Page created on October 26, 2021. Not updated since.

Summary

• Tendon injuries are usually traumatic. They’re classified into injuries of the flexor and extensor tendons, and into five and eight zones, respectively. There is loss of active flexion or extension of the affected finger. Treatment is usually surgical repair.
• Jersey finger is an injury of flexor tendons in zone I which leaves the affected finger lying is slight extension at rest. Treatment is surgical repair.
• Mallet finger is an injury of extensor tendons where the finger rests in 45° of flexion. Treatment is splint fixation or internal fixation
• Boutonniere deformity is an injury where the finger is in PIP flexion and DIP extension. Treatment is splint fixation or surgical repair.

Tendon injuries of the hand

Definition and epidemiology

Tendon injuries are traumatic injuries but are relatively rare. There may be concomitant neurovascular injury.

We can distinguish injury of flexor tendons and extensor tendons. Flexor tendon injuries are those which affect the tendons of the flexors of the hand:

• Flexor digitorum superficialis (FDS)
• Flexor digitorum profundus (FDP)
• Flexor pollicis longus (FPL)
• Flexor carpi radialis (FCR)
• Flexor carpi ulnaris (FCU)

A jersey finger is a characteristic injury of flexor tendons in zone I. It’s caused by avulsion of the FDP from its insertion at the base of the distal phalanx, usually of the ring finger.

Extensor tendon injuries are those which affect the tendons of the extensors of the hand:

• Extensor digitorum
• Extensor digiti minimi
• Extensor carpi ulnaris
• Extensor pollicis longus
• Extensor pollicis brevis
• Extensor indicis

Mallet finger and boutonniere deformity are characteristic injuries of extensor tendons. Mallet finger is caused by disruption of the extensor tendon distal to the DIP joint. Boutonniere deformity is caused by rupture of the extensor tendon over the PIP joint.

Etiology

Tendon injuries may occur due to cutting, pulling, or stretching forces.

Classification

We can classify flexor tendon injuries according into five “zones”:

Zone	Description
Zone I	Fingertips, area from distal to FDS insertion
Zone II	Fingers, area from FDS insertion to palm
Zone III	Palm area
Zone IV	Carpal tunnel area
Zone V	Area from carpal tunnel to forearm

Zone III injury has a high risk of neurovascular injury and a poor prognosis.

Extensor tendon injuries are classified into eight similar zones.

Clinical features

The patient experiences loss of active flexion or extension of the involved digits, and there may be local swelling and pain. In case of jersey finger, the finger lies in slight extension compared to the other fingers in rest.

In case of mallet finger the finger rests at 45° of flexion. In case of boutonniere deformity the finger is in PIP flexion and DIP extension.

Diagnosis and evaluation

Diagnosis is clinical and based on the function of flexion and extension for each joint in the hand, the resting position, as well as any concomitant skin injuries.

Treatment

Initial wound care is important. Most tendon injuries require surgical repair or reconstruction, except partial lacerations which may be treated conservatively. Implants or grafts may be used for reconstruction. Physiotherapy and controlled rehabilitation (Kleinert protocol) is important to regain as much function as possible.

Mallet finger requires either splint fixation with the DIP in hyperextension or internal fixation. Boutonniere deformity requires splint fixation with the PIP in hyperextension or suturing.