Overview
Millions of amputees require above-knee prostheses. Many non-government organizations like Ratna Nidhi Charitable Trust fabricate and supply them to marginalized patients. They needed to improve the fitment using patient-customized sockets, and yet reduce the overall lead time. The project was carried out at the Biomedical Engineering Technology Innovation Center, IIT Bombay and supported by Google. It also involved IIT Madras (for knee joint) and MGM Hospital (for gait study).
TEAM
Lalit Amrutsagar, Dr. Trimbak Kawdikar, Arvind Bhallamudi, Viren Dhumal, Dr. Rupesh Ghyar
MY ROLE: Mechcanical Engineering Intern
Caried out measurement design, generation of stump models using field data, comparison and validation of the developed parametric model, and supported in fabrication and assembly.
KEY SKILLS
Developing Lower-Limb Prostheses
BIOMEDICAL ENGINEERING & TECHNOLOGY INNOVATION CENTER, IIT BOMBAY | 2018
CHALLENGES
Discovering Needs & Process Gaps
India has a large number of trans-femoral (above-knee) amputees who need high-quality yet affordable prostheses to return to near-normal life. Current low-cost prostheses such as ‘Jaipur Leg’ use a plaster replica of the residual limb of patients to fabricate a matching socket. Stump replication is a cumbersome process that requires skilled technicians, challenges the dignity of patients and often requires rework.
RESEARCH
Understanding Conventional Prosthesis Design
Study on conventional prosthesis pointed to the need for a patient-customized above-knee prosthesis with better conformance and shorter fabrication time (compared to conventional Jaipur Leg).
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DESIGNS
Generating a Parametric Model from Stump Measurments
21 dimensions identified in discussions with clinicians and technicians, to semi-automatically generate a parametric stump model for patients. We also tried generating the stump model by 3D scanning but this method had limitations in accuracy as well as logistics. To facilitate proper measurements and their recording by field workers, an intuitive and bilingual chart was designed. These measurements will be used to parametrically generate a CAD model of the patient’s stump, which can be used to fabricate a socket.
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Using field data from measurement camps, we generated parametric CAD stumps of multiple patients, followed by fixing and modifying the form to improve conformity. To test the conformity, the parametric CAD stumps were compared to conventional plaster stumps by 3D scanning the plaster stumps using Steinbichler Comet L3D. The distance between cloud points of these two meshes was analysed using CloudCompare and were found to have an accuracy of 90% up to 8 mm in deviation.
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The parametric model of the patient stumps were exported for manufacturing using CNC machining. The stumps were then coated before fabricating corresponding sockets using conventional socket molding procedure, followed by the rest of the prosthesis.
Bilingual Measurement Sheet
Parametric Model Design
Manufacturing & Assembly
IMPACT
Outcomes in Cost, Convenience & Comformation
The gait of different prostheses was tested at Center for Human Movement Science, MGM Hospital, Mumbai. Patients in remote areas do not need to travel to cities since field workers can take their stump measurements and send them to the fabrication center. The prostheses can be fabricated and delivered to the patients.
