Variation in insertion of the abductor digiti minimi: an anatomic study

We dissected 70 cadaver hands to examine the anatomy of the insertion of the abductor digiti minimi (ADM). The insertion had 2 forms. In 58 hands the insertion of the ADM was divided into 2 tendinous portions: one attached the base of the proximal phalanx (bone insertion) and the other attached the extensor aponeurosis (extensor insertion). In 12 hands the bone insertion existed solely. The mean length and width of the bone insertion were 10.6 +/- 3.1 and 4.0 +/- 0.9 mm and those of the extensor insertion were 18.5 +/- 4.0 and 2.1 +/- 1.1 mm, respectively. The mean proportion of the width of the extensor insertion to that of whole tendon was 31% (range, 0% to 50%). These observations show greater variation in the insertional anatomy of the ADM than reported previously.