Stemless Shoulder Implant Positioning in High-Density Bone
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Solution Overview
Problem
Current robotic systems for surgery lack precision and accuracy in preparing the shoulder joint for shoulder arthroplasty, particularly when using stemless implants, which require secure placement without a humeral stem for stability.
Innovation Solution
A robotic surgery system with a robotic manipulator and cutting tool, coupled with a localizer and controller, uses density data to determine the optimal location for material removal, ensuring the eccentric distal projection of the implant is placed in a region of higher bone density for improved fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If robotic systems are used for shoulder arthroplasty, then precision and accuracy in implant placement is improved, but the ability to adapt to varying bone density distributions is insufficient
Solution Approach 1:
The system determines bone density at specific locations within the humerus and uses this local density information to position the implant's eccentric distal projection in regions of higher bone density. This local adaptation ensures optimal fixation strength at the implant-bone interface while maintaining the precision of robotic placement.
Solution Approach 2:
The system performs preoperative planning that includes determining the bone density distribution throughout the humerus before surgery. This preliminary assessment allows the surgical plan to be customized to place the implant in regions of higher bone density, and the robotic system then executes this pre-determined optimal position with high precision.
2Loss of substance
If stemless implants are used, then bone preservation is improved, but implant stability is reduced
Solution Approach 1:
The system compensates for the lack of a stabilizing stem by concentrating the implant's fixation elements in regions of higher bone density. The eccentric distal projection is specifically positioned in dense bone regions to maximize fixation strength, allowing stemless implants to achieve adequate stability without requiring extensive bone removal for stem accommodation.
Solution Approach 2:
The system changes the placement parameters of the implant based on measured bone density characteristics. By adjusting the position and orientation of the eccentric distal projection to align with high-density bone regions, the system optimizes the mechanical interlocking between implant and bone, thereby enhancing stability despite the absence of a stem.
3Manufacturing precision
If material is removed from the bone to receive the implant, then implant fit is improved, but bone structural integrity is compromised
Solution Approach 1:
The system performs virtual planning that determines the optimal volume and location of bone material to be removed based on the target implant position and bone density distribution. This preliminary calculation ensures that material removal is minimized while still achieving proper implant fit, and that critical load-bearing bone structures are preserved.
Solution Approach 2:
The system identifies and preserves regions of high bone density that are critical for structural integrity while allowing material removal in regions where it is safe to do so. The implant is positioned to utilize high-density bone regions for fixation while minimizing removal from areas that would compromise overall bone strength.
Data Source
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AI summary
A robotic system includes a machining station and a guidance station. The guidance station tracks movement of various objects in the operating room, such as a surgical tool, a humerus of a patient, and a scapula of the patient. The guidance station tracks these objects for purposes of controlling movement of the surgical tool relative to virtual cutting boundaries or other virtual objects associated with the humerus and scapula to facilitate preparation of bone to receive a shoulder implant system. The virtual objects are located based on density data of the bone such that, when one or more shoulder implants are fully seated in the bone, distal portions of the implants are located in a first region of the bone having a density characteristic greater than an adjacent second region of the bone.