Trigger Finger

Trigger finger (TF) is one of the most common upper limb problems to be encountered in orthopedic practice and is also one of the most common causes of hand pain and disability. It results from thickening of the flexor tendon within the distal aspect of the palm.[2, 3] This thickening causes abnormal gliding of the tendon within the tendon sheath. Specifically, the affected tendon is caught at the edge of the first anular (A1) pulley. (See Etiology and Pathophysiology.)

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.

The etiology of TF remains unknown or uncertain, although triggering seems to occur more frequently in patients with rheumatoid arthritis (RA) or diabetes mellitus (DM). (See Etiology and Pathophysiology.)

TF begins as discomfort in the palm during movements of the involved digit(s). Gradually or, in some cases, acutely, the flexor tendon causes painful popping or snapping as the patient flexes and extends the digit. The patient may present with a digit locked in a particular position, most often flexion, which may require gentle, passive manipulation into full extension. (See Presentation.)[1]

TF has a predilection for the dominant hand, with the most commonly affected digit being the thumb, followed by the ring, long, little, and index fingers. (However, a retrospective study of 577 TFs by Schubert et al found no relation to hand dominance.[10] ) The involvement of several fingers is not unusual.

Trigger finger occurs much less frequently in the pediatric population than in adults and develops almost exclusively in the thumb.[11] Historically, the condition in children has been referred to as congenital trigger thumb.[12] Evidence indicates, however, that it usually presents sometime after infancy and is thus more appropriately referred to as pediatric trigger thumb. (See Epidemiology and Presentation.)[13] Yet, by the time medical opinion is sought, surgery is usually indicated.

In the past, triggering of the digits was treated by splinting in extension, which caused stiffness and, consequently, loss of MCP and IP flexion. Out of dissatisfaction with this form of treatment, researchers used intrasheath steroid injections instead, which resulted in a high proportion of good results. (See Treatment and Medication.)[14, 10]

In an uncomplicated case of trigger digit, the first-line therapy is still generally agreed to be injection into the tendon sheath, with surgical release of the A1 pulley as second-line treatment.

Surgery, in the form of release of the A1 pulley, became popular when splinting and/or injection therapy failed or in the presence of other pathology, such as RA, in which injection treatment proved futile or there was a risk of tendon rupture or infection.

Fingers

Tendon sheaths of the long flexors run from the level of the metacarpal heads (distal palmar crease, superficial; volar plate, deep) to the distal phalanges. They are attached to the underlying bones and volar plates, which prevent the tendons from bowstringing. Predictable and efficient thickenings in the fibrous flexor sheath act as pulleys, directing the sliding movements of the fingers.

The two types of pulleys are anular (A) and cruciate (C). Anular pulleys are composed of single fibrous bands (ie, rings), whereas cruciate pulleys have two crossing fibrous bands.

The order of the pulleys from proximal to distal is as follows:

• The A1 pulley overlies the MCP joints; it is released during surgery for TF (see the image below)
• The A2 pulley overlies the proximal end of the proximal phalanx
• The C1 pulley overlies the middle of the proximal phalanx
• The A3 pulley lies over the PIP joint
• The C2 pulley lies over the proximal end of the middle phalanx
• The A4 pulley lies over the middle of the middle phalanx
• The C3 pulley lies over the distal end of the middle phalanx
• The A5 pulley lies over the proximal end of the distal phalanx

Flexor tendons pass within tendon sheath and beneath A1 pulley at approximately metacarpal head, beyond which they travel into digit.

The A2 and A4 pulleys are vital in preventing bowstringing of the flexor tendons and must be preserved or reconstructed after any damage to them.

Thumb

The flexor anatomy of the thumb differs from that of the fingers. The flexor pollicis longus (FPL) tendon is a single tendon within the flexor sheath that inserts onto the base of the distal phalanx. The fibro-osseous sheath is composed of two anular pulleys (A1 and A2) that arise from the palmar plates of the MCP and IP joints, respectively. The oblique pulley, which originates from and inserts onto the proximal phalanx, is the most important pulley from a biomechanical perspective. The oblique pulley is approximately 10 mm in length, blending with a portion of the adductor pollicis insertion.

The digital nerves and arteries run parallel to the tendon sheath distally. At the level of the MCP flexion crease, they lie just deep to the skin. Proximal to the A1 pulley, the radial digital nerve of the thumb crosses obliquely over the sheath.

A mismatch between the flexor tendon and the proximal pulley mechanism occurs in most cases of trigger finger. Normally, the tendons of the finger flexors glide back and forth under a restraining pulley.[15, 16, 17] 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. (See the image below.)

Inflamed nodule can restrict tendon from passing smoothly beneath A1 pulley. If nodule is distal to A1 pulley (as shown in this sketch), then digit may get stuck in extended position. Conversely, if nodule is proximal to A1 pulley, then patient's digit is more likely to become stuck in flexed position.

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.

Using sonoelastography, a newer technique for quantitative assessment of the stiffness of soft tissues, the data from one study noted that the causes for snapping in TF were increased stiffness and thickening of the A1 pulley. Three weeks after corticosteroid injection, the pulley thickness and the ratio of subcutaneous fat to the pulley both decreased; snapping disappeared in all patients studied.[18]

The etiology of trigger finger is unknown or uncertain. It is suspected that nodule formation in the tendon, morphologic changes in the pulley, or both in combination may effect triggering, though why these changes are actually initiated remains unknown.

Several studies have demonstrated a correlation between TF and activities that require exertion of pressure in the palm while a powerful grip is used or that involve repetitive, forceful digital flexion (eg, arc welding, use of heavy shears). Proximal phalangeal flexion in power-grip activities causes high anular loads at the distal edge of the A1 pulley. Hueston and Wilson have suggested that bunching of the interwoven tendon fibers causes the reactive intratendinous nodule observed at surgery.[19]

Thus, in conclusion, the exact etiology remains unknown, but certain conditions such as DM or RA may predispose an individual to triggering of the digit.

Sampson et al concluded that the underlying pathobiologic mechanism for triggering is fibrocartilaginous metaplasia of the pulleys due to trauma or disease.[20] Several studies have failed to demonstrate the presence of acute or chronic inflammatory cells within the tenosynovium. The suffix -itis in the term stenosing tendovaginitis actually is a misnomer unless the condition is associated with RA or inflammatory arthritis.

The exact etiology is still unknown, but it is thought that DM or autoimmune conditions may contribute to morphologic changes in the pulley and/or the tendon sheath to cause triggering. Systemic causes of TF are collagen-vascular diseases, including the following[21] :

• RA
• DM
• Psoriatic arthritis
• Amyloidosis
• Hypothyroidism
• Sarcoidosis
• Pigmented villonodular synovitis

Septic causes of TF are secondary infections (eg, tuberculosis). A few case reports have documented rare causes of TF, including tenosynovitis that itself resulted from a Mycobacterium kansasii infection in an immunocompetent patient; triggering following the development of calcific tendonitis has been reported in a child. Such cases should invoke a high degree of suspicion.

The association of idiopathic TF with idiopathic carpal tunnel syndrome has long been suggested. A study of 551 patients with no predisposing causes diagnosed with either TF, carpal tunnel syndrome, or both based on clinical grounds reported that 43% of patients with TF also had concomitant carpal tunnel syndrome; this is significantly higher than the population prevalence of carpal tunnel syndrome, which is about 4%.[22]

A retrospective study by Grandizio et al indicated that the risk of developing TF following surgical carpal tunnel release is greater in patients with DM than in those without DM. In the study, the investigators found that out of 1003 carpal tunnel releases in patients without DM, the incidence of TF at 6 and 12 months was 3% and 4%, respectively, whereas out of 214 carpal tunnel releases in patients with DM, the incidence at 6 and 12 months was 8% and 10%, respectively. The severity of the DM, however, was not found to be a significant factor in the development of TF.[23]

Trigger thumb

Trigger thumb (see the image below) usually occurs idiopathically, though it develops more frequently in individuals with diabetes or osteoarthritis. Trigger thumb is more likely to occur in an individual with any condition that causes diffuse proliferation of the tenosynovium, such as inflammatory arthritis, gout, or chronic infection (eg, fungus, atypical mycobacteria). This process can extend distal to the MCP joint and, when severe, cause stiffness rather than intermittent triggering.

Trigger thumb. A1 pulley exposed within surgical field (arrow). Digital neurovascular bundles behind retractors.

Certain people appear more prone to tenosynovitic conditions; patients with trigger thumb are more likely to develop carpal tunnel syndrome and de Quervain disease. The roles of overuse and trauma in trigger thumb are controversial, though the condition does have a predilection for the dominant hand.

Trigger finger is a relatively common condition and occurs two to six times more frequently in women than in men.

Several series found the peak incidence of trigger digit to be in individuals aged 55-60 years. Age distribution has not changed significantly despite an increase in computing activities and repetitive tasks. As previously mentioned, TF in the pediatric population occurs much less frequently than in adults and develops almost exclusively in the thumb.[11]

Injection with or without splinting

The prognosis in trigger finger is very good; most patients respond to corticosteroid injection with or without associated splinting. Some cases of TF may resolve spontaneously and then reoccur without obvious correlation with treatment or exacerbating factors.

Freiberg et al found a greater success rate for TF injection therapy when the treatment was used in patients in whom an examiner could palpate a discrete, rather than a diffuse, nodular consistency in the flexor sheath.[24] Digits with a discrete, palpable nodule had a 93% success rate with a single injection of triamcinolone at 3 months' follow-up, whereas digits with a diffuse pattern had a 52% failure rate.

Marks and Gunther reported an 84% success rate in trigger digits and a 92% success rate in trigger thumbs following a single injection of triamcinolone.[14]

Using sonoelastography, a newer technique for quantitative assessment of the stiffness of soft tissues, one group noted that the causes for snapping in TF were increased stiffness and thickening of the A1 pulley. Three weeks after corticosteroid injection, the pulley thickness and the ratio of subcutaneous fat to the pulley both decreased; snapping disappeared in all patients studied.[18]

Griggs et al reported an overall success rate of 50% for steroid injection in patients with DM.[25] Patients with insulin-dependent diabetes had a higher incidence of multiple digit involvement and required surgical release more frequently than did patients who were not insulin-dependent.[26, 27]

Surgery

Patients who need surgical release generally have a very good outcome. Percutaneous trigger finger release has been reported by several authors to be safe and efficacious, with success rates of 74-94% and no complications having been found at medium-term follow-up. The procedure is advised for individuals with established primary TF who have symptoms lasting longer than 4 months or for patients in whom injection therapy has failed to relieve symptoms. It is considered a reasonable choice following one injection failure and actually may confer cost benefits through permanent relief.

The prognosis is also very good for congenital trigger thumb that is treated with resection of the tendon nodule.

A study suggests that perioperative characteristics and outcomes differ between TF and trigger thumb and that the surgical outcome is poorer for TF than for trigger thumb (partly due to flexion contracture of the PIP joint).[28]

Pediatric

Triggering may resolve spontaneously in 23-63% of pediatric cases. If patients are not treated by the time they have reached the age of 4 years, some may be left with permanent flexion contractures. Surgical release of the A1 pulley prior to this age leads to excellent results.[29, 30, 9]

As with patient education following any local injection, patients should be told to watch for signs and symptoms of infection and bleeding. Any suggestion of infection or excessive bleeding should be reported to the physician immediately.

Patients should understand that some increased tenderness may be noted at the injection site for 2-4 days, until the corticosteroid begins to have a significant therapeutic effect. If there is an inordinate amount of pain after the procedure, patients should contact the physician who performed the injection.

Patients should understand that a certain amount of numbness in the digit may occur if some of the local anesthetic has come into contact with a digital nerve; however, the numbness should resolve within a matter of hours after the injection. Significant, persistent numbness should be reported to the physician who performed the injection.

To minimize the risk of tendon rupture after corticosteroid injection, the patient should be advised that for a few weeks after the injection, he or she should avoid using the injected structures for excessively strenuous or forceful activity.

Patients with trigger finger (TF) may have a history of diabetes mellitus (DM) or rheumatoid arthritis (RA). In these individuals, multiple digits may be involved in TF.

Some patients will have a history of repetitive trauma to the affected area, while others may have occupational duties requiring repetitive use of the involved tendons.[31]

Signs and symptoms of TF are as follows:

• Locking or catching during active flexion-extension activity (passive manipulation may be needed to extend the digit in the later stages)
• Stiff digit, especially in long-standing or neglected cases
• Pain over the distal palm
• Pain radiating along the digit
• Triggering on active or passive extension by the patient
• Palpable snapping sensation or crepitus over the A1 pulley
• Tenderness over the A1 pulley
• Palpable nodule in the line of the flexor digitorum superficialis (FDS), just distal to the metacarpophalangeal (MCP) joint in the palm
• Fixed-flexion deformity in late presentations, especially in the proximal interphalangeal (PIP) joint
• Evidence of associated conditions (eg, RA, gout)
• Early signs of triggering in other digits (may be bilateral)

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.

Some patients have difficulty with finger flexion rather than extension, though 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 report swelling of the affected digit, particularly at the digit's base or proximal aspect.

Pediatric

Children with trigger thumb rarely complain of pain. They usually are brought in for evaluation when aged 1-4 years, when the parent first notices a flexed posture of the thumb’s interphalangeal (IP) joint. These children often demonstrate bilateral fixed flexion contractures of the thumb by the time they present to the physician.[4]

At the level of the distal palmar crease, a tender nodule can be palpated, usually overlying the 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. (See the image below.)

Trigger finger often results in difficulty flexing or (in this case) extending metacarpophalangeal joint of involved digit.

In severe cases, the patient is unable to move the digit beyond the restriction, and thus 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.

Trigger finger (TF) is a clinical diagnosis. Occasionally, the nodule in the tendon is easily felt, and a palpable and audible click can be appreciated when the triggering is relieved with forced extension of the digit.

As a rule, no lab tests are needed in the diagnosis of TF. If there is a concern regarding an associated, undiagnosed condition, such as diabetes mellitus (DM), rheumatoid arthritis (RA), or another connective tissue disease, tests such as those assessing glycosylated hemoglobin (HbA1c), fasting blood sugar, or rheumatoid factor (RF) should be ordered.

Radiography rarely is indicated in TF.[5] Hand radiographs are performed only if abnormal pathology (eg, abnormal sesamoids, loose bodies in the metacarpophalangeal [MCP] joint, osteoarthritic spurs on the metacarpal head, or avulsion injuries of collateral ligaments) is suspected.

Radiographs are helpful to exclude osteoarthritis, fracture malunion, foreign body, or a large sesamoid bone that is affecting interphalangeal (IP) joint motion.

The A1 pulley exhibits a marked degree of hypertrophy, described as a white, cicatricial, collarlike thickening. Microscopy demonstrates degeneration, cyst formation, and plasma-cell infiltration. Microscopic studies have also shown chondrocytic proliferation of type III collagen instead of chondrocyte presence in the normal innermost or friction layer of the A1 pulley.[33] The amount of extracellular matrix is increased significantly when compared with controls.

Green's classification of triggering is used only for clinical grading and documentation. No correlation has been established between the grading scheme and the outcome following injection therapy. The various grades are defined as follows[34] :

• Grade I (pretriggering) - Pain; history of catching that is not demonstrable on clinical examination; tenderness over the A1 pulley
• Grade II (active) - Demonstrable catching, but with the ability to actively extend the digit maintained
• Grade III (passive) - Demonstrable locking in which passive extension is required (grade IIIA) or in which the patient is unable to actively flex (grade IIIB)
• Grade IV (contracture) - Demonstrable catching, with a fixed flexion contracture of the proximal interphalangeal (PIP) joint

Early series recommended surgical treatment of trigger finger (TF) as straightforward and highly effective, while regarding prolonged conservative treatment as unreliable and expensive. Subsequent series documented poor results from surgical treatment in 7-9% of cases.

In 1972, Lapidus reversed his previous recommendation for operative treatment of TF after he and Guidotti reported uniformly good results following a single injection of prednisolone into the tendon sheath.[35] Rhoades et al subsequently reported a 72% success rate in a series of 53 digits following injection and immobilization.[36]

Injection therapy is now generally agreed to be the first line of management. Surgery is reserved for individuals in whom injection treatment has failed or in whom other pathology, particularly rheumatoid arthritis (RA), is suspected to be causing triggering that cannot be treated conservatively.[37] No absolute contraindications exist for surgical management.

In May 2014, the European HANDGUIDE Group published a guideline for multidisciplinary treatment of trigger finger.[38] By consensus, suitable treatment options were considered to include the following:

• Orthoses (splinting)
• Corticosteroid injections
• Corticosteroid injections plus use of orthoses
• Surgery

Severity and duration of disease and prior treatments received were judged to be the primary factors influencing choice of therapy.[38]

Conservative treatment

Most trigger digits in adults can be managed successfully with local steroid injections and splinting.[39] Oral or topical pharmacologic measures have not been demonstrated to be effective. A 2021 Cochrane review found that injection of nonsteroidal anti-inflammatory drugs offered little or no benefit as compared with steroids.[40]

The outcome of conservative treatment for pediatric trigger thumb is somewhat controversial.[41] A report by Baek et al on the natural history of this condition demonstrated that after a follow-up period of 5 years or more in patients who received no treatment for pediatric trigger thumb, complete resolution of flexion deformity occurred in 66 out of 87 thumbs (75.9%), and partial improvement occurred in the remaining 21 thumbs.[30, 42]

Another study, by Lee et al, reported that extension splinting for 12 weeks led to improvement in 71% of thumbs, compared with 23% improvement in patients not receiving any treatment.[43] See also the recommendations described by Ogino.[44]

Surgical release

The chief indications for surgical management of TF are as follows:

• Failure of splinting and/or injection treatment
• Irreducibly locked TF
• Trigger thumb in infants - Without surgical release, these infants are likely to develop a fixed flexion deformity of the interphalangeal (IP) joint

Although the results of percutaneous release are well established, the open technique is absolutely essential for the thumb or little finger or in the presence of proximal interphalangeal (PIP) contractures. Percutaneous release should be reserved for the index, middle, and ring fingers.[6, 7, 8, 9]

In a study from Oxford comparing percutaneous and open surgical methods, the two approaches displayed similar effectiveness, and both proved superior to conservative corticosteroid-injection treatment with regard to trigger cure and relapse rates.[45]

In children, triggering has varying causes. Release of the A1 pulley alone does not always correct the problem. Additional treatment (eg, resection of one or both limbs of the flexor digitorum superficialis [FDS] tendon, A3 pulley release) may be required and is recommended in RA tenosynovitis.[9, 46, 47, 48]

In infants, the nodule on the flexor pollicis longus (FPL) tendon can be resected with good results. Corticosteroid injections are generally not helpful in these cases of trigger thumb.

Pregnant patients

Splinting and local corticosteroid injection can be performed if the patient is pregnant. Surgical release of the A1 pulley is generally an elective procedure and is usually deferred until after delivery.

Elderly patients

In elderly patients with a history of gastrointestinal problems or other complications from nonsteroidal anti-inflammatory drugs (NSAIDs), consider cyclo-oxygenase-2 (COX-2) inhibitors if oral NSAIDs are needed.

Consultations

Surgical consultation for operative treatment may be required. Typically, such procedures are performed by an orthopedic hand surgeon or a plastic surgeon.

Corticosteroid injection in the area of tendon sheath thickening is considered to be the first-line treatment of choice for TF.[49, 50, 51, 52, 10] Research in 2009 concluded that the most successful and cost-effective management strategy for TF is the algorithm of two steroid injections prior to surgical intervention, if needed.[53]

A variety of preparations have been used—most commonly prednisolone, dexamethasone, and triamcinolone—in the steroid injection treatment of TF, and most are uniformly successful in relieving symptoms.[54, 49, 55, 56]

A highly satisfactory rate of success can be predicted in female patients and in patients with single digit involvement, short duration of symptoms (ie, < 4 months), no associated conditions (eg, RA, diabetes mellitus [DM]), or a discrete, palpable nodule. (Patients with RA or DM seem to be more resistant to injection treatment.)[26, 27, 57]

Procedure

The author's technique for steroid injection is as follows. A mixture of triamcinolone, 1% lidocaine, and 0.5% bupivacaine is used, in a ratio of 2:1:1, respectively; adrenaline is not used. The nodule in the palm is well localized and circled out using an indelible skin marker. The procedure is performed in an office setting, using strict aseptic precautions, with alcoholic povidone-iodine used for injection-site preparation. Ethyl chloride is used only if requested; frequently, it is unnecessary, and most patients tolerate this procedure quite well

A 26-gauge needle is introduced in a proximal-to-distal direction in the nodule, making an angle of 45° with the palm (see the first image below). The needle enters the nodule with a distinct grating sensation; positioning of the needle is verified by asking the patient to move the digit when it is possible to clearly observe the needle moving with the digit (see the second image below)

Introduction of needle into tendon sheath at 45° angle to palm for injection treatment.

Movement of needle with flexion of digit confirms correct positioning of needle for injection treatment.

The syringe with the steroid preparation then is attached to the needle. Attempting to inject the drug with light pressure confirms the intratendinous location of the needle. Do not inject the solution if significant resistance to injection flow is noted, because this may indicate that the needle tip is in the tendon rather than just within the tendon sheath. The needle is withdrawn very carefully until a give-way sensation is felt, indicating that the tip of the needle is out of the tendon and in the sheath. The preparation is then injected.

A small water-impermeable dressing is applied. The patient is actively encouraged to move the digit; in most cases, the triggering is relieved

(Carlson and Curtis prefer a midaxial injection at the level of the midproximal phalanx as a simple and painless way to access the flexor sheath for the purpose of injection.[58] )

A follow-up appointment is made for 3-4 weeks after the treatment. Splinting is not used routinely for these cases, though a hand-based MP-block Orthoplast splint has been described as useful.

Although injection treatment has long been administered by "feel" and experience, research suggests that using ultrasonographically guided steroid injection may maximize the injection's accuracy and, consequently, its beneficial effects in the treatment of trigger digits.[59, 60]

No major complications from injection treatment are noted. A transient rise in blood and urine sugar levels is common in patients with diabetes. Advise these patients that this is likely to occur. Theoretically, repeated steroid injections could cause attrition and/or rupture of tendons, but only 1 such case has been reported to date.[61]

Pain relief

While corticosteroid injections into the palm are considered highly effective in treating TF, the injection itself may be significantly painful. A study that compared conventional injection with injection preceded by median and ulnar nerve blocks performed at the wrist found that of the study’s 19 patients, who were treated with 47 total injections, 88% preferred to have the median and ulnar nerve block prior to the injection.[62]

Both study groups, however, had excellent resolution of TF, with excellent resolution being defined in the study as an asymptomatic hand (without triggering) and a pain score on the 0-10 cm Visual Analog Scale of less than 2 cm.[62]

Repeat injections

A second corticosteroid injection may be performed 3-4 weeks after the first one. If two or perhaps three 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 TF.[63]

Alternative injection techniques

Proximal phalanx technique

Another injection method, the proximal phalanx technique, allows for injection directly into the tendon sheath through the palmar surface of the midproximal phalanx. Injections performed this way were found to be less painful than injecting the flexor tendon sheath directly over the metacarpal head. There was no statistically significant difference in the rate of recurrent pain between the two injection methods.[64]

Subcutaneous injection

Although corticosteroid injection has traditionally been administered into the tendon sheath (but not into the tendon itself),[61] studies seem to indicate that subcutaneous injection may be as effective as the intrasheath approach.[65, 66, 67] Additionally, in some cases, steroid injection into the subcutaneous tissue seems to result in better clinical outcomes than does injection into the sheath alone.[65]

Custom-made splinting of the metacarpophalangeal (MCP) joint is another conservative treatment, used in patients who do not wish to undergo a steroid injection or as an adjuvant to injection. Typically, a custom-made splint is used to hold the MCP joint of the involved finger at 10-15° of flexion, leaving the PIP and distal interphalangeal (DIP) joints free. The average length of splinting is 6 weeks. In patients with symptoms longer than 6 months, splinting as a sole treatment strategy does not seem to eliminate the triggering events.[21]

Although traditionally splinting has not been thought to be an effective treatment for TF, one study of thermoplastic splinting of MCP joint flexion showed improvement in stenosing tenosynovitis, the numeric pain rating scale, and the number of triggering events and also demonstrated an overall perceived participant improvement in symptoms.[68] Another study determined that 87% of patients who wore custom-made, thermoplastic orthoses for 8-10 weeks did not require an injection or surgical intervention in the 1-year follow-up after institution of the orthoses.[69]

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

The benefits of operative treatment of trigger finger and trigger thumb were outlined in three studies of surgical pulley release.

Between 1994 and 2004, Li et al treated seven children (nine thumbs; three right, two left, two bilateral) for trigger thumb with hyperextensible MCP anomaly (>60°) by surgical release of the first anular pulley (A1 pulley) and proximal advancement of the MCP volar plate. The patients (four girls, three 3 boys), who had a mean age of 46 months at surgery (range, 26-82 months), were observed over a mean follow-up period of 64 months (range, 1-8 years).

All patients in the study at last follow-up had returned to full activity without limitation or pain, and none of the patients had a recurrence of triggering or MCP hyperextension deformity, demonstrating, according to the authors, that trigger thumb with concomitant MCP hyperextension deformity can be treated in children by A1 pulley release and advancement of the volar plate.[13]

In a study of 93 trigger thumbs in 83 patients, Chao et al compared the results of miniscalpel-needle percutaneous release with those of steroid injection. At 12 months, 44 of the 46 trigger thumbs treated with the miniscalpel-needle release had satisfactory results (measured by visual analogue pain scale and patient satisfaction), but only 12 of 47 thumbs treated with steroid injection had satisfactory results. No nerve injuries occurred in either group.[70]

Trigger thumb in children almost always calls for surgical management. Trigger thumb in an adult not responding to corticosteroid tendon sheath injection needs surgery. The technique of release itself is irrelevant. Open and not percutaneous surgery is the norm for trigger thumb in children and adults alike, since the neurovascular bundles in the thumb are closer to the midline than in other digits. A single series (quoted above) comparing the efficacy of percutaneous surgery vis-a-vis a corticosteroid injection found surgery still to be more effective than injection treatment, but this technique of surgical release itself is not de rigueur.

Lange-Rieb et al presented long-term results of open operative treatment of TF and trigger thumb in adults. Of the operations performed, 210 (76%) were for a single-digit release and 76 (24%) for multiple digits. All operations were performed under tourniquet control with local anesthesia as outpatient procedures using a transverse incision just distal to the distal palmar crease or on the flexor crease of the thumb at the MCP joint. At latest follow-up (average, 14.3 years), 234 patients were evaluated, with no complaints, and there were no serious complications, such as nerve transection or bowstringing, or recurrence.[71]

Preparation for surgery

Preoperative considerations include the following:

• Only digits that actively trigger must be considered for operative release
• Neither PIP contracture nor thumb triggering is suitable for percutaneous release, and the A1 pulley always is transected under direct vision
• Patients with PIP joint contractures undergo a period of hand therapy and splinting prior to the procedure
• A tourniquet always is used to obtain a clean operative field
• Approximately 4-5 mL of 1% lidocaine is used to infiltrate the skin overlying the A1 pulley, with injection performed deeper to the tendon sheath
• The transverse incision is marked with a skin marker corresponding to the digit to be surgically treated (see the image below)
• The proximal edge of the A1 pulley coincides almost exactly with the distal palmar crease in the fourth and fifth rays, with the proximal palmar crease in the index and with the halfway point between the two creases in the middle finger

Incision marked out in distal palmar crease for surgical division of A1 pulley.

Operative details

The MCP joint is hyperextended to displace the neurovascular structures dorsally, minimizing the risk of injury.

A transverse incision measuring 1-1.5 cm is made over the involved metacarpal head. Blunt dissection is used to spread the subcutaneous fat and expose the tendon sheath.

The proximal edge of the A1 pulley is identified, and a scalpel blade is used to divide the entire A1 pulley in the midline under vision. Care is taken to avoid incising too distally and risk cutting into the A2 pulley, which can result in bowstringing. A study suggests that the proximal part of the A2 pulley can be safely incised if the release of the A1 pulley in isolation does not result in relief of triggering.[72] This is still experimental and is best left to hand or plastic and reconstructive surgeons.

The patient is asked to actively move the digit to confirm full release. Meticulous hemostasis is achieved with a bipolar cautery, and the wound is closed with two or three skin sutures. The hand is left free, and motion is encouraged immediately following the procedure.

If a percutaneous approach is favored, a pair of blunt-tipped, fine scissors is introduced through the incision, and the A1 pulley is transected (see the image below). Care is taken not to drift too distally. Disappearance of a grating sensation indicates complete section of the pulley through a separate, distal oblique incision.

A1 pulley is sectioned by using blunt-tipped, fine scissors, keeping strictly in midline. Note digit being held in hyperextended position by assistant to displace neurovascular bundles away from midline.

A study by Rogo-Manaute et al showed that it is possible to use ultrasonographically guided percutaneous release to achieve a success rate of 100%. With adequate anatomic knowledge, technical training, and a basic ultrasound machine, sonographically directed A1 pulley release can be performed safely and successfully, thus offering an alternative to conventional open technique.[73]

On rare occasions, sectioning the A1 pulley does not relieve triggering, indicating that the A3 pulley might be involved. If that is the case, the A3 pulley requires division. This percutaneous technique as described here usually applies to most cases of triggering, exceptions being surgery for trigger thumb in children and triggering involved in conditions like RA, in which the nodule formation may be distal to the A1 pulley and for which open surgery may be required.

Trigger thumb

Surgery for trigger thumb is performed as follows. The A1 pulley is approached through a transverse incision in the flexion crease overlying the MCP joint (see the image below). Palpate the FPL to ensure that the incision is centered appropriately.

Incision for trigger thumb release placed in metacarpophalangeal flexion crease, centered over flexor tendon nodule.

Bluntly dissect through subcutaneous tissue; identify and gently retract radial and ulnar neurovascular bundles. Expose the A1 pulley, identify its proximal and distal edges, and incise it longitudinally (see the first image below).[74]  Avoid injury to the underlying tendon (see the second image below).

Trigger thumb. A1 pulley exposed within surgical field (arrow). Digital neurovascular bundles behind retractors.

Trigger thumb. A1 pulley has been released; flexor pollicis longus tendon is now exposed. Retractors have been removed to demonstrate proximity of neurovascular bundles (arrows) to tendon.

Inspect the tendon nodule during full passive motion of the IP joint. Ensure that no further restrictions to excursion are present. A band of tissue proximal to A1 may exist that also requires release.[75] Observe FPL excursion while the patient actively flexes the thumb to verify a complete surgical decompression.

Deflate the tourniquet, obtain hemostasis, and close the incision with nylon. Dress the wound with a soft compressive bandage

Postoperative care

Active motion is encouraged on the day of surgery. Anti-inflammatory drugs and elevation are advised for a period of 2-3 days following surgery. Sutures are removed on postoperative day 10.[76]

Future treatment for TF may involve Kapandji enlargement-plasty of the A1 pulley. In this procedure, which is complex and technically demanding, the A1 pulley is enlarged by making a diagonal incision in it, followed by suture instead of simple longitudinal division, thus increasing the mean diameter of the canal.

In a study by Migaud et al, 15 patients who underwent this procedure and who were followed up for a mean period of 5 years had complete symptomatic relief without any recurrences.[77]

Physical therapy is generally not required for patients with TF. For cases of chronic TF, 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. No therapy programs have been documented to improve TF.

If a trial of therapy is recommended for patients with chronic TF or for individuals who require postoperative hand therapy, the physician may refer them to either a physical therapist or an 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 (ADL) with limited or no use of the affected hand while it is splinted or is recovering from surgery.

Corticosteroid injection

Potential complications of corticosteroid injection include the following:

• Infection - The use of sterile technique can minimize this problem
• Bleeding
• Weakening of the tendon
• Fat atrophy occurring locally at the injection site
• Nerve infiltration and subsequent nerve injury - This complication is uncommon; it can be monitored by assessing sensation throughout the affected digit

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 tendon

Weakening of the tendon 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).[61, 78]

A study demonstrated that ultrasonographically guided injections were safer than blind injections in that 30% of fingers injected blindly demonstrated dye within the tendon, while no tendon injected under ultrasonographic imaging was infiltrated with dye.[37]

The risk of tendon rupture may increase with multiple injections, although at least some clinical researchers (eg, Anderson and Kaye) found no episodes of tendon rupture after corticosteroid injection for TF, even with repeated injections.[63]

Fat atrophy

Fat atrophy can occur locally at the injection site 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.

Surgical release

If the surgeon maintains a careful surgical technique, the incidence of complications should be low.[71] Potential complications of TF surgery include the following:

• Tenderness over the site of the incision - This occurs quite frequently but usually settles on its own
• Adhesions and subsequent stiffness - This may develop with excessive handling of the tendon or delayed postoperative mobilization
• Digital nerve injury - Overall, this is extremely rare, even though the digital nerves lie within 2-3 mm of the midline; prompt repair or reconstruction is indicated in the event of this unfortunate complication; observation for suspected neurapraxia is appropriate; digital nerve transection is the most common complication reported after trigger thumb surgery; the radial digital nerve is injured more frequently because of its superficial location and oblique course over the flexor sheath
• Superficial scoring of the FDS tendon - This has been reported frequently but does not require further treatment
• Accidental cutting into the A2 pulley - This can cause bowstringing, with loss of full finger flexion; pulley exploration and reconstruction may be indicated if bowstringing does not resolve
• Scarring - This is more likely to occur after TF surgery than after trigger thumb surgery
• Recurrence - This has been reported but is extremely rare
• Infection - This is a risk in patients who are diabetic or immunosuppressed and may be problematic if septic flexor tenosynovitis results

Research has shown no statistically significant differences in surgical complication rates between persons with diabetes and those without it. This was also found to be true when patients with type 1 diabetes were compared with individuals who had type 2 diabetes.[50]

For patients with trigger finger (TF), 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 at the site of maximal tenderness or inflammation and the administration of nonsteroidal anti-inflammatory drugs (NSAIDs).

The most common corticosteroid preparations used include prednisolone, dexamethasone, and triamcinolone. Commonly, the corticosteroid is mixed with a local anesthetic agent prior to injection.

Class Summary

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 (DOC). 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, NeoProfen, Provil)

Ibuprofen is the drug of choice for patients with mild to moderate pain. NSAIDs inhibit inflammatory reactions and pain by decreasing prostaglandin synthesis.

Diclofenac topical (Zorvolex, Zipsor, Cambia, Cataflam, Voltaren XR)

NSAIDs inhibit inflammatory reactions and pain by decreasing prostaglandin synthesis.

Ketoprofen

Ketoprofen has good anti-inflammatory properties and exceptional analgesic properties. It is a first-line medication because of its daily dosing, which helps with compliance. Small dosages are initially indicated in small and elderly patients and in those with renal or liver disease. Doses higher than 75 mg do not increase therapeutic effects. Administer high doses with caution, and closely observe the patient for response.

Naproxen or naproxen sodium (Naprelan, Naprosyn, Aleve, Anaprox)

Naproxen is used for relief of mild to moderate pain and inflammation; it inhibits inflammatory reactions and pain by decreasing activity of COX, which results in a decrease of prostaglandin synthesis. Naproxen is available in many dosages and delivery systems. It is fairly inexpensive and has a therapeutic profile similar to those of other NSAIDs.

Indomethacin (Indocin)

Indomethacin is used for relief of mild to moderate pain; it inhibits inflammatory reactions and pain by decreasing the activity of COX, which results in a decrease of prostaglandin synthesis.

Celecoxib (Celebrex)

Celecoxib primarily inhibits COX-2. COX-2 is considered an inducible isoenzyme, induced during pain and inflammatory stimuli. Inhibition of COX-1 may contribute to the GI toxicity of NSAIDs. At therapeutic concentrations, the COX-1 isoenzyme is not inhibited; thus, GI toxicity may be decreased. The lowest dose that is effective in a given patient should be given.

Class Summary

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 (A-Methapred, Depo-Medrol, Solu-Medrol, Medrol)

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 gastrointestinal and other risks of systemic medications.

Dexamethasone acetate (Baycadron)

This agent decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reducing capillary permeability. The dosage varies with the degree of inflammation and the size of the affected area.

Hydrocortisone acetate (Solu-Cortef, Cortef, A-Hydrocort)

Hydrocortisone acetate decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reversing increased capillary permeability. The dosage varies with the degree of inflammation and the size of the affected area.

Betamethasone (Celestone, Celestone Soluspan)

Betamethasone is the drug of choice for intra-articular injections. It does not crystallize if used with paraben-free anesthetic preparations.

Triamcinolone (Aristospan, Kenalog-10, Kenalog-40)

Triamcinolone is used for inflammatory conditions responsive to steroids; it decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reversing capillary permeability. This is the preferred drug, owing to its longer duration of action.