Bedside Ultrasound for the Detection of Soft Tissue Foreign Bodies: A Cadaveric Study

doi:10.1016/j.jemermed.2007.10.071

The Journal of Emergency Medicine

Volume 36, Issue 4, May 2009, Pages 377-380

https://doi.org/10.1016/j.jemermed.2007.10.071 Get rights and content

Abstract

The objective of this study was to evaluate the sensitivity and specificity of bedside ultrasound, as performed by emergency physicians with typical equipment, in detecting small, soft tissue foreign bodies, using a cadaveric model. This was a prospective study, using 6 unembalmed human cadavers and 6 ultrasound-credentialed, emergency medicine residency-trained physicians as sonographers. Incisions were made in 150 total sites of the extremities and each site was randomly assigned one of five groups: wood, metal, plastic, glass, or no foreign body. All foreign bodies were 2.5 mm³ in total volume or less, no longer than 5 mm in any dimension, and inserted to a depth of up to 3 cm. Ultrasound was performed with a SonoSite TITAN^® (SonoSite, Inc., Bothell, WA) ultrasound system using a L38/10-5 broadband linear array transducer. Sonographers were blinded to the number, type, and location of foreign bodies. A total of 900 ultrasound examinations were recorded. Overall sensitivity of ultrasound for foreign body detection was 52.6% (95% confidence interval [CI] 48.9%–56.2%), and overall specificity was 47.2% (95% CI 39.9%–54.5%). Positive predictive value was 79.9% (95% CI 76.3%–83.5%), and negative predictive value was 20.0% (95% CI 16.2%–23.7%). Sensitivity for individual sonographers ranged from 40.8% to 72.3% (average 52.6% ± 13.3%), and specificity ranged from 30% to 66.7% (average 47.2% ± 15.1%). Inter-observer reliability was poor. In our model, bedside ultrasound performed by emergency physicians was neither sensitive nor specific for the presence of small soft tissue foreign bodies.

Introduction

Ultrasound (US) has gained increasing favor in the Emergency Department (ED) over the past decade and has been employed in a myriad of clinical diagnostic and procedural applications (1). Multiple studies have been performed to determine the utility of US in excluding or identifying soft tissue foreign bodies (FB) (2, 3, 4, 5). These studies achieved mixed results. Many physicians are using US as an adjunct to careful wound exploration and plain radiography for excluding soft tissue FB in appropriate settings. However, the reliability of ultrasound for this purpose is still the subject of debate. If ultrasound were demonstrated to be highly sensitive for the detection of foreign bodies, it could replace more expensive and time-consuming radiographic techniques such as computed tomography. It could also be used in out-of-hospital settings where other imaging techniques are impractical or unavailable.

Our goal was to determine whether ultrasound examinations, done by emergency physicians (EPs) with standard equipment, are sensitive and specific for the detection of small soft tissue foreign bodies, the likes of which might be missed on physical examination of a traumatic wound. For our experimental model, we chose human cadaveric tissue as the medium, ultrasound equipment commonly used in EDs, and four types of small, radiopaque and radiolucent foreign bodies. To our knowledge, this is the largest study of its type to date. If proven reliable, ultrasound might be the method of choice to decrease the incidence of unidentified FB in wounds (4, 6, 7).

Section snippets

Study Design

This was a prospective, cadaveric study. The study was approved by the Institutional Review Board of the sponsoring institution in an expedited review.

Study Setting and Population

The six sonographers in this study were all ultrasound-credentialed, EM residency-trained physicians, practicing at a 65,000-visits-per-year community hospital ED, where ultrasound is used widely for all typical EM applications. All physicians had attended a 2-day local ultrasound course given at the beginning of their tenure at the hospital, and

Results

A total of 900 ultrasound examinations were recorded. The overall sensitivity of ultrasound for detection of a foreign body was 52.6% (95% confidence interval [CI] 48.9%–56.2%), and overall specificity was 47.2% (95% CI 39.9%–54.5%). The positive predictive value was 79.9% (95% CI 76.3%–83.5%), and the negative predictive value was 20.0% (95% CI 16.2%–23.7%). Positive and negative likelihood ratios were 1.00 (95% CI 0.81–1.24) and 1.00 (95% CI 1.28–0.80), respectively. Sensitivity for the

Discussion

Some previous studies demonstrated high sensitivity and specificity of ultrasound for detection of FB in soft tissue; three have shown overall sensitivities > 89% and overall specificities > 93% (2, 3, 5). Similarly to these studies, our study employed a cadaveric model, utilized comparable transducers, and used multiple sites in the same model. However, procedural differences in our study included the training of the sonographers, their primary practice specialty, type of cadaveric model,

Limitations

There are several limitations of our methodology. As soft tissue ultrasound by EPs is a relatively new consideration, the training these physicians received may not have included an appropriate depth of instruction in evaluating soft tissue. Our model, like any experimental model, may not have optimally represented live human tissue, and we may have portrayed US in an excessively negative light due to any of the parts of our model, as described above. Neglecting the above, our findings may

Conclusions

In our cadaveric model, bedside US by EPs without intensive training, and using standard equipment, seems to be neither sensitive nor specific for the detection of small soft tissue foreign bodies. Within the limitations of our study, our findings may contradict some previous results. Further study is indicated.

References (8)

E. Legome et al.
Future applications for emergency ultrasound
Emerg Med Clin North Am
(2004)
P.W. Bray et al.
Sensitivity and specificity of ultrasound in the diagnosis of foreign bodies in the hand
J Hand Surg [Am]
(1995)
R. Hill et al.
Ultrasound for the detection of foreign bodies in human tissue
Ann Emerg Med
(1997)
R.L. Lammers
Soft tissue foreign bodies
Ann Emerg Med
(1988)

There are more references available in the full text version of this article.

Cited by (31)

Nail Puncture Wound Through a Rubber-Soled Shoe: Should We Take Every Patient to the Operating Room?
2022, Journal of Foot and Ankle Surgery
Citation Excerpt :
The small size of rubber pieces makes this task even more challenging, resulting in very low rates of detection. To support this conclusion, we may also look at the cadaveric study by Crystal et al who inserted very small radiolucent pieces (volume up to 2.5 mm3) into cadaveric limbs, although not including feet (14). The reported US sensitivity of 52.6% and specificity of 47.2% in detection of these small foreign bodies.
Nail puncture wounds through rubber-soled shoes, when presenting acutely, have a deceivingly benign appearance. High index of suspicion for a retained rubber piece should be maintained by the physician. This study investigates whether preoperative ultrasound examination can rule out a foreign body and reduce the need for surgery. It is a retrospective cohort of 125 patients with deep nail puncture wounds through a rubber-soled shoe, who underwent surgical exploration between 2008 and 2018. All patients had a preoperative ultrasound examination for detection of a rubber foreign body. The patients’ median age was 29, and 112 (89.6%) were males. Median time of presentation was 1 day, but there were patients who presented up to 90 days after injury (mean 5.1 ± 15.6 days). Foreign bodies, ranging 1 to 4 mm in diameter, were surgically removed in 37 (29.6%) patients. Only 16 of these patients had a positive preoperative ultrasound examination, corresponding to sensitivity of 43.2%. Specificity of the ultrasound examination was 95%. Ultrasound examination has low sensitivity for detection of foreign bodies following a puncture wound of the foot. This is attributable to the small size of the foreign bodies in this scenario and to the complexity of sonography in this location. We conclude that ultrasound cannot be used to rule out foreign body in the foot, and should not be relied on when deciding to avoid surgery. Nevertheless, it can be a helpful adjunct preoperatively, as an assessment of the foreign body size and location.
Detectability of foreign body materials using X-ray, computed tomography and magnetic resonance imaging: A phantom study
2021, European Journal of Radiology
To evaluate the effectiveness of plain radiography (X-ray. XR), computed tomography (CT) and magnetic resonance imaging (MR) in visualising commonly seen foreign bodies. A special focus was put on objects relevant to head and neck surgery.
Thirty-four commonly encountered objects of different compositions including wood, plastic, and glass were embedded in a gelatin gel phantom and imaged using XR, CT and MR. The success rates of radiologists in detecting and correctly identifying the foreign objects were evaluated. Subjective visibility was rated on a 4-point Likert scale. Objective visibility was analysed using region of interest-based contrast for CT.
Sensitivity in foreign bodies detection was highest in MR (97.1 %) followed by CT (86.0 %) and x-ray (61.8 %). Success rates for the correct identification of the objects and material types were highest in MR (33.3 % and 39.2 %, respectively) followed by CT (25.5 % for both) and XR (16.7 % and 15.7 %). Overall, subjective visibility was rated higher in CT and MR imaging (“good visibility”), as compared to XR (“poor visibility”). Interreader agreement was high across modalities (Kendall’s W = 0.935, 0.834 and 0.794 for XR, MR and CT, respectively).
Detection and identification of non-ferromagnetic objects was most successful in MR followed by CT imaging in this experimental setup.
Musculoskeletal Ultrasound in the Emergency Department: Is There a Role?
2021, Seminars in Roentgenology
Ultrasound (US) is gaining wider acceptance for the diagnosis of musculoskeletal pathology by both radiologist and non-radiologist clinicians in urgent or emergent settings. Part of the growth of US can be attributed to its portability, relative low cost compared to other imaging modalities, lack of radiation, and the capacity to make a rapid diagnosis in experienced hands. Bedside US enables faster decision making and expedited patient care. As training programs further integrate musculoskeletal US into their diagnostic imaging education, US utilization and breadth of application will only increase. This paper highlights some of the benefits, applications, and potential pitfalls of the sonographic diagnosis of common urgent musculoskeletal conditions that present to the emergency department.
Ultrasound for the evaluation of soft tissue foreign bodies before and after the addition of fluid to the surrounding interstitial space in a cadaveric model
2016, American Journal of Emergency Medicine
Citation Excerpt :
There was no statistically significant difference found between the preinjection and postinjection sonographic evaluations (P = .08; 95% CI, − 0.04 to 0.01). Previous studies of point-of-care sonographic detection of FBs have been in deceased animal tissue (e.g., chicken legs) [6] or human cadaveric tissue [7,8] with varying results. Orlinsky et al [6] implanted wooden toothpicks in 104 chicken thighs.
Point-of-care ultrasound may be used to facilitate foreign body (FB) localization and removal. We hypothesized that injection of normal saline adjacent to an FB may make it easier to detect.
The study was performed on one embalmed human cadaver. Potential FB sites were created of wood (24), metal (24), and null (24). Two sonographers evaluated each of the 72 sites both before and after a 25-gauge needle was inserted into each incision and 3 cc of normal saline was injected. Accuracy, sensitivity, and specificity were calculated both before and after injection of normal saline. Binomial tests were used to determine the statistical significance of FB detection before and after injection. A 2-tailed Student's t test was used to determine if there was a statistically significant difference between the 2 methods.
Preinjection, 116 (81%) of the 144 interpretations (P ≤ .001) were correct in their assessment of whether or not an FB was present, with a sensitivity of 81% (95% confidence interval [CI], 72%-88%) and a specificity of 79% (95% CI, 65%-90%). Postinjection, 119 (83%) of these 144 interpretations (P ≤ .001) were correct in their assessment of whether or not an FB was present, with a sensitivity of 85% (95% CI, 77%-92%) and a specificity of 77% (95% CI, 63%-88%). This difference was not significant (P = .08; 95% CI, − 0.04 to 0.01).
Ultrasound was reasonably accurate, sensitive, and specific in identifying 1-cm metal and wood FBs. Although accuracy and sensitivity did improve after normal saline injection, this difference was not significant.
Migrating sternal rod: Ultrasound identification of an unusual soft tissue foreign body
2014, Journal of Emergency Medicine
Citation Excerpt :
Plain radiographs perform excellently in the identification of metallic objects, with 100% sensitivity (11). Although ultrasonography has similar sensitivity (92%) for detecting radiopaque foreign bodies, its ability to detect radiolucent foreign bodies is variable, with reported sensitivities ranging from 53% to 90% (12–15). ED bedside ultrasound provides several advantages in the detection of soft tissue foreign bodies.
Sternal hardware migration from its original site of implantation is a rare entity. Bedside ultrasound may identify migrated hardware if the site of migration is the subcutaneous tissue.
This case report will discuss the unusual phenomenon of migrating sternal hardware, as well as the ultrasonographic characteristics of soft tissue foreign bodies.
A 51-year-old man presented to the Emergency Department with a 2-month history of intermittent lower abdominal pain, 11 months status post bilateral lung transplant surgery. His examination was remarkable for a palpable mass over the left lower quadrant of the abdomen. Initial bedside ultrasound identified a soft tissue foreign body in the subcutaneous tissue overlying the left lower quadrant of the abdomen. Further evaluation using plain radiography and computed tomography ultimately diagnosed the foreign body as a metal rod, which had migrated from his sternum. The sternal rod was removed at the bedside, and he was discharged the next day without any complications.
Sternal hardware migration is uncommon, but in patients who have undergone surgery involving sternal fixation, this diagnosis should be considered as a cause for unusual symptoms.
Use of cadaver models in point-of-care emergency ultrasound education for diagnostic applications
2012, Journal of Emergency Medicine
Citation Excerpt :
Delaunoy et al. and Hong et al. demonstrated that injecting normal saline into cadaver joints provided a model to detect joint effusion in knees (11,12). Additionally, studies have shown that cadaver models are useful in answering important clinical questions such as the sensitivity of US to localize small soft-tissue foreign bodies and the ability of US to confirm endotracheal tube placement and intraosseous needle placement (13,14,18). As in previous studies, our study demonstrated that qualitatively, freshly frozen cadavers can be effective models for joint effusion.
As the use of bedside emergency ultrasound (US) increases, so does the need for effective US education.
To determine 1) what pathology can be reliably simulated and identified by US in human cadavers, and 2) feasibility of using cadavers to improve the comfort of emergency medicine (EM) residents with specific US applications.
This descriptive, cross-sectional survey study assessed utility of cadaver simulation to train EM residents in diagnostic US. First, the following pathologies were simulated in a cadaver: orbital foreign body (FB), retrobulbar (RB) hematoma, bone fracture, joint effusion, and pleural effusion. Second, we assessed residents’ change in comfort level with US after using this cadaver model. Residents were surveyed regarding their comfort level with various US applications. After brief didactic sessions on the study’s US applications, participants attempted to identify the simulated pathology using US. A post-lab survey assessed for change in comfort level after the training.
Orbital FB, RB hematoma, bone fracture, joint effusion, and pleural effusion were readily modeled in a cadaver in ways typical of a live patient. Twenty-two residents completed the pre- and post-lab surveys. After training with cadavers, residents’ comfort improved significantly for orbital FB and RB hematoma (mean increase 1.6, p < 0.001), bone fracture (mean increase 2.12, p < 0.001), and joint effusion (1.6, p < 0.001); 100% of residents reported that they found US education using cadavers helpful.
Cadavers can simulate orbital FB, RB hematoma, bone fracture, joint effusion, and pleural effusion, and in our center improved the comfort of residents in identifying all but pleural effusion.

View all citing articles on Scopus

: The views expressed in this article are those of the authors, and do not necessarily reflect those of the U.S. Army or Department of Defense.

¹: Current affiliation: Division of Emergency Medicine, Legacy Good Samaritan Hospital, Portland, Oregon.

View full text

Ultrasound in emergency medicineBedside Ultrasound for the Detection of Soft Tissue Foreign Bodies: A Cadaveric Study