Keywords
plastic surgery - robotic surgery - brachial plexus
The brachial plexus is a complex network of nerves from the cervical and thoracic spinal cord that provide motor and sensory innervation to the upper extremity. Given the multitude of interwoven connections between the nerves from the root to the nerve level, lesions to nerves in this plexus present with varying degrees of sensory and motor deficits depending on the location and mechanism of injury.[1] Injuries can occur secondary to trauma, compression by adjacent tissues, and inflammation, and can severely affect the patient's quality of life.[2] Treatment of these injuries requires a multidisciplinary approach with cooperation from numerous different medical and surgical specialties.[3]
Management of closed injuries includes observation and serial examinations for 3 to 6 months as current limitations in imaging do not always allow for precise identification of the type and location of the nerve lesion.[1]
[4] Patients who do not have a resolution of their symptoms require surgical exploration and reconstruction. However, the complex anatomy often makes reconstruction extremely difficult, requiring the surgeon to pinpoint the origin of the injured nerve and match it to its appropriate target in a relatively confined anatomical space.[1] These operations traditionally require wide exposure via large incisions and extensive dissection to establish the correct anatomical pathways, posing some risk of damage to surrounding structures. While scarring from these procedures makes reoperation extremely difficult, delays to surgical intervention also result in extensive scar formation at the nerve lesion, which may necessitate nerve grafting.
One potential solution to these problems has been attempted through the use of minimally invasive techniques and endoscopic approaches.[5]
[6] Although an endoscopic approach would seemingly obviate the need to wait for surgical exploration and reduce the extensive scarring associated with open surgery, it does not allow for fine motor capabilities and magnification required for microsurgical nerve repairs.[7] More recently, robot-assisted brachial plexus surgery has surfaced as another proposed solution to combine the minimally invasive techniques of endoscopic approaches with the potential microsurgical capabilities offered by robotics.[8]
[9]
Despite a substantial increase in the use of robotics in other surgical subspecialties, application in plastic and reconstructive surgery has been relatively slow, gradually increasing over the last decade.[10] Use of robotic systems within the field of brachial plexus surgery has not had the same emphasis as other areas of plastic and reconstructive surgery.[11] However, to appreciate the rationale behind this slow uptake and to recognize the potential of future applications of robot-assisted brachial plexus surgery, it is important to understand the complex evolution of brachial plexus surgery.
Historical Perspective
Some of the oldest diagnoses and treatments of brachial plexus injuries can be dated back to the second century AD.[12] One of the earliest was from the Roman physician Galen, who attributed sensory deficits in a Persian sophist's hand to spinal cord inflammation from a traumatic shoulder injury, a diagnosis for which he recommended conservative management and immobilization.[12]
[13] Despite this early characterization by Galen, true advances in the anatomical characterization of the brachial plexus injuries did not occur until the second half of the 19th century.[12] During this time, physicians such as Duchene, Klumpke, and Erb, among others, began to describe and isolate the specific nerve lesions associated with various palsies of the upper extremity.[12]
[14]
[15]
[16] These advancements coincided with other groundbreaking strides in nerve surgery: Nelaton and Laugier performing the first successful nerve sutures in 1863 and 1864, respectively, Phillipeaux and Vulpan's experimental use of nerve grafts in 1870, and Eduard Albert's publication of the first successful clinical nerve graft in 1885.[12]
[17]
[18]
[19]
[20] These surgeons ushered in a new era for the exploration of brachial plexus reconstruction.
Ultimately, the first published description of surgical exploration and repair of a brachial plexus injury can be attributed to William Thorburn in 1900 with his case description of a surgical resection of a neuroma involving the entire plexus, and subsequent direct nerve repair.[21] Although the patient improved minimally, this publication, and the emergence of more novel techniques for nerve repair, resulted in an expanse of studies exploring both adult and obstetrical brachial palsies.[12]
[22]
[23]
[24]
[25] While surgical repair of obstetrical palsies was met with extremely promising results and interest continued to bloom, surgical repair of adult brachial palsies was still widely regarded as hopeless and interest in this area stagnated.
Although the First World War spurred a slight interest in this subject, it was not until the Second World War that interest in the surgical repair of adult brachial plexus injuries would renew with the same fervor that it had initially.[12] Particularly, the large number of penetrating and traumatic brachial plexus injuries combined with novel advancements in diagnostic technology, such as the electromyogram and recording of nerve action potentials through skin, provided ample opportunity to study and to try to correct these injuries once again.[26]
[27] Results of these studies yielded discouraging results, and surgical recommendations were limited to the most severe cases of brachial plexus palsies.[28]
[29]
Fortunately, major advancements came with the evolution of microsurgery in the 1960s.[12] The development of the operating microscope and microsurgical suture materials once again peaked interest in brachial plexus surgery. Techniques pioneered by Millesi and Narakas were adopted by surgeons worldwide, this time with substantially more favorable results.[12]
[30]
[31]
[32] Yet, even with the progress that has been made, brachial plexus repair still presents as a complex reconstructive challenge, particularly in the cases with root avulsion, and nonsurgical treatment is often still strikingly similar to that which was recommended by the Roman physician, Galen, in the second century.[7]
[33] Although the exploration of surgical reconstructive options has been limited, reconstructive techniques and diagnostic technology have continued to evolve, leaving the field of brachial plexus surgery primed for a new era of growth.
Anatomical Considerations
Anatomical Considerations
The brachial plexus is classically divided into five segments as it follows its anatomical course from the nerve root to the terminal branches.[2] The roots are formed from the ventral rami of the lower four cervical spinal nerves and the first thoracic spinal nerve (C5–T1). They travel from the posterior triangle of the neck and pass between the anterior and middle scalene muscles to form the upper (C5–C6), middle (C7), and lower (C8–T1) trunks. After the trunks pass beneath the clavicle, they divide into anterior and posterior divisions. The anterior divisions of the upper and middle trunks then re-form as the lateral cord; anterior divisions from the lower trunk re-form as the medial cord and all three posterior divisions as the posterior cord. Of note, the cords are named for their positions relative to the axillary artery in the infraclavicular region. The terminal branches then extend from the cords and into the distal upper extremity. The ulnar nerve (C8–T1) is a terminal branch of the medial cord; the median nerve (C6–T1) is formed from the medial root of the medial cord and the lateral root of the lateral cord; the axillary nerve (C5–C6) and radial nerve (C5–T1) are terminal branches of the posterior cord; and the musculocutaneous nerve (C5–C7) is a terminal branch of the lateral cord.[34]
Although this simplified description does not account for the various nerves branching from earlier divisions of the plexus, they must also be taken into account when considering the etiologies of brachial plexus injuries. [Table 1] provides a functional overview of commonly involved nerves and their associated functions.
Table 1
Functional overview of nerve branches frequently involved in brachial plexus injuries
|
Nerve branch
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Muscle innervation
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Motor and sensory functions
|
|
Dorsal scapular nerve (C5)
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Levator scapulae, and major and minor rhomboids
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• Retraction and elevation of the scapula
|
|
Long thoracic nerve (C5–C7)
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Serratus anterior
|
• Protraction and elevation of the scapula
|
|
Suprascapular nerve (C5–C6)
|
Supraspinatus and infraspinatus
|
• External rotation of the shoulder
• Abduction of the arm
|
|
Lateral pectoral nerve (C5–C7)
|
Pectoralis major
|
• Flexion, adduction, and medial rotation of the humerus
|
|
Upper and lower subscapular nerve (C5–C6)
|
Subscapular (both) and teres major (lower)
|
• Internal rotation of the shoulder and humerus
• Depression and abduction of the scapula
|
|
Thoracodorsal nerve (C6–C8)
|
Latissimus dorsi
|
• Adduction, internal rotation, and extension of the shoulder
|
|
Musculocutaneous nerve (C5–C7)
|
Brachialis, coracobrachialis, and biceps brachii
|
• Flexion of the elbow
• Adduction of the shoulder
• Supination of the forearm
• Sensation to the lateral forearm
|
|
Median nerve (C5–T1)
|
Pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis, flexor digitorum profundus (I and II), first and second lumbricals, opponens pollicis, abductor pollicis brevis, superficial head of the flexor pollicis brevis
|
• Flexion of the digits
• Flexion, abduction, opposition, and extension of the thumb
• Sensation to the palmar side and dorsal tips of the lateral three and half digits, thenar eminence, and lateral palmar side of the hand
|
|
Axillary nerve (C5–C6)
|
Deltoid and teres minor
|
• Abduction, flexion, extension, and external rotation of the shoulder
• Sensation to the upper arm
|
|
Radial nerve (C5–T1)
|
Triceps brachii, anconeus, brachioradialis, extensor carpi radialis longus and brevis, supinator, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, extensor pollicis longus and brevis, extensor indicis, and abductor pollicis longus
|
• Extension of the forearm, wrist, and digits
• Sensation to the lateral and posterior forearm, lateral dorsum of the hand, and lateral three and half digits
|
|
Ulnar nerve (C8–T1)
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Flexor carpi ulnaris, flexor digitorum profundus (III and IV), opponens digiti minimi, abductor digiti minimi, flexor digiti minimi brevis, adductor pollicis, third and fourth lumbricals, dorsal and palmar interossei, palmaris brevis, and deep head of the flexor pollicis brevis
|
• Flexion of the wrist
• Sensation to the medial dorsal and palmar hand, and medial one-half digits
|
Etiology
Injury to the brachial plexus results in loss of motor function and sensation to the areas innervated by the damaged nerves. However, injuries to the plexus often involve multiple nervous structures and make localization of the lesion substantially more difficult.[2] Thus, the mechanism of injury may provide unique insight into the etiology of brachial plexus injuries. In traction injuries, traction in the cephalad direction often results in damage to the lower plexus, while downward traction often results in damage to the upper root and trunks. High-energy trauma resulting in fractures of the humerus or dislocations are more likely to cause root avulsions, while milder trauma to these regions may cause a temporary palsy.[2]
[4]
[35] Additional mechanisms of injury include crushing injuries, compression by adjacent tissues, and inflammation of the nervous structures.[2]
[7]
These injuries can occur independently or in conjunction with one another, resulting in a myriad of presentations and localizing symptoms. A thorough history and physical and neurologic examination are critical in determining the etiology and location of the lesion, and imaging with X-ray, computed tomography (CT), or magnetic resonance imaging (MRI) may offer additional information about the nerve lesions and extent of damage to the surrounding tissues.[2]
[4] Two to 3 weeks after initial injury, electromyographic studies can be used to measure the progression of nerve recovery. Unfortunately, many patients do not improve over time and ultimately require surgical repair of their brachial plexus injuries.[3]
[4]
[33]
Surgical Repair
Current indications for surgical repair of brachial plexus injuries and reconstruction options are outlined in [Fig. 1].[7] As previously described, traditional surgical repair requires large incisions and extensive dissection of the regions surrounding the brachial plexus to allow for microsurgical repairs of the damaged nervous structures. Although attempts have been made to conduct these surgeries endoscopically, the decreased dexterity and visualization makes successful minimally invasive nerve surgery extremely difficult.[6]
[7]
Fig. 1 Indications for surgical repair of brachial plexus injuries with options for reconstruction
In recent years, robot-assisted surgical techniques commonly utilized for pelvic and abdominal procedures have seen increased utility in plastic and reconstructive surgery.[36]
[37] Although the minimal utilization of endoscopic procedures in this field has resulted in slower adoption than other fields, the potential advantages these systems can provide to reconstructive procedures have led to the exploration of their utility in transoral surgery, muscle flap harvesting, microsurgery, limb reconstruction, and peripheral nerve surgery.[11]
[38]
[39] Although, the adoption of robot-assisted brachial plexus surgery has progressed even more slowly than many other fields of plastic and reconstructive surgery, various surgeons have begun to publish their respective experiences with this technology.
Feasibility Studies
Some of the earliest studies describing the feasibility of the da Vinci Surgical Robotic System (Intuitive Surgical, Sunnyvale, CA) in brachial plexus surgery were published by Drs. Phillipe Livernoux, Stacy Berner, and Gustavo Mantovani between 2009 and 2011. As previously stated by Facca et al, robotic-assisted surgery of the brachial plexus has evolved inversely to endoscopy, by initially focusing on peripheral nerve reconstruction and extending into minimally invasive approaches.[1] Several of these early studies used animal models to demonstrate the feasibility of the epineural and neurotrophic repairs, and nerve harvesting techniques for use in brachial plexus repair.[8]
[40]
[41]
[Table 2] outlines the current published literature focusing on robot-assisted brachial plexus repair in human cadavers and subjects.
Table 2
Current publications of robot-assisted brachial plexus surgery
|
Study
|
Study type
|
Procedures
|
Key findings
|
|
Manatovi et al
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Human cadaver
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Robot-assisted endoscopic dissection and exploration of supraclavicular brachial plexus with nerve graft repair of artificial lesion to the upper trunk
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Endoscopic repair of supraclavicular brachial plexus is feasible with exclusive use of the robot. No macroscopic evidence of damage to nerves or surrounding structures
|
|
Lequint et al.[43]
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Case report (N = 1)
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Minimally invasive robot-assisted biopsy of intraneural perineurioma in the right superior trunk of the brachial plexus
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The patient had better cosmesis and decreased scarring without sensory or motor deficits postoperatively. Lack of sensory feedback was not a problem, but nerve biopsy was unable to be confirmed without electrical stimulation
|
|
Garcia et al[9]
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Human cadaver and case series (n = 3)
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Open dissection of the brachial plexus and robot-assisted microsurgical repair of the brachial plexus in cadaver and then in human subjects
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Tremor filtration, motion scaling, and ergonomic positioning allowed for successful repair in all subjects; however, lack of adequate instrumentation was noted
|
|
Berner et al[42]
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Case series (N = 12)
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Minimally invasive robot-assisted dissection and repair of the brachial plexus
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Microsurgical repair of nerves achieved; however, it needed to be converted to open in 9 of 12 cases. Reasons for conversion included inability to maintain insufflation of resection cavity, unsuited instrumentation, blurring of stereoscopic vision, and difficulties with visual identification of anatomical landmarks
|
|
Facca et al[1]
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Human cadaver and case series (n = 8)
|
Open incision with robot-assisted microsurgical dissection and repair of the brachial plexus in cadavers and then in human subjects (repair of two complete brachial plexus palsies, three partial C5–C6, two continuous axillary nerve lesions, and one axillary and musculocutaneous nerve lesion
|
Confirmed the ability to perform dissection and microneural repair robotically, but inadequate instrumentation prevented minimally invasive and microsurgical techniques
|
|
Tetik et al[44]
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Human cadaver
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Open incision and initial blunt dissection of the infraclavicular space with robot-assisted dissection of the lower trunk of the brachial plexus
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Easier exposure and more ergonomic positioning with wider range of motion for robotic arms than the traditional supraclavicular approach
|
|
Jiang et al[45]
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Human cadaver
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Endoscopic dissection of the paravertebral C7 nerve root and contralateral nerve transfer using minimally invasive, robot-assisted technique
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This technique allowed for use of smaller incision and nerve graft compared with the traditional open surgery
|
One of the earliest cadaver studies, published by Manatovi et al in 2011, demonstrated the feasibility of the exclusive use of the da Vinci robot for both endoscopic dissection and microsurgical nerve repair, providing the framework for further attempts in human populations. These later studies, published between 2012 and 2014, attempted either open incisions with robot-assisted dissection and microsurgical repair of the brachial plexus or robot-assisted endoscopic dissection and repair of the brachial plexus, often practicing initial technique on a human cadaver before transitioning to human subjects.[9]
[42]
[43] The cadaver studies published by Tetik and Uzun[44] and Jiang et al[45] in 2014 and 2016, respectively, demonstrated the feasibility of alternative uses of the robotic systems with infraclavicular and paravertebral approaches to brachial plexus repair. Although sparse, these studies demonstrated many of the key advantages of robot-assisted brachial plexus surgery and addressed many of the current limitations preventing their widespread adoption.
Advantages
Many of the advantages demonstrated in these studies are the basis for the widespread adoption in numerous other surgical specialties; however, these advantages also provide specific benefit to brachial plexus surgery and microsurgical nerve repair. Specifically, the reduction of physiologic tremor, 3D visualization of anatomical structures, and ergonomic positioning allow for increased surgical dexterity within the confined anatomical spaces of the brachial plexus.[1] The ability to perform minimally invasive microsurgical procedures exclusively with robotic systems, as demonstrated by Lequint et al and Berner et al, results in decreased scar formation, which is a primary motivation for implementing minimally invasive brachial plexus repair.[5]
[6]
[42]
[43] Although long-term outcomes have not been demonstrated in the current literature, the authors of these early studies posit that the potential benefits of these novel techniques allow for earlier exploration, diagnosis, and intervention compared with the traditional approaches.[9]
[39]
[42]
Limitations and Future Directions
Limitations and Future Directions
Currently, robot-assisted brachial plexus surgery is not without significant limitations. The above-mentioned studies demonstrate the same constraints that have continued to limit the expansion of robotic-assisted surgery into the field of plastic and reconstructive surgery. Specifically, inadequate instrumentation has been consistently cited as the major restricting factor.[7]
[9]
[10]
[42]
[44] To date, there is no comprehensive set of microsurgical instruments designed for use in the da Vinci systems. The authors consistently noted that the instruments were too large to manipulate the delicate tissue and nerves in the brachial plexus and that the optics of the robot-systems did not allow for proper visualization and identification of anatomical structures.[1]
[10]
[42] Additionally, Lequint et al noted that the lack of a nerve stimulator compatible with these robotic systems makes confirming the identity of structures within the brachial plexus significantly more difficult.[43]
The continued evolution of robot-assisted brachial plexus surgery is largely dependent on the development of instrumentation specific to microsurgery and nerve surgery. Although there is currently no comprehensive set of microsurgical instruments for the da Vinci robot, the increased utilization of these systems for microsurgery has led to the development of novel microsurgical software and tools adapted to the robotic console.[11] These include the addition of enhanced optics, confocal microscopy, CO2 laser dissection, and various other tools designed to facilitate complex microsurgical procedures.[46] These advancements provide new and promising methods to optimize the use of robotic systems in brachial plexus surgery. Continued refinement of procedural steps and adaption of additional microsurgical tools will allow for novel approaches to procedures that previously were limited by this lack of instrumentation.[1]
[44]
There are various additional limitations to consider that are less significant to the feasibility of robot-assisted brachial plexus surgery. Some authors noted technical difficulties such as fogging of camera lenses, inability to maintain insufflation, and small working spaces making navigation difficult.[1]
[42] As demonstrated within the case series conducted by Berner,[42] many of the technical difficulties experienced by these surgeons during the endoscopic approach do not require substantial technological advancements. Instead, they require increased case volume to overcome the learning curve associated with robotic systems and optimize their technique with this approach.
Although the feasibility of these procedures has been demonstrated by these initial studies, there are limited data available concerning the hospital costs, length of operation, and outcomes associated with long-term utilization of robot-assisted systems in larger cohorts of patients. While cost and operating time have also been voiced as initial concerns, longitudinal studies are necessary to see if the same benefits that have led to the widespread adoption of robot-assisted surgery in other specialties remain applicable to brachial plexus surgery.[10]
Conclusion
The complex anatomy of the brachial plexus provides a unique challenge to the reconstructive surgeon. Although historical management favored a more conservative approach, the evolution of surgical techniques and diagnostic technology has resulted in renewed interest in surgical correction of these nerve lesions. Recently, the birth of robot-assisted surgery and consequent study in brachial plexus surgery has demonstrated the feasibility of this approach versus the traditional open surgery. Development of instrumentation specific to these endoscopic and microsurgical procedures will potentially allow for more acute intervention without prohibitive scar formation interfering with future surgeries. However, large longitudinal studies outlining long-term costs, changes in operating time, and functional outcomes are required before the decision to use robotic systems in brachial plexus surgery can be made.
