TRIGGER FINGER

TRIGGER FINGER

Trigger finger results from thickening of the flexor tendon within the distal aspect of the palm.

This thickening causes abnormal gliding of the tendon within the tendon sheath. Specifically, the affected tendon is caught at the edge of the first annular (A1) pulley.

Patients can have difficulty flexing the affected digit if the tendon is caught distal to the A1 pulley, or extending the digit, if the tendon is caught proximal to the pulley.

The condition is very painful, especially when the locked digit snaps (releases) beyond the restriction by the use of increased force.

PATHOPHYSIOLOGY

Normally, the tendons of the finger flexors glide back and forth under a restraining pulley.

    Thickening of the flexor tendon sheath restricts the normal gliding mechanism.

A nodule may develop on the tendon, causing the tendon to get stuck at the proximal edge of the A1 pulley when the patient is attempting to extend the digit, thereby causing difficulty.

When more forceful attempts are made to extend the digit, by using increased force from the finger extensors or by applying an external force (for example, by exerting force on the finger with the other hand), the digit classically snaps open with significant pain at the distal palm and into the proximal aspect of the affected digit.

Less commonly, the nodule is restricted distal to the A1 pulley, resulting in difficulty flexing the digit.

MORTALITY/MORBIDITY

• Morbidity - Trigger digits can be a significant source of pain. In addition, the difficulty in achieving a normal range of motion at the digit can make functional tasks (eg, grasping objects, typing) problematic.

• Mortality - No mortality is known to be associated with this condition.

SEX

This condition has a higher incidence in women (75%) than in men.

AGE

Trigger digits are most commonly seen in adults, with the average age range for its occurrence being 52-62 years.

CLINICAL

HISTORY

• A classic complaint is difficulty in achieving full extension of a single digit, which eventually releases or snaps open with pain at the distal palm and into the digit.

• In individuals with diabetes or rheumatoid arthritis, multiple digits may be involved in trigger finger.

• Some patients have difficulty with finger flexion rather than extension, although the former is less common.

• Other patients may have a painful nodule in the distal palm without any catching or triggering.

• Some patients report stiffness in the fingers, especially after they have been asleep or following other periods of inactivity.

• Some patients may have a history of repetitive trauma to the affected area.

• Patients may have a history of diabetes or rheumatoid arthritis.

• Some patients report swelling of the affected digit, particularly at the digit's base or proximal aspect.

PHYSICAL

• At the level of the distal palmar crease, a tender nodule can be palpated, usually overlying the metacarpophalangeal (MCP) joint.

• The affected digit may lock in a flexed or (less commonly) extended position. When the patient attempts to move the digit more forcefully beyond the restriction, the digit may snap or trigger beyond the restriction. The triggering movement is very painful for the patient.

• In severe cases, the patient is unable to move the digit beyond the restriction, so no triggering occurs.

• With a trigger thumb, the tenderness to palpation is found at the palmar aspect of the first MCP joints rather than over the distal palmar crease.

CAUSES

• Congenital cases of trigger thumb are generally caused by a nodule of the flexor pollicis longus tendon.

• In adults, some cases may be associated with repetitive trauma.

DIAGNOSIS

LABORATORY STUDIES

• As a rule, no lab tests are needed in the diagnosis of trigger finger. If there is a concern regarding an associated, undiagnosed condition, such as diabetes, rheumatoid arthritis, or another connective tissue disease, an assessment of, respectively, glycosylated hemoglobin (HgbA1c), fasting blood sugar, or rheumatoid factor should be ordered.

PROCEDURES

• Injection of the trigger digit is generally considered to be therapeutic rather than diagnostic.

TREATMENT

PHYSICAL THERAPY

Physical therapy is generally not required for patients with trigger finger.

For chronic cases, however, treatment may include a trial of heating modalities followed by sustained nonballistic stretching of the flexor tendon, as well as soft-tissue mobilization of the A1 pulley.

Following injection or surgery, a home exercise (stretching) program may be one component of treatment for patients.

OCCUPATIONAL THERAPY

If a trial of therapy is recommended for patients with chronic trigger finger or for individuals who require postsurgical hand therapy, the physician may refer them to a physical or occupational therapist, depending on his/her preference and the therapists' availability.

The treatment provided by an occupational therapist is very similar to the above-discussed physical therapy treatment. In addition, the occupational therapist may provide a patient with strategies for completing activities of daily living with limited or no use of the affected hand while it is splinted or is recovering from surgery.

COMPLICATIONS

• The main potential complications of trigger finger are pain and decreased functional use of the affected hand.

• Potential complications of corticosteroid injection include the following:

  • Infection - The use of sterile technique can minimize this problem.

  • Bleeding - This can be minimized by applying direct pressure immediately after the procedure. Caution should be exercised before injecting a patient who is taking anticoagulants or an individual with a bleeding disorder.

  • Weakening of the tendon - This increases the risk of subsequent tendon rupture, a possibility that is of particular concern if the injection is performed incorrectly (specifically, if the injection is administered into the tendon itself rather than just within the tendon sheath).  The risk may increase with multiple injections; however, at least some clinical researchers (eg, Anderson and Kaye) have found no episodes of tendon rupture after corticosteroid injection for this condition, even with repeated injections.

  • Fat atrophy occurring locally at the injection site - Such atrophy can occur if the corticosteroid is injected into the subcutaneous tissue. This complication can cause a cosmetic depression in the skin, and tenderness can result from the loss of padding provided by the fat.

  • Nerve infiltration and subsequent nerve injury - This complication is uncommon; it can be be monitored by assessing sensation throughout the affected digit.

SURGICAL INTERVENTION

• A congenital nodule on the flexor pollicis longus tendon generally does not respond to injections. Therefore, it usually requires referral for surgical intervention.

• Trigger digits that fail to respond to 2 or perhaps 3 injections may require surgical treatment, including dissection of the nodule on the tendon and surgical release of the A1 pulley, under local anesthesia.

• Surgical release is highly effective, leading to a permanent resolution of the triggering symptoms. Such surgery should be reserved for patients in whom conservative treatment methods fail.

• When patients with diabetes were compared with persons who did not have diabetes, no statistically significant differences were found in surgical complication rates. This was also true when patients with type 1 diabetes were compared with individuals who had type 2 diabetes.

OTHER TREATMENT

• Corticosteroid injection in the area of tendon sheath thickening is considered to be the first-line treatment of choice for a trigger finger.

  • Typically, such an injection is performed using a 25-gauge needle to inject a mixture of 0.5-1 mL of 40 mg/mL corticosteroid (eg, methylprednisolone) and 0.5 mL of 1% lidocaine (without epinephrine).

  • Corticosteroid injections seem to be less effective in treating trigger finger in patients with diabetes mellitus; thus, patients with diabetes are more likely to require surgical treatment.

  • A second corticosteroid injection may be performed 3-4 weeks after the first one. If 2 or perhaps 3 injections fail to provide adequate resolution, consider referring the patient for surgical release. Repetitive injections theoretically increase the likelihood of tendon rupture, although such a risk was not found in Anderson's study of repeated injections for trigger fingers.

  • An increased risk of tendon rupture may potentially exist after corticosteroid injection, particularly if the corticosteroid is erroneously injected into the tendon itself rather than injected only into the tendon sheath.

  • Oral nonsteroidal anti-inflammatory drugs (NSAIDs) also may help.

• Although corticosteroid injection has traditionally been administered into the tendon sheath (but not into the tendon itself), studies now seem to indicate that subcutaneous injection may be as effective as the intrasheath approach. Additionally, in some cases, steroid injection into the subcutaneous tissue seems to result in better clinical outcomes than does injection into the sheath alone.

MEDICATION

For this musculoskeletal condition, medications are used primarily to decrease pain and inflammation in conjunction with the rehabilitation plan.

Thus, the most common medication treatments are focal corticosteroid injection and the administration of NSAIDs.

NONSTEROIDAL ANTI-INFLAMMATORY DRUGS

Oral NSAIDs can help to decrease pain and inflammation. Various oral NSAIDs can be used, although none of these agents holds a clear distinction as the drug of choice.

The choice of NSAID is largely a matter of convenience (how frequently doses must be taken to achieve adequate analgesic and anti-inflammatory effects) and cost. 

IBUPROFEN (Motrin, Advil, Nuprin, Rufen)

DOC for patients with mild to moderate pain. NSAIDs inhibit inflammatory reactions and pain by decreasing prostaglandin synthesis.

Adult: 200-800 mg PO tid/qid

Pediatric:

<6 months: Not established

6 months to 12 years: 4-10 mg/kg/dose PO tid/qid

>12 years: Administer as in adults

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Category D in third trimester of pregnancy; caution in congestive heart failure, hypertension, and decreased renal and hepatic function; to minimize risks of adverse effects, avoid taking multiple NSAIDs concurrently; caution in anticoagulation abnormalities or during anticoagulant therapy

CORTICOSTEROIDS

In contrast to the widespread systemic distribution that occurs when an oral anti-inflammatory drug is administered, a local corticosteroid injection can achieve the focal placement of a potent anti-inflammatory agent at the site of maximal tenderness or inflammation.

A variety of corticosteroid preparations are available. Commonly, the corticosteroid is mixed with a local anesthetic agent prior to injection. The clinician has numerous local anesthetic agents from which to choose. 

METHYLPREDNISOLONE (Depo-Medrol, Medrol, Adlone)

Corticosteroids are commonly used in local injections administered to bursae or joints. The drugs provide a local anti-inflammatory effect while minimizing some of the GI and other risks of systemic medications.

Adult:

40 mg (1 mL), intralesionally, is common for injection at many sites; often mixed with a few mL of a local anesthetic, such as 1% lidocaine.