Orthotics/Prosthetics

Assessing amputee gait patterns can be a remarkably complex and challenging task for prosthetists. Lack of access to gait laboratories combined with time constraints and added costs represent major barriers to formal gait analysis for most practitioners. Instead, prosthetists traditionally have relied on observational analysis learned and refined over years of clinical practice to assess gait patterns. However, with all of the technological advances that have occurred in recent years, various tools have become available that can aid practitioners in making some basic gait measures.

Observational analysis

Because most practitioners do not have access to instrumented gait analysis, they rely primarily on observational gait analysis to assess amputee gait in the clinic setting. Practitioners make specific prosthetic recommendations, changes and design features based primarily on visual observation of patients walking on their check socket. Many gait deviations can be observed in the frontal plane even if they do not occur in that plane, John T. Brinkmann, MA, CPO/L, FAAOP, an instructor at Northwestern University Prosthetics-Orthotics Center and Gait Society chair for the American Academy of Orthotists and Prosthetists, said.

	John T. Brinkmann

“The most common thing is to observe gait in the frontal plane, so you are having the patient walk away from you and toward you. Ideally it is good to also get a view from the sagittal plane,” Brinkmann told O&P Business News. “The reality of most office situations is you do not have a great way of doing that. Patients can walk down a hallway away from you for 20 feet, but to get a true sagittal view you either have to watch patients as they walk by the door of the exam room, or you have to follow alongside them. It is helpful to have a big enough room that you can stand in one place while they walk.”

One of the most basic and easily accessible tools practitioners can use in the clinical setting to aid in assessing gait is a camera with the capability of slow motion. Although the ideal setup is to use a camera and tripod so that the camera remains steady and the right plane can be captured, Brinkmann noted that even a smart phone can be used to capture video.

“The single greatest thing anyone can do for orthotic or prosthetic gait assessment is to capture video,” Brinkmann said. “Being able to watch the same gait cycles multiple times and then slow down the video, especially in more complicated cases, is invaluable. Even for an experienced person assessing gait visually, there are so many things going on in such a short amount of time that it is hard to catch the nuances.”

Video allows practitioners to evaluate separate segments of gait and their relationships to each other. The video also allows practitioners to rewatch a patient’s gait cycle without having the patient walk multiple times. Moreover, the initial video can be used as a baseline to compare with future videos obtained after additional interventions and adjustments to assess the effects of therapy and determine if there has been any improvement.

	Steven A. Gard

Brinkmann noted less expensive camera systems also are becoming available. Although such systems are not as sophisticated as those available at full gait labs, some cameras allow for a view of approximately 180·. This enables the camera to be used in a narrow area to obtain frontal and sagitttal views of a patient walking down a hall.

“If you want to get a true sagittal side view, the camera has to be able to follow the person because as soon as you record at an angle, it changes the perceived joint angles, or it appears to,” Brinkmann said.

Gait mats and activity monitors

Another gait assessment tool that clinicians can use fairly easily in the clinical setting is a gait mat. Gait mats, which can be set up in a fairly limited amount of space such as a hallway, are designed to collect basic information as patients walk on the mat.

“One of the advantages of something like the GAITRite is that there is no subject preparation required. You simply roll out a mat and have people walk back and forth a few times,” said Steven A. Gard, PhD, executive director of Northwestern University Prosthetics-Orthotics Center, director of Jesse Brown VAMC Motion Analysis Research Laboratory, and a research associate professor in the department of physical medicine and rehabilitation at Feinberg School of Medicine.

Some of the fundamental gait parameters that are collected by gait mats include step length, cadence and walking speed. Practitioners can then use such measurements for documenting and tracking patient progress over time.

“Walking speed itself is one of the first gait parameters that I look at when I am doing an evaluation of pathological gait because generally people will adopt a freely selected speed of walking at which it is thought that they minimize energy expenditure,” Gard told O&P Business News. “Walking speed has been shown to be proportional to energy expenditure during gait, so a person with greater impairment will tend to walk slower. If you have an intervention that improves the way that somebody walks, then presumably you are increasing function and making that gait more efficient.”

Image: Courtesy of Steven A. Gard, PhD

To obtain walking measurements collected over a longer period of time, practitioners can use Orthocare Innovations’ StepWatch Step Activity Monitor. Basically an accelerometer, the StepWatch is a microprocessor-controlled device that can be strapped onto a patient’s prosthesis to record the patient’s walking activity for up to period of 2 months. At the end of the monitoring session, the collected data collected are downloaded and analyzed by accompanying software.

The StepWatch Step Activity Monitor can provide a good snapshot of how patients are using their prosthesis in the real world, Gard said. In addition, he noted that the monitor has been used to compare patients’ activity levels wearing different types of prosthetic components.

Compas and Smart Pyramid

Compas (Computerized Prosthesis Alignment System) and Smart Pyramid from Orthocare Innovations is a technologically advanced assessment tool designed specifically for prosthetic use in a clinical setting. The system, first realeased in 2009, is designed to aid prosthetists in aligning prostheses.

“The Compas and Smart Pyramid is the first accessible gait assessment tool for prosthetics that bridges the gap between observational gait and a full-fledged gait lab,” Brinkmann said. “It is an extremely exciting development because it now takes a completely subjective process and puts some kind of actual numbers to it, which we have never had for prosthetics unless you put somebody in a gait lab.”

The system consists of two parts. The Smart Pyramid is basically a pyramid with a four-hole pattern that is mounted to the socket and contains the actual sensors. The Compas Master unit is attached to the Smart Pyramid for active data collection during a patient’s office visit and then the data is sent via Bluetooth to a computer to be analyzed. After the data collection has been completed, the Compas Master unit is removed.

“The device has a set of eight strain gauges built into it to measure the strain across this pyramid, and when all of that data gets dumped into the software, what you get is two moment profiles,” Jason Wening, MS, CPO, FAAOP, clinical research director at Scheck & Siress, said. “It is a moment profile at the Smart Pyramid, wherever that happens to be in the prosthesis, and it is in the sagittal and coronal plane, so front to back and side to side if you have the pyramid aligned and calibrated correctly.”

The IPecs Pro System will provide objective data to help prosthetists align and fit prosthetic devices.

Image: College Park Industries

Wening noted that the system is not set up to address all six degrees of freedom that prothetists normally consider for alignment. The system does not have the ability to assess whether the height of the prosthesis is correct or whether the transverse rotation is correct.

“You can take the data and with a good clinical understanding of the type of patient that you are dealing with, the gait habits that patients present with when they walk in the door, the type of foot that they are using on the prosthesis, the type of knee that they are using, the design and how well the socket fits, you can use the data that this system gives you to try to improve the alignment of the prosthesis,” Wening told O&P Business News. “The logical leap would be if you have improved the alignment of the prosthesis, you have improved the gait pattern of the amputee walker. That is the end goal.”

In fact, the system can allow practitioners to identify alignment problems that they are unable to discern visually. “It makes us better because we think we are seeing certain things, but we cannot actually tell what is going on with a lot of the forces inside the socket and in the prosthesis. You just see these gross motions, such as a lean or a rotation problem,” Brinkmann said. “What they are finding is that you can align the prosthesis to where an experienced prosthetist thinks ‘This is perfect alignment.’ You can then put patients on this system and you will realize that significant changes would improve their gait.”

Because the system is designed for clinical use, the cost of the device is billed either to patients directly or to their insurance company as an inline alignment measurement tool that is part of the prosthesis. Wening noted that some insurance companies are paying for the device.

iPecs

Another tool on the market for amputee gait assessment is the iPecs Lab system from College Park Industries. The system, which has been available for approximately 2 years, was designed specifically as a research tool for gait analysis. Development of the system was partially funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development. College Park also worked closely with Northwestern University, and last fall the system was awarded first place in the Electronic product category in the NASA Tech Briefs Create the Future Design Contest, Mike Leydet, director of research at College Park Industries, said.

The iPecs Lab has the ability to measure six degrees of freedom comprising three-axis forces and moments including transverse rotation in a portable device that can be used in a variety of real-world environments.

“You can collect a lot of this data with different means inside a gait lab, but if you want to go outside of the gait lab, this is the device for amputee gait analysis,” Leydet told O&P Business News. “Literally, you could walk for 2 hours up a mountainside and collect every one of those steps, bring it back, and start to analyze and characterize some of the types of loading conditions that you would see in that environment.”

Although the iPecs Lab is geared specifically toward researchers, College Park just recently received a patent for a clinical version, which will be called the iPecs Pro. Leydet estimated the iPecs Pro would be available for practitioners to use in the clinical setting within the next 6 to 8 months.

“The challenge there is really trying to take and provide a very utilitarian approach to assist in the alignment process and then provide documentation features for the prosthetists so that they can help support their reimbursement claim,” Leydet said. “We all know how that is a hot topic, and that is the way the world is going, outcomes based, having objective measures to support what we do on a daily basis, whether you are an engineer, physician or a prosthetist.”

Leydet noted that the iPecs Pro is being designed to assist prosthetists in the alignment and fitting of prosthetic devices and also to provide objective rather than subjective data. In addition, he noted that while the cost of the iPecs Pro has not been determined as yet, they are working to make it as affordable as possible for clinicians.

Gait analysis markers must remain stable for accurate measurement.
Image: Steven A, Gard, PhD

“The reality is it is much tougher to make that product for the clinician because it has to bridge the gap between the research talk and the engineering talk, and what is practical for making reasonable adjustments to the prosthetic fitting,” Leydet said. “Essentially, we’re merging cell phone technology with some high-end computer software applications along with an industrial load cell system, and there are a lot of hoops to jump through to be able get all of those things to work together in unison and then provide something that is meaningful for the end user. It is definitely one of the most exciting and challenging programs our engineering team at College Park has ever worked on.”— by Mary L. Jerrell, ELS

Disclosure: No sources for this story had any relevant financial disclosures.