“I-P Flexor Lag” after Thumb Flexor Reconstruction — Causes and Solution

Abstract

A small but significant percentage of thumbs fail to regain complete range of motion after reconstructive procedures designed to replace lost function of the flexor pollicis longus tendon. A characteristic but little noted posture and attitude of metacarpophalangeal flexion with loss of interphalangeal motion and metacarpophalangeal stabilisation with restoration of interphalangeal motion is described. (“I-P flexion lag”—I.P.F.L.) Clinical causes include shortening of the muscle-tendon unit, loss of pulleys with bowstringing, adhesions and hypermobile joints.