The usual purpose of lower-limb orthoses and prostheses is to enable or improve the wearer's gait. How well the device achieves this goal has historically been judged subjectively by the patient and clinician. "Nevertheless," says Joan E. Edelstein, MA, PT, FISPO, CPed, adjunct professor in the Department of Physical Therapy at New York University (NYU), New York, and a former senior research scientist in the now defunct NYU Department of Prosthetics and Orthotics, "one's opinion of the ease and comfort of walking, while important, is idiosyncratic. No one can really know another person's feelings." Consequently, it is imperative that an unbiased person documents the efficacy of the treatment using objective measurements. "Accurate [valid] and consistent [reliable] measurements," she says, "are fundamental to objective measurement."
Obtaining objective, accurate, and consistent gait measurement information, however, is notoriously difficult. From person to person, condition to condition, even between genders, gait differs. Foot shape, foot size, and musculature, among other things, all influence how a person walks.
"Even gait assessment using fully instrumented gait labs is subject to errors related to marker placement and complex mathematical equations," says John Brinkmann, MA, CPO, LPO, FAAOP, lead prosthetic instructor at the Northwestern University Prosthetics-Orthotics Center, Chicago, Illinois, and chair of the American Academy of Orthotists and Prosthetists (the Academy) Gait Society. "Detailed measurement of the individual structures of the foot is so difficult that it is generally considered one unit for the purposes of gait assessment. Any practitioner treating foot/ankle disorders is aware of the significant impact that even minor variations on foot structure and function make on a patient's gait and overall function."
Regardless, experts interviewed by The O&P EDGE agree that accurate, consistent, and objective gait measurement is critical not only for the successful application of lower-limb orthotic and prosthetic devices, but also in the documentation of O&P outcomes. (Editor's note: For more information about the importance of outcomes documentation, read "Outcome Measures: Are We There Yet?" in this issue.)
Equally important to measuring the data, Brinkmann says, is knowing how to use and apply the data that is collected. "Practitioners will need to improve their knowledge of the science of gait," Brinkmann says. "We can't take advantage of more advanced tools unless our understanding increases. We have to do more than show that the structure of a body segment was favorably impacted [by an O&P device]. We need to explain how overall function changed." And while "outcome reports based on sound scientific data, will be meaningful and useful, [they] will only be as good as the data that is collected and the quality of the analysis."
Christopher Hovorka, MS, CPO, LPO, FAAOP, co-director of the master of science in prosthetics and orthotics (MSPO) program at the Georgia Institute of Technology (Georgia Tech), Atlanta, agrees. Not only does gait measurement help to assess a successful outcome, from a diagnostic perspective it also is crucial for describing and quantifying the magnitude of the disorder. "Reliable, objective, and accurate assessments of gait are critical for problem identification and treatment outcome as well as estimation of future performance with orthotic/prosthetic treatment," he says.
"3-D [three-dimensional] instrumented analysis remains the gold standard of gait assessment because it has the highest degree of objectivity," Brinkmann says. "Systems with less objectivity can improve collaboration and decision making among professionals but have less value as outcomes tools. Collecting and analyzing data using 3-D instrumented systems will contribute greatly to our understanding of the impact of our interventions."
While 3-D gait analysis instrumentation and analysis systems have improved over the years—they now provide enhanced resolution of limb-segment motion and can predict the location of joint rotation—these systems are expensive and require skilled, knowledgeable persons to operate them, Hovorka says, which means additional personnel costs. Because of this—not to mention the considerable space that is needed for the cameras to record the subject's movement in the capture zone—such systems are mostly used in academic and research centers and large clinical practices with plenty of resources.
Generally, less expensive and less cumbersome equipment incorporates instrumented force mats that record groundreaction forces and the coordinates of each step a person takes, Hovorka says. Many of these more portable systems include digital and video software tools, strain gauges, and accelerometers, Brinkmann adds. The GAITRite System by CIR Systems, Sparta, New Jersey, for example, is an instrumented mat that enables rapid data collection and analysis.
"By combining the portable instrumented force-recording mat with digital video capture, a less expensive and relatively reliable portable 3-D gait lab may be created and used with some success in the clinical arena," Hovorka offers.
"Videotaping provides a quick record of the walker's maneuvers although usually the analysis is subjective," Edelstein says. "Recording kinetics is more difficult in the usual clinical setting."
Brinkmann agrees that portable gait-measurement systems may not provide the accuracy of an instrumented gait lab, but they do provide practitioners with tools they can use in everyday practice to assess gait. Even so, cost remains the number one obstacle preventing practitioners from using these systems regularly. Time is also a factor.
"Treatment time is finite," Edelstein says. While "assessment is essential to rational treatment planning…whatever time a clinician uses to document a patient's performance subtracts from total treatment time."
"Decision makers have to make tough decisions about how to invest money, and it is unlikely that the acquisition cost of this sort of technology will reduce enough to make the decision an easy one," Brinkmann says.
There are other limitations as well. For instance, motioncapture data is usually collected at a clinic, but that's not where an orthosis or prosthesis wearer resides or spends most of his or her time, Hovorka notes.
Researchers at Georgia Tech are hoping to address some of these issues. Géza Kogler, PhD, CO, LO (IL), LPed (IL), director of the Clinical Biomechanics Lab at Georgia Tech, is designing a wearable 3-D motion-capture system that records movement of limb segments via inertial measurement units (IMUs), which are akin to relatively inexpensive gyroscopes. Meanwhile, Hovorka and a team of investigators are developing an anchor system for the IMUs to attach to lower-limb orthoses and prostheses. The IMUs can record a person's movement as he or she walks in home and community environments, Hovorka says.
"Kogler's lab is also developing the motion-analysis software to analyze and interpret the recorded movement data from the IMUs so that the movement of the person can be used to reliably, accurately, and objectively quantify the movement of the person as a clinical outcome measure," Hovorka says.
Such wearable measurement technology "is one emerging technology that has the potential for widespread use by the everyday clinician once the technology is validated through ongoing pilot investigations and a future clinical trial," he concludes.
There is still something to be said for simplicity, Edelstein says. "A basic stop watch can accurately record time/distance aspects of gait with a minimum of expense or space utilization."
For many years, strain gauges in the socket or in the shoe have been used on a limited basis in research aimed at improving socket design, she adds. However, "it is unlikely that such devices could give the wearer more usable information than is now available."
Or is it?
Zach McKinney, a graduate student in biomedical engineering at the University of California, Los Angeles (UCLA) Center for Advanced Surgical and Interventional Technology (CASIT) is developing a tactile feedback system for individuals with transtibial amputations that provides additional sensory awareness of prosthetic devices.
The system provides the user with real-time tactile feedback denoting both the location and magnitude of loading on the prosthetic foot, which can help the user improve his or her gait. The system's sensing technology may be used as a gait analysis tool in future iterations.
"Though the current version of our mobile tactile feedback system uses the sensor data only for the provision of feedback in real time, we expect future versions of the system to provide the capability of logging this sensor data, in which case the data could certainly be used for gait assessment," McKinney says.
The device is currently in prototype form, and McKinney says that the electronics and pneumatics need to be further streamlined and miniaturized "to provide for convenient use in the home and clinical environments."
Brinkmann says he is "optimistic that over time we'll see more systems that offer improved reliability and validity and that can be integrated into everyday practice relatively easily." However, he stresses that individual practitioners and practices "need to adopt protocols that can be accurately repeated to ensure that the data collected is meaningful, particularly when using tools that are inherently less reliable and valid than 3-D assessment."
"Though is it unlikely that any technology will fully replace visual observation as a primary means of gait assessment, supplemental technologies are needed to provide objective, repeatable outcome measures for gait," McKinney adds. Lowerpriced alternatives "will become increasingly important as they become validated by clinical research to provide accurate, meaningful patient outcome measures." As cost becomes an increasing constraint to high-quality healthcare, "the rehabilitative technologies that prevail will be the ones that offer the best combination of low cost and high benefit."
Garrison Wells is an award-winning freelance writer and author based in Colorado Springs, Colorado. He has written for newspapers and magazines nationwide and authored five books on martial arts. He can be reached at
