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Research Reports |
We thank Robertson for her insightful commentary on our study1 and for his documentation of the emerging potential for future uses of ultrasound (US) in physical therapist practice. We agree that recent research holds promise for the benefit of therapeutic US for bone healing2,3 and for the benefit of diagnostic US using specific imaging technology.4
However, the purpose of our study was to examine current and common practices among physical therapists who had achieved the designation of Orthopaedic Certified Specialist (OCS) for using therapeutic US to manage musculoskeletal impairments. It was not the purpose of this study to examine US's untapped potential. We believe our survey design provided ample opportunity for early adopters of emerging therapeutic US applications to identify and describe these uses. Each respondent had the option of self-selecting up to 2 "other" impairments for which they would use US and answering all survey questions based on these self-selected uses. As Robertson noted, only 19 of 205 respondents identified uses of US other than the 6 researcher-selected options. No pattern of "other" uses emerged. One person identified "bone healing" as a condition for which US is used. The low number of "other" uses suggested to us that we had adequately captured the common uses of US by OCSs.
We agree that there is growing evidence supporting the benefit of low-intensity US for bone healing. However, the low-intensity pulsed ultrasound (LIPUS) machine described in the articles by Heckman et al2 and Warden3 is typically not used by physical therapists. The LIPUS machine utilizes parameters not available in the typical clinical model US machine, and LIPUS most typically is self-applied at home using a unit purchased by the patient. It is unclear at this time whether the skills of a physical therapist are needed to deliver this intervention specifically for bone healing. A recent animal-model study,5 published after our study was completed, reports promising findings for the ability of US to promote bone healing using a conventional US machine. However, human subject studies still are needed to fully confirm the benefit in humans with fracture. The skills of a physical therapist would seem to be necessary if a conventional US machine is used, as the risk of injury from excessive heating is a real danger.
Our study did not inquire about OCS use of diagnostic US. In 2003, when preparing our survey instrument for distribution, we found no evidence in the literature that physical therapists were using US technology for diagnostic imaging, nor was this use identified by any of the physical therapists who helped pilot test the survey instrument for content validity related to the uses of US in the United States. Whether diagnostic US imaging will (or should) be applied by physical therapists in the future is an intriguing consideration. However, we see little evidence that this is an emerging area for consideration for physical therapist practice at this time.
Robertson identified several specific concerns for which additional clarification is helpful. We are happy to have the opportunity to clarify.
Concern was expressed that we did not include a category "promoting the repair of ligaments, tendons, cartilaginous tissues, and muscle." However, "tissue healing" was 1 of the 6 researcher-identified categories that subjects responded to throughout the survey. The survey instrument did not divide this category any further into specific tissues or specific stages of healing. We captured only the general category "tissue healing." Indeed, identification of specific tissues or specific stages of healing would have enhanced this category. The decision to use one overall category stemmed from our overriding concern that a lengthy survey instrument would negatively affect response rate. We believe the category "tissue healing" would be chosen by respondents who use US to promote soft tissue repair. Forty-seven percent of the respondents believed US was clinically important for tissue healing.
When reporting the temporal average intensity (TAI) scores for this study, we did not separate TAI scores by preferred US frequency (1 MHz or 3 MHz). However, we did examine the scores for each category in our initial analysis of data. The difference in TAI scores for respondents who chose 1-MHz versus 3-MHz frequency was no more than 0.2 W/cm2 for any of the 12 categories (6 impairment categories, each with a superficial tissue and a deep tissue option). Thus, we aggregated scores. This finding supports Robertson's concern that respondents who use US at 3-MHz frequency may be using an excessively high TAI.
Robertson provides greater specificity about the history of US. We agree that reports of the potential for therapeutic benefit from US, based on both animal and human studies, were available well before the 1950s. However, the intent of the statement in our study, consistent with the purpose of our study, was to indicate that, by the early 1950s, US had moved from the early stages of development and testing into the mainstream of use.
Robertson suggests that one explanation for the 56% of OCSs who chose not to respond to the survey could be that clinicians who do not value US did not see the survey as useful and, therefore, did not respond. This would result in a biased sample. Although any interpretation of why individuals chose to respond or not to respond is conjecture, the organization of the survey instrument provided some guarding against such bias. The wording of the survey provided clear and easy opportunities for respondents to choose "would not use" if they did not believe US was warranted. It is our opinion that those with a strong position about the lack of usefulness of US would be just as likely to respond to the survey (expressing their opinion that US was not useful) as those with a strong opinion about a positive benefit of US. For example, respondents were asked directly about the importance they placed on US as an adjunctive modality. In response to this question (summarized in Tab. 2), 27.4% indicated they would not use US for soft tissue swelling, and 20.2% indicated they would not use US for pain management.
We undertook this study very aware of the limited evidence to either clearly support or clearly refute the use of US for many conditions for which US has historically been used. As indicated in the introduction to our study, we examined 15 systematic reviews of US spanning a variety of musculoskeletal conditions. A consistent conclusion, identified in 116–16 of the 156–20 systematic reviews, was that there is insufficient high-quality evidence to make an informed judgment about the clinical benefit of US. This is a very different conclusion from one that there is sufficient evidence to state that an intervention is ineffective. Each systematic review called for additional well-designed clinical studies to help answer the question of effectiveness. The statement in the discussion section of our article that indicates there are very few clinical trials supporting the clinical effectiveness of US is followed by a statement in the next sentence indicating that there also is insufficient evidence to refute the effectiveness of US. Our study did not delve into the rationale for why specific impairments and parameters were preferred. This is an area for future research. Did practitioners base their judgment on a critical assessment of the void in the literature combined with their critical reflection on the effectiveness of US on their patients? Or, rather, was their judgment based on uncritical habits and unexamined expectations of effectiveness?
We do not suggest that therapeutic US should continue to be used simply because it is currently being used by advanced practice clinicians. However, in the absence of convincing scientific evidence to either support or refute any commonly used technique, the opinion of expert practitioners is a level of evidence that should not be discounted without careful examination. This study gathered self-report information about the clinical conditions for which advanced practice clinicians use US. Future researchers should incorporate this information as one of their decision-making factors driving their prioritization of conditions most in need of intervention effectiveness studies. Well-designed clinical trials should provide the evidence to definitively answer these questions.
Evidence-based practice utilizes a hierarchy of evidence to guide clinical decisions. When insufficient scientific evidence exists, evidence from expert clinicians often is used. The judgment of the advanced practice clinicians in our study was that US is a useful adjunctive modality for several conditions. Thus, it seems reasonable that conditions for which these advanced practice clinicians use US merit further investigation. Our findings suggest that soft tissue inflammation, tissue extensibility limitations, and scar tissue remodeling are the most commonly identified conditions for which US is used and identified as clinically important. Well-designed clinical studies will help determine whether the perception of benefit is justified.
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  V. J Robertson Invited Commentary Physical Therapy, January 1, 2008; 88(1): 58 - 61. [Full Text] [PDF]
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