As with all injuries, the history is very important for the surgeon in injuries of the hand. The type of injury and the mechanism of injury are decisive for planning surgical treatment.
One type of injury is saw injuries. They are often accompanied by bone and joint defects. In these cases, the surgeon must expect difficult treatment, possibly with bone or tissue grafts. How important the history is can also be illustrated by the example of a human bite injury. In a wound in the area of the metacarpophalangeal joint of the fingers sustained during a fight, a human bite in the sense of a fight bite (“clenched fist injury”) must always be suspected. This is a typical punch injury against the opponent’s incisors during a brawl. Because of the associated risk of joint infection, antibiotic therapy is indicated in such cases.
Diagnosis
The diagnosis is based on the following examinations:
- Inspection: location of the wound and malposition of the finger
- Testing of motor function
- Diagnostic exploration: because of the anatomical conditions, extensor tendon lesions, especially partial lesions, cannot be verified as clearly as flexor tendon injuries. In cases of doubt, exploration is therefore recommended to decide on further management.
Among the types of injury, open extensor tendon injuries predominate compared with traumatic ruptures, which are rare and usually accompanied by a bony avulsion.
Traumatic ruptures at the distal and middle joints are rather rare and must be distinguished from degenerative ruptures, as in rheumatoid arthritis or tendon degeneration (mallet finger). There should be clear signs of injury such as haematomas, swelling and/or an abrasion. In some circumstances, the cause of the injury can also have insurance-law consequences.
Anatomy of the extensor tendons
The so-called
extrinsic extensor tendons originate in the forearm and run to the hand.
They are the tendons of nine muscles:
- Abductor pollicis longus muscle (APL): long abductor of the thumb
- Extensor pollicis brevis muscle (EPB): short extensor of the thumb
- Extensor pollicis longus muscle (EPL): long extensor of the thumb
- Extensor carpi radialis longus muscle (ECRL): long radial wrist extensor
- Extensor carpi radialis brevis muscle (ECRB): short radial wrist extensor
- Extensor digitorum muscle 2–4 (ED): finger extensor 2 to 4
- Extensor indicis proprius muscle (EIP): index finger extensor
- Extensor digiti minimi muscle (EDM): little finger extensor
- Extensor carpi ulnaris muscle (ECU): ulnar wrist extensor
The tendons of the extensor muscles run in osteofibrous canals formed by 6 septa, which are called extensor compartments. These
6 extensor compartments and the extensor retinaculum, which encircles the wrist and carpus dorsally like a bracelet, prevent the tendons from slipping sideways and lifting off dorsally (bowstring effect).
1st extensor compartment: the tendons of the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) form the palmar border of the anatomical snuffbox. CAUTION: this compartment is closely related to the branch of the radial nerve!
2nd extensor compartment: the tendons of the extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB) are crossed at the edge of the radius by the tendon of the extensor pollicis longus (EPL).
3rd extensor compartment is formed by the tendon of the extensor pollicis longus (EPL). It runs in an arc around the dorsal tubercle of the radius (Lister’s tubercle) and forms the dorsal border of the anatomical snuffbox.
4th extensor compartment contains the tendons of the extensor indicis proprius (EIP) and extensor digitorum 2–4 (ED) and lies between the radial tubercle and the head of the ulna.
5th extensor compartment is formed by the tendon of the extensor digiti minimi (EDM) and lies radial to the ulnar head. This tendon is usually doubled.
6th extensor compartment contains the tendon of the extensor carpi ulnaris (ECU) and lies over the ulnar head. The ulnar wrist extensor tightens during ulnar deviation against resistance and is then easily palpable distal to the ulnar head.
The
intrinsic extensor tendon system is formed by the intrinsic muscles of the fingers: the interossei and lumbrical muscles. Together with the continuation of the extrinsic tendons, they form the complex extensor apparatus of the finger.
Sources and further information
