Intramedullary Fixation Device for Hammertoe Correction
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Solution Overview
Problem
Current surgical methods for hammertoe correction, such as using K-wires, often result in non-unions, migration, and pin tract infections due to inadequate fixation and stability, particularly in the phalanges of the toes.
Innovation Solution
A surgical technique involving an intramedullary fixation device with a smaller diameter head (less than 2.5 mm) that anchors in subchondral bone, providing increased pull-out resistance and stability by spanning multiple joints, and a method for intraoperative trimming to accommodate varying intramedullary canal sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If K-wire fixation is used for hammertoe correction, then the procedure is simple and easy to perform, but fixation stability is insufficient leading to non-unions, migration, and pin tract infections
Solution Approach 1:
The fixation device is segmented into multiple functional zones: a first head portion for anchoring in subchondral bone, a body portion for intramedullary placement, and a second head portion for distal anchoring. This segmentation allows each portion to perform its specific function optimally, providing stable fixation while maintaining surgical simplicity
Solution Approach 2:
The fixation device transitions from conventional two-dimensional cortical bone fixation to three-dimensional intramedullary canal anchoring with subchondral bone engagement. By utilizing the intramedullary space and anchoring in the dense subchondral bone, the device achieves superior fixation stability while remaining easy to implant
2Strength
If a larger diameter fixation device is used to increase pull-out resistance, then fixation strength is improved, but the device cannot pass through narrower intramedullary canals
Solution Approach 1:
The fixation device features a tapered geometry with a smaller diameter body portion that passes through the intramedullary canal and a larger diameter first head portion that anchors in the dense subchondral bone. This local quality variation allows the device to navigate narrow canals while achieving superior pull-out resistance through strategic anchoring in the stronger subchondral bone
Solution Approach 2:
The device utilizes the parameter change in bone density from cancellous to subchondral bone to achieve fixation. By anchoring the first head portion in the denser subchondral bone, the device achieves high pull-out resistance without requiring a uniformly large diameter throughout its length, thus maintaining adaptability to various canal sizes
3Ease of operation
If fixation device anchors only in cancellous bone, then insertion is easier, but pull-out resistance is insufficient leading to migration
Solution Approach 1:
The surgical technique involves preliminary preparation of the intramedullary canal to receive the fixation device, followed by strategic positioning of the first head portion into the subchondral bone. This preliminary action ensures proper alignment and facilitates easy insertion while achieving the goal of strong anchoring in subchondral bone to prevent migration
Data Source
AI summary
Surgical methods and fixation devices for bone fixation and stabilization on a patient include exposing at least a portion of a first phalanx and a second phalanx at a joint of a patient; creating a passage in an intramedullary canal of the first phalanx; inserting a first head portion of a fixation device along the passage in the intramedullary canal in a translating manner past the cancellous bone in the phalanx until the head portion engages the subchondral bone at a base of the first phalanx, the fixation device having an opposing second head portion extending out of the passage from the first phalanx; and introducing the second phalanx onto the second head portion so that the second head portion anchors in the second phalanx.