When preparing a patient for brachial plexus exploration, the shoulder is elevated, usually by a folded sheet, and the patient’s head is rotated away from the side to be exposed. On this cadaver, blue towels are used to demarcate the operative field (Slide 1). An incision is planned beginning along the posterior border of the sternocleidomastoid muscle extending inferiorly to the midportion of the clavicle and extending further inferiorly and laterally along the deltopectoral groove toward the axilla.
Initial Operative Exposure
During the initial skin incision, the platysma is divided and the loose connective tissue of the posterior cervical region is opened. Slide 2 shows self-retaining Weitlaner retractors holding soft tissue structures anteriorly and posteriorly. The clavicle extends across the midportion of the incision and demarcates two approaches to the brachial plexus. The pectoralis major and deltoid muscles are found below the clavicle. The sternocleidomastoid is located in the supraclavicular space. A large fat pad, which lies posterior to the sternocleidomastoid, is on the side of the initial dissection when using the supraclavicular approach to the brachial plexus.
Initial Soft Tissue Dissection for the Supraclavicular Approach
Slide 3 depicts a slightly improved dissection of the clavicle along the midportion of the incision. The sternocleidomastoid belly is better revealed. Detaching a portion of the clavicular head of the sternocleidomastoid muscle to enable its anterior retraction is a standard procedure. The omohyoid muscle is the only transverse running muscle in the neck. In Slide 3, the omohyoid muscle has been dissected and can be seen in the midportion of the supraclavicular plexus dissection.
Circumferential Dissection of the Omohyoid Muscle
Scissors have been passed under the omohyoid muscle in Slide 4. The first major landmark in the dissection of the posterior triangles of the neck is circumferential dissection and transection of the omohyoid muscle. The omohyoid muscle is secured with sutures to allow for its reapproximation during closure.
After Transection of Omohyoid Muscle
In this cadaveric specimen, the omohyoid muscle has been transected and the two portions are reflected anteriorly and posteriorly and attached with hemostats (Slide 5). The transverse cervical vessels are located directly under the omohyoid muscle. The transverse cervical artery and vein traverse the supraclavicular plexus elements. The next step in the dissection is the circumferential dissection and ligation of the supraclavicular plexus elements.
Initial Dissection of Anterior Scalene Muscle
A wider exposure shows the transverse cervical vessels in the supraclavicular space just deep to the omohyoid muscle (Slide 6). The initial elements of the supraclavicular brachial plexus along the superior aspect of the wound are starting to appear. The sternocleidomastoid is reflected medially by one blade of a Weitlaner retractor. Deep to the sternocleidomastoid lies the anterior scalene muscle and running along the anterior border of the anterior scalene is the phrenic nerve. Dissection of the phrenic nerve is an important initial landmark. The phrenic nerve must be mobilized and protected to prevent inadvertent injury during the remainder of the dissection. The phrenic nerve can also be traced back proximally to find its contribution from C5, thereby locating the C5 root and upper trunk. In this cadaver, the connection between the phrenic nerve and the C5 root has been severed during the dissection. After the phrenic nerve has been protected, the anterior scalene muscle can be resected to allow for better proximal exposure of supraclavicular plexus elements.
After Resection of Transverse Cervical Vessels
The transverse cervical vessels have been sectioned and retracted out of the way (Slide 7). The C5 and C6 nerve roots are giving rise to the upper trunk superiorly. The phrenic nerve and the anterior scalene muscle are still visible at this point. Some of the anterior scalene muscle has been resected proximally to allow for visualization of the remainder of the supraclavicular plexus elements.
Wide View Perspective
Slide 8 provides an overview of the anatomic dissection to this point in the exploration of the supraclavicular brachial plexus. The clavicle runs along the inferior aspect of the dissection. The deltoid and pectoralis major muscles are located below the clavicle. The omohyoid muscle is reflected medially and laterally. The lateral-most portion of the omohyoid muscle is clearly seen when a hemostat is attached. The transverse cervical vessels below the omohyoid muscle have been resected, and a portion of the anterior scalene muscle has been resected. The phrenic nerve has been identified. The C5 and C6 nerve roots are evident in the center of the wound.
Close View of Supraclavicular Plexus
In Slide 9, a total view of the supraclavicular dissection is shown. The C5 and C6 nerve roots are evident. Inferiorly, C5 and C6 give rise to the upper trunk before passing under the clavicle. The C7 nerve root and middle trunk are also evident. In a standard approach to the supraclavicular plexus, the next step in the dissection is to work further inferiorly and to reveal the C8 and T1 roots. Further dissection shows the branches of the upper trunk.
Dissection of Entire Supraclavicular Plexus with Iatrogenic Vertebral Artery Injury
The entire supraclavicular brachial plexus is exposed. C5, C6, C7, C8, and T1 roots make up the five roots of the brachial plexus. Further distal, the C5 and C6 roots give rise to the upper trunk just before passing under the clavicle. The C7 root continues on as the middle trunk. Inferiorly, the C8 and T1 roots combine to form the lower trunk. Along the depths of the wound underneath the anterior scalene muscle, the vertebral artery appears. Along the medial and deep aspects of the exposure and under the anterior scalene muscle, which attaches to the anterior tubercles of the vertebral bodies, the foramina transversarium conveys the vertebral artery with its accompanying veins and sympathetic chain. Iatrogenic injury to the vertebral artery is possible with a far proximal dissection of the plexus. Slide 10 demonstrates an iatrogenic injury to the vertebral artery.
Wide View at Completion of Supraclavicular Plexus Dissection
Reviewing the anatomy, the clavicle runs across the midportion of the dissection. The pectoralis major and deltoid muscles are found in the infraclavicular region. The C5, C6, C7, C8, and T1 nerve roots are evident. The sternocleidomastoid is reflected anteriorly by a Weitlaner retractor. The omohyoid muscle has been transected and is retracted medially and laterally (Slide 11). The omohyoid muscle is then attached to a hemostat. The transverse cervical vessels have been transected. The phrenic nerve is seen along the border of the anterior scalene muscle. The next step in the dissection is to formally identify the upper, middle, and lower trunks and then to dissect the branches of the upper trunk in the supraclavicular compartment.
Resection of Middle Scalene and Dissection of Long Thoracic Nerve
To show the long thoracic nerve, C5 and C6 are elevated in Slide 12. A portion of the middle scalene muscle has been resected. The long thoracic nerve originates along the posterior border of the C6 nerve root. The dorsal scapular nerve arises medially from the C5 root. The dorsal scapular nerve is important in localizing the level of plexus injury.
Divisions of the Upper Trunk
The upper trunk divides into divisions just before passing under the clavicle. In Slide 13, the upper trunk is seen superficially. Also depicted is the suprascapular nerve, the main branch of the upper branch of the trunk prior to its separation into divisions at roughly the level of the clavicle, and the anterior and posterior divisions of the upper trunk. The anterior division of the upper trunk forms a portion of the lateral cord, while the posterior division contributes to the posterior cord.
Complete View of Brachial Plexus Showing C8 and T1
At this stage of the dissection, there is a wide exposure. Cerebellar retractors are retracting the soft tissue elements. The sternocleidomastoid and belly of the anterior scalene muscle can be visualized along the medial depths of the wound. The phrenic nerve is present, and C5 and C6 are forming the upper trunk. C7 lies just below C6, giving rise to the middle trunk. C8 and T1 lie inferiorly, with T1 here being gripped by a pair of forceps (Slide 14).
Entire Superclavicular Plexus with Penrose Drains
Slide 15 demarcates the five roots of the brachial plexus. Penrose drains are routinely used during operative dissections to safely manipulate the nerve root proper. Penrose drains are placed upon each root of the brachial plexus. The divisions of the upper trunk are evident, as well as the clavicle, pectoralis major muscle, and deltoid. The plexus elements are coursing toward the deltopectoral groove on the infraclavicular compartment.
Entire Supraclavicular Plexus Penrose Drains Upon Trunks
Superiorly, the Penrose drain encircles the C5 and C6 roots as they form the upper trunk. The Penrose drain around C7 has been advanced distally and now encircles the middle trunk. More inferiorly, there is a Penrose drain upon the lower trunk. As evidenced here, the subclavian artery runs near the lower trunk (Slide 16). In the area of the clavicle, a separate Penrose drain has been placed around the subclavian artery. With this dissection complete, it is now time to move to the infraclavicular plexus exposure.
Beginning Dissection of Infraclavicular Plexus
Next is the infraclavicular aspect of the brachial plexus dissection. Slide 17 shows the most superficial aspects of the dissection. The subcutaneous fat overlying the deltoid and pectoralis major muscles has been removed and self-retaining retractors are positioned. The clavicle runs transversely in the superior portion of the image. The fat pad within the deltopectoral groove is evident. The dissection will begin along this fat pad and will follow it deep until the lateral cord is evidenced.
View of Entire Supraclavicular and Infraclavicular Brachial Plexus Exposure Before Entering the Deltopectoral Groove
The Weitlaner retractors are positioned at the level of the clavicle and inferiorly over the deltoid and pectoralis muscles (Slide 18). The supraclavicular plexus elements course under the clavicle in the direction of the deltopectoral groove. The origin of the suprascapular groove appears just before the upper trunk passes underneath the clavicle. With this orientation evident, the dissection within the deltopectoral groove proper commences.
Beginning Dissection of Deltopectoral Groove
In Slide 19, the pectoralis major muscle is reflected off of the clavicle. In operative specimens, a cuff of the pectoralis major muscle will be left attached to the clavicle to allow for reattachment of the muscle along its normal anatomic orientation. The deltopectoral vessels are evident in this dissection. Dissection and either mobilization or ligation of the deltopectoral artery and vein are important initial steps.
Deeper Dissection of Deltopectoral Groove
The dissection advances deeper along the deltopectoral groove. The deltopectoral artery and vein have been ligated. The pectoralis major muscle has been divided with a clump of muscle left along the clavicle (Slide 20). Paralleling the intraoperative dissection in the midportion of the dissection, pectoralis branches heading into the pectoralis major muscle are evident. Dissection and preservation of these branches is important in operative specimens. The pectoralis branches may be used for neurotization to the musculocutaneous nerve or to other more distal branches of the brachial plexus in select patients.
Wide View of Supraclavicular and Infraclavicular Plexus
At this stage of the dissection, the supraclavicular brachial plexus dissection is seen coursing under the clavicle at the level of the deltopectoral groove. More inferiorly, the pectoralis major muscle has been resected and retracted with a Weitlaner retractor. The deltopectoral groove is opened, and pectoralis branches are dissected within the deltopectoral groove (Slide 21). The fat pad within the deep aspect of the deltopectoral groove is becoming evident. The next step in dissection is mobilization of the pectoralis minor muscle.
Pectoralis Minor Dissection
In this dissection of the pectoralis minor muscle in the cadaveric specimen, the pectoralis branches have been sacrificed to allow for ease of dissection. The pectoralis minor muscle has been circumferentially dissected and is evident here in the infraclavicular space (Slide 22). The pectoralis minor muscle is divided to allow for exposure of the deep aspects of the infraclavicular compartment.
Wide View After Ligation of Pectoralis Minor Muscle
This wide view (Slide 23) demonstrates both supraclavicular and infraclavicular plexus exposures after division of the pectoralis minor muscle. The two edges of the pectoralis muscles are retracted laterally by a Weitlaner retractor. The fat pad lying under the pectoralis minor muscle is apparent. The course of the brachial plexus elements is leading directly to this fat pad. During the next stage of the dissection, this fat pad will be entered and the first neural element encountered will be the superficial-most cord, the lateral cord.
Initial Dissection of the Lateral Cord
Neural elements along the infraclavicular compartment are becoming visible (Slide 24). Superiorly, a small portion of the clavicle is present. A fat pad underneath the pectoralis minor muscle has been opened and the initial dissection of the lateral cord is made.
Dissection of the Lateral Cord
The subclavian artery and vein lie medially to the lateral cord. Inferiorly are the two terminal divisions of the lateral cord, the musculocutaneous nerve, and the lateral cord contribution to the median nerve (Slide 25). The musculocutaneous nerve courses more laterally, while the lateral cord contribution to the median nerve courses over the subclavian artery.
Lateral Cord and Vessels
Here is a slightly wider dissection of the lateral cord, following the course of the lateral cord proximally toward the area of the clavicle (Slide 26). Distally, the musculocutaneous nerve is present. A large venous branch crosses over the lateral cord contribution to the median nerve. The continuation of the subclavian artery into the axillary artery is also seen running medially to the lateral cord.
Retraction of Vein Structures
Slide 27 demonstrates better dissection distally. This dissection of the anatomy is evident upon retraction of the traversing branch of the axillary vein.
Lateral and Medial Cords
The clavicle is running transversely in the upper-right hand corner in Slide 28. In this slide, the lateral cord, the lateral cord contribution to the median nerve, the musculocutaneous nerve, and the other terminal branch of the lateral cord are also present. With further dissection between the lateral cord and the axillary artery, the medial cord is discovered. The ulnar nerve is yet to be dissected.
Dissection of Posterior Cord
In Slide 29, the lateral cord is elevated revealing the posteriorly situated posterior cord. The next step in dissection is to complete the dissection of the medial cord.
Dissection of Lateral and Medial Cords
The medial cord is gripped by the forceps, and its contribution to the median nerve is evident (Slide 30). The continuation of the median nerve into the ulnar nerve is also evident. The lateral cord, with its terminal branches contributing to the median nerve, continue on as the musculocutaneous nerve. The vessels in this specimen are running lateral to the plexus elements as opposed to running between the elements proper as in the standard plexus exposures.
Penrose Drains Around Cords
Penrose drains are used to mobilize the cord. Penrose drains are also used along the medial-most aspect of the dissection and next to the axial artery, around the medial cord, superficially near the clavicle, and along the deepest aspect of the dissection a Penrose drain envelopes the posterior cord (Slide 31). With a more standard position of the axillary artery and vein between the lateral and medial cords and the posterior cord, this dissection is much more challenging.
Wide View Showing Supraclavicular and Infraclavicular Plexus Dissection
Slide 32 shows a wide view of the skeletonized clavicle. The Penrose drains remain around the cords. Contributions from the anterior and posterior divisions of the upper, middle, and lower trunks and how they give rise to the lateral, medial, and posterior cords can be visualized. The next step in the dissection is the mobilization of the clavicle via dissection of the subclavius muscle and further dissection of the anterior and posterior divisions of the upper, middle, and lower trunk.
After completing the dissection of the supraclavicular and infraclavicular plexus elements, the next step is to mobilize the clavicle. To mobilize the clavicle and allow for superior and inferior retraction, the plexus elements must be dissected off of the underside of the clavicle and complete dissection of the subclavius muscle. In Slide 33, subclavius muscle is pulled down inferiorly under the clavicle. There are numerous large veins that bridge from the subclavius muscle to the subclavian vein. Care must be taken to dissect and ligate these veins to prevent inadvertent vascular injury.
Large Subclavius Vein
A large branch of the subclavian vein is running within the subclavius muscle (Slide 34). The subclavius muscle has been partially resected demonstrating the vein proper. This large branch of the subclavian vein is running into the subclavian proper just distal to the clavicle.
Injury to Subclavian Vein
Slides 35A and Slide 35B demonstrate the ease with which injury to the subclavian vein may occur. Avulsion of the subclavius vein may produce a defect within the subclavian vein, yielding significant intraoperative blood loss. Care must be taken during this stage of the dissection to ligate and divide veins running within and around the subclavius muscle to allow for safe dissection underneath the clavicle. The vein arises within the subclavius muscle running into the subclavian proper (Slide 35A) and avulsion of one of the veins of the subclavius muscle can yield a large proximal injury within the subclavian vein (Slide 35B).
Circumferential Dissection of the Clavicle
The subclavius muscle has been resected en totem (Slide 36). The venous channels arising within the subclavius muscle and running into the subclavian vein have been divided. A large hemostat is passed under the clavicle. Considerable mobilization of the clavicle can be obtained in operative specimens.
Mobilization of the Clavicle
Lap sponges have been passed under the clavicle. Lap sponges are usually attached to a large clamp and then used to pull the clavicle inferiorly and superiorly. Via mobilization of the clavicle, the anterior and posterior divisions of the brachial plexus trunks may be visualized (Slide 37). This circumferential dissection and mobilization of the clavicle allow for dissection of the remaining elements of the brachial plexus.
Divisions of the Upper Trunk
The next step in dissection is to visualize the anterior and posterior divisions of each trunk of the brachial plexus. The upper trunk in this specimen divides into three branches at the level of the clavicle. The suprascapular nerve runs superiorly and heads posteriorly under the clavicle (Slide 38). The forceps are pressing down upon the anterior and posterior divisions of the upper trunk to allow for easy visualization of the suprascapular nerve.
Anterior and Posterior Divisions of the Upper Trunk
In Slide 39, the anterior and posterior divisions of the upper trunk are coming into view at the level of the clavicle. The forceps are pulling down upon the posterior division of the upper trunk. The anterior division of the upper trunk is running between the suprascapular nerve and the posterior division. The anterior divisions of the upper and middle trunk combine to form the lateral cord. The posterior division of the upper trunk combines with posterior divisions from the middle and lower trunk to form the posterior cord.
Divisions of the Middle Trunk
Moving further inferiorly are the anterior and posterior divisions of the middle trunk. The anterior divisions of both upper and middle trunks give rise to the lateral cord. The lateral cord is formed in the operative specimen just deep to the clavicle. The posterior division of the middle trunk combines with the other two posterior trunk divisions to form the posterior cord (Slide 40).
Lower Trunk Divisions
The anterior and posterior divisions of the lower trunk are evidenced in Slide 41. The anterior division of the lower trunk is grasped with the forceps. The posterior division of the lower trunk is heading medially and deep to form the posterior cord. Just underneath and deep to the forceps, the subclavian artery is seen. At this point, all three trunks of the anterior and posterior divisions have been dissected.
Infraclavicular Plexus Overview
Slide 42 is a wider shot of the infraclavicular brachial plexus. The forceps are resting upon the lateral cord, which arises from the anterior divisions of the upper and middle trunk. The lateral cord courses distally and gives rise to the musculocutaneous nerve and the lateral cord contribution to the median nerve. Just medial to the lateral cord is the medial cord, and medial to the medial cord lies the axillary artery and vein. In this operative specimen, the axillary artery and vein are running medial to the plexus elements as opposed to between the lateral, medial, and posterior cords as in most specimens.
Terminal Branches of the Lateral Cord
In Slide 43, the terminal branches of the lateral cord are present. The forceps are resting upon the musculocutaneous nerve. The contribution arising from the lateral cord and going to the median nerve as seen in the midportion of this image are also visible. Tracking posteriorly from the median nerve is the contribution from the medial cord.
Medial Cord Contributions to the Medial Nerve
The forceps are grasping the contribution from the medial cord to the median nerve (Slide 44). Completing the "M" of the lateral and medial cords is the ulnar nerve.
Completing the "M" of the lateral and medial cords is the ulnar nerve (Slide 45). In this specimen, the ulnar nerve rises proximally along the course of the medial cord. Progressing from lateral to medial is the musculocutaneous nerve, the lateral cord contribution to the median nerve, the median nerve, the medial cord contribution to the median nerve, and the ulnar nerve. These structures form the terminal branches of the lateral and medial cord.
Posterior Cord Terminal Branches
The lateral cord is retracted medially to allow for easy visualization of posterior cord structures (Slide 46). It is of note that the axillary artery and vein in a standard dissection also overlie the posterior cord and add an additional level of complexity to the intraoperative dissection. The more medial orientation of these vessels in this specimen simplifies the dissection. The posterior cord runs deep to the medial and lateral cords. The posterior cords terminal divisions, the axillary nerve, and radial nerve can be faintly seen distally.
Completion of Dissection of Posterior Cord Terminal Branches
This completes the distal-most dissection of the posterior cord. The forceps are applying traction upon the lateral cord and considerable traction upon the musculocutaneous nerve to allow for visualization of the radial nerve. The larger of the two terminal branches of the posterior cord and the axillary nerve is held by the forceps (Slide 47). The axillary nerve is posterior and deep. This completes our dissection of the supraclavicular and infraclavicular brachial plexus and of the terminal branches of the posterior cord.