk of breaching while maintaining derotation effectiveness
Solution Approach 2:
Multiple tubes are merged or connected together to form a unified derotation system that acts as a single mechanical unit, allowing force distribution across multiple attachment points while maintaining coordinated action for vertebral derotation
2Reliability
If multiple tubes are linked together to distribute force across multiple screws, then the risk of bone fastener breaching is reduced, but the process becomes time consuming and requires separate instruments to assemble and tighten
Solution Approach 1:
Multiple tubes are merged into a single integrated assembly that can be attached to multiple bone fasteners simultaneously, eliminating the need for separate assembly steps and instruments for each tube while maintaining force distribution across multiple screws
Solution Approach 2:
The tube assembly is designed with multi-functionality, serving both as the derotation mechanism and as the connection structure for multiple bone fasteners, eliminating the need for separate assembly instruments and reducing procedural time
3Shape
If derotation systems apply corrective forces to straighten lateral curvature, then spinal alignment is improved, but flat back syndrome and degenerative changes in the lower lumbar spine can result
Solution Approach 1:
The derotation system applies localized corrective forces at specific vertebral levels through individually attachable tubes, allowing precise control over which segments are derotated while preserving natural sagittal alignment and avoiding excessive lumbar lordosis that could cause flat back syndrome
Data Source
AI summary
Treatment of spinal irregularities, including, in one or more embodiments, derotation apparatus and systems that can be used to reduce the rotation of vertebral bodies. Derotation apparatus that may comprise a tube assembly comprising an inner sleeve and an outer sleeve disposed over the inner sleeve. The inner sleeve may have a distal end for attachment to an implant. The tube assembly may further comprise a handle assembly. The tube assembly may further comprise a ball joint assembly disposed between the tube assembly and the handle assembly. The ball joint assembly may comprise a ball joint configured for attachment to a coupling rod. The ball joint assembly further may comprise a reducing extension below the ball joint, the reducing extension being sized to fit in a central bore of the inner sleeve. Orthopedic fixation devices comprising a ball joint are also disclosed.