Alexander M. Marcus
DEFINITION
Trigger finger is an entrapment of the digital flexor tendon(s) by the flexor tendon sheath.
Trigger finger progressively causes inflammation, pain, catching, locking, and reduced range of motion (ROM).
ANATOMY
The flexor digitorum profundus and superficialis (flexor pollicis longus in the thumb) pass under (dorsal to) the flexor sheath, which consists of annular and cruciate pulleys.
The A1 pulley, which is volar to the metacarpophalangeal joint (MCP), is the most proximal pulley (except for a thickening known as the palmar aponeurotic pulley6), and is almost always the primary site of entrapment (FIG 1).
PATHOGENESIS
High angular loads at the A1 pulley and often, other causes of local inflammation result in a flexor tendon sheath whose inner diameter is too narrow to accommodate the flexor tendon(s).
This size mismatch causes hypertrophy (thickening) of the A1 pulley and tendinous swelling.
These changes exacerbate the size discrepancy, setting up a cycle in which entrapment causes hypertrophy and hypertrophy causes entrapment.
NATURAL HISTORY
Trigger digits may develop spontaneously or may occur after swelling, from either trauma or a period of heavy use.
Trigger digits may:
Resolve spontaneously (especially in mild cases)
Persist with the same level of symptoms
Advance to passively correctable locking
Become indefinitely locked in either flexion or extension
PATIENT HISTORY AND PHYSICAL FINDINGS
The history may include any of the following:
Pain in the distal palm, often radiating proximally along the path of the flexor tendon
Pain occurring with use, and difficulty grasping objects or flexing the digit
Clicking or locking with digital flexion and extension, which is often perceived to be at the proximal interphalangeal joint (PIP)
The finger being stuck in flexion, often in the morning, requiring the other hand to straighten it
Being unable to flex or extend the digit fully, or at all (FIG 2)
The history should elicit the following information:
Whether the patient has had a trigger finger before, in either the currently involved or any other digit
Previous treatments for trigger finger, and the extent and duration of the result
FIG 1 • To understand trigger finger and its release, an appreciation of the flexor tendon pulley system of the finger (A) and thumb (B) is required.
FIG 2 • Reduced flexion caused by ring finger triggering.
Whether the condition began after a particular incident or period of increased hand use
The patient's medical history should be evaluated for conditions that may cause trigger fingers and alter treatment, as well as commonly associated conditions, including:
Diabetes
Rheumatoid arthritis and other inflammatory arthropathies
Amyloidosis, most commonly secondary to renal disease requiring dialysis
Lysosomal storage diseases
Carpal tunnel syndrome (often seen in patients with trigger finger, but not causally related)
The history and physical examination should exclude other conditions that cause overlapping symptoms, including:
Nerve compression
Muscle weakness
Tendon interruption from laceration (partial or complete) or rupture
Pulley rupture and bowstringing
Joint or soft tissue contracture or swelling, or both
Extensor tendon laceration or subluxation, especially at the MCP joint
Joint dislocation
The physical examination should include the following:
ROM test, which is the most objective measure of severity. If the patient has absolutely no active motion at the PIP (or thumb IP), consider tendon interruption.
Palpation of the palm. If the A1 pulley is not tender, strongly consider other diagnoses. Examine for other causes of the patient's symptoms, including Dupuytren's contracture, tendon sheath ganglion, PIP joint injury, and A3 pulley triggering.
Examination of the extensor apparatus. Rule out extensor mechanism abnormalities that may cause overlapping signs or symptoms, including a popping sensation with ROM.
Perform a neurovascular examination. Carpal tunnel syndrome often is associated with trigger finger. Muscle weakness may cause similar findings. Any neurovascular deficit should be documented before treatment.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Radiographs can exclude some unusual causes of trigger finger symptoms and can assess for arthritis, but are not required to make the diagnosis of trigger finger.
If other pathology is suspected, MRI can be useful.
Nerve conduction studies can evaluate for anterior interosseous nerve (AIN) compression, which may mimic a trigger thumb or concomitant carpal tunnel syndrome.
DIFFERENTIAL DIAGNOSIS
Extensor tendon subluxation at the MCP joint
Joint contracture or injury, including MCP locking due to collateral ligaments and a swollen PIP joint
Soft tissue swelling or contracture, including Dupuytren's contracture
Partial tendon laceration
Triggering at the A3 pulley (rare)
Muscle weakness, including flexor pollicis longus weakness secondary to AIN palsy
Masses (especially tendon sheath ganglions), which may cause A1 pulley tenderness
NONOPERATIVE MANAGEMENT
Observation and splinting
Mild, early cases often resolve spontaneously or do not bother the patient significantly.
Use of a night extension splint may help alleviate swelling and morning locking.
Unless the PIP joint remains locked, in either flexion or extension, for several weeks, delayed treatment usually does not significantly change either the options available or their results.
Injection
Long-term relief in most affected digits with one to three injections.2
Results in diabetic patients are not as good,1,4 but it still is worth trying.
Injection technique (FIG 3)
1 mL of 2% plain (no epinephrine) lidocaine and 1 mL of a soluble corticosteroid solution (eg, betamethasone or dexamethasone) in a single syringe with a 25-gauge needle is given.
FIG 3 • Technique for trigger digit injection.
The A1 pulley area is prepped with an antiseptic solution such as alcohol or betadine.
A topical spray may be used to reduce discomfort.
1 to 2 mL is injected in the sheath and subcutaneously.11 Avoid injecting into the tendon itself; if increased resistance is encountered, this may be the cause.
SURGICAL MANAGEMENT
Indications for surgical treatment include:
Symptoms that persist despite conservative management
Inability to flex or extend the finger even passively: this is an indication for earlier release to prevent secondary joint contracture.
Open A1 pulley release is indicated for any routine trigger finger.
Percutaneous trigger finger release:
Requires an actively triggering digit so the patient can flex to confirm needle placement and pulley release.
Is used primarily for the middle and ring fingers. Use in the other digits may place digital nerves in jeopardy.13
In patients with very extensive synovitis, such as that seen in rheumatoid arthritis, lysosomal storage diseases, or amyloidosis associated with end-stage renal disease, releasing the A1 pulley percutaneously or through a routine, small incision is contraindicated. A more extensive tenosynovectomy and sometimes ulnar slip of the flexor digitorum superficialis (FDS) resection (USSR) is required.
Preoperative Planning
Clinical notes and any studies obtained preoperatively should be reviewed.
If procedures beyond an A1 pulley release are being considered (eg, possible resection of the ulnar slip of the flexor digitorum superficialis), they should be discussed with the patient preoperatively.
Positioning
The patient is supine.
The extremity is positioned so that the palm is facing up on a hand table.
For index, middle, ring, and small digits, a hand holder (eg, a “lead hand”) is helpful.
For the thumb, it is more useful for the surgeon and assistant to position the hand and thumb throughout the procedure or to use a specialized thumb holder.
Place a padded tourniquet and inflate it just before making the incision.
Approach
Anesthesia is obtained by injecting 2% plain (no epinephrine) lidocaine subcutaneously around the incision and in the tendon sheath.
Sedation will mitigate the discomfort associated with the injection and the tourniquet. If sedation is used, the patient should be allowed to wake up in time to demonstrate complete active digital flexion and extension without locking, documenting successful pulley release.
A standard volar approach to the A1 pulley is made with either an oblique, transverse, or longitudinal incision.
For resection of the ulnar slip of the sublimis, a Bruner-type or midaxial longitudinal incision is used over the distal portion of the proximal phalanx.
TECHNIQUES
OPEN A1 PULLEY RELEASE
Incision and Exposure
A 1-cm incision is placed over the A1 pulley.
Longitudinal (TECH FIG 1A)
If a transverse incision is used, it is placed in a palmar skin crease (TECH FIG 1B):
Distal palmar crease for small and ring fingers
Proximal palmar crease for index finger
An incision between creases may be required for middle finger release
Oblique or Bruner-type
Avoid crossing palmar skin creases at a right angle with any incision type.
Incise only the skin and dermis with a no. 15 blade.
Bluntly spread subcutaneous tissue to avoid injury to the digital nerves.
The digital neurovascular structures adjacent to the A1 pulley must be retracted and protected.
Extensive dissection and exposure of these structures is not required.
The radial digital nerve of the thumb is at the greatest risk because it typically crosses the surgical field (TECH FIG 1C).
TECH FIG 1 • A. A longitudinal incision for ring finger A1 release. Index finger demonstrates a well-healed longitudinal incision without any contracture. B. Position of transverse incisions for trigger finger release in relation to the palmar skin creases and the A1 pulley. C. The digital neurovascular structures are right next to the A1 pulley and must be protected. This schematic demonstrates the proximity of the digital nerves and arteries. Because the radial digital nerve of the thumb may cross at the level of the A1 pulley, it is particularly vulnerable.
Performing the Release
Clear off the A1 pulley with sponge dissection.
The A1 pulley is not incised until it is clearly visualized (TECH FIG 2A).
Use of small right-angle retractors helps provide needed visualization.
Begin the A1 pulley incision with a knife, taking care not to cut deep into the tendon.
Complete the release with scissors until the pulley leaflets can be spread completely apart (TECH FIG 2B).
Avoid cutting any significant portion of the A2 pulley (or the oblique pulley in the thumb).
TECH FIG 2 • A. The digital neurovascular structures are retracted, and the A1 pulley has been cleared of all overlying soft tissue. B. The A1 pulley has been completely released. C. The palmar pulley remaining after A1 release. D. The flexor tendons are bluntly separated and pulled out of the wound, which then flexes the digit. (A–D. Top is proximal.)
TECH FIG 3 • A. Tenosynovium between the tendons can be gently removed. B. A tendon sheath mass. Pathologic analysis confirmed it was a tendon sheath ganglion. C,D. Full active flexion and extension after release.
The A2 pulley is separated from the A1 pulley either by a space (where there is no sheath) or a section of very thin sheath tissue.9
If the tendons appear constricted by the palmar aponeurotic pulley6 proximal to the A1 pulley, it should also be released (TECH FIG 2C).
Bluntly separate the tendons (in the fingers) and pull the tendon(s) out of the wound (TECH FIG 2D). Minimize any direct handling of the tendons.
Completion
A limited tenosynovectomy may be performed if required (TECH FIG 3A). Any unusual resected tissue or mass is sent to the pathology department for analysis (TECH FIG 3B).
Confirm that the patient can actively flex and extend the finger (TECH FIG 3C,D). If the active ROM is not full or significantly improved, or if the tendons are not passing under the remaining pulleys, consider ulnar slip of the flexor digitorum superficilias resection (USSR) as well as etiologies other than standard trigger finger.5,7,8,10
Release the tourniquet, and irrigate the wound.
Obtain hemostasis, usually with manual compression. Reinspect the wound, check for any arterial bleeding, and confirm the finger has brisk capillary refill.
Close the skin with interrupted sutures and place a mildly compressive dressing.
PERCUTANEOUS A1 PULLEY RELEASE
The patient must have active triggering.
The procedure is performed with a sterile prep in either the office or operating room.
Hyperextend the MCP joints over a towel to help displace the neurovascular structures dorsally.
Palpate the A1 pulley.
Inject the local anesthetic (with or without corticosteroid) as described for nonoperative treatment.
An 18- or 19-gauge needle is placed through the A1 pulley, centered radial to ulnar, and into the tendon (TECH FIG 4).
The patient actively flexes the finger which moves the needle, confirming location.
The needle is pulled back slightly so that it remains in the A1 pulley, but not the tendon.
The needle is rotated so that the bevel is in line with the longitudinal axis of the pulley.
Sweep the needle proximally and distally until grating is no longer felt.
The patient should be able to actively flex and extend the finger without triggering, confirming release.
Open A1 Pulley Release With FDS Ulnar Slip Excision (USSR)
The initial steps are performed in the same manner as described for an open A1 pulley release.
A Bruner-type or ulnar midaxial incision is made over the proximal phalanx.
For a Bruner-type incision, a zigzag skin incision is made with the points over the finger flexion creases (TECH FIG 5).
The skin only is opened with a no. 15 blade, and blunt dissection is used to separate the neurovascular bundles as a unit. Formal dissection of the nerve and artery, or separating them from each other, is not required.
Care should be taken to stay more centrally as the incision proceeds distally (over the PIP and distal interphalangeal joints) because the neurovascular bundles can become less radial and ulnar on the digit.
TECH FIG 4 • Percutaneous A1 release.
TECH FIG 5 • A Brunner-type incision. (Courtesy of Dominique Le Viet.)
Inspect the tendon distal to the A2 pulley, confirming that there is no catching under the A3 pulley8 and that an enlarged, bulbous flexor digitorum profundus is not catching under the distal end of the A2 pulley.10 In either of these cases, USSR may or may not relieve the problem.
Ulnar slip excision is then performed in either distal-toproximal fashion7 or with a proximal-to-distal technique.5
Distal-to-Proximal Ulnar Slip Excision
Just distal to the A2 pulley, incise the tendon sheath, creating a radially based flap. This flap may be repaired later with 6-0 Prolene if desired.
With the PIP joint maximally flexed, isolate and cut the ulnar slip of the flexor digitorum superficialis distally, taking care to preserve the vinculum brevis.
Pull the tendon into the proximal wound and cut it as far proximal as can be reached safely.
Confirm that the tendons now pass smoothly under the pulley system through a complete ROM.
Release the tourniquet. Irrigate the wounds.
Obtain hemostasis, usually with manual compression. Reinspect the wound, check for any arterial bleeding, and confirm the finger has brisk capillary refill.
Close the skin with interrupted sutures and place a mildly compressive dressing.
TECH FIG 6 • Open A-1 pulley release with FDS ulnar slip excision. A. Enlargement of tendon proximal to A-2 pulley (after A-1 release). B. Separating the FDS tendon slips. C. Use of a wire loop to separate tendon adhesions after cutting the FDS tendon proximally. (A,B: Modified from Le Viet D, Tsionos I, Boulouednine M, Hannouche D. Trigger finger treatment by ulnar superficialis slip resection [U.S.S.R.]. J Hand Surg 2004:29B:368–373.)
Proximal to Distal Ulnar Slip Excision
Examine the part of the tendon meant to glide under the A1 and A2 pulleys for enlargement, degeneration, longitudinal splitting, or loss of its smooth surface (TECH FIG 6A).
Fully flex the finger, identify the ulnar and radial slips of the FDS distally, and split them longitudinally in a proximal direction (TECH FIG 6B).
With the finger and wrist flexed, cut the ulnar slip of the FDS as far proximal as possible. Pull the ulnar slip distally, carefully separating it through the chiasm, and, with the PIP joint flexed, cut it distally at the edge of the A3 pulley. The tendon slip is than removed from either direction; a loop of 3-0 wire can be used to separate adhesions if necessary (TECH FIG 6C).
Release the tourniquet. Irrigate the wound.
Obtain hemostasis, usually with manual compression. Reinspect the wound, check for any arterial bleeding, and confirm the finger has brisk capillary refill.
Close the skin with interrupted sutures and place a mildly compressive dressing.
POSTOPERATIVE CARE
A soft dressing is applied with all of the digits free (FIG 4). Active ROM as tolerated is encouraged. Minimize dressing bulk to avoid inhibiting motion.
Formal therapy is required only if the patient has difficulty regaining ROM.
Patients whose digits were locked preoperatively are more likely to need therapy. This may be started within the first week.
Scar massage is encouraged after the wound is sealed.
OUTCOMES
Surgical release of trigger digits has a high success rate with a low complication and recurrence rate.3,12
COMPLICATIONS
Injury to digital nerve or artery
Bowstringing
Wound infection or dehiscence resulting in a flexor sheath infection
Postoperative stiffness
Incomplete release
Recurrence
Incisional tenderness
FIG 4 • A soft dressing is applied with all the digits free.
REFERENCES
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3. Gilberts EC, Wereldsma JC. Long-term results of percutaneous and open surgery for trigger fingers and thumbs. Int Surg 2002;87:48–52.
4. Griggs SM, Weiss AC, Lane LB, et al. Treatment of trigger finger in patients with diabetes mellitus. J Hand Surg Am 1995;20:787–789.
5. Le Viet D, Tsionos I, Boulouednine M, et al. Trigger finger treatment by ulnar superficialis slip resection (U.S.S.R.). J Hand Surg Br 2004;29:368–373.
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