Unicondylar Knee Cutting Guide Using Resected Bone Datum
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Solution Overview
Problem
Conventional unicondylar knee replacement procedures face challenges in accurately positioning tibial and femoral cuts due to reliance on anatomical features that may be worn or impaired, leading to inconsistencies in cut placement and implant fit.
Innovation Solution
The development of specialized surgical instruments, including a unicondylar posterior femoral cutting guide and tibial reference guide, with adjustable mechanisms and pin fixation, allows for precise cuts by using the resected posterior femoral condyle as a reference datum, enabling better alignment and adjustment of tibial and femoral cutting blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional cutting guides are used that rely on native anatomical features as datums, then the procedure is simpler to perform, but the positioning accuracy of cuts deteriorates when anatomical features are worn or impaired
Solution Approach 1:
The patent introduces an intermediary reference system consisting of a reference pin inserted into the resected posterior femoral condyle and a reference guide that receives the pin. This intermediary reference datum transfers the accuracy from the resected bone surface to the cutting block positioning, eliminating direct reliance on worn anatomical features while maintaining procedural simplicity
Solution Approach 2:
The procedure performs the posterior femoral condyle resection before establishing the cutting guides. This preliminary action creates a fresh, reliable bone surface that serves as the foundation for the reference pin and subsequent cutting guides, ensuring accurate cut placement without relying on degraded anatomical landmarks
2Stability of the object's composition
If cutting blocks are fixed rigidly to the bone, then positioning is more stable, but adaptability to different anatomical variations is reduced
Solution Approach 1:
The cutting guide employs a dynamic positioning system where the cutting block can be adjusted relative to the reference guide along a guide rail. This allows the cutting block to be positioned at different locations while maintaining stable reference to the bone, accommodating anatomical variations without sacrificing stability
Solution Approach 2:
The cutting guide is divided into separate components: a reference guide that attaches to the bone, a guide rail that provides the cutting path, and a cutting block that can be positioned along the rail. This segmentation allows each component to be optimized independently - the reference guide provides stable attachment while the cutting block maintains adaptability through adjustable positioning
Data Source
AI summary
Instrumentation and a method for unicompartmental knee replacement procedure are described. The surgical instrumentation may include a unicondylar posterior femoral cutting guide, a unicondylar tibial cutting block assembly and a unicondylar femoral cutting guide. The method may include inserting the unicondylar posterior femoral cutting guide into a joint gap while the knee is in flexion, resecting the posterior femoral condyle of the femur while the knee is in flexion, the surface of the resected posterior femoral condyle defining a reference plane, and setting the position of a unicondylar tibial cutting block on the tibia relative to the reference plane by using the resected surface of the posterior femoral condyle. The unicondylar femoral cutting guide may then be used to make one or more femoral cuts.