Ultrasonography for detecting a hog bristle in a finger: a case report and literature review

Abstract

A 62 year-old hog butcher had a sharp pain in his right little finger while he was removing the hair from a white hog 1 month ago. He immediately sought help at a nearby emergency department (ED). His finger was cleaned, but doctors found nothing in his finger at that time. Because of frequent painful swelling in his finger, he sought treatment at many clinics. However, surgical exploration for a cause was negative, and the pain and tenderness did not improve. He then came to our ED with a painfully swollen right little finger. A physical examination showed a local tender spot on the radial side of the distal interphalangeal joint. We suspected that the patient had a foreign body in his finger; hence an ultrasonographic investigation was performed by an experienced orthopaedics ultrasonologist (T.C.C.). To detect and localise the foreign body, the suspected area was scanned. A hyperechoic foreign body without posterior acoustic shadowing, surrounded by a hypoechoic halo of inflammation was identified in the axial (transverse to the foreign body) and oblique (longitudinal to the foreign body) directions (Figure 1, right panels: green arrows). After the foreign body had been localised, an ink mark was made on the skin directly over it (Figure 2, upper panels). Care was taken to mark the skin nearest to the foreign body and on the proposed line of minimal incision for the exploration. The object's depth from the skin surface was measured using electronic callipers. Ultrasonograms were obtained using a real-time scanner (t3000TM; Terason, Burlington, MA) with a 5–12-MHz linear array transducer. We removed the foreign body, a tiny white pig bristle about 1 cm long (Figure 2, lower panel). A follow-up showed that the patient had rapidly recovered. Ultrasonography has proved to be an accurate non-invasive method for detecting and localising radiolucent foreign bodies in soft tissue. Because of its low cost, convenience and lack of risk, an ultrasonograph machine should be used in the ED and for in-office physical examination of patients suspected of harbouring radiolucent foreign bodies. Moreover, ultrasonography not only contributes preoperatively in detecting the presence, size and exact location and depth of foreign bodies but also provides intraoperative guidance during their percutaneous removal 1-9. Although a plain X-ray is considered the standard technique, ultrasonography is an indispensable tool for managing radiolucent foreign bodies. In one report 10 on ultrasonographic localisation and guided removal of foreign bodies embedded in the hand, 8 of 11 foreign bodies were removed using real-time intraoperative ultrasonographic guidance. The foreign bodies were seven pieces of wood and one piece of glass (length range: 4·5 mm–3 cm); all were radiolucent and would have been difficult to localise with any other preoperative or intraoperative technique. Our illustrative case, a hog bristle being a very small radiolucent foreign body on which there are no published reports, evidences the usefulness of this technique for these difficult-to-find items. Technological developments have modified the quality of ultrasonographic images, which can be superimposed without using a dedicated spool or a particular acquisition parameter. Most case reports and series studies have used 5–10 MHz linear transducers, which are widely available, simple to use and inexpensive, and will identify radiopaque and radiolucent foreign bodies (glass, metal and stone) as short as 4·5 mm. However, a recent series 11 reported detecting a 0·5-mm glass splinter using a high-frequency linear-array probe of 12–17 MHz. We believe that a high-frequency transducer offers a more accurate topographic assessment and has more potential for detecting tiny foreign bodies. However, in this case report, we used a 5–12-MHz linear array transducer to find a hog bristle. In our experience using ultrasonography to detect radiolucent foreign bodies, we agree with Blankstein et al. that examinations and routine check-ups of the extremities for foreign bodies are time consuming and require expertise8. We successfully used high-frequency ultrasonography to identify a tiny foreign body and our conclusion echoed a previous study that high-resolution (12–17 MHz) ultrasonography is substantially better than standard resolution (5–12 MHz) ultrasonography12, and is a worthy practical tool for diagnosis and a therapeutic adjuvant for removing foreign bodies from soft tissue. Moreover, as these devices continue to evolve and techniques improve, much smaller and softer foreign bodies than before may be detected. A detailed ultrasonographic examination is mandatory and well worth the effort for detecting embedded foreign bodies. Sui-Yi Chao, MD1, Tai-Chung Chern, MD2, I-Ming Jou, MD, PhD1, Yao-Lung Kuo, MD, Dr Med3 1Department of Orthopedics, National Cheng Kung University Hospital, College of Medicine National Cheng Kung University Tainan, Taiwan 2Chern Tai-Chung Orthopedic Clinics Ping-Tung, Taiwan 3Department of Surgery, National Cheng Kung University Hospital, College of Medicine National Cheng Kung University, Tainan and Dou-Liou Branch Tainan, Taiwan [email protected]