Distally extended muscle belly of the flexor digitorum within the carpal tunnel: is it a risk factor for carpal tunnel syndrome?
Background The distally extended muscle belly of the flexor digitorum (MB-FD) within the carpal tunnel has been suggested as a plausible cause for carpal tunnel syndrome (CTS) based on cadaveric studies. Purpose To evaluate whether MB-FD within the carpal tunnel is a risk factor for CTS by comparing asymptomatic volunteers and patients with CTS. Material and Methods Presence, length, and cross-sectional area of MB-FD within the carpal tunnel were evaluated in 63 wrists of 32 asymptomatic volunteers and 52 wrists of 33 patients with CTS using ultrasonography. Length of MB-FD within the carpal tunnel was measured as the distance between the distal end of MB-FD and the palmar margin of the distal radius longitudinally. On a transverse scan, the cross-sectional area of MB-FD at the proximal limit of the carpal tunnel was measured. Results MB-FD in the carpal tunnel was found in 39 (62%) asymptomatic volunteers and 35 (67%) patients with CTS ( P = 0.549). There was a female preponderancy of MB-FD within the carpal tunnel in asymptomatic volunteers ( P = 0.044), but not in patients. Length and cross-sectional area of MB-FD within the carpal tunnel were significantly greater in male-CTS patients than in male volunteers ( P = 0.022 and 0.012, respectively). These qualities were risk factors for CTS in men, though not in women. Conclusion The presence of distally extended MB-FD within the carpal tunnel was not a risk factor for CTS. In men, a longer and thicker MB-FD within the carpal tunnel increased the risk for CTS.
Department of Radiology, College of Medicine, Inje University Busan Paik Hospital, Busan, Republic of Korea.
Hye Jung
HJ
Choo
Department of Radiology, College of Medicine, Inje University Busan Paik Hospital, Busan, Republic of Korea.
Sun Joo
SJ
Lee
Department of Radiology, College of Medicine, Inje University Busan Paik Hospital, Busan, Republic of Korea.
Young-Mi
YM
Park
Department of Radiology, College of Medicine, Inje University Busan Paik Hospital, Busan, Republic of Korea.
Dong Wook
DW
Kim
D000328:Adult; D002349:Carpal Tunnel Syndrome / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D011446:Prospective Studies; D012307:Risk Factors; D014463:Ultrasonography
Carpal tunnel syndrome; anatomic variation; flexor digitorum superficialis; ultrasonography