Representation of the arthroscopic anatomy of the shoulder divided into anterior, superior and posterior compartments
The anterior, the inferior shoulder, and the posterosuperior shoulder.
Each one of these compartments has a certain amount of nerves that should be expected, and seeked when working in this space.
The anterior compartment contains the Cords and the distal divisions of the brachial plexus (Musculocutaneous, median, ulnar, radial nerves).
The posterosuperior compartment regroups the SupraScapular nerve (SSN), and the Trunks (superior middle and inferior).
The inferior compartment contains the axillary nerve and the branches to the long head of the triceps from the radial nerve.
14.3 Types of Complications
14.3.1 Expected and Less Expected Complications
As soon as the surgery is performed out of the limits of the joint, it becomes risky for the nerves. This principle is widely accepted and most surgeons prefer to remain inside the joint to prevent neurologic complications.
However, it remains possible to damage nerves during exclusively arthroscopic procedures. Particularly the axillary nerve and the SSN.
The main risk for the axillary nerve is related to its proximity with the inferior capsule.
During Bankart procedures, the inferior suture, if tighten too widely after grabbing too much capsular tissue is at risk of transecting the axillary nerve and damaging it.
During SLAP repair procedures, an ancre placed too high and through the coracoid notch might damage the SSN.
Therefore again, it is tremendously important to always keep in mind the anatomy and take care of the surrounding nerves even though they might be considered as protected during the procedures.
14.3.2 Non-Surgical Complications
The set-up of the patient can be a great source of complications around the nerves.
The literature has described palsy in almost all peripheral nerve territory after the set up was neglected, particularly at the lower limb and the ulnar nerve with compression points.
However, we recently faced a severe complication caused by the set up in beach chair and a compression of the cranial nerves at the neck.
The 9th, 10th and 12th cranial nerve pairs were compressed and paralyzed during a beach chair position set up with a stabilizing strapping around the head of the patient, who woke up with a palsy of the tong, and suffering dysphonia and dysphagia.
Those symptoms spontaneously recovered within the first 2 months.
The first emergency to look for in such a situation is a basilar trunk stroke. Therefore an Angio MRI should be performed in emergency.
An MRI of the cervical spine should shortly be made in order to eliminate decompensation of peripheral nerve tumors.
When the paraclinical examination is normal, the diagnose is clinical and confirmed by the ENT physicians. It is most likely the compression of the cranial nerves at the neck while the surgery was performed in a beach chair position, by the strapping of the head.
However such symptoms have also been described following a wrong management of the intubation and air management by the anesthesiology team and is called the Tapia’s syndrome [1, 2].
This rare complication reminds us not only of the importance of positioning during anesthesia and surgery, but also of the need for careful and correct airway management. It could be probably prevented by careful insertion of an appropriate size LMA, and the use of low intracuff pressures and/or volumes.
Anesthesiology complications are also described regarding loco regional anesthesia.
Cases of intraneural injections have been described, causing severe damage to any nerves in the area where the block was made.
The typical presentation is a neurological pain and weakness in the territory of the SSN, that can be extended to the upper trunk territory after an interscalenic block.
Patient suffers from pain for many months, which resigns and leaves a permanent weakness and atrophy. Electromyographic studies are not very specific but show an absence of complete nerve block, and only an increase of latencies.
After a few months an MRI can be performed and will show signs of scaring within the nerve.
It is not yet perfectly well defined if the best solution is to leave the situation to spontaneous healing, or perform an intraneural neurolysis in order to remove the scar tissue and provide better and faster healing.
This situation has also been described in axillary blocks, with symptoms in the median and ulnar nerve.
14.3.3 Positioning Complications
The patients set up, may lead to several nerve complications.
The main injuries occurring because of the set up are traction or compression injuries.
Either beach chair or lateral decubitus can be responsible for nerve injuries when associated to a simple traction or an arm holder.
The traction aiming mostly inferiorly, produces a stretch on the superior trunk and on the musculocutaneous nerve [3]. Though mostly transitory, traction injuries due to positioning of the patient may occur if the weigh put on the arm is too heavy, or during certain steps of the procedures [4].
Traction injuries to the cervical brachial plexus have been described as well, with permanent lesion of the auricular branches of C5.
14.3.4 Surgical Complication
Working in the anterior space of the shoulder outside of the joint is more frequent in many shoulder surgeons’ practice. Procedures such as arthrolysis, massive subscapularis tears, Latarjet procedures, and revisions, lead to working in a space close to the brachial plexus and its division branches.
Therefore, not knowing exactly during some steps of the procedures where the nerves stand, put them at risk.
Examples of axillary and musculocutaneous nerve palsies occur even in experienced surgeons’ hands.
Working in the posterosuperior area of the shoulder, far from the limit of the joints (i.e. rotator cuff release) may lead to SSN damage particularly at the spinoglenoid notch.
As described previously, the inferior shoulder is an area where very few procedures occur exept for the stabilization procedure such as Bankarts with a need of a very inferior reattachment of the labrum. The axillary nerve is there again at risk.
Mechanism of the lesion is frequently clean cuts in case of surgical mistakes, but also hot water burns with the use of radio frequency around nerves. During arthroscopic procedures, compression injuries secondary to retractor placement are less frequent.
14.4 Paraclinical Investigations
We now tend to preform MRI of the brachial plexus with a specific protocol targeting the nerves, in order to visualize the level of the lesion.
It is possible to localize the area of the damage on the nerve, and we can determine if the nerve is still in continuity or if there is a rupture or a fresh cut.
MRI representation of the denervation oedema of the deltoid, following an axillary nerve injury. This sagittal reconstruction also shows a denervation oedema of the Teres minor, indicating a lesion of the nerve proximal to the division of the axillary nerve into its anterior and posterior branches innervating respectively the deltoid and the Teres minor
There isn’t any real interest in performing an electromyographic study before 3 weeks. The surgeon must specifically ask for the study of every nerve suspected of palsy, and also ask the neurologist if the lesion is proximal or distal. It is possible to determine if the nerve is still in continuity, functionally or anatomically speaking, and therefore to precise the prognosis of recovery.
The interest of the EMG study is also to help follow the recovery, and decide to perform a surgery when it is to slow, and incomplete.
14.5 Management
14.5.1 Nerve Injuries and Management
In this chapter we describe the most common nerve injuries, their clinical consequences, the hypothetical surgical situations at risk of creating such a trauma, and the expected management of this situation.
14.5.2 General Management of Nerves During Shoulder Arthroscopy
The best way to avoid nerve damages during shoulder arthroscopy is to either remain in a space where there is no risk (i.e. glenohumeral joint laterally to the glenoid, anterior shoulder, laterally to the conjoint tendon, above the inferior limit of the subscapularis). In any other situation, we recommend to be able to dissect around the nerve and identify the location of the nerve in order to visualize it and protect it.
Recently described advanced arthroscopic procedures such as arthroscopic Latarjet, can be harmful to the brachial plexus and the axillary nerve. When the nerve is visualized, it can be protected, and surgeons should not perform this procedure if afraid of identifying it. For the same reasons, Latissimus dorsi transfers passed arthroscopically through the posterior space, between the deltoid and the posterior cuff may threaten the axillary nerve. Therefore, the long head of the triceps and the posterior part of the nerves must be strictly dissected and identified before passing the transfer.
The management of a nerve palsy requires to be initially conservative, and to follow the potential recovery. The pattern of the palsy, allows to identify most frequently the level of the lesion. Associated palsies will indicate cords or trunks lesions, and isolated muscle palsy will orientate rather toward a distal branches lesion.
The association of a sensitory and motor deficit, is in favor of a severe lesion and a potential risk of no recovery. On the other hand, when the deficit is only motor, without any sensitory deficit, the chances of recovery are good.
During the follow up, an EMG should be performed between 3 and 6 weeks. It enables to verify the absence of complete transient lesion of the nerves. However, the interpretation of the EMG cannot stand alone in the therapeutic decision.
We recommend that if any doubt exists at 3 weeks post op, a surgical exploration should be performed. It seems reasonable to contact specialized peripheral nerve surgeons for this step of the management, and if one is not confident into dealing with nerve exploration, the patient should be referred.
14.5.3 Conservative Treatment
In most of the cases the recovery is complete, but it should be fast. The common attitude is to wait for six months until there is a recovery of the palsy and perform surgery if it doesn’t happen. We believe that the “wait and see” attitude should be shorter since an early exploration of the nerve enables an identification and most frequently a direct suture of the nerve when possible.
14.5.4 Suprascapular Nerve
Any procedure taking place in the area of the coracoid and spinoglenoid notch put the SSN at risk.
Few surgeons work around the coracoid notch, except for those who perform SSN release. During SSN release, the Supra spinatus must not be retracted too much posteriorly to expose the nerve, since distal lesion can occur to the branches penetrating the muscle at the level of the coracoid notch.
Drawings on the shoulder of a patient suffering from a distal SSN and axillary nerve lesion, requiring a posterior approach for a transfer from the Spinal accessory nerve to the SSN and the long head of the triceps motor branch to the anterior branch of the deltoid
The spinoglenoid notch is frequently approached during arthroscopic procedures. Wide release of the supra – and infraspinatus at the spine in massive cuff tears, can cause SSN lesions.
On the articular side, any procedure approaching the superior labrum can be responsible for iatrogenic injuries to the SSN. The release of the labrum, and the debridement of the bone is frequently a source of nerve lesion, along with drilling and anchors placements [5, 6].
Lesions to the SSN are also observed in cases of too long and ascending latarjet screws, or with ancres misplaced ayt the superior part of the glenoid during SLAP repair. The management of a severe lesion of the SSN at the coracoid or glenoid notch is possible with nerve procedures, such as neurolysis or nerve transfers when addressed soon enough.
However, in case a nerve transfer is needed, the lesion is frequently too distal to be addressed by a proximal and classic Spinal accessory nerve transfer. The approach must be posterior and enable an end to end anastomosis distally to the coracoid or glenoid notch, using either the Spinal accessory nerve or the dorsal scapular nerve (Fig. 14.3) [7–10].
When nerve procedures are no longer available, the palliative techniques include lower trapezius transfer to reanimate external rotation, and Latissimus dorsi transfer to reanimate forward elevation. Those transfers have a good functional outcome as long as the deltoid is still efficient [11].
14.5.5 Musculocutaneous Nerve
A musculocutaneous nerve palsy can occur particularly while surgery is performed in the anterior space of the shoulder.
Many cases of lesions are described during Latarjet procedures. Even if the nerve is visualized and protected, traction injuries can be responsible for elbow flexion palsies.
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