The flexor tendons of the hand are held in place by a series of connective tissue structures called pulleys.
The pulley system comprises 5 sets of of annular or A pulleys.
These are supported by 3 sets of cribriform/cruciate or C pulleys which are at the level of the joints.
There is a further larger more proximal palmar aponeurotic (PA) pulley proximal to the A1 pulley
The annular pulleys are considered more important.
The A1 pulley lies at the level of the metacarpal phalangeal joint just distal to the C1 pulley.
Other A pulleys are between the joints
A2 and A4 are the most important to prevent tendon bowstringing. A3 has some role, A1 and A5 none
Pulley injuries are most commonly described in rock climbers.
A2 and A4 are involved
The crimp grip in particular is used by climbers to secure a hold on the underlying rock and this places great stress on the flexor tendon and pulley system.
Baseball pitching usually affects A4
The A2 pulley is the largest of the pulley and lies at the level of the proximal phalanx.
It holds the flexor tendon in close apposition to the proximal phalanx.
It is a thin connective structure that is difficult to identify on imaging, direct visualisation is best with ultrasound.
The function of the pulley is more commonly assessed by noting the distance between the flexor tendon and the underlying bone particularly when the finger is flexed against resistance.
With a functioning pulley, the flexor tendon should lie no more than a millimetre from the underlying bone.
The extent of injury to the pulley system can be assessed during flexion stress on the flexor tendon by identifying the distance between the tendon and the metacarpal.
If the tendon is displaced but less than 3mm than a tear of the A2 pulley is diagnosed.
If the distance between the bone and the tendon is more than 4mm then a combined tear of the A2, 3 and 4 pulleys is assumed.
Injury grade
• 1 Sprai
• 2 Complete A4 or partial A2 or A3
• 3 Complete A2 A3
• 4 Complete A2 A3 A4 or A2 A3 plus muscle or ligament injury
Injuries to the cribriform or C pulleys are rare.
The commonest pathology of the A1 pulley is a fibroma
This likely occurrs as a result of overuse.
The flexor system is convex in orientation at the level of the A1 pulley
Thickening of the A1 pulley can develop as a result of chronic flexion and extension of the finger or thumb.
Alternatively, a fibrous nodules can develop in the superficial flexor tendon itself
Whether 1 or both of these processes occur, movement of the flexor tendon within the fibro-osseous tunnel is constrained
In the early stages, the patient complains of pain on finger flexion.
Ultrasound examination at this stage may demonstrate the nodule or ..
Dynamic assessment may show abnormal elevation of the pulley which normally remains in the same position as the tendon moves beneath it
As the condition deteriorates, the patient complains of a more significant clicking sensation as the tendon nodule passes beneath the pulley.
In time, the thickened is unable to return to its extended position without assistance
The patient finds that they need to push the finger back into full extension.
The condition is called trigger finger. Ultrasound is the most useful technique as it allows both diagnosis and treatment of the condition.
Treatment can involve corticosteroid injection into the tendon sheath alone or ..
be givenin conjunction with dry needling of the tendon nodule and/or percutaneous release of the pulley itself
Percutaneous release is carried out under ultrasound guidance Following local anaesthetic infiltration, a 19 gauge needle is inserted in the sagittal plane at the midpoint of the pulley as close to parallel to the pulley as can be achieved
If necessary, a small bend or bends can be introduced to the needle to align it better
Multiple passes are carried out through the pulley until the pulley is ruptured and the finger released
