Is ultrasound superior to plain radiography for detecting radiolucent soft tissue foreign bodies in the extremities?
Date First Published:
March 10, 2026
Last Updated:
March 10, 2026
Report by:
Pericles Philippou, Resident Doctor (Blackpool Teaching Hospitals NHS Foundation Trust)
Search checked by:
Daniel Darbyshire, Consultant
Three-Part Question:
In [patients with suspected radiolucent soft tissue foreign bodies in the extremities] is [ultrasound superior to plain radiography] as a [first-line imaging modality]?
Clinical Scenario:
A 34-year-old man presents to the Emergency Department after accidentally falling onto a wooden deck while repairing his garden fence. He reports immediate pain in his right palm and believes he may have a wooden splinter embedded in his hand. On examination, there is a small puncture wound over the thenar eminence with localised tenderness and mild swelling. No foreign body is visible externally. Neurovascular examination of the hand is normal. You suspect a retained radiolucent soft tissue foreign body (wood). Traditionally, plain radiographs would be requested as the initial imaging modality. However, given that wooden foreign bodies are often radiolucent and may not be visible on X-ray, you wonder whether bedside ultrasound would be a more sensitive first-line investigation.
Search Strategy:
A structured literature search was conducted via Ovid using MEDLINE, EMBASE and Cochrane databases. A combination of MeSH terms and free-text keywords were included:
(exp Foreign Bodies/ OR foreign bod* OR retained foreign bod* OR soft tissue foreign bod*) AND (exp Extremities/ OR exp Arm/ OR exp Leg/ OR exp Hand/ OR exp Foot/ OR extremit* OR arm* OR leg* OR hand* OR foot OR feet) AND (exp Ultrasonography/ OR ultrasound OR ultrasonograph* OR sonograph*) AND (exp Radiography/ OR exp X-Rays/ OR radiograph* OR x-ray* OR plain film*) AND (wood* OR plastic OR radiolucent)
In addition, forward citation tracking was performed using the Google Scholar “cited by” function on all included studies to identify any further relevant literature. Reference lists of selected papers were also screened to ensure no key studies were missed.
(exp Foreign Bodies/ OR foreign bod* OR retained foreign bod* OR soft tissue foreign bod*) AND (exp Extremities/ OR exp Arm/ OR exp Leg/ OR exp Hand/ OR exp Foot/ OR extremit* OR arm* OR leg* OR hand* OR foot OR feet) AND (exp Ultrasonography/ OR ultrasound OR ultrasonograph* OR sonograph*) AND (exp Radiography/ OR exp X-Rays/ OR radiograph* OR x-ray* OR plain film*) AND (wood* OR plastic OR radiolucent)
In addition, forward citation tracking was performed using the Google Scholar “cited by” function on all included studies to identify any further relevant literature. Reference lists of selected papers were also screened to ensure no key studies were missed.
Outcome:
The search identified a total of 119 papers, with no duplicates. Following title and abstract review, 101 papers were excluded. 18 papers underwent full-text review and a further 12 were excluded: 5 of these were non-human studies and 7 were not directly relevant to the three-part question.
6 papers were selected for final analysis: 4 prospective diagnostic cohort studies, 1 retrospective cohort study and 1 retrospective case series. The key results are summarised in table 1.
6 papers were selected for final analysis: 4 prospective diagnostic cohort studies, 1 retrospective cohort study and 1 retrospective case series. The key results are summarised in table 1.
Relevant Paper(s):
| Study Title | Patient Group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
|---|---|---|---|---|---|
| Accuracy of ultrasonography in detecting radiolucent soft-tissue foreign bodies Tahmasebi M.; Zareizadeh H.; Motamedfar A. May 2014 United States | 51 consecutive patients with clinically suspected radiolucent soft tissue foreign bodies in extremities and negative plain radiographs (n=51, male: 75%, mean age: 27.6) | Prospective diagnostic cohort study (Level 2 evidence) | Detection of retained foreign body confirmed by surgical exploration or ultrasound-guided removal; calculation of sensitivity, PPV and accuracy | • Foreign body confirmed in 47/51 patients | • No direct statistical comparison with radiography (radiographs negative by inclusion criteria) • Small sample size • Single-centre study • Ultrasound performed by experienced radiologist (may limit generalisability) • Selection bias (only radiograph negative patients included) |
| • Ultrasound sensitivity: 97.9% | |||||
| • Positive predictive value: 92% | |||||
| • Overall accuracy: 90.2% | |||||
| • 1 false negative, 4 false positives | |||||
| • All initial plain radiographs were negative | |||||
| Role of ultrasound in detection of radiolucent foreign bodies in extremities Tantray MD; Rather A; Manaan Q; Andleeb I; Mohammad M; Gull Y August 2018 India | 120 patients with clinically suspected soft-tissue radiolucent foreign body in extremities and negative plain radiographs (n=120, male: 68.3%, mean age: 26.8) | Prospective diagnostic cohort study (Level 2 evidence) | Detection of foreign body confirmed at surgical exploration; calculation of sensitivity, PPV, and accuracy of ultrasound | • Ultrasound positive in 114/120 patients | • No direct statistical comparison with radiography (radiographs negative by inclusion criteria) • Selection bias (only radiograph negative patients included) • Single-centre study • Ultrasound performed by experienced radiologist (may limit generalisability) |
| • Foreign body retrieved in 108/120 | |||||
| • Among six US-negative cases, one had a foreign body found on exploration | |||||
| • Sensitivity: 99.08% | |||||
| • Positive predictive value: 94.13% | |||||
| • Overall accuracy: 94.16% | |||||
| The role of ultrasonography in detection and localization of radiolucent foreign body in soft tissues of extremities Shrestha D; Sharma UK; Mohammad R; Dhoju D January - March 2009 Nepal | 23 patients with clinically suspected non-radiopaque soft tissue foreign bodies in extremities. (n=23, male: 67%, mean age: 31.7) | Retrospective diagnostic cohort study (Level 2–3 evidence) | Detection of foreign body using plain radiography and ultrasound, confirmed by surgical exploration | • Plain radiography detected 0/23 foreign bodies | • Retrospective design Small sample size (n=23) • No formal calculation of sensitivity, specificity, or comparison statistics. • Single-centre study in a resource-limited setting (may affect generalisability) • Operator-dependent ultrasound performance |
| • Ultrasound positive in 19/23 cases | |||||
| • 18/19 ultrasound-positive cases confirmed at surgery (1 granuloma false positive) | |||||
| Ultrasonography detection of radiolucent foreign bodies in soft tissue compared to computed tomographic scan Al-Zahrani S.; Kremli M.; Saadeddin M.; Ikram I.; Takroni T.; Zeidan H. 1995 Saudi Arabia | 31 consecutive patients with clinically suspected radiolucent foreign bodies (wooden splinters) in soft tissues of the extremities. (n=31, male = 74%, mean age: 22.8) | Prospective diagnostic cohort study (Level 2 evidence) | Detection of radiolucent foreign bodies using plain radiography, CT scan and ultrasonography, with surgical exploration as the reference standard | • 20/31 patients had foreign bodies confirmed at surgical exploration | • Small sample size (n=31) • Single-centre study • No formal calculation of sensitivity, specificity, or comparison statistics • No evaluation of operator variability |
| • Plain radiography detected 0/20 confirmed foreign bodies (0% accuracy) | |||||
| • Ultrasound detected 18/20 confirmed foreign bodies (90% accuracy; 10% false negative rate) | |||||
| • No false positives reported with ultrasound | |||||
| • Foreign bodies embedded in the calcaneum and the talonavicular joint were not detected by ultrasound | |||||
| The use of sonography in the identification, localization, and removal of soft tissue foreign bodies Gibbs T.S. January 2006 United States | 20 patients with suspected soft tissue foreign bodies in extremities (n=20, male = 50%, mean age: 30) | Retrospective case series (Level 3 evidence) | Detection and localisation of soft tissue foreign bodies using ultrasound compared with plain radiography | • 6 radiolucent (wooden) foreign bodies were present | • Retrospective design • Small sample size (n=20) • Not limited to radiolucent foreign bodies (included metallic and glass) • No formal calculation of sensitivity, specificity or comparison statistics • Selection bias (only patients who underwent ultrasound included) • Ultrasound performed by experienced sonographers (may limit generalisability) |
| • Radiographs were performed on 5 of these patients and detected 0/5 | |||||
| • Ultrasound detected 6/6 wooden foreign bodies | |||||
| Clinical value of ultrasonography in the detection and removal of radiolucent foreign bodies Crawford R.; Matheson A.B. 1989 United Kingdom | 39 consecutive patients with suspected retained foreign body in the hand and negative plain radiographs (n=39, male = 82%, mean age: 41.7) | Prospective diagnostic cohort study (Level 2 evidence) | Detection and localisation of radiolucent foreign bodies confirmed at surgical exploration | • 20 radiolucent foreign bodies confirmed at surgery | • Single-centre study • Small sample size (n=39) • Operator-dependent ultrasound performance • Only hand injuries included (limited generalisability to all extremities) • No direct statistical comparison with radiography (radiographs negative by inclusion criteria) |
| • Ultrasound true positives: 19/20 | |||||
| • False negatives: 1/20 | |||||
| • Sensitivity: 95% | |||||
| • False positives: 2 | |||||
| • Specificity: 89.5% |
Author Commentary:
The evidence consistently demonstrates that ultrasound has high sensitivity for detecting radiolucent soft tissue foreign bodies in the extremities. Across diagnostic cohort studies, ultrasound sensitivity ranged from 90% to 99%, with positive predictive values of 92% to 94%.1,2,3,4,6 In contrast, plain radiography detected none of the confirmed radiolucent foreign bodies in the studies where it was evaluated.3,4 These findings support the plausibility that radiolucent materials such as wood are poorly visualised on radiographs but readily identified on ultrasound.
However, the findings should be interpreted with caution. Some studies included only patients with negative plain radiographs; this introduces selection bias and limits direct head-to-head statistical comparison between the imaging modalities.1,2 Sample sizes were small (n=23–120), and all studies were single-centre, which may affect external validity.1–4 Operator dependence is another important limitation, as ultrasound examinations were frequently performed by experienced practitioners, which may overestimate diagnostic performance in less-experienced hands.1,2,5
False positives and false negatives were reported in several studies. One study demonstrated a 10% false negative rate, with deeply embedded foreign bodies proving more difficult to detect.4 These findings suggest that while ultrasound is highly sensitive, it is not infallible, particularly in anatomically complex regions.
The retrospective case series further supports the utility of ultrasound, demonstrating successful identification of all six radiolucent wooden foreign bodies, whereas radiographs detected none.5 However, its retrospective design and small sample size limit the strength of its conclusions.
Overall, the current evidence suggests that ultrasound is superior to plain radiography for detecting radiolucent soft tissue foreign bodies in the extremities. The evidence base is limited by small, single-centre studies and potential operator dependence; however, the consistency of findings across multiple cohorts strengthens the conclusion. Larger, multicentre prospective studies directly comparing ultrasound with radiography would help to clarify its role as a first-line imaging modality and better define its generalisability.
However, the findings should be interpreted with caution. Some studies included only patients with negative plain radiographs; this introduces selection bias and limits direct head-to-head statistical comparison between the imaging modalities.1,2 Sample sizes were small (n=23–120), and all studies were single-centre, which may affect external validity.1–4 Operator dependence is another important limitation, as ultrasound examinations were frequently performed by experienced practitioners, which may overestimate diagnostic performance in less-experienced hands.1,2,5
False positives and false negatives were reported in several studies. One study demonstrated a 10% false negative rate, with deeply embedded foreign bodies proving more difficult to detect.4 These findings suggest that while ultrasound is highly sensitive, it is not infallible, particularly in anatomically complex regions.
The retrospective case series further supports the utility of ultrasound, demonstrating successful identification of all six radiolucent wooden foreign bodies, whereas radiographs detected none.5 However, its retrospective design and small sample size limit the strength of its conclusions.
Overall, the current evidence suggests that ultrasound is superior to plain radiography for detecting radiolucent soft tissue foreign bodies in the extremities. The evidence base is limited by small, single-centre studies and potential operator dependence; however, the consistency of findings across multiple cohorts strengthens the conclusion. Larger, multicentre prospective studies directly comparing ultrasound with radiography would help to clarify its role as a first-line imaging modality and better define its generalisability.
Bottom Line:
The current evidence suggests that ultrasound is superior to plain radiography for detecting radiolucent soft tissue foreign bodies in the extremities.
Level of Evidence:
Level 2: Studies considered were neither 1 or 3
References:
- Tahmasebi M.; Zareizadeh H.; Motamedfar A.. Accuracy of ultrasonography in detecting radiolucent soft-tissue foreign bodies
- Tantray MD; Rather A; Manaan Q; Andleeb I; Mohammad M; Gull Y. Role of ultrasound in detection of radiolucent foreign bodies in extremities
- Shrestha D; Sharma UK; Mohammad R; Dhoju D. The role of ultrasonography in detection and localization of radiolucent foreign body in soft tissues of extremities
- Al-Zahrani S.; Kremli M.; Saadeddin M.; Ikram I.; Takroni T.; Zeidan H.. Ultrasonography detection of radiolucent foreign bodies in soft tissue compared to computed tomographic scan
- Gibbs T.S.. The use of sonography in the identification, localization, and removal of soft tissue foreign bodies
- Crawford R.; Matheson A.B.. Clinical value of ultrasonography in the detection and removal of radiolucent foreign bodies