Stemless Semi-Constrained Interphalangeal Implants for Predictable Motion
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Solution Overview
Problem
Current interphalangeal joint arthroplasty devices suffer from high failure rates, stiffness, and unpredictable motion outcomes due to reliance on durable and reliable arthroplasty alternatives, leading to permanent functional loss and potential amputation.
Innovation Solution
A stemless semi-constrained implantable interphalangeal joint replacement device with a flexible connector secured by transverse fixation systems, using biocompatible materials and various fixation methods to maintain joint stability and allow natural motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If stemmed arthroplasty devices are used to provide joint replacement, then joint stability is improved, but bone loss and functional loss occur due to stem insertion requirements
Solution Approach 1:
The patent removes the stem component from the arthroplasty device, extracting the problematic element that caused bone loss while retaining the essential joint replacement function. The stemless design eliminates the need for medullary canal preparation and stem insertion, thereby preventing bone loss in the phalangeal bones while maintaining joint stability through alternative fixation methods using the condylar surfaces.
Solution Approach 2:
The arthroplasty device is segmented into separate condylar components that articulate with each other, allowing independent optimization of each component. The modular design includes a first condylar component with a first condyle and a second condylar component with a second condyle, enabling precise fitting to the patient's anatomy without requiring stem insertion for stability.
2Ease of operation
If constrained hinge joint replacement devices are used, then joint motion is controlled, but stiffness and unpredictable motion outcomes occur
Solution Approach 1:
The patent transitions from a static, fully constrained hinge design to a dynamic semi-constrained design that allows natural joint motion patterns. The condylar components articulate with each other to permit flexion, extension, and limited rotation, mimicking natural interphalangeal joint kinematics while maintaining stability through the condylar groove and ridge geometry.
Solution Approach 2:
The degree of constraint is changed from fully constrained to semi-constrained, altering the motion parameters of the joint replacement. This parameter change allows more natural range of motion and rotation while maintaining sufficient stability through the condylar articulation geometry, improving both motion control and predictability.
3Object-affected harmful factors
If fusion surgery is performed to eliminate pain, then pain relief is achieved, but permanent functional loss of movement occurs
Solution Approach 1:
Instead of fusing the joint to eliminate motion and pain (the conventional approach), the patent inverts the strategy by replacing the joint surfaces with mobile condylar components that maintain motion capability. This inversion allows pain relief through resurfacing while preserving functional mobility, avoiding the permanent functional loss associated with fusion.
4Device complexity
If one-piece axial hinge devices are used, then surgical procedure is simplified, but implant loosening and breakage occur at high stress areas
Solution Approach 1:
The one-piece hinge device is segmented into separate condylar components that articulate with each other. This segmentation distributes mechanical stresses across multiple articulating surfaces rather than concentrating them at a single high-stress junction, improving implant durability while maintaining surgical simplicity through the straightforward condylar resurfacing procedure.
Data Source
AI summary
A stemless semi-constrained implantable interphalangeal joint replacement device and methods for use thereof. The stemless implantable device comprises a flexible connector that spans the joint space between and flexes in the sagittal plane. The flexible connector is secured along its proximal edge by a fixation system implanted transversely in the coronal plane through the first phalange and along its distal edge by a fixation system implanted transversely through the second phalange in parallel relationship with the first fixation system. In certain embodiments, the flexible connector is attached to bone using a rod or an anchor. In certain embodiments, the anchor is a cannulated screw anchor comprising a hollow shaft and a slot, the slot being of sufficient width to allow both a first barrel shape at the proximal edge of the flexible connector and a second barrel shape at the distal edge of the flexible connector to pass through the slot and into a joint cavity whereby said flexible connector will be held fast within the hollow shaft of the anchor. In certain embodiments, the flexible connector is a polymer connector which comprises bumper flanges that are oriented in a perpendicular aspect to the coronal plane of the flexible connector to prevent bone-on-bone contact.