Finger pulley injuries can occur at any one of the five flexor tendon pulleys of the fingers, but most commonly affects the A2 pulley.
These are overwhelmingly the result of a discrete trauma occurring with the hand in a finger grip position. They are most frequently seen in competitive climbing athletes, up to a quarter of whom report finger pulley injuries.
The annular pulleys are the most functionally important and commonly injured. They comprise a transversely oriented sheath of fibrous tissue that wraps over the flexor superficials and profunda tendons.
There are five flexor tendon pulleys in the fingers that are named A1-A5. The thumb only has two pulleys that are described as A1 and A2.
- A1, A3 and A5 pulleys
- overlie the palmar aspect of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints respectively
- attach to the volar plate
- rarely torn
- A2 and A4
- attach to periosteum
- A2 is most load bearing and most frequently torn 2
- A4 is the most flexible
- A4 rupture often seen with A3 rupture
Have no role in the diagnosis but may be requested in the acute setting of a finger injury. May shows soft tissue swelling.
Allows for dynamic testing with flexion stress on the affected digit. It is reported to be up to 100% accurate in identifying pulley injuries 3,4. Normal pulleys are seen as thin fibrillar, hyperechoic bands anteriorly while their lateral portion is usually obscured by anisotropy.
- hematoma or discontinuity in the pulley band
- bowstringing of the flexor digitorum tendons
- displacement of the flexor digitorum profundus from the phalangeal/metacarpal cortex
pulley sprain or partial rupture
- pulley thickening
- hypoechoic change
Also highly accurate for finger pulley injuries. MRI is better at demonstrating the lateral pulley attachments, best seen on axial slices. The hand can be scanned in a normal and stressed position.
The pulleys are normally seen as bands of hypoechoic tissue and are best appreciated on T1 imaging without fat sat. Fluid sensitive imaging helps demonstrate associated focal edema at the site of injury.
Treatment and prognosis
All A2 and a large proportion of A4 pulley ruptures require surgical repair. A1, A3 and A5 pulleys may be managed conservatively initially.
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