Ultrasound-Guided Trigger Finger Release at the First Annular (A1) Pulley
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Compared to open surgery, releasing the A1 pulley under ultrasound guidance has a better safety profile with a lower risk of complications and a quicker return to work.
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Percutaneous release is performed through a small puncture incision that does not require sutures.
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Ultrasound image guidance allows the physician to visualize the neurovascular bundle before making the incision as well as during the procedure, which diminishes the risk of neurovascular injury.
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Return to basic daily activities and resuming full duties at work is quicker since the wound heals more quickly. , ,
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This procedure should be avoided in patients that present with evidence of Dupuytren contracture.
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The Colberg criteria help confirm a complete release of the A1 pulley.
Anatomy
The flexor tendons in the finger lay palmar (volar) to the metacarpal bones with the flexor digitorum profundus (FDP) closer to the metacarpal bone and the flexor digitorum superficialis (FDS) farthest from the metacarpal bone. The FDP and FDS tendons are surrounded by a common synovial tendon sheath. There are five annular ligaments, referred to as “A pulleys,” which are superficial to the tendon sheath that hold the tendons close to the bone. The A1 pulley is the most proximal and clinically significant ligament. , The length of the A1 pulley can be estimated by measuring the distance between the palmar creases of the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints. The A1 pulley is found at the level of the metacarpal head and MCP joint, and this measurement is roughly equivalent to the distance between the proximal edge of the A1 pulley and the MCP crease ( Fig. 28.1 ). There is a neurovascular bundle at both the radial and ulnar side of the tendon. The digital arteries originate from the superficial palmar arch (artery), which is roughly 1 inch proximal to the MCP joint.
Common Pathology
Stenosing tenosynovitis of the finger flexor tendons, more commonly referred to as “trigger finger,” can lead to pain and loss of mechanical hand function. In the acute phase, inflammation of the tendon and the synovial lining of the tendon sheath causes severe pain with finger bending. The inflammation eventually can cause mechanical catching or locking of the tendon at the A1 pulley as the tendon gets so swollen that it does not glide well under the pulley with finger flexion and extension. The friction created from the catching leads to chronic thickening of the A1 pulley, which may lead to a permanently locked finger. The severity of the trigger finger is graded based on the Quinnell grading system :
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Grade 1—pain with flexion at the A1 pulley with no mechanical symptoms
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Grade 2—painful catching at the A1 pulley with active release with the same finger extension
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Grade 3—painful locking that requires passive release with the other hand
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Grade 4—permanently locked finger
Ultrasound Imaging Findings
Ultrasound is used to evaluate the A1 pulley, flexor tendons, and neurovascular structures, as well as to diagnose mechanical catching of the tendon ( Fig. 28.2 ). In the cross-sectional view, the A1 pulley is at the level of the metacarpal head superficial to the tendon sheath. The neurovascular structures are seen radial and ulnar (i.e., lateral and medial) to the tendons (see Fig. 28.2A ). The A1 pulley can be further evaluated in the longitudinal view for any evidence of tendinopathy such as hypoechoic thickening of the tendon and/or hyperemia in the tendon sheath or A1 pulley on power Doppler imaging. , Hypertrophy of the A1 pulley and a swollen nodule in the tendon with a mechanical catching at the A1 pulley (see Fig. 28.2C ) during dynamic ultrasound examination confirms the diagnosis of trigger finger.
Treatment Options
Patients are generally first treated with nonsteroidal antiinflammatory drugs (NSAIDs), finger night splints, cortisone injection, and/or physical therapy. Injecting the trigger finger using ultrasound guidance improves accuracy of the placement of the needle, avoiding neurovascular structures. , Cortisone injection and splinting have been shown to provide significant relief in 50% to 56% of patients. However, more than 30% of cases do not resolve, especially if the treatment did not start before the onset of mechanical symptoms. , These cases require a release of the A1 pulley by either open surgery, palpation guided, or ultrasound-guided release of the A1 pulley. , ,
Equipment
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Needles: 25-gauge, 1.5-inch needle/18-gauge, 1.5-inch needle with a blade at the tip (Nokor Admix, Becton, Dickinson and Company, Franklin Lakes, NJ) ( Fig. 28.3 ). Other instruments such as the hook knife have also been reported and shown to be effective.
Fig. 28.3
Nokor Admix 18-gauge, 1.5-inch hypodermic needle (A) with blade at the tip and ultrasound image of the needle (B).
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Musculoskeletal ultrasound machine with a high-frequency linear array transducer.
Technique
Patient Position
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Seated with the palmar side of the hand facing up and the hand resting at the edge of the table in order to allow hyperextension of the MCP joint. The palmar side is cleansed in a sterile fashion from mid-palm down to the distal interphalangeal joint, creating a sterile field ( Fig. 28.4A ).
Fig. 28.4
(A) Position of patient, clinician, transducer, needle, and ultrasound machine. (B) Flexor digitorum superficialis and profundus at the metacarpophalangeal joint. Oval : A1 pulley. Arrow : 25-gauge, 1.5-inch hypodermic needle distal to the A1 pulley inside the tendon sheath. The fluid was injected from distal to proximal inside the tendon sheath. It can be seen spreading through the superficial and deep aspect of the tendon sheath proximal to the A1 pulley.
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For patients with risk of vasovagal syncope, we recommend having them lay down supine with the hand facing up, resting at their side at the edge of the table.
Clinician Position
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Seated distal to the trigger finger.
Transducer Orientation
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Short axis to the metacarpal bone and flexor tendon to identify the neurovascular structures.
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Long axis to the flexor tendon over the A1 pulley and the MCP joint to perform the release.
Needle Orientation
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In-plane with the transducer with a distal to proximal approach toward the A1 pulley.
Target
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Inject local anesthesia with a 25-gauge, 1.5-inch needle from distal to proximal over the A1 pulley and inside the tendon sheath (see Fig. 28.4B )
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Create a puncture incision in the skin using the 18-gauge Nokor needle and advance towards the A1 pulley and flexor tendons.
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Make an incision through the A1 pulley and the tendon sheath from distal to proximal (see Fig. 28.4A ). Irrigate the tendon with normal saline solution to ensure a complete release.
Injectate Volume
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Local anesthesia: 1 to 3 mL of local anesthetic
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Author prefers 1% lidocaine with epinephrine (1:100,000)
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Irrigation: 3 mL normal saline solution
Pearls and Pitfalls
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Avoid puncturing the neurovascular structures and blood vessels by keeping the Nokor needle tip (blade) in the visual field at all times.
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Despite popular belief, epinephrine is safe to use near fingers, even for digital nerve blocks, and it greatly reduces the amount of bleeding that occurs with the procedure, minimizing complications.
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This procedure should be avoided in patients that have widespread hand pain, complex regional pain syndrome, or evidence of Dupuytren contracture.
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Complete release of the A1 pulley can be confirmed after the procedure using the Colberg criteria ( Fig. 28.5B–D ) :
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Irrigate the tendon and the area where the A1 pulley was released in order to visualize an anechoic defect between the two ends of the severed A1 pulley (see Fig. 28.5B and D ).
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Perform a dynamic ultrasound evaluation of the tendon by doing active and passive range of motion in order to visualize the tendon gliding smoothly without any mechanical catching/locking (see Fig. 28.5E and F ).
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Have the patient make a fist 10 times by doing full active range of motion of the hand/fingers, closing and opening all of the fingers to make sure there is no residual mechanical catching/locking of the tendon.
Fig. 28.5
Flexor digitorum superficialis and profundus at the metacarpophalangeal joint before and after A1 pulley release. ( Oval : A1 pulley). (A) Longitudinal view of tendons showing intact A1 pulley before release. truncated rectangle : 18-gauge Nokor needle. The needle was advanced from distal to proximal. (B) Longitudinal view of tendons post-release showing an empty space where the A1 pulley used to be. (C) Cross-sectional view of the tendons showing intact A1 pulley and neurovascular bundles (arrows) . (D) Cross-sectional view of the tendons showing a transected A1 pulley (empty space inside the rectangle between (the two ends of the A1 pulley after release). (E) Finger in full extension with the nodule away from the area of the A1 pulley. (F) Finger in full flexion with the nodule gliding smoothly through the area where the A1 pulley used to be not catching anymore.
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If a patient does not pass any of the three tests, residual A1 pulley fibers may be present and the incision should be extended proximal or distal according to where the residual catching is identified. The Colberg criteria should be performed again to ensure complete release of the A1 pulley.
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If done correctly, patients should not feel any residual catching/locking after the procedure and rate of recurrence is less than 1%.
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Avoid immobilizing after the procedure in order to minimize scar tissue formation around the tendon that may lead to flexion contracture.
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Preexisting PIP joint flexion contracture is a risk factor for residual pain at the PIP joint after releasing the trigger finger because the finger range of motion increases from eliminating the mechanical catching of the trigger finger. ,
Post-Procedure
Once the A1 pulley has been released, an adhesive bandage is placed over the puncture incision and it may be removed 24 hours post-procedure. Patients are instructed to avoid heavy lifting or gripping for 2 weeks. Patients can perform all basic activities of daily living and light duties as tolerated 24 hours post-procedure. If there is pain, patients can ice the treated area and take acetaminophen or an over-the-counter NSAID as needed. Patients may have mild residual soft tissue swelling after the release that will resolve within the first 4 weeks post-procedure.
Complications Post-Procedure
Possible complications after the procedure, although extremely rare, include residual pain, infection, flexor tendon laceration, neurovascular injury, and incomplete release of the A1 pulley. The thumb presents two additional challenges to the procedure: (1) the thumb digital nerve can cross over the A1 pulley and is at risk of laceration; and (2) the thumb frequently has a sesamoid bone within the adductor pollicis and abductor pollicis brevis tendons, which may displace the tendon and make it difficult to navigate the needle into the A1 pulley without lacerating the tendon. , These are similar to complications that may be seen with open surgery and palpation-guided percutaneous release. Open surgeries carry a risk rate of 12% to 28%, ranging from nerve injury, vascular injury, wound infection to wound dehiscence and scar hypertrophy. Ultrasound minimizes the risks associated with palpation-guided percutaneous release, especially the risk of an incomplete release, tendon laceration and neurovascular injury. PIP joint flexion contracture and diabetes are risk factors for residual pain at the PIP joint after releasing the trigger finger.
Ultrasound-Guided Release of De Quervain Tenosynovitis
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