2 – Anatomy

With the superficial serratus plane block, the needle tip is inserted into the fascial space between the serratus anterior muscle and the latissimus dorsi muscle caudad to the teres major muscle

Local anaesthetic injected into this fascial plane covers the thoracic intercostal nerves and their lateral cutaneous branches – and also the thoracodorsal nerve which innervates the latissimus dorsi muscle and the long thoracic nerve which innervates the serratus anterior muscle. The last mentioned nerves run alongside the thoracodorsal artery.

Blanco R, Parras T, McDonnell JG, Prats-Galino A (see ref.) have also described a serratus plane block with injection of local anaesthetic into the fascial plane deep to the serratus anterior muscle

This deeper serratus plane block also produces analgesia of the thoracic intercostal nerves and the lateral hemithorax; however, the analgesia of the deep block seems to last a shorter time than the superficial serratus plane block

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Serratus anterior m. (blue asterixs); teres major m. (magenta arrow); latissimus dorsi m. (green asterix); pectoralis major m. (yellow asterix); fifth rib (blue arrow); the needle insertion position is displayed

3 – Sonoanatomy and needle insertion

Place the patient supine

Place the probe in the parasagittal plane on the midclavicular line and the fifth rib is identified by counting from above. The rib is tracked to the midaxillary line. Rotate the probe 45 degrees from the axial plane.

The latissimus dorsi, the serratus anterior and the teres major muscles are overlying the fifth rib (see previous page). The thoracodorsal artery can be used as a marker of the fascial plane between the latissimus dorsi and serratus anterior muscles.

The needle is inserted from the anterior end of the probe and advanced in-plane

Inject 25 mL ropivacain 0.2% into the fascial plane between the serratus anterior and latissimus dorsi muscles

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The upper image shows the position of the probe and the in-plane needle orientation.
The lower image shows the fascial plane between the latissimus dorsi m. (blue asterix) and the serratus anterior m. (red asterix). Cr (cranial); Ca (caudad); r3-r5 (ribs 3-5); teres major m. (green asterix). The needle is displayed (magenta).

4 – References

Blanco R, Parras T, McDonnell JG, Prats-Galino A: Serratus plane block: a novel ultrasound-guided thoracic wall nerve block,
Anaesthesia 68: 1107-1113 (2013)

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11 – Sonoanatomy: Step two of the PECS II block

At the infero-lateral margin of the minor pectoral muscle the strong Gerdy’s ligament (= the lower part of the clavicopectoral fascia) connects the minor pectoral muscle to the axillary fascia

When the needle tip penetrates Gerdy’s ligament it enters the the lower part of the axillary space between the Gerdy’s ligament antero-laterally and the serratus anterior muscle covering the lateral thoracic wall medially in the axilla

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Gerdy’s ligament (cyan arrows), minor pectoral muscle (green asterix), major pectoral muscle (red asterix), serratus anterior (magenta asterix), pleura (red arrows), ribs III and IV (r3 and r4)

12 – Sonoanatomy: Identify the ribs

Below the lateral third of the clavicle the axillary artery is typically located on top of the second rib

Ribs III and IV can be identified by sliding caudad and counting

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Axillary artery (A), rib 2 (r2), rib 3 (r3), major pectoral muscle (red asterix), minor pectoral muscle (green asterix), serratus anterior muscle (magenta asterix)

13 – Sonoanatomy: Needle insertion for step two of PECS II

The needle is inserted in-plane from the cranial end of the probe until the tip of the needle penetrates the infero-lateral margin of the minor pectoral muscle and enters the lower part of the axilla between the Gerdy’s ligament and the serratus anterior muscle

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Gerdy’s ligament (cyan arrow), minor pectoral muscle (green asterix), serrratus anterior muscle (magenta asterix), needle (red), rib III (r3), rib IV (r4)

15 – References

Blanco R: The ‘pecs block’: a novel technique for providing analgesia after breast surgery. Anaesthesia 66(9): 847–848 (2011)

Blanco R, Fajardo M, Parras Maldonado T: Ultrasound description of Pecs II (modified Pecs I): A novel approach to breast surgery. Rev Esp Anestesiol Reanim. (2012) (

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1 – Indications

The serratus plane block produces analgesia of the lateral thoracic wall including the axilla.

The indications of the serratus plane block are postoperative analgesia after surgery of:

– lateral thoracic wall

– breast

– axilla

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The surface area of analgesia with the serratus plane block

5 – Anatomy: The clavipectoral fascia penetrated by nerve and vessels

The part of the clavipectoral fascia close to the clavicle – the costocoracoid ligament – is penetrated by the cephalic vein, the lateral pectoral nerve and the thoracoacromial artery

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The clavipectoral fascia is pierced by the lateral pectoral nerve together with the cephalic vein (magenta arrow) and by the thoracoacromial artery (cyan arrow). The cephalic vein runs upward in the deltopectoral groove between the deltoid muscle (cyan asterix) and the major pectoral muscle (green asterisks)

6 – Anatomy: The nerves in the axilla

The anterior wall of the axilla consists of the major and minor pectoral muscles and the clavipectoral fascia

The medial wall of the axilla is the lateral thoracic wall with costae I-IV and intercostal muscles – and the serratus anterior muscle

The lateral wall is the intertubercular groove of the humerus and the posterior wall is the subscapularis, teres major and latissimus dorsi muscles.

The axilla contains some nerves that are relevant for axillary extension of breast surgery:

1) the lateral cutaneous branches of the intercostal nerves
2) the anterior intercostal branches of the intercostal nerves
3) the long thoracic nerve that innervates the serratus anterior muscle
4) the thoracodorsal nerve that innervates the latissimus dorsi muscle

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Lateral cutaneous branch of intercostal nerves I (black arrow), II (white arrow), IV (green arrow), major and minor pectoral muscles (green and cyan asterixs), latissimus dorsi (magenta asterix), serratus anterior (blue asterix), long thoracic nerve (magenta arrows), thoracodorsal nerve (cyan arrows)