Conical Intramedullary Nail Screw Interlock for Bone Fixation
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Solution Overview
Problem
Current intramedullary nail and screw combinations for stabilizing fractured bones are invasive, provide insufficient support against torsional and bending forces, and expose patients to radiation during surgery due to the difficulty in accurately placing screws within the medullary canal.
Innovation Solution
An intramedullary nail with conical holes and screws featuring a conical central section with threads that interlock with the nail's holes, providing enhanced stability and resistance to separation under torsional or bending forces, and a method for inserting screws without radiological guidance by using conical holes that guide drill placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional transverse screws or pins are used to lock the intramedullary nail, then the nail can be secured in the bone, but the construct provides insufficient resistance to torsional and bending forces
Solution Approach 1:
The patent employs conical geometry in the screw-nail interface, where the conical screw threads engage with conical recesses in the nail. This curved, tapered geometry provides mechanical advantage by converting axial loading into radial clamping forces, significantly enhancing resistance to torsional and bending moments while maintaining reliable bone fixation.
2Manufacturing precision
If radiological guidance is used to accurately place screws through cortical tissue and into the nail, then screw placement precision is improved, but patient and surgeon exposure to x-ray radiation increases
Solution Approach 1:
The conical screw and nail geometry provides self-aligning and self-guiding properties. The conical shape naturally guides the screw into the correct orientation and position as it is inserted, eliminating the need for radiological guidance while maintaining high placement accuracy. This self-service mechanism reduces radiation exposure for both patient and surgeon.
3Ease of operation
If the surgical procedure is made less invasive by using intramedullary nails instead of external plates, then surgical trauma is reduced, but the level of support against torsional and bending forces decreases
Solution Approach 1:
The conical geometry of the screw-nail interface creates mechanical advantage that compensates for the minimally invasive approach. The tapered design generates radial clamping forces that significantly enhance the construct's resistance to torsional and bending loads, allowing the procedure to remain minimally invasive while achieving strength comparable to or exceeding traditional plate fixation.
Data Source
AI summary
The present invention demonstrates and improved interlocking nail and screw combination to repair fracture bones. The preferred combination uses an hourglass shaped intramedullary nail wherein the larger ends of the nail have holes capable of receiving screws. The holes may, or may not be conical. Further, the holes may or may not be threaded. The surgical screws have a variety of thread patterns, or lack threads. A non-threaded end is believed to improve healing because of a larger core diameter as compared to a comparably sized threaded screw end.