Treatment of MCP Joints in the Rheumatoid Hand

Abstract

The fi nger extensor tendons do not insert at the base of the proximal phalanx , as they need to glide proximally and distally to provide extension of the interphalangeal joints (IPJ). The extensor tendons are stabilized at the dorsum of the metacarpal heads by two aponeurotic expansions, the sagittal bands (SB), which insert at both sides of the volar plate of the metacarpophalangeal joints (MPJ). The SB are responsible for maintaining the extensor tendon at the dorsum of the joint during radial and ulnar inclination of the fi ngers, as well as allowing the tendon to glide proximally and distally during extension and fl exion of the fi nger joints. If the intrinsic muscles are paralyzed, as seen after median and ulnar nerve lesions, the extensor tendon will only extend the MPJ, causing a claw deformity of the fi ngers. In these circumstances, if the MPJ are passively held in fl exion, because the extensor tendon does not insert into the proximal phalanx (PP), it will be capable of extending the IP joints.The fl exion forces at the MPJ, provided by the extrinsic fl exors and the intrinsic musculature, are far greater than the extension force provided by the extensor tendon. The collateral ligaments (CL) originate on the dorsum of the metacarpals and insert at the most anterior part of the base of the proximal phalanx, for the purpose of preventing the PP from displacing anteriorly. Anterior displacement of the PP is also prevented by the ball and socket joint morphology, as well as the constraint of the SB, which insert at both sides of the volar plate and should be considered as a proximal extension of the PP.Synovitis of the MPJ will attenuate the collateral ligaments (CL) and the SB, allowing the PP to displace volarly from the pull of the extrinsic and intrinsic fl exor muscles. The intensity and characteristics of the joint synovitis, as seen in cases of lupus, may rapidly destroy the CL and both SB, causing a complete anterior dislocation of the PP. When the dorsal stabilizers are not completely disrupted, the PP will partially sublux causing a scalloping deformity from wear of the dorsal part at its base.Another common deformity is an ulnar inclination of the fi ngers, known as ulnar drift. There is no single cause for the ulnar drift deformity, but rather a combination of several factors and the relative importance of each of them are diffi cult to determine. The following causes have been described as contributing to ulnar drift of the fi ngers in the rheumatoid hand: gravity, thumb

Valoración de la mano en la enfermedad reumatoide

“…ISBN 978-84-7993-361-6. Enlace: http://hdl.handle.net/10334/5442 ge proximal, la desviación hacia cubital de los dedos y la pérdida de extensión (1).…”