Trigger finger and trigger thumb consist in the altered movement causing an involuntary catching when flexing the finger towards the palm. In severe cases the fingers are locked in a flexed position and cannot be straightened.
Trigger finger is a pathology of the flexor tendon, which connects the phalanges to the muscles in the palmar side of the forearm. The tendon is aligned with the finger and fixed by lateral ligaments named pulleys. The tenosynovium sheath encloses the tendon to facilitate its gliding when the finger is extended or flexed.
In trigger finger the irritated flexor tendon and pulleys become swollen occasionally leading to the formation of a nodule, which limits or blocks the sliding of the tendon during movement. A typical catching and popping noise can be heard during grasping function.
There are various classification systems for a shoulder impingement syndrome.
Stages of subacromial impingement in athletes - Jobe’s Classification
Pure impingement with no instability
Primary instability, with capsular and labral injury with secondary impingement, which can be internal or subacromial impingement
Primary instability due to intrinsic ligament laxity with secondary impingement
Pure instability with no impingement.
Grading of impingement changes - Milgrom’s Ultrasound Classification:
Stage 1 Bursal thickness from 1.5 to 2.0 mm
Stage 2 Bursal thickness over 2.0 mm
Stage 3 Partial or full thickness tear of the rotator cuff.
Impingement lesions - Copeland Levy Classification:
This is based on the location of the impingement, either on the acromial or the bursal side.
A0 normal - smooth surface
A1 minor deterioration, haemorrhage or local inflammation
A2 marked scuffing/damage of the undersurface of the acromion and coraco-acromial ligament
A3 exposed bone areas.
B0 normal - smooth surface
B1 minor deterioration, haemorrhage, inflammation
B2 major deterioration of the cuff, partial thickness tear
B3 full thickness tear of the rotator cuff
B4 massive cuff tear.
According to the Habermeyer Classification the fractures to the proximal humerus are divided into:
Type 0 one fractured part without dislocation
Type A two-part fracture of the great tuberosity and lesser tuberosity avulsion
Type B involves the humerus “surgical” neck below the femoral head as two-part, three-part and four-part with one or both tuberosities
Type C involves the humerus anatomical neck (between the head and greater tuberosity) as two-part, three-part and four-part with one or both the greater and lesser tuberosities.
These are defined further as:
One-part fractures are non-displaced fractures or fractures with minimal displacement
Two-part fractures only involve a single segment
Three-part fractures involve two segments
Four-part fractures occur when all humeral segments are involved (see image in pathology section)
The injury severity is proportional to the increasing number of fractures.
The irritation of the flexor tendon causing trigger finger is mostly a consequence of overuse of the hand; however the aetiology of this pathology remains unknown. The condition is more frequent in women and the adult/aged population. Apart from repetitive grasping/gripping function other causes leading to trigger finger include:
Tear to the flexor tendon
Infection of the synovium
Congenital condition predisposing to tendon nodule formation
Although risk factors leading to trigger finger have not been identified, the following factors may pose a risk:
Age between 40 and 60 years
Occupational activities: repetitive gripping of power tools
Prolonged driving (grasping the steering wheel)
Daily activities: writing, carrying bags and briefcases
Medical conditions: diabetes increases four times the risk, rheumatoid arthritis
The symptoms arising from a trigger finger are:
Pain at the nodule site when flexing and extending the finger
Clicking sensation when flexing the finger
Impaired finger extension
Movement restrictions (grasping) especially after inactivity
Blockage of the finger in a bent position
The diagnosis of trigger finger does not require special tests or X-rays. Medical examination is based on:
Observation of the hand anatomy
Palpation to detect the presence of nodules at metacarpo-phalangeal or proximal-phalangeal joints
Assessing changes in finger flexion/extension, stiffness, pain level when opening/closing the fist 10 times
Audible clicking/popping noises
Conservative treatment is the most common and efficacious management of trigger finger. if the condition has not been protracted over four months, physiotherapy and occupational therapy will restore successfully finger function. Conservative management also include:
Immobilisation of the fingers with a splint until the inflammatory condition has subsided
Administration of NSAIDs
Local steroid injection
Surgery is required in case of severe and prolonged trigger finger symptoms. It consists in the resection of the pulleys at the nodule zone to free the tendon during movement. This an outpatient procedure performed under local anaesthesia. Methods such as endoscopic surgery and percutaneous tendon release are available providing a faster postoperative healing.
Complications following a surgical treatment of trigger finger are:
Limited straightening of the finger (insufficient tendon release)
Hyperextension of the finger (excessive tendon release)
Ongoing trigger finger
A physical or occupational therapist will guide stretching movements to restore flexibility and physical exercises to strengthen the fingers and re-acquire fine motor control. Physiotherapy is recommended for 6 weeks. Full recovery after surgery can take up to 6 months. Advice on modifying daily activities is provided to avoid excessive stress on the affected tendon.
There are no specific measures to prevent trigger finger. The best strategy is to avoid excessive strain of the flexor tendon during occupational and daily activities.