The Journal of Bone and Joint Surgery, Vol 63, Issue 9 1371-1381, Copyright © 1981 by Journal of Bone and Joint Surgery, Inc
The kinesiology of the thumb trapeziometacarpal joint
WP Cooney, MJ Lucca, EY Chao and RL Linscheid
To measure the motions of the trapeziometacarpal joint of the thumb
quantitatively, a roentgenographic method was developed and tested using
T-shaped metal markers, a special cassette-holder, and biplane
roentgenograms. Two experiments were performed. In the first one, the metal
markers were fixed to the trapezium and third metacarpal in ten cadaver
specimens, and a fixed spatial relationship between the trapezium and the
third metacarpal was identified roentgenographically. This relationship was
that the reference axes of the trapezium were aligned at median angles of
48 degrees of flexion, 38 degrees of abduction, and 80 degrees of pronation
with reference to the reference axes of the third metacarpal. In the second
experiment, in the dominant hand of nine male and ten female subjects
(average age, twenty-six years) T-shaped markers were fixed to the skin
overlying the third metacarpal and the metacarpal and phalanges of the
thumb. Using the same roentgenographic technique and coordinate systems
employed in the first study, the average total motions of the
trapeziometacarpal joint (determined as motions of the first metacarpal
with reference to the third metacarpal) were 53 degrees of
flexion-extension, 42 degrees of abduction-adduction, and 17 degrees of
axial rotation (pronation-supination). In addition, six functional
positions of the thumb were studied: rest, flexion, extension, abduction,
tip pinch, and grasp. A position of adduction and flexion of the
trapeziometacarpal joint was most common during thumb function, and both
the trapeziometacarpal and metacarpophalangeal joints contributed to
rotation of the thumb.
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