Hour-Glass Interlocking Nail Geometry for Bone Fracture Repair
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Solution Overview
Problem
Current interlocking nails with straight rod designs fail to provide adequate stability and resistance to bending and torsion, leading to delayed healing or non-union of bone fractures, and often require invasive surgical procedures and external fixators, which can cause infection and instability.
Innovation Solution
An hour-glass interlocking nail with a self-tapping, tapered locking design and a geometry that includes a proximal and distal section with larger diameters than the mid section, allowing for flexible insertion and reduced stress at the fracture site, minimizing invasive procedures and promoting better bone healing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a straight rod design with consistent cross section is used for interlocking nails, then the surgical implantation is simple, but the resistance to bending and torsion is inadequate, resulting in micromotion at the fracture site
Solution Approach 1:
The nail is divided into multiple sections (proximal section, mid section, distal section) with different cross-sectional characteristics. The proximal and distal sections have larger cross-sections for enhanced fixation and resistance, while the mid section has a smaller cross-section to accommodate the fracture geometry, creating a segmented structure that optimizes both strength and surgical ease
Solution Approach 2:
Different sections of the nail are given different local qualities: the proximal and distal sections have larger cross-sections with fixation holes for strong anchoring, while the mid section has a reduced cross-section to match the narrower bone canal at the fracture site. This local differentiation provides adequate resistance to bending and torsion where needed while maintaining ease of implantation
2Strength
If the proximal and distal portions of the nail have larger cross sections, then the resistance to bending and torsion is improved, but the stresses at these portions increase, challenging the fixation
Solution Approach 1:
The nail geometry is pre-designed with enlarged proximal and distal sections that naturally distribute stresses before the implant is even inserted. This preliminary geometric configuration ensures that when the nail is implanted, the stress distribution is already optimized, reducing peak stresses at the fixation portions while maintaining overall structural strength
Solution Approach 2:
The cross-sectional parameters of the nail are changed along its length, creating an hourglass shape where the proximal and distal sections have larger cross-sections for strength, and the mid section has a smaller cross-section. This parameter variation optimizes the stress distribution and resistance to bending and torsion without creating excessive stresses at any single location
3Object-affected harmful factors
If conventional interlocking nails are used, then the surgical procedure is less invasive than bone plates and screws, but the stability is inadequate, requiring external fixators and resulting in delayed union or non-union
Solution Approach 1:
The nail employs a composite geometric structure combining elements of different designs: the hourglass shape with enlarged ends provides the stability and resistance needed for reliable fixation, while the overall intramedullary nail design maintains the less invasive surgical approach. This composite approach integrates the advantages of both stable fixation and minimal invasiveness
Data Source
AI summary
An interlocking nail having an hour-glass geometry is used for repair of bone fractures. The hour-glass interlocking nail includes a proximal section, a mid section, and a distal section. Each section of the hour-glass interlocking nail has a diameter. The proximal and distal sections each have a diameter larger than the mid section so that the interlocking nail has an hour-glass geometry. The hour-glass interlocking nail comprises at least one fixation aperture located within either the proximal or distal section of the hour-glass interlocking nail. Preferably, the fixation aperture has a tapered locking design adapted to receive a screw-cone peg. The hour-glass geometry utilized by the interlocking nail is better suited to address a larger population of bone canal geometries, stressing the fracture site with known values within the healing process and preventing inadvertent perforation of the nail through the cortex of the bone. Hour-glass nail geometry more appropriately distributes stresses and promotes better healing at the bone fracture.