Forearm and Wrist Blocks

This sections covers simple blocks for the radial, ulnar, and median nerves.

Indications

Anaesthesia/analgesia of the hand
Supplementation to partially successful upper limb block

Contraindications

Anatomy

The upper limb is supplied by the brachial plexus:

Formed by the anterior primary rami of C5 to T1
- Variably C4 to T2
Divided into roots, trunks, devisions, cords, and branches
Blocking the plexus at different levels will give a different distribution of sensory block.
Runs between the clavicle and third rib
Runs with the axillary artery into the upper limb, where it forms the major terminal branches

Sections of Brachial Plexus

The brachial plexus has five key sections:

Five roots
The nerve roots that give rise to the plexus. May be imaged as they emerge from the vertebral foramen.
Three trunks
Roots merge together to form three trunks:
- May be imaged at the interscalene level
  Deep to SCM, between anterior and middle scalene. Key landmarks:
  - Lateral border of SCM
  - Scalenus anterior
  - Interscalene groove
- Superior trunk
  From C5 & C6.
- Middle trunk
  From C7.
- Inferior trunk
  From C8 and T1.
Six divisions
Three anterior and three posterior, which then re-merge to form the cords.
- Lie posterior and cephalad to the subclavian artery
- May be imaged at the supraclavicular level.
Three cords
Imaged wrapping around the axillary artery at the infraclavicular level, and include:
- Lateral cord
- Posterior cord
- Medial cord
Branches
- Divided into major and minor terminal branches
- Major terminal branches may be imaged in the axilla

Major Terminal Branches

The major terminal branches include:

Radial nerve
- Sensation to the dorsum of the hand, generally the lateral 2.5 digits.
- Motor: Extension of elbow and fingers
Median nerve
- Sensation to the palm, and the palmar surface and dorsum of the distal phalanges of the lateral 3.5 digits
- Motor: Flexion of fingers
Ulnar nerve
- Sensation to the medial 1.5 fingers, the ulnar border of the hand (including the dorsum), and sometimes the ulnar part of the forearm
- Motor: Flexion of 4^th and 5^th digits and opposition of 1^st digit
- Most effectively blocked with a targeted axillary block
Musculocutaneous nerve
- Sensation to the lateral aspect of the forearm
- Motor: Flexion and supination of forearm
Axillary nerve
- Sensation over the “regimental patch” of the shoulder

Minor Terminal Branches

From the roots:

Dorsal scapular nerve
Long thoracic nerve
Branch to phrenic nerve

From the trunks:

Nerve to subclavius
Suprascapular nerve

From the cords:

Lateral pectoral nerve
Subscapular nerve
Thoracodorsal nerve
Median pectoral nerve
Intercostal brachial nerve
Medial brachial cutaneous nerve
Medial antebrachial cutaneous nerve Supplies upper medial part of the forearm, and can be covered with a subcutaneous bleb just distal to the axillary hairline.

Equipment

Local anaesthetic
- 1% lignocaine
- 0.75% ropivacaine
- 0.5% bupivacaine

Technique

Subdivided into:

Ultrasound
Landmark

Ultrasound Guided Approaches

Ulnar:

Identify the ulnar artery at the level of the wrist
Scan through proximally, identifying where the nerve separates from the artery in the mid-forearm
Inject ~2.5ml of LA around the vessel

Median:

Appears as an anisotropic and hyperecholic structure deep the bicepts aponeurosis
Inject ~2.5ml of LA round nerve

Radial:

Nerve runs in spiral groove in the mid-humerus, deep to tricepts
May run close to profunda brachii.

Landmark Approaches

All performed at the level of the wrist
Ensure wrist is supinated and externally rotated