Expandable Interbody Cage for Lumbar Fusion
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Solution Overview
Problem
Current posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) techniques are limited by the size of the interbody cage, which restricts surface area contact with adjacent vertebrae, leading to inadequate correction of segmental lordosis and sagittal imbalance, and increased risk of cage subsidence.
Innovation Solution
The development of an interbody cage with medio-lateral expansion capability, featuring upper and lower mechanisms with overlapping or angularly adjacent plates that can move laterally to increase surface area contact with adjacent vertebrae, thereby enhancing deformity correction and fusion success while reducing subsidence risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a traditional interbody cage is used in PLIF or TLIF procedures, then the surgical approach is simple and the cage can be inserted through a single posterior approach, but the cage size is limited due to the presence of the thecal sack and emerging nerve roots, resulting in reduced surface area contact with vertebrae
Solution Approach 1:
The cage incorporates expandable mechanisms at the top and bottom that allow the cage to transition from a compact inserted state to an expanded state with increased surface area contact with the vertebrae. This dynamic expansion capability resolves the contradiction by enabling a simple insertion procedure while achieving enhanced surface area contact after deployment.
Solution Approach 2:
The cage expansion occurs in the medio-lateral dimension, increasing the surface area contact with the vertebral endplates from the front and back surfaces. This dimensional expansion allows the cage to achieve greater contact area without increasing the anterior-posterior or superior-inferior dimensions, thus resolving the contradiction between surface area and structural complexity.
2Ease of operation
If the cage size is limited due to the presence of the thecal sack and emerging nerve roots, then the surgical approach remains safe and simple, but the ability to achieve adequate correction of segmental lordosis and sagittal imbalance is reduced
Solution Approach 1:
The expandable cage allows the surgeon to maintain a simple posterior approach for insertion while enabling enhanced deformity correction capability after the cage is deployed. The expansion mechanisms allow the cage to adapt to different deformity patterns and achieve adequate correction of segmental lordosis and sagittal imbalance without complicating the surgical approach.
Solution Approach 2:
The cage design allows for changes in the surface area contact parameter after insertion through controlled expansion. This parameter change enables the cage to provide adequate correction of deformities while maintaining the simplicity of the surgical approach, as the expansion occurs after the safe insertion is completed.
3Reliability
If the cage surface area contact is reduced, then the cage can be easily inserted through a single posterior approach, but the risk of cage subsidence increases
Solution Approach 1:
The cage incorporates expandable mechanisms that increase the surface area contact with the vertebrae after insertion, thereby reducing the risk of cage subsidence. The dynamic expansion occurs after the simple posterior approach insertion is completed, resolving the contradiction between subsidence resistance and mechanism complexity.
Solution Approach 2:
The cage is inserted in a compact state through the simple posterior approach, and then the expansion mechanisms are activated to increase surface area contact before the cage bears the full load. This preliminary expansion action reduces subsidence risk without requiring a complex surgical approach, as the expansion occurs after insertion but before load-bearing.
Data Source
AI summary
A device for interbody vertebral fusion is constructed of a cage supporting a plurality of upper plates on a top of the cage and supporting a plurality of lower plates on a bottom of the cage. An expansion mechanism is operatively connected between the cage and the upper plates and the lower plates. The expansion mechanism is operable to cause the plurality of upper plates to move to side-by-side relative positions increasing their combined surface area and to cause the plurality of lower plates to move to side-by-side relative positions increasing their combined surface area.