Prosthetics, Orthotics and Pedorthics R&D Experience and Teamwork in Action*

By Dr. Vern Houston

Editor’s introduction: The author, Vern Houston, worked hard to produce this article despite a heavy workload and imminent deadlines. When asked to provide additional details for the by-line, he wrote the following, which was considered worthy of reproduction in its entirety. I think it is a typical example of collaborative teamwork and humor combining with a rich wealth of experience - a celebrated tradition in movement analysis studies. GB

Vern writes: “My job titles are: Associate Professor, Department of Rehabilitation Medicine, NYU School of Medicine; and Senior Research Scientist, Rehabilitation Engineering Research, Department of Veterans Affairs New York Harbor HealthCare System. I have a bachelor’s degree in Mechanical Engineering, a doctoral degree in Electrical Engineering, and am ABC Board Certified in Prosthetics and Orthotics, as well as Licensed in P&O in the State of New Jersey. I have worked in clinical care and research and development in Prosthetics, Orthotics, and Pedorthics for 32 years. Our colleague, and recently retired Co-Director of the RERL, Mr. Carl P. Mason, MSBE, worked in the RERL for the Department of Veterans Affairs for 42 years. He was responsible for developing much of the instrumentation and conducting many of the locomotion studies performed in the first gait laboratory established by the Department of Veterans Affairs in the United States, as well as for developing the VAPC myoelectric externally powered hand, elbow, and hook, and the multi-axis SCI manipulator. Our Podiatric Medicine consultant, Martin Mussman, DPM, worked in the VA for 46 years. He started and directed the Podiatric Medicine Service in the Department of Veterans Affairs for over 32 years. Our research therapist, Ms. MaryAnne Garbarini, MA, PT, is a licensed physical therapist with a master’s degree in movement disorders. She has worked in Prosthetics, Orthotics, and Pedorthics research for 21 years. Our mechanical engineer, material scientist, computer numerical analyst, Gangming Luo, PhD, is an Assistant Professor in Rehabilitation Medicine at the NYU School of Medicine; and a Research Scientist at the VA NYHHS. He is an internationally recognized expert in soft tissue mechanical modeling and testing, finite element and boundary value analysis, and in computational modeling of prosthesis osseous integration and remodeling. Dr. Luo has worked at the NYUSM and the VA NYHHS in Prosthetics, Orthotics, and Pedorthics research and development for 11 years. Mr. Aaron C. Beattie, BS, is our program analyst, numerical control system integrator and instrumentation specialist. Mr. Beattie has worked in Biomedical and Rehabilitation Engineering research for 21 years. Mr. Chaiya Thongpop, our research assistant and laboratory technician, has been working in Biomedical and Rehabilitation Engineering research for 20 years. *Looking at all of the time we have collectively put in, perhaps the article should be entitled: “VA NYHHS / NYUSM Rehabilitation Engineering Research Laboratory - Old Researcher Folks Home.” Or “RERL Researchers Serve Life Terms”.

Figure 1a. Patellar-tendon bearing prosthetic socket for a transtibial amputee lined with two 1360 element Tekscan PScan FVR transducers to measure interface stresses during stance and gait.	Figure 1b. Resultant interface pressure distribution at midstance in a typical gait cycle for a transtibial amputee in a PTB socket measured with Tekscan PScan transducers.

The Rehabilitation Engineering Research Laboratory (RERL), at the Department of Veterans Affairs New York Harbor HealthCare System (VA NYHHS) and the New York University School of Medicine, Department of Rehabilitation Medicine (NYUSM), is a modern research laboratory established especially for research, development, and testing of Prosthetics, Orthotics, Pedorthics, and Rehabilitation Engineering procedures, systems, devices, and equipment. Historically, the RERL has its roots in the first Prosthetics, Orthotics, Pedorthics, and Biomechanics laboratory founded by the Veterans Administration in 1947 to conduct research and development to improve the rehabilitative treatment and care of US Veterans returning from World War II.

The RERL has offices, a computer laboratory, an electronics laboratory, a machine laboratory, patient fitting and evaluation rooms, a scanning laboratory, and a motion analysis laboratory. RERL instrumentation includes a Vicon eight 1000Hz M2-camera Model 612 Data Station Motion Analysis System with BodyBuilder and Polygon software, VA-Cyberware Lower Limb, Body, and Pedorthics Optical Digitizers, the VA Servo-controlled tissue indenters and integument tester, the VA NYHHS Prosthetics-Orthotics-Pedorthics CAD/CAM Systems, Tekscan PScan, FScan, and IScan stress measurement systems, the CIR Systems GaitRite Electronic Walkway, Kistler Force Platforms, Cosmed K4b2 Respiratory Gas and Metabolic Energy Measurement System, Quark ECG System, and a full complement of electronic and mechanical instrumentation and equipment for design, fabrication, and testing of Prosthetics, Orthotics, and Pedorthics devices, systems, and procedures.

Figure 1c. Measurement of a transtibial amputee’s residual limb morphology using magnetic resonance imaging (MRI).	Figure 1d. Mid-sagittal plane and MTP-2.5 cm transverse MRI cross sections of the transtibial amputee in Figure 1c.
Figure 1e. The transtibial amputee in Figure 1c with photoreflective markers, PScan and FScan transducers, in a comparative gait trial with a TSB prosthetic socket to measure his body and limb segment kinematics.	Figure 1f. Trajectories of the transtibial amputee’s body segments and prosthetic limb in a comparative gait trial with a TSB prosthetic socket measured with the Vicon Motion Analysis System.
	Figure 1g. The resultant center of mass (CoM) trajectory over a typical gait cycle for the transtibial amputee in Figure 1e.

RERL staff are involved in a number of collaborative research projects with researchers at the VA NYHHS, the NYUSM, the NYU Hospital for Joint Diseases, the City University of New York City College Department of Biomedical Engineering, and the State University of New York Downstate Medical Center, in which the Vicon motion analysis system is an essential quantitative measurement and assessment instrument. The “portability” of the Vicon system has enabled RERL researchers to measure and monitor patients’ movements in a range of settings while performing activities of daily living, and/or other specified tasks, to evaluate the patients’ functional capabilities, to assess the efficacy of new rehabilitative treatments and their respective outcomes, to evaluate prosthetic/orthotic/pedorthic component functional performance, etc.

One of the key areas of research being conducted at the RERL is development, testing, and evaluation of prosthetic socket designs. Data is being collected and comparatively analyzed on the tissue stress-strain magnitude, gradient, and strain energy density distributions that are produced in amputees’ residual limb tissues by: (i) traditional patellar tendon bearing socket designs; versus newer (ii) ambient pressure cast total surface bearing (TSB) sockets; versus (iii) positive pressure cast TSB sockets; versus (iv) negative pressure cast TSB sockets, and the consequent circulatory and metabolic impact the resultant stress-strain values have on residual limb tissues. Kinematic data collected with the Vicon system, in concert with information obtained on intra-socket loading and gait timing with Tekscan FScan and PScan transducers and the CIR Systems GaitRite Electronic Walkway, are being used to determine relationships between amputee residual limb geometric, morphological, and mechanical characteristics, and prosthetic socket design geometries and material properties, and prosthetic components’ biomechanical characteristics and alignments. Intra-socket pressures are measured with two 1360 element Tekscan PScan FVR transducer arrays, lining the inside of the respective sockets (Figure 1a). As the subject walks, data is synchronously collected by the Vicon, Tekscan, and GaitRite systems, and the Kistler force platforms. The resultant socket/residual limb interface pressure distributions produced by the respective socket designs (as shown in Figure 1b for a PTB socket at midstance) are being comparatively analyzed as a function of the subjects’ respective residual limb tissue morphology and mechanical stiffness, as determined from MRI scans and indentation studies (Figures 1c and 1d) of the subjects’ residual limbs with and without their sockets donned, with and without external loading applied. Vicon recordings of the subject’s gait kinematics (Figure 1f) together with GaitRite, Tekscan FScan, and Kistler force platform measurements of the respective resultant pedal plantar loading reveal the dynamic effects differences in the respective socket designs can have on the subjects’ static and dynamic stability, and their gait, (Figure 1g).

Another key area of research being conducted at the RERL is development, testing, and evaluation of orthosis designs for hemiplegic, multiple sclerosis, and traumatic injury patients. Orthotic cuff/limb tissue and pedal plantar stress spatiotemporal distributions produced by various orthoses are being synchronously measured and comparatively analyzed in conjunction with kinematic data collected with the Vicon system, Tekscan FScan, CIR Systems GaitRite Walkway, and Kistler force platforms, to determine the effects different orthosis designs have on subjects’ static and dynamic stability, their gait kinematics, and ambulatory strength and energy requirements. “Near normal” results are shown in Figure 2 for an experimental subject wearing a dual-axis (ankle-subtalar joint) orthosis in a comparative study of ankle-foot orthoses. Intra-subject comparative analyses between right and left limb kinematics for given orthosis designs, as well as between different designs, help reveal trends in performance for categories of subjects that can be used to establish prescription guidelines for the respective orthoses.

Figure 2a. Placement of photoreflective markers on an experimental subject in a comparative gait trial evaluating the kinematics of ankle foot orthoses.	Figure 2b. The experiment subject wearing a dual-axis AFO which allows relatively “normal” kinematic function compared to plastic posterior leaf spring design AFOs.
Figure 2c. Vicon BodyBuilder 3-D projected views of the subject in Figure 2b walking in a dual-axis AFO.	Figure 2d. Resultant pedal total and regional stress measurements and corresponding limb and body segment trajectories over a gait cycle for the subject in Figure 2b wearing the dual-axis AFO on her right leg. Comparative analysis of ipsilateral and contralateral limb measurements reveal advantages and disadvantages of orthosis designs.

A third principal area of RERL research is Pedorthics. As shown in Figure 3a, patients’ pedal biomechanical functional capabilities and deficits are assessed with video and Vicon system measurements. Their 3D pedal spatial geometry is measured with the VA Pedorthic Optical Digitizer (Figure 3c), and the resultant digitized data input into the VA Pedorthic CAD/CAM System (Figure 3b), where custom shoe lasts, insoles, and footwear upper patterns are designed and fabricated for subsequent assembly and fitting. Pedorthic research is also being performed measuring static and dynamic plantar and dorsal loading over a range of conditions to establish safe load limits for neuropathic diabetic patients with little to no sensation in their feet, (Figure 3d). The effects of rocker sole designs on pedal plantar loading and gait kinematics and stability in diabetic Charcot patients and rheumatoid and osteoarthritic patients are also being studied, (Figure 3e).

Figure 3a. Biomechanical assessment of a pedorthics patient’s foot and ankle function. Previous video recordings and subjective assessments can be replaced with quantitative measurements of segmental trajectories, velocities, and accelerations recorded with the Vicon System.	Figure 3b. 3-D digitization of an experiment subject’s foot and ankle with the VA Pedorthics Optical Digitizer.
Figure 3c. VA Pedorthics CAD/CAM System design of a custom orthopedic last and shoe patterns for the patient in Figures 3a and 3b.	Figure 3d. Total and regional pedal plantar and dorsal stresses for the subject in Figure 3a and 3b in an orthopedic shoe measured with Tekscan FScan and IScan transducers and Kistler force platform.
	Figure 3e. Body segment model of a diabetic pedorthics patient over a typical gait cycle when wearing a rocker sole shoe.

A fourth area of research where RERL investigators have taken advantage of the “portability” of the Vicon system is measurement and analysis of patients’ upper limb movement patterns while performing ADLs. RERL investigators have measured upper limb segmental trajectories and velocities of hemiplegic, Parkinson’s disease, and rheumatoid arthritic patients when performing tasks such as following a target LED in space to reveal visual field deficits and/or inhibited movement patterns, or opening a tamper-proof medicine container as shown in Figure 4. Such analyses have proven effective in developing alternate movement strategies for hemiplegics, and in assessing treatment efficacies in Parkinson’s patients. They also can prove beneficial in design of new types of containers that are not as “painful” to open for arthritic patients.

Figure 4. Application of the Vicon system in upper limb movement analysis of an arthritic patient tracking hand and wrist movements when opening a tamper-proof container.

The Vicon motion analysis system has proven to be a powerful and widely applicable tool for measurement and analysis of movement. RERL researchers are just beginning to tap its capabilities. As technology continues to develop, the RERL researchers look forward to watching the capabilities of the Vicon system grow, so the problems that can be taken on and solved in Rehabilitation Engineering will also expand.