Plastic surgery Hand surgery Various blocks in hand surgery

A wrist block consists of anesthetizing the terminal branches of the ulnar, median, and radial nerves at the level of the wrist.

Ulnar nerve - anesthetized by inserting the needle under the tendon of the flexor carpi ulnaris muscle close to its distal attachment just above the styloid process of the ulna.

Median nerve - blocked by inserting the needle between the tendons of the flexor palmaris longus and flexor carpi radialis. 

Radial nerve - is essentially a "field block" and requires more extensive infiltration because of its less predictable anatomic location and division into multiple smaller cutaneous branches. Xylocaine injected subcutaneously just proximal to the radial styloid, aiming medially. Then the infiltration is extended laterally,

• Shown are flexor palmaris longus (white arrow) and flexor carpi radialis (red arrow) tendons.

Note that the musculocutaneous nerve is outside of the axillary plexus sheath.

The arrangement of the individual nerves and their relationship to the axillary artery is important in axillary blockade. The pulse of the axillary artery is palpated high in the axilla. Once the pulse is felt, the artery is fixed between the index and the middle fingers and firmly pressed against the humerus to prevent "rolling" of the axillary artery during block performance. 

• With the arm abducted at 90° and the axillary arterial pulsation as a point of reference, the nerves are located as follows:
• - Median nerve is positioned superficially and immediately above the pulse
• - Ulnar nerve is found superficial slightly deeper than the median nerve
• - Radial nerve is located behind the pulse.
• - Musculocutaneous nerve can be found 1 to 3 cm deeper and above the pulse, often outside the brachial plexus sheath as it moves distally away from the axillary fossa

• Ankle block as a block of two deep nerves (posterior tibial and deep peroneal) and three superficial nerves (saphenous, sural, and superficial peroneal).
• Deep nerves are anesthetized by injecting local anesthetic under the fascia, whereas three superficial nerves are anesthetized by a simple subcutaneous injection of local anesthetic.

Deep peroneal nerve - is located immediately lateral to the tendon of the extensor hallucis longus muscle (between the extensor hallucis longus and the extensor digitorum longus). The pulse of the anterior tibial artery (dorsalis pedis) can be felt at this location; the nerve is positioned immediately lateral to the artery.

Posterior tibial nerve is anesthetized by injecting local anesthetic just behind the medial malleolus. 

Saphenous nerve block is accomplished by injection of local anesthetic in a circular fashion (line) subcutaneously just above the medial malleolus. 

Superficial peroneal nerve block is performed by injecting local anesthetic in a circular fashion at the level of the lateral malleolus and extending from anterior to posterior.

Sural nerve block is accomplished by injecting local anesthetic in a fanwise fashion subcutaneously and below the fascia behind the lateral malleolus.

The hand is divided into five distinct flexor zones

• • Zone 1—from the insertion of the profundus tendon at the distal phalanx to just distal to the insertion of the sublimus (FDS)
• • Zone 2—Bunnell’s “no-man’s land”: the critical area of pulleys between the insertion of the sublimus and the distal palmar crease
• • Zone 3—“area of lumbrical origin”: from the beginning of the pulleys (A1) to the distal margin of the transverse carpal ligament
• • Zone 4—area covered by the transverse carpal ligament
• • Zone 5—area proximal to the transverse carpal ligament

The flexor digitorum profundus (FDP) inserts onto the distal phalanx. The flexor digitorum superficialis (FDS) rests on top of the FDP until it divides into its 2 terminal slips that insert onto the middle phalanx.

• The pulley system is critical to flexion of the finger. The retinacular system for each of the fingers contains 5 annular pulleys and 4 cruciform pulleys. The thumb has 2 annular pulleys and 1 oblique pulley.
• The system supplies mechanical advantage by maintaining the flexor tendons close to the joint's axis of motion. In doing so, the pulleys prevent bowstringing. 

The dorsum of the hand, wrist, and forearm are divided into nine anatomic zones to facilitate classification and treatment of extensor tendon injuries. Odd numbers are used for regions overlying articular structures, with even numbers being assigned to the regions between joints, as follows:

• Zone 1 (distal interphalangeal [DIP] joint)
• Zone 2 (middle phalanx)
• Zone 3 (proximal interphalangeal [PIP] joint)
• Zone 4 (proximal phalanx)
• Zone 5 (metacarpophalangeal [MCP] joint)
• Zone 6 (dorsum of hand)
• Zone 7 (wrist)
• Zone 8 (distal forearm)
• Zone 9 (proximal forearm)

Extensor tendon injuries are often more difficult to treat than flexor tendon injuries, owing to several issues specific to extensor tendons. The extensor mechanisms of the hand are in a superficial position, not enclosed in tendon sheaths (as flexor tendons are), and often have limited retraction after injury.

Extensor tendons also tend to be thinner and flatter than flexor tendons are, as well as being in very close proximity to bony structures. This leaves them highly susceptible to adhesions and shortening, which can severely impair function and range of motion.