Expandable Evans Wedge Implant for Flatfoot Correction
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Solution Overview
Problem
Current orthopedic implants for correcting flatfoot deformity require multiple trials for optimal wedge thickness, leading to potential bone damage and increased risk of post-operative complications due to distraction and revision surgeries.
Innovation Solution
An expandable orthopedic implant capable of continuous expansion within a specific thickness range, allowing surgeons to dial in the desired wedge thickness for correcting bone deformities, such as flatfoot, without the need for pre-trialing and minimizing bone damage during insertion.
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 risk of implant subsidence increase
Solution Approach 1:
The implant transitions from a static trial wedge requiring multiple insertions to a dynamic expandable implant that can be adjusted in situ. The expandable structure allows the surgeon to insert a minimal wedge and then expand it to the optimal thickness, eliminating repeated trial insertions and their associated cortical damage risks.
Solution Approach 2:
The optimal wedge thickness is determined through pre-operative planning and imaging, allowing the surgeon to select the appropriate expansion target before surgery. This preliminary determination eliminates the need for intraoperative trial-and-error testing, thereby preventing cortical wall deformation from multiple insertions and removals.
2Manufacturing precision
If distraction is performed to accommodate thicker wedge, then the desired correction can be achieved, but bone fragments on anterior or posterior calcaneus may be damaged or broken off
Solution Approach 1:
The wedge is expanded dynamically within the osteotomy site after insertion, rather than requiring pre-distracted bone fragments. This controlled expansion occurs after the osteotomy is created but before final fixation, allowing the bone edges to be gently separated without acute forcing that could cause fragment breakage.
Solution Approach 2:
The osteotomy is created with sufficient initial gap to accommodate the full expansion range of the implant. This preliminary preparation ensures that when the wedge is expanded to the desired thickness, the bone fragments are already positioned to accommodate the correction without requiring additional forced distraction that could damage fragments.
3Manufacturing precision
If revision surgery is performed to insert thicker wedge due to bony resorption, then lost correction can be recovered, but wound healing complications risk increases
Solution Approach 1:
The expandable implant allows for post-operative adjustment of wedge thickness through minimally invasive access. If bony resorption occurs and correction is lost, the surgeon can access the implant through a small incision and expand it further without requiring full revision surgery with large incisions, thereby minimizing wound healing complications.
Solution Approach 2:
The implant design allows for recovery of lost correction through minimal access expansion rather than complete removal and reinsertion. The same implant structure is retained and simply adjusted to a greater thickness, avoiding the need for extensive revision surgery and its associated wound healing risks.
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.