Clavicle fractures are common injuries, and both the injury itself, as well as fixation surgery, can be associated with moderate to severe pain.^{1 2} Adequate analgesia provision is desirable for improved patient satisfaction and early return to function. Regional anaesthetic techniques can be useful for analgesia provision and can be a viable option for surgical anaesthesia during fixation surgery for high-risk patients. However, this region has a complex innervation that remains a controversial subject.^1-3 Varying fracture locations and injury patterns add a further layer of complexity. Current literature comprises of heterogenous studies, and several different regional anaesthetic approaches, as well as combinations of these approaches, have been previously described.⁴ These include cervical plexus, selective supraclavicular nerve, superior trunk, and interscalene blocks.⁴ Additionally, the widespread adoption of ultrasound-guided regional anaesthesia has led to the emergence of interfascial techniques, such as the clavipectoral fascial plane block.⁵ Furthermore, local infiltration analgesia and haematoma block have also been described in the literature.^{6 7} Several studies have demonstrated the reliability of regional anaesthesia as a sole anaesthetic technique for clavicle fixation surgery.^{4 8 9} The option to avoid general anaesthesia is attractive, as patients with clavicle fractures may have concomitant chest or pulmonary injuries.

The combination of a cervical plexus block and interscalene brachial plexus block was previously regarded as the technique of choice for if surgical anaesthesia is desired.⁴ However, this approach is associated with the potential for hemidiaphragmatic paresis amongst other problems. This begets the question if some of the more novel, selective techniques or interfascial blocks can circumvent some of the issues from this ‘traditional’ approach whilst providing non-inferior surgical anaesthesia.

Innervation of the clavicle The complete innervation of the clavicular region has long been a subject of debate.^1-3 Nonetheless, most of its innervation seems to arise from branches of the cervical plexus and superior trunk of the brachial plexus. The supraclavicular nerve (C3,4) divides into medial, intermediate, and lateral branches to innervate the cephalad and ventral aspect of the clavicle along its entire length, as well as the sternoclavicular joint and, together with the lateral pectoral nerve (C5-7), the acromioclavicular joint.¹⁰ However caudal and dorsal surfaces of the clavicle receive differing innervation – by the subclavian nerve (C5,6) at the medial and middle thirds, and by the lateral pectoral nerve at the middle and lateral thirds.¹⁰ Although the suprascapular, spinal accessory, and long thoracic nerves have been implicated, their exact contribution to clavicular innervation remains contentious.^{1 3}

Cervical plexus block and nomenclature Cervical plexus blockade has been well described in the literature. Analgesia provision occurs by inhibiting nociceptive input from the supraclavicular nerve; however, since this nerve does not supply the caudal and dorsal surfaces of the clavicle, cervical plexus block alone is usually not sufficient for surgical anaesthesia alone.^{4 10 11} Most studies use a cervical plexus block to complement general anaesthesia or combine it with another regional anaesthetic technique such as an interscalene brachial plexus or clavipectoral fascial plane block if general anaesthesia is to be avoided.^{8 9 11}

Studies examining the efficacy of a ‘superficial cervical plexus block’ might be difficult to interpret at face value due to inconsistent nomenclature and variability in in-text descriptions and sonographic images.⁴ By definition, subcutaneous deposition of local anaesthetic along the posterior border of the sternocleidomastoid constitutes a superficial cervical plexus block.^{12 13} If the needle tip is advanced deep to the investing fascia of the neck, while remaining superficial to the prevertebral fascia, this is termed an intermediate cervical plexus block.^{12 13} The investing cervical fascia was once considered to be an impenetrable barrier to deeper local anaesthetic spread – rendering a superficial injection less effective. However, data from anatomical studies and carotid surgeries has suggested that this fascia is porous or incomplete and that a superficial injection is as efficacious as an intermediate block; although the clinical significance of this dichotomisation remains unclear.^{12 13} Studies directly comparing the efficacy of superficial and intermediate cervical plexus blocks in clavicular surgeries are lacking, although a small study reported a 20% failure rate in patients receiving superficial versus intermediate cervical plexus block in conjunction with an interscalene block.⁸ Alternatively, since the desired end-point is blockade of the supraclavicular nerve, ultrasound-guided block of this branch of the cervical plexus is an alternative that has been described.^{4 14 15}

Interscalene brachial plexus block Interscalene block targets the C5 to C7 nerve roots, and might be expected to produce blockade of the subclavian nerve that originates from the upper trunk, and lateral pectoral nerve which arises from the lateral cord or from the anterior divisions of the upper and middle trunks. Its use in clavicular fractures has been well described in the literature, and when combined with cervical plexus blockade can produce surgical anaesthesia of the clavicular region and alleviate the need for general anaesthesia.^{4 8} However, despite sonographic guidance and low-volume injections, interscalene block can be associated with undesirable side-effects such as phrenic nerve blockade, hoarseness, Horner’s syndrome, and sensorimotor block of the ipsilateral upper limb.^{9 11} This can lead to impairment in pulmonary function mechanics such as forced vital capacity and volume, although in most patients this appears to be well compensated, possibly by accessory muscles of respiration.^{9 16} However, patients may have thoracic injuries which can place them at elevated risk of respiratory failure if phrenic nerve paresis were to occur. Despite its limitations, interscalene brachial plexus block coupled with a superficial/intermediate cervical plexus block is a reliable choice if surgical anaesthesia is desired.

Selective approaches In order to minimise the problems associated with an interscalene block, more selective approaches have been adopted which target the superior trunk or the 5^th and/or 6^th cervical nerve roots.¹⁴ Intermediate cervical plexus block combined with targeted C5 and C6 is sufficient for surgical anaesthesia; while omission of the C6 component seems to be adequate if analgesia (but not anaesthesia) is the desired clinical outcome.^{4 14} The superior trunk block has been described as a alternative to the interscalene block in clavicle fractures when performed in combination with a cervical plexus or supraclavicular nerve block, the latter of which has been termed a ‘SCUT block’.¹⁵

Clavipectoral fascia and clavipectoral fascial plane block. The clavipectoral fascia lies deep to the clavicular part of the pectoralis major muscle. Medially this fascia fuses with the external intercostal membrane and first rib; laterally it thickens to form the costocoracoid ligament and attaches to the coracoid process. The clavipectoral fascia divides to enclose the subclavius muscle and attaches to clavicle superiorly, it also occupies the space between the pectoralis minor and clavicle.¹⁷ Given that the clavipectoral fascial plane contains the subclavius muscle, it should, by extension, also envelope the subclavian nerve (or nerve to the subclavius). Furthermore, since the clavipectoral fascia also surrounds the clavicle, nerve endings that supply the clavicle should also be contained within this fascia. Terminal branches of the sensory nerves, such as the suprascapular, subclavian, lateral pectoral, and long thoracic nerves pass through the plane between the clavipectoral fascia and the clavicle itself.¹⁷ Hence, the sensory innervation of the clavicle should penetrate the clavipectoral fascia, and local anaesthetic deposition within this fascial plane should at least anaesthetise the caudal and dorsal surfaces of the clavicle. Studies report success with either a single- or dual-injection approach; the latter is administered on both sides of the fracture site.^{4 5 9 17} Given observations of some studies that clavipectoral block as a sole technique allows for surgical anaesthesia, and can provide coverage of the skin overlying the clavicle, there might be cephalad spread of the injectate into the investing layer of cervical fascia which produces supraclavicular nerve blockade. The comparable anaesthetic coverage afforded by this block with a paucity of motor effects makes it an attractive alternative to the ‘traditional’ combination of a cervical plexus and interscalene brachial plexus block.⁹

Surgical site infiltration Surgical fixation under local infiltration analgesia alone has been reported in a few studies which typically use high volume local anaesthetic in combination with a vasoconstrictor.^{4 18} Subcutaneous infiltration produces local nociceptive blockade, and deeper subperiosteal infiltration is postulated to facilitate endosteal local anaesthetic spread via nutrient vessels from the periosteum; thus blocking sensory fibers in the periosteum and within bone. On a similar note, the successful use of ultrasound-guided haematoma block for pain relief in the emergency department has been reported⁷; in this approach the fracture haematoma serves as a medium for local anaesthetic spread into the surrounding structures and periosteum. Even if expertise for regional block performance is unavailable, local anaesthetic infiltration should at least be considered in fixation surgeries performed under general anaesthesia alone.^{4 6}

Other regional techniques Some small studies or reports have utilised other regional blocks, such as a supraclavicular brachial plexus or pectoralis (PECS) I or II blocks as part of the regional anaesthetic regimen with varying degrees of success.⁴ The former likely targets the trunks or divisions distal to the origin of the subclavian and lateral pectoral nerves, while the latter mainly provides block of the medial and lateral pectoral nerves, although it can be argued that spread to muscles adjacent to the clavicle (such as the pectoral muscles) might play a role in nociceptive inhibition. These will not be elaborated upon given the paucity of evidence, somewhat limited mechanistic plausibility, as well as availability of other techniques which can provide better coverage.

Conclusion Several regional anaesthetic aproaches have been described in the literature, and the feasibility of awake surgical fixation has been well reported. The regional anaesthetic of choice depends largely on whether surgical anaesthesia is required or if analgesia provision without anaesthesia is sufficient for the clinical context. If analgesia desired as part of a general anaesthetic, a superficial/intermediate cervical plexus block or supraclavicular nerve block is may suffice. Although a superficial/intermediate cervical plexus block has previously been the technique of choice for surgical anaesthesia provision, it has a propensity for undesirable motor effects such as hemidiaphramatic paresis; which can be mitigated by the use of a clavipectoral fascial plane block with or without a cervical plexus block.¹¹ Clavipectoral fascial plane block may be a promising new tool in the anaesthesiologist’s armamentarium for anaesthesia and analgesia provision in clavicle factures and fixation surgery.

References

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