Rebecca Fieles, MS4
The Article: Tantray, et al. “Role of ultrasound in detection of radiolucent foreign bodies in extremities” Strategies in Trauma and Limb Reconstruction (2018) 13:81–85
The Idea: Penetrating foreign bodies are common reasons for emergency department visits. Radiolucent foreign bodies such as splinters, wood or glass may be missed and potentially cause complications such as pain, abscess or neurodeficits. Ultrasound, in addition to CT, CR and MRI are all imaging modalities used to find retained foreign bodies. The purpose of this study was to determine the effectiveness of sonography in detecting radiolucent foreign bodies.
The Study: This is a single hospital observational study that took place in Kashmir from January 2014 to January 2016.
Inclusion Criteria: Symptomatic patients with definite history and clinical suspicion of soft tissue foreign body and negative radiography were included in the study.
Exclusion Criteria: none
A single radiologist read radiographs and performed the ultrasound examinations of each patient using a sonosite Micromaxx USG with high-frequency (13-6 MHz) linear array transducer. Location, size, depth and orientation of the FB were documented as was its relationship to other structures. A single orthopedic surgeon performed direct surgical exploration guided by the sonographic findings.
Primary Endpoints: 1) Presence or absence of a foreign body on ultrasound imaging. 2) Foreign body found on surgical exploration.
The Results: 120 patients underwent surgical exploration. 114 had a positive ultrasound. Of these foreign body was removed from 108 patients. In the remaining 6 patients with a positive USG, 5 had underwent at least one previous exploration. 6 patients had a negative ultrasound. One of these had a strong suspicion of FB with chronic discharging sinus near the Achilles insertion site and a thorn was removed on surgical exploration. 90 patients were male and 30 were female. Average age was 27.6 years with a range of 6-70 years. Foreign bodies removed were wooden (41 cases), thorn (38 cases), rubber/plastic from nail slipper (22 cases), and glass (8 cases). FB size ranged from 3-32mm with a mean of 15mm. Foreign bodies were removed from foot (69 cases) and hands (26 cases), the ankle region, wrist, thigh, leg, knee, forearm. The accuracy, sensitivity, and PPV of ultrasound detection of FB not seen on X-ray were 94.16, 99.08, and 94.13%, respectively.
The Takeaway: It is important to detect and remove foreign bodies to avoid the potential consequences of pain, abscess, and chronic drainage. Conventional radiographs are great for ruling out radio-opaque foreign bodies but can be negative in 86% of patients with radiolucent foreign bodies such as wood. Similarly, MRI can fail to detect foreign bodies when they are small and there is no associated abscess or fluid collection. In addition, it is more expensive and time intensive than ultrasound. Finally, while CT has greater sensitivity than plain X-ray, it is not as sensitive as ultrasound or MRI and uses radiation. This study proved that ultrasound is a highly effective imaging modality for the detection of radiolucent foreign bodies and facilitated removal by surgical exploration. It is especially useful in underdeveloped nations with financial constraints and in farming populations where splinters and wood foreign bodies are particularly common. Overall, ultrasound is an excellent tool to determine the presence of radiolucent foreign bodies and should be used in every case of suspected retained foreign body as it is sensitive, cheap, fast and does not expose the patient to radiation.