PEM POCUS Series: Hip Effusion

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


PATIENT CASE: Child with a Limp

Sarah is a 4-year-old girl who comes into the emergency department complaining of a limp for the last day. She had an upper respiratory infection which started a week ago for which she had been taking acetaminophen and ibuprofen with her last dose of either being 2 days ago. Those symptoms have improved. Yesterday, she started complaining of diffuse right leg pain primarily at her hip, thigh, and knee. Today, her parents noted she was walking with a limp.

On arrival, her vital signs are:

Vital SignFinding
Temperature100.1F
Heart rate100 bpm
Blood pressure97/50
Respiratory rate19
Oxygen saturation (room air)100%

She is well appearing and walks with an antalgic gait favoring the left leg. She has a normal HEENT, neck, cardiac, respiratory, abdominal, and back examination. She points to her right anterior thigh when you ask her where her pain is. She has limited range of motion with internal and external rotation of her right hip and complains of pain. She cries when you palpate any part of her leg, but is able to range her knee, ankle, and foot fully. She has 2+ dorsalis pedis and posterior tibialis pulses and intact sensation to light touch throughout. 

Given her pain with range of motion at her hip, you order a hip radiograph, but while waiting for it, decide to perform a hip point of care ultrasound (POCUS) examination.

PEDIATRIC HIP EFFUSION: Ultrasound Technique

It can be difficult for children to locate the exact area of pain and often hip pain can present with referred knee and thigh pain. A thorough physical examination along with hip POCUS can help localize the area of discomfort. When we use POCUS to evaluate the hip, we are primarily looking for a joint effusion in the synovial space. This is best visualized anterior to the femoral neck.  

hip anatomy hip effusion
Figure 2. Hip anatomy with target landmark being the femoral neck (red arrow) 

Technique

  1. The patient should be positioned supine.
    • Depending on the age of the child, the child can be positioned supine in the guardian’s lap while undergoing the examination. 
    • Offering the child a toy, book, or phone/tablet for distraction during the examination can also help ease anxiety.
  2. Use a linear high frequency transducer with a wide footprint.
  3. Place the transducer along the anterior hip.
    • Use the greater trochanter as a lateral landmark and place the probe on top of the femoral head and neck (Figure 3)
  4. Aim the probe marker towards the patient’s umbilicus.
hip effusion ultrasound
Figure 3. Linear transducer at the hip with probe marker (red dot) aimed towards the patient’s umbilicus
  1. Identify the anatomical landmarks on ultrasound (figure 4) 
    • Hip muscles: Sartorius, quadriceps, and iliopsoas
    • Bones: Femoral head, femoral neck
  2. The area of interest in looking for a hip effusion is the synovial space anterior to the femoral neck and NOT anterior to the femoral head. This area is also referred to as the anterior synovial recess.
Figure 4. Ultrasound image showing the normal landmarks for a pediatric hip without an effusion and the location of the femoral head (X) and synovial space (circle) with the linear transducer positioned overlying and longitudinal to the femoral neck
  • Tips:
    • It is often helpful to ultrasound the unaffected side as a comparison.
    • Be aware of the patient’s comfort throughout the examination.

ABNORMAL ULTRASOUND FINDINGS

A hip effusion will appear anechoic (black) in the synovial space anterior to the femoral neck (anterior synovial recess). Measure the distance between the anterior surface of the femoral neck and the posterior surface of the iliopsoas muscle. Examples are illustrated in figures 5 and 6.

hip effusion PEM POCUS ultrasound

There have been different methods used to assess if an effusion is present including:​1,2​

  • Measured effusion is >0.5 cm 
  • Measured effusion with >0.2 cm difference compared to the contralateral hip
  • Gestalt view with the anterior synovial recess areas appearing asymmetric compared to the other hip

Limitations of the Hip POCUS

Note that hip POCUS does not tell you the cause of an effusion but rather only whether an effusion is present or not. Effusions can result from infectious, inflammatory, and traumatic etiologies, and thus it is important to take into account the context of the patient’s presentation. 

References

  1. Vieira R, Levy J. Bedside ultrasonography to identify hip effusions in pediatric patients. Ann Emerg Med. 2010;55(3):284-289. PMID 19695738
  2. Cruz C, Vieira R, Mannix R, Monuteaux M, Levy J. Point-of-care hip ultrasound in a pediatric emergency department. Am J Emerg Med. 2018;36(7):1174-7. PMID 29223689 

FACTS and LITERATURE REVIEW

There have been multiple case reports of hip POCUS identifying hip effusions in children with fractures, septic joints, and in the work up of children with limps.​1–3​ There are limited studies examining the accuracy of hip POCUS compared to radiology-performed ultrasound in children (table 1).

StudyNSensitivitySpecificityComments
Vieira et al., Ann Emerg Med, 2010​4​2885%93%If the pediatric emergency physician had a high confidence in ultrasound accuracy, the sensitivity increased to 90% and specificity to 100%
Cruz et al., Am J Emerg Med, 2018​5​51685%98%For each additional hip POCUS performed, the odds of an accurate scan increased by 2.4%. 
Table 1. Published studies comparing pediatric hip POCUS to radiology-performed ultrasound

 

References [click to expand] +

  1. Deanehan J, Gallagher R, Vieira R, Levy J. Bedside hip ultrasonography in the pediatric emergency department: a tool to guide management in patients presenting with limp. Pediatr Emerg Care. 2014;30(4):285-287. PMID 24694889
  2. Garrison J, Nguyen M, Marin J. Emergency Department Point-of-Care Hip Ultrasound and Its Role in the Diagnosis of Septic Hip Arthritis: A Case Report. Pediatr Emerg Care. 2016;32(8):555-557. PMID 27490732
  3. Tsung J, Blaivas M. Emergency department diagnosis of pediatric hip effusion and guided arthrocentesis using point-of-care ultrasound. J Emerg Med. 2008;35(4):393-399. PMID 18403170 
  4. Vieira R, Levy J. Bedside ultrasonography to identify hip effusions in pediatric patients. Ann Emerg Med. 2010;55(3):284-289. PMID 19695738
  5. Cruz C, Vieira R, Mannix R, Monuteaux M, Levy J. Point-of-care hip ultrasound in a pediatric emergency department. Am J Emerg Med. 2018;36(7):1174-1177. PMID 29223689 

CASE RESOLUTION

The patient’s hip plain film radiographs are unremarkable. You decide to incorporate hip POCUS to your evaluation. You place a linear, high-frequency transducer and visualize the patient’s bilateral hips. You observe the following:

Right Hip (Affected Side) POCUS Video and Key View

Though the child complained of hip, knee, and thigh pain, your POCUS evaluation identifies a right hip effusion which helps you narrow the location of her pain.

Video 1. A hip POCUS of the case patient’s right hip (affected side)

 

PEM POCUS hip effusion
Figure 7. Right (affected side) hip POCUS with a hip effusion measuring 0.77 cm

Left Hip (Normal Side) POCUS Video and Key View

Video 2. A hip POCUS of the case patient’s left hip (unaffected side) for comparison

 

PEM POCUS hip no effusion normal
Figure 8. Left (unaffected side) hip POCUS with no effusion

ED Course

The patient’s labs result, and she has reassuring labs, which include a serum WBC 8.3 x109/L and ESR 34 mm/hr. The patient receives ibuprofen during her visit and within 1 hour is able to walk without a significant limp and states she feels better. The patient’s family notes they have spent the last few weeks of summer in a Lyme-endemic region, and so you send off Lyme titers.

Given the resolution of limp, lack of fever, and reassuring lab values, you do not believe the patient has a septic joint. Her effusion is more likely the result of a transient tenosynovitis. You recommend close pediatrician follow-up.

Pediatrician Clinic Follow-Up

At her pediatrician clinic visit 1 week later, her Lyme titers return negative, and the patient continues to be limp-free.  

 

The PEM POCUS series was created by the UCSF Division of Pediatric Emergency Medicine to help advance pediatric care by the thoughtful use of bedside ultrasonography.

Read other PEM POCUS tutorials. Learn more about bedside ultrasonography on the ALiEM Ultrasound for the Win series.

By |2021-07-21T18:55:01-07:00May 17, 2021|Orthopedic, PEM POCUS, Ultrasound|

SplintER Series: What is Wrong With My Daughter?

 

A 16 year-old competitive gymnast presents to the emergency department with left ankle pain for several weeks and missed periods. The mother provides consent to treat the patient and informs you she is concerned that with the patient’s missed periods, she may be pregnant. You obtain x-rays of her ankle (Figure 1).

Figure 1. Case courtesy of Dr Hani Makky ALSALAM, Radiopaedia.org, rID: 8720

 

Stress fracture at the distal tibial metaphysis – note the faint sclerotic line at the tibial metaphysis (Figure 2).

Figure 2. Arrows identifying the stress fracture. Case courtesy of Dr. Hani Makky Al Salam, Radiopaedia.org, rID: 8720

When coupled with the amenorrhea, consider the female athlete triad.

  • PEARL: The female athlete triad is a syndrome consisting of disordered eating, amenorrhea, and low bone mineral density (eg. osteoporosis) – Patients will have a degree of dysfunction from all 3 of the components. This is a fairly common disorder in young female athletes but the actual prevalence is hard to estimate because of the complexity of the three components [1]. Studies have shown a range from 0-16% when encompassing all three but can be as high as 4-18% when using two concurrent components and even 16-54% when only looking for one [2,3].

  • PEARL: Stress fractures in competitive athletes is usually multifactorial – increased activity, poor nutrition, and possible hormone imbalance [4,5].

Plain film ankle views should be obtained. If a stress fracture is acute, sensitivity on plain films can be as low as 10% [6]. MRI can be performed outpatient with a sensitivity approaching 100% [4,5,7,8]. A pregnancy test should be performed as well given the amenorrhea. A standard workup for amenorrhea should be performed as an outpatient. Inquire about eating habits and anxiety/depression.

  • PEARL: Athletes, regardless of competition level and gender, may be pushed into decreasing caloric intake for the sake of performance, appearance, or making weight. This can have serious physical and mental implications.

The three components of the female triad are on a spectrum of severity in the disruption of bone mineral density/osteoporosis, menstrual dysfunction/dysmenorrhea, and low energy with or without an eating disorder [1,9-11]. Patients will have a degree of dysfunction of all three components.

  • PEARL: Risk factors for developing the female athlete triad are participation in sports that emphasize leanness or a specific weight, appearance, or are beneficial if less gravitational forces. These may include gymnastics, ice skating, wrestling, boxing, dance, and track [10,12].

Stress fracture treatment included rest and analgesics. Immobilization is not necessary, but refraining from activity which exacerbates pain is crucial. NSAIDs may be used for pain control [5,7]. Female athlete triad is multifactorial and outpatient follow up should be ensured. Referral to adolescent medicine, sports medicine, or close primary care follow up is important.

  • PEARL: The patient will need education on good eating habits and nutrition, decrease in activity, and counseling [1,10,12]. The best way to treat the female athlete triad is to prevent it.

Check out ALiEM’s SplintER Series to brush up on other can’t miss diagnoses of ankle pain.

References

  1.  Weiss Kelly AK, Hecht S; COUNCIL ON SPORTS MEDICINE AND FITNESS. The Female Athlete Triad. Pediatrics. 2016;138(2):e20160922. PMID: 27432852.
  2. Nichols JF, Rauh MJ, Lawson MJ, Ji M, Barkai HS. Prevalence of the female athlete triad syndrome among high school athletes. Arch Pediatr Adolesc Med. 2006;160(2):137-142. doi:10.1001/archpedi.160.2.137. PMID: 16461868.
  3. Hoch AZ, Pajewski NM, Moraski L, et al. Prevalence of the female athlete triad in high school athletes and sedentary students. Clin J Sport Med. 2009;19(5):421-428. doi:10.1097/JSM.0b013e3181b8c136. PMID: 19741317.
  4. Matcuk GR Jr, Mahanty SR, Skalski MR, Patel DB, White EA, Gottsegen CJ. Stress fractures: pathophysiology, clinical presentation, imaging features, and treatment options. Emerg Radiol. 2016;23(4):365-375. PMID: 27002328.
  5. Saunier J, Chapurlat R. Stress fracture in athletes. Joint Bone Spine. 2018;85(3):307-310. PMID: 28512006.
  6. Matheson GO, Clement DB, McKenzie DC, Taunton JE, Lloyd-Smith DR, MacIntyre JG. Stress fractures in athletes. A study of 320 cases. Am J Sports Med. 1987;15(1):46-58. doi:10.1177/036354658701500107. PMID: 3812860.
  7. Denay KL. Stress Fractures. Curr Sports Med Rep. 2017;16(1):7-8. PMID: 28067732.
  8. McInnis KC, Ramey LN. High-Risk Stress Fractures: Diagnosis and Management. PM R. 2016;8(3 Suppl):S113-S124. PMID: 26972260.
  9. Otis CL, Drinkwater B, Johnson M, Loucks A, Wilmore J. American College of Sports Medicine position stand. The Female Athlete Triad. Med Sci Sports Exerc. 1997;29(5):i-ix. PMID: 9140913.
  10. Nattiv A, Loucks AB, Manore MM, et al. American College of Sports Medicine position stand. The female athlete triad. Med Sci Sports Exerc. 2007;39(10):1867-1882. PMID: 17909417.
  11. Sundgot-Borgen J. Risk and trigger factors for the development of eating disorders in female elite athletes. Med Sci Sports Exerc. 1994;26(4):414-419.PMID: 8201895.
  12. Scofield KL, Hecht S. Bone health in endurance athletes: runners, cyclists, and swimmers. Curr Sports Med Rep. 2012;11(6):328-334. PMID: 23147022.

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By |2021-04-10T10:24:46-07:00Apr 5, 2021|EMRad, Orthopedic, Pediatrics, Radiology, Trauma|

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