Expandable Spinal Implant With Distal Hook Load Distribution
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Solution Overview
Problem
Existing expandable interbody devices inhibit bone growth-promoting material introduction and suffer from subsidence due to inadequate load-bearing surfaces, necessitating additional surgical interventions.
Innovation Solution
An expandable spinal implant with a frame and movable endplates that expand outward, featuring a distal hook configuration to engage vertebral foramina and apophyseal rims, providing increased surface area and load-bearing capacity, and allowing post-expansion introduction of bone growth-promoting materials through a cannulated shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If expandable interbody devices are used to provide additional spacing and curvature restoration, then the implant can be introduced in a collapsed state and expanded to produce spacing, but internal mechanisms inhibit the introduction of bone growth promoting material after expansion
Solution Approach 1:
The implant is divided into distinct functional components: an expandable cage structure for spacing, a separate plug component for material delivery, and a delivery system. This segmentation allows the expansion mechanism and material introduction to occur through separate access points, resolving the conflict between expansion capability and material introduction ease
Solution Approach 2:
A separate plug component acts as an intermediary element that can be introduced through the distal aperture after expansion. The plug serves as the mediator through which bone growth promoting materials are delivered into the expanded cage, bypassing the internal expansion mechanisms that would otherwise block direct material introduction
2Device complexity
If existing interbody devices are used with relatively small surface areas, then the implant structure remains compact, but subsidence of spinal surfaces occurs due to inadequate load-bearing surfaces
Solution Approach 1:
The endplates are designed with anterior portions that extend in a specific dimension to create distal end hook portions. This dimensional extension increases the load-bearing surface area and provides anterior hooking engagement with vertebral bodies, enhancing reliability without significantly increasing overall device complexity
Solution Approach 2:
The endplates feature asymmetric design with anterior portions extending further than posterior portions, creating distal end hook portions that engage anteriorly with vertebral bodies. This asymmetric configuration optimizes load distribution and prevents subsidence by anchoring the implant to the anterior vertebral rims, improving reliability while maintaining compact structure
3Reliability
If follow-on surgery is performed to address subsidence, then the subsidence problem can be corrected, but additional surgical interventions increase patient morbidity and treatment time
Solution Approach 1:
The implant is designed with pre-configured distal end hook portions and extended endplate surfaces that are prepared in advance to engage with vertebral bodies. This preliminary configuration ensures adequate load-bearing capacity from the first implantation, preventing subsidence before it occurs and eliminating the need for follow-on corrective surgeries, thereby reducing total treatment time and patient morbidity
Data Source
AI summary
An expandable spinal implant includes a distal projection extending from only one side of the implant, ending in an anterior tip, the anterior portion and anterior tip defining an elongated distal end hook, which is wider than the proximal end. The distal end hook rotates around the spinal cord, aligning the implant with a desired pathway, then inserts into place in the disc space between the vertebrae. The elongated widened distal end hook provides a TLIF approach, distributes loads, provides anterior rim engagement, and creates lordosis.