PEM POCUS Series: Pediatric Musculoskeletal Ultrasound

PEM POCUS pediatric musculoskeletal badge

Read this tutorial on the use of point of care ultrasonography (POCUS) for pediatric musculoskeletal evaluation. Then test your skills on the ALiEMU course page to receive your PEM POCUS badge worth 2 hours of ALiEMU course credit.

Module Goals

  1. List the indications for performing pediatric musculoskeletal (MSK) point-of-care ultrasound (POCUS)
  2. Describe the technique for performing specific pediatric MSK POCUS applications
  3. List anatomical landmarks for specific MSK POCUS applications
  4. Interpret signs of fracture, effusion, dislocation, and osteomyelitis with POCUS
  5. Describe the limitations of MSK POCUS

Case Introduction: Adolescent with Left Knee Swelling

A 13-year-old female with no past medical history presents to the emergency department with pain and swelling to her left knee. The pain started 3 days ago, with the pain worsening and swelling noted on the day prior to arrival. She can bear weight but has a limp. She has had no other current or past joint pain or swelling, no known trauma, no fever or other infectious symptoms, no recent travel, and no known insect or tick bites. She spent the summer at camp in the northeast United States. Her vaccines are up to date.

On arrival, her vital signs are:

Vital SignFinding
Temperature37.3 C
Heart rate109 bpm
Blood pressure117/74
Respiratory rate20
Oxygen saturation (room air)99%

On physical examination, she is well appearing and in no acute distress. Her exam is significant for left knee swelling and tenderness to palpation anteriorly with decreased knee flexion due to pain. She has no redness, warmth, or numbness around her knee. She has an antalgic gait but can bear weight.

Given her pain and swelling of her left knee, blood tests and X-rays are ordered, and orthopedics is consulted. You decide to perform a musculoskeletal point-of-care ultrasound (MSK POCUS) examination.

Musculoskeletal POCUS can be performed for a variety of indications including trauma, swelling, erythema, pain, decreased range of motion of a joint, and limp or inability to bear weight. It can assist in early diagnosis of fracture, effusion, dislocation, and osteomyelitis and allow for expedited treatment. Children and adolescents are ideal candidates for MSK POCUS as they generally have less subcutaneous tissue, making it easier to obtain ultrasound images to assess for pathology.

Note: This module focuses on diagnostic uses in musculoskeletal POCUS and not on procedural uses.

Musculoskeletal POCUS can be incorporated into the physical examination by scanning the area of injury, the point of maximal pain or tenderness, or a joint for effusion.

Probe Selection and Patient Comfort

Linear ultrasound probe

Figure 1. Linear ultrasound probe.

  • Use a high frequency linear probe (Figure 1) to obtain high resolution images of generally superficial structures in MSK POCUS.
    • A curvilinear probe may be necessary for older children to examine structures with depth greater than 4-6 cm (e.g., hip).
  • Patient comfort is the key to obtaining quality images.
    • Place in a position of comfort on the bed, chair, or in a parent’s lap.
    • Apply copious warm gel (Figure 2L).
    • Rest the base of your scanning hand on a non-tender area to avoid putting excessive pressure on a painful area (Figure 2R).
    • Provide pain control.
    • Distract with a toy, book, or phone/tablet.
    • Consult a child life specialist, if available, to help ease the child’s anxiety.
Linear probe with gel and floating probe technique

Figure 2. Linear probe with copious gel (L). The clinician floats the probe on the gel and rests the base of the scanning hand on an uninjured area to minimize pressure on the painful area (R).

Pro-Tips

  1. When performing MSK POCUS, it is helpful to scan the contralateral normal side first. This allows for identification of the child’s normal anatomy, including growth plates if present, and comparison when scanning the area of pain/injury. It also allows the child to understand the MSK POCUS exam before scanning the painful area.
  2. Match the probe footprint to the area being scanned: a wider, longer footprint for the hips or long bones; a smaller footprint for the small bones of the hands or feet.
Musculoskeletal POCUS is excellent at identifying fractures of long bones (e.g., radius and ulna); however, it is less reliable for identifying fractures at joints, epiphyses, and the small bones of the hands and feet, where curved, irregular contours make imaging with POCUS more difficult. Additionally, non-displaced physeal fractures (Salter-Harris I) may be missed by POCUS.

Technique

To evaluate for fracture, dislocation, or osteomyelitis, place a linear transducer over the desired area to identify changes to the bony contour or alignment.

  • Look everywhere. Scan bones circumferentially as much as possible and in perpendicular planes (longitudinal and transverse axes) to avoid missing pathology. Fractures may escape detection if the transducer is placed parallel to the course of the fracture.
  • Scan the contralateral side for comparison. This is especially crucial when the pathology involves or is adjacent to a physis.
  • Use the water bath technique. Submerge the injured extremity in a basin of water to facilitate imaging of the small bones of the hands and feet (Figure 3). The probe does not need to be in contact with the injured area in a water bath, and the probe is submersible up to the point where the electrical cord exits the probe.
Water bath technique to image a phalanx dorsally and ventrally with the submerged probe floating above the hand

Figure 3. Water bath technique to image a phalanx dorsally (L) and ventrally (R), with the submerged probe floating just above but not touching the injured hand.

Normal finger phalanx imaged with water bath technique

Figure 4. Normal finger phalanx imaged with the water bath technique, with the probe not touching the finger and approximately 1 cm of anechoic fluid between the probe and the finger. Air bubbles may be visible in the water.

Figure 5. Ultrasound clip of a normal finger phalanx using the water bath technique.

Normal Findings

Normal bone is seen as a hyperechoic line with posterior acoustic shadowing.

Normal physis:

  • Longitudinal view (Figure 6): Appears as a V-shaped, hypoechoic, uniform band of cartilage between the metaphysis and epiphysis that is symmetric with the contralateral side.
  • Transverse view (Figure 7): Appears as a regular but ragged area between the hyperechoic curvilinear metaphysis and epiphysis of the bone.

Longitudinal view of normal physis showing V-shaped hypoechoic band between metaphysis and epiphysis

Figure 6L. Longitudinal view of a normal physis. The hypoechoic band of cartilage forms a smooth V-shape between the hyperechoic metaphysis and epiphysis (yellow arrows: physis above, bone below). Compare with the contralateral side to confirm symmetry.

Figure 6R. Longitudinal scanning of a normal physis.

Transverse view of normal physis with regular but ragged appearance between metaphysis and epiphysis

Figure 7L. Transverse view of a normal physis. The cartilage band appears regular but ragged between the curvilinear hyperechoic metaphysis and epiphysis (yellow arrows: physis above, bone below).

Figure 7R. Transverse scanning of a normal physis.

Ultrasonography can reliably detect diaphyseal (long bone) fractures including the forearm, lower leg, and clavicle. It is also useful for detection of other fractures.

1. Long Bone Fracture

  • Longitudinal view (Figure 8): A fracture is visualized as a disruption in the bony cortex with a discontinuity or step-off. There may be associated periosteal changes, periosteal fluid, or hematoma. Angulation and displacement of the fracture fragments may be measured.
  • Transverse view (Figure 9): The fracture site is identified by an irregularity in the hyperechoic, curvilinear bony cortex and/or a “jump” in the location of the bone as the fracture site is crossed.
  • Ultrasound can detect fractures as small as 1 mm [1].
  • In the forearm and lower leg, be sure to scan both bones at the site of injury to avoid missing a fracture.

Pediatric distal radius fracture in longitudinal view showing cortical step-off with physis distal to the fracture

Figure 8L. Forearm fracture in longitudinal view. An angulated, displaced distal radius fracture is shown, with the physis visible distal to the fracture site.

Figure 8R. Longitudinal scanning of a distal radius fracture.

Pediatric distal radius fracture in transverse view showing irregular curvilinear bony surface with both edges of the fracture site visible

Figure 9L. Forearm fracture in transverse view. The fracture site shows an irregular curvilinear bony surface with both edges of the fracture visible.

Figure 9R. Transverse scanning of a distal radius fracture.

2. Buckle Fracture

  • A buckle fracture appears as a small “bump” in the linear bone cortex, usually without any discontinuity of the bone (Figure 10).

ultrasound finger fracture

Figure 10L. Two examples of buckle fracture of the distal radius (arrows). Top: small “bump” in the bony cortex without discontinuity. Bottom: a second buckle fracture of the distal radius in longitudinal view.

Figure 10R. Buckle fracture of the distal radius.

3. Finger Phalanx Fracture

  • The discontinuity of the cortex of a phalanx may be seen in longitudinal and transverse views (Figures 11 and 12).
  • A fracture appears as a break in the hyperechoic cortex, in contrast to a joint, which is regular and similar to adjacent fingers or to the contralateral normal side.

Pediatric finger phalanx fracture imaged in a water bath showing discontinuity of the bony cortex with FRACTURE and JOINT labeled

Figure 11. Discontinuity of the bony cortex of the phalanx (arrow) in a water bath, consistent with fracture. The adjacent joint is regular and intact.

Figure 12L. Longitudinal scanning of a phalanx fracture.

Figure 12R. Transverse scanning of a phalanx fracture.

4. Metacarpal Fracture

  • The discontinuity of the cortex of a metacarpal may be seen in longitudinal and transverse views (Figure 13).

Figure 13L. Cortical discontinuity (arrow) in a metacarpal fracture, with periosteal fluid (asterisk) adjacent to the fracture site.

Figure 13R. Scanning of a metacarpal fracture.

5. Nasal Fracture

  • The nasal bones may be identified, with fractures appearing as a discontinuity of the bone (Figures 14, 15, and 16). Use copious gel to facilitate imaging in this superficial, highly curved area and to minimize pain to the affected area.

Linear ultrasound probe positioning to evaluate for a pediatric nasal fracture

Figure 14. Linear probe positioning to evaluate for a nasal fracture.

Transverse ultrasound of a normal pediatric nasal bone (L) and a pediatric nasal fracture with cortical discontinuities indicated by yellow arrows (R)

Figure 15. Transverse view of a normal nasal bone (L) and a nasal fracture with cortical discontinuities (arrows, R).

Figure 16. Transverse scan of a nasal fracture.

6. Healing Fracture

  • Healing fractures will have a discontinuity in the bone with varying degrees of periosteal thickening and callus formation (Figures 17 and 18). The callus will be hypoechoic initially and will become more hyperechoic over time.

Longitudinal ultrasound of a healing distal radius fracture with periosteal thickening and callus

Figure 17L. Healing distal radius fracture in longitudinal view, with periosteal thickening and callus formation.

Figure 17R. Longitudinal scan of a healing distal radius fracture.

Transverse ultrasound of a healing distal radius fracture with periosteal thickening and callus

Figure 18L. Healing distal radius fracture in transverse view, with periosteal thickening and callus formation.

Figure 18R. Transverse scan of a healing distal radius fracture.

For evaluation of a joint effusion, the linear or curvilinear transducer is used to identify anechoic or hypoechoic fluid in the joint space. POCUS identifies the effusion but cannot distinguish hemorrhagic, infectious, or inflammatory etiologies; labs and/or advanced imaging are needed for further work-up.

POCUS of the lower extremity can assess for hip, knee, or ankle effusions. Findings must be interpreted with the clinical presentation and physical examination. For hip effusions, the Kocher criteria may be used to evaluate for septic hip.

1. Hip

  • See the ALiEM module on POCUS: Hip Effusion for more detail.
  • Positioning and probe placement: With the child’s leg in slight external rotation, place the linear transducer on the anterior hip parallel to the long axis of the femoral neck. Point the probe marker toward the patient’s head (Figure 19L).
  • Normal findings
    • Identify the hyperechoic curvilinear femoral head (+/- physis), hyperechoic linear femoral neck, and the posterior surface of the iliopsoas muscle (Figure 19R).
    • Look for fluid/effusion between the femoral neck and the posterior surface of the iliopsoas muscle. Normally a femoral fat pad sits in this space.

Linear ultrasound probe positioning on the anterior hip (L) and normal hip anatomy showing the femoral head with open physis, femoral neck, and iliopsoas muscle (R)

Figure 19. Linear probe positioning to evaluate for hip effusion (L) and normal hip anatomy (R). The arrow points to the femoral head physis.

Figure 20. Longitudinal scanning of a normal hip.

  • Abnormal finding: Hip effusion
    • Location: Anechoic or hypoechoic fluid located between the femoral neck and the iliopsoas muscle (Figure 21).
    • Measurement: A convex fluid collection measuring >5 mm (or >2 mm difference from the contralateral normal side) is positive for a hip effusion.
      • There is debate regarding measurement technique for hip effusion, with measurement of the hypoechoic fluid directly vs. measurement from the anterior surface of the femoral neck to the posterior surface of the iliopsoas muscle. However, clinically significant effusions will likely be positive (>5 mm) regardless of measurement technique, and asymmetry compared to the contralateral normal hip will usually be evident.

Hip effusion with anechoic fluid layering over the femoral neck measured to 5.7 mm, with femoral head, open physis (arrow), and iliopsoas muscle (asterisk) visible

Figure 21. Hip effusion with anechoic fluid layering over the femoral neck measured to 5.7 mm. Also visible are the femoral head with an open physis (arrow) and the iliopsoas muscle (*).

Figure 22. Longitudinal scanning of the hip showing a hip effusion.

2. Knee

  • Positioning and probe placement: Place the linear transducer longitudinally on the anterior distal femur, just superior to the patella, in the midline over the quadriceps tendon. Point the probe marker toward the patient’s head (Figure 23L). This single, longitudinal view of the suprapatellar bursa, which has direct communication with the knee joint, is the most sensitive for identifying a knee effusion (Figure 24). You may also fan the probe in longitudinal and transverse views to further evaluate the suprapatellar bursa for effusion.
    • Place a towel roll under the knee to provide about 30 degrees of knee flexion, the optimal position for detecting a knee effusion.
    • Avoid excessive pressure: pressure from the probe can compress the suprapatellar bursa and mask a small effusion.
    • To avoid missing a small effusion, milk fluid downward, medially, and/or laterally toward the probe to push fluid into the suprapatellar bursa. Hold the probe lightly while doing this.

Linear probe positioning over the anterior distal femur with a towel under the knee (L) and normal knee anatomy showing quadriceps tendon, cartilage around the patella, and femur (R)

Figure 23. Linear probe positioning to evaluate for knee effusion. Note the towel under the knee for slight knee flexion (L). Normal knee anatomy showing the quadriceps tendon (arrows) and cartilage around the patella (asterisk) (R).

Anatomic diagram of the bursae of the knee, highlighting the suprapatellar bursa contiguous with the knee joint space

Figure 24. Normal bursae anatomy at the knee. The suprapatellar bursa is contiguous with the knee joint space [2].

Figure 25. Longitudinal scanning of a normal knee.

  • Normal findings
    • Identify the linear, hyperechoic distal femur (+/- physis), the patella, and the quadriceps tendon attaching to the patella (Figure 23R). There is a pre-femoral fat pad between the femur and the quadriceps tendon. Look for a fluid collection in this suprapatellar space.
    • The patella ossifies at approximately 3-6 years of age, so younger children may still have a cartilaginous patella. The patella appears hypoechoic and may not have posterior acoustic shadowing. Do not confuse the cartilaginous patella with a joint effusion.
  • Abnormal finding: Knee effusion
    • Location: Anechoic or hypoechoic fluid sits in the suprapatellar bursa between the femur and the quadriceps tendon (Figure 26).
    • Measurement: Fluid measuring >2 mm in height is positive for a knee effusion.

Figure 26. Two examples of a knee effusion with anechoic fluid (*) between the femur and the quadriceps tendon (L) and with measurement of effusion (R).

Figure 27. Longitudinal scanning of a knee effusion.

3. Ankle

  • Positioning and probe placement: Place the linear transducer in the longitudinal axis anteriorly over the ankle joint in the midline. Point the probe marker toward the patient’s head (Figure 28L) to evaluate the tibiotalar joint. The tibiotalar joint is the area most likely to identify an effusion. Interrogate the entire joint by fanning the probe in longitudinal and transverse views to avoid missing an effusion.
  • Normal findings
    • Identify the curvilinear hyperechoic lines with posterior acoustic shadowing of the tibia and talus bones and the “V” shape of the joint (Figure 28R).

Figure 28. Ankle POCUS: Linear probe positioning to evaluate for ankle effusion (L) and normal ankle anatomy with an arrow pointing to the tibiotalar joint space (R).

  • Abnormal finding: Ankle effusion
    • Anechoic or hypoechoic fluid is seen in the tibiotalar joint space (Figure 29).

Bilateral ankle POCUS comparison with normal left tibiotalar joint and an asterisk marking anechoic effusion in the right tibiotalar joint

Figure 29. Ankle POCUS of bilateral ankles showing an effusion (*) in the right tibiotalar joint compared with the normal left side.

Figure 30. Longitudinal scanning of an ankle effusion.

POCUS of the upper extremity can assess for elbow and shoulder effusions. When an elbow effusion is identified after trauma, radiography is typically needed to further characterize a fracture.

1. Elbow

  • Positioning and probe placement: With the child’s elbow flexed to 90 degrees, place the linear transducer over the posterior distal humerus in longitudinal and transverse views to visualize the olecranon fossa and the elbow posterior fat pad (Figure 31).

Linear ultrasound probe positioning on the posterior elbow in longitudinal (L) and transverse (R) orientations with the elbow flexed to 90 degrees

Figure 31. Linear probe positioning for performing POCUS of the elbow to evaluate the elbow posterior fat pad in longitudinal (L) and transverse (R) views.

  • Normal findings
    • Identify the hyperechoic cortex of the distal humerus and the olecranon fossa.
    • The normal posterior fat pad (PFP) sits in the olecranon fossa below the continuation of the distal humeral line in the longitudinal view and below the line connecting both edges of the olecranon fossa in the transverse view. The triceps muscle can be seen above the elbow joint (Figure 32).

Normal elbow POCUS in longitudinal (L) and transverse (R) views showing the posterior fat pad (PFP) sitting below the distal humeral line in the olecranon fossa, with triceps muscle above and humerus below

Figure 32. Elbow POCUS: Normal elbow anatomy in longitudinal (L) and transverse (R) views with the posterior fat pad (PFP) located under the distal humeral line (dotted line).

Figure 33. Scanning of a normal elbow in longitudinal (L) and transverse (R) views.

  • Abnormal finding: Elbow effusion
    • Elbow US has high sensitivity and moderate specificity for fracture, so a negative scan makes fracture unlikely.
    • Sonographic findings: The posterior fat pad is elevated above the distal humeral line in the longitudinal view, and above the line connecting both sides of the olecranon fossa in the transverse view (Figure 34). Lipohemarthrosis, i.e., blood and lipid material in the posterior fat pad, may appear as hypoechoic areas within the elevated fat pad (Figure 36).
    • Clinical significance: An elevated posterior fat pad and/or lipohemarthrosis is a marker of intracapsular elbow fracture, because the posterior fat pad sits intracapsular but extra-synovial.
      • Caution: The radial neck and medial epicondyle are extracapsular, so fractures at these sites may occur without an elevated posterior fat pad.
    • Application to nursemaid elbow: Annular ligament displacement (nursemaid elbow) does not usually produce a significant effusion or lipohemarthrosis. When the diagnosis is in question, a POCUS showing a normal posterior fat pad and no lipohemarthrosis may help rule out fracture and support proceeding with closed reduction.

Elbow effusion on POCUS with elevated posterior fat pad (PFP) rising above the distal humeral line in longitudinal view (L) and above the olecranon fossa line in transverse view (R), pushing up on the triceps muscle

Figure 34. Elevated posterior fat pad in longitudinal view rising above the distal humeral line (L) and transverse view rising above the line connecting both edges of the olecranon fossa (R). In both views, the posterior fat pad pushes up on the triceps muscle.

Figure 35. Scanning of an elbow effusion with an elevated posterior fat pad in longitudinal (L) and transverse (R) views.

Elbow POCUS showing elevated posterior fat pad with lipohemarthrosis marked by yellow asterisks in longitudinal (L) and transverse (R) views

Figure 36. Elbow POCUS: Elevated posterior fat pad with lipohemarthrosis (*) in longitudinal (L) and transverse (R) views.

2. Shoulder

  • Positioning and probe placement: Place the linear transducer in the transverse view over the posterior shoulder and point the probe marker laterally (Figure 37L).
  • Normal findings
    • Identify the hyperechoic curvilinear humeral head (+/- physis) and the hyperechoic glenoid (Figure 37R). The humeral head should be located in the glenoid fossa, with the humeral head and glenoid in the same horizontal plane.
  • Abnormal finding: Shoulder effusion
    • Anechoic fluid is seen around the humeral head within the glenohumeral joint (Figure 38).

Linear ultrasound probe positioning in the transverse view over the posterior shoulder (L) and corresponding normal shoulder anatomy showing humeral head, physis, and glenoid (R)

Figure 37. Shoulder POCUS: Linear probe positioning to evaluate for shoulder effusion (L) and the corresponding ultrasound view with normal shoulder anatomy (R).

Shoulder POCUS showing a shoulder effusion with anechoic fluid (asterisk) adjacent to the humeral head, with the physis indicated by an arrow

Figure 38. Shoulder POCUS: anechoic fluid (*) adjacent to the humeral head (L) and transverse scanning of the same effusion (R).

1. Shoulder Dislocation

  • Evaluate the relative positions of the glenoid and humeral head.
  • In a normal shoulder, the humeral head and glenoid should be in approximately the same horizontal plane (Figure 37R).
  • Anterior shoulder dislocation: The humerus is farther from the transducer and thus deeper on the ultrasound screen (Figure 39).
  • Posterior shoulder dislocation: The humerus is closer to the transducer and thus higher up on the ultrasound screen.
  • POCUS can be used to confirm relocation of the humerus into the glenoid fossa after a shoulder reduction.
Transverse shoulder POCUS demonstrating an anterior shoulder dislocation, with the glenoid labeled in the upper portion of the image and the humerus labeled deeper, indicating anterior displacement of the humeral head away from the posteriorly placed probe

Figure 39. Transverse view of an anterior shoulder dislocation: humeral head dislocated anteriorly, or farther away from the probe (L) and corresponding transverse scanning (R).

2. Finger Dislocation

  • In a finger dislocation, the bone malalignment at the interphalangeal joint can be seen (Figure 40).

Finger dislocation on POCUS with the probe positioned dorsally (L) showing the dorsal aspect of the interphalangeal joint and ventrally (R) showing the malaligned phalangeal bones with LEFT PINKY label

Figure 40. Finger dislocation with probe positioned dorsally (L) and ventrally (R).

Figure 41. Scanning of a finger dislocation: dorsal view (L) and ventral view (R).

  • Ultrasound findings of osteomyelitis may precede X-ray findings by several days.
  • Sonographic findings: Disrupted or irregular bony cortex, periosteal elevation and/or abscess, and increased vascular flow (Figure 42).

Osteomyelitis of the distal femur on POCUS showing irregular bony cortex with periosteal abscess marked by asterisk (L) and color Doppler showing increased vascular flow adjacent to the periosteal abscess (R)

Figure 42. Osteomyelitis of the distal femur with irregular bony cortex and periosteal abscess (*) (L) and increased vascular flow adjacent to the periosteal abscess (R).

Figure 43. Scanning of a distal femur with osteomyelitis: longitudinal view (L) and transverse view (R).

Figure 44. Longitudinal scanning of a distal femur with osteomyelitis showing increased vascularity on color Doppler.

Bony pathology that may be missed

MSK POCUS is excellent for long-bone fractures but is less reliable for fractures at joints, epiphyses, and the small bones of the hands and feet, whose curved, irregular contours are more difficult to image. Non-displaced physeal fractures (Salter-Harris I) and fractures <1 mm may also be missed. POCUS generally focuses on the area of injury and does not image the entire bone, so distant pathology can be missed.

Additionally, for elbow evaluation, radial neck and medial epicondyle fractures are extra-capsular and may occur without an associated effusion. A normal posterior fat pad on POCUS does not exclude these fractures. If a patient has tenderness at the radial neck or medial epicondyle, obtain further imaging.

Underlying pathology that cannot be characterized

POCUS can identify the presence of pathology such as a joint effusion or bone infection, but it cannot determine the etiology (e.g., hemorrhagic vs. infectious vs. inflammatory effusion). Further work-up, such as labs, joint aspiration, or advanced imaging, is needed to characterize the underlying process.

Image sharing across systems

Sharing POCUS clips within or between institutions can be cumbersome. Where feasible, archiving images to the medical record helps preserve diagnostic context for the broader healthcare team.

There have been several systematic reviews and meta-analyses on musculoskeletal POCUS applications.

StudyApplicationNSensitivitySpecificityComments
Morello et al, Eur J Pediatr 2024 [3]Distal forearm fractures23 studies, 3,484 children92–100%85–100%Scoping review
Hassankhani et al, Skeletal Radiol 2024 [4]Clavicle fractures7 studies, 1,255 patients94%98%Pediatric subset (4 studies, 863 children): Sn 96%, Sp 94%
Zhao et al, Medicine 2019 [5]Hand fractures7 studies, 842 patients91%96%Fracture prevalence 39%
Tokarski et al, J Pediatr 2018 [6]Elbow fractures6 studies, 512 children96%81%Fracture prevalence 48%
Gottlieb et al, Am J Emerg Med 2019 [7]Shoulder dislocation7 studies, 739 patients99%99%Dislocation prevalence 41%; associated fracture: Sn 98%, Sp 99.8%

Table 1. Key systematic reviews and meta-analyses on musculoskeletal POCUS.

Other notable studies focusing on musculoskeletal POCUS include the following.

Pediatric Distal Forearm Fracture

The BUCKLED multicenter, noninferiority, randomized trial by Snelling et al enrolled 262 children ages 5–15 years with clinically non-angulated distal forearm injuries [8]. Children were randomized to POCUS or radiography. Those in the POCUS group with a cortical break identified also received radiography and usual care; buckle fractures were managed with a splint.

Results: At 4 weeks, physical function of the affected arm was non-inferior in the POCUS group. The POCUS group also had fewer X-rays, shorter emergency department length of stay, and higher patient satisfaction. The authors emphasized that physical function at 4 weeks is an important, real-world clinical outcome.

Joint Effusions

Adhikari and Blaivas compared POCUS with physical examination for the diagnosis of joint effusions [9]. They enrolled 54 adult patients with joint pain, erythema, and swelling.

Results: POCUS was more sensitive and accurate than physical examination. POCUS altered emergency department management in 65% of patients, either by avoiding an unnecessary joint aspiration or by identifying a clinically occult effusion.

Pediatric Hip Effusion

Jones et al conducted a multicenter prospective diagnostic study in children <18 years requiring radiology-performed hip ultrasound, comparing hip POCUS with the radiology study as the reference standard [10]. 161 children were enrolled by 18 PEM physicians, with 3 high-volume operators contributing 62% of cases.

Results: POCUS had an overall sensitivity of 94% and specificity of 98%. Among high-volume operators, sensitivity was 98% (specificity 98%); among low-volume operators, sensitivity was 83% (specificity 97%).

Case Resolution

A musculoskeletal POCUS of the left knee with a linear, high-frequency probe demonstrated a joint effusion in the suprapatellar bursa with internal septations (Figures 45 and 46).

Pediatric left knee POCUS composite showing suprapatellar joint effusion (L) and effusion with internal septations (R)

Figure 45. Left knee POCUS demonstrating a joint effusion in the suprapatellar bursa (L) and internal septations within the effusion (R).

Figure 46. Longitudinal scan of the left knee showing the joint effusion with internal septations.

Initial laboratory studies showed a white blood cell count of 10 × 109/L, ESR 69 mm/hr, and CRP 32 mg/L. Knee radiographs were negative for fracture. Orthopedics performed an arthrocentesis that yielded synovial fluid with 52,000 white blood cells/µL, raising concern for septic arthritis.

The patient was admitted, started on intravenous antibiotics, and taken to the operating room for incision, drainage, and washout. Joint fluid cultures returned negative, but Lyme serologies returned positive. She was transitioned to a 28-day course of doxycycline for Lyme arthritis.

Read more from this series → PEM POCUS Series

References

  1. Grechenig W, Clement HG, Fellinger M, Seggl W. Scope and limitations of ultrasonography in the documentation of fractures—an experimental study. Arch Orthop Trauma Surg. 1998;117(6-7):368-371. doi:10.1007/s004020050268. PMID: 9709853
  2. Wilson C. Suprapatellar bursitis: causes, symptoms, treatment & recovery. Knee Pain Explained. Published June 2, 2024. Accessed May 23, 2026. https://www.knee-pain-explained.com/suprapatellar-bursitis.html
  3. Morello R, Mariani F, Snelling PJ, Buonsenso D. Point-of-care ultrasound for the diagnosis of distal forearm fractures in children and adolescents: a scoping review. Eur J Pediatr. 2024;184(1):19. doi:10.1007/s00431-024-05877-w. PMID: 39548004
  4. Hassankhani A, Amoukhteh M, Jannatdoust P, Valizadeh P, Gholamrezanezhad A. A systematic review and meta-analysis on the diagnostic utility of ultrasound for clavicle fractures. Skeletal Radiol. 2024;53(2):307-318. doi:10.1007/s00256-023-04396-3. PMID: 37433884
  5. Zhao W, Wang G, Chen B, et al. The value of ultrasound for detecting hand fractures: a meta-analysis. Medicine (Baltimore). 2019;98(44):e17823. doi:10.1097/MD.0000000000017823. PMID: 31689869
  6. Tokarski J, Avner JR, Rabiner JE. Reduction of radiography with point-of-care elbow ultrasonography for elbow trauma in children. J Pediatr. 2018;198:214-219.e2. doi:10.1016/j.jpeds.2018.02.072. PMID: 29681446
  7. Gottlieb M, Holladay D, Peksa GD. Point-of-care ultrasound for the diagnosis of shoulder dislocation: a systematic review and meta-analysis. Am J Emerg Med. 2019;37(4):757-761. doi:10.1016/j.ajem.2019.02.024. PMID: 30797607
  8. Snelling PJ, Jones P, Bade D, et al; BUCKLED Trial Group. Ultrasonography or radiography for suspected pediatric distal forearm fractures. N Engl J Med. 2023;388(22):2049-2057. doi:10.1056/NEJMoa2213883. PMID: 37256975
  9. Adhikari S, Blaivas M. Utility of bedside sonography to distinguish soft tissue abnormalities from joint effusions in the emergency department. J Ultrasound Med. 2010;29(4):519-526. doi:10.7863/jum.2010.29.4.519. PMID: 20375371
  10. Jones RM, Malia L, Snelling PJ, et al. Diagnostic accuracy of point-of-care ultrasound for hip effusion: a multicenter diagnostic study. Ann Emerg Med. 2025;86(6):566-575. doi:10.1016/j.annemergmed.2025.04.033. PMID: 40481828

Procedural Use of a Mini C-arm in the Emergency Department

C-arms are mobile, C-shaped X-ray units that allow dynamic imaging for a wide range of procedures in outpatient clinics, procedure suites, operating rooms, and even emergency departments. Their uses include: fracture reduction and fixation, hardware placement, joint injections, and other image-guided interventional procedures. They are available in a variety of sizes including a mini C-arm that is specifically designed for imaging smaller body parts such as the hands and wrists.

Mini C-arms in emergency departments (ED) are not commonplace but when available they are often in trauma centers and most commonly utilized by orthopedic surgeons. Literature on the use of mini C-arms in the ED has mostly been for distal forearm fractures, where they have been shown to facilitate safe and effective fracture reductions and reduce the need for repeat formal radiographs during reductions [1-4]. Although mini C-arms are not typically used by emergency medicine (EM) physicians, familiarity with this imaging modality may be a valuable skill, especially for trainees rotating on the orthopedics service.

This article reviews mini C-arm anatomy, fluoroscopic principles, radiation safety and equipment, and illustrates its application in a case of a distal radius fracture.

Mini C-arm structure

The C-arm’s name comes from the C-shape that connects the X-ray source on one side to the image detector on the other, allowing rotation around the patient (Figure 1).

Anatomy of a mini c-arm machine illustration

Figure 1. Anatomy of a mini c-arm machine

How it works

  1. The operator controls acquisition of images through a foot pedal (allowing single images or live imaging).
  2. X-rays are generated through a tube which diverge out in a cone-like projection and pass through structures such as bone, which absorb X-rays differently based on characteristics like density and tissue thickness.
  3. After passing through structures, X-rays are absorbed on the opposite side by an image detector.
  4. The image detector converts this radiation to light, which is then processed by a computer to create a digital image visible on the monitor.

The C-arm has a rotation mechanism and an adjustable arm with various joints that allow movements in multiple planes. It allows orbital rotation, vertical and lateral movements, tilt, or swivel (Figure 2).

Maneuverability of a mini c-arm illustration

Figure 2: Maneuverability of a mini c-arm

How to set up a mini C-arm

  1. Plug in the device to a power source
  2. Turn on the switch to power on the device
  3. Use the monitor and/or keyboard to set up a study (some monitors are touch screen)
  4. Enter patient information
    • Find and select the option to begin study
    • Adjust the C-arm to the desired position
  5. Position the body part of interest flat and center on the detector
  6. Place the foot pedal in an easy to reach position
  7. Ensure that everyone in the room has radioprotective equipment (see radiation safety and equipment below)
  8. Step on the foot pedal to obtain an image or activate live imaging (review individual devices manuals to determine function of pedals)
  9. Save desired images

How to interpret images on a mini C-arm

Interpreting an image with a mini C-arm requires familiarity with fundamental radiographic principles related to image projection.

Laterality:

Unlike formal radiographs which include left or right markers, orientation of fluoroscopic images on a mini C-arm will be displayed based on the orientation of the image detector.

To illustrate this, in Figure 3, the right hand is rested with the palm resting directly on the image detector. On the monitor, the image appears as if the operator were directly looking at the hand, with the thumb on the left-most side. Most C-arms allow inversion of images on the monitor if another orientation is preferred.

Note: The X-ray beam travels from dorsal (posterior) to palmar (anterior), corresponding to a posteroanterior (PA) view.

Illustrated mini C-arm image of hand in posteroanterior view.

Figure 3: Illustrated mini C-arm image of hand in posteroanterior view

Magnification and depth

The relative distance between the X-ray source, the object, and the image detector affects image magnification and apparent depth of structures. To put it simply: the closer an object is to an X-ray source, the more magnified it appears; the closer an object is to the image detector, the less magnified it appears. This is analogous to the size of a shadow formed when a finger is moved closer to a light source. This principle affects image interpretation and highlights the importance of standardized positioning when obtaining images [5].

To illustrate this effect, we can consider the lateral view of the hand. Starting from the position in Figure 3, the hand can be supinated so that the ulnar aspect rests on the detector producing a lateral view (Figure 4). In this orientation, the thumb and second metacarpal may appear slightly magnified because they are now closer to the X-ray source. This also applies to the relative appearance of the radius and ulna.

Illustrated mini C-arm image of hand in lateral view

Figure 4: Illustrated mini C-arm image of hand in lateral view

As an analogy, imagine using a mini C-arm to image a rubber duck. If the duck is placed flat on the detector, the part closest to the X-ray source—the head—will appear slightly magnified. If the duck has an abnormally long neck that brings the head closer to the X-ray source, this magnification increases further (Figure 5). This same concept explains the apparent difference in heart size between posteroanterior (PA) and anteroposterior (AP) chest radiographs.

llustrated mini C-arm image of rubber duck

Figure 5: Illustrated mini C-arm image of rubber duck

This concept is important when using the mini C-arm for fracture reduction. You often want to capture as much of the entire body part as possible in the X-ray image while decreasing magnification, which means you will position the extremity directly against the image detector as far away as possible from the X-ray source while performing a reduction.

Radiation safety and protection

C-arms, like standard X-rays, emit ionizing radiation. Although most of the radiation is directed at patients, interactions between X-rays and surrounding matter produce scatter radiation, which is the primary source of radiation exposure to personnel. Repeated exposure is associated with increased lifetime risk of cancer, cataracts, thyroid issues including cancer, and fertility issues [6].

Radiation dose is measured in various units, including millirem (mrem) [5]. For context:

  • Average background radiation exposure (due to cosmic rays, radioactive elements in earth’s crust, etc) to U.S. residents is on average 310 mrem/year or <1 mrem/day
  • A cross country flight from NY to LA is ~5 mrem
  • A chest x-ray is ~10 mrem
  • A CT abdomen/pelvis is ~1,000 mrem

A benefit of the mini C-arm is that it emits less radiation than a standard-sized C-arm [8, 9]. In pediatric studies of distal forearm reductions performed with mini C-arm fluoroscopy, the estimated radiation exposure per case ranged from approximately 30 to 80 mrem, with lower exposures observed when trainees had completed radiation safety training, likely reflecting behavioral changes including fewer image acquisitions and shorter fluoroscopy activation [10]. Thus image acquisition should be intentional to reduce unnecessary radiation to both patients and personnel.

Radiation exposure follows the inverse square law, where if you double your distance from the X-ray source, you reduce exposure by one-fourth the original intensity. When possible, standing further away (at least 1 meter) from the X-ray source is recommended to reduce exposure (Figure 6) [5].

Additionally, use of radiation protective equipment such as lead aprons, thyroid shields, and leaded glasses, can significantly attenuate scatter radiation [8]. See Figure 7.

Inverse square law of radiation

Figure 6: Inverse square law of radiation

Radiation protective equipment

Figure 7: Radiation protective equipment

Bottom line:

  • Image only when necessary
  • Stand at least 1 meter away from the X-ray source when feasible
  • Utilize appropriate radiation protective equipment
  • By adhering to these principles, radiation exposure can be minimized when using a mini C-arm

Case: Distal radius fracture reduction with mini C-arm fluoroscopy

You are rotating through orthopedics and holding the consult pager. A 30-year-old patient presents to the ED after falling on their right outstretched hand, resulting in a deformity to the right distal forearm.

On examination, the skin appears intact and distal neurovascular exam is normal. Formal three-view wrist radiographs show an impacted, dorsally angulated transverse distal radius fracture without intra-articular extension.

Your senior recommends a reduction under fluoroscopy with your assistance. You perform a hematoma block, apply finger traps, and suspend the extremity vertically under ~10 lbs of traction. While the arm remains in traction, you bring the mini C-arm into the room and apply lead shields.

Obtaining images:

  1. Position the C-arm so that the image detector is near the affected arm. For a reduction, you should obtain PA and lateral views (oblique views are excluded in this example for simplicity).
  2. To obtain a PA view, ensure the palmar side of the distal forearm is against the detector (Figure 8).
  3. To obtain a lateral view, place the ulnar aspect of the distal forearm against the detector (Figure 9).

Note: Since the forearm is suspended in traction, sometimes you will need to rotate the mini C-arm around the extremity to obtain the correct alignment, instead of manipulating the arm.

Illustrated mini C-arm image of a distal radius fracture in posteroanterior view

Figure 8: Illustrated mini C-arm image of a distal radius fracture in posteroanterior view

\Illustrated mini C-arm image of a distal radius fracture in lateral view

Figure 9: Illustrated mini C-arm image of a distal radius fracture in lateral view

Important radiographic measurements:

In these views, assess radiographic parameters such as radial height, radial inclination, ulnar variance, and volar versus dorsal angulation angles (Supplemental Figures 1 and 2).

Post-reduction imaging:

Once the fracture appears appropriately reduced, obtain repeat C-arm images prior to applying a splint (Figure 10). After splint placement, obtain another set of images to confirm the reduction was maintained. Finally, order a formal post-reduction three-view wrist radiograph.

Illustrated mini C-arm images of a post-reduction distal radius fracture

Figure 10: Illustrated mini C-arm images of a post-reduction distal radius fracture

Restrictions on the use of fluoroscopy

Before using a mini C-arm, clinicians should confirm that they are appropriately credentialed and permitted to operate the device under local or state regulations, as fluoroscopy use laws differ across states and countries. Alternatively, a fluoroscopy credentialed radiation technologist can operate the device while the clinician performs the reduction.

Conclusions

Mini C-arms are a useful imaging modality available in select emergency departments. With an understanding of proper device operation and radiographic concepts such as image projection and radiation safety, the mini C-arm can be an effective tool to facilitate procedures such as distal radius fracture reduction. Although ultrasound remains the primary imaging modality for many procedures in the emergency department, the mini C-arm may potentially be a useful adjunct in other ED procedures such as joint aspirations and could warrant future exploration.

Measurements of the distal radius in posteroanterior view

Supplemental Figure 1: Measurements of the distal radius in posteroanterior view

Measurements of the distal radius in lateral view

Supplemental Figure 2: Measurements of the distal radius in lateral view

References

  1. Lee SM, Orlinsky M, Chan LS. Safety and effectiveness of portable fluoroscopy in the emergency department for the management of distal extremity fractures. Ann Emerg Med. 1994;24(4):725-730. doi:10.1016/S0196-0644(94)70284-5. PMID: 7998561
  2. Lee MC, Stone NE 3rd, Ritting AW, et al. Mini-C-arm fluoroscopy for emergency-department reduction of pediatric forearm fractures. J Bone Joint Surg Am. 2011;93(15):1442-1447. doi:10.2106/JBJS.J.01052. PMID 21915550 
  3. Dailey SK, Miller AR, Kakazu R, Wyrick JD, Stern PJ. The effectiveness of mini-C-arm fluoroscopy for the closed reduction of distal radius fractures in adults: a randomized controlled trial. J Hand Surg Am. 2018;43(10):927-931. doi:10.1016/j.jhsa.2018.02.015. PMID: 29573894
  4. Sumko MJ, Hennrikus WL, Slough J, King S. Measurement of radiation exposure when using the mini C-arm in pediatric orthopaedics. J Pediatr Orthop. 2016;36(2):122-125. doi:10.1097/BPO.0000000000000418. PMID: 25730377
  5. Bushberg JT, Seibert JA, Leidholdt EM Jr, Boone JM. The essential physics of medical imaging. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2012.
  6. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Ionizing Radiation. Atlanta, GA: US Department of Health and Human Services; 1999. Available from: https://www.ncbi.nlm.nih.gov/books/NBK597577/
  7. Centers for Disease Control and Prevention. Radiation Thermometer. Updated January 2, 2024. Accessed December 26, 2025. https://www.cdc.gov/radiation-emergencies/causes/radiation-thermometer.html
  8. Giordano BD, Ryder S, Baumhauer JF, DiGiovanni BF. Exposure to direct and scatter radiation with use of mini-C-arm fluoroscopy. J Bone Joint Surg Am. 2007;89(5):948-952. doi:10.2106/JBJS.F.00733. PMID: 17473130
  9. Giordano BD, Baumhauer JF, Morgan TL, Rechtine GR. Patient and surgeon radiation exposure: comparison of standard and mini-C-arm fluoroscopy. J Bone Joint Surg Am. 2009;91(2):297-304. doi:10.2106/JBJS.H.00407. PMID: 19181973
  10. Gendelberg D, Hennrikus W, Slough J, King S. A radiation safety training program results in reduced radiation exposure for orthopedic residents using the mini C-arm. J Pediatr Orthop. 2015;35(8):e123-e129. doi:10.1097/BPO.0000000000000345. PMID: 26566977
By |2025-12-30T18:08:43-08:00Dec 31, 2025|Orthopedic, Radiology|

SAEM Clinical Images Series: Mind the Gap

scapholunate

A 25-year-old right-handed female with a longstanding history of right wrist pain presents with wrist pain. Her chronic pain had worsened over the past 2-3 weeks. She did not recall a specific recent injury, but did recall that she had a painful injury to the same wrist in the past when she fell on her outstretched hand. She was seen several weeks prior for the injury, but did not seek follow-up care after her initial evaluation. She had pain with any movement and complained of tenderness around the wrist, but denied any fever, redness, swelling, or any other complaints.

Vitals: All vital signs are normal.

General: No acute distress.

Musculoskeletal: Right upper extremity: Normal shoulder and elbow range of motion without tenderness. The right wrist is tender over the proximal carpal row and thenar eminence, with mild snuffbox tenderness. Radial and ulnar pulses are intact. Radial, median, and ulnar nerve motor and sensory function intact. The patient can fully flex and extend at the wrist, but has pain with motion. There is no obvious visual deformity and no ecchymosis. Capillary refill in all digits <2 seconds. Can flex and extend all digits without difficulty. There is no warmth or erythema over the joint.

Non-contributory

Terry Thomas sign (widening of the scapholunate space)

The scapholunate ligament is disrupted.

Scapholunate advanced collapse (SLAC)

A fall on an outstretched hand (FOOSH) injury can result in not only fractures, but also ligamentous disruptions. Scapholunate Advanced Collapse (SLAC) injury is a progressive form of degenerative osteoarthritis of the wrist, often resulting from untreated disruption of the scapholunate ligament (SLL). SLAC is the most common form of post-traumatic osteoarthritis of the wrist. Injury to the SLL may be identified by intra-articular space widening between the scaphoid and lunate bones of the proximal row of the carpal bones on radiographs. This classic x-ray finding is also known as the “Terry Thomas” sign, referring to the famous gap in the upper dental incisors of the late British comedian. The SLL is responsible for stabilizing the scapholunate joint, and this x-ray finding indicates disruption of the ligament. Patients with this degree of joint space widening will often require surgical repair to ensure best functional outcome, and in the short term the injury is managed with NSAIDS, splinting, and orthopedic hand referral.

Take-Home Points

  • Scapholunate ligament disruption can lead to long term arthritis and impaired wrist function. Early identification and treatment helps improve outcomes.

  • MRI may be needed to identify disruption of the scapholunate ligament. X-ray is approximately 63% sensitive in identifying the injury by demonstrating scapholunate space widening.

  • Kompoliti E, Prodromou M, Karantanas AH. SLAC and SNAC Wrist: The Top Five Things That General Radiologists Need to Know. Tomography. 2021 Sep 23;7(4):488-503. doi: 10.3390/tomography7040042. PMID: 34698283; PMCID: PMC8544666.
  • Wessel LE, Wolfe SW. Scapholunate Instability: Diagnosis and Management – Anatomy, Kinematics, and Clinical Assessment – Part I. J Hand Surg Am. 2023 Nov;48(11):1139-1149. doi: 10.1016/j.jhsa.2023.05.013. Epub 2023 Jul 14. PMID: 37452815.



By |2025-11-17T01:47:19-08:00Nov 17, 2025|Orthopedic, SAEM Clinical Images|

SAEM Clinical Images Series: A Case of Sudden Right Arm Pain and Deformity


popeye sign

A 73-year-old male presented to the Emergency Department with acute pain in his upper right arm. The pain began suddenly upon attempting to lift a 30-lb box that had been delivered to his house. He stated that as he began to lift the box, he felt a sudden pop coupled with the acute onset of pain. Since the injury, he had difficulty with flexion of his right upper extremity. He denied any other complaints.

Vitals: All vital signs are normal.

General: Alert and oriented, well appearing.

Chest: Heart and lung sounds are normal. Chest palpation is unremarkable.

Musculoskeletal: See provided images comparing right versus left upper arm appearance. The patient reports pain with right elbow range of motion. No bony tenderness is present. Flexion of the right upper extremity is limited on exam.

Neurologic: Sensation is intact throughout. The patient has weakness of right elbow flexion, but other tests of strength are preserved.

Non-contributory

The patient has a “Popeye sign” – a proximal biceps bulge at the anterior mid-arm level of his right arm.

The patient has a biceps tendon rupture of his right arm.

Patients with biceps tendon ruptures present with anterior upper arm pain, often after contraction against resistance. Ruptures of the proximal tendon are more common than distal ruptures. Risk factors include advanced age, male gender, chronic biceps tendinopathy, tobacco use, and obesity. Acute ecchymosis and swelling are common. Proximal ruptures such as in this case demonstrate a proximal muscular bulge at the anterior mid-arm level (known as the Popeye sign). Distal rupture can be examined with several maneuvers such as the hook test, supination pronation test,biceps squeeze test, and distal biceps provocation test, which overall have high sensitivity and specificity for diagnosing distal biceps tendon rupture. Proximal ruptures may be treated conservatively, though surgical repair options exist. For distal ruptures, definitive treatment is surgical intervention. Factors affecting recommendations for surgery include the location and severity of the tear (complete vs. partial), and the patient’s medical fitness. Though rare, rhabdomyolysis and compartment syndrome are possible complications.

Take-Home Points

  • Biceps tendon ruptures are usually due to forcible contraction against significant resistance.

  • Initial treatment can be conservative in the ED, though all biceps tendon ruptures require urgent outpatient orthopedic referral.

  • Kelly, Mick P., et al. “Distal Biceps Tendon Ruptures: An Epidemiological Analysis Using a Large Population Database.” The American Journal of Sports Medicine, vol. 43, no. 8, 2015, pp. 2012–17, https://doi.org/10.1177/0363546515587738.
  • Vishwanathan K, Soni K. Distal biceps rupture: Evaluation and management. J Clin Orthop Trauma. 2021 May 20;19:132-138. doi: 10.1016/j.jcot.2021.05.012. PMID: 34099972; PMCID: PMC8167284.

By |2025-10-26T13:32:30-07:00Oct 27, 2025|Orthopedic, SAEM Clinical Images|

SAEM Clinical Images Series: Pain and Swelling in a Roofer’s Right Wrist

A 27-year-old male with no significant past medical history presented to the ED due to right hand pain and swelling. The patient reported that he works as a roofer and felt severe, sharp pain in his right hand immediately after using a nail gun this morning. The pain was followed by gradual swelling of the right wrist and hand. There was no loss of sensation or bleeding from the injury site. He additionally denied any injury from the nail itself. The patient was in moderate pain but hemodynamically stable while in the ED.

Vitals: Temp 36.6 °C; BP 155/99; HR 71; RR 18; SpO2 99%

General: Alert, mild distress.

Musculoskeletal: No gross deformities to right hand, reduced right hand flexion/extension due to pain, normal ROM of right shoulder and elbow, pain with right forearm supination/pronation, swelling of right hand and fingers and diffusely tender carpal bones.

Non-contributory

Comminuted lunate fracture. Lunate fractures, especially comminuted lunate fractures, usually result from high-energy trauma, with an incidence ranging from only 0.5% to 6.5% of carpal fractures. Up to one-third of wrist fractures appear to be overlooked on traditional radiography. Further imaging should be warranted for patients who are clinically suspicious of wrist fractures in the ED. Multidetector Computed Tomography (MDCT) with multiplanar reformat capability is a useful method to identify occult wrist fractures.

The blood supply of the lunate bone comes from the palmar and medial arteries of the carpometacarpal branch of the radial artery. Damage to the artery may lead to avascular necrosis (Kienböck disease). Comminuted lunate fractures may result in severe intraosseous destruction of vasculature, increasing the risk of lunate bone necrosis. An at-risk nerve is the median nerve, which runs through the carpal tunnel. If the lunate is fractured or displaced, it may compress or damage the median nerve, resulting in pain, paresthesia, or sensory loss in the palmar surface of the thumb, index, and middle fingers and radial half of the ring finger.

Take-Home Points

  • Associated risk factors for a lunate fracture include occupations or sports involving repetitive pressure to the base of the hand with the wrist in extension (eg, roofer, gymnast, jack-hammer operator).

  • Due to complex carpal anatomy, traditional radiography may not be sufficient to detect lunate fractures.

  • At-risk structures that require evaluation in the case of lunate fracture include the palmar and medial branches of the radial artery and the median nerve.

  • Li, Jun, et al. “Comminuted lunate fracture combined with distal radius fracture and scaphoid fracture: A case report.” Medicine, vol. 102, no. 29, 2023, https://doi.org/10.1097/md.0000000000034393.

  • Balci, Ali, et al. “Wrist fractures: Sensitivity of radiography, prevalence, and patterns in MDCT.” Emergency Radiology, vol. 22, no. 3, 2014, pp. 251–256, https://doi.org/10.1007/s10140-014-1278-1.

  • Geissler, William B. “Carpal fractures in athletes.” Clinics in Sports Medicine, vol. 20, no. 1, 2001, pp. 167–188, https://doi.org/10.1016/s0278-5919(05)70254-4.

By |2025-04-28T14:39:34-07:00May 2, 2025|Orthopedic, SAEM Clinical Images|

SAEM Clinical Images Series: Weird Flex

tenosynovitis

A 29-year-old female with a history of depression, anxiety, and tobacco use disorder presented with worsening right index finger pain, swelling, and redness for the previous three days. Additionally, she reported that she was unable to further flex or extend her finger. She denied fevers, chills, rashes, or recent illness. There was no history of trauma, aquatic or other environmental exposures, insect bites, or intravenous drug use. She did note that she uses a copper brillo pad to clean her dishes at home which often causes small abrasions to her fingers.

Vitals: BP 160/112; PR 73; Temp 36.4°C; RR 18; SpO2 100% on RA

General: Well-appearing, no acute distress.

Cardiovascular: Right index finger capillary refill <2 sec.

Skin: Right index finger uniformly edematous and erythematous with tenderness to palpation along the tendon sheath; small healed abrasions over distal palmar aspect of the digit; no focal area of fluctuance.

MSK: right index finger held in flexion, pain with passive extension.

WBC: 8.6

ESR: 129

CRP: 105.5

This patient has flexor tenosynovitis, an infection of the synovial sheath surrounding the flexor tendon of the hand. The condition is usually caused by local inoculation from penetrating trauma although can also result from hematogenous spread. Flexor tenosynovitis is considered a surgical emergency, as delayed intervention can lead to significant morbidity including tendon rupture, deep space infection, abscess development, soft tissue necrosis, amputation, and/or chronically compromised hand function. Diagnosis is usually clinical, based on history and physical exam findings; however, laboratory evaluation may reveal leukocytosis and/or elevated inflammatory markers. If there is a history of penetrating trauma, x-rays of the affected digit are recommended to rule out retained foreign body. Management in the ED includes prompt surgical consultation and broad-spectrum antibiotics against common cutaneous pathogens. Antibiotic coverage should be broadened in patients with a history of marine exposure or Pseudomonal risk factors including immunocompromised status.

Flexor tenosynovitis presents with four classic exam findings called “Kanavel Signs.” Kanavel Signs include (1) flexion of the involved digit, (2) tenderness to palpation over the tendon sheath, (3) pain with passive extension, and (4) uniform swelling of the finger. The presence of all four Signs has a sensitivity for flexor tenosynovitis as high as 97.1%, although early in the course of infection, pain with passive extension may be the only finding.

Take-Home Points

  • Flexor tenosynovitis is an infection of the flexor tendon sheath of the hand and a history of trauma or penetrating injury to the area should raise suspicion.

  • Flexor tenosynovitis is a “can’t miss” clinical diagnosis in the ED as there is a risk of significant complications with delayed antibiotics and surgical intervention.

  • Infection can reliably be identified by the presence of the four Kanavel Signs on physical exam.

  • Chan E, Robertson BF, Johnson SM. Kanavel signs of flexor sheath infection: a cautionary tale. Br J Gen Pract. 2019 Jun;69(683):315-316. doi: 10.3399/bjgp19X704081. PMID: 31147342; PMCID: PMC6532803.

  • Chapman T, Ilyas AM. Pyogenic Flexor Tenosynovitis: Evaluation and Treatment Strategies. J Hand Microsurg. 2019 Dec;11(3):121-126. doi: 10.1055/s-0039-1700370. Epub 2019 Nov 2. PMID: 31814662; PMCID: PMC6894957.

  • Hermena S, Tiwari V. Pyogenic Flexor Tenosynovitis. In: StatPearls. StatPearls Publishing; 2022.

  • Kennedy CD, Huang JI, Hanel DP. In Brief: Kanavel’s Signs and Pyogenic Flexor Tenosynovitis. Clin Orthop Relat Res. 2016 Jan;474(1):280-4. doi: 10.1007/s11999-015-4367-x. Epub 2015 May 29. PMID: 26022113; PMCID: PMC4686527.

By |2025-03-30T20:30:57-07:00Apr 7, 2025|Orthopedic, SAEM Clinical Images|

SAEM Clinical Images Series: An Unusual Arm Conundrum

shoulder

A 58-year-old female with a past medical history significant for osteoporosis presented with right shoulder pain after a witnessed mechanical fall down two stairs. She sustained no headstrike or loss of consciousness. She endorses severe right shoulder pain without numbness/tingling over any part of her arm. Since the fall, she has been unable to move her arm, which remains abducted overhead.

General: Right arm fixed, abducted position and elevated over her head.

Vascular: 2-second capillary refill in all nail beds, strong palpable radial pulse.

Neuro: Sensation intact to light touch on medial and lateral aspects of all distal digits, and throughout entire axillary, radial, ulnar and median nerve distribution.

Motor: Flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) intact in digits 2 through 5. Extensor digitorum communis (EDC) and extensor indicis proprius (EIP) intact. Normal finger abduction and adduction. Normal thumb opposition. Normal OK sign. Wrist flexors and extensors intact.

Luxatio erecta (inferior shoulder dislocation) is a rare type of shoulder dislocation. The majority of shoulder dislocations are anterior (over 95%), with a smaller number being posterior (2-4%). Inferior dislocations are the least common injury pattern (0.5%), but prompt identification and treatment are crucial due to the high risk of neurovascular damage.  Radiographs will typically demonstrate the humeral head lying inferior to the glenoid fossa, with the humeral shaft parallel to the spine of the scapula. Classically, the entire arm is held in abduction.

Inferior shoulder dislocation most commonly occurs either due to hyperabduction of the shoulder (such as when grasping at a tree branch above while falling) or through an axial load from above on a hyperabducted arm (as seen in falls or motor vehicle accidents). Patients presenting with inferior shoulder dislocation are at substantial risk for neurovascular compromise, particularly of the axillary nerve, leading to impaired upper extremity movement and sensation. Due to the substantial injury mechanism, patients with inferior shoulder dislocations are also at increased risk for rotator cuff pathology. Treatment of inferior shoulder dislocation is immediate closed reduction to reduce the risk of neurovascular complications. Once reduced, the arm should be placed in an immobilizer to prevent recurrent dislocation.

Take-Home Points

  • Patients with inferior shoulder dislocations often present holding their arm above their head. Often, patients cannot adduct their arm.

  • Axillary nerve injuries occur in about 60% of inferior dislocations. Compared to other dislocations, inferior dislocations have the highest incidence of axillary nerve injuries.

  • Patients with inferior dislocations often present with neurovascular compromise of the affected arm, so be sure to do a thorough exam after reduction.

  • Grate I Jr. Luxatio erecta: a rarely seen, but often missed shoulder dislocation. Am J Emerg Med. 2000 May;18(3):317-21. doi: 10.1016/s0735-6757(00)90127-x. PMID: 10830689.

  • Nambiar M, Owen D, Moore P, Carr A, Thomas M. Traumatic inferior shoulder dislocation: a review of management and outcome. Eur J Trauma Emerg Surg. 2018 Feb;44(1):45-51. doi: 10.1007/s00068-017-0854-y. Epub 2017 Oct 3. Erratum in: Eur J Trauma Emerg Surg. 2018 Feb;44(1):53. doi: 10.1007/s00068-017-0878-3. PMID: 28975397.

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