Angled Intramedullary Fixation Assembly for Foot Arch Restoration
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Solution Overview
Problem
Current orthopedic implant devices, such as intramedullary nails and plates, are inadequate for effectively fusing angled joints like the metatarsal and phalangeal bones in the foot, as they fail to deliver sufficient compression and often lead to complications like wound infections and skin irritation, limiting their ability to restore the arch in Charcot foot deformities.
Innovation Solution
An intramedullary fixation assembly with a proximal member and a distal member forming a fixed angle, allowing for an interference fit and compression of the joint, combined with a method involving incisions, reaming, and guide wire placement to restore the arch in the mid-foot region, utilizing materials like Titanium or other biocompatible metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple screws and plates are used to fuse metatarsal-phalangeal joints, then fixation is achieved, but wound complications and skin irritation increase due to surface prominence requiring greater tissue tension
Solution Approach 1:
The invention extracts the problematic surface-prominent components (plates and exposed screw heads) and replaces them with an intramedullary nail that sits entirely within the medullary canal. The fixation is achieved through internal interference fit and friction between the nail and medullary canal walls, eliminating the need for external hardware that causes skin irritation and wound complications.
Solution Approach 2:
The intramedullary nail is nested within the medullary canal of the metatarsal bone, with the nail's outer surface fitting inside the bone's internal canal. This nesting arrangement allows the fixation device to be contained within the bone structure rather than protruding externally, reducing soft tissue disruption and wound complications.
2Stability of the object's composition
If plates with fixed angles are used for MTP fusion, then bone alignment is maintained, but direct compression across the joint is insufficient
Solution Approach 1:
The invention changes the geometric parameters of the intramedullary nail, specifically incorporating a distal portion that is offset and angled relative to the proximal portion. This angular configuration allows the nail to deliver direct compression forces across the metatarsal-phalangeal joint while maintaining proper bone alignment, overcoming the limitation of fixed-angle plates.
Solution Approach 2:
The intramedullary nail features a curved or angled distal portion rather than a straight configuration. This curvature allows the nail to follow the natural anatomy of the medullary canal while delivering compression forces at the appropriate angle to the joint, improving both alignment and compressive force delivery.
3Reliability
If screws are inserted through plates for MTP fusion, then fixation is achieved, but screw head break out occurs due to insufficient compression
Solution Approach 1:
The invention removes the plate and screw construction entirely, replacing it with an intramedullary nail that achieves fixation through direct interference fit and friction within the medullary canal. This eliminates the screw heads that are prone to breaking out and provides more reliable compression without the need for additional fasteners.
4Ease of operation
If intramedullary nails with smooth surfaces are used for long bones, then insertion is facilitated, but they cannot secure small bones at obtuse angles like metatarsal-phalangeal joints
Solution Approach 1:
The intramedullary nail incorporates a curved distal portion with a specific angle relative to the proximal portion. This angular curvature allows the nail to be inserted through the medullary canal while delivering fixation at the appropriate obtuse angle for metatarsal-phalangeal joint fusion, combining ease of insertion with angular adaptability.
Solution Approach 2:
The nail has different geometric characteristics at different locations: the proximal portion has a smooth surface for easy insertion and navigation through the medullary canal, while the distal portion features an angled offset configuration for proper joint fixation. This local differentiation of properties allows the single device to achieve both ease of insertion and angular adaptability.
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 solution enables effective fusion of metatarsal-phalangeal joints, reduces wound complications, and restores the arch in the foot by minimizing tissue tension and incision length, improving surgical outcomes for Charcot foot and other deformities.
Implementation Method 1
The proximal member and the distal member form an interference fit and friction between the proximal member and the distal member provides compression
Data Source
Figure 1
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Figure 3A
AI summary
Disclosed is intramedullary fixation assembly for bone fusion. A first member is positioned at a proximal end of the intramedullary fixation assembly and comprises first and second terminal ends, a first aperture at the first terminal end, a longitudinal axis extending through the first aperture and the second terminal end, and a bore extending through the first aperture and a second aperture in a side of the first member. The longitudinal axis and the bore define an angle. A second member is positioned at a distal end of the intramedullary fixation assembly. The second member comprises a second shaft extending along a second longitudinal axis, a bulbous portion at a first end of the second member, and a second threaded portion at a second end of the second member. The bulbous portion is configured to abut the first aperture of the first member when the second member is inserted through the second aperture and the bore and out the first aperture of the first member. The second member is configured for coupling with the first member at the angle.