Adjustable Interbody Spinal Cage for Uniform Bone Interface Pressure
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Solution Overview
Problem
Existing interbody spinal cages face issues with uneven bone-cage interface pressure distribution leading to poor bone growth, necessitating complex and invasive post-surgical adjustments.
Innovation Solution
A telescoping interbody spinal cage with variable length rods and extensible shells that allow non-invasive adjustment to conform to vertebral bone contours, using actuators and sensors to optimize contact pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the cage dimensions are fixed based on pre-surgery imaging, then the surgical procedure is simplified, but the cage cannot adapt to post-surgical bone growth and uneven bone-cage interface pressure
Solution Approach 1:
The cage incorporates variable length rods with telescoping inner and outer tubes that can dynamically adjust their length. The inner tube can slide within the outer tube to change the effective length of the rod, allowing the cage to adapt its dimensions post-surgery to match bone growth and achieve uniform pressure distribution at the bone-cage interface.
Solution Approach 2:
The variable length rod employs a nested structure where an inner tube is received within an outer tube. This nested configuration allows the inner tube to telescope within the outer tube, enabling length adjustment while maintaining a compact form factor that simplifies the initial surgical implantation procedure.
2Reliability
If the cage dimensions are adjusted post-surgery to optimize bone growth, then uniform pressure distribution is achieved, but complex additional surgery is required
Solution Approach 1:
The patent replaces complex mechanical surgical adjustment procedures with a simpler actuation system. A tube actuator, which may be driven by motors, hydraulics, or pneumatics, is used to extend or retract the inner tube within the outer tube, enabling dimension adjustment through controlled actuation rather than invasive surgical intervention.
Solution Approach 2:
The cage dimension adjustment is achieved by changing the length parameter of the variable length rods. By controlling the extension or retraction of the inner tube relative to the outer tube, the effective length of the rod changes, thereby adjusting the cage dimensions to optimize bone-cage interface pressure distribution for reliable bone growth.
3Ease of operation
If the patient undergoes general anesthesia for cage adjustment, then the procedure can be performed, but confounding factors remain and patient discomfort increases
Solution Approach 1:
The cage adjustment system is designed to be self-actuated or remotely actuated after implantation. The tube actuator can be controlled to adjust the variable length rods without requiring the patient to undergo general anesthesia again, enabling the patient to benefit from cage adjustment while avoiding the harmful effects of repeated anesthesia exposure.
4Ease of manufacture
If fixed-length rods are used in the cage, then the manufacturing is simpler, but the cage cannot conform to uneven bone surfaces and achieve uniform contact pressure
Solution Approach 1:
Instead of manufacturing rods with fixed lengths, the patent employs variable length rods with telescoping tubes that can dynamically adjust their length. This dynamic capability allows the cage to conform to uneven bone surfaces and achieve uniform contact pressure distribution, while the manufacturing of the individual tube components remains relatively simple.
Data Source
AI summary
An interbody spinal cage when implanted can be manipulated non-invasively to change dimensions conforming to contours of adjacent vertebral bones. The interbody spinal cage includes a flexible shell that encases multiple variable-length rods. Each of the multiple variable-length rods includes telescoping tubes and an actuator for increasing and decreasing the length of the telescoping tubes. Each of the variable-length rods includes a retention member to limit movements of the telescoping tubes, wherein the retention member can be engaged and disengaged. Both the retention member and the actuator can be operated from outside the body in which the interbody spinal cage is implanted.