"I-P flexor lag" after thumb flexor reconstruction---causes and solution

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 caused include shortening of the muscletendon unit, loss of pulleys with bowstringing, adhesions and hypermobile joints.