Dynamic Implant Fixation Plate for Load Sharing and Bone Growth
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Solution Overview
Problem
Existing medical implants often hinder natural bone growth and integration due to rigid attachments that shield bones from stress, leading to weaker new bone growth and potential bone loss, while also restricting necessary movement and stability.
Innovation Solution
A dynamic implant fixation plate with a lattice structure that allows for at least one degree of freedom, using a concave-convex screw head interface and clearance fit with the implant, enabling axial compression and preventing lateral movement, while promoting osteointegration and new bone growth through optimized pore and interconnection sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a rigid attachment is used between the implant and bone, then stability is improved, but stress shielding occurs leading to weaker bone growth and potential bone loss
Solution Approach 1:
The fixation plate transitions from a rigid static attachment to a dynamic system that allows controlled motion. The concave-convex interface between the screw head and screw hole enables rotational and translational degrees of freedom, allowing the implant to adapt to bone movement and stress changes, thereby preventing stress shielding while maintaining stability
Solution Approach 2:
The patent changes the mechanical parameters of the connection interface by introducing a clearance fit (greater than zero) between the bone screw head and fixation plate screw holes. This clearance allows the system to transition from a rigid connection to one with controlled compliance, enabling stress transfer that promotes bone growth without compromising stability
2Stability of the object's composition
If a fixed position implant is used, then stability is improved, but necessary movement and osteointegration are restricted
Solution Approach 1:
The fixation plate is designed with dynamic characteristics, allowing it to move and rotate relative to the implant through the concave-convex interface. This enables the implant to accommodate physiological movements and promote osteointegration while maintaining adequate stability through the controlled degrees of freedom
Solution Approach 2:
The system is segmented into multiple components (implant, fixation plate, bone screws) with independent degrees of freedom. The fixation plate can rotate and move relative to both the implant and the bone, creating a hierarchical structure that allows movement at the plate level while maintaining overall stability
3Strength
If a rigid fixation plate is used, then load-bearing capacity is improved, but bone growth and integration are hindered
Solution Approach 1:
The patent changes the stiffness parameter of the fixation system by introducing compliance through the clearance fit and concave-convex interface. This allows the fixation plate to maintain sufficient load-bearing capacity while transferring appropriate stress to the bone to stimulate growth, avoiding the harmful effects of rigid fixation
4Adaptability or versatility
If clearance fit is introduced between screw head and screw hole, then degrees of freedom are improved, but binding between components may occur
Solution Approach 1:
The patent optimizes the clearance fit parameter to be greater than zero but within specific tolerances. This controlled clearance allows the bone screw head to move freely within the fixation plate screw hole, providing degrees of freedom while preventing excessive binding through proper dimensional design and tolerance specification
Data Source
AI summary
The dynamic implant fixation plate and implant configured to accept the disclosed fixation plate can, in some aspects, provide a means of fixing an implant relative one or more planes while allowing motion relative to one or more planes. The use of the disclosed fixation plate and corresponding implant can reduce the occurrence of stress shielding and permit enhanced loading of the implant site.