Intramedullary Nail With Variable Pitch Threads For Bone Compression
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Solution Overview
Problem
Conventional compression screws exert uniform compression along the bone shaft, lacking specific engineering for enhanced fixation and load distribution in intramedullary nail and screw combinations, particularly in tibiotalo and talo-calcaneal fusion procedures.
Innovation Solution
A cannulated screw/nail implant with synchronized end, middle, and head threads of varying diameters and pitches, allowing for selective compression and distraction capabilities, featuring a sharpened tip for drilling, biocompatible materials, and strategically placed holes for rotational stability and load distribution, along with a three-piece structure for adjustable compression and distraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional compression screws are used, then compression is applied along the bone shaft, but the compression is uniform and lacks specific engineering for enhanced fixation and load distribution
Solution Approach 1:
The screw features multiple thread sections with different pitches: a first middle thread section with a first pitch, a second middle thread section with a second pitch different from the first, and a head thread section with a third pitch. This allows different regions of the screw to provide different mechanical characteristics - finer pitch sections for compression in specific zones, coarser pitch sections for load distribution in other zones, enabling localized optimization of fixation strength and load distribution.
Solution Approach 2:
The screw is divided into multiple functional segments along its length, each with distinct thread characteristics. The end section has a sharpened tip for drilling, followed by first middle threads, second middle threads, and head threads, each with varying pitch and diameter. This segmentation allows each section to perform a specific function: drilling, compression, load distribution, and anchoring, thereby enhancing overall fixation capability.
2Adaptability or versatility
If a single-thread screw is used, then the structure is simple, but it cannot provide selective compression and distraction capabilities
Solution Approach 1:
Different thread sections are designed with specific pitch characteristics to provide selective compression or distraction in different zones. The first middle thread section with its specific pitch can be optimized for compression in one region, while the second middle thread section with a different pitch optimizes for distraction or compression in another region, allowing selective mechanical action without requiring multiple separate implants.
3Ease of manufacture
If the end diameter is similar to the middle diameter, then manufacturing is simpler, but the sharpened tip cannot effectively drill and tap as it advances
Solution Approach 1:
The screw features an asymmetric diameter profile along its length: the end diameter is smaller than the middle diameter, creating a tapered geometry. The sharpened tip at the smallest diameter section is designed to cut and tap bone as the screw advances, while the larger middle diameter provides structural strength and thread engagement. This asymmetric design balances the competing requirements of drilling capability and structural integrity.
Data Source
AI summary
The present bone implant is a cannulated screw/nail or combination having end, middle and head threads as well as unthreaded portions along the length of the shaft. The pitch of the head threads is always less than the middle threads. Variations include a two-part construction with a narrow protrusion having narrow-protrusion threads of opposite hand, or the inclusion of at least first middle threads and second middle threads of different pitch. The implant provides bone compression engineering heretofore unavailable with prior known compression screws.