Point of Care Ultrasounds in the Diagnosis of Pulled Elbows

Point of Care Ultrasounds in the Diagnosis
of Pulled Elbows
Jin Gao
Word count
Introduction: 84
Case: 342
Discussion: 2926
Abstract:
The pulled elbow(PE) is a common childhood injury. In most cases, the clinical management is straight
forward, however, the diagnosis and management may be difficult if there is an unclear history, an
unwitnessed injury or an atypical mechanism of injury. This medical literature project evaluates the
effectiveness of point-of-care ultrasound in the diagnosis of PEs.
Method:
A literature search for peer reviewed articles on the use of ultrasonography in the diagnosis of PEs.
Results:
Six studies were found through the literature search and all six studies demonstrate that
ultrasonography can play an important role in the diagnosis and management of PEs. In the PE, there
is entrapment of the annular ligament and supinator muscle within the radiocapitellar joint. The
studies demonstrate that in the majority of children with PE, this entrapment can be seen as a J
shaped hypoechoic image on ultrasound. With manipulation and successful treatment, this
abnormality resolves as the annular ligament and supinator muscle return to their original positions.
Introduction
The pulled elbow (PE) is a common childhood injury. In most cases, the clinical management is
straight forward, however, the diagnosis and management may be difficult if there is an unclear
history, an unwitnessed injury or an atypical mechanism of injury(1,2).
With the increasing use of point of care ultrasound (POCUS) in the urgent care and emergency
department setting, I wondered whether POCUS can be used to aid the diagnosis of PE by directly
identifying soft tissue changes and by ruling out a fracture.

Case history
Day 1
Presenting complaint:
XX is a 21 month old boy who presented to an urgent care clinic on Friday with his parents.
He was picked up from day-care and his parents noticed that he was not using his left arm. He was
not in distress. His brother who is 1 year older, said he may have fallen at day-care. There were no
adult witnesses of any injuries.
XX is normally in good health. He has had two pulled elbows in the past which were treated in the
community. XX takes no regular medications. XX has no known drug allergies.
Examination:
XX was able to move his left hand but there was no active movement in his left elbow. He appears to
be tender around the mid-radius and ulna area. There was no tenderness in the elbow, wrist and
humerus. XX was neurovascularly intact.
X-ray forearm and elbow: no evidence of a fracture or elbow joint effusion.
Impression: Likely left pulled elbow.
Management:
XX was treated with the pulled elbow reduction manoeuvre, however, despite three attempts there
was no ‘click’. XX was very distressed during the attempts. XX was monitored and his left elbow
remained inactive. XX was subsequently discharged from the practice with a broad-arm sling and
advised to follow up in clinic the following day.
Day 2:
On the following day, XX followed up with a second urgent care doctor. He was still not using his left
elbow and was referred to Starship Emergency Department without further attempts at reduction.
At Starship Hospital, XX was reviewed by an emergency physician. He was re-X-rayed and the X-ray
was reviewed with the on-call radiologist. The X-ray showed no evidence of any fractures.
XX was given nitrous sedation, reduction manoeuvres were performed twice and a ‘click’ was noted
on the second attempt. XX was then monitored and discharged after he started to use his left arm.
On day 1, XX spent just over 1 hour at the urgent care clinic and on day 2, he spent over 3 hours in the
emergency department.
Discussion
The pulled elbow(PE) or radial head subluxation is a common childhood injury and most typically
occurs between 1 and 4 years of age. In this age group, it represents about 1% of musculoskeletal
injuries and forms up to 27% of injuries involving the elbow area(1,2).
The typical mechanism of injury involves a traction force on an extended arm, however, other less
common mechanisms such as falls and rolling over the arm have also been reported. Children with
this injury typically present non-distressed, with an inactive arm. The affected arm is often held in
pronation and has little or no soft tissue swelling around the elbow area. A simple reduction
manoeuvre is used to treat and confirm the diagnosis. Confirmation of diagnosis can be through the
detection of ‘clicking’ during the manoeuvre (in 72% of cases) or return of spontaneous movement of
the affected arm post-reduction.(1,2,3)
With the typical history and presentation, the majority of PE are straight forward to diagnose and
manage. However, as seen in our case history, the diagnosis and management may be difficult if there
is an unclear history, an unwitnessed injury or an atypical mechanism of injury. This is because elbow
fractures can mimic the findings of PE, in which case, the reduction manoeuvre should not be
attempted as it will result in unnecessary pain, parental anxiety and potentially iatrogenic fracture
dislocation (1,2,3). Currently, when there is uncertainty, an X-ray is taken to exclude a fracture before
the reduction manoeuvre is undertaken. If the child’s elbow remains inactive, the child is often
discharged with a sling and reviewed the following day or referred for a second opinion. It must be
noted that the pulled elbow is not identified on X-ray and in cases where there is uncertainty, the
diagnosis of PE is made once fracture is excluded.
With the increasing use of point of care ultrasound(POCUS) in the urgent care and emergency
department setting, I wondered whether POCUS can be used to aid the diagnosis of PE by directly
identifying soft tissue changes and by ruling out a fracture. This would enable speedier diagnosis and
management, and would avoid the unfavourable factors listed earlier (1,2,3).
Review of literature

Biomechanical and MRI studies have demonstrated that when a child sustains a PE, the traction force
on the extended elbow causes the radial head to sublux and the annular ligament to become
entrapped between the subluxed radial head and the capitellum (4,5). In recent years, several studies
have been conducted to examine the signs of PE on ultrasonography.
Kosuwon et al, were the first to report the use of ultrasound scanning(USS) in the diagnosis of PE. In
this study, 10 children with PE were examined and their findings were compared to 10 children with
normal elbows. It was observed that the radiocapitellar distance was increased in the PE group by an
average 3mm. This difference in radiocapitellar distance was very small and as a result, this sign
lacked sensitivity and specificity for the diagnosis of PE and therefore had limited use (6).
It was discussed in Dohi’s article that Minagawa’s research was the first to directly identify the
anatomical changes within the pulled elbow joint on USS. In Minagawa’s research, he examined the
USS findings of 32 children with PE by scanning the anterior surface of the radiohumeral joint in the
longitudinal axis. He found that the supinator muscle (which partially originates from the annular
ligament) and the annular ligament can be seen to be entrapped in the radiohumeral joint. This USS
finding formed a J- shaped image which was named the J-sign (See Figure 1). Minagawa’s article itself
was not accessible and therefore it is difficult to comment on its validity(7,8).
Figure 1. USS of the normal elbow (left) and PE (on right) through the anterior longitudinal axis of the
radiohumeral joint. The red arrows indicated the J sign. C. Capitellum, R. Radius, S. supinator. USS
image from Dr Kelvin Ward
Dohi retrospectively reviewed the USS findings of 70 children who presented to Dohi Orthopaedic
Hospital, Higashi Hiroshima, Japan between September 2010- February 2013. These children were
clinically diagnosed with PE and did not have any other imaging prior to USS. The children’s elbows
were scanned in the extended position and images were taken of the anterior surface in the
longitudinal axis. Scans were taken before and after manipulation(8).
Dohi observed a normal annular ligament in the normal elbow and an absence of a normal annular
ligament in the PE. In the PE, USS showed the supinator muscle and the annular ligament to be
trapped within the radiocapitellar joint displaying a J-shaped hypoechoic image; this is equivalent to
the J-sign described by Minagawa above(7). The J-shaped hypoechoic image disappeared after
successful reduction and the normal annular ligament was once again observed. It was noted that the
presence and then disappearance of the J-shaped hypoechoic image was seen in all 70 children, giving
the J-shaped hypoechoic image a sensitivity of 100% in the diagnosis of PE and its reduction(8).
In this study, Dohi reported that 10/70 children did not demonstrate the characteristic ‘click’
following manipulation and as a result, it was initially uncertain whether their elbows were
successfully reduced. Despite this, in these children the J-shaped hypoechoic image disappeared
immediately after reduction and the normal annular ligament was again seen. Retrospectively these
findings suggest that the disappearance of the J-shaped hypoechoic image and return of the normal
annular ligament is useful in the confirmation of successful reduction(8).
C
C
R R
S S
Annular ligament
C
Dohi’s findings suggest that USS is useful in the diagnosis of PE and in the confirmation of reduction.
However, Dohi’s findings are limited by its small population size and in its retrospective design. The
study only included a review of children with PE and was therefore unable to directly assess the
findings in other injuries which may mimic the PE. It is also uncertain whether we are able to apply
these findings to POCUS because the article did not indicate the skill/ experience of the
ultrasonographers and whether it mirrors that of urgent care / emergency department physicians
who are trained in POCUS.
Lee S H et al reviewed the usefulness of combining both USS and X-ray findings for the diagnosis of
PE. The team retrospectively reviewed the records of 37 consecutive children with a final diagnosis of
PE who presented to the Samsung Medical Centre, a tertiary hospital in Seoul, Korea. These children
presented between April 2015 and September 2018 and were referred to the orthopaedic team with
an atypical history or failed PE reduction. All of these children had both an X-ray and USS taken at the
time of presentation(9).
The X-rays were taken with the elbows in flexion and were reviewed by two independent
investigators who looked for evidence of the posterior fat pad sign. The USS were taken by a single
experienced paediatric orthopaedic surgeon with the child seated opposite to the operator. The
images were taken in the anterior longitudinal axis of the extended elbow. Once confirmation of PE
was achieved, a reduction manoeuvre was performed and considered successful if a ‘ click’ was felt
and the child was able to use their affected arm voluntarily. An USS was then repeated after
reduction(9).
Out of the 37 children studied, 9/37 were referred with an impression of occult fracture, 10/37 were
referred with an impression of unimproved contusion and 18/37 had undergone a prior PE reduction
manoeuvre without symptomatic improvement.
Prereduction imaging using X-ray and USS found:
– Posterior fat pad signs on X-ray in 16% of subjects;
– Entrapped supinator on USS in 100% of subjects (This is equivalent to the J-sign/ J-shaped
hypoechoic image described above(7,8);
– Absent annular ligament on USS in 74% of subjects;
– Coronoid and olecranon fossa effusion in 100% of subjects; and
– Deep synovial fringe in 63% of subjects.
Post reduction imaging with USS found:
– Disentangled and swollen supinator on USS in 100% of subjects;
– Restored annular ligament on USS in 100% of subjects;
– Supinator effusion on USS in 58% of subjects; and
– Retrieved synovial fringe on USS in 58% of subjects.
In this study, an entrapped supinator was seen on USS in 100% of cases with PE. In all of these cases,
the supinator returned to the original position once reduction had been achieved. This is consistent
with findings from both Minagawa and Dohi(7,8).
It was interesting to note that the posterior fat pad sign on X-ray and olecranon effusion on USS was
present in a small number of children with PE. Lee S H et al postulated that these signs may be
positive in PE because in some children the superior edge of the annular ligament may enter into the
radiocapitellar joint. As a result of this variation in anatomy, any disruption to the annular ligament,
such as in PE, may cause injury to the elbow synovial joint resulting in an effusion(9).
Lee S H et al’s findings are consistent with that of Dohi and Minagawa and suggest that the presence
and resolution of an entrapped supinator on USS (also known as the J-sign/ J-shaped hypoechoic
image) is 100% sensitive in the diagnosis of PE and confirmation of its successful management(7,8,9).
It must be noted that the study findings are limited in power due to its small study population. In
addition, the study participants are not fully representative of the patients we see in urgent care or in
the emergency department. This is because the study involves children that have been referred to the
orthopaedic department for a second opinion and these children may be more complex in their
presentation or management. The sonographer involved in this study was a paediatric orthopaedic
specialist who was experienced in USS; it is uncertain whether his/her level of skill is comparable to
that of an urgent care or emergency physician trained in POCUS.
Varga M et al conducted a prospective study to review the use of USS in the diagnosis of PE. The study
enrolled 205 children with a clinical suspicion of PE between October 2016 – November 2017. The
USS was carried out by two orthopaedic surgeons and an orthopaedic resident in training. The images
were taken of the elbow in extension and over the longitudinal dorsal plane of the olecranon fossa
and ventrally over the radio-capitellar joint. The clinicians looked for evidence of posterior fat pad
elevation and intra-articular synovial fringe enlargement on USS (This is equivalent to the J-sign
described above(7). Confirmation of a diagnosis of PE was via presence of painless movement in the
affected limb 15 minute post-reduction(10).
Of the 205 children examined 196 (95.6%) had PE and 9 (4.39 %) had fractures. 156/196 children with
PE demonstrated a positive synovial fringe enlargement. All the children with fracture and one with
PE demonstrated positive fat pad sign, as per table 1 (10)
n = 205 Pulled elbow n = 196 Fractures n = 9
Synovial fringe positivity 156 0
Sonographic fat pad sign positivity 1 9
Sonographic fat pad positivity and synovial fringe negativity 0 9
sonographic fat pad negativity and synovial fringe negativity 40 0
Sonographic fat pad and synovial fringe positivity 1 0
sonographic fat pad negativity and synovial fringe positivity 155 0
Table 1. Varga M et al study results(10)
The findings of this study, in which synovial fringe enlargement (equivalent to the J-sign, J-shaped
hypoechoic image) was found to be 79% sensitive and 100% specific in the diagnosis of PE, were in
contrast to the earlier studies where the sensitivity of the sign was 100%(7,8,9). This study also
demonstrated that the presence of both fat pad positivity and synovial fringe negativity had 100%
sensitivity and specificity for the diagnosis of fracture(10).
Similar to Lee S H et al, Varga M et al also found that fat pad abnormalities may be seen in a small
portion of children with PE. In this study, the only child with PE and a positive fat pad sign was late to
present and his PE remained unreduced for > 24 hours. Varga M et al postulated that the delayed
treatment may have allowed intra-articular fluid accumulation causing a positive fat pad sign(10). This
theory may also explain the higher proportion of children found to have a posterior fat pad sign in Lee
S H et al’s study above as their average time to USS was longer because they were referred from
other services(9).
Compared to the above studies, this study is superior as it was conducted prospectively and included
children with elbow fractures who presented like PE. This study allowed us to look for findings
suggestive of fractures in addition to those suggestive of PE. Once again, on its own, the study lacks
power due to its small population size. The sonographers involved in this study were orthopaedic
surgeons or an orthopaedic resident. This means their level of expertise in USS may not represent
that of urgent care or ED physicians.
Instead of reviewing the J-sign, Rabiner et al studied the use of the posterior fat pad sign on USS in
the diagnosis of PE. Rabiner et al conducted a prospective study between January 2011 – May 2012 in
a New York paediatric emergency department. They reviewed 42 children with a clinical diagnosis of
PE. The USS were conducted by a group of paediatric emergency physicians/ fellows who attended a
one hour session on the basics of using the USS to evaluate the presence of the posterior fat pad sign.
The clinicians involved were mostly novices in USS. In the study, both the affected and contralateral
elbows were imaged with the elbow in 90 degree flexion. Both dorsal longitudinal and transverse
views were obtained. Following the USS, the PEs were reduced. Successful reduction was defined as
return of spontaneous movements in the affected arm(11).
PE was confirmed in all cases and 6/42 cases (14%) showed a positive posterior fat pad sign. This
study once again proves that a positive posterior fat pad sign can be seen in children with PE and does
not necessarily indicate fracture(11).
It is interesting to note that Varga M et al suggested that a positive elbow effusion may be secondary
to delayed presentation, whereas Rabiner et al observed no clear correlation between delayed
presentation and the presence of a positive posterior fat pad sign(10,11). It was also noteworthy that
in the post-study analysis where the USS images were reviewed, the posterior fat pad sign categorised
as elevated by the emergency physicians were in fact very minimally elevated when compared to
those typically seen in fractures.
Conclusion
PE is a common childhood injury and in the majority of cases an accurate clinical diagnosis can be
reached easily and the child treated in a timely manner. Problems arise when the history is unclear or
the typical mechanism of injury has not occurred. It has been suggested that between 1-5% of
children with a clinical diagnosis of PE may actually have a fracture(1). Reduction attempts in these
children will cause unnecessary pain, anxiety and harm.
USS is an excellent imaging modality as it can be performed at the bedside and is becoming
increasingly available across urgent care clinics and the emergency department. It is also very safe for
the paediatric population who are at increased risk from radiation and is able to offer imaging in a
cost effective and timely manner.
Although the individual studies are small, the combination of the above 6 studies suggest that USS
imaging can play an important role in the diagnosis and management of PE. In PE, there is entrapment
of the annular ligament and supinator muscle within the radiocapitellar joint and the above studies
have demonstrated that in the majority of children with PE, this entrapment can be seen as a J shaped
hypoechoic image on USS. Similarly, with manipulation and successful treatment of PE, this
abnormality resolves as the supinator and annular ligament returns to its original position. The above
studies also suggest that an elbow joint effusion is not always associated with fractures and can be
seen in a small portion of children with PE.
Based upon the above findings, it is reasonable to suggest that, in a child such as XX, who presents
with a history and/or clinical findings suggestive of possible PE, the presence of a J shaped hypoechoic
image and a negative posterior fat pad sign on USS can be diagnostic for PE and the clinician can
proceed with manipulation with confidence. Success of manipulation can be confirmed with another
USS to check for restoration of the supinator and annular ligament to its normal position. In the
absence of a positive J shaped hypoechoic image or in the presence of a positive fat pad sign, the
possibility of fracture remains and the clinician may wish to proceed with X-ray and/or seek a second
opinion before performing PE reduction.
Therefore, in XX’s case, the use of POCUS by an experienced urgent care doctor may have helped in
the diagnosis of PE, eliminated the need for X-rays and given us the confidence to proceed with
further attempts at reduction in the community. This would have saved time, resources and
potentially his visit to the emergency department.
It is also important for clinicians to be reminded that although elbow effusions on USS and/or X-ray
are associated with fracture, they can also be seen in PE. Therefore it is vital that clinicians do not
automatically immobilise all children with an elbow effusion for a prolonged period of time thinking
that there is a underlying fracture.
POCUS for the diagnosis of PE should only be conducted by physicians who are specifically trained in
its identification. Given USS diagnosis is operator dependent and subject to interpretation error, it is
vital that further review of its use is conducted in the urgent care and emergency department setting
to ensure accuracy of sign identification and diagnosis.
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