🤖Medical Robotics Unit 11 – Robotic Prosthetics and Orthotics

Key Concepts and Terminology

• Robotic prosthetics artificial limbs that integrate mechanical components, sensors, and computer control to replace missing body parts
• Orthotics external devices applied to the body to modify structural and functional characteristics of the neuromusculoskeletal system (braces, splints)
• Biomechatronics interdisciplinary field combining biology, mechanics, electronics, and computer science to develop assistive devices
• Degrees of freedom (DOF) number of independent parameters defining the configuration of a robotic system
  • Each joint in a robotic prosthetic contributes to the overall DOF
• Actuators components responsible for generating motion in robotic systems (motors, hydraulic cylinders, pneumatic muscles)
• Sensors devices that detect and measure physical quantities, enabling feedback control (force sensors, accelerometers, gyroscopes)
• Electromyography (EMG) technique for recording and analyzing electrical signals produced by skeletal muscles
  • EMG signals often used as control inputs for robotic prosthetics
• Osseointegration direct structural and functional connection between living bone and the surface of a load-bearing artificial implant

Historical Development

• Early prosthetics date back to ancient civilizations, featuring simple materials like wood and leather
• In the 16th century, Ambroise Paré introduced hinged prosthetic legs and arms with locking mechanisms
• The American Civil War and World Wars I and II drove advancements in prosthetic design and manufacturing
• The concept of powered prosthetics emerged in the 1940s with the introduction of pneumatic and hydraulic systems
• Microprocessor-controlled prosthetic knees developed in the 1990s, enabling more natural gait patterns
• The 21st century has seen rapid progress in robotic prosthetics, integrating advanced sensors, materials, and control systems
  • Examples include the DEKA Arm (Luke Arm) and Ossur Power Knee

Types of Robotic Prosthetics and Orthotics

• Upper limb prosthetics designed to replace functionality of the hand, wrist, elbow, or shoulder
  • Examples: bebionic hand, LUKE arm, Michelangelo hand
• Lower limb prosthetics replace functionality of the foot, ankle, knee, or hip
  • Examples: Ossur Power Knee, Empower Ankle, Genium X3 knee
• Exoskeletons wearable robotic devices that enhance or assist human movement and strength
  • Examples: ReWalk, Ekso Bionics, HAL (Hybrid Assistive Limb)
• Functional electrical stimulation (FES) systems use electrical currents to stimulate paralyzed or weakened muscles
  • Often combined with orthotic devices to assist in walking or grasping
• Neuroprosthetics devices that interface directly with the nervous system to restore sensory or motor function
  • Examples: brain-computer interfaces (BCIs), cochlear implants, retinal implants

Biomechanics and Control Systems

• Biomechanics study of mechanical principles and structures in living organisms
  • Crucial for designing prosthetics that mimic natural human movement
• Inverse kinematics determines joint angles required to achieve a desired end-effector position
• Forward kinematics calculates the end-effector position based on given joint angles
• Control systems regulate the behavior of robotic prosthetics to achieve desired movements and forces
  • Open-loop control systems operate without feedback, relying on predefined commands
  • Closed-loop control systems use sensor feedback to adjust the system's behavior in real-time
• Proportional-Integral-Derivative (PID) control commonly used in robotic prosthetics to minimize error between desired and actual output
• EMG pattern recognition analyzes muscle activation patterns to predict intended movements and control prosthetic devices

Materials and Manufacturing

• Robotic prosthetics require lightweight, durable, and biocompatible materials
• Metals like titanium and aluminum alloys offer high strength-to-weight ratios and corrosion resistance
• Carbon fiber composites provide excellent mechanical properties and low weight
• Polymers, such as polyurethane and silicone, used for cosmetic covers and interface components
• 3D printing (additive manufacturing) enables rapid prototyping and customization of prosthetic components
  • Fused Deposition Modeling (FDM) and Selective Laser Sintering (SLS) are common 3D printing techniques
• Computer-Aided Design (CAD) software used to create digital models of prosthetic components
• Computer-Aided Manufacturing (CAM) techniques, like CNC machining, employed for precise fabrication of components

Integration with Human Anatomy

• Prosthetic sockets form the interface between the residual limb and the prosthetic device
  • Sockets must provide a secure, comfortable fit and distribute forces evenly
• Liners made of soft, flexible materials (silicone, polyurethane) worn between the residual limb and the socket for comfort and protection
• Suspension systems help to maintain the connection between the prosthetic device and the residual limb
  • Examples: suction suspension, pin lock, lanyard
• Myoelectric control uses EMG signals from residual muscles to control prosthetic devices
  • Requires careful placement of electrodes on the skin surface
• Targeted muscle reinnervation (TMR) surgery reassigns nerves to different muscle groups, enabling more intuitive prosthetic control
• Osseointegration involves surgically anchoring the prosthetic device directly to the bone, eliminating the need for a socket
  • Provides improved comfort, stability, and sensory feedback

Challenges and Limitations

• Robotic prosthetics can be expensive, limiting accessibility for many individuals
• Battery life and power consumption remain challenges for fully implantable and portable devices
• Achieving natural, intuitive control of prosthetic devices is difficult due to the complexity of human movement
• Sensory feedback from prosthetic devices is limited compared to natural sensory input
  • Lack of proprioception (sense of body position) can affect balance and coordination
• Durability and reliability of robotic prosthetics must be improved for long-term use in daily activities
• Social stigma and psychological adjustment to using prosthetic devices can be significant barriers
• Regulatory approval processes for new technologies can be lengthy and complex, slowing down innovation

Future Trends and Innovations

• Advancements in neural interfaces aim to provide more intuitive, thought-controlled prosthetic devices
  • Examples: brain-computer interfaces, peripheral nerve interfaces
• Improved sensory feedback systems to restore touch, pressure, and temperature sensations
  • Techniques like direct nerve stimulation and electrocutaneous stimulation show promise
• Integration of artificial intelligence and machine learning algorithms for adaptive, personalized control of prosthetic devices
• Development of more energy-efficient, lightweight, and compact components (batteries, motors, sensors)
• Exploration of alternative power sources, such as fuel cells and energy harvesting technologies
• Increased use of additive manufacturing for customized, patient-specific prosthetic designs
• Focus on reducing costs and improving accessibility of robotic prosthetics through open-source initiatives and standardization
• Continued research on biomimetic materials and structures to more closely replicate human tissues and movements