guidebook. - Fanconi Anemia Research Fund

102
Fanconi Anemia: Guidelines for Diagnosis and Management
child often helps discriminate between these types by
pattern of usage. An unstable thumb (Type III-B) is not
incorporated into pinch and grasp. Prehension or pinch
develops between the index and long digits, and the
index finger tends to rotate out of the palm to resemble
a thumb position. In equivocal cases, the decision is
further complicated by the delayed ossification of the
bones at the base of the thumb (trapezium and trapezoid),
which do not ossify until four to six years of
age. The decision to ablate a hypoplastic thumb without
a base is often a difficult process for parents and caregivers.
Discussions with the surgeon and conversations
with families who have made similar decisions are
often helpful.
A thumb that is slightly smaller than the normal thumb
(Types I, II, and III-A) can be reconstructed, or augmented,
by tendon transfers to improve its motion
and use. Thumb reconstruction in Types II and III-A
requires addressing all deficient elements. The tight
web space is corrected by opening the space between
the thumb and index finger. The metacarpophalangeal
joint instability is corrected by ulnar collateral ligament
reconstruction. The deficient thenar muscles are
supplanted by a tendon and/or muscle transfer from the
ring or small finger to the thumb (Figure 4). This tendon
transfer improves active motion and enhances function.
There is negligible effect on the donor digit.
A thumb without a stable base (Types III-B, IV, and V)
is removed, and the index finger moved to the thumb
position. The index is moved with its nerves, arteries,
tendons, and muscles. This procedure is known
as a pollicization. The time to perform pollicization
remains controversial, with a trend toward early surgery
(6 months to 1 year of age), prior to the normal