Trigger Finger

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Introduction

Each digit of the hand has the ability to move freely throughout a full ROM into flexion and extension.

Courtesy of www.netterimages.com

The efficiency, fluidity, and forcefulness of such movement are made possible by several "pulleys" along each digit of the hand. These pulley systems are comprised of a series of retinacular-type structures that are either annular or cruciform in nature. There are five annular pulleys (A1-A5) and three cruciform pulleys (C1-C3).

Trigger finger is thought to be caused by inflammation and subsequent narrowing of the A1 pulley of the affected digit, typically the third or fourth. A difference in size between the flexor tendon sheath and the flexor tendons may lead to abnormalities of the gliding mechanism by causing actual abrasion between the two surfaces, resulting in the development of progressive inflammation between the tendons and the sheath.

Commonly, trigger finger is referred to as "stenosing tenosynovitis." However, there have been histologic studies showing that the inflammation occurs more so in the tendon sheaths rather than the tendosynovium, making this name a false depiction of the actual pathophysiology of the condition.

Epidemiology/Etiology

Trigger finger can occur in anyone, but, statistically, women in their fifth to sixth decade of life are more likely to develop the condition than men and nearly six times more frequently. The chance of developing trigger finger is 2-3%, but in the diabetic population, it rises to 10%. The reason is not of glycemic nature, but rather is the actual cause of the duration and progression of the disease. Trigger finger can concomitantly occur in patients with:

• Carpal Tunnel Syndrome
• DeQuervain's disease
• Hypothyroidism
• Rheumatoid arthritis
• Renal disease
• Amyloidosis
  

There have been many potential causes of trigger finger discussed throughout the literature. However, there is little to no evidence on the precise aetiology.

• Occupational-related causes of trigger finger have been proposed, but the research linking the two is very inconsistent.
• Authors suggest that trigger finger can manifest from any activity requiring prolonged forceful finger flexion (i.e. carrying shopping bags or a briefcase, prolonged writing, rock climbing, or the strenuous grasping of small tools).
• It is important to consider that the cause of trigger finger is often times multi-factorial in nature.

Clinical Presentation

Trigger finger has a range of clinical presentations. Initially, patients may present with painless clicking with movement of the digit that can progress to painful catching or popping, typically at the MCP or PIP joints. Possible additional symptoms are stiffness and swelling (especially in the morning), loss of full flexion/extension, palpable painful nodule, and/or finger locked into a flexed position. Other signs and symptoms are slight thickening at the base of the digit and pain that may radiate to the palm or to the distal aspect of the digit.

Differential Diagnosis

The main characteristic of trigger finger is popping and/or catching with movement of the digit. However, this characteristic is not unique to just trigger finger. Other etiologies associated with a locking digit include:

• Dupuytren's contracture
• Focal dystonia
• Flexor tendon/sheath tumour
• Sesamoid bone anomalies
• Post-traumatic tendon entrapment on the metacarpal head
  

Complaints of pain at the MCP joint could be associated with any of the following:

• DeQuervain's (for trigger thumb only)
• Ulnar collateral ligament injury/Gamekeeper's thumb
• MCP joint sprain
• Extensor apparatus injury
• MCP joint osteoarthritis
  

Diagnosis of trigger finger can be confirmed with the injection of lidocaine into the flexor sheath, which should relieve pain and allow flexion/extension of the joint. Imaging is not typically indicated, but ultrasound and MRI may be used to help diagnose other aetiologies.

Read these documents on differential diagnosis:

• Trigger Digits: Principles, Management, and Complications
• Disorders of the Hand: A Case Study Approach

Outcome Measures

• Numeric Pain Rating Scale
• Grip Strength (Jamar dynameter)
• DASH Outcome Measure
• Stages of Stenosing Tenosynovitis (SST)
  • 1 = Normal
  • 2 = A painful palpable nodule
  • 3 = Triggering
  • 4 = The proximal interphalangeal (PIP) joint locks into flexion and is unlocked with active PIP joint extension
  • 5 = The PIP joint locks and is unlocked with passive PIP joint extension
  • 6 = The PIP joint remains locked in a flexed position
• Participant Perceived Improvement in Symptoms Rating Scale
  • 1 = Resolved
  • 2 = Improved, but not completely resolved
  • 3 = Not resolved
  • 4 = Resolved, but triggering at the distal interphalangeal/proximal interphalangeal joint(s)
  • 5 = Resolved at ten weeks versus six weeks
• Open & Close Hand 10 Times - Patient is to actively make ten fists. The number of triggering events in ten active full fists is then scored out of 10. If patient’s finger remains locked at any time, the test is completed and an automatic score of 10/10 is recorded.

Examination

History

• Recent trauma
• Job related repetitive movements
• Locking or snapping while flexing or extending the affected digit
• Radiating pain to the palm or digits

Past Medical History

• Diabetic individuals are 4x more likely to develop trigger finger 
• Disorders causing connective tissue changes such as RA and Gout

Observation

• A digit locked in flexion
• Bony proliferative changes in the subadjacent PIP joint

Palpation

• Painful nodule in the palmar MCP secondary to intratendinous swelling

Range of Movement

• Loss of motion, particularly in extension

Manual Muscle Testing

• Flexor Digitorum Profundus
• Flexor Digitorum Superficialis 
• Grip strength using the Jamar Dynameter

Note: If the finger is locked, testing may not be possible.

Joint Accessory Mobility

• PIP, MCP, DIP, and CMC of all affected digits
• Surrounding tissues 
• Wrist joint

Special Tests

• Open and Close hand 10x

Medical Management

The chronic nature of the symptoms associated with trigger finger makes conservative treatment difficult and often frustrating. Still conservative care (listed below in PT Management) is always recommended as a treatment plan prior to surgical intervention.

Corticosteroid use has shown to be effective in reducing pain and frequency of triggering.  The shot is injected into the affected tendon and reduces the inflammation and pressure on the tendon for better gliding through the flexor pulleys. Application by a primary care provider is an effective and safe alternative to surgical therapy.  Patient satisfaction, safety, and functional improvement are characteristics of steroidal injections in comparison to surgical treatment.  Surgery is associated with higher costs, longer absence from work, and the possibility of surgical complications.  Studies have also shown the combination of corticosteroid injections with lidocane to have significantly more effectiveness than lidocane alone. However, symptoms have shown to return longterm (4-6 mos) when treating with injections only.

Possible Side effects

• Flaring at injection site
• Local infections
• Tendon ruptures
• Allergic reactions
• Atrophy of subcutaneous fat tissue

Contraindications

• Under 18 years old
• Any prior treatment or surgery to the area within the last six months
• Possible traumatic or neoplastic origin of symptoms

Open Surgical Technique

This technique, considered to be the gold standard, is performed by making a longitudinal incision in the palmar crease over the metacarpophalangeal joint of the involved digit and followed by release of the flexor digitorum superficialis and profundus tendons.  This procedure lasts 2-7 minutes and has a longer average time of discomfort (45 days) post-op. An advantage to this technique is it allows the pulley to be visualized and therefore has less risk of damage to the digital nerves compared to endoscopic techniques.

Endoscopic Surgical Technique

This technique is performed by making two incisions: one at the palmar crease over the metacarpophalangeal and the other at the volar crease of the finger.  An endoscope is then introduced to cut the pulley releasing the flexor tendons.  This procedure lasts 2-9 minutes and has a shorter average time of discomfort (23 days) post-op.  Other advantages are absence of scars and scar related problems and shorter post-op rehabilitation.  However, there is a large learning curve and the instruments are costly.

Percutaneous Release

This technique can be performed with or without imaging.  Non-image-guided (blind) percutaneous release is performed by using anatomical landmarks to avoid injury to the tendons and neurovascular structures.  The recovery time is shorter than an open surgery but chance for damage to digital nerves is higher, especially to digits 1, 2, and 5.  A new technique using ultrasound-guidance helps clearly identify the tendons and neurovascular structures, preventing potential complications that are present with non-image-guided percutaneous release and it also compares favourably with surgical techniques.

Physical Therapy Management

As with all disorders of the upper extremity, proximal segments must be screened.  Also, because posture can contribute to distal problems, it should be addressed to provide the patient with optimal outcomes.

Patient Education

Since trigger finger is observed as an overuse injury, education is very important. Education should be given on:

• Rest
• Modifications of activities
• Specialized tools
• Splinting
• Modalities
• Posture

Splinting

A first step in treatment is to stop doing activities that aggravate the condition.  Splinting is one of the best ways to limit motion. Most authors agree that the intent of splinting is to alter the biomechanics of the flexor tendons while encouraging maximal differential tendon glide.  However, authors disagree on which joints to include in the splint and the degree of joint positioning.  There are various ways to splint a patient but, ultimately, it will depend on what provides the patient with the most relief. Splints are usually worn for 6-10 weeks. It should be noted that splinting yields lower success rates in patients with severe triggering or longstanding duration of symptoms.

Two major types of splinting most recently studied:

1. Splinting at the DIP joint.  This showed to have resolution in 50% of the patient’s symptoms.
2. Splinting at the MCP joint with 15 degrees of flexion.  This showed to have resolution of the patient’s symptoms at both 65% and 92.9%, which is consistent with the current literature.

               

Other Options

Modalities such as heat/ice, ultrasound, electric stimulation, massage, stretching, and joint motion (active and passive) can have some positive effects on trigger finger. It is thought that heat can help by providing increased blood flow and extensibility to the tendon. Following heat with stretching can provide more extensibility with plastic deformation. Joint movement and mobilisations increase joint and soft tissue mobility via a slow, passive therapeutic traction and translational gliding.

Although the evidence is lacking some documented cases and studies of improvement with various combinations of these techniques exist:

• 74 patients were treated with ten sessions of wax therapy, ultrasound, stretching muscle exercises and massage yielding 68.8% resolution of symptoms and symptom-free 6 months out.
• 60 trigger thumbs in 48 children were treated daily with passive exercise of their affected thumb by their mother resulting in a cure rate of 80% for stage 2 and 25% for stage 3 thumbs after an average of 62 months.
• Case Study: Both ART (Active release technique) and Graston techniques, followed by ice and mobilisations of the thenar eminence and 1st digit yielded no pain and only slight irritation at the joint capsule with mild weakness after 8 treatments.  The patients were given theraputty and released with exercises (flexion, extension, abduction, adduction) to continue STR.  At 14 months the patient reported complete resolution and pre-injury strength.

Extracorporeal Shockwave Therapy

Recently, extracorporeal shock wave therapy (ESWT) has been advanced as a possible alternative to surgery for the treatment of musculoskeletal disorders in patients recalcitrant to traditional conservative treatment. In a prospective randomized controlled clinical trial with a follow-up of 1, 3 and 6 months,to determine the efficacy of ESWT in the treatment of trigger finger and to compare the efficacy of ESWT and a corticosteroid injection in the treatment of trigger finger, the following findings were displayed. The findings show that three sessions of ESWT treat-ment could be as effective as a corticosteroid injection for improving symptom severity and functional status in patients with a classification of grade 2 according to the Quinnell classification. By setting 1000 shocks at an energy fluxdensity of 2.1 bar by considering previous studies using EWST in tendinopathies. We achieved high curerates in the ESWT group using this setting. It is also believed that ESWT induces the repair of the inflamed tissues by tissue regeneration and stimulates nitric oxide synthase, leading to suppression of ongoing inflammation in the soft tissues. There is also mild evidence that one of these mechanisms may also have a beneficial effect on the thickening of the flexor tendon and its sheath, resulting in overcoming the obstruction in the trigger finger. ESWT offers an alternative for people who reject corticosteroid injections because of their potential complications, or who are allergic to local anesthetics as well as in patients with an intense fear of injections ('needle phobia').