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Hand and Wrist: Normal and Pathology

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Authors

Sergio Alvarez, MD, CAQ-SM
Assistant Professor
Department of Emergency Medicine
New York Presbyterian Queens
Weill Cornell Medical College

Yana Klein, DO
Loyola University Medical Center
Emergency Medicine Department
Sports Medicine Track
Class of 2023

Editors

William Denq, MD, CAQ-SM
Assistant Professor
Department of Emergency Medicine
University of Arizona

Summary

  • A high-frequency linear transducer, 10 MHz or greater, is the optimal probe to use as is provides increased resolution for the superficial structures of the hand and wrist
  • The hand and wrist can be evaluated in two compartments: flexor (volar) and extensor (dorsal)
  • There are 6 extensor compartments. Lister’s tubercle separates #2 and #3.
  • The flexor compartment contains Guyon’s canal, flexor compartment, and the carpal tunnel.
  • Pathologies such as De Quervain’s, carpal tunnel syndrome, Guyon’s canal syndrome, ganglion cyst, hamate fracture, and intersection syndrome can be evaluated with ultrasound.

Introduction

  • The wrist and proximal hand are critical to everyday functioning and are susceptible to a variety of pathologies.
  • Understanding the anatomy of the hand is necessary for the clinician to appropriately evaluate and identify the source of hand pain given the vast spectrum of pathology.
  • This chapter will review MSK US of the hand including the relevant anatomy and pathology that can be found in each view.

Ultrasound Probes and Settings

  • A high-frequency linear transducer, 10 MHz or greater, is the optimal probe to use as is provides increased resolution for the superficial structures of the hand and wrist
  • Images for the dorsal wrist can be optimized by placing the wrist in slight flexion and similarly for the volar side, in slight extension [1]. [1]Martinoli C. Musculoskeletal ultrasound;technical guidelines. Insights Imaging. 2010;1 (3):99-141
  • Optimize the image by placing the structure of interest in the center of the screen and adjusting the gain.

Anatomy

  • The hand and wrist can evaluated in two compartments: 
    • Flexor (volar) compartment 
    • Extensor (dorsal) compartments
  • Volar wrist
    • Flexor compartment contains the flexor tendons, carpal tunnel, and Guyon’s canal 
  • Dorsal wrist
    • 6 extensor compartments
    • Lister’s tubercle separates extensor compartment 2 and 3. 
  • Nerves: The wrist is innervated by the branches of the median, ulnar, and radial nerve.
Anatomy of the wrist extensor compartments. [2]Image provided courtesy of TeachMeAnatomy.com
anatomy of the flexor wrist
Anatomy of the flexor compartment. [3]Image provided courtesy of TeachMeAnatomy.com

Normal Ultrasound Anatomy​

  • There are multiple approaches to imaging a wrist with ultrasound.
  • This section will focus on the views and anatomical structures that are of particular interest for Emergency Physicians.

Dorsal Wrist

  • General
    • Position: Hand in pronation and slight flexion
    • Additional consideration: Water bath, utilize adequate gel to maintain contact
    • Probe: Linear probe
    • View: Short axis on dorsal wrist in slight flexion. Scan proximal to distal.
  • Structures to identify:
    • Extensor compartments 1-6. 
    • Lister’s Tubercle
  • Instructions: The order of compartment identification is performed from radial to ulnar side starting with the first compartment
Probe over dorsal wrist
Transverse plane image of the 1st extensor compartment containing the EPB and APL.

First Dorsal Wrist Compartment:

  • Place the patient’s wrist halfway between pronation and supination with the hypothenar eminence down towards the table. The probe should be over the lateral aspect of the radial styloid.
  • Using Lister’s tubercle identify the 2nd compartment, continue to move the probe to the radial side of the wrist until you are far lateral and superficial to the radial styloid 
  • This view contains the abductor pollicis longus (APL) and the extensor pollicis brevis (EPB). See Image 2 for more.
  • Follow the APL distally over the scaphoid
  • The radial artery can sometimes be visualized deep to the sensory branch of the superficial radial nerve.
Dorsal Wrist
Dorsal Wrist

Second Dorsal Wrist Compartment

  • Identify this compartment by moving the ultrasound to the radial side of Lister’s Tubercle
  • This view contains the extensor carpi radialis brevis (ECRB) and extensor carpi radialis longus tendons (ECRL) directly adjacent to the Lister’s Tubercle.

Third Dorsal Wrist Compartment

  • Identify Lister’s Tubercle and slide the probe directly adjacent to the ulnar side of the tubercle.
  • This view contains the extensor pollicis longus tendon (EPL), which crosses over in an oblique path towards the thumb as it courses distally from Lister’s tubercle.
  • See: Intersection Syndrome
Dorsal Wrist
Dorsal Wrist

Fourth Dorsal Wrist Compartment

  • To the ulnar side of the 3rd dorsal compartment you will find the 4th compartment
  • This compartment contains the extensor digitorum (ED) and extensor indicis (EI) tendons

Fifth Dorsal Wrist Compartment

  1. The extensor digiti minimi tendon (EDM) travels through this compartment, near distal radioulnar joint
Dorsal Wrist
Dorsal Wrist

Sixth Dorsal Wrist Compartment

  • This compartment contains the extensor carpi ulnaris tendon (ECU) which runs through a groove between the ulnar head and styloid process.
  • Obtaining this image may require a gel step-off depending on patient anatomy.
Dorsal Wrist

Volar Wrist​

  • General
    • Position: Hand in supination, slight extension
    • Additional consideration: Water bath, utilize adequate gel to maintain contact
    • Probe: Linear probe
    • View: Short axis on volar wrist in slight flexion.
    • Scan proximal to distal.
  • Structures to identify: 
    • Radial and ulnar artery
    • Flexor carpi radialis
    • Flexor digitorum superficialis
    • Flexor digitorum profundus
    • Carpal ligament
    • Median nerve
    • Palmaris longus 
      • Note: Anatomical variant, may be absent. Found ulnar to flexor carpi radialis and superficial (volar) to carpal tunnel.
  • Instructions: Start from the center and move proximal to distal.
    • See below for more information regarding the Carpal Tunnel and Guyon’s Canal.

Carpal Tunnel

  • In short-axis view, evaluate the proximal carpal tunnel by placing the probe in the center of the wrist at the level of the volar wrist crease 
  • The median nerve will be hypoechoic compared to the flexor tendons and hyperechoic compared to the forearm muscles. If experiencing difficulty in identifying the nerve you can scan in the transverse plane from wrist crease to palm and the median nerve will travel from radial to flexors to ulnar and deep in between the flexor digitorum tendons. Another method is to fan the ultrasound probe while in the transverse plane along the long axis of the nerve and tendon. The nerve will remain with relatively stable echogenicity and the tendons will darken due to anisotropy [4]Martinoli C. Musculoskeletal ultrasound;technical guidelines. Insights Imaging. 2010;1 (3):99-141
  • Center the median nerve and identify the radial artery, flexor carpi radialis (FCR), flexor digitorum tendons (superficialis and profundus). The median nerve can be examined in long axis as well.
Carpal Tunnel
Carpal Tunnel

Guyon's Canal

  • Start by identifying the ulnar nerve and artery in-short axis view at the level of the volar wrist crease 
  • Follow the artery and nerve distally as it approaches the pisiform [Figure 6]
  • The ulnar nerve will be located between the ulnar artery and pisiform 
  • The flexor carpi ulnaris (FCU) can be identified proximal and slightly ulnar to the pisiform 
  • Scanning distally will bring the hook of hamate into view deep to the ulnar nerve and artery [2] [5]Cartwright MS, Hobson-Webb LD, Boon AJ, et al. Evidence-based guideline: neuromuscular ultrasound for the diagnosis of carpal tunnel syndrome. Muscle Nerve 2012; 46:287.
Guyons Canal
Guyons Canal

Fingers

  • General
    • Position: Hand in supination or pronation depending on anatomic structure in question.
    • Additional consideration: Water bath, utilize adequate gel to maintain contact
    • Probe: Linear probe
    • View: Dependent on
  • Structures to identify:
    • Flexor digitorum profundus (FDP)
    • Flexor digitorum superficialis (FDS)
    • Terminal extensor digitorum tendon
  • Note: Finger anatomy is complex, this is not a comprehensive review.
  • Instructions: Individualized for each structure, see below.
Hand position
Hand position
  • Flexor digitorum profundus (FDP)
    • Can be identified by scanning the finger over volar surface along midline and in its long-axis
    • The FDP will attach at the proximal end of the distal phalanx [Figure 7]
    • A disruption here will limited flexion at the distal interphalangeal joint (DIP)
  • Flexor digitorum superficialis (FDS)
    • This tendon can be found by scanning over the volar surface of the finger in long-axis near the palmar digital crease
    • The FDS then splits [Figure 8] at the level of the proximal interphalangeal joint and runs side by side to the FDP and attaches to the proximal end of the middle phalanx
    • A disruption here will limit flexion at the proximal interphalangeal joint (PIP)
FDP
FDS
  • Terminal extensor digitorum tendon
    • This tendon attaches to the proximal end of the distal phalanx [Figure 9]
    • A disruption here will produce a “mallet finger” and limit extension at the DIP
Terminal Extensor Tendon

Pathology

Carpal Tunnel Syndrome​

  • Signs and symptoms: nocturnal paresthesia, intermittent pain or paresthesia of the 1st-3rd digits
  • Etiology: repetitive microtrauma or overuse injuries lead to thickening and fibrosis of the transverse ligament which in turn compresses the median nerve [6]Cartwright MS, Hobson-Webb LD, Boon AJ, et al. Evidence-based guideline: neuromuscular ultrasound for the diagnosis of carpal tunnel syndrome. Muscle Nerve 2012; 46:287[7]Firestein, Gary S., et al. Firestein & Kelley’s Textbook of Rheumatology . Eleventh edition., Elsevier, 2021[8]Dębek A, Czyrny Z, Nowicki P. Sonography of pathological changes in the hand. J Ultrason. 2014;14(56):74-88. doi:10.15557/JoU.2014.0007 (See Figure 5). 
  • Evaluation: no consensus on diagnostic standard yet
  • Various diagnostic criteria: 
    • Inlet to outlet median nerve area ratio (IOR)
    • Flattening ratio
    • Swelling ratio
    • Bowing of the flexor retinaculum
    • Median nerve wrist-to-forearm area ratio
  • Editor’s note: Refer back to Volar Wrist “Carpal Tunnel” for ways to identify the median nerve
Carpal Tunnel
Carpal Tunnel

Guyon’s (Pisohamate) Canal Syndrome

  • Also known as “cyclist’s palsy”
  • Signs and symptoms: paresthesias and occasional diminished motor function of the ulnar nerve distribution
  • Etiology: ulnar nerve entrapment as it passes through Guyon’s canal. Entrapment can be due to repetitive microtrauma to Guyon’s canal from cyclist handlebars or a mass obstruction such as ganglion cyst, lipoma, or ulnar artery thrombosis.
  • Diagnosis: evaluate Guyon’s canal for evidence of ulnar nerve entrapment from mass obstruction
  • Guyon’s canal syndrome commonly referred to as “cyclist’s palsy” is caused by ulnar nerve entrapment as it passes through Guyon’s canal. At this level, patients would present with altered sensation in their fingers in addition to diminished motor function in the muscles of the hypothenar eminence (flexor digiti minimi, abductor digiti minimi, and opponens digiti minimi), adductor pollicis, the interossei, medial two lumbricals, and palmaris brevis) [9]Magee, David J., PhD, BPT, CM; Manske, Robert C., PT, DPT, MEd, SCS, ATC, CSCS. Forearm, Wrist, and Hand. Orthopedic Physical Assessment. Published January 1, 2021. © 2021.
Guyons Canal
Guyons Canal

Hamate Fracture​

  • Signs and symptoms: Often missed, seen in young active patients who present with palmar pain
  • Etiology: Classic mechanism is a fall on extended wrist or repeated forceful striking of a ball with a bat or club.
  • Evaluation: Utilize a linear probe to scan the palmar hypothenar region. The hook of hamate is located superficially at the base of the 4th and 5th metacarpals. Compare the contralateral side under ultrasound to determine if any noted cortical irregularity is abnormal.
Hamate Fracture Xray
Hamate Fracture Ultrasound

Ganglion cyst​

  • Signs and symptoms: An often painless, palpable well-circumscribed mass, ganglion cysts are commonly found near joints and tendons. The majority of cysts are found on the dorsal wrist near the scapholunate articulation.
  • Etiology: Likely repetitive microtrauma to connective tissue.
  • Evaluation: Utilize a linear probe to scan the mass in question. A ganglion cyst will typically be hypoechoic or anechoic and have well-defined margins and thick walls. [10]Teefey SA, Dahiya N, Middleton WD, Gelberman RH, Boyer MI. Ganglia of the hand and wrist: a sonographic analysis. AJR Am J Roentgenol. 2008 Sep;191(3):716-20. doi: 10.2214/AJR.07.3438. PMID: 18716098
  • Dębek A, Czyrny Z, Nowicki P. Sonography of pathological changes in the hand. J Ultrason. 2014;14(56):74-88. doi:10.15557/JoU.2014.0007[/ref]
Ganglion cyst of the wrist
Ganglion Cyst of the Wrist
Ganglion Cyst of the Wrist

Extensor Tendinopathies​

  • Signs and symptoms: Pain, weakness, or stiffness at the dorsal wrist or forearm is often the complaint. It may be accompanied by morning wakeup pain and a history of overuse.
  • Etiology: Repetitive microtrauma. For example, ECU tendinopathy is commonly caused by repetitive ulnar deviation leading to tendonitis or tenosynovitis. 
  • Evaluation: Utilize a linear probe in transverse view over the extensor tendon in question. tenosynovitis appears as thickened echogenic areas that may or may not be surrounded by tenosynovial fluid [4]. [11]Firestein, Gary S., et al. Firestein & Kelley’s Textbook of Rheumatology . Eleventh edition., Elsevier, 2021.
  • Figure 6. Axial US image of the Extensor Carpal Ulnaris showing the thickened synovial sheath (arrows) with areas of echogenic synovitis within the fluid distending the tendon sheath [10] [12]Benjamin Plotkin, Srihari C. Sampath, Srinath C. Sampath, and Kambiz Motamedi. MR Imaging and US of the Wrist Tendons. RadioGraphics 2016 36:6, 1688-1700
wrist extensor tendinopathy
Axial US image of the Extensor Carpal Ulnaris showing the thickened synovial sheath (arrows) with areas of echogenic synovitis within the fluid distending the tendon sheath. [13]Benjamin Plotkin, Srihari C. Sampath, Srinath C. Sampath, and Kambiz Motamedi. MR Imaging and US of the Wrist Tendons. RadioGraphics 2016 36:6, 1688-1700
Video of the dorsal wrist of a patient with rheumatoid arthritis. Tenosynovitis with hypertrophy of the extensor tendons is demonstrated.

Intersection Syndrome​

  • Signs and symptoms: Pain and/or swelling over the dorsal wrist proximal to the radial styloid. Often seen in repetitive wrist extension or flexion activities such as rowing, weightlifting, horseback riding, skiing, or occupational injuries. 
  • Etiology: The first dorsal compartment extensors, abductor pollicis longus and extensor pollicis brevis, cross over the second dorsal compartment extensors, extensor carpi radialis brevis and extensor carpi radialis longus. The pathophysiology is debated, but likely includes a component of friction from apposition of the first extensor compartment on the second extensor compartment and stenotic changes of the second compartment tendon sheaths [12] [14]Costa CR, Morrison WB, Carrino JA. MRI features of intersection syndrome of the forearm. AJR Am J Roentgenol 2003;181(5):1245–1249. Impingement between the tendons can result in inflammation, pain, and swelling [14] [15]Dębek A, Czyrny Z, Nowicki P. Sonography of pathological changes in the hand. J Ultrason. 2014;14(56):74-88. doi:10.15557/JoU.2014.0007.
  • Evaluation: Utilize a linear probe in the transverse view to locate the 1st and 2nd extensor compartments radial to Lister’s tubercle. Following the 1st compartment proximally, examine the junction of the 1st and 2nd compartments. Evaluate for tendon sheath fluid and peritendinous edema [13][16]Montechiarello S, Miozzi F, D’Ambrosio I, Giovagnorio F. The intersection syndrome: ultrasound findings and their diagnostic value. J Ultrasound 2010;13(2):70–73. See Video 1 for an example of where the 1st and 2nd extensor compartments intersect.
Fluid in the tendon sheath and peritendinous edema. [17]Case courtesy of Dr Maulik S Patel, Radiopaedia.org, rID: 66323
Normal anatomy demonstration of where the 1st and 2nd extensor compartments intersect. Intersection syndrome can result in tendon sheath fluid and peritendinous edema.

De Quervain’s Tenosynovitis​

  • Signs and Symptoms: Radial sided wrist pain, weakness, or swelling that worsens with wrist or thumb activity. Tenderness over the 1st extensor compartment radial to Lister’s tubercle and a positive Finkelstein test aid in the clinical diagnosis of this pathology.
  • Etiology: The first extensor compartment runs through a fibrous tunnel over the radial styloid that can become entrapped, resulting in inflammation through repetitive motion. 
  • Evaluation: Utilize a linear probe in the transverse view to locate the 1st extensor compartment radial to Lister’s tubercle. Evaluate the two tendons, EPB and APL, in transverse and longitudinal view for tendon thickening, hypoechoic changes, and surrounding hypoechoic or anechoic fluid [1,9,10] [18]Bogges, BR. Musculoskeletal ultrasound of the wrist: UpToDate, Fields, KB et al. (Ed), UpToDate, Waltham, MA 2020[19]Benjamin Plotkin, Srihari C. Sampath, Srinath C. Sampath, and Kambiz Motamedi. MR Imaging and US of the Wrist Tendons. RadioGraphics 2016 36:6, 1688-1700
De Quervain’s Tenosynovitis​ ultrasound
Hypoechoic soft tissue thickening around EPB (extensor pollicis brevis) tendon at distal end of radius. This thickening shows hypervascularity. Tendon is round in shape due to constriction from all around. Tendon is intact with normal echopattern.[20]Case courtesy of Dr Maulik S Patel, Radiopaedia.org, rID: 51160
First dorsal compartment corticosteroid injection in short axis.

Ultrasound Guidance Procedures

Pearls & Pitfalls

Anistropy
Dynamic Imaging
  • Anisotropy
    • Anisotropy is an artifact in MSK US that occurs when the ultrasound beam is at an oblique insonating angle to an anatomical structure. This artifact is most prominent in tendons and muscles, but it can also be seen with ligaments and nerves. This can result in a loss of echogenicity, which can misdiagnose soft tissue injuries (false-positive finding). To avoid anisotropy, the transducer must be held strictly perpendicular to these anatomical structures, because even a few degrees of rotation off of this plane can result in abnormal-appearing hypoechoic foci that mimics soft-tissue pathology like tendinosis [20]. 
  • Dynamic Imaging
    • Dynamic imaging is an important advantage of MSK US because it can provide real-time imaging of MSK disorders. Examples include visualization of muscles and tendons during motion and muscle contraction, impingement syndromes, subluxation, and ligament pathology. Specifically for the knee, this can diagnose causes of snapping knee syndrome and visualize snapping IT band [21]. Stress testing of the knee under ultrasound can be used to visualize collateral ligament tears, which appear as increased joint space widening and discontinuity in the normal fibrillar ligament structure that worsens with valgus/varus stress testing [5]. 
  • Patient Positioning
    • Positioning of the patient, provider and ultrasound machine should be optimized for image quality and the comfort of the patient and provider. Generally, the knee should be positioned in between the provider and the ultrasound machine so that the provider can visualize both physical anatomy and ultrasound anatomy in their line of sight. The probe marker should be positioned so that movement of the transducer relative to the structure of interest correlates with the same direction of movement on the screen. When you encounter difficulty with diagnostic or therapeutic ultrasound, take advantage of the ability to compare the symptomatic side to the asymptomatic side and scan in different positions of the knee.

References

References[+]