A recent study published in the Journal of Biomechanics shows the opportunity for increased rigor and randomization in orthotic- and prosthetic-related research, according to study co-author Michael S. Orendurff, BS, MS, PhD, director of the Biomechanics Laboratory for Orthocare Innovations. The researchers continue to mine the data for additional results of the study.
While the study’s focus was determining whether patients in blind trials displayed a preference for particular prosthetic feet, Orendurff said its goals were much broader.
“We were interested in how practitioners make prescriptions for prostheses and what specific categories of prosthetic feet are available. Because the field had never really received any funding to look at the comparative effectiveness question of whether there is an appropriate prosthetic foot that is best for a particular type of individual, there is a lack of evidence-based information to support this type of clinical decision making,” he said. Additionally they had hoped to find “whether the prosthetic user’s preference for a specific category of prosthetic foot is related to some biomechanical measure or some perception of an induced increase in community activity.”
Trial design, methods emphasized over results
The study used a small load cell at the base of the socket, in addition to traditional force plates, to measure the sagittal movements of 11 transtibial amputees at MFCL, K2, K3 and K4 functional levels. These sagittal movements were recorded during walking in three objective categories of prosthetic feet: stiff, intermediate and compliant. Prostheses were randomly assigned and blinded from participants and investigators. After laboratory testing, participants underwent a week of wear tests in the community and completed a modified prosthetics evaluation questionnaire.
Michael S. Orendurff
Orendurff said the methods used in the study set it apart from other studies in the O&P field.
“The idea was to try to create a rigorous study that had all the characteristics of the best clinical trials,” he said, comparing the study to a double-blind placebo-controlled trial of a drug, “where nobody knows what they are getting.” This is the best and most accepted way of assuring the validity of the data from the study, he said.
He said the patient preference results are not the most important outcome of the trial.
“The most important aspect of this work was the design and completion of a trial in prosthetics that is double blind and randomized and has measures from three different complementary domains that are critical to understanding the efficacy of prosthetic prescription.”
The trial showed that the majority of patients studied preferred prosthetic feet categorized as compliant. But Orendurff cautioned, “It was not a big enough sample to be conclusive, and therefore the results cannot be generalized with confidence to all lower extremity prosthetic users. So we need a big trial to figure out what the right way is to prescribe feet to people.”
Despite the size of the study, Orendurff was intrigued by the results.
Silvia U. Raschke
“It is the first time any published research has shown a biomechanical measure that was related to patient preference for a specific, objective category of prosthesis – those with lower peak moments during gait. But it is interesting that prosthetic users in the study only developed their perception of the prosthetic feet they were testing after they wore it during the week-long community testing.”
Silvia U. Raschke, PhD, research faculty member at the British Columbia Institute of Technology, who also co-authored the study, emphasized the importance of the tools the study uncovered for the prescription of prostheses.
“This is actually a huge step forward for prosthetics and orthotics,” she said. “I think more recently as the pressure has started to be applied to rehabilitation professionals to actually justify their decisions from those insurance companies, it has become a lot more onerous to try to justify prescriptions for prostheses based on subjective measures … This has raised the importance of this as a research issue and we have more researchers around the world actually looking at this as a topic and that means we are actually going to start to get some results because we are going to get a critical mass around this topic.”
Methods needed to determine best foot for each patient
While the trial size was small, Orendurff said the results show the need for further research.
“I am actually pretty startled by the finding. I think it is probably much more likely that the conclusion [of continued research] is going to be that there are a certain set of criteria that make individuals fall into particular categories of preferred feet.”
Raschke said, “We were able to link the functional performance of the foot or the design of the foot with something the amputee actually perceived. That is important from a patient-centered point of view. This has the potential to validate that a patient’s opinion or experience with a certain component or device should actually be listened to.”
She added, “We did this in a double blind setting. This means that in identifying these difference between categories of feet, the amputees were not actually impacted by advertising or what they have read on the Internet or the ‘cool’ factor of technology.”
The current system for prescribing prosthetic feet is not supported by clinical evidence, Orendurff and Raschke noted, so further research could dramatically change the way prostheses are prescribed and reimbursed.
“Right now, the K-levels that are established for amputees … That idea has no rigorous published evidence,” Orendurff said. “Nobody has ever validated that as being an appropriate way to categorize patients or to allow prescriptions for particular components. So there is no reliable evidence that somebody should get a SACH foot because they are a K1 [level] or a super high-end carbon fiber foot because they are a K4 [level]. The entire idea has no rigorous scientific evidence behind it.”
Orendurff suggested that K levels are a form of health care rationing without scientific evidence.
“Can you imagine your mother or father being denied insurance coverage for a stent surgery because their functional level was not high enough to get a benefit from the vascular prosthetic? No one would accept that without irrefutable evidence that there would be no benefit.”
He added, “There are approximately 75 different prosthetic feet on the market … so that makes it difficult to do comparative effectiveness research if you have to compare all 75 feet against each other. It is just mind numbing trying to think of the statistics or trying to get any kind of clinical, meaningful recommendations out of the data. That has been a huge setback to the field. But with this research design our team has just published, we finally have an objective framework for categorizing the types of prosthetic feet, and we can now determine the effect on the patients mobility in the community, the forces they subject their limb to with every step, and what foot the patient prefers, all with the highest scientific rigor.”
Laying the ground work
Orendurff said while this study shows promise, it is the first step on a long road that needs to be traveled in order to raise the level of rigor of – and the funding for – O&P research.
“The whole idea is to use this study as pilot work to support an application for a large, multi-center clinical trial as rigorous as a clinical trial would be in any surgical intervention or a big pharma trial. A definitive and trustworthy trial in prosthetic foot prescription would have a range of participants on an objective, functional scale.”
An ideal group for this study would be 400 to 500 participants, he said. A study of that size would provide adequate statistical power for all measures to trust the results.
While Orendurff, Raschke and colleagues have applied for funding to support additional trials, they said, researchers find it difficult to obtain funding from governmental institutions for O&P research. Part of the reason is the cost – Raschke said for a study of prosthetic feet, prosthetic components make up roughly 50% of the budget, which is high.
“It is sort of a catch-22 situation, where they tell us we need more rigorous research but when we correctly and honestly budget the project we get knocked out of the running because of the expense,” she said. Having funding from a manufacturer of prosthetic feet – even just in providing prosthetic feet to be tested – would introduce the perception of bias and reduce the perceived rigor of the research conclusions, she said.
Another issue is the priority level for the program managers at the various institutions and centers of the NIH, he said. Orendurff said funding typically is directed toward the cause of limb loss – such as diabetes, cancer or congenital disease – rather than limb loss effects.
“The NIH deals with scientific opportunity, not necessarily disease burden, but you do not get ‘scientific opportunity’ unless you invest in the research to lay the ground work for rigorous comparative effectiveness research,” Orendurff said. “The better we get and the more rigorous our trials get, the more likely it is that we actually solve this and answer some of the questions for people making prescriptions and providing prostheses and orthoses.” – by Amanda Alexander
Orendurff M. et al. J Biomech. 2015; doi:10.1016/j.jbiomech.2014.10.002.
Disclosure: The authors report the study was funded by the American Orthotic & Prosthetic Association.