Femoral Positioning Template for Rotational Knee Implant Alignment
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Solution Overview
Problem
Existing methods for aligning the femoral component in prosthetic knee surgery do not adequately consider the rotatory component of the femur, leading to potential ligament tension imbalances and patient discomfort due to misalignment.
Innovation Solution
A device comprising an anatomical template with a concave upper portion and lateral fins, which is attached to the distal femur and aligned using a stem inserted into the medullary canal, ensuring correct positioning of the femoral component by reproducing the patellofemoral joint and using fixing elements for secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical alignment method is used to restore neutral alignment of the knee, then the mechanical axis is aligned from the femoral head through the knee center to the ankle center, but the rotatory component of the femur is not considered leading to ligament tension imbalances and patient discomfort
Solution Approach 1:
The patent introduces an anatomical template as an intermediary device that bridges the gap between mechanical alignment and rotational alignment. The template serves as a mediator that transfers the correct rotational orientation from anatomical landmarks (trochlear groove, condyles) to the femoral component positioning, ensuring both mechanical and rotational alignment are achieved simultaneously
Solution Approach 2:
The alignment process is segmented into distinct functional components: the template body that contacts anatomical landmarks, the stem that extends into the medullary canal for rotational control, and the positioning features that guide the femoral component. This segmentation allows each part to perform its specific function in achieving comprehensive alignment
2Reliability
If alternative alignment methods (kinematic, restricted, reverse, functional) are used, then ligament tension may be better preserved, but the rotatory component of the femur is still left to surgeon intuition without systematic guidance
Solution Approach 1:
The template is designed to self-align through its anatomical contact surfaces that automatically position themselves on the trochlear groove and condyles. The stem self-adjusts within the medullary canal to achieve correct rotational orientation, eliminating the need for complex surgeon maneuvers or subjective judgment calls during positioning
Solution Approach 2:
The template performs preliminary alignment work by establishing the correct rotational orientation before the actual femoral component implantation. The anatomical landmarks are pre-prepared and the template is pre-configured with the correct geometry, so that when applied, it automatically establishes the proper alignment without requiring the surgeon to perform complex rotational adjustments
3Measurement precision
If a complex alignment device is designed to address all alignment parameters including rotatory component, then positioning precision may improve, but device complexity and cost increase
Solution Approach 1:
The patent merges multiple alignment functions into a single integrated template structure. The template combines anatomical contact surfaces for transverse plane alignment, longitudinal axis definition through the stem, and rotational control features, all in one device that simplifies the overall alignment process while maintaining comprehensive positioning precision
Solution Approach 2:
The template is designed as a precise copy or replica of the ideal anatomical relationships and alignment geometry. By copying the correct spatial relationships between the trochlear groove, condyles, and mechanical axis into the template structure, the device transfers this ideal geometry to the patient's anatomy, achieving accurate positioning without requiring the device itself to be overly complex
Data Source
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AI summary
A device (1) for identifying the correct positioning of the femoral component in prosthetic knee surgery, the peculiarity of which consists in that it comprises an anatomical template (2) adapted to be applied after distal resection of the femur, said template (2) having a concave upper portion (3) and two lateral portions (9, 10) separated by a cavity (4), each one of said lateral portions being provided with at least one hole (7, 8), a stem (5) being insertable in said cavity (4) and fixable therein by way of a fixing element (6) which can slide along said cavity (4).