Definition
The snap finger, also known as stenosing tenosynovitis, is a disorder in which one of the fingers of the hands remains in a bent position, only to straighten up with a sharp jerk (as if a trigger was triggered and released, " trigger finger ").
The snap finger appears most commonly in the dominant hand and in most cases affects the thumb, middle or ring finger. The pathology can affect several fingers simultaneously and involve both hands.
People forced to perform repetitive gripping actions, for occupational or hobby reasons, are more susceptible to the onset of the snap finger.
Therapeutic treatment varies depending on the severity and duration of the disorder.
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The signs and symptoms of the snap finger can be mild or severe and include:
- swelling or stiffness of the finger (especially in the morning);
- feeling of snap or snap at the completion of the flexion-extension movement or while firmly grasping an object;
- presence of a nodule at the base of the affected finger;
- localized pain in the palm of the hand;
- finger stuck in a bent position, straightening suddenly or, in more serious cases, unable to complete the extension movement.
In the event of stiffness or jerking at the articulation of a finger it would be advisable to warn the doctor, especially if the affected area is hot and inflamed, as the symptoms indicate the onset of a possible infection.
Snap finger and Dupuytren's syndrome
The snap finger should not be confused with Dupuytren's contracture, a pathological condition affecting the connective tissue of the palm of the hand. The snap finger, however, can occur in conjunction with this disorder. Dupuytren's disease is characterized by the progressive and permanent flexion of one or more fingers, caused by the chronic and progressive fibroproliferative lesion of the aponeurosis of the palm of the hand (fibrous band surrounding the muscle to secure it to bone insertion).
Causes
The main cause that causes the onset of the finger to snap is a narrowing of the sheath that surrounds the tendon of the affected finger. The flexors (superficial and deep) are long fibers that depart from the muscles of the forearm, pass into the wrist and are inserted on the phalanges of the fingers, connecting the muscle to the bone. The tendons are covered by a protective membrane, in turn surrounded by the tenosynovia, which releases a lubricating liquid, which allows the tendon to slide without friction in its membrane, while the finger makes extension and flexion movements.
If the tenosynovial sheath becomes inflamed frequently or for prolonged periods of time, the space within the tendon lining may become narrow and constrictive.
The flexor tendons of the fingers do not easily slip through the sheath and force the finger to remain locked in the folded position, before extending with a click. This condition causes irritation and, progressively, an inflammatory process affecting the tendons involved. If the inflammation is prolonged it is possible that scarring, thickening (fibrosis) or nodules may occur.
The presence of synovial swelling increases the tendon difficulty in overcoming the entry of the digital channel. To be able to extend the finger, the patient must make a forced traction, causing the click, associated with a violent pain. The disorder is very annoying, as it greatly limits the function of the hand.
Risk factors
The risk factors that make it susceptible to the onset of the snap finger are:
- Microtraumas in the hand .
- Repeated gripping movements : a subject is more inclined to develop a snap finger if forced to grasp an object, such as a tool or a work tool (scissors, shears ...), for long periods of time.
- Concomitant diseases : patients suffering from some pathologies (rheumatoid arthritis, diabetes, hypothyroidism and some infections) turn out to be more at risk of suffering from finger snap.
- Sex : the disorder is more common in women. The incidence is lower in males.
Diagnosis
The diagnosis of the snap finger is essentially clinical: the doctor can diagnose the disorder based on the anamnesis (patient's medical history) and on the physical examination. The physical examination allows the doctor to identify the painful areas, check the fluidity of the movements by asking the patient to close and open the hand (transition from flexion to extension position). With palpation of the palm of the hand, at the metacarpophalangeal joint, the doctor can detect the presence of any subcutaneous nodules, often painful.
