Tag Archives: pocus

Alternative Rib Fracture Management in the ED

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Alternative Rib Fracture Management in the ED – A Medical Student Clinical Pearl

Victoria Mercer, Clinical Clerk 3, DMNB

Reviewed and Copyedited by Dr. Mandy Peach

Rib fractures are a frequent presentation in the ED, occuring in approximately 10% of all injured patients with the primary causes being blunt chest trauma and MVAs(1,2).  The mainstay of treatment for rib fractures is analgesic control(1). When pain cannot be adequately managed, the patient is at a heightened risk of hypoventilation due to decreased thoracic mobility and secretion clearance, predisposing the patient to significant atelectasis(1,2).

Historically the pain from rib fractures has been managed with acetaminophen or NSAIDS and if these do not sufficiently alleviate the pain, opioids are used(1,3). Unfortunately, these methods often do not provide adequate pain control or in the case of opioids, come with a myriad of side effects such as nausea, vomiting, constipation, respiratory depression and the potential for dependency and abuse (1,4).

An alternative to traditional methods include regional techniques such as paravertebral or epidural nerve blocks. These interventions have been shown to effectively control pain in rib fractures(3,4). The downside to these interventions include being technically challenging and time consuming with significant complication risks and contraindications such as coagulation disorders (1,3).

The solution? A serratus anterior block 

An ultrasound guided blockade of the lateral cutaneous branches of the thoracic intercostal nerves was first described by Blanco et al. in 2013 for patients following breast surgery to manage their postoperative pain(5). This procedure has been adopted by many emergency departments for its convenience and practicality compared to epidural or paravertebral nerve blocks(3).

Serratus anterior blocks are less invasive and considerably more practical in the ED setting, providing paresthesia to the ipsilateral hemithorax for 12-36 hours (6).

The only absolute contraindications are patient refusal, allergy to local anesthetic and local infection(1).

Complications of a serratus anterior block include pneumothorax, vascular puncture, nerve damage, failure/inadequate block, local anesthetic toxicity and infection(1).

Serratus anterior blocks are only effective for the anterior two-thirds of the chest wall (3).

 

Figure 1. Ultrasound image of serratus anterior muscle and surrounding tissues with superficial or deep needle guides. Image from Thiruvenkatarajan V, Cruz Eng H, Adhikary SD. An update on regional analgesia for rib fractures. Current Opinion in Anaesthesiology. 2018;31(5):601–607.

How do you do it?

The procedure is usually performed with the patient laying supine however the patient could also lay in a lateral decubitus position (1,3). Using a high frequency linear ultrasound probe (6-13MHz), identify the serratus anterior and latissimus dorsi muscles over the fifth rib in the mid-axillary line(1,3). Using an in-plane approach, insert the needle either superficial or deep to the serratus anterior and confirm correct needle placement by visualizing anaesthetic spread via ultrasound(1,3). According to May et al., superficial spreading tends to have a longer lasting analgesic effect(1). Place and secure a catheter to infuse the remainder of the bolus(1,3). Thiruvenkatarajan et al. recommend a bolus of 40ml of 0.25% levobupivacaine and a 50mm 18G Tuohy catheter needle(3).

See this excellent review by Dr. David Lewis on identifying rib fractures and their complications using ultrasound (start 3:08) as well as a review of the block and procedure (start 8:00)

Rib Fractures and Serratus Anterior Plane Block

References

  1.         May L, Hillermann C, Patil S. Rib fracture management. BJA Education. 2016 Jan 1;16(1):26–32.
  2.         Malekpour M, Hashmi A, Dove J, Torres D, Wild J. Analgesic choice in management of rib fractures: Paravertebral block or epidural analgesia? Anesthesia and Analgesia. 2017 Jun 1;124(6):1906–11.
  3.         Thiruvenkatarajan V, Cruz Eng H, Adhikary S das. An update on regional analgesia for rib fractures. Vol. 31, Current opinion in anaesthesiology. 2018. p. 601–7.
  4.         Tekşen Ş, Öksüz G, Öksüz H, Sayan M, Arslan M, Urfalıoğlu A, et al. Analgesic efficacy of the serratus anterior plane block in rib fractures pain: A randomized controlled trial. American Journal of Emergency Medicine. 2021 Mar 1;41:16–20.
  5.         Blanco R, Parras T, McDonnell JG, Prats-Galino A. Serratus plane block: A novel ultrasound-guided thoracic wall nerve block. Anaesthesia. 2013 Nov;68(11):1107–13.
  6.         Mayes J, Davison E, Panahi P, Patten D, Eljelani F, Womack J, et al. An anatomical evaluation of the serratus anterior plane block. Anaesthesia [Internet]. 2016 Sep 1 [cited 2021 Apr 18];71(9):1064–9. Available from: http://doi.wiley.com/10.1111/anae.13549

 

 

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PoCUS & COVID Severity

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Dal PoCUS Fellowship Journal Club March 2021

Dr. Mandy Peach

PoCUS Fellow

Dalhousie University Department of Emergency Medicine

Zieleskiewicz L, Markarian T, Lopez A, Taguet C, Mohammedi N, Boucekine M, Baumstarck K, Besch G, Mathon G, Duclos G, Bouvet L, Michelet P, Allaouchiche B, Chaumoître K, Di Bisceglie M, Leone M; AZUREA Network. Comparative study of lung ultrasound and chest computed tomography scan in the assessment of severity of confirmed COVID-19 pneumonia. Intensive Care Med. 2020 Sep;46(9):1707-1713. doi: 10.1007/s00134-020-06186-0. Epub 2020 Jul 29. PMID: 32728966; PMCID: PMC7388119.

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Rib Fractures and Serratus Anterior Plane Block

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Saint John EM Rounds – March 2021

Dr. David Lewis

@e_med_doc

 

View PDF here

Further Reading and Links

 

 

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Scaphoid Fracture – Can PoCUS disrupt the traditional ‘splint and wait’ pathway?

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PoCUS Fellow Pearl

Dr. Melanie Leclerc, CCFP-EM

MSK PoCUS Fellow

Dalhousie University Department of Emergency Medicine

 

Reviewed & Edited by Dr David Lewis (@e_med_doc)

All case histories are illustrative and not based on any individual

 

Case:

A 37 year old, right hand dominant, carpenter presents to your local ED with a complaint of right wrist pain. He was on a step-stool and lost his balance earlier today. He fell landing on his outstretched arm and had an acute-onset of radial-sided wrist pain. He denies any other injury. There are no neurologic complaints.

On exam, there is no visible deformity. The skin is closed and there is some swelling noted. The patient is tender over the anatomic snuff box as well as volarly over the scaphoid. There is pain noted with axial loading of the thumb. There is no other tenderness. ROM is within normal limits. The limb is distally neurovascularly intact.

X-rays are normal.

An occult scaphoid fracture is suspected. At this institution, patients with suspected occult scaphoid fracture are placed in a thumb spica splint and referred to the local hand surgeon to be seen in ~10-14 days for repeat assessment and X-ray.

Can Point of Care Ultrasound change this traditional “splint and wait” patient pathway?

 

Background:

Scaphoid fracture is a common presentation to the Emergency Department accounting for approximately 15% of all wrist injuries and 70% of carpal fractures. Up to 30% of the time, radiographs at initial presentation appear normal making fracture a commonly missed injury for Emergency physicians. A failure to recognize this injury can lead to chronic pain and functional impairment for patients. Particularly, fractures of the proximal pole (most distant to the blood supply) can lead to avascular necrosis (AVN) at high rates. Non-union can lead to scaphoid non-union advanced collapse (SNAC wrist) which can perpetuate further degenerative changes throughout the carpus. This can cause a significant impact on quality of life and occupation. Early detection of fracture could expedite fixation and possibly results in better outcomes. Further study in this area is needed.

 

Anatomy:

The scaphoid bone lies in the radial aspect of the proximal carpal row. It’s unique shape (“twisted peanut”), lends to easy recognition. It articulates proximally with the distal radius, distally with the trapezium, and on its’ ulnar aspect with the lunate to form the scapho-lunate interval. The blood supply to the scaphoid is unique in that the majority of it is retrograde. The dorsal carpal branch of the radial artery supplies the bone from distal to proximal. A small proportion of the blood supply originates at the proximal end. The boundary between the two supplies creates a “watershed” area prone to non-union and AVN.

 

Classification of Fractures:

Scaphoid fractures are classified by location. These regions are the proximal, middle and distal thirds which account for 20%, 75%, and 5% of the fractures respectively. The stability of fractures is determined by the displacement (>1mm) and angulation (scapholunate angle >60 and radiolunate angle >15). The Hebert Classification as endorsed by Traumapedia can be found below.

 

Traditional Imaging:

Imaging of these suspected injuries varies. Traditionally serial X-rays were used, but have been found to be poorly sensitive even several weeks after injury. Bone scan has also been used as an alternative due to it’s high sensitivity, but has poor specificity and provides no further information regarding the nature of the fracture. CT is relatively sensitive and specific and provides information for pre-operative planning. MRI is considered the gold standard, but is difficult to obtain in a timely manner in Canada.

Bäcker HC, Wu CH, Strauch RJ. Systematic Review of Diagnosis of Clinically Suspected Scaphoid Fractures. J Wrist Surg. 2020 Feb;9(1):81-89. doi: 10.1055/s-0039-1693147. Epub 2019 Jul 21. PMID: 32025360; PMCID: PMC7000269.

 

PoCUS Technique:

  • Linear probe

  • Consider waterbath, gel standoff pad, or bag of IV fluid

  • Scan with the wrist ulnarly deviated

  • Scan in the longitudinal and transverse orientations of volar, lateral and dorsal aspects

  • Place the probe in longitudinal orientation dorsally over lister’s tubercle of the radius and scan distally until the scaphoid is visualized in the snuff box. Scan radial to ulnar.

  • Rotate to the transverse orientation and scan through proximal to distal

  • Volarly, in the transverse plane, identify the tendon of the flexor carpi radialis (this lies radial to the easily identifiable palmaris longus tendon on exam). The scaphoid is found deep to this. Scan proximal to distal.

  • Rotate to the longitudinal orientation and scan radial to ulnar

 

 

Video Demonstration:

 

 

Findings:

  • Cortical disruption

  • Periosteal elevation

  • Hematoma

 

The Evidence:

  • Early advanced imaging (CT or MRI) compared to initial 2 week immobilisation proved more cost effective and had better patient oriented outcomes (ie. missed work).(7)
  • A systematic review and meta analysis of moderate to high quality studies published in 2018 found that ultrasound had a mean sensitivity of ~89% and specificity of ~90% for detection of occult scaphoid fractures.(1)
  • Similar results were also reported by another systematic review in 2018.(8)
  • Pocus was shown to have a comparable sensitivity to CT for occult scaphoid in a systematic review published in 2020.(2)

 

Limitations:

  • Only useful if positive
  • Operator experience dependent
  • US probe and frequency dependant
  • Potential for false positives due to injury of nearby structure causing hematoma
  • Potential for false positives in context of arthritis or remote trauma

 

Bottom line:

  • Useful if positive
  • Still need definitive test to further delineate fracture (ie: for operative planning)
  • Could expedite CT
  • Could expedite specialist follow-up
  • May improve ER physician diagnostic certainty
  • May improve patient trust and compliance with splinting
  • Further study is needed

 

Case Conclusion:

Scaphoid cortical disruption was visualized using PoCUS. After discussion with the hand surgeon, a CT Scan of the wrist was performed which confirmed a minimally displaced waste fracture of the scaphoid. The patient was splinted and seen the next day in clinic for discussion regarding operative management.

 

Further Review:

 

 

 

References

  1. Ali M, Ali M, Mohamed A, Mannan S, Fallahi F. The role of ultrasonography in the diagnosis of occult scaphoid fractures J Ultrason 2018; 18: 325–331.
  2. Bäcker HC, Wu CH, Strauch RJ. Systematic Review of Diagnosis of Clinically Suspected Scaphoid Fractures. J Wrist Surg. 2020 Feb;9(1):81-89.
  3. Bakur A. Jamjoom, Tim R.C. Davis. Why scaphoid fractures are missed. A review of 52 medical negligence cases, Injury, Volume 50, Issue 7, 2019, Pages 1306-1308.
  4. Carpenter CR et al. Adult Scaphoid Fracture. Acad Emerg Med 2014; 21(2): 101-121.
  5. Gibney B, Smith B, Moughty A, Kavanagh EC, Hynes D and MacMahon PJ American Journal of Roentgenology 2019 213:5, 1117-1123
  1. Jenkins PJ, Slade K, Huntley JS, Robinson CM. A comparative analysis of the accuracy, diagnostic uncertainty and cost of imaging modalities in suspected scaphoid fractures. Injury. 2008;39:768–774.
  2. Karl, John W. MD, MPH1; Swart, Eric MD1; Strauch, Robert J. MD1 Diagnosis of Occult Scaphoid Fractures, The Journal of Bone and Joint Surgery: November 18, 2015 – Volume 97 – Issue 22 – p 1860-1868.
  3. Kwee, R.M., Kwee, T.C. Ultrasound for diagnosing radiographically occult scaphoid fracture. Skeletal Radiol 47, 1205–1212 (2018).
  4. Malahias MA, Nikolaou VS, Chytas D, Kaseta MK, Babis GC. Accuracy and Interobserver and Intraobserver Reliability of Ultrasound in the Early Diagnosis of Occult Scaphoid Fractures: Diagnostic Criteria and a Way of Interpretation. Journal of Surgical Orthopaedic Advances. 2019 ;28(1):1-9.
  5. Mallee WH, Wang J, Poolman RW, Kloen P, Maas M, de Vet HCW, Doornberg JN. Computed tomography versus magnetic resonance imaging versus bone scintigraphy for clinically suspected scaphoid fractures in patients with negative plain radiographs. Cochrane Database of Systematic Reviews 2015, Issue 6.
  6. Mallee, W.H., Mellema, J.J., Guitton, T.G. et al. 6-week radiographs unsuitable for diagnosis of suspected scaphoid fractures. Arch Orthop Trauma Surg 136, 771–778 (2016).
  7. Melville, D., Jacobson, J.A., Haase, S. et al. Ultrasound of displaced ulnar collateral ligament tears of the thumb: the Stener lesion revisited. Skeletal Radiol 42, 667–673 (2013).
  8. Meyer, P., Lintingre, P.-F., Pesquer, L., Poussange, N., Silvestre, A., & Dallaudiere, B. (2018). Imaging of Wrist Injuries: A Standardized US Examination in Daily Practice. Journal of the Belgian Society of Radiology, 102(1), 9.
  9. Mohomad et al. 2019. Accuracy of the common practice of doing X-rays after two weeks in detecting scaphoid fractures. A retrospective cohort study. Hong Kong Journal of Orthopaedic Research 2019; 2(1): 01-06.
  10. Neubauer J, Benndorf M, Ehritt-Braun C, et al. Comparison of the diagnostic accuracy of cone beam computed tomography and radiography for scaphoid fractures. Sci Rep 2018; 8:3906.
  11. Ravikant Jain, Nikhil Jain, Tanveer Sheikh, Charanjeet Yadav. 2018. Early scaphoid fractures are better diagnosed with ultrasonography than X-rays: A prospective study over 114 patients, Chinese Journal of Traumatology, Volume 21, Issue 4, Pages 206-210.
  12. Senall, JA, Failla, JM, Bouffard, JL. 2004. Ultrasound for the early diagnosis of clinically suspected scaphoid fracture. J Hand Surg Am, 29:400-405.
  13. https://essr.org/content-essr/uploads/2016/10/wrist.pdf
  14. http://www.bonetalks.com/scaphoid
  15. https://radiopaedia.org/articles/scaphoid-fracture
  16. https://sketchymedicine.com/2014/07/scaphoid-bone-anatomy-and-fractures/
  17. https://radiopaedia.org/cases/scaphoid-fracture-11?lang=gb
  18. https://www.orthobullets.com/hand/6034/scaphoid-fracture
  19. https://meeting.handsurgery.org/abstracts/2018/EP15.cgi
  20. https://www.researchgate.net/figure/Bone-scintigraphy-patient-C-of-the-hands-the-patient-with-a-scaphoid-fracture-on-the_fig4_50399987
  21. https://www.youtube.com/watch?v=7pCXiRQMRKo&t=5s&ab_channel=UltrasoundPod
  22. https://litfl.com/terry-thomas-sign
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A Case of Posterior Vitreous Detachment

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A Case of Posterior Vitreous Detachment – Medical Student Clinical Pearl

Ben McMullin, Clinical Clerk III

Dalhousie Medicine New Brunswick, Saint John

Reviewed by Dr. David Lewis

Copyedited by Dr. Mandy Peach

Case Presentation

A 61 year old female presented to the emergency department complaining of a floater in her right eye, which appeared 3 days prior to presentation. The floater moved with her eye movements. The patient claimed that her vision in the right eye was slightly blurry over the past 3 days but denied any significant decline in visual acuity. She denied any trauma, eye pain, discharge, or redness, but was particularly concerned since she was blind in her left eye since childhood.

On examination, the patients right eye appeared normal, with no discharge or conjunctival injection. Her pupil was roughly 3 mm and reactive to light. Her visual acuity was 20/30 in the right eye, and extraocular eye movements as well as visual field testing were normal. The intraocular pressure in her right eye was 9 mmHg.

Anatomy of the Eye

Figure 1: Normal eye anatomy as seen with ultrasound imaging.1

 

The cornea is the most superficial convex membrane, and immediately posterior to this is the anterior chamber, which is seen as anechoic on sonography. Posterior to the anterior chamber is the iris. Immediately posterior to the lens is the posterior chamber, which is also anechoic on sonography. The outer membrane of the eye from the inner most layer to the outer consists of the retina, choroid, and sclera.2

 

Differential Diagnosis for Non-Traumatic Visual Disturbance
• Posterior vitreous detachment
• Retinal tear
• Vitreous hemorrhage
• Vitreous inflammation
• Ocular lymphoma
• Intraocular foreign body
• Uveitis3

POCUS Ocular Exam

Advantages of POCUS

Ultrasound is a useful tool in the evaluation of some ocular complaints in the ED. Dilated fundoscopic examination is not always easily performed in the ED, but bedside ultrasound is becoming more readily available to physicians.4,5 Ultrasound can be useful in diagnosis of a wide range of ocular complaints, such as retinal detachment, posterior vitreous detachment (PVD), vitreous hemorrhage, and intraocular foreign body.4

Technique

Depending on the clinical history, a bedside ultrasound examination of the eye may be performed with the patient either supine or sitting in a chair.4 A high frequency probe should be used for this exam.1

Liberal amounts of gel should be used when performing a POCUS ocular exam, so as to minimize the amount of pressure placed on the eye.4 The gel does not need to be sterile, however for patient comfort, some physicians place tegaderm over the eye being examined. In order to orient the probe properly, ensure that the indicator on the probe is pointing towards the patients head when performing a longitudinal scan, and to the patients right when performing a transverse scan.1

To ensure that the entire eye is assessed, the eye should be examined in both the longitudinal and transverse planes, and it is important to sweep through in both directions. If the patient is able, it is also helpful to ask them to look to the right and left, as well as up and down with the probe on the eye.1 It is imperative to maximize brightness – if the field is too dark pathology like vitreous detachment can be easily missed.

PVD vs Retinal Detachment on POCUS

Complete retinal detachment will often appear as a V shape on ultrasound, with the apex seen at the optic nerve.5 Partial detachments can be more subtle and can appear differently from case to case.6

PVD is less echogenic than retinal detachment. PVD can often be seen moving with eye movements, more so than with retinal detachment.5 There is often a lag seen between movement of the globe, and movement of the vitreous appendage. In PVD, the detached vitreous is not connected to the optic disc, which contrasts with retinal detatchment.6 PVD can vary widely in size and can be seen with or without vitreous hemorrhage.2

Figure 2: Retinal detachment visualized on point of care ultrasound.6

Figure 3: Retinal detachment on ultrasound. (PoCUS Atlas)

 

Figure 4: Posterior vitreous detachment visualized on point of care ultrasound.2

Figure 5: Vitreous detachment on ultrasound (PoCUS Atlas).

 

Management

In the ED, retinal detachment requires urgent referral to ophthalmology. Retinal detachment can progress to total vision loss and should be seen and treated within 24 hours.3 In contrast, isolated PVD has a much better prognosis. Typically, floaters resolve within 3 to 12 months, but patients should still be referred for follow-up within 3 months to ensure no retinal tear is detected.3

Case Conclusion

Bedside ocular ultrasound showed PVD in the patient’s right eye, with no evidence of vitreous hemorrhage or retinal detachment. The patient was reassured of the prognosis but given that she was completely dependent on her right eye for vision, ophthalmology agreed to assess her the following week.

References

  1. Roque PJ, Hatch N, Barr L, Wu TS. Bedside Ocular Ultrasound. Crit Care Clin 2014; 30(2): 227-241.
  2. Southern, Simon. Ultrasound of the Eye. Australas J Ultrasound Med 2009; 12(1): 32-37.
  3. Arroyo, Jorge G. “Retinal detachment” last modified March 19, 2020, https://www.uptodate.com/contents/retinal-detachment?search=vitreous%20detachment&sectionRank=1&usage_type=default&anchor=H3491968696&source=machineLearning&selectedTitle=1~11&display_rank=1#H1505785278.
  4. Lahham S, Qumber A, Bea MP, Lee C, Fox JC. Role of point of care ultrasound in the diagnosis of retinal detachment in the emergency department. Open Access Emergency Medicine 2019; 11: 265-270. Retrieved from https://search-proquest-com.ezproxy.library.dal.ca/docview/2314891088?accountid=%24%24CLIENTID&pq-origsite=primo.
  5. Botwin A, Engel A, Wasyliw C. The use of ocular ultrasound to diagnose retinal detachment: a case demonstrating sonographic findings. Emerg Radiol 2018; 25: 445-447.
  6. Gandhi K, Shyy W, Knight S, Teismann N. Point of care ultrasound for the evaluation of non traumatic visual disturbances in the emergency department: the VIGMO protocol. Am J Emerg Med 2019; 37 (8): 1547-1553.
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PoCUS for Diverticulitis

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Dal PoCUS Fellowship – Journal Club – Feb 2021

Dr. Mandy Peach  CCFP-EM

PoCUS Fellow

Dalhousie University Department of Emergency Medicine

 

A Prospective Evaluation of Point-of-Care Ultrasonographic Diagnosis of Diverticulitis in the Emergency Department Allison Cohen, MD*; Timmy Li, PhD; Brendon Stankard, RPA-C; Mathew Nelson

 

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Lisfranc Injury – We have PoCUS but do we still need the cavalry?

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PoCUS Fellow Pearl

Dr. Melanie Leclerc, CCFP-EM

MSK PoCUS Fellow

Dalhousie University Department of Emergency Medicine

 

Reviewed & Edited by Dr David Lewis (@e_med_doc)

All case histories are illustrative and not based on any individual

 

Case Report

A 32 year old male presents to a rural Emergency Department with a complaint of traumatic left foot pain. He was playing recreational football this evening. While crouching, the patient was tackled by another player who landed on his hyper-plantar flexed left foot from behind. The patient had immediate onset of pain in the middle of his foot and was unable to weight-bear. 

On physical examination, you notice significant bruising and swelling of the mid-foot. There is tenderness to the medial mid-foot specifically at the 1st-2nd tarsal-metatarsal articulations. X-rays of the foot appear normal. You are concerned about the possibility of a ligamentous Lisfranc injury.

https://www.footandanklesurgery.com.au/lisfranc-injuries

 

 

Lisfranc injuries

Lisfranc injuries are those that involve the tarsal-metatarsal joints. A spectrum of injury exists from ligamentous to fracture-dislocation. Up to 20% – 40% of injuries to the Lisfranc complex are missed in the Emergency Department. Unrecognized and untreated injuries can lead to long-term instability through the midfoot. As this region of the foot is responsible for a significant load during weight bearing, instability can accelerate degenerative changes in the foot resulting in chronic pain and disability

The injury is named after Jacques Lisfranc de St. Martin, a French surgeon and gynecologist performed forefoot amputations at the tarsometatarsal joint on cavalrymen, during the 1815 Napoleonic wars. Although he didn’t specifically describe the injury, it has since been recognised in equestrians and occurring as a result of a trapped plantar flexed foot in the stirrup during a fall.

 

Other mechanisms have been described including high velocity injuries (sports injuries, foot on brake pedal MVA) and low velocity injuries (Stepping off a curb awkwardly). Low velocity injuries are more likely to be missed than high velocity injuries.

Further Reading – OrthoBullets

 

Anatomy

The Lisfranc ligament complex is comprised of 3 ligaments. The dorsal (red), interosseous (blue) and the plantar (green) Lisfranc ligaments. The  Interosseous ligament is the largest and the dorsal ligament is the smallest.

The first and second rays have unique ligamentous anatomy wherein no intermetatarsal ligaments exist, but extreme strength is imparted by dorsal, interosseous, and plantar bundles of ligament binding the lateral aspect of the medial cuneiform bone with the medial head of the second metatarsal bone—the Lisfranc ligamentous complex. Only the dorsal and plantar Lisfranc ligaments are accessible to ultrasound.

 

 

 

PoCUS of the Lisfranc joint and dorsal lisfranc ligament (DLL)

Lisfranc injuries are one of the most commonly missed orthopaedic injuries in the Emergency Department. Normal X-rays are often falsely reassuring to providers and patients are discharged with a diagnosis of “soft-tissue injury”. These injuries result in midfoot instability and often require definitive surgical management.

PoCUS has been studied as a method of early detection of these injuries. Specifically, assessment of the dorsal lisfranc ligament (DLL) between the second metatarsal (M2) and the medial cuneiform(C1). PoCUS also has the advantages of being significantly cheaper and more accessible than CT and MRI. Further investigation is needed to validate this method of diagnosis, however ultrasound findings of a disrupted DLL and a widened C1-M2 interval compared to the contralateral side may increase your suspicion when pre-test probability is high.

 

Technique

  1. Linear probe-MSK setting starting at a depth of 2cm
  2. Place probe in transverse orientation over the proximal aspect of the 1st-2nd metatarsals with the probe indicator to the patient’s right
  3. Slide the transducer proximally until you locate the medial cuneiform and identify the junction between the medial cuneiform (C1) and the 2nd metatarsal (M2)
  4. The medial cuneiform will have an angulated contour appearance in contrast to the round appearance of the metatarsals
  5. Sweep to identify the dorsal lisfranc ligament (DLL)
  6. Assess the DLL for a fibrillar pattern, normal echogenicity and contour
  7. Measure the DLL width and the C1-M2 distance compare to the contralateral side
  8. Measure the C1-M2 distance with weightbearing (if patient tolerates) to compare
  9. Apply colour doppler to assess for hyperemia

 

PoCUS Findings

Medial Cuneiform (C1), 2nd Metatarsal (M2)

Note the angulated contour of C1 and the smooth contour of M2 – this sectional plane is important when locating the dorsal Lisfranc ligament. The ligament appears hypoechoic with a fibrillar pattern, typical for other ligaments more commonly visualized with PoCUS e.g MCL, ATFL.

1. Normal image – Arrows = dorsal Lisfranc ligament

2. Normal Clip and annotated image. Note how the dorsalis pedis a. frequently overlies the dorsal Lisfranc ligament (yellow lines)

3. Normal clip. Note how there is no separation of C1/M2 while counterstressing the 1st and 2nd rays

 

4. Thickened, convex contour

5. DLL disrupted, wide joint space

6. Widening C1-M2 with weightbearing

Video Case

 

Limitations

  1. Anisotropy – Irregular dorsal contour of foot can result in difficult perpendicular imaging of doral Lisfranc ligament. Stand-off gel pad may help.
  2. History of prior trauma – chronic Lisfranc injury may result in joint widening
  3. Bilateral injuries – inability to compare sides to judge joint space widening

Application

Standard foot radiographs should be performed in all cases of suspicion for Lisfranc Injury. Weight bearing radiographs should also be performed if tolerated (the ability to fully weight bear is often limited in the acute setting)

HIgh velocity injuries result in significant soft tissue swelling, and although non-weight bearing radiographs may not be diagnostic, the index of suspicion for Lisfranc injury will be high. Immobilization +/- early CT and follow up with foot and ankle specialist is recommended. For these, high pretest probability injuries, PoCUS findings are unlikely to change management significantly. A clear Lisfranc ligament rupture on PoCUS may trigger a request for CT/MRI earlier than otherwise considered. In most cases advanced imaging and a clear diagnosis is not usually possible until the swelling has subsided.

In low velocity injuries, soft tissue swelling is less pronounced. in the acute presentation the ability to perform weight bearing radiographs is limited by pain. Index of suspicion for Lisfranc injury may be low-moderate and the decision to immobilize and refer for specialist follow up can be difficult. While there is limited published evidence for PoCUS test characteristics in Lisfranc injury, a positive scan (injury + disrupted ligament / widening of C1/M2) is likely to be highly specific. Patients with positive PoCUS findings should therefore be immobilized and referred for specialist follow up. In those with negative or inconclusive findings, management and disposition will depend on degree of clinical suspicion and correlated with radiographic findings.

In summary, PoCUS provides a useful additional piece of information that can be plugged into a bayesian diagnostic pathway. What is the pretest probability of a particular diagnosis? After reviewing radiographs and performing PoCUS is the diagnosis more or less likely?

More evidence is required to fully understand the test characteristics of PoCUS for Lisfranc injury. Would the addition of plantar views improve sensitivity?

Although the performing the scan takes only a few minutes, it is quite technically challenging for the novice. As with all MSK PoCUS, repeated practice in numerous patient presentations will increase operator speed and accuracy.

 

Finally, although we still need the cavalry, PoCUS can help us decide which regiment and how quickly we need them!

 

References

  1. Mayich DJ, Mayich MS, Daniels TR. Effective detection and management of low-velocity Lisfranc injuries in the emergency setting: principles for a subtle and commonly missed entity. Can Fam Physician. 2012;58(11):1199-e625. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3498011
  2. Woodward, S., Jacobson, J.A., Femino, J.E., Morag, Y., Fessell, D.P. and Dong, Q. (2009), Sonographic Evaluation of Lisfranc Ligament Injuries. Journal of Ultrasound in Medicine, 28: 351-357.
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