boutonniere deformity


What is a boutonniere deformity?

Boutonnière deformityA boutonniere deformity characterizes an injury of one of the eight fingers, excluding the thumbs, when the middle joint of the finger will remain bent when you try to straighten your finger.  Quick medical attention can reverse the damage, but a boutonniere deformity that goes untreated in a timely manner will remain deformed despite intervention.  A boutonniere deformity manifests when a portion of tendon that attaches to the middle bone of the finger tears away from the bone or from a traumatic event cutting it.

Relevant anatomy to a boutonniere deformity

Control of the hand relies on muscles on site and further up into the wrist.  On the palm side of the hand flexor tendons attach these controlling muscles to the fingers and allow you to bend your fingers.  On the top of the hand extensor tendons allow you to straighten out your fingers from a bend position.  Two bones compose the thumbs, and three bones compose the fingers.  On the center bone of each finger the flexor tendons attach with the central slip of tendon.  When the central slip of tendon sustains damage to no longer allow the flexor tendon to straighten out the center bon of the finger the boutonniere deformity manifests with a straightened joint between the center bone and the finger tip while the joint between the center bone and the bone closest to the palm remains bent.

What causes a boutonniere deformity?

Usually a boutonniere deformity results from blunt force impact to the top of the finger causing pressure on the tendon of the nature it cannot bear.  When the tendon tears an internal dimple forms that appears like a dimple from a button, after all boutonniere means button in French.  Other causes of a boutonniere deformity besides blunt trauma include degenerative conditions such as arthritis.

Symptoms of a boutonniere deformity

When the central slip of tendon tears away the finger no longer can straighten.  Since a bit of extensor tendon attaches at each bone in the finger the patient exhibits a bend between the first two bones of the finger with a straightened joint between the middle bone and the fingertip.  A boutonniere deformity can form on any of the eight fingers containing three bones.  The thumbs can not form a boutonniere deformity.  However, the thumbs can also have flexor and extensor tendons torn; these types of injuries are not boutonniere deformities, but also require attention.  Swan neck deformities of fingers are similar, but they present opposite with the first joint bending the wrong way, up, and the fingertip pointing down.

Treatment of a boutonniere deformity

RA_hand_deformityLuckily, surgeons prefer non-surgical treatment for a boutonniere deformity.  They apply a specialized splint that immobilizes the first joint of the finger while allowing the fingertip to still bend.  Patients are required to wear this splint at all times for up to 6 weeks, and then possibly at night for an extended period.  Specialized exercises to strengthen and stretch the fingers can accompany recover after the splinting period, and patients with high risk of reinjury from lifestyle, such as contact athletes, your physician will recommend a protective splint.  Splinting the torn tendon in the case of a boutonniere deformity allows the tendon to reattach over time without allowing the ends of the tendon to further separate as it heals.  Some patients however will not respond to splinting and will require surgery.  Other situations that indicate surgical intervention include cases where the injury stems from a laceration that severed the tendon entirely, cases involving rheumatoid arthritis as the cause, or when a the tearing of the tendon from the bone brought a large chuck of bone off with it.


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