Trigger Finger (Stenosing tenosynovitis) is an inflammatory condition that narrowing the retinacular sheath of the tendon, and therefor leads to an entrapment of the tendon at A1 pulley.
- More common in women older than age 50.
- Most common in ring and middle fingers.
- The incidence of trigger digits is 2.2% in nondiabetic adults older than 30 years and up to 10% in patients with insulin dependent diabetes mellitus.
- Commonly associated with diabetes and inflammatory arthropathy.
- May result from repetitive grasping activities.
- The phenomenon of trigger finger is due to mechanical impingement of the digital flexor tendons as they pass through a narrowed retinacular pulley (A1 Pulley) at the level of the metacarpal head.
- The most remarkable pathologic changes are seen in the pulley itself, which demonstrates gross hypertrophy, described as a “whitish, cicatricial collar-like thickening.”
- A1 pulley and the corresponding surface of the flexor tendon undergo fibrocartilaginous metaplasia under the influence of repetitive, compressive loads.
- Microscopic examination of A1 pulley demonstrates the following changes:
- Cyst formation,
- Fiber splitting
- Lymphocytic or plasma cell infiltration.
- Presence of chondrocytes
- Presence of type III collagen
- Every digit (except the thumb) has:
- 5 annular pulleys (A1 to A5).
- 3 cruciate pulleys (C1 to C3).
- The Thumb has:
- 2 annular pulley.
- Oblique pulley .
- A1 Pulley is where trigger finger occurs.
- A2 and A4 are the most important pulleys to prevent flexor tendon bow-stringing.
See Also: Extensor compartments of the wrist
Classification of Trigger Finger
The Classification of Trigger Finger was proposed by Quinnell and modified by David Green in 1997.
|Grade I (pre-triggering)||Pain.|
History of catching, but not demonstrable on physical examination; tenderness over the A1 pulley.
|Grade II (active)||Demonstrable catching, but the patient can actively extend the digit.|
|Grade III (passive)||Grade IIIA: Demonstrable catching requiring passive extension.|
Grade IIIB: inability to actively flex.
|Grade IV (contracture)||Demonstrable catching with a fixed flexion contracture of the PIP joint.|
See Also: Classification of Nerve Injuries
- Pain / tenderness in the distal palm.
- Progresses to mechanical catching/locking.
- The finger may become in fixed flexion.
- Patients often complain of referred pain at the dorsal MCP/PIP area.
Treatment of Trigger Finger
Indicated as a first line of Trigger Finger treatment and includes:
- Activity modification
- Steroid injections:
Steroid injection is curative in about 60% of patients with trigger finger.
Diabetic patients generally less responsive to steroid injection.
Rarely, tendon ruptures have been reported after corticosteroid injection, so intratendinous injection should be avoided given the known attritional effects of corticosteroids on collagen.
See Also: Flexor Tendon Injury of the Hand
- Indicated after failure of nonoperative management.
- Surgical release of A1 pulley (open or percutaneous) with resection of ulnar FDS slip when necessary.
Congenital Trigger Thumb
Congenital Trigger Thumb is the most common cause of abnormal thumb posturing in flexion or extension.
- The condition has a bilateral incidence of 25% to 33%
- Pathologic specimens document more frequent thickening and synovial proliferative changes in the tendon itself rather than in the annular sheath.
- Notta node is a pathologic nodular thickening in the tendon.
- It can be palpated just proximal to the proximal border of the A1 pulley, confirming the diagnosis.
- Congenital Trigger Thumb may initially be observed.
- In case of observation failure, annular pulley release may be required between ages of 2 and 4 to prevent IP joint contracture.
Trigger Finger in Childhood
- It’s usually caused by anatomic anomaly.
- Children with storage diseases, such as Hurler syndrome, can acquire trigger finger and carpal tunnel syndrome as a result of abnormal collections of mucopolysaccharide within and around the flexor tendons.
- A1 pulley release may not resolve triggering; additional A3 release or resection of ulnar FDS slip may be required.