SCIENTIFIC ARTICLE
Symptomatic Flexor Carpi Radialis Brevis: Case Report Arkaphat Kosiyatrakul, MD, Suriya Luenam, MD, Sunya Prachaporn, MD A patient with a flexor carpi radialis brevis (FCRB) is reported. In contrast to all but one previous case, the anomalous FCRB was painful. The FCRB tendon was located in a separate compartment; the tenosynovitis in that compartment was the likely cause of pain. Release of the compartment relieved the symptoms. (J Hand Surg 2010;35A:633–635. © 2010 Published by Elsevier Inc. on behalf of the American Society for Surgery of the Hand.) Key words Flexor carpi radialis brevis, separated compartment, wrist pain, symptomatic.
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NOMALOUS MUSCLES OF the forearm and wrist are
occasionally found incidentally during imaging studies, cadaveric dissections, or surgical procedures. They can also present with symptoms of pain or nerve compression. Flexor carpi radialis brevis (FCRB) is an uncommon anomalous muscle,1–5 the incidence of which is 3.9% to 8.6%.1–2 An FCRB that is associated with pain is extremely rare; we found only one report in the literature.5 We report another case with the same clinical presentation. The etiology of the pain appeared to be due to the separate compartment for the FCRB and accompanying tenosynovitis. CASE REPORT A 57-year-old, right hand– dominant woman presented with a 6-month history of intermittent painful swelling on the volar radial aspect of the wrist, just proximal to the wrist flexion crease. The pain was aggravated by activities such as wringing or ironing clothes. The pain was greatest when she pushed her right hand against the chair or the floor to get up, or when she leaned weight on the wrist in full extension. On physical examination we found a 1-cm area of ill-defined tenderness and swelling on the volar radial aspect of the right wrist. This area of swelling was firm FromtheDepartmentofOrthopaedics,PhramongkutklaoHospitalandCollegeofMedicine,Bangkok, Thailand. Received for publication June 24, 2009; accepted in revised form December 18, 2009. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Arkaphat Kosiyatrakul, MD, Department of Orthopaedics, Phramongkutklao Hospital and College of Medicine, 315 Ratchawithi Road, Bangkok 10400 Thailand; email:
[email protected]. 0363-5023/10/35A04-0017$36.00/0 doi:10.1016/j.jhsa.2009.12.028
and nonmobile. Localized tenderness was found along the flexor carpi radialis (FCR) tendon at the wrist level. Pain could be elicited with resisted palmar flexion as well as passive hyperextension of the wrist. Radiographs of the wrist showed no abnormal findings. Our provisional diagnosis was a volar ganglion cyst or FCR tendinitis. The patient requested surgical treatment. She was advised that the planned procedure would consist of excision of the volar ganglion cyst and decompression of the FCR tunnel. The surgery was performed under brachial block. We made a volar zigzag incision, beginning from the distal forearm to the distal wrist crease, in the line of the FCR tendon and over the area of the swelling. The FCR tendon sheath was identified but no mass or ganglion was found. The sheath of FCR tendon was opened. The synovitis of the FCR was minimal and the tendon was intact. After we mobilized the FCR tendon ulnarly, we encountered an anomalous tendon. The proximal part of the anomalous tendon was separated from the FCR tendon by a 1-cm-long septum (Fig. 1). This finding resembled the separate first dorsal compartment, found in de Quervain’s disorder. A moderate amount of synovial tissue was found around the anomalous tendon. The anomalous tendon was connected to its muscle, which is found outside the FCR tendon sheath. When the tendon was pulled proximally, flexion of the wrist was demonstrable. When the anomalous tendon was pulled distally, its muscle belly was pulled into its compartment (Fig. 1). A similar finding was also demonstrated when the wrist was placed in full extension. We believed this finding explained the cause of the pain. The compartment of the anomalous tendon was then released and the synovial tissue was excised (Fig. 2). The FCR tunnel at the
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SYMPTOMATIC FCRB
FIGURE 1: The FCR tendon sheath is open. The FCR tendon and the FCRB tendon (open and white arrows, respectively) are in the same compartment but the FCRB tendon is separated from the FCR tendon by a septum (open arrowhead). The FCRB muscle (white arrowhead) is found outside the sheath of the FCR.
trapezial crest, the narrowest part, was left undisturbed. We did not perform further dissection to identify the origin and the insertion point of the muscle because it was not part of the patient’s informed consent. The skin was closed and a bulky dressing was applied. The dressing was removed on the fifth postoperative day and wrist motion exercises were allowed as tolerated. Two months after surgery, the pain was completely gone and a full range of motion of the wrist (75o extension and 75o flexion) was obtained. DISCUSSION Flexor carpi radialis brevis is a rare anatomical variant. It is occasionally encountered inadvertently during cadaveric dissections or surgical procedures.1–5 FCRB originates from the volar aspect of the distal radius. In some cases, the muscle occupies the radial insertion of pronator quadratus and causes hypoplasia of the pronator muscle.3,4 The FCRB tendon usually passes beneath the FCR tendon and has various sites of insertion, such as the second, third or forth metacarpal, trapezium, and capitate.1–5 The FCR and FCRB tendons were found in the same compartment in all studies.1–5 To our knowl-
FIGURE 2: The septum was released. The FCRB tendon (white arrow) runs underneath the FCR tendon (open arrow).
edge, the separate compartment in our case has not been reported previously. Symptomatic FCRB is extremely rare. To our knowledge, there has been only one previously reported case.5 Pain and swelling localized in the volar radial aspect of the wrist were the patient’s chief complaint. Magnetic resonance imaging and surgical findings were different from those in the previously reported literature. The FCRB tendon originated dorsal to the FCR tendon in the forearm, then crossed superficially to the FCR tendon from ulnar to radial within the FCR tunnel. The authors concluded that the patient’s symptoms appeared to be caused by the intersection between the FCRB and FCR tendons. In our case, beside the volar ganglion cyst, we suspected FCR tendinitis because the patient had a pathognomonic sign of pain on resisted wrist flexion as well as local tenderness directly over the tendon.6,7 However, this condition cannot explain why the patient had pain on passive extension of the wrist. Surgical exploration demonstrated the separate compartment of the FCRB tendon. When the FCRB tendon was pulled distally or the wrist was placed in full extension, the FCRB muscle was trapped in the separate compartment. The FCR tendon sheath and the compartment of the FCRB tendon were released and the tenosynovitic tissue was removed. However, the FCR tunnel at the trapezial crest, the most common site
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of compression in a typical case of FCR tendinitis,7,8 was left undisturbed. After the surgery, our patient had complete resolution of her symptoms. This result, combined with findings observed during surgery, leads us to attribute the source of pain in this patient to the separate compartment of the FCRB and accompanying tenosynovitis, not the FCR tendinitis. Anomalous muscle such as the FCRB should be included in the differential diagnosis of radial side wrist pain, especially when it is accompanied by a painful volar radial swelling. REFERENCES 1. Wood J. On human muscular variations and their relation to comparative anatomy. J Anat Physiol 1867;1:44 –59.
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2. Carleton A. Flexor carpi radialis brevis vel profundus. J Anat 1935; 69:292–293. 3. Dodds SD. A flexor carpi radialis brevis muscle with an anomalous origin on the distal radius. J Hand Surg 2006;31A:1507–1510. 4. Kang L, Carter T, Wolfe SW. The flexor carpi radialis brevis muscle: an anomalous flexor of the wrist and hand. A case report. J Hand Surg 2006;31A:1511–153. 5. Peers SC, Kaplan FT. Flexor carpi radialis brevis muscle presenting as a painful forearm mass: case report. J Hand Surg 2008;33A:1878 – 1881. 6. Fitton J, Shea FW, Goldie W. Lesions of the flexor carpi radialis tendon and sheath causing pain at the wrist. J Bone Joint Surg 1968;50B:359 –363. 7. Gabel G, Bishop AT, Wood MB. Flexor carpi radialis tendinitis. Part II: results of operative treatment. J Bone Joint Surg 1994;76A:1015– 1018. 8. Bishop AT, Gabel G, Carmichael SW. Flexor carpi radialis tendinitis. Part I: operative anatomy. J Bone Joint Surg 1994;76A: 1009 –1014.
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