Soft tissue foreign bodies: A training manual for sonographic diagnosis and guided removal

Abstract Sonography provides excellent detection, localization, and characterization of soft‐tissue foreign bodies. Ultrasound guided foreign body removal is a safe and highly successful minimally invasive procedure that facilitates effective treatment and avoidance of complications in patients with soft tissue foreign bodies. Focused laboratory training is critical to successful implementation of a sonographic foreign body management practice.


| INTRODUCTION
Ballistic foreign bodies (FB) in current combat scenarios, to include injuries sustained with improvised explosive devices (IED), consist of materials such as metal, ceramic, stone, wood, plastic, clothing, flesh, bone, or vegetable matter. Ballistic FB such as wood, plastic, clothing, flesh, or vegetable matter that are not visible with radiographic or fluoroscopic evaluation may be identified and removed with ultrasound guidance. [1][2][3][4][5][6] As a general rule, any soft-tissue FB requires removal when they High resolution sonography is an excellent imaging tool used for detection, localization and removal of nonradiopaque soft-tissue FB. [1][2][3][4] Radiopaque FB are frequently detected and grossly localized with plain radiographs. Sonography plays an expanding role in identification, characterization, and detailed three-dimensional (3D) localization with respect to vital neurovascular structures and tendons.
This training guide will focus on management of soft-tissue FB, including those in muscle, tendon, and intra-articular spaces and bony structures. Detection of soft-tissue FB is performed with the highest resolution sonographic transducers available. In the search for embedded FB, high frequency linear array transducers (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) are the most useful in detection of radiopaque and nonradiopaque FB, ranging in size from 0.5 to more than 10 mm in transverse dimension. Meticulous scanning is critical for detection, since minimally echogenic FB can be sonographically subtle and mistaken as a muscle fibril or fascial tissue plane. Other distractions may include gas, proteinaceous of echogenic fluid, or multiple small foreign bodies.
In the initial search process, FB are most easily detected when the sound beam strikes the object aligned with the FB longitudinal axis, delineating the full length of the FB. Frequently, initial sonography will strike in the transverse plane to the plane of the FB, defining small linear FB as more echogenic than surrounding soft tissues.
Once an FB is detected, it is important to maintain alignment of the sound beam with the long axis of the FB for conspicuity and definition. Caution is advised to the potential pitfall of the "oblique cross-cut" artifact created by scanning obliquely to the true long axis of the FB, foreshortening the appearance of the FB. The same concept of pitfall of oblique cross-cut artifact is applicable to accurate visualization of the forceps during FB removal (see Figure 1, which shows oblique crosscut artifact during forceps management; see Video S1, demonstrating oblique cross-cut artifact). Once fully defined, the operator can accurately localize the FB with respect to surrounding structures.
The response of surrounding tissues has diagnostic significance, as granulation tissue and pus purulent debris will create hypoechoic zones. [1][2][3][4] Longstanding inflammation surrounding a FB will produce a hypoechoic "halo" of granulation tissue, with vascular in-growth demonstrated with color Doppler sonography. If a surgeon or other physician has unsuccessfully attempted removal, there is often air in the surrounding soft tissues, limiting definition of the retained object immediately following surgical dissection. It is prudent to dress the wound and allow a few days to pass for air absorption, prior to repeat sonographic examination.

| Technical considerations
Interrogation of adjacent soft-tissues is essential for the pre- The optimal hand grasp and transducer movement is described as  The last forceps pitfall occurs when FB near joints are encountered. Blunt dissection is pursued but the tip of the foreign body cannot be contacted or grasped due to intra-articular positioning and the joint capsule is found interposed between the FB and the forceps.

| Pitfalls
Intra-articular foreign body removal can be successfully completed, entering the joint with ultrasound guided arthrotomy using a #11 scalpel blade under direct sonographic guidance.

| CONCLUSION
Ballistic and nonballistic injuries with embedded soft-tissue FB are challenging clinical dilemmas. This technique can also be used to remove implanted medical devices. Sonography provides excellent detection, localization, and characterization of soft-tissue foreign bodies. USFBR is a safe and highly successful minimally invasive procedure that facilitates effective treatment and avoidance of complications in patients with soft tissue foreign bodies. Focused hands on simulation training is critical to successful implementation of a sonographic foreign body management practice.
F I G U R E 4 Volume averaging artifact. A, Foreign body aligned with forceps with appearance of good alignment but no tactile sensation of grasp or successful removal. B. Oblique view of the incorrect alignment of the forceps and foreign body illustrating adjacent position of the forceps and foreign body allowing sonographic volume averaging artifact