What is Trigger
Finger?
Trigger finger is a common
disorder of the hand which causes a painful snapping or locking of
the fingers or thumb. The medical name for this condition is
stenosing tenosynovitis. Stenosing refers to the narrowing of an
opening or passageway in the body. Tenosynovitis refers to
inflammation of the outer covering of the tendons that bend and
extend the fingers and thumb. The tendons are tough, fibrous cords
that connect the muscles of the forearm to the bones of the fingers
and thumb. This muscle and tendon system enables one to bend the
fingers inward when making a fist, and extend them out
straight.
The tendons glide through a protective covering called the tendon
sheath. The sheath is like a tunnel, and is lined with a thin
membrane called synovium. The synovial lining helps reduce friction
as the tendons glide through the tendon sheath. Areas of dense
fibrous tissue called annular bands or pulleys are also part of the
tendon sheath. These structures are attached to the bones of the
fingers and thumb, and hold the tendons close to the bones over
which they pass. Your Indiana Hand Center physician will review
this anatomy with you during your office visit.
Trigger finger is often caused by inflammation of the
synovial sheath surrounding the tendons. It may also result from
enlargement of the tendon itself, or narrowing of the first annular
band (A1 pulley).
When inflamed, the normally thin covering of the sheath may be
thickened to several times its normal size. This reduces the amount
of space through which the tendons are able to pass. The tendon is
no longer able to glide freely through the sheath, and the tendon
itself may swell up in a balloon-like mass at the point where it
tries to pass through the tunnel.
Upon forceful bending of the finger or thumb, the enlarged portion
of the tendon is dragged through the constricted opening. This
motion is often accompanied by a painful snap, and the finger or
thumb may be locked in a bent position. Straightening the finger or
thumb may require using the non-affected hand to actually pull the
finger back into an extended position, causing another painful snap
as the swollen portion of the tendon passes back through the
sheath.