Hand Movement Imbalance

Posted Fri, 09/04/2009 - 8:51pm by dnennig

Hand Movement Imbalance

What happens when one movement of your hand is injured? Do you recognize the imbalance in these photos?

                a.  b.  c.   d.       

Look at picture (a) above. This is a boutonniere/pseudoboutonniere deformity. In this scenario, the central slip can rupture, volar plate can have a contracture, PIP flexion contracture can occur, reduced central slip excursion, triangular ligament laxity can occur and ORL tightness happens which can hyperextend the DIP jt.

The next picture (b) is a swan neck deformity. This can occur from any primary pathology that causes excessive tension on the extensor apparatus leading to PIP joint hyperextension. Some of these can be a mallet finger deformity, flexor tendon graft, superficialis transfer, reduced EDC excursion, extensor contracture, intrinsic contracture and saggital band rupture.

The next picture (c) is of a claw deformity from intrinsic wasting due to a low level ulnar nerve injury. This occurs when the ulnar nerve is injured, inhibiting function of the intrinsics, but still allowing function of the long flexors and extensors. The extrinsic extensors hyperextend the MP joints, and the extrinsic flexors flex the PIP and DIP joints. The flexion vector, induced by the intrinsics, across the MP joint is lost. Over time, the volar capsular-ligamentous structures will stretch and the claw deformity will become more severe.

The next picture (d) is the effects of Extensor Quadrigia. This can occur due to tendon adhesions following repair of the EDC proximal to Zone V, metacarpal fractures causing adhesions, and saggital band ruptures. The mechanism of Extensor quadrigia is a deficient EDC excursion of one tendon slip affecting adjacent EDC tendon function. This effect can cause an increase in intrinsic force at the PIP, causing swan neck deformity, intrinsic contractures, volar subluxation of proximal phalanx base in RA, and an ulnar drift in RA.

Many imbalances of the kinematic function of the hand can be preventable with early management and correctable, and adjustable to keep independence and function, with good knowledge and understanding of the biomechanics.