Expandable Evans Wedge Implant for Flatfoot Correction
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Solution Overview
Problem
Current orthopedic implants for correcting pes planus or flatfoot deformity require multiple trials for optimal wedge thickness, leading to potential bone damage, increased procedure time, and complications from post-operative bony resorption, necessitating revision surgery.
Innovation Solution
An expandable orthopedic implant capable of continuous expansion with automatic locking at desired thickness, allowing surgeons to dial in the wedge thickness to correct bone deformities without the need for pre-trialing or independent distraction, minimizing bone damage and preserving the osteotomy site.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple trial wedges are inserted and removed to determine optimal thickness, then the optimal wedge thickness can be determined, but cortical wall deformation and implant subsidence risk increase
Solution Approach 1:
The implant transitions from static trial wedges to a dynamic expandable system. The implant is inserted in a collapsed state and then expanded in-situ to the required thickness, eliminating the need for multiple trial insertions and removals that cause cortical damage.
Solution Approach 2:
The implant uses a nested structure where the endplate is contained within the main body in a collapsed state for easy insertion, then expands outward to the required thickness. This nesting allows the implant to be inserted through a small incision and then expanded to the optimal size without requiring multiple trial insertions.
2Manufacturing precision
If distraction is performed to insert a thicker wedge, then the desired correction can be achieved, but bone fragments surrounding the wedge are damaged or broken off
Solution Approach 1:
The implant is inserted in a collapsed state and then dynamically expanded to the required thickness. This eliminates the need for pre-distraction of the osteotomy site, thereby preventing damage to the bone fragments that would otherwise occur during the distraction process.
Solution Approach 2:
The implant is prepared in a collapsed state before insertion, allowing it to be inserted into the osteotomy site without requiring prior distraction. The expansion to the required thickness occurs after insertion, preventing damage to the bone fragments during the correction process.
3Reliability
If a thicker wedge is used to correct the deformity, then the correction effectiveness is improved, but the risk of post-operative bony resorption and revision surgery increases
Solution Approach 1:
The expandable implant allows for precise adjustment of the wedge thickness in-situ, enabling the surgeon to achieve the optimal correction without using an excessively thick wedge. This precision reduces the risk of post-operative bony resorption and the need for revision surgery.
Solution Approach 2:
The system replaces the mechanical trial-and-error process with a controlled expansion mechanism. The implant is inserted in a collapsed state and then expanded to the precise required thickness using an actuator assembly, eliminating the need for multiple trial insertions and reducing the risk of over-correction and subsequent bony resorption.
4Measurement precision
If multiple trial insertions are performed, then the optimal wedge size is determined, but procedure time is prolonged
Solution Approach 1:
The expandable implant eliminates the need for multiple static trial insertions by allowing the wedge thickness to be adjusted dynamically in-situ. The implant is inserted once in a collapsed state and then expanded to the required thickness, significantly reducing surgical procedure time.
Solution Approach 2:
The single expandable implant performs multiple functions: it serves as both the trial device and the final implant. The actuator assembly allows the implant to be adjusted to the optimal thickness after insertion, eliminating the need for separate trial and final implantation steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The expandable implant effectively corrects bone deformities by allowing precise adjustment of wedge thickness, reducing the risk of bone damage and revision complications, while providing a stable fusion site for bone growth, thus improving surgical efficiency and patient outcomes.
Implementation Method 1
the endplate defining a pair of ramps, an actuator assembly including an actuator and two actuator pivots, each actuator pivot having a ring received on the actuator and a foot with a sliding surface configured to mate with the respective ramps on the endplate
Implementation Method 2
a drive assembly configured to move the actuator assembly, wherein movement of the drive assembly translates the actuator assembly to expand the endplate away from the main body
Data Source
AI summary
Expandable wedge implants and methods. The expandable implant has a main body, a moveable endplate pivotably connected to the main body, an actuator assembly including an actuator and two actuator pivots, and a drive assembly including a drive screw configured to move the actuator assembly to thereby expand the endplate relative to the main body. The expandable implant may be configured to correct pes planus or a flatfoot deformity using an Evans procedure during foot surgery.