Ultrasonography in assessing suspected bone fractures: a cross-sectional survey amongst German general practitioners

Background Over the last two decades, ultrasonography (US) has been shown to be an accurate tool for the diagnosis of suspected bone fractures; however, the integration of this application of US into routine care and outpatient settings needs to be explored. In this study, we surveyed German general practitioners (GPs) to assess their knowledge, attitudes, and utilization of US for the diagnosis of suspected fractures. Methods Notification of the study, a self-designed questionnaire, and a reminder were mailed to 600 randomly selected GPs in Saxony and Saxony-Anhalt. Results The response rate was 47.7% (n = 286), and respondents did not differ from the population of all GPs in respect to sex and practice type. Among GPs surveyed, 48.6% used an US device in their practice. On average, GPs diagnosed six patients with suspected fractures per month, yet only 39.3% knew about the possibility of ultrasonographic fracture diagnosis, and only 4.3% of GPs using US applied it for this purpose. Among participants, 71.9% believed that US is inferior to conventional X-rays for the diagnosis of bony injuries. Users of US were better informed of and more commonly used US for fracture diagnosis compared to non-users. Conclusion The need to rule out possible fractures frequently arises in general practice, and US devices are broadly available. Further efforts are needed to improve the knowledge and attitudes of GPs regarding the accuracy of US for fracture diagnosis. Multicenter controlled trials could explore the safety, usefulness, and effectiveness of this still seldom used diagnostic approach for suspected fractures.

GPs in Germany and 67% in Greenland use US [10]. Heidemann et al. [2] reported that ultrasound devices were available for about 70% of German GPs, although they found lower availability of US devices (32.1% of all GPs) for the area of former East Germany.
The vast majority of published studies on US-guided fracture diagnosis refer to observations in emergency departments [4], while very few studies report on outpatient settings [11,12].
The aim of this exploratory study was to describe the utilization of US, knowledge and attitudes towards fracture diagnosis based on US, and referral behavior dealing with suspected fractures among German GPs. Differences between physicians using or not using US as a diagnostic tool and between GPs with long or short driving distances to the nearest radiographic unit were also investigated.

Sampling and design
We performed a cross-sectional survey of GPs from the federal states Saxony (n = 2733) and Saxony-Anhalt (n = 1445). Addresses were gained from publicly accessible registers, and the contacted GPs were selected from the register using random numbers (n = 400 Saxony, n = 200 Saxony-Anhalt). A response rate of about 25% was expected. Selected GPs first received a mailed notification of the study, which was followed by a mailed questionnaire one week later. A reminder was mailed seven weeks after sending the questionnaire. Responses could be returned by fax or mail.
We received further pooled sociodemographic data of all GPs in Saxony and Saxony-Anhalt from the Associations of Statutory Health Insurance Physicians (Kassenärztliche Vereinigung), including average age, sex, and registration for reimbursement of US diagnostics.

Questionnaire
The questionnaire was entirely self-designed by the research team, which included two social scientists, a medical student, and two experienced GPs who provided content-related input. A four-point scale was used for all questions regarding attitudes or personal assessments. To ensure face validity, the questionnaire was pre-tested among two groups of six GPs respectively, followed by additional feedback discussions. After minor revisions, the questionnaire was considered feasible by pre-testing physicians and could be completed in five minutes (Additional file 1: Questionnaire translated to English). The diagnostic scores and tools mentioned in the final question of the questionnaire were compiled through an unsystematic literature search.

Statistical analyses
Data was analyzed using SPSS 25 (IBM SPSS Inc., Chicago, USA). Sociodemographic characteristics of the sample were presented descriptively (means, standard deviation, relative and absolute frequencies). Users and non-users of US were compared in bivariate cross tabulations regarding their knowledge and attitude towards US (relative and absolute frequencies). These differences were tested for statistical significance using chi-square tests (with Fisher-Exact correction as necessary). Further characteristics (e.g., suspected fractures after trauma, referring patients with suspected fractures) were analyzed using univariate statistics. The criterion of statistical significance has been set to an error probability of p < 0.05.
Because of the small sample size, the inference statistics omit a correction for serial testing and are, therefore, exploratory.

Ethics approval and consent to participate
According to the Model Professional Code for Physicians [13], an explicit ethics approval was deemed unnecessary for this study because no personal data of patients was collected. GPs were informed in writing about the use and publication of their anonymized data, and participants voluntarily consented by returning a completed questionnaire.

Results
Of the 600 mailed questionnaires, 306 questionnaires were returned (51.0%), with 286 fully completed (47.7% response rate). Of the 286 completed questionnaires, 61 responses (21.3%) were received after a mailed reminder. A non-responder analysis showed no differences between responding GPs and non-responders with regard to sex, academic title, and specialization.
Sociodemographic data of the surveyed sample is given in Table 1. The study sample and the total population of GPs in Saxony and Saxony-Anhalt did not differ significantly in respect to sex and type of practice. There were no differences in the availability of US devices between urban or rural areas (major cities: 55.8% (n = 43/77); small towns: 54.7% (n = 64/117); rural areas: 58.3% (n = 49/84); p = 0.876). The GPs using US reported performing on average 17 (mean = 16.7; median = 10; right-skewed distribution) examinations per week. The most frequently examined structures were the abdomen, the thyroid gland, and the kidneys (including the urinary passages). Only 4.3% (n = 6/138) of GPs using US stated that they regularly used US for the imaging of bone structures.

Knowledge and beliefs
The beliefs and attitudes regarding the use of US for suspected fractures among GPs are summarized in Figure 1. The majority of respondents (71.9%, n = 192/267) believed that US is inferior to conventional X-rays for diagnosing bone injuries. or other clinical decision tools as "rather relevant" or "relevant".
The GPs were asked whether they would refer patients with suspected fractures and if so, to which specialty. The answers are summarized in Figure 2. GPs from major cities were more likely to refer their patients to a radiologist than their colleagues from small towns or rural areas, whereas there was no statistically significant difference between referrals made to a surgeon or to the nearest emergency department ( Table 2). No significant differences in referral behavior between users and non-users of US were found. decided on further diagnostic procedures with patients or patients' relatives.

Influence of distance to radiological unit
GPs were asked if their practices were located in rural areas, small towns, or a major city. GPs were also asked to estimate the driving minutes to the nearest outpatient surgery, radiological department or emergency department. The answers are summarized in Table 3. There were no correlations between the distances to the next surgeon, radiology, or emergency department and the use of US or referral behavior.

Discussion
In this study, we surveyed a random sample of GPs in Germany (Saxony and Saxony-Anhalt) regarding their knowledge, attitudes, and utilization of US for the diagnosis of suspected bone fractures. Although half of the responding doctors used US as diagnostic imaging modality in their daily routine, its accuracy and potential for detecting bone injuries were grossly underestimated. Around one-third of those surveyed knew that US can be used in fracture diagnosis. Yet, more than two-thirds of GPs believed US was inferior to conventional radiographs, and fewer than 8% had experience with ultrasonographic investigation of bone structures.
In a search of recent literature, we found no comparable studies examining the use of US for fracture diagnosis in general practice. Jacobs et al. [14] investigated the effect of the introduction of teleradiology on the number of performed radiographic examinations for suspected fractures in a remote general practice. The possibility of making a diagnosis by the GP reduced the number of unnecessary referrals to the hospital, and more patients with fractures were treated in the general practice rather than the hospital. A similar effect might be presumed for integrating US as an addition to the physical examination of suspected bone fractures.

Implications for future practice
We found that GPs regularly encounter suspected bone fractures, and half of all GPs own an US device. Further evaluation of US as a diagnostic tool for suspected fractures in general practice seems promising and possible.
For safe and cost-effective patient care, an accurate imaging modality to rule out suspected fractures is needed. Today, conventional radiographs are most frequently utilized to make a diagnosis [7]. Radiographs are widely available in Germany, as illustrated by our finding that 75% of the GPs from rural areas reported the closest radiology department to be reachable in less than 20 minutes driving by car.
Our findings show that 43% of GPs refer their patients to the radiology, even if a fracture seems unlikely. This finding suggests a demand for specific tools with a high negative predictive value to help rule out fractures with sufficient certainty.

Implications for future research
Potential benefits of utilizing US for the diagnosis of suspected fractures in general practice need to be carefully investigated. It remains to be seen whether fracture US in general practice can improve patients' safety and comfort in addition to reducing costs. The diagnostic process for suspected fractures with US should therefore be assessed in prospective multicenter studies. Further studies of test performance in general practice or other outpatient settings with a relatively low pre-test probability for fractures should also take into account organizational and financial aspects, safety, and practicability.

Strengths and limitations
To our knowledge, this study is the first to investigate the attitudes and beliefs of GPs toward US for fracture diagnosis.
However, this study has several limitations. The questionnaire was self-designed, and questions assessing the feelings and attitudes of GPs toward fracture diagnosis and the use of US for this purpose were not validated. This might limit the reliability of those results. Because of the cross-sectional design, we relied on estimates reported by GPs of the incidence of suspected fractures.
In addition to the actual use of US in the daily practice, it would have been interesting to assess how many GPs underwent an explicit training for US based fracture diagnosis.
The response rate achieved in our study was relatively high compared to similar recently published surveys among German GPs [21][22][23][24] and acceptable considering international findings [25]. Nonetheless, it was lower than 50%, and bias due to an overrepresentation of those GPs interested in the topic cannot be excluded.
Our sample may not be representative of all German GPs, as regional disparities in the presence of US devices in general practices across the federal states have been described [2]. However, it is possible that physicians who are routinely using US in their practice are overrepresented among respondents (US device available for 55.6% of the responding GPs vs. 32.1% as reported by Heidemann et al. [2]). These physicians may overestimate the potential and benefits of US for fracture diagnosis.
Yet, given these findings of low utilization and poor knowledge of US for suspected fractures, it is reasonable to assume the need for information and clear evidence in this field is even higher for the total GP population in Germany.

Conclusion
Ruling out suspected bone fractures is a frequent task in general practice, and US devices are available for half of the GPs in Germany. Further efforts are needed to improve the knowledge and attitudes of GPs regarding the accuracy of US for fracture diagnosis. Multicenter controlled trials could explore the safety, usefulness, and effectiveness of this still seldom used diagnostic approach for suspected fractures.

Ethics approval and consent to participate
According to the Model Professional Code for Physicians [13], an explicit ethics approval was deemed unnecessary for this study because no personal data of patients was collected. After being informed of the study, all participants completed this anonymous survey on a voluntary basis.

Consent for publication
The participating GPs were informed in writing about the use and publication of their anonymized data and consented by voluntarily returning the completed questionnaire. Availability of data and materials Anonymized survey responses obtained through this study are available from the corresponding author on reasonable request.

Competing interests
TF is an associate editor on the editorial board of BMC Family Practice. There are no further competing interests.

Funding
There were no sources of funding for this research.

Authors' contributions
GLS and BK designed the questionnaire, conducted the survey, read out and interpreted the results, and drafted and revised the manuscript. MH revised the questionnaire, analyzed the data, discussed the results critically, and iteratively revised the manuscript. TD designed and revised the questionnaire, helped with the statistical analysis of the data, discussed the results critically, and revised the manuscript several times. TF had the idea for the research question, designed and revised the questionnaire, discussed the results critically, and revised the manuscript multiple times. All authors read and approved the final manuscript.  Figure 1 Knowledge, beliefs, and attitudes toward US for the diagnosis of bone injuries of GPs who use The referral behavior of GPs for patients with suspected bone fractures is visualized for the c