Musculoskeletal medicine is an evolving field with new treatments and technology in constant development. For the last two decades, musculoskeletal ultrasound has become much more integral in both diagnosis and treatment. Currently, there is considerable variation in the quality and experience of resident education across US residency programs regarding both ultrasound and procedural training.1 Because of this variation, it is possible that the first time a resident will perform an ultrasound-guided (USG) procedure will be during a real patient encounter. Surveys have shown that most musculoskeletal ultrasound education is performed in outpatient clinics.1 It is hypothesized that this can lead to adverse outcomes including poor results, patient dissatisfaction, and discouraged resident physicians.
Previous literature regarding resident education of USG procedures is minimal and based on interventional radiology, regional pain, and trauma/intensive care applications.2–5 The goal of this study was to develop a low-cost, simplistic educational tool to improve procedural exposure and resident learning of USG procedures. It was theorized that residents would report improved experience, comfort, and performance with USG procedures after receiving a short lecture regarding fundamentals of ultrasound and using our practice model.
Models were constructed using a rectangular mold. Agar powder and black food dye were dissolved in simmering water and then poured into the mold to a height of 1 centimeter. This was allowed to harden; then, one chicken leg and two cherry tomatoes were placed on this hardened layer and covered in more liquid agar solution. This was allowed to harden into a firm block with the chicken and tomatoes encased (Fig. 1). The chicken was used to simulate muscle and tendon, whereas tomatoes simulated blood vessels. Black food dye was used to remove visual cues forcing participants to rely solely on USG (Fig. 1).
Eleven physiatry residents volunteered as subjects and completed a questionnaire about their experience and comfort with USG procedures. In phase 1, subjects were instructed to use ultrasound to identify two “circular structures” (tomatoes) and one “tendon-like structure” (chicken tendon) (Fig. 1). They were then instructed to use the needle to access the circular structure. Thereafter, participants were instructed to avoid the circular structures while performing a percutaneous needle tenotomy of the tendon-like structure (Fig. 1C). The previously mentioned tasks were timed and no feedback or guidance was provided. The tasks were graded by the first author as either completed or not completed. All stations were timed from start to when the participant stated that they had completed the task. All subjects were then given a short lecture on the fundamentals of USG procedures and percutaneous needle tenotomy, serving as the intervention. This lecture was developed by the authors who at the time of development were a post graduate year 3 resident in physical medicine and rehabilitation, a sports and spine fellow, and a pain boarded physiatrist. Participants then entered phase 2, performing the same tasks and completing the questionnaire again. The tasks were again graded and timed by the lead author as previously mentioned. The subjective questions in the questionnaire were designed in a Likert-type scale ranging from 1 indicating “strongly disagree” to 5 indicating “strongly agree” (presurvey and postsurvey, Supplemental Digital Contents 1 and 2, http://links.lww.com/PHM/A832, http://links.lww.com/PHM/A833). Preintervention and postintervention variables were compared using paired t test for statistical analysis of collected data. The surveys can be viewed online as supplemental digital content.
Resident ability to use ultrasound to identify the three structures fixed in the agar significantly improved from an average of 1.45/3 structures before intervention to 2.54/3 structures after intervention (P = 0.003). Similarly, the time spent to complete the task of accessing the “circular structure” improved from 394 to 258 secs (P = 0.04). Participants expressed an increase in comfort level performing USG procedures from 1.82/5 to 2.73/5 (P = 0.005) and an increased familiarity with percutaneous tenotomy procedures from 2.27/5 to 4.09/5 (P = 0.00004) on a five-point Likert scale (Table 1).
After reviewing the literature, no articles were found that discuss phantoms designed for musculoskeletal application, including tendon procedures. Through trials of previously described phantoms, which included tofu, jello, chicken legs, and pig legs, the authors developed the phantom described, comprising the ideal aspects of previous phantoms with added features, which best simulated USG musculoskeletal procedures.3 Other simulators were tested and proved to be less realistic and unable to sustain multiple needle sticks without losing their form. The agar allowed researchers to mimic subcutaneous tissue and suspend strusctures in space.
This study demonstrates that USG procedural skills can be improved by using this easily prepared, low-cost, homemade practice model. Similar improvements were found compared with what has been described in previous literature regarding USG procedural practice using other more expensive phantoms.3 The low-cost model, which is more applicable for tendon procedures than commercially available phantoms ranging from $500 to $1500, allows for practice in a completely controlled environment with no pressures, such as time or patient satisfaction.6,7 A number of mock procedures can be practiced on one mold before it is destroyed. In addition, the model can be used by learners at any stage of their careers, including mid-career physicians who are trying to integrate USG procedures into their practices. What makes this model different from previous designs is that the targets are not visible to the naked eye and that targets can be customized for each type of procedure as desired.4
This study had several limitations. We chose to use the same design of phantom for the pretest and posttest evaluation. This was done to limit confounding variables but provides a limitation because participant improvement may be related to comfort with the model. However, the participants received no feedback on how they performed in stage 1 of testing and therefore any improvement one would believe was secondary to the lecture provided and repeated use of ultrasounds. Another limitation of this model is the inability to practice palpation of anatomic structures when performing USG procedures on patients. Although the agar remains firm and does not melt at room temperature, food products, such as raw chicken, require refrigeration and can present sanitary challenges. The low number of participants limits the power of this study.
Residents demonstrated improved comfort and ability in USG procedural skills when using this low-cost, customizable, homemade model. Further study may focus on development of models for other kinds of musculoskeletal USG procedures. Residents and attending physicians desiring practice in USG procedures who may not have access to cadavers or expensive phantoms now have an easily accessible and cost-effective model for training.
1. Siddiqui IJ, Luz J, Borg-Stein J, et al.: The current state of musculoskeletal ultrasound education in physical medicine and rehabilitation residency programs. PM R
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3. Farjad Sultan S, Shorten G, Iohom G: Simulators for training in ultrasound guided procedures. Med Ultrason
4. Liu Y, Glass NL, Glover CD, et al.: Comparison of the development of performance skills in ultrasound-guided regional anesthesia simulations with different phantom models. Simul Healthc
5. Mendiratta-Lala M, Williams T, de Quadros N, et al.: The use of a simulation center to improve resident proficiency in performing ultrasound-guided procedures. Acad Radiol
6. Ultrasound trainers. SynDaver Labs. 2017. Available at: http://syndaver.com/product-category/synatomy/ultrasound-trainers/
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7. CAE Healthcare: realistic & durable ultrasound training models. Blue Phantom, Blue Sky Projects, 2018. Available at: http://www.bluephantom.com/category/By-Phantom-Type_Select-Series-Models.aspx
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