Tendon and nerve displacement at the wrist during finger movements.
BACKGROUND
Repetitive motion of the hand has been suggested as a major factor of pathogenesis of cumulative trauma disorders (e.g., carpal tunnel syndrome). The purpose of this study was to investigate the 3D displacement of the median nerve and extrinsic finger flexor tendons (flexor digitorum superficialis; flexor digitorum profundus) as a function of flexion/extension of metacarpophalangeal joints of the index and middle fingers.


METHODS
Shim markers were placed on the median nerve, flexor digitorum superficialis, and flexor digitorum profundus tendons at the wrist region of seven cadaveric specimens for the purpose of digitization of tendon and nerve locations. The metacarpophalangeal joint of the index or middle finger was moved from 15 degrees extension to 75 degrees of flexion while the markers were digitized at increments of 15 degrees. Marker displacements were determined in the longitudinal, radial-ulnar, and dorsal-palmar directions.


RESULTS
Movement of metacarpophalangeal joint of the index or middle finger caused tendon and nerve displacements in the longitudinal, radial-ulnar, and dorsal-palmar directions. The longitudinal displacements of the median nerve and the flexor tendons were linearly correlated with angular movement of the metacarpophalangeal joint. The maximum longitudinal displacements of the flexor digitorum superficialis tendon, flexor digitorum profundus tendon, and median nerve were, on average, 14.7 mm, 11.9 mm, and 3.0 mm, respectively, for the index finger; and 18.4 mm, 14.5 mm, and 4.0 mm, respectively, for the middle finger. The radial-ulnar and dorsal-palmar displacements were irregular and relatively small. The maximum displacements in these transverse directions fell in the range of 1.4-5.1 mm for the median nerve and 1.9-7.3 mm for the flexor tendons.


CONCLUSIONS
Finger flexor tendons and median nerve move not only concurrently, but also differentially, in all anatomical directions. Tendon and nerve movement during prolonged repetitive hand movement may cause hand disorders such as carpal tunnel syndrome.
Ugbolue
U Chris
UC
Hand Research Laboratory, Department of Orthopaedic Surgery, University of Pittsburgh, 210 Lothrop Street, P.O. Box 71199, Pittsburgh, PA 15213, USA.
Hsu
Wei-Hsiu
WH
Goitz
Robert J
RJ
Li
Zong-Ming
ZM
D000368:Aged; D002102:Cadaver; D005385:Fingers / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D008475:Median Nerve / Q000502:physiology*; D008662:Metacarpophalangeal Joint / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D013223:Statistics as Topic; D013710:Tendons / Q000502:physiology*; D014953:Wrist / Q000502:physiology*