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Sonographic Appearance of the Extensor Carpi Radialis Intermedius Tendon
PM R 7 (2015) 789-791
www.pmrjournal.org
Images
Sonographic Appearance of the Extensor Carpi Radialis Intermedius Tendon Jay Smith, MD, Adam M. Pourcho, DO, Sanjeev Kakar, MD, MBA A 47-year-old, right-hand dominant woman was referred for sonographic examination of her right dorsal wrist for clinically suspected second dorsal compartment tenosynovitis. Ultrasound revealed tenosynovitis, extensor carpi radialis longus (ECRL) tendinosis, a normal extensor carpi radialis brevis (ECRB) tendon, and a third, oval, tendinous structure lying between the ECRL and ECRB tendons. This third tendon attached distally to the third metacarpal base directly adjacent to the ECRB and proximally transitioned to a muscle belly positioned between the ECRL and ERCB muscles
(Figure 1A-C). The sonographic appearance was consistent with an extensor carpi radialis intermedius (ECRI) tendon [1-4]. The ECRI is present in 10%-24% of individuals and usually represents an asymptomatic anatomic variant [1-4]. It is considered to be a developmental variant occurring during the formation of the ECRL and ECRB, which have a common embryologic origin [2]. The ECRI typically lies between and is partially fused to the ERCL and ECRB muscle bellies proximally, transitions to a tendon at the intersection between the first and second
Figure 1. Transducer positioning for sonographic short-axis (SAX) view of the second dorsal compartment (CPT) with correlative sonographic and magnetic resonance imaging (MRI) images. (A) Transducer (black rectangle) and patient positioning for the sonographic SAX view of the second dorsal CPT. (B) Sonographic correlative image of the second dorsal CPT at the level of the proximal intersection of the first dorsal CPT over the second dorsal CPT. The extensor carpi radialis intermedius tendon (white arrow) is shown in its typical location between and deep to the extensor carpi radialis longus (ECRL) (L) and extensor carpi radialis brevis (B) tendons. Note thickening and hypoechoic heterogeneity of the ECRL tendon consistent with tendinosis. (C) A correlative T2-weighted axial MRI scan of the same patient again shows the extensor carpi radialis intermedius tendon (white arrow) between and deep to the ECRL (L) and extensor carpi radialis brevis (B) tendons. The dotted rectangle represents the relative sonographic field of view represented in image B. LT ¼ Lister’’s tubercle; RAD ¼ radius; ULN ¼ ulnar. (Note: The MRI image was inverted for orientation purposes.)
1934-1482/$ - see front matter ª 2015 by the American Academy of Physical Medicine and Rehabilitation http://dx.doi.org/10.1016/j.pmrj.2015.04.005
790
Extensor Carpi Radialis Intermedius Tendon
Figure 2. Sonographic short-axis (SAX) view of an extensor carpi radialis intermedius (ECRI) tendon with differential anisotropy. (A) A sonographic SAX view of the second dorsal compartment (CPT) (with transducer orientation the same as in Figure 1A), demonstrating a subtly noticed ECRI tendon (white arrows) central and deep to the extensor carpi radialis longus (L) and extensor carpi radialis brevis (B) tendons at the level of the extensor retinaculum (ER). (B) By tilting the transducer to create differential anisotropy between the extensor carpi radialis longuseextensor carpi radialis brevis and the ECRI tendons, the ECRI tendon becomes more conspicuous (hypoechoic) relative to surrounding tissues. The maneuver can be useful to distinguish the ECRI tendon from the other wrist extensor tendons at the level of the ER. Care must be taken to not mistake this region of hypoechogenicity for synovial thickening, synovial cyst, or tenosynovitis. ULN ¼ ulnar.
compartment tendons, and attaches distally to the second or third metacarpal base [1-3]. In some cases it has been found to fuse with the ECRL or ECRB tendons, respectively, prior to insertion [1-3]. The ECRI tendon is variable in size and may be up to several millimeters in diameter [1,3]. Larger ECRI tendons have been used for tendon transfers [1]. Despite the prevalence of the ECRI tendon, only one prior case report addresses the sonographic appearance of this structure [5]. Vessal and Rai reported a unilateral, painless bulge in the radial forearm of a 39-year-old woman that was confirmed by magnetic resonance imaging to be an ECRI muscle belly [5]. Although the authors used ultrasound to identify the aberrant muscular portion of the ECRI, the appearance of the ECRI tendon in the second dorsal compartment was
neither discussed nor demonstrated [5]. Based on our experience, either magnetic resonance imaging or ultrasound can be used to easily identify the ECRI tendon, which lies between the ECRL and ECRB tendons at the wrist, and its sonographic conspicuity can be increased by tilting the transducer to take advantage of differential anisotropy (Figure 2A, B). The ECRI tendon is a common occurrence in the second dorsal extensor compartment. It may be misdiagnosed as a split tear of the ECRL or ECRB tendons, or if it appears anisotropic (ie, dark), it may be mistaken for a tendon sheath effusion, synovial cyst, or tenosynovial thickening (Figure 3A-C). Furthermore, the ECRI tendon represents a potential pitfall to diagnostic ultrasound of the second dorsal compartment. Correct identification of the ECRI tendon can be confirmed by
Figure 3. A companion case of a 45-year-old patient with de Quervain tenosynovitis (not shown) and an extensor carpi radialis intermedius (ECRI) tendon. (A) Transducer positioning for sonographic short-axis (SAX) view of the second dorsal compartment (CPT) at the proximal intersection (solid rectangle) and at Lister’s tubercle (LT; dotted rectangle). (B) A correlative sonographic SAX image of the second dorsal CPT demonstrates an ECRI tendon (I) lying deep to the extensor carpi radialis longus tendon (L) at the level of the proximal intersection of the first dorsal CPT over the second dorsal CPT. The use of differential anisotropy with tilting of the transducer allows the ECRI tendon to appear anisotropic (ie, hypoechoic) relative to the surrounding tendons. (C) Correlative sonographic SAX view of the ECRI tendon in the same patient at LT lying central and deep to the extensor carpi radialis longus and extensor carpi radialis brevis (B) tendons. Notice the crowding of the tendons under the extensor retinaculum (ER). ULN ¼ ulnar.
J. Smith et al. / PM R 7 (2015) 789-791
meticulous scanning, including controlling for anisotropy and identifying the tendon’s proximal and distal attachments. References 1. Wood V. The extensor carpi radialis intermedius tendon. J Hand Surg Am 1988;13A:242-245.
791
2. Claasen H, Wree A. Multiple variations in the region of Mm. extensores carpi radialis longus and brevis. Ann Anat 2002;184:489-491. 3. Nayak S, Krishnamurthy A, Prabhu L, Rai R, Ranade A, Madhyastha S. Anatomical variation of radial wrist extensor muscles: A study in cadavers. Clinics 2008;63:85-90. 4. Hong M, Hong M. An uncommon form of the rare extensor carpi radialis accessorius. Ann Anat 2005;187:89-92. 5. Vessal S, Rai S. Accessory extensor carpi radialis brevis muscle, a pseudomass of the distal forearm: Ultrasound and MR appearancesdcase report and literature review. Clin Radiol 2006;61:442-445.
Disclosure J.S. Department of Physical Medicine & Rehabilitation, Mayo Clinic Sports Medicine Center, Mayo Clinic, W14, Mayo Building, 200 1st St SW, Rochester, MN 55905; Departments of Radiology and Anatomy, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN. Address correspondence to: J.S.; e-mail: Smith. [email protected] Disclosures outside this publication: consultancy, Tenex Health (money to author and institution); employment, Tenex Health; payment for lectures, including service on speakers bureaus, Gulf Coast Ultrasound Institute; patents, royalties, stock/stock options, Tenex Health (money to author and institution)
A.M.P. Department of Physical Medicine and Rehabilitation, Department of Sports Medicine, Swedish Spine, Sports, and Musculoskeletal Medicine, Swedish Medical Group, Seattle, WA Disclosure: nothing to disclose S.K. Department of Orthopaedic Surgery, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN Disclosures outside this publication: consulting fee or honorarium, Arthrex & Skeletal Dynamics
Submitted for publication January 4, 2015; accepted April 3, 2015.
www.pmrjournal.org
Images
Sonographic Appearance of the Extensor Carpi Radialis Intermedius Tendon Jay Smith, MD, Adam M. Pourcho, DO, Sanjeev Kakar, MD, MBA A 47-year-old, right-hand dominant woman was referred for sonographic examination of her right dorsal wrist for clinically suspected second dorsal compartment tenosynovitis. Ultrasound revealed tenosynovitis, extensor carpi radialis longus (ECRL) tendinosis, a normal extensor carpi radialis brevis (ECRB) tendon, and a third, oval, tendinous structure lying between the ECRL and ECRB tendons. This third tendon attached distally to the third metacarpal base directly adjacent to the ECRB and proximally transitioned to a muscle belly positioned between the ECRL and ERCB muscles
(Figure 1A-C). The sonographic appearance was consistent with an extensor carpi radialis intermedius (ECRI) tendon [1-4]. The ECRI is present in 10%-24% of individuals and usually represents an asymptomatic anatomic variant [1-4]. It is considered to be a developmental variant occurring during the formation of the ECRL and ECRB, which have a common embryologic origin [2]. The ECRI typically lies between and is partially fused to the ERCL and ECRB muscle bellies proximally, transitions to a tendon at the intersection between the first and second
Figure 1. Transducer positioning for sonographic short-axis (SAX) view of the second dorsal compartment (CPT) with correlative sonographic and magnetic resonance imaging (MRI) images. (A) Transducer (black rectangle) and patient positioning for the sonographic SAX view of the second dorsal CPT. (B) Sonographic correlative image of the second dorsal CPT at the level of the proximal intersection of the first dorsal CPT over the second dorsal CPT. The extensor carpi radialis intermedius tendon (white arrow) is shown in its typical location between and deep to the extensor carpi radialis longus (ECRL) (L) and extensor carpi radialis brevis (B) tendons. Note thickening and hypoechoic heterogeneity of the ECRL tendon consistent with tendinosis. (C) A correlative T2-weighted axial MRI scan of the same patient again shows the extensor carpi radialis intermedius tendon (white arrow) between and deep to the ECRL (L) and extensor carpi radialis brevis (B) tendons. The dotted rectangle represents the relative sonographic field of view represented in image B. LT ¼ Lister’’s tubercle; RAD ¼ radius; ULN ¼ ulnar. (Note: The MRI image was inverted for orientation purposes.)
1934-1482/$ - see front matter ª 2015 by the American Academy of Physical Medicine and Rehabilitation http://dx.doi.org/10.1016/j.pmrj.2015.04.005
790
Extensor Carpi Radialis Intermedius Tendon
Figure 2. Sonographic short-axis (SAX) view of an extensor carpi radialis intermedius (ECRI) tendon with differential anisotropy. (A) A sonographic SAX view of the second dorsal compartment (CPT) (with transducer orientation the same as in Figure 1A), demonstrating a subtly noticed ECRI tendon (white arrows) central and deep to the extensor carpi radialis longus (L) and extensor carpi radialis brevis (B) tendons at the level of the extensor retinaculum (ER). (B) By tilting the transducer to create differential anisotropy between the extensor carpi radialis longuseextensor carpi radialis brevis and the ECRI tendons, the ECRI tendon becomes more conspicuous (hypoechoic) relative to surrounding tissues. The maneuver can be useful to distinguish the ECRI tendon from the other wrist extensor tendons at the level of the ER. Care must be taken to not mistake this region of hypoechogenicity for synovial thickening, synovial cyst, or tenosynovitis. ULN ¼ ulnar.
compartment tendons, and attaches distally to the second or third metacarpal base [1-3]. In some cases it has been found to fuse with the ECRL or ECRB tendons, respectively, prior to insertion [1-3]. The ECRI tendon is variable in size and may be up to several millimeters in diameter [1,3]. Larger ECRI tendons have been used for tendon transfers [1]. Despite the prevalence of the ECRI tendon, only one prior case report addresses the sonographic appearance of this structure [5]. Vessal and Rai reported a unilateral, painless bulge in the radial forearm of a 39-year-old woman that was confirmed by magnetic resonance imaging to be an ECRI muscle belly [5]. Although the authors used ultrasound to identify the aberrant muscular portion of the ECRI, the appearance of the ECRI tendon in the second dorsal compartment was
neither discussed nor demonstrated [5]. Based on our experience, either magnetic resonance imaging or ultrasound can be used to easily identify the ECRI tendon, which lies between the ECRL and ECRB tendons at the wrist, and its sonographic conspicuity can be increased by tilting the transducer to take advantage of differential anisotropy (Figure 2A, B). The ECRI tendon is a common occurrence in the second dorsal extensor compartment. It may be misdiagnosed as a split tear of the ECRL or ECRB tendons, or if it appears anisotropic (ie, dark), it may be mistaken for a tendon sheath effusion, synovial cyst, or tenosynovial thickening (Figure 3A-C). Furthermore, the ECRI tendon represents a potential pitfall to diagnostic ultrasound of the second dorsal compartment. Correct identification of the ECRI tendon can be confirmed by
Figure 3. A companion case of a 45-year-old patient with de Quervain tenosynovitis (not shown) and an extensor carpi radialis intermedius (ECRI) tendon. (A) Transducer positioning for sonographic short-axis (SAX) view of the second dorsal compartment (CPT) at the proximal intersection (solid rectangle) and at Lister’s tubercle (LT; dotted rectangle). (B) A correlative sonographic SAX image of the second dorsal CPT demonstrates an ECRI tendon (I) lying deep to the extensor carpi radialis longus tendon (L) at the level of the proximal intersection of the first dorsal CPT over the second dorsal CPT. The use of differential anisotropy with tilting of the transducer allows the ECRI tendon to appear anisotropic (ie, hypoechoic) relative to the surrounding tendons. (C) Correlative sonographic SAX view of the ECRI tendon in the same patient at LT lying central and deep to the extensor carpi radialis longus and extensor carpi radialis brevis (B) tendons. Notice the crowding of the tendons under the extensor retinaculum (ER). ULN ¼ ulnar.
J. Smith et al. / PM R 7 (2015) 789-791
meticulous scanning, including controlling for anisotropy and identifying the tendon’s proximal and distal attachments. References 1. Wood V. The extensor carpi radialis intermedius tendon. J Hand Surg Am 1988;13A:242-245.
791
2. Claasen H, Wree A. Multiple variations in the region of Mm. extensores carpi radialis longus and brevis. Ann Anat 2002;184:489-491. 3. Nayak S, Krishnamurthy A, Prabhu L, Rai R, Ranade A, Madhyastha S. Anatomical variation of radial wrist extensor muscles: A study in cadavers. Clinics 2008;63:85-90. 4. Hong M, Hong M. An uncommon form of the rare extensor carpi radialis accessorius. Ann Anat 2005;187:89-92. 5. Vessal S, Rai S. Accessory extensor carpi radialis brevis muscle, a pseudomass of the distal forearm: Ultrasound and MR appearancesdcase report and literature review. Clin Radiol 2006;61:442-445.
Disclosure J.S. Department of Physical Medicine & Rehabilitation, Mayo Clinic Sports Medicine Center, Mayo Clinic, W14, Mayo Building, 200 1st St SW, Rochester, MN 55905; Departments of Radiology and Anatomy, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN. Address correspondence to: J.S.; e-mail: Smith. [email protected] Disclosures outside this publication: consultancy, Tenex Health (money to author and institution); employment, Tenex Health; payment for lectures, including service on speakers bureaus, Gulf Coast Ultrasound Institute; patents, royalties, stock/stock options, Tenex Health (money to author and institution)
A.M.P. Department of Physical Medicine and Rehabilitation, Department of Sports Medicine, Swedish Spine, Sports, and Musculoskeletal Medicine, Swedish Medical Group, Seattle, WA Disclosure: nothing to disclose S.K. Department of Orthopaedic Surgery, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN Disclosures outside this publication: consulting fee or honorarium, Arthrex & Skeletal Dynamics
Submitted for publication January 4, 2015; accepted April 3, 2015.