UT Health San Antonio

Jesse Rettele

Orthotics and prosthetics is a division of the allied health profession and consists of professionals who share a passion for biomechanics. In simple terms, orthotics is the practice of bracing what’s existing, and prosthetics is the practice of replacing what’s missing. Orthotists and prosthetists currently have to complete a master’s-level orthotic and prosthetic (O&P) program that incorporates a clinical residency to be eligible for board certification. Included in the didactic portion of O&P is gross anatomy, biomechanics and material science. Orthotists/ prosthetists specialize in observational pathologic gait, and through an understanding and application of material science and mechanics, they apply external structures to the human body to minimalize pathologic gait in an attempt to restore as much function and stability as possible. Dr. Jacquelin Perry’s gait analysis research has laid the foundation for orthotists/prosthetists like Charles Radcliffe to develop best practice guidelines in using orthotic and prosthetic devices that apply external forces and movements to influence biomechanics during gait. The goal is to maintain a center of mass (COM) within a small area in all planes during gait. There are 6 determinants of gait, as defined by Dr. Perry, that are applied when observing gait to determine any deficiencies requiring attention. Any deviations of this COM cause increased energy expenditure and imbalance, which could result in increased falls and reduced activity level.

Historically, orthotic devices provided structure or corrective forces for weak or malaligned joints/segments of the body, and prosthetic devices provided shock absorption and basic suspension/support to the residual limb as a foundation to attach prosthetic components. However, with advances in technology and material science, more options are available to further improve O&P services in the never-ending goal to reduce gait deviations and reach normal human locomotion. Dynamic materials such as carbon fiber, microprocessor-controlled joints and vacuum-assisted socket systems have significantly enhanced the ability to shrink the gap between pathologic gait and normal human locomotion. These materials/technologies are able to retain the shock absorption properties that have been available for many years. However, they are also able to provide specifically designed and controlled resistances/shock absorption and kinetic return features to further enhance performance during gait. For example, a custom-made carbon fiber Ankle Foot Orthosis (AFO) can be designed to control excessive motion about a joint (normally a total of 25 degrees range of motion during normal gait) by stabilizing the proximal and distal segments to allow normal motion under controlled resistance (defined as the loading response and closed-chain mechanics during the stance phase of gait). This deflection of forces is absorbed, stored and released by the carbon fiber to provide propulsion (during the pre-swing phase of gait). Additionally, when there is a weakness and inability to control the knee joint (either weak plantar flexors/knee extensors, or in the case of an above-knee amputation), a microprocessor-controlled joint can be used that incorporates a gyroscope and accelerometer to allow the knee to easily flex up to 60 degrees during the swing phase while also allowing controlled resistive knee flexion up to 20 degrees in the stance phase. The Vacuum Assisted Socket System has provided improved proprioception for the user to reduce falls, stabilized fluctuating residual limb volume, and reduced perspiration, which becomes excessive within a prosthetic socket. These technologies have been utilized within the past twenty years and are now being covered by insurance due to undeniable ability to reduce hospitalizations and help the users to maintain gainful employment.

"A 3D printer produces a quick, low-cost, rapid prototype that can then be tested, if needed, and redesigned"

An evolving technology that is being applied to O&P device design and fabrication is added manufacturing. This is commonly known as 3D printing and opens up many more possibilities when compared to traditional design and fabrication methods. Historically, the design of O&P devices has been driven by the limitations of the materials and fabrication methods for these devices. Vacuum encapsulation, a technique used in fabrication O&P devices by highly skilled technicians, has limited design control with inconsistent results due to many uncontrollable factors. However, 3D printing has the potential to change all of this with generative design and topology optimization software, as well as the rapidly evolving 3D printers and developing durable textiles used with 3D printing. For example, 3D printing of O&P devices allows certain areas of the device to be designed flexible and other areas to be designed rigid to allow for reducing pressure areas or increasing torsional resistance to forces and/or moments. A 3D printer produces a quick, low-cost, rapid prototype that can then be tested, if needed, and redesigned. A definitive device can then also be created from a 3D printer after being designed and tested to ensure optimal results. This creates a highly customizable device that is specifically engineered and designed to meet the requirements of the user.

While the best technology is not necessarily the best use of technology, orthotists/prosthetists are excited about the potential benefits that improved technology may offer when developing a plan of care for those who suffer with physical limitations and decreased mobility and independence. Added manufacturing (3D printing) specifically, promises low cost immediate access to large populations in need of O&P care that currently have limited access to much needed enabling devices.