Purpose
To assess the influence of lunate type on scaphoid kinematics.
Methods
One hundred normal wrists had fluoroscopic assessment of the wrist in maximal radial,
neutral, and ulnar deviation. The shortest distance in a neutral position between
the capitate and triquetrum, C-T distance, determined lunate type. A type I lunate
had a C-T distance of ≤2 mm, a type II lunate ≥4 mm, and an intermediate group lay
between these values. Scaphoid flexion and translation in radial and ulna deviation
was measured.
Results
There were 18 subjects with a type I lunate, 19 with an intermediate lunate, and 63
with a type II lunate. There was no statistically significant difference between lunate
type, subject age, or hand dominance. There was a statistically significant higher
proportion of women with a type I lunate. Subjects with a type II lunate had a statistically
greater amount of flexion during radioulnar deviation as determined by CR index (0.79
vs 0.91) and scaphoid flexion index (0.21 vs 0.09). Subjects with a type II lunate
had statistically less translation during radioulnar deviation as determined by translation
ratio (0.22 vs 0.31) and scaphoid inclination index (0.18 vs 0.23). The average scaphoid
kinematic index in subjects with a type II lunate was 1.24, intermediate 0.86, and
type I 0.42. A scaphoid kinematic index of greater than 1 indicates the scaphoid has
more flexion during radioulnar deviation than translation.
Conclusions
Wrists with a type I lunate show statistically greater scaphoid translation with radial
deviation. Wrists with a type II lunate show statistically greater scaphoid flexion
with radial deviation. Intermediate lunates have intermediate scaphoid mechanics.
This allows the surgeon to determine the likely wrist scaphoid mechanics based on
the lunate type determined from a single posterior-anterior x-ray.
Key words
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Article info
Publication history
Accepted:
March 19,
2007
Received:
December 21,
2006
Footnotes
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
Identification
Copyright
© 2007 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.
