Brachial Plexus Exploration Approach

What it exposes. The combined approach exposes the brachial plexus from the roots and trunks above the clavicle, through the divisions behind it, to the cords and terminal branches below. The supraclavicular limb works in the posterior triangle of the neck; the infraclavicular limb works in the deltopectoral interval. Where they meet, the clavicle is left intact for two separate windows or osteotomised for one continuous field. Three variants.

Why a combined approach is chosen. Adult traumatic lesions frequently span the clavicle. A preganglionic (avulsion) injury may be reconstructed with distal nerve transfers in the infraclavicular region, while a postganglionic rupture of the upper trunk is addressed supraclavicularly. A combined exposure lets the surgeon map the whole lesion, stimulate and record across segments, and route grafts or transfers without a second incision. Primary indications:

• Traumatic brachial plexus exploration - closed traction (stretch, rupture or avulsion) injury to confirm the lesion and perform repair, grafting or nerve transfer
• Penetrating injury with neurological deficit - sharp laceration allows primary repair within a healthy window
• Plexus tumour - benign nerve sheath tumours (schwannoma, neurofibroma) and malignant or secondarily invasive masses
• Thoracic outlet syndrome - first rib resection and plexus decompression when conservative measures fail
• Nerve transfer procedures - reconstruction of shoulder, elbow and hand function after irreversible injury
• Pain procedures - selected cases of intractable neuropathic pain Contraindications:
• Complete preganglionic avulsion of all roots with no reconstructable targets and no donor nerves
• Medical unfitness for prolonged general anaesthesia or steep positioning
• Early presentation of a closed traction injury with neurapraxia expected to recover (observe with serial examination and electrodiagnostics first)
• Active soft tissue infection over the planned incision Selecting the exposure. The choice of supraclavicular, infraclavicular or combined exposure follows the anatomical level of the lesion and the planned reconstructive strategy.

Preoperative planning. A combined plexus exploration is planned on a clear map of the lesion, not discovered at the table. Preoperative work-up defines which elements are injured and whether the injury is preganglionic (avulsion) or postganglionic (rupture), because this distinction changes the operation from grafting to nerve transfer. - Clinical examination - grade every muscle (MRC scale 0 to 5) and map the sensory deficit, including the preterminal branches (serratus anterior for the long thoracic nerve, rhomboids for the dorsal scapular nerve, supraspinatus and infraspinatus for the suprascapular nerve)

• High-resolution MRI of the plexus - identifies pseudomeningocoeles (suggesting root avulsion), neuromas in continuity and tumour
• CT myelography - sensitive for detecting nerve root avulsion when MRI is equivocal
• Electrodiagnostic studies - serial electromyography and nerve conduction studies to document the absence of recovery before exploration
• Intraoperative planning tools - nerve action potentials recorded across a lesion in continuity distinguish a conducting (recovering) segment from a non-conducting one that must be resected and grafted Alternative and supplementary approaches:
• Posterior (subscapular) approach to the plexus - rarely used, avoids the clavicle but is unfamiliar to most surgeons
• Arm and forearm approaches to individual terminal branches (axillary, radial, musculocutaneous, median, ulnar) for distal lesions
• Scapular and shoulder approaches when a free functioning muscle transfer must be docked to distal targets
• Endoscopic thoracic outlet decompression for selected thoracic outlet syndrome cases

Overview. The combined approach exposes the trunks above the clavicle, the divisions and cords below it, and the terminal branches that cross the shoulder. The plexus itself is the surgical target, so the dissection is defined less by a classical internervous plane and more by the safe anatomical intervals that bracket it. Work from superficial to deep in each window, protecting the named nerves at every layer. Brachial plexus anatomy to orient the dissection:

• Roots - ventral rami of C5, C6, C7, C8 and T1 (a prefixed plexus receives C4; a postfixed plexus receives T2)
• Trunks - upper (C5, C6), middle (C7) and lower (C8, T1)
• Divisions - each trunk splits into anterior and posterior divisions (six in total)
• Cords - lateral (anterior divisions of upper and middle trunks), medial (anterior division of lower trunk) and posterior (all three posterior divisions)
• Terminal branches - musculocutaneous, axillary, radial, median, ulnar, and the medial cutaneous nerves of arm and forearm Key preterminal branches to know during exploration:
• From the roots - dorsal scapular (C5) to rhomboids; long thoracic (C5, C6, C7) to serratus anterior
• From the upper trunk - suprascapular (supraspinatus and infraspinatus); nerve to subclavius
• From the lateral cord - lateral pectoral nerve
• From the medial cord - medial pectoral, medial cutaneous of arm, medial cutaneous of forearm
• From the posterior cord - upper and lower subscapular, thoracodorsal (latissimus dorsi) Internervous plane. There is no classical internervous muscular plane above the clavicle. The supraclavicular exposure exploits the interscalene groove between scalenus anterior and scalenus medius, where the trunks lie with the upper trunk most superficial - it is intermuscular rather than internervous. Below the clavicle a true internervous plane exists in the deltopectoral groove between deltoid (axillary nerve) laterally and pectoralis major (medial and lateral pectoral nerves) medially; deep to this, pectoralis minor is retracted laterally or detached from the coracoid to reveal the cords around the axillary artery.

The structures at risk are best organised by the layer in which they are encountered - naming them per layer is a classic examination structure for this approach. Superficial layer (skin, subcutaneous tissue, platysma):

• Supraclavicular nerves (sensory, C3, C4)
• External jugular vein
• Cephalic vein (infraclavicular) Interscalene layer (supraclavicular):
• Phrenic nerve on anterior scalene
• Long thoracic nerve of Bell on scalenus medius
• Dorsal scapular nerve piercing scalenus medius
• Suprascapular nerve from the upper trunk
• Subclavian artery (posterior to scalenus anterior) and subclavian vein (anterior)
• Transverse cervical and suprascapular vessels
• Thoracic duct (left side only) Infraclavicular layer (cords and terminal branches):
• Axillary artery and vein
• Lateral, posterior and medial cords
• Musculocutaneous nerve (pierces coracobrachialis)
• Lateral and medial pectoral nerves

Extensile options. Extend the supraclavicular limb proximally along the interscalene groove toward the intervertebral foramina (formal intraforaminal root work is rare and shared with neurosurgery). Unite the two limbs by crossing the clavicle with a stepladder incision, or by a clavicular osteotomy for continuous exposure. Extend the infraclavicular limb distally down the deltopectoral groove and medial arm to expose the terminal branches, connecting with arm and forearm approaches for distal nerve work. Clavicular osteotomy morbidity. A clavicular osteotomy converts separate exposures into one continuous field for pan-plexus lesions, but it adds nonunion, hardware prominence and infection risk. Predrill and preplate before osteotomising, repair rigidly, and reserve it for cases that genuinely need cross-clavicular access.

• Neurolysis - external neurolysis to free the plexus from scar, callus or tumour
• Primary nerve repair - direct epineurial or fascicular repair of sharp, clean transections
• Nerve grafting - interposition autograft (sural nerve, medial antebrachial cutaneous nerve) for postganglionic rupture with a gap
• Nerve transfers - spinal accessory to suprascapular; triceps branch to axillary; partial ulnar fascicle to the musculocutaneous nerve (Oberlin) or a double fascicular transfer; intercostal nerves to the musculocutaneous nerve; medial pectoral nerve for free muscle transfer
• Tumour excision - enucleation of benign nerve sheath tumours or margin-wide resection of malignancy
• Thoracic outlet decompression - first rib resection and release of congenital bands

Guidelines, Registries and Global Practice Brachial plexus reconstruction is practised at specialist units worldwide, and the principles converge across examination systems. The evaluation and management of adult traumatic injuries are informed by the Narakas and Sunderland frameworks, high-resolution MRI and CT myelography for lesion localisation, and intraoperative nerve action potentials to guide resection and reconstruction. Side-by-side principles (where guidance converges): | Body | Position on adult brachial plexus injury |

|------|------------------------------------------| | AO Foundation / AS nerve injury principles | Microsurgical technique, intraoperative action potential recording, early reconstruction of sharp lacerations and delayed reconstruction of closed traction injuries once recovery is excluded | | BOA / BOAST (nerve injury) | Specialist referral, meticulous preoperative assessment and documentation, reconstruction by a surgeon with peripheral nerve expertise | | International consensus (nerve transfer) | Prioritise restoration of elbow flexion, then shoulder stability and abduction, then hand function; use expendable donor nerves to minimise donor morbidity | Population and outcome context:

• Adult traumatic brachial plexus injuries are most common in young men after high-energy motorcycle crashes, with a traction mechanism that frequently produces a combination of preganglionic avulsion and postganglionic rupture.
• Outcomes depend on the level and completeness of the lesion, the time to reconstruction, and the quality of the donor nerves and end targets; proximal muscle recovery (shoulder and elbow) is generally more reliable than distal (hand) recovery. Global practice variation. In well-resourced centres, microsurgical reconstruction with grafting and nerve transfers is standard, frequently combined at a second stage with free functioning muscle transfer and secondary tendon procedures. In resource-limited settings, the same priorities are pursued with simpler grafting and palliative tendon transfers, accepting that distal hand reconstruction may be limited. Consent (globally applicable). Discuss phrenic nerve injury and hemidiaphragm paralysis, long thoracic nerve injury and winged scapula, vascular injury (subclavian and axillary vessels), chylous leak on the left side, incomplete or delayed recovery, the need for staged secondary procedures, and persistent neuropathic pain.