Patient-Specific Bone Milling Paths for Efficient Resection
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Solution Overview
Problem
Conventional milling path generation techniques for surgical systems are inefficient, leading to increased path length and milling time, and often result in suboptimal bone removal, air-cutting, and collision risks due to lack of patient-specific constraints and flexibility for intra-operative modifications.
Innovation Solution
A computer-implemented method for generating a milling path that involves obtaining a virtual model of the bone, defining a resection volume and a reference guide, producing section planes along the reference guide, generating section paths within each plane, and connecting these paths with transition segments to create a milling path that is constrained to the hard tissue and optimized for efficient bone removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional implant-specific worst-case milling paths are used, then the resection volume is sufficient for all possible implant placements, but the path length and milling time are increased
Solution Approach 1:
The system dynamically generates milling paths based on the actual implant placement position rather than using static pre-computed worst-case paths. The path is adapted in real-time to match the specific resection volume required for the implanted device, eliminating unnecessary milling operations while ensuring sufficient bone removal for the actual implant configuration.
Solution Approach 2:
The milling path parameters are changed from fixed worst-case values to variable parameters that depend on the actual implant placement. The system computes the resection volume based on the specific implant geometry and position, then generates a milling path that precisely matches these parameters, reducing the path length while maintaining adequate resection.
2Reliability
If conventional implant-specific worst-case milling paths are used, then the resection volume accommodates all implant placements, but more material is removed than needed
Solution Approach 1:
The system dynamically adjusts the resection volume and milling path to match the actual implant placement rather than removing material for all possible placements. The resection volume is computed specifically for the implanted device's geometry and position, ensuring that only the necessary bone material is removed while maintaining sufficient space for the actual implant.
Solution Approach 2:
The resection volume parameters are changed from fixed worst-case values to variable parameters based on the actual implant characteristics. The system computes the precise resection volume required for the specific implant device and placement position, then generates a milling path that removes exactly this volume, minimizing unnecessary bone material removal.
3Ease of manufacture
If conventional pre-operative milling paths are generated, then the path is determined before implant placement, but flexibility for intra-operative adjustments is lost
Solution Approach 1:
The system enables dynamic path generation that can be performed intra-operatively after the implant placement position is determined. Rather than being locked into a pre-operative plan, the milling path is computed in real-time based on the actual implant position and orientation, providing flexibility to adjust the resection volume and path to match the final implant configuration.
Solution Approach 2:
The system performs preliminary computation of the resection volume and milling path based on the actual implant placement position that is determined during the surgical procedure. This allows the path to be optimized for the specific case at hand while still being prepared in advance of the actual milling operation, combining the benefits of both pre-planning and intra-operative adaptation.
4Device complexity
If conventional linear entry segments are used, then the milling path is simple to generate, but plunge cuts into the anatomy occur due to abrupt entry
Solution Approach 1:
The system replaces linear entry segments with curved transition segments that smoothly guide the milling tool into the bone. The curved paths eliminate abrupt entry angles that cause plunge cuts, providing gradual tool engagement with the bone surface. This increases path generation complexity slightly but eliminates the harmful plunge cut effect.
Data Source
AI summary
Surgical systems, computer-implemented methods, and software programs for generating a milling path for a bone. The implementations involve obtaining a virtual model of the bone, a resection volume defined relative to the virtual model of the bone, and a reference guide defined with respect to the resection volume. Section planes are successively arranged along the reference guide, and each section plane intersects the reference guide and intersects the resection volume. A section path is generated within each section plane and is defined relative to the resection volume. Transition segments are generated to connect section paths of section planes. The milling path is then generated by combining the section paths and the transition segments.