Posterior Prosthetic Disc for Minimally Invasive Spinal Replacement
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Solution Overview
Problem
Conventional spinal fusion procedures lead to degenerative changes in adjacent mobile segments due to altered biomechanical environment, causing increased motion and stress on adjacent discs, which results in long-term degeneration.
Innovation Solution
Prosthetic intervertebral discs with upper and lower end plates separated by a compressible core member, held together by high tenacity fibers, designed for minimally invasive surgical implantation using a posterior approach, mimicking the functional characteristics of a natural disc to maintain biomechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spinal fusion is performed to treat herniated disc, then short-term pain relief is achieved, but long-term degenerative changes occur in adjacent mobile segments due to altered biomechanical environment
Solution Approach 1:
The patent extracts and removes the damaged disc material (nucleus pulposus and annulus fibrosus) from the spinal column, eliminating the source of pain and herniation while preserving the adjacent mobile segments. By taking out only the problematic disc and replacing it with a prosthetic device, the harmful biomechanical changes that would affect adjacent segments are prevented.
Solution Approach 2:
The prosthetic intervertebral disc changes the biomechanical parameters of the spinal segment by providing controlled motion and stress distribution. The device maintains appropriate flexibility and load-bearing characteristics that mimic natural disc behavior, preventing the excessive motion and stress that would otherwise occur in adjacent segments after fusion.
2Strength
If a spacer is inserted and secured with screws and plates to fuse vertebrae, then structural stability is achieved, but the biomechanical environment is altered leading to increased motion and stress on adjacent discs
Solution Approach 1:
The prosthetic disc provides localized structural support and stability at the specific intervertebral level where it is implanted, without creating the rigid fusion that would alter biomechanics throughout the entire spinal column. The device maintains local stability while preserving natural motion characteristics in adjacent segments.
Solution Approach 2:
The prosthetic intervertebral disc introduces dynamic characteristics to the spinal segment, allowing controlled motion and flexibility rather than rigid fixation. This dynamic behavior enables the device to adapt to physiological movements while distributing stresses appropriately, preventing excessive loading on adjacent discs.
3Reliability
If conventional surgical approaches are used to implant prosthetic discs, then complete disc replacement is achieved, but the surgical complexity and invasiveness increase
Solution Approach 1:
The prosthetic disc is segmented into separate components including an outer cage structure and an inner nucleus component. This segmentation allows the device to be assembled and implanted through a minimally invasive posterior approach, reducing surgical complexity while achieving complete disc replacement. The modular design enables easier insertion and positioning compared to monolithic prosthetics.
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 prosthetic discs effectively replace damaged discs, reducing stress on adjacent segments and maintaining biomechanical stability, thereby preventing long-term degeneration and alleviating pain or paralysis associated with herniated discs.
Implementation Method 1
The core member may be compressed in the axial direction between the upper and lower end plates
Implementation Method 2
The fiber annulus may be pre-stressed in the radial direction prior to insertion into the intervertebral space
Data Source
AI summary
Spinal implants are described that may be surgically implanted into the spine to replace damaged or diseased discs using a posterior approach. The implants are prosthetic devices that can approach or mimic the physiological motion and reaction of the natural disc. The implants are adapted to be used in minimally invasive surgical procedures.