Trigger Finger/Thumb
Trigger finger / thumb (referred to as stenosing tenosynovitis) is a common and painful condition. It is more common in females in the 4th to 6th decade of life, it can affect any digit but is more commonly seen in the middle finger, ring finger or thumb and can be bilateral in up to 30% of cases Trigger Thumb – StatPearls – NCBI Bookshelf
The flexor tendons made up of the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) or Flexor Pollicis longus (FPL) for the thumb are held in place by a set of pullies that fasten the tendons to the metacarpals and phalanges (bones of the hands and fingers). These pullies along with the tendons can be come thickened, the A1 pulley is most commonly affected site which is situated at the level of the Metacarpal phalangeal joint (MCP) which stops the tendon from gliding naturally through the finger.
The exact cause of trigger finger/thumb remains unknown but several predisposing factors have been identified. Overuse of the hands and repetitive gripping movements promotes diffuse tenosynovial growth. Patients with certain underlying metabolic and systemic diseases such as diabetes, hypothyroidism, gout and rheumatoid arthritis are also at an increased risk of developing the disease. Trigger Thumb – StatPearls – NCBI Bookshelf. The condition was initially thought to be due to a local inflammatory response of the pulley but is now thought to be more of a degenerative process resulting in fibrocartilage metaplasia of the flexor tendon sheath. Trigger Finger – StatPearls – NCBI Bookshelf
What are the signs and symptoms?
The condition is characterised by a painful click/snap along the palmar aspect of the base of the thumb or finger. The digit can become locked in a flexed/bent position, making it very difficult to straighten, and usually needs to be extended using the other hand. This typically results in a painful snap referred to as the trigger as the tendons are squeezed underneath the pulley.
How is it diagnosed?
The diagnosis of trigger finger/thumb can usually be made from your clinical history and examination findings. Imaging is not routinely required.
Patients usually present to the clinic with quite clear signs and symptoms of triggering that they are often able to reproduce. Imaging may be requested in atypical cases or where surgical workup is being considered. Ultrasound can be helpful given its dynamic capabilities to see any compression signs at the site of pulleys as well as help exclude any occult tendon sheath pathology. Ultrasound Features of Trigger Finger: Review of the Literature – PubMed. MRI can also be helpful but does not have the dynamic capabilities of ultrasound. X-rays are not typically helpful for this condition.
How are they treated?
Treatment options are divided into conservative and surgical.
Conservative options:
- Activity modification, ergonomic modifications, +/- analgesia/short course of NSAIDs. These simple interventions can be helpful initially, allowing things to calm down. A finger splint (metacarpophalangeal blocking splint) can also be used to immobilise the digit which can be very helpful. However, compliance can be difficult for some patients, and time frames for improvement remain unclear, ranging from 6-10 weeks or longer. Consistent splitting over this period is more effective than night time splinting only. Efficacy of Splinting in Managing Adult Trigger Finger: A Systematic Review of Short-Term Outcomes – PMC
- A local anaesthetic and steroid injection into the flexor tendon sheath under ultrasound guidance can be very helpful for patients and in certain individuals can be curative. Corticosteroid Injection for the Treatment of Trigger Finger: A Meta-Analysis of Randomised Control Trials – PubMed. Less favourable results are typically seen in patients with underlying metabolic disease.
Surgical options:
If conservative options mentioned previously do not provide adequate relief or if there is a reoccurrence in symptoms, then surgery is usually definitive.
- Surgical treatment consists of a release of the A1 pulley. This involves a 1 cm to 1.5 cm incision over the volar aspect of the MCP just proximal to the A1 pulley, where it is cut, making more space for the underlying tendons to glide over the finger/thumb. This has a reported success rate of 90-100%. Tendon Sheath Incision for Surgical Treatment of Trigger Finger – PubMed
- Other surgical options, such as endoscopic and ultrasound-guided percutaneous release, can also be offered. They have been shown to be as effective as ‘open’ surgery but with shorter post-procedure recovery times. Treatment of Trigger finger by ultrasound-guided needle release of a1 pulley: A series of 105 cases – PubMed
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