Patella Implant Planning Using Coordinate System
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Solution Overview
Problem
The irregular morphology of the patella makes it difficult to obtain accurate measurements for proper sizing and positioning of patellar implants during total knee arthroplasty, leading to potential maltracking, anterior knee pain, and implant instability.
Innovation Solution
A method to generate a patellar coordinate system using key bony landmarks, allowing for the identification of natural coordinates and ensuring proper alignment and sizing of the resection plane and implant placement, utilizing a graphical user interface to select landmarks and create coordinate planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calipers are used to measure patella thickness, then measurement can be obtained, but measurement precision is poor due to irregular morphology and lack of reference points
Solution Approach 1:
The patent introduces a coordinate system as an intermediary framework that maps the irregular patella surface to a standardized reference system. By defining origin points, axes, and measurement planes based on anatomical landmarks, the system enables precise thickness measurements without requiring complex specialized measurement devices. The coordinate system acts as a mediator between the irregular patella geometry and the simple caliper measurement tool.
Solution Approach 2:
The patent transitions from direct linear measurement to a multi-dimensional coordinate-based measurement approach. By establishing a three-dimensional coordinate system with origin, axes, and measurement planes, the system enables precise thickness measurement at specific locations and orientations. This dimensional transformation allows accurate measurement without requiring complex measurement devices, as the coordinate system provides the reference framework.
2Reliability
If implant thickness is increased to compensate for measurement uncertainty, then implant stability improves, but patellar kinematics are altered and flexion is limited
Solution Approach 1:
The patent performs preliminary planning to precisely determine the required implant thickness before surgery. By establishing the patella coordinate system and measuring actual thickness at specific locations (anterior-posterior, medial-lateral, proximal-distal dimensions), the system calculates the exact implant thickness needed. This preliminary precise measurement eliminates the need to over-compensate with thicker implants, thereby maintaining patellar flexion range while ensuring implant stability.
Solution Approach 2:
The patent changes the measurement parameters from a single overall thickness measurement to multiple localized thickness measurements at different positions and orientations. By measuring thickness in three dimensions (anterior-posterior, medial-lateral, proximal-distal) and using these parameters to calculate implant thickness, the system determines the precise implant specification needed, avoiding both under-sizing and over-sizing.
3Strength
If resection thickness is reduced to maintain patella strength, then patellar fracture risk decreases, but implant positioning accuracy is compromised
Solution Approach 1:
The patent segments the patella thickness measurement into three independent dimensions: anterior-posterior thickness, medial-lateral thickness, and proximal-distal thickness. By measuring and planning resection in each dimension separately using the coordinate system, the system can precisely control resection depth while maintaining structural strength. This segmentation allows accurate implant positioning without requiring excessive resection, as each dimensional parameter can be independently optimized.
4Measurement precision
If computer-assisted surgery is used to improve measurement accuracy, then implant sizing improves, but device complexity and procedural complexity increase
Solution Approach 1:
The patent introduces a patella coordinate system as a conceptual intermediary that simplifies the measurement and planning process. Rather than requiring complex computer-assisted surgery hardware and software, the coordinate system provides a standardized reference framework that can be used with simple calibration blocks and visual inspection. The coordinate system acts as a mediator between the irregular patella anatomy and the simple measurement tools, enabling accurate implant sizing without complex equipment.
Data Source
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AI summary
Disclosed herein are systems and methods of patella preparation. A method of patella preparation includes creating a patellar coordinate system utilizing key boney landmarks of a patella on a virtual model of an unresected patella. The method can further include defining a resection plane at a predetermined implant thickness and aligning the resection plane with the patellar coordinate system. Implant selection can be finalized on the resection plane to meet predetermined tolerances. A navigated patella clamp with a tracker and stylus can then be used to intraoperatively resect the patella and locate the implant.