Spinal Cable Tensioning Mechanism for Deformity Correction
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Solution Overview
Problem
Conventional implants for correcting spinal curvature deformities are invasive, lead to potential neurologic damage, and do not effectively support large spinal loads, causing fatigue failure and inadequate correction due to their rigid structure and lack of consideration for viscoelastic properties of spinal tissues.
Innovation Solution
A device comprising a cable system with a tension member, leadscrew, and engaging members that allow for adjustable tension and rotational movement, enabling incremental corrective displacement of vertebrae without fusion, using a biocompatible material and magnetic actuation to minimize invasiveness and support spinal realignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rigid metal rods and plates are used to attach to the spine, then structural strength and stability are improved, but the risk of fatigue failure increases under large spinal loads
Solution Approach 1:
The patent changes the mechanical parameters of the implant by using a flexible rod instead of a rigid rod, allowing the implant to bend and deform under load rather than maintaining a fixed rigid structure. This parameter change from rigidity to flexibility resolves the contradiction by enabling the implant to withstand large spinal loads without fatigue failure while still providing sufficient structural support.
Solution Approach 2:
The patent employs composite construction by combining flexible rod material with bone graft material in a layered configuration. The flexible rod provides structural support while the bone graft material integrates with the vertebral bodies, creating a composite structure that distributes loads more effectively and reduces stress concentration on the implant, thereby improving fatigue resistance.
2Stability of the object's composition
If stiff instrumentation is used for spinal correction, then immediate structural support is improved, but the ability to accommodate viscoelastic deformation of spinal tissues is worsened
Solution Approach 1:
The patent applies dynamics by designing the spinal instrumentation to transition from a static rigid structure to a dynamic flexible structure that can adapt its configuration. The flexible rod can bend and deform dynamically in response to the viscoelastic properties of spinal tissues, allowing the system to maintain structural stability while accommodating time-dependent tissue deformation and stress relaxation.
Solution Approach 2:
The patent changes the mechanical parameter of the instrumentation from high stiffness to flexible, enabling the implant to deform elastically under load. This parameter change allows the instrumentation to accommodate the viscoelastic deformation of spinal tissues including intervertebral discs and ligaments, while still providing sufficient structural support to maintain spinal alignment.
3Reliability
If extensive discectomies and bone graft harvest are performed, then bone fusion is improved, but the invasiveness and potential for neurologic damage increase
Solution Approach 1:
The patent extracts the bone graft material from the traditional harvest sites (such as iliac crest) and places it directly into the intervertebral space between vertebral bodies. This extraction and repositioning of the bone graft eliminates the need for extensive discectomies and reduces surgical invasiveness, thereby lowering the risk of neurologic damage while maintaining effective bone fusion.
Solution Approach 2:
The flexible rod acts as an intermediary structure that maintains spinal alignment and distributes mechanical loads during the bone fusion process. This intermediary support reduces the need for aggressive surgical maneuvers to achieve fusion, allowing for a more conservative surgical approach that minimizes neurologic risk while still promoting successful bone graft incorporation.
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 allows for non-invasive or minimally invasive correction of spinal deformities, reducing the risk of neurologic damage and fatigue failure, while effectively realigning the spine to eliminate force imbalances, potentially avoiding the need for spinal fusion and promoting permanent curvature correction.
Implementation Method 1
a tension member having a cylindrical magnet, a leadscrew and a body
Data Source
AI summary
A device for correction of a spinal deformity. In one embodiment, the device includes a cable having a first end portion, and an opposite, second end portion attachable to a vertebra, and means for adjusting the tension of the cable so as to impose a corrective displacement on the vertebra.