Ultrasound-guided single needle tip placement below axillary artery in the infraclavicular area: A cadaveric study : Journal of Anaesthesiology Clinical Pharmacology

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Ultrasound-guided single needle tip placement below axillary artery in the infraclavicular area: A cadaveric study

Diwan, Sandeep; Feigl, Georg1; Nair, Abhijit2,

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Journal of Anaesthesiology Clinical Pharmacology 38(4):p 658-661, Oct–Dec 2022. | DOI: 10.4103/joacp.JOACP_694_20
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The motor evoked responses of the posterior cord during a neurostimulation-guided vertical infraclavicular block (ICB) is associated with maximum efficacy.[1] Traditional parasagittal ultrasound (US)-guided ICB advocates needle position below the second part of the axillary artery (AA) and appearance of a doughnut sign on injection of local anaesthetic (LA) agent is followed by a successful block.[2] The posterior and medial brachial plexus cords are commonly situated anywhere from 6 to 8 o’clock position.[3] Our aim was to understand the latex spread in cadaveric infraclavicular area, after a single injection of 20 ml latex posterior to the AA in Thiel embalmed cadavers.

Material and Methods

The cadavers we investigated were two bodies donated to science (BDTS) as per the rules of the donation program of the Department of Macroscopic and Clinical Anatomy of the Medical University of Graz and the Styrian burial law. The study was approved by Medical University of Graz. The BDTS were embalmed with Thiel’s method which provides very lifelike conditions for investigations for applied regional anaesthesia interventions.[4]

Bilateral ICBs were performed using latex in both cadavers. In first cadaver, 20 ml red latex was injected posterior to the AA. In second cadaver, 20 ml blue latex was injected posterior to the AA. A linear US transducer (5–13 mHz, Sonosite Inc., USA) was placed in parasagittal plane medial to the coracoid process below the clavicle. The needle (Pajunk 50 mm, Pajunk®, Geisingen, Germany) was inserted in-plane from cephalad to caudal below the linear probe [Figure 1a]. The final needle tip was targeted posterior to the AA and was monitored under US [Figure 1b]. The needle tip was stabilized and 20 ml red latex was injected in cadaver 1, and 20 ml blue latex in cadaver 2. A continuous visualization of the spread was monitored and recorded. Injecting small boluses confirmed the posterior, medial and lateral spread of latex. Cadaver 1 underwent an open dissection and the second cadaver was frozen (‒20ºC) for 2 weeks before subjecting to the cross-section. After ensuring that the latex had hardened after 2 days, the infraclavicular area of the cadaver 1 was dissected carefully by elevating all layers, that is, pectoralis major (PMa) and pectoralis minor (PMi). The branches of the thoracoacromial artery (TAA) were carefully dissected away from the PMa and the PMi. The pectoral muscle was reflected until the sheath enclosing the red latex was visualized [Figure 2a]. The extent of the sheath engulfing the red latex was examined for spread and extravasation. The sheath engulfing the brachial components was dissected and elevated gently and the red latex were closely examined. The spread of the red latex on the dorsal and ventral of the brachial plexus cords – the posterior, the lateral and the medial were examined. The distal nerves in particular the radial, median, ulnar, and musculocutaneous were examined for inundation with red latex.

Figure 1:
(a) Left parasagittal infraclavicular single needle-tip placement an injection of red latex. (b) Needle placement (white dashed line) posterior to the AA and spread of dye observed in real time (red-dotted area)
Figure 2:
(a) Left infraclavicular area: The plane between the PMa and minor reflected medially depicting the thoraco-acromial artery and the pectoral nerves. Immediately below the PMi is the lateral cord. Contrast is seen lateral to lateral cord. (PMa, pectoralis major; PMi, pectoralis minor). (b) Left infraclavicular area: Retracting the and cutting the conjoint tendon reveals the red latex spread along the lateral, medial and superior aspect of the lateral and posterior cord. The posterior cord is posterior and medial to the lateral cord, and, lateral and posterior to the subclavian artery. (SuBM, subclavius; LC, lateral cord; PC, posterior cord; SCA, subclavian artery; SCV, subclavian vein; TAA, thoraco-acromial artery; TAAbr, branches of TAA; CT, conjoint tendon)

After a complete examination, in cadaver 1 (bilateral) with the clavicle intact the brachial plexus component was removed en masse from the level above the clavicle until the 5 cm distal to the nerves engulfed in latex. Both specimens were scrutinized on the ventral and the dorsal aspects for involvement of cords and nerves with red latex.


In open dissection, the red latex was visualized emerging from beneath the AA, engulfing the lateral and posterior cord on its lateral aspect [Figure 2b]. Superficially the latex reached an upper limit below the subclavius muscle [Figure 2b]. The branches of TAA clear of latex could be seen criss-crossing the above the brachial cords [Figure 2b]. After the TAA was reflected lateral, the red latex was visualized inundating the cords of brachial plexus on its ventral aspect as it emerged from below the AA and was sandwiched between the AA and the axillary vein [Figure 2b]. Distally the latex encompassed the AA, the posterior cord and its terminal radial nerve, beneath the sheath as far as 10–12 cm below the clavicle [Figure 3a]. The axillary nerve in its proximal part, the musculocutaneous nerve until its proximal third were stained [Figure 3a]. The lateral and medial roots of the lateral and medial cord were heavily stained until the formation of the median nerve. The intercostobrachial nerves were totally spared [Figure 3b].

Figure 3:
(a) Left infraclavicular area: Lateral retraction of deltoid demonstrates the neurovascular sheath. (b) Left infraclavicular area: The sheath is reflected medially and the latex gently peeled off from the cords demonstrating the formation of the medial nerve, the posterior cord terminating into the radial nerve and the musculocutaneous nerve disappearing into the coracobrachialis. (TAA, thoracoacromial artery; NVS, neurovasculae sheath; ICBN, intercostobrachial nerve; PECMi, pectoralis minor; MrM, medial root of median; LrM, lateral root of median; McN, musculocutaneous; RN, radial nerve; MN, median nerve; SCA, subclavian artery)

Examination of the ventral area of the en masse specimen revealed latex engulfing the lateral cord on its lateral aspect, posterior cord from its beneath and medial side, the lateral root of median, the medial root of median, median and the latex was sandwiched between the median and radial nerves [Figure 4]. In both specimens, similar findings were observed with minor variations.

Figure 4:
Left infraclavicular area: The specimen of brachial plexus cord below the level of clavicle depicting the latex engulfing the lateral cord, lateral root of median, medial root of median, median, radial, and musculocutaneous nerves. The axillary nerve from the posterior cord must be surrounded by the latex at its emergence. (SuBM, subclavius muscle; AxN, axillary nerve; MrM, medial root of median; LrM, lateral root of median; McN, musculocutaneous; CB, coracobrachialis; RN, radial nerve; MN, median nerve; SCA, subclavian artery)

The cross-section in the proximal infraclavicular area revealed the blue latex encompassing the cord beneath the AA (a customary position for posterior cord), cord between the AA and vein, the axillary vein (a customary position medial cord) and the cord superior and medial to the AA (a customary position lateral cord) [Figure 5a]. Latex distribution was perceived on the superior part of the musculocutaneous nerve in the muscular area of the coracobrachialis muscle [Figure 5a]. The cord superior to the AA was separated from the cords between and beneath the AA. However, there was no latex penetration between the two cords positioned between and beneath the artery [Figure 5a]. In the cross-section 5 cm distal to the proximal, the blue latex thinned out posterior to the artery but was well contained medial and superior to the artery [Figure 5b]. A periarterial distribution was noted [Figure 5b]. The cross-sections revealed fascicles (dark brown) of each cord interspersed with connective tissue (light brown) [Figure 5c]. Fascicular pattern was denser in the cords between and beneath the artery [Figure 5c].

Figure 5:
(a) Proximal cross-section at the left infraclavicular area demonstrating the blue latex engulfing the all three brachial cords. The spread is far as the ventral aspect of the musculocutaneous nerve. (b) Distal cross-section depicting the periarterial blue latex involving the pf-MC and PC and consistently the LC. (c) Expanded figure demonstrating the blue latex engulfing the brachial cords. The dark brown shadows are the nerve fascicles and light brown interspersed are the connective tissue. (pf-LC, possible fascicles of lateral cord; pf-MC, possible fascicles of medial cord; pf-PC, possible fascicles of posterior cord; AA, axillary artery; AV, axillary vein; CB, coracobrachialis)


Our cadaveric open dissection and cross-sections demonstrates that a single injection posterior to the AA leads to adequate spread along all the brachial plexus cords in the infraclavicular area.

The success of neurostimulation-guided ICB depends on the localization of posterior cord with extensor muscle response at not less than 0.4 Ma.[1,5] Ootaki et al. were probably the first ones to demonstrate an US-guided ICB in real time at the proximal cord level.[2] US-guided separate injections at each cord were performed to increase block efficacy at the infraclavicular level.[6] Prediction of a successful block with a single injection posterior to the AA was first reported in a very limited case series.[7] A posterolateral ‘U’ spread of LA around the AA under US guidance predicted successful ICB.[8] A magnetic resonance imaging study at the infraclavicular level suggested that LA can be deposited at a 8 o’clock position will deliver adequate results in clinical practice.[3]

Questions were raised considering the efficacy of block after a single-needle placement posterior to the AA in comparison to triple injection US-guided infraclavicular approach.[8-10] Our cadaveric study bespeaks that positioning the needle tip under US-guidance posterior to the AA and upon 20 ml latex injection permits uninhibited spread across three cords of brachial plexus and related terminal nerves.

In clinical practice in patients with crush injuries of the hand, the distal motor evoked responses would not be obtained and are, therefore, appropriate candidates for US-guided ICB with injections of LA injection’s posterior to the AA.

Existence of septum is described to restrict diffusion of LA during an US-guided parasagittal ICB.[11] Based on our study, we demonstrated an unrestricted diffusion of red latex involving three cords with spread to distal nerves, after a single-point injection posterior to the AA. No compartmentalization was observed in the cross-section specimen except for blue latex which did not penetrate between the two cords beneath the AA. Nevertheless, the three cords were equally surrounded by the blue latex. Fascial clicks are described in clinical practice, during penetration of the neurovascular sheath and the sheath of the septum. The triad of fascial click, U-shaped distribution of LA, and anterior displacement of the AA are highly predictive of a successful ICB.[12] The cadaveric sample size was a limitation in our study. Further differing volumes (20–30 ml) of latex would have resulted in different outcomes. Latex solidifies and we are uncertain if injections of solution like methylene-blue dye would have given different results.

To conclude, based on the results of our cadaveric study, we recommend needle-tip placement posterior to the AA and to estimate in real time the spread of LA around the three cords in clinical practice.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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Cadaver; infraclavicular; nerve block; regional anaesthesia; ultrasonography

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