Article

Dexterity after finger pollicization (reconstruction to thumb) is critical to
functional outcomes. While most tests of hand function evaluate
a combination of
strength, coordination, and motor control, the Strength-Dexterity (S-D) paradigm
focuses on the dynamic control of fingertip forces. We evaluated 10 pollicized
and 5 non-pollicized hands from 8 participants ages 4-17 years (2 female, 6 male;
10.6 +/- 4.5 years). Participants partially compressed and held an instrumented
spring prone to buckling between the thumb and first finger to quantify dynamic
control over the direction and magnitude of fingertip forces. They also completed
traditional functional tests including grip, lateral pinch, and tripod pinch
strength, Box and Blocks, and 9-hole peg test. Six of 10 pollicized hands and all
non-pollicized hands had S-D scores comparable to typically developing children.
However, dynamical analysis showed that pollicized hands exhibit greater
variability in compression force, indicating poorer corrective action. Almost all
pollicized hands scored below the normal range for the traditional functional
tests. The S-D test Z-scores correlated moderately with Z-scores from the other
functional tests (r = 0.54-0.61;
p = 0.02-0.04) but more weakly than amongst the
other functional measures (r = 0.58-0.83; p = 0.0002-0.02), suggesting that the
S-D test captures a different domain of function. A higher incidence of radial
absence in the hands with poor S-D scores (3/4 vs. 0/6 in hands with normal S-D
scores, p = 0.03) was the only clinical characteristic associated with S-D
outcome. Overall, these results suggest that while most pollicized hands can
control fingertip forces, the nature of that control is altered.
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