Triggering of the digits or thumb Constriction at the level of the metacarpal head

results from the disproportionate size of the flexor tendon in relation to its overlying retinacular pulley (i.e. the A1 pulley) which can undergo marked hypertrophy (Bunnell, 1944) (Fig. 8.3).

ECU tendonitis EDM

EIP APL EPB Site of intersection syndrome ECRL ECRB

FPL

FCR tendonitis

Triggering at AI pulleys over metacarpal heads

Calcific tendonitis of FCU

FCU tendonitis

Thickened tendon

AI pulley Patient presentation

The incidence of trigger finger peaks in the sixth decade of life. The thumb is most commonly affected, followed by the ring, middle, little and index fingers (Weilby, 1970). Several digits can be affected at once. Multiple digit involvement is more common in insulin-dependent diabetics who sometimes present with a mild PIP joint flexion deformity of the middle finger. Non-diabetic patients with longstanding triggering may also present with a PIP joint flexion deformity which is sometimes mistaken for Dupuytren’s disease or joint dislocation.

The patient may complain of tenderness over the A1 pulley, pain on active flexion and/or ‘catching’

or ‘clicking’ of the PIP joint as the finger moves from extension to flexion or from flexion to full extension. The digit may actually ‘lock’ into flexion and require passive correction to restore digital extension. The thickened flexor sheath can generally be palpated.

Conservative management 1. Corticosteroid injection

Primary triggering of the digits can often be treated successfully with corticosteroid injection into the tendon sheath. Success of this treatment is greater in patients with involvement of only Figure 8.1. The more common tendon disorders on

the dorsum of the hand involve the 1st and 6th compartments, i.e. the tendons of abductor pollicis longus (APL)/extensor pollicis brevis (EPB) and extensor carpi ulnaris (ECU) respectively. Less common entrapment disorders involve the tendons of extensor indicis proprius (EIP) and extensor digiti minimi (EDM).

Figure 8.2. Common tendon disorders on the volar aspect of the hand include triggering of the thumb and/or digital flexor tendons and tendonitis of flexor carpi radialis (FCR) and flexor carpi ulnaris (FCU).

The FCU tendon can be the site for calcific deposits near the tendon’s junction with the pisiform. In rheumatoid disease, flexor pollicis longus (FPL) can undergo attrition rupture due to bony spicules on the scaphoid.

Figure 8.3. The disproportionate size of the flexor tendon in relation to its overlying retinacular pulley can result in pain on active flexion and cause the finger to ‘trigger’ or, in severe cases, lock into the flexed position.

Conditions of the wrist and finger tendons 101

one digit and where duration of symptoms is less than four months (Newport et al., 1990). If symptoms persist, the injection can be repeated on two more occasions without the risk of possible complications such as skin depigmenta-tion, skin atrophy or tendon rupture (Marks and Gunther, 1989).

2. Splinting

Patients who do not wish to undergo injection or surgical release can be managed with a hand-based splint which immobilizes the MCP joint(s) of the affected digit(s) in neutral extension. This treatment protocol was devised by Evans et al. (1988) and its aim is to rest the proximal pulley system by altering the biomechanics of the flexor tendons (Fig. 8.4).

The outcomes of splinting have been compared with those of injection at follow-up after one year and results have been encouraging. Sixty-six per cent of splinted digits were symptom-free compared to 84 per cent in the case of injected digits (Patel and Bassini, 1992).

The patient is asked to wear the splint during waking hours for an initial period of 3 weeks. The splint prevents flexion at the MCP joint(s) of affected digit(s), however is ‘stepped down’ to allow MCP flexion of uninvolved digits. Every 2 hours during the day, the patient actively flexes

the fingers into a ‘hook fist’ and then actively extends the digits to full range. This exercise maintains the differential glide of the flexor tendons within the sheath and is repeated 20 times at each session (Fig. 8.5).

At the completion of this set of exercises, ‘place and hold’ flexion exercises are performed in the full-fist position, i.e. the fingers are passively placed into full flexion at all three digital joints and the patient is then asked to gently maintain this fully flexed position for several seconds. This manoeuvre maintains mobility of the MCP joints and avoids the ‘triggering’ that can occur with active digital flexion from the fully extended position.

If the patient has shown some improvement during the 3-week period, a further 3 weeks of treatment can be trialled. If there has been no improvement during this time, steroid injection or pulley release are indicated.

Surgery

The pulley is generally divided through an open procedure; however, percutaneous trigger finger release is an alternative procedure (Stothard and Kumar, 1994). The percutaneous method is contra-indicated in patients with rheumatoid disease, diabetes or those with excessive subcutaneous tissue (Froimson, 1993) (Fig. 8.6).

Early active movement is begun within a day of surgery and scar management is commenced upon removal of sutures.

Figure 8.4. Conservative management of trigger finger(s) involves a hand-based splint that immobilizes the MCP joint(s) of the affected digit(s) in neutral extension.

Figure 8.5. On a 2-hourly basis, the patient fully flexes and extends the digits 20 times. The purpose of this exercise is to maintain the differential glide of the flexor tendons.

Branches of superficial

radial nerve EPL

1st Dorsal compartment

housing APL and EPB tendons

Open release of the AI pulley