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Abstract

Background and Purpose: For many years, ultrasound (US) has been a widely used and well-accepted physical therapy modality for the management of musculoskeletal conditions. However, there is a lack of scientific evidence on its effectiveness. This study examined the opinions of physical therapists with advanced competency in orthopedics about the use and perceived clinical importance of US in managing commonly encountered orthopedic impairments.

Subjects: Four hundred fifty-seven physical therapists who were orthopaedic certified specialists from the Northeast/Mid-Atlantic regions of the United States were invited to participate.

Methods: A 77-item survey instrument was developed. After face and content validity were established, the survey instrument was mailed to all subjects. Two hundred seven usable survey questionnaires were returned (response rate=45.3%).

Results: According to the surveys, the respondents indicated that they were likely to use US to decrease soft tissue inflammation (eg, tendinitis, bursitis) (83.6% of the respondents), increase tissue extensibility (70.9%), enhance scar tissue remodeling (68.8%), increase soft tissue healing (52.5%), decrease pain (49.3%), and decrease soft tissue swelling (eg, edema, joint effusion) (35.1%). The respondents used US to deliver medication (phonophoresis) for soft tissue inflammation (54.1%), pain management (22.2%), and soft tissue swelling (19.8%). The study provides summary data of the most frequently chosen machine parameters for duty cycle, intensity, and frequency.

Discussion and Conclusion: Ultrasound continues to be a popular adjunctive modality in orthopedic physical therapy. These findings may help researchers prioritize needs for future research on the clinical effectiveness of US.

For decades, ultrasound (US) has been a widely used and well-accepted physical therapy adjunct modality throughout the world,17 particularly for the management of musculoskeletal conditions.1,2,47 Ultrasound was first introduced as a therapeutic modality in the 1950s, when both animal and human studies demonstrated its ability to safely heat tissue several centimeters below the skin, particularly tissues that are high in collagen.8,9 This finding, combined with studies demonstrating that collagenous structures yield better to a stretch when they are warmed (within therapeutic ranges), bolstered the popularity of US, particularly for conditions such as shortened tendons and muscles, joint capsule tightness, and scar tissue limitations.10 In the late 1960s and 1970s, reports on the nonthermal therapeutic effects of US, primarily in the area of enhanced tissue healing, further bolstered its popularity.11,12

Although US has been a popular adjunct modality for decades, the lack of studies confirming its benefits has led contemporary scientists to question the traditional view of its therapeutic benefits.3 Indeed, eleven1323 of fifteen3,1326 systematic reviews could not draw any definitive conclusions about the effectiveness (or lack of effectiveness) of US because of insufficient evidence. Several reviews3,16,24,26,27 also report disagreement and confusion about the most efficacious treatment parameters for US.

Against this backdrop, anecdotal reports from clinicians suggest that US remains a popular modality. It has been nearly 20 years since the use of US in the United States has been assessed.4 In that study, 79% of respondents reported using US at least once per week, and 45% more than 10 times per week. The study, however, did not attempt to identify specific conditions for which US was used. Has US remained a popular modality and, if so, for which conditions is it most often used?

The purpose of this descriptive study was to determine how frequently physical therapists with experience in orthopedics use US and to determine their opinions about the clinical importance of US in achieving beneficial outcomes when managing common musculoskeletal impairments (eg, pain, soft tissue inflammation, tissue extensibility limitations, tissue injury, soft tissue swelling, and scar tissue limitations). Three research questions were addressed:

  1. How often do orthopedic physical therapists use US as part of the management of selected impairments?

  2. Do orthopedic physical therapists believe US is clinically important in managing these impairments?

  3. What US treatment parameters do orthopedic physical therapists use for management of these impairments?

Method

Target Population

Given the range of settings in which physical therapists practice, we wanted to provide some assurance that those responding to the survey had recent experience in orthopedics and were likely to be familiar with the orthopedic physical therapy literature. Thus, we chose to limit our population to physical therapists who have achieved the designation of Orthopaedic Certified Specialist (OCS). To become an orthopaedic certified specialist, physical therapists must demonstrate a minimum of 2,000 hours of direct patient care in orthopedics over the previous 10 years, with 25% of those hours occurring in the last 3 years.28 Physical therapists seeking certification as an OCS must also pass a written examination that assesses competency in the specialty practice of orthopedic physical therapy. An OCS must recertify every 10 years.

Although we have no direct assurance that physical therapists with the OCS designation are familiar with the current literature about US specifically, the nature of the certification process requires successful completion of a rigorous certification examination aimed at current best practice in orthopedic physical therapy. The likely career path of individuals who choose to pursue OCS certification makes it reasonable to assume that most individuals with the OCS certification are working with patients with orthopedic conditions.

Sampling Procedures

The American Physical Therapy Association's (APTA) List Rental Services Department randomly selected a sample of approximately 400 members of APTA who had an OCS certification. The List Rental Services Department randomly selected the Northeast and Mid-Atlantic region of the United States for the sample and provided mailing labels for all 457 APTA members with an OCS certification living in this region (Connecticut, District of Columbia, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Virginia, and West Virginia). In March 2003, following approval by the Marymount University Institutional Review Board for the Use of Human Subjects in Research, a survey questionnaire and cover letter explaining the study and informed consent procedures were mailed to all 457 physical therapists with an OCS designation. The return of a completed survey questionnaire implied the consent to participate in the study. Ten weeks after the first mailing, a second copy of the survey instrument was mailed to those who had not responded.

Respondents

Of the 457 survey questionnaires mailed, 213 were returned. Six of the 213 returned survey questionnaires indicated respondents did not want to participate in the study, yielding a 44.9% usable response rate. Respondents were 97 men and 104 women. Chi-square analyses revealed no significant differences in the proportion of survey respondents from each state compared with the OCS population in each state reported by the American Board of Physical Therapy Specialties.28 The age of the respondents ranged from 26 to 70 years (X̄=42.7, SD=7.6). The number of years since initial licensure as a physical therapist ranged from 3 to 41 (X̄=17, SD=7.4). The number of years of OCS certification ranged from 1 to 19 (X̄=5.5, SD=3.7).

Survey Instrument

We developed a 77-question survey instrument by first searching the existing research literature to identify impairments, treatment goals, and machine parameters commonly associated with the use of US. Based on this literature review, a list of potential survey questions was compiled and placed in draft survey format. This initial survey was presented to 10 experienced physical therapists. Feedback about the accuracy, comprehensiveness, and clarity of the survey's content was obtained from these initial reviewers and used to develop a more definitive survey for pilot testing of face and content validity.

The pilot survey instrument was examined sequentially by 3 separate groups of 5 physical therapists working in orthopedics. Each physical therapist completed the survey independently and then discussed his or her responses within a small group. The physical therapists described their interpretations of each question and explained why they answered each question as they did. For those questions for which there were discrepancies in interpretation among respondents, we sought suggestions for rewording. The research team considered the feedback from each group and made revisions based on this feedback. We then modified the survey instrument and presented it to the next small group. We continued to pilot test the instrument on small groups of clinicians until we achieved agreement on 90% of the items. When the research team reached a consensus on the instrument, a university professor with experience in survey research reviewed and approved the revised instrument.

The regularity of physical therapists’ use of US for each of the following 6 impairments was assessed by the survey instrument: pain, soft tissue inflammation (eg, tendinitis, bursitis), decreased tissue extensibility, delayed tissue healing, soft tissue swelling (eg, edema, joint effusion), and scar tissue remodeling. Respondents were asked to “Indicate the percentage of patients for whom you would include US, with or without phonophoresis, as an adjunctive therapy for each of the following impairments.” Respondents chose one of the following responses: (1) “with less than 10% of patients,” (2) “for about 25% of my patients,” (3) “for about 50% of my patients,” (4) “for about 75% of my patients,” and (5) “for more than 90% of my patients.” The option was available to list a maximum of 2 “other” impairments for which they would use US, in addition to the 6 listed impairments.

To assess beliefs about the clinical importance of US for managing the same 6 impairments, respondents were asked “For those patients whom you do treat with US, how clinically important do you believe US is in achieving each of the following therapeutic goals?” Respondents chose one of the following responses: (1) “I would not use US,” (2) “US is not important,” (3) “US is minimally important,” (4) “US is somewhat important,” (5) “US is very important,” or (6) “US is essential.” Again, the option to list 2 additional “other” impairments was available.

Lastly, respondents indicated the treatment parameters (duty cycle, intensity, frequency) they would use to achieve therapeutic goals related to each of the previously named impairments. Respondents selected 1 of 4 duty cycles (10%, 20%, 50%, or 100%) and 1 of 2 frequencies (1 MHz or 3 MHz), and they indicated the intensity (in watts per square centimeter) they would use for superficial and deep tissue. Respondents had the option to select “N/A” if they did not use US for the impairment. Demographic information was gathered to identify respondent's age, sex, state of residence, year of graduation from a physical therapist education program, and year of certification as an orthopedic certified specialist.

Data Analysis

Data from completed survey questionnaires were entered into the Statistical Package for the Social Sciences (SPSS), version 11.0.* Descriptive statistics were used to characterize the shape, central tendency, and variability within the study sample. The frequency of each response was calculated and examined for trends. The relationship between the perceived clinical importance of US and the frequency of US use for each of the 6 impairments was analyzed using the Spearman rho correlation coefficient. We expected to find that respondents who believe US is clinically important would use it more frequently. Six separate correlations were performed. Therefore, the Bonferroni correction factor was used to calculate the level of significance, as protection against a type I error. Using this correction factor, the significance level was established at P<.008.29

The temporal average intensity (TAI) was calculated as the product of the duty cycle and average pulse intensity (in watts per square centimeter) that the respondent reported using for each of the impairments. This calculation reflects the average intensity of the US beam relative to the duty cycle. This study did not examine the total amount of US energy delivered in relationship to the treatment time or size of the sound head.

Results

Respondents who reported using US for at least 25% of their patients (choosing any 1 of 4 survey responses: “for about 25% of my patients,” “for about 50% of my patients,” “for about 75% of my patients,” or “for more than 90% of my patients”) were categorized as “likely to use US.” Respondents who reported using US “with less than 10% of my patients” were categorized as “unlikely to use US.” Table 1 displays aggregated frequency counts for the categories “likely to use US” and “unlikely to use US.” In this study, 83.6% of the respondents indicated they were likely to use US to decrease soft tissue inflammation, 70.9% to increase tissue extensibility, 68.8% to enhance scar tissue remodeling, 52.5% to increase soft tissue healing, 49.3% to decrease pain, and 35.1% to decrease soft tissue swelling.

Table 1.

Response Frequency to the Survey Question “Indicate the Percentage of Patients With the Following Primary Impairments for Whom You Would Include US, With or Without Phonophoresis, as an Adjunctive Therapy”a

Additionally, respondents added 19 impairments under the category of “other.” The most frequent “other” conditions were muscle spasm (4 respondents), calcium deposits (3 respondents), and hematoma (3 respondents). The remaining 9 “other” conditions were each listed by 1 respondent and represented either a physiological response (increase cell permeability, increase blood flow, stimulate wound healing) or a pathology/injury (sprain, strain, joint capsule inflammation, plantar fasciitis, bone healing, temporomandibular disorder). There were too few conditions in any one “other” category for further analysis of these responses.

Aggregated frequency counts summarize respondents’ judgment about the clinical importance of US in managing each of the impairments addressed by the survey (Tab. 2). For each of the impairments, the responses “US is somewhat important,” “US is very important,” or “US is essential” were grouped together into the category “US is clinically important.” The responses “US is not important” and “US is minimally important” were grouped together into the category “US is not clinically important.” Table 2 also identifies the number of respondents who responded “I would not use US.” In this study, 71.1% of all respondents identified US as clinically important for the management of tissue extensibility, 62.6% for soft tissue inflammation, 53% for remodeling scar tissue, 47% for tissue healing, 39.4% for pain control, and 27.9% for decreasing soft tissue swelling. For each of the 6 impairments, a statistically significant and moderately strong Spearman rho correlation was found between “frequency of use of US” and “perceived clinical importance of US” (Tab. 3).

Table 2.

Response Frequency to the Survey Question “For Those Patients Whom You Do Treat With Ultrasound (US), How Clinically Important Do You Believe US Is in Achieving the Each of the Following Therapeutic Goals?”

Table 3.

Correlation Between the Frequency of Use of Ultrasound (US) and the Clinical Importance of US for Each Impairmenta

Spearman rho correlations also were performed to determine any potential relationship between year of initial physical therapy licensure and perceived clinical importance of US for managing each of the 6 impairments. Very weak, but statistically significant, correlations were identified for pain management (rs=−.24), tissue extensibility (rs=−.20), soft tissue inflammation (rs=.24), scar tissue management (rs=−.20), and soft tissue swelling (rs=−.20). Correlation coefficients (r values) less than .25 are generally interpreted as showing little or no relationship between the variables.29

Table 4 summarizes the frequency responses for preferred US parameters for each of the 6 impairments under review: duty cycle (10%, 20%, 50%, 100%), intensity, and frequency (1 MHz, 3 MHz). Respondents could choose “N/A” if they did not use US for the specific impairment. Less than 2.5% of respondents chose 10% pulsed US for any impairment; therefore, in Table 4, responses of “10%” and “20%” were combined to form the category “less than or equal to 20% duty cycle.” Continuous US (100% “on” duty cycle) was chosen almost exclusively when the goal was to increase tissue extensibility (93.6%, n=160). Continuous US also was the most frequently chosen pulse mode when the goal was to decrease pain (75%; n=105) or to remodel scar tissue (81.8%, n=130). A pulsed mode (either ≤20% or 50%) was chosen most frequently when the goal was to decrease soft tissue swelling (82.3%, n=79) and decrease soft tissue inflammation (70.5%, n=117).

Table 4.

Frequency Responses for Preferred Ultrasound (US) Parameters

Respondents identified the intensity setting they would use to achieve each therapeutic goal based on whether US was being applied to superficial or deep tissue. The intensities identified by respondents ranged from 0.10 W/cm2 to 3.30 W/cm2 (bimodal central tendency scores=1.00 W/cm2 and 1.50 W/cm2) for superficial tissues and from 0.40 W/cm2 to 4.00 W/cm2 (mode=1.50 W/cm2) for deep tissues. Table 5 displays the number of respondents who indicated they would use US to deliver medication (phonophoresis) for each of the 6 impairments reviewed.

Table 5.

Percentage of Respondents (N=207) Who Indicated They Would Use Ultrasound to Deliver Phonophoresis

From the parameters that reportedly would be used to achieve the 6 therapeutic goals, a TAI was calculated as the product of the duty cycle (expressed as a percentage) and the pulse average intensity. The mean TAI scores were highest for decreasing pain in deep tissues (1.58 W/cm2) and lowest for decreasing soft tissue swelling in superficial tissues (0.52 W/cm2). Respondents consistently used 3 MHz when treating superficial tissues and 1 MHz for deep tissues, regardless of the therapeutic goal.

Discussion

Use of Ultrasound

The frequency responses for likelihood of using US for each of the 6 impairments clustered into 3 general ranges. In the high range, at least two thirds of respondents indicated they would use US for soft tissue inflammation (83.6%), tissue extensibility (70.9%), and scar tissue remodeling (68.8%). Two impairments clustered in the middle range with frequency counts fairly evenly divided between respondents who would use US versus those who would not use US: pain management (49.3% would use US) and tissue healing (52.5% would use US). One impairment, soft tissue swelling, fell in the lower range, with only 35.1% of respondents indicating that they would use US for this condition.

About half of the respondents (54.1%) reported they would use US to deliver medication via phonophoresis for soft tissue inflammation, 22.2% of respondents would use phonophoresis for pain management, and 19.8% of respondents would use phonophoresis for soft tissue swelling. We did not anticipate high use of phonophoresis and did not include any survey items to further delineate medication preferences.

In providing insights into changes in the use of US over time, the findings of this study can only be indirectly compared to the 1988 study by Robinson and Snyder-Mackler,4 which is the next most recent study of US use in the United States. Differences in the characteristics of the respondents surveyed, the patient population addressed, and the specific questions asked to identify frequency of US use make direct comparisons impossible. Our study had a more narrow focus, targeting physical therapists who treated patients with orthopedic problems and asking respondents to estimate the percentage of patients they treat with US. In contrast, Robinson and Snyder-Mackler did not specify any particular group of conditions and quantified use by numbers of patients per week rather than percentage of patient caseload.

Similarities in outcomes, however, are noticeable and do not suggest any major change in the use of US over the last 19 years. In the study by Robinson and Mackler,4 45% of respondents indicated that they used US more than 10 times per week; 64% indicated that they used US 6 or more times per week. In our study, when scores across impairment categories were averaged together, approximately 60% of respondents indicated they were likely to use US, with a frequency count across specific impairment categories varying between 35.1% and 83.6%.

Over the past 10 years, researchers from Australia,1 Canada,5 and the Netherlands6 have examined US use in their countries. The specific nature of the questions differed somewhat among the studies. In both Canada and Australia, however, clinicians indicated that they used US at least once a day. This included 93.7% of private practice physical therapists in Alberta, Canada,5 and 84.7% of sports physical therapists in Australia.1 The Dutch study6 reported that physical therapists practicing in the Dutch primary health care system chose US 30% of the time as the primary intervention to address at least 1 of 4 treatment goals for their patients. Respondents could only identify 1 intervention as “primary” for each of 4 treatment goals. These studies from across the globe support the findings of our study. Ultrasound is a commonly used modality in physical therapist practice and is perceived to be important by clinicians for selected conditions.

Perceived Importance of US

We speculated that a high correlation between scores for the frequency of use of US and beliefs about the clinical importance of US existed. Indeed, statistically significant and moderately strong correlations were identified for each of the impairment categories. Respondents who believed US was clinically important were more likely to use US than those who did not believe US was important. We did not ask respondents to provide any justification for their opinion about the importance of US in the management of their patients. This is a notable question that was beyond the scope of this study. Future examination of this topic could provide insights to guide further research.

It would be appropriate to determine whether the impressions of the respondents were shaped primarily by their reflective judgments about the clinical outcomes they have observed in their patients, by their interpretation of the current literature, or by their personal comfort with this well-established and popular modality. Were their decisions primarily pragmatic based on availability and ease of use of US compared with alternative treatments? Do their patients request US? Is US typically reimbursable with adequate justification of need, whereas alternative therapies may not be? These are a few of the questions that could help qualify responses of those surveyed.

The respondents in our study had been licensed physical therapists for an average of 17 years (SD=7.4) and averaged 5 years as an OCS. We speculated that those who entered clinical practice at a time when the emphasis on evidence-based practice was less well established might consider US more clinically important when compared with more recent graduates. For each impairment category, therefore, a correlation was performed comparing the date of initial licensure as a physical therapist and respondent opinion of the importance of US. We found a very weak to absent relationship between these variables with rs values less than .25 for each category. We concluded, therefore, that, in this group of orthopaedic clinical specialists, the length of time since initial licensure as a physical therapist did not substantively influence respondent opinion of the importance of US in clinical practice.

Future Research Needs

There remains much controversy over the appropriateness of US as an adjunct modality in physical therapy. The biophysical basis of its use, particularly the nonthermal effects, has become controversial,30 and there are very few controlled trials that have found US to be clinically effective. Most systematic reviews of the topic conclude that there are very few clinical trials to either support or refute the benefit of US.1323 If physical therapists base their decision to use US primarily on clear demonstration of effectiveness in the scientific literature, then they are likely to stop using US based on lack of supporting evidence. However, against this near void of clinically applicable research, we found experienced and advanced-practice clinicians continuing to use US regularly for specific impairments often encountered in orthopedic settings, and indicating that US has an important role in managing selected impairments. In 2001, Robertson and Baker3 called for high-quality clinical trials to address this concern and help end this confusion. To date, very few clinical trials of this nature have been completed. Our study provides insights into how advanced practice clinicians are using US to manage musculoskeletal conditions. This information should help guide researchers in identifying key conditions to target for future clinical trials.

Strengths and Limitations of the Study

The strength of the design of this survey was its clarity, the ability for respondents to complete the survey quickly, and the variety of impairments addressed. This format also served as a limitation of the study. The survey was organized around impairments, not specific clinical scenarios. The use of clinical case scenarios (eg, describing a typical patient with lateral epicondylitis) would have provided greater detail from which to ground clinical decisions about US use and specific machine parameters. This, however, would have required us to present a detailed scenario for each of the impairments assessed and would have made the survey unacceptably long and tedious to complete.

This study sampled only physical therapists practicing in the Northeast and Mid-Atlantic region of the United States. Regional differences across the United States may be present and, by the nature of our sample, were not captured.

We also limited the number of US parameters to be considered. This study did not examine respondent opinions about the size of the treatment area, size of the sound head, or treatment time. Thus, estimates of the total amount of US energy delivered could not be calculated. We did not seek opinions about the number and frequency of treatment sessions. Each of these parameters has been identified in the literature as being potentially important to the effectiveness of US.10,27,31 We limited the investigation to the most fundamental parameters in order to keep the survey simple and time efficient. The specific size of the treatment area, size of the sound head's effective radiating area, and treatment time are all interconnected concepts. Including these parameters in the survey would have provided more definitive information but would have required organizing the survey around patient case scenarios. Indeed, 4 respondents did not fully complete the parameters section, commenting that they needed more information about the patients in order to make a decision.

This study did not ask respondents to confirm actual use of US through documentation such as a review of prior treatment logs or by maintaining a prospective treatment log. Rather, respondents simply provided their best judgment at one particular point in time. There may be differences between their perception of their own behavior and their actual behavior. We also chose not to inquire about the number of treatment sessions respondents typically administered for each incident of care. We believed that the influence of insurance coverage would complicate the interpretation of responses. Without adding questions to the survey, it would be difficult to determine whether responses about the number of treatment sessions represented the physical therapist's view of the ideal number of treatment sessions or a less than ideal number of treatment sessions approved by the third-party payer. Although this is an important consideration, we believed answering this question was best left to future research.

Conclusion

Our study demonstrates that physical therapists with the OCS designation practicing in the Northeast and Mid-Atlantic region of the United States regularly use US and believe US is clinically important for managing selected musculoskeletal impairments. In this study, the 3 most common impairments that US was used to manage were soft tissue inflammation (83.6%), tissue extensibility (70.9%), and scar tissue remodeling (68.8%). Similarly, 71.1% of respondents identified US as clinically important for managing tissue extensibility, 62.6% for soft tissue inflammation, and 53% for remodeling scar tissue. More than half of respondents indicated they use US to deliver medication (phonophoresis) for soft tissue inflammation. These findings support the need to further investigate the underlying clinical decision-making factors that contribute to the use of US by physical therapists and to engage in research that helps answer critical questions about the clinical effectiveness of US.

Footnotes

  • All authors provided concept/idea/research design, writing, and data collection and analysis. Dr Wong provided project management.

  • This study was approved by the Marymount University Institutional Review Board for the Use of Human Subjects in Research.

  • * SPSS Inc, 233 S Wacker Dr, Chicago, IL 60606.

  • Received December 19, 2005.
  • Accepted March 15, 2007.

References

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