Cantilevered Knee Joint Cutter for Tunnel Cutting
Solution Overview
Problem
Conventional methods for knee joint replacement arthroplasty using robots result in significant tissue damage and lengthy surgery times due to large cutter sizes and top-down milling techniques, leading to increased pain and prolonged recovery for patients.
Innovation Solution
A tunnel cutting technique using a cantilevered cutter with a minimal diameter and optimized length, introduced from both anterior and posterior sides of the knee joint, to minimize tissue damage and reduce incision size, while employing chatter blockers and a helix angle for efficient bone cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large diameter cutter is used for milling the knee joint bone, then the cutting speed and material removal efficiency are improved, but the incision size increases and surrounding tissue damage occurs
Solution Approach 1:
The cutting process is divided into two distinct phases: a preliminary cutting phase using a large diameter cutter to remove most bone material efficiently, and a finishing cutting phase using a small diameter cutter to precisely define the implant surface. This segmentation allows each cutter size to optimize for its specific function without compromising the other.
Solution Approach 2:
The harmful effect of large diameter cutters damaging surrounding tissue is extracted and isolated to only the preliminary cutting phase. The finishing phase uses a small diameter cutter that does not contact or damage surrounding tissues, thereby removing the harmful effect from the critical finishing operation.
2Manufacturing precision
If a top-down milling technique is used, then the bone can be milled systematically, but the surgery time becomes lengthy and patient recovery is prolonged
Solution Approach 1:
The bone cutting process is segmented into bulk material removal and surface definition operations. The preliminary cutting phase removes the majority of bone material quickly, while the finishing phase takes only a fraction of the time to precisely define the implant surface, significantly reducing total surgery time while maintaining precision.
Solution Approach 2:
The preliminary cutting phase rapidly removes the majority of bone material through efficient cutting paths, skipping the time-consuming step of removing all bone material before defining the final surface. This rushing through of bulk removal allows the precision finishing to be performed quickly on minimal remaining material.
3Length of moving object
If the cutter shaft is made longer to reach deep bone structures, then the cutting capability is improved, but the cutter becomes more prone to vibration and breakage
Solution Approach 1:
The cutter assembly is segmented into a long shaft portion that reaches deep bone structures and a short cutting head portion that performs the cutting. The long shaft is supported by a sleeve mechanism that reduces vibration, allowing the cutting head to be short and stable despite the deep reach requirement.
Solution Approach 2:
A sleeve mechanism acts as an intermediary between the long shaft and the cutting head. The sleeve provides vibration damping and mechanical support, mediating the connection between the long reach requirement and the stability requirement, thereby allowing a long shaft without compromising cutter reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for precise and efficient cutting of the knee joint with reduced tissue damage and shorter surgery times, enhancing patient recovery and surgical precision by minimizing the size of the cut surface and preventing vibrations that could harm surrounding tissues.
Implementation Method 1
a cutter which is rotated at a high speed to cut the bone
Implementation Method 2
chatter blockers and a helix angle for efficient bone cutting
Data Source
AI summary
A method and a system for cutting the knee joint using a robot. A cantilevered cutter is introduced into the knee joint from inside and outside of upper and lower bones of the knee joint to realize a tunnel cutting technique in which cutting is conducted such that tunnels are defined in bone and remnant bone is cleared. The cutter includes a shaft in which a substantial axial portion is fitted into a sleeve and a remaining axial portion serves as a cantilever extending out of the sleeve, and a head which is formed at a distal end of the shaft. A length of the cantilever and a diameter of the head are determined to have minimum sizes as long as the head can be introduced into bone in such a way as to define a tunnel and can be moved in the bone while cutting the bone.