Utilising point-of-care ultrasound for the diagnosis of bilateral pulled elbow in a 2-year-old boy: a case report

Introduction

Background

Pulled elbow, also known as nursemaid’s elbow, is the term applied to subluxation of the radial head commonly encountered in children under the age of 5 years (1). It often occurs as a result of sudden or forceful longitudinal traction to the forearm, often from an adult or older child (2), and is one of the most frequent upper limb injuries to present to the Paediatric Emergency Department (PED) in this age group (3,4), with a peak incidence between 2 and 3 years of age. However, it has been reported in infants as young as 5 months associated with rolling over, leading to the arm becoming trapped underneath the infant’s body (5). Thus, while diagnosis has traditionally been made based on the classical history, this isn’t always available. Furthermore, clinical examination may be difficult to undertake or may not yield sufficient clues.

Rationale and knowledge gap

Bilateral pulled elbow is rare with only a very small number of cases reported in the literature (6-10). A large study in China involving 11,404 cases of pulled elbow found only 0.11% had bilateral pulled elbows, mostly occurring when children were playing and being held by both hands (6). Meiner et al. (7) reported two cases of bilateral pulled elbow, both with similar mechanisms as described in the above case of being pulled up by both arms. In one of their cases, the diagnosis was only suspected after blood tests and elbow X-rays were carried out and were unremarkable. There have been two case reports of bilateral pulled elbow with unusual or unwitnessed mechanisms (8,9). One child had an unwitnessed injury and then developed apparent bilateral upper extremity weakness resulting in multiple imaging modalities, including CT scans, with an eventual diagnosis of bilateral pulled elbow being made (8). The second case report was that of a 4-year-old girl with previous episodes of pulled elbow who presented with her arms held in the characteristic “funny” position after trying to lift a heavy object. A clinical diagnosis was made in this case (9). None of the existing case reports or studies relate to the use of POCUS in diagnosing bilateral pulled elbow.

Objective

To highlight the utility of POCUS for the diagnosis of bilateral pulled elbow. We present this article in accordance with the CARE reporting checklist (available at https://pm.amegroups.com/article/view/10.21037/pm-25-80/rc).

Case presentation

A healthy 2-year-old boy was brought to the PED after his mother was concerned about an apparent inability to use both of his arms that afternoon. The child was sat in his highchair and was not feeding himself as usual, instead crying out in distress. The child had been well with no history of fever, falls, or trauma.

When presenting to our PED the child walked into the room with both arms hanging loosely at his sides. His vital signs were normal, and he was comfortable at rest. He would not lift up his hands to attempt to get toys and any slight upper limb movement was initiated from the shoulder. Inspection did not reveal obvious swelling, erythema, or bruising throughout the upper limbs, and the rest of the examination was normal.

A point-of-care ultrasound (POCUS) was undertaken by the authors using the GE Logiq System and high-frequency 12 MHz transducer. As per our established departmental protocols, scanning started by interrogating for the presence of elbow joint effusion or hemarthrosis. The probe was placed in the olecranon fossae of both elbows in the transverse orientation, as shown in Figure 1A,1B. This was negative for effusion on each side as demonstrated. Next, the distal and mid humerus was assessed again in both the longitudinal and transverse orientation to exclude any extracapsular fracture that would not result in elbow joint effusion. This was unremarkable, so the distal radius and ulna were assessed for any cortical abnormalities suggestive fracture, of which there were none. Finally, the probe was placed along the radiocapitellar line in the longitudinal orientation in order to assess for the sonographic signs of pulled elbow. As demonstrated in Figure 2A,2B, this child had a positive “hook sign” on each side, denoting evidence of bilateral pulled elbow.

Figure 1 POCUS image of the (A) left olecranon fossa and (B) right olecranon fossa in transverse orientation using the high-frequency 12 MHz linear probe. This demonstrates the normal appearances without evidence of joint effusion. POCUS, point-of-care ultrasound.

Figure 2 POCUS image along the (A) left radiocapitellar line and (B) right radiocapitellar line using the high-frequency 12 MHz linear probe. This demonstrates a positive “hook sign” (thin arrows) caused by the entrapment of the supinator muscle within the joint space. It also demonstrates a prominent or exaggerated synovial fringe (thick arrows). POCUS, point-of-care ultrasound.

A collateral history was obtained from the child’s father, who recalled that he had lifted him up from the floor holding both of his wrists 2 hours previously, and reported hearing a click when doing so. On closer questioning, the child’s father reported this had happened previously, once in the left arm and once in the right arm, but never at the same time.

After explanation of the POCUS findings, verbal consent was obtained for manipulative reduction. This reduction was carried out on each upper limb simultaneously by each author. D.J.M. reduced the right radius using the flexion supination method, and B.M. reduced the left side using the hyperpronation method, owing to the relative comfort and familiarity of clinicians with each method. “Clicks” were readily appreciated by each clinician, suggesting that straightforward reductions had occurred. POCUS was repeated along the radiocapitellar line for each elbow, demonstrating resolution of the “hook sign” and a less prominent synovial fringe, confirming that a positive reduction had occurred on each side, see Figure 3A,3B. The child returned to function within 1 minute and was able to give the clinicians the confirmatory “high-fives” using both arms. Education was provided about the relative propensity of this child to sustain subluxation of the radial head with caution, in particular, given to lifting the child from the hand or wrist in the future.

Figure 3 POCUS image along the (A) left radiocapitellar line and (B) right radiocapitellar line using the high-frequency 12 MHz linear probe. This has been taken post-reduction and demonstrates resolution of the hook sign (thin arrows), with the supinator muscle showing its normal tapered appearance, not extending into the joint space. The previously evident synovial fringe is much less prominent than before (thick arrows). POCUS, point-of-care ultrasound.

This is the first documented case of bilateral pulled elbow being identified using POCUS.

Ethical considerations

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient’s legal guardian for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

Key findings

Pulled elbow is a common paediatric diagnosis and one which clinician usually recognise based on the characteristic presentation of the child. Diagnosis has traditionally relied upon the history being provided from a carer or witness; however, as one study demonstrated, in up to 50% of cases, the history may be atypical or lacking altogether (11). Bilateral pulled elbow is very rare with only few cases noted in the literature. Subsequently, it may not be a differential diagnosis considered by most clinicians, particularly where the history is unclear.

Strengths and limitations

Strengths of this case report include the fact that it is the first documented example of the use of POCUS for bilateral pulled elbow and that it highlights a rare condition within the paediatric literature. Ultrasound examinations were conducted by experienced clinicians with prior research in POCUS, including relating to this condition.

Limitations include the fact that it is a single case report, making generalisability of findings more difficult. We also acknowledge that clinical follow-up did not occur; however, that would not be expected for this condition.

Comparison with similar research

POCUS has been demonstrated to be highly effective in correctly identifying pulled elbow (12-19). One recent case series in the UK included 110 children with elbow injury, of which 37 had underwent POCUS as part of their assessment. Of these, 29 had a typical history of pulled elbow, and all had positive signs on POCUS for pulled elbow. From the other eight patients with an atypical history, three were found to have a positive POCUS for pulled elbow and were correctly diagnosed as such after manipulative reduction; the remaining five went on to have other diagnoses, meaning the specificity was 100% (range, 47.8–100%) (P=0.00003) and sensitivity was 100% (19).

Most of the studies use the “hook sign” (sometimes referred to as the “J sign”) when describing positive findings for pulled elbow (12,13). This relates to an entrapment of the supinator muscle and annular ligament within the radio-humeral joint, causing it to extend more proximally into the joint space, giving a characteristic hooked appearance. Some studies also comment upon the exaggerated appearance of the synovial fringe (14-18) which in our opinion always co-exists to some extent but has not been demonstrated to be statistically significant on its own (14). In one novel study POCUS was used to visualise the real-time reduction of pulled elbow, something which can provide further reassurance to the clinician that successful treatment has taken place (20).

Differential diagnoses for children presenting with reduced movement of the upper limb include supracondylar fractures of the humerus and radial head. Here, POCUS can be extremely useful by excluding traumatic elbow joint effusion, which can help reliably rule-out intracapsular fractures while ruling-in pulled elbow (21).

Implications for clinical practice

Upper limb POCUS protocols (22) have been demonstrated to be an easily teachable skill (Figure 4) with short periods of focused training (23) and represent a valuable tool alongside clinical assessment for a range of upper limb pathologies (24).

Figure 4 The transducer position along the radiocapitellar line to obtain views to assess for pulled elbow. The probe marker may be caudal or cranial. Image reproduced from (22).

Utilising POCUS for undifferentiated paediatric elbow injuries allows for the prompt diagnosis and treatment of pulled elbow without the need for X-rays. This confers obvious benefits to the patient, such as a reduced length of stay in the PED, as well as the economic advantages to the department.

Conclusions

Pulled elbow is a commonly made diagnosis in the PED. Bilateral pulled elbow is much rarer. Upper limb POCUS is quick, easy to learn, and well-tolerated by paediatric patients. POCUS has been demonstrated to be highly reliable in cases of suspected pulled elbow, both for diagnosis and in confirming successful reduction. It serves as an invaluable diagnostic tool in the PED for evaluating undifferentiated elbow injuries, particularly when the history may be lacking, atypical, or as in this case unusual.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://pm.amegroups.com/article/view/10.21037/pm-25-80/rc

Peer Review File: Available at https://pm.amegroups.com/article/view/10.21037/pm-25-80/prf

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://pm.amegroups.com/article/view/10.21037/pm-25-80/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient’s legal guardian for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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