Fig. 1

The length of the skin defect and that of advance distance of the V–Y flap should be L'-L. The distance from the midpoint of the middle phalanx to its base on the contralateral hand is labelled as L'. The same interval on the affected finger is named L (\(\overline{AD }\); orange line). Line P (\(\overline{BC }\); red line) is the length of the proximal phalanx; line M (\(\overline{AB }\); blue line), half the length of the middle phalanx; and line H (\(\overline{CD }\); green line), the height of the flap, which also represents the distance of the advancement of the V–Y flap. The angle θ (∠ABC) indicates the angle of limitation of extension in the PIP joint with flexion contracture