Expandable Hip Stem With Screw-Driven Contraction Mechanism
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Solution Overview
Problem
Conventional artificial hip joint stems require strong impact for insertion and fixation, which can damage weak femur bones, and are difficult to remove due to bone growth and ossification, leading to challenges in reoperation and implant stability.
Innovation Solution
An artificial hip joint stem with a separable, contractible, and expandable structure featuring a screw-driven motion converter, adjustable variable operation portion, and curved guide hole and pin for minimizing insertion impact and facilitating easy removal, allowing for secure fixation and reoperation without damaging the femur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the stem is inserted in a press-fitting manner to increase adhesion to the femur, then fixation strength is improved, but impact damage to the femur worsens
Solution Approach 1:
The stem is designed with an expandable structure that transitions from a contracted state during insertion to an expanded state for fixation. The outer diameter of the stem can be dynamically adjusted: smaller during insertion to reduce impact, and larger after insertion to increase adhesion and fixation strength through expansion against the femoral cortex.
2Strength
If the hole in femur is formed smaller than stem diameter for press-fitting, then fixation power is improved, but manufacturing precision requirements worsen
Solution Approach 1:
The stem's outer diameter parameter is changed dynamically through expansion after insertion. Instead of requiring precise control of the initial hole diameter, the stem is inserted in a contracted state and then expanded to achieve the desired fixation pressure, making the process more tolerant of variations in hole size.
3Strength
If the stem is fixed to femur by press-fitting, then initial fixation is improved, but ease of removal worsens
Solution Approach 1:
The stem employs a reversible dynamic structure that can transition between expanded and contracted states. For removal, the stem is contracted back to its smaller diameter, reducing the adhesion force and allowing easy extraction from the femur, while still providing strong fixation during the operational expanded state.
Data Source
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AI summary
The present invention relates to an artificial hip joint stem and a stem providing method, and the artificial hip joint stem, which is used to replace the damaged femoral head or acetabulum, comprises: a stem body having a head fixing part, which protrudes from the upper part thereof and fixes a head, an operating space horizontally opened at the upper side thereof, and a head insertion hole vertically penetrated so as to be connected to the operating space; a screw part inserted into the head insertion hole and rotating; an operation converting part inserted into the operating space so as to vertically move by the screw part in a state in which the operation converting part is connected to the screw part; a fixing bracket inserted into the operating space such that the screw part is fixed so as to rotate without changing the depth thereof; a variable operating part inserted into a supporting surface of the stem body so as to adjust a horizontal width by means of operation of the operation converting part; and a movable pin for fixing the variable operating part to the operation converting part.