Knee Instrument Mechanical Axis Alignment
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Solution Overview
Problem
Current knee arthroplasty instruments fail to accurately align the distal femur and proximal tibia as a single lower extremity body part, leading to inexact cuts and potential premature failure of the reconstructed knee, due to the violation of established biomechanical principles and the need for external rotation adjustments to balance compartment compression.
Innovation Solution
The use of a 'hinged' rod and cutting guides that align the femur and tibia along the mechanical axis, with the femoral and tibial cuts made in full extension, allowing for precise alignment and adjustment of the anterior and posterior femoral cuts relative to Whiteside's line, ensuring equal compartment compression and proper patellar tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional intramedullary instruments are used to determine distal femur alignment, then the instrumentation process is simpler to teach and utilize, but the alignment precision and reliability of the reconstructed knee deteriorates
Solution Approach 1:
The instrument divides the alignment process into distinct segments: an intramedullary component for establishing the mechanical axis and an extramedullary component for referencing the anterior distal femoral cortex and Whiteside's line. This segmentation allows each component to perform its specific function optimally while working together to achieve comprehensive alignment.
Solution Approach 2:
The patent combines intramedullary and extramedullary instrumentation into a single integrated system. The intramedullary rod establishes the mechanical axis, while the extramedullary guide aligns with the anterior distal femoral cortex and Whiteside's line, merging both approaches to achieve precise alignment of both femur and tibia as a single lower extremity body part.
2Ease of operation
If separate preparation of distal femur and proximal tibia is performed using traditional instruments, then the surgical procedure is easier to perform, but the conjoined alignment of the single lower extremity body part deteriorates
Solution Approach 1:
The alignment instrument serves multiple functions: it aligns the distal femur along the mechanical axis, references the anterior distal femoral cortex, establishes Whiteside's line, and guides proximal tibia alignment. This multi-functionality ensures conjoined alignment of both bones while maintaining ease of operation through a unified instrument design.
3Device complexity
If external rotation of the femoral component is not performed, then the surgical procedure is simpler, but patellar tracking and compartment compression balance deteriorate
Solution Approach 1:
The instrument establishes Whiteside's line and the mechanical axis before any bone cuts are made, preliminarily determining the correct external rotation angle. This preliminary alignment guidance ensures that the required external rotation is accurately achieved, improving patellar tracking and compartment compression balance while maintaining procedural simplicity.
Data Source
AI summary
Knee arthroplasty instrument systems directly reference and align with the anterior distal femoral cortex and the mechanical axis of the leg. The anterior femoral resection is aligned in the same plane as the anterior distal femoral cortex. The center of the femoral head, the medial/lateral center of the distal femur, the medial/lateral center of the proximal tibia, and the second toe, medial/lateral center of the ankle, or anterior tibial spine are all aligned to the mechanical axis of the leg. Methods of using the instrument systems are disclosed.