Expandable Bone Fastener for Spinal Rod Adjustment
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Solution Overview
Problem
Current spinal implant systems face challenges in adjusting spinal constructs during surgery without compromising the bone-screw interface strength or causing screw pull-out, particularly in accommodating the position of spinal rods relative to vertebrae, which limits flexibility and stability in treating spinal disorders.
Innovation Solution
A modular spinal implant system featuring a bone fastener with an adjustable pedicle screw system that allows for in-situ assembly without instrumentation, utilizing a screw shaft assembly and head assembly that can expand to adjust the position of the implant cavity relative to the tissue, enabling secure attachment of spinal rods without the need for rod bending or loss of interface strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If spinal rods are attached to vertebrae using fixed-position bone fasteners, then the attachment is stable, but the flexibility to adjust rod position relative to vertebrae is lost
Solution Approach 1:
The bone fastener incorporates an expandable mechanism that transitions from a compressed delivery state to an expanded deployed state. The distal portion of the fastener body can radially expand after insertion, allowing the implant cavity to be positioned at multiple locations relative to the vertebra while maintaining secure attachment. This dynamic transformation enables post-insertion adjustment of rod position without compromising the stability of the bone-screw interface.
2Adaptability or versatility
If spinal constructs are adjusted during surgery by traditional methods, then rod position can be changed, but bone-screw interface strength is compromised or screw pull-out occurs
Solution Approach 1:
The bone fastener is divided into distinct functional segments: a proximal portion that engages the vertebra, a distal expandable portion that provides adjustment capability, and an implant cavity that receives the rod. This segmentation allows the proximal segment to maintain strong bone engagement while the distal segment provides mechanical advantage for adjusting rod position without affecting the bone-screw interface strength.
Solution Approach 2:
The expandable mechanism allows the fastener to transition from a compact delivery configuration to an expanded operational configuration. Once expanded, the fastener provides stable anchorage that prevents screw pull-out while enabling safe adjustment of the spinal construct during surgery through controlled expansion and locking mechanisms.
3Ease of manufacture
If bone fasteners are delivered with fixed implant cavities, then the delivery is simple, but the ability to accommodate varying rod positions is limited
Solution Approach 1:
The expandable bone fastener employs a nested structure where the distal expandable portion is contained within or alongside the proximal portion during delivery. The fastener is delivered in a compressed or collapsed state through the delivery system, then deployed by expanding the distal portion at the target site. This nesting approach maintains delivery simplicity while enabling post-deployment adaptation to various rod positions.
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 system provides flexible adjustment of spinal constructs during surgery, ensuring secure attachment of spinal rods to vertebrae while minimizing pre-load on the vertebrae, thus enhancing stability and reducing the risk of screw pull-out, thereby effectively treating spinal disorders such as degenerative disc disease and curvature abnormalities.
Implementation Method 1
engaging the second member such that the members expand to adjust position of the implant cavity relative to the tissue
Data Source
AI summary
A bone fastener comprises a first member defining an implant cavity. A first part is disposed with the implant cavity and engageable with an implant. A second member is configured to penetrate tissue and includes a mating surface engageable with the first member such that the members are expandable. Implants, spinal constructs, systems, instruments and methods are disclosed.