UGRAbas

2 – Anatomy: The trajectory of the sural nerve

The sural nerve is a sensory nerve made of the fusion of the medial sural cutaneous nerve from the tibial nerve and of a communicating branch from the lateral sural cutaneous nerve from the common fibular nerve

The two sural cutaneous nerves pierce the deep fascia – together with the short saphenous vein – before the fusion that makes the sural nerve

The sural nerve descends posterior to the lateral malleolus together with the short saphenous vein

The sural nerve innervates the postero-lateral part of the skin cover of the ankle and supply calcaneal branches that innervate the lateral heel and lateral dorsal cutaneous nerves that innervate the lateral margin of the foot

Image missing — Sural nerve (magenta), lateral calcaneal branches (cyan), lateral dorsal cutaneous branches (green)

1 – Indications

The indications of an ultrasound guided ankle block is forefoot surgery as an alternative to a combined popliteal sciatic and midthigh saphenous nerve blockade

It is not indicated for surgical anaesthesia if a tourniquet is applied proximal to the ankle level

All five nerves innervating the foot have to be anaesthetized which can be painful in the awake patient

3 – Anatomy: The trajectory of the superficial peroneal nerve

The superficial peroneal nerve (SPN) branches off the common peroneal nerve in the proximal lateral compartment of the leg

The SPN descends in the lateral compartment between the peroneal muscles and the fibula. It innervates the peroneal muscles

Approx. 10 cm above the lateral malleolus the SPN emerges between the lateral compartment (peroneal muscles) and the anterior compartment (the extensor muscles of the foot) and pierces the deep fascia of the leg

Above the deep fascia the SPN splits into the intermediate and medial dorsal cutaneous nerves that supply cutaneous innervation to the antero-lateral part of the distal leg, ankle and dorsum of foot – including the dorsal digital nerves that supply innervation of dorsal part of the toes and the interdigital spaces – except the first interdigital space

4 – Sonoanatomy: The intercostal nerves

The intercostal nerves are located between the innermost and the internal intercostal muscles

Typically the intercostal nerves are not visible with ultrasound. But the adjacent intercostal arteries and veins can be visualized with Color Doppler

3 – Scanning technique for ultrasound guided intercostal block

– Place the patient sitting or in the lateral decubitus position

– Place the high-frequency linear probe in the parasagittal paravertebral plane approx. 10-15 cm from the sagittal midline. The lateral cutaneous branches branch off in the midaxillary line

– Visualize the target intercostal space (see next page)

– Insert the needle with in-plane technique from the cranial end of the probe

– Advance the needle to the fascial plane between the internal and the innermost intercostal muscles and inject 5 mL of local anaesthetic

– The needle shold be kept meticulously in-plane in order to avoid pneumothorax

1 – Probes

Basic UGRA can be performed solely with a high-frequency linear probe

Advanced UGRA requires high-frequency linear as well as low-frequency curved array probes

1 – Indications

– Chest drain insertion

– Rib fractures

– Rescue block with failed TAP block of the intercostal TAP plexus

2 – Electrical nerve stimulation

Basic UGRA can be performed only with ultrasound without supplemental electrical nerve stimulation (ENS) technique

Advanced UGRA requires a combination of ultrasound and ENS for various blocks

ENS is obsolete for most blocks for the purpose of nerve localisation. However, sometimes peripheral nerves are not visible with ultrasound and ENS can be useful in order to confirm nerve identity

Generally, the main purpose of ENS is a safeguard in order to assist avoiding accidental piercing of peripheral nerves and intraneural injection

3 – Colour Doppler mode

Colour Doppler mode can be very useful to identify blood vessels surrounding deeply located target nerves

2 – Anatomy of the intercostal nerve

The spinal nerve is formed by the union of the dorsal sensory root and the ventral motor root

It passes the intervertebral foramen and branches into a ventral and a dorsal ramus. The dorsal ramus innervates the intrinsic back muscles. The ventral ramus of the intercostal nerves run anterior together with the intercostal artery and vein between two adjacent ribs sandwiched between the socalled innermost intercostal muscle (the deepest intercostal muscle layer just separated from the parietal pleura by the endothoracic fascia) and the internal intercostal muscle (the middel intercostal muscle layer). The outermost intercostal muscle layer is called the external intercostal muscle.

In the midaxillary line the intercostal nerve gives off a lateral cutaneous branch that pierces the internal and external intercostal muscles and innervates the lateral thoracic wall

Anteriorly the intercostal nerve terminates in the anterior cutaneous branch that innervates the skin covering the medial part of the trunk