Chapter13. Nerve Entrapment

Publicado em: 15 de maio de 2020 por Dr. José Carlos Garcia Jr.
Categorias: Capítulos de Livros


Telemicrosurgery: RAMSES, chapter 13.,2013, pp 109-117 Springer Paris

 DOI 10.1007/978-2-8178-0391-3_13

Print ISBN 978-2-8178-0390-6

Online ISBN 978-2-8178-0391-3

16.1 Introduction:

This chapter is designed to demonstrate the anatomical and functional causes of nerve entrapment in upper limb and its possible surgical treatments. The robotic, endoscopic and open treatment of nerve entrapment syndromes will be presented. The surgeon needs to understand and recognize the anatomical considerations and variations in the common locations of nerve compressions.

Knowing these entrapment syndromes, the surgeon will be able to access the correct surgical site. Robotic assisted surgery is already available as a treatment for some of these conditions, and as the field develops, more robotic solutions will be available for these common problems.

16.2 General Considerations:

Patients with nerve entrapment syndromes often have concomitant neurologic conditions, and surgeons caring for such patients must be aware of them.

Some factors that may affect compression syndromes include:

1- Fructose and sorbitol substances increase the intra-fascicular pressure

2- Hereditary neuropathies

3- Acquired and congenital abnormalities (elbow varus-valgus)

4- Muscle hypertrophy in athletes

5- Repeated trauma

6 – Peripheral fibers are more susceptible to compression

7 – More myelin increases susceptibility when there is compression

8 – If the nerve has more fibers, the nerve will be more fragile.

9 – If the nerve has more connective tissue, it has lower compression risk

10 – Fractures

11 – Dislocations

12 – Presence of tumors and cysts

13 – Any increase in pressure around the nerve may cause venous congestion and circulatory compromise, affecting the nerve

In addition, the practice of reconstructive surgery carries a risk of iatrogenic injury and entrapment syndromes to neighboring neurologic structures. 

The knowledge of the most common sites for nerve lesion around the upper limb allows surgeons to better recognize these entities,asFamiliarity with the relevant neural anatomy will also help surgeons  to avoid potential neural injuries. 

Sometimes entrapment syndromes may cause weakness and pain, and nerve lesions may result in sensory and motor loss. 

Strength measurement is important in the neurologic evaluation of the patient, however sometimes it is possible to move structures using muscles with different innervation. The elbow, for example, can strongly flex with the action of the brachioradialis without having any function of the biceps and the brachialis. Some patients can abduct the shoulder through a full arc of motion by using either just the supraspinatus or the deltoid, in the face of complete paralysis of one or the other1. 

Since different nerves may have the same root, diminished  radial nerve function should alert the examiner to look closely at axillary nerve function, because they are both derived from the same cord(posterior). Similarly, loss of median nerve function that also affects the musculocutaneous nerve strongly suggests the lesion is at the level of the lateral cord.

One needs to evaluate patients for other conditions causing motor impairment besides those of a neurologic etiology. Certainly, the surgeon needs to consider that an inability to externally rotate the arm might represent a neurologic lesion, a suprascapular nerve entrapment affecting the rotator cuff, a rotator cuff tear, or any combination thereof. 

The surgeon must carefully evaluate the patient presenting with pain in the upper extremity from a cervical radiculopathy in the context of  motor weakness and sensory loss. In this situation, flexion and extension of the cervical spine or Spurling’s maneuver might reproduce or exacerbate the patient’s symptoms. Upper motor neuron lesions can also result in shoulder weakness. In these cases, the deep tendon reflexes may be hyperreflexic, pathologic reflexes may be present, and tone may be increased. 

Referred pain should also be excluded during the clinical examination. Cardiac and other intrathoracic as well as intra-abdominal complaints may be manifested as upper limb pain.

16.3 Entrapment sites: 

The specific structures and symptoms related to each nerve entrapment will be addressed in the following:

16.3.1 Musculocutaneous Nerve 

The lateral free margin of the biceps aponeurosis can exert a compression force  on the musculocutaneous nerve as the elbow extends. The nerve is caught between the biceps tendon and brachialis fascia causing pain in the lateral aspect of the forearm. This compression force can be markedly accentuated if the forearm is fully pronated.2

16.3.2 Axillary Nerve

The quadrilateral space syndrome has been described as a potential cause of posterior shoulder pain resulting from compression of the axillary nerve within the quadrilateral space. 

Fibrous bands 3,4 are one of the most commonly cited causes of compression of the contents of the quadrilateral space.  

16.3.3 Suprascapular Nerve

Suprascapular neuropathy can occur from a variety of causes, including:transverse scapular ligament anomalies,5compression from adjacent ganglia,6 abnormal osseous morphology of the suprascapular notch,7,8 traction injury,9repetitive or extreme shoulder motions, rotator cuff rupture,10,11 and trauma.12 Isolated nerve compression is a relatively rare phenomenon and, as such, is easily misdiagnosed.

16.3.4 Thoracic outlet syndrome

Thoracic outlet syndrome (TOS) is a generic name used to describe patients with neurovascular symptoms related to sites of compression of the brachial plexus or its accompanying vascular structures.13.

Predominantly neurological symptoms are involved in 92-95% of the cases, 14 and may arise in any of the following structures: anomalies of scalene muscle development or insertion (these include an enlarged scalenus anticus, enlarged scalenus medius, anomalous insertion of the muscles, overlapping insertion ofscalenus anticus and medius, or enlarged scalene tubercle), scalenus minimus, scalenus hipertrophy, cervical rib14, Sibson’s fascia, clavicle (usually the sequela of fractures), compression within the coracopectoral space (or pectoralis minor syndrome), syndrome median (compression of the axillary artery between the bundles of the brachial plexus), Langer’s syndrome (compression of the neurovascular bundle by an anomalous muscle, the axillar-pectoralis), iatrogenic, traumatic, positional, residual fibrous band from an incomplete cervical rib,   anomaly of the subclavius tendon or tubercle of insertion, an anomaly not clearly identifiable as a developmental variation, or the absence of a clearly evident abnormality.15

The patient usually presents with paresthesia or nonspecific pain upon direct neurologic stimulation, or with a secondary reduction of muscles strength and loss of precision in coordination (most commonly in the rotator cuff). These symptoms may be exacerbated by direct stimulation or in specific maneuvers.  16,17

16.3.5 Spinal Accessory Nerve

The diagnosis may be suspected by trapezius atrophy and winging of the scapula, but is often missed, resulting in delayed treatment.18

Iatrogenic scar tissue is the most common nerve entrapment cause about the spinal accessory nerve due surgical dissection in the posterior triangle of the neck, such as for lymph node biopsy.

16.3.6 Long thoracic nerve

The causes of long thoracic nerve paralysis are diverse, ranging from acute or recurrent trauma to infections and surgical operations. In the majority of cases, the nerve lesion seems to be mechanical in origin.19-21

Spontaneous cases of entrapment at the scalenus medius may occur.22 

Overexertion, including athletic activities and thoracic outlet syndrome may be other causes.

This nerve injury is usually manifested as winging of the scapula(fig.1).

16.3.7 Dorsal scapular nerve

Because the nerve is usually trapped as it exits the lower two-thirds of the scalenus medius, neck rotation or extension may reproduce or exacerbate symptoms. The entrapment is caused by either a hypertonic scalenus medius, abnormal insertion of the scalenus medius into the first rib, or mechanical friction on the nerve.

16.3.8 Radial nerve

At the level of the lateral head of the triceps, the radial nerve may be compressed through the intermuscular septum23; however, the most common 4 structures that may compress the posterior interosseous nerve in the tunnel are the arcade of Frohse, the sharp tendinous margin of the ECRB, the fibrous bands anterior to the radial head, and the radial recurrent vessels24. Other causes of nerve entrapment are: adhesions at the distal aspect of the of the distal humerus, muscular anomalies, vascular aberrations, bursae, ganglions25, fibrotic bands proximally within the midportion or at the distal end of the supinator muscle26, inflammatory thickening and adherence of the extensor carpi radialis brevis27 tendinous origin to the proximal edge of the supinator in its radial side28, thrombotic recurrent radial vessels, and thickened proliferated rheumatoid synovium from the radiocapitellar joint29,30. 

 The painful condition associated with compression of the posterior interosseous nerve, is known  as radial tunnel syndrome, or resistant tennis elbow. 31,32.

If the patient shows just motor manifestations, it is termed posterior interosseous syndrome. 

At the level of the wrist, the sensory branch of the radial nerve can be compressed between the tendon of the brachioradialis and the extensor carpi radialis longus.

16.3.9 Ulnar Nerve

Common areas of compression are the arcade of Struthers, medial intermuscular septum, medial epicondyle, narrow cubital tunnel, arcade of Osbourn (fibroaponeurotic tissue connecting the humeral and ulnar heads of the flexor carpi ulnaris), and aponeurosis of the deep flexor and pronator teres; furthermore, during elbow flexion, traction forces on the ulnar nerve are major causes of increased intraneural pressure.33

The cubital tunnel changes from oval to flattened ellipse34, where flexion pressures within the tunnel may increase by seven times.35

For throwing athletes, the ulnar nerve compression can be enhanced since the pressures in the cubital tunnel increases up to six times over the resting position when the arm is placed in the cockiedthrowing postition. 

The ulnar nerve can also be compressed in Guyon’s canal in the wrist, between the pisiform bone and the hamate bone, under the pisohamate ligament.

16.3.10 Median Nerve

Carpal tunnel syndrome is the most common nerve entrapment syndrome of the median nerve, however several syndromes of more proximal entrapment have been described. These include entrapment at the ligament of Struthers, lacertus fibrosus36, heads of the pronator teres muscle, sublimis bridge of the flexor digitorum sublimis muscle, and of the anterior interosseous nerve 37. The surgeon must be cognizant of these, because such syndromes are rare and often confused with radiculopathy or carpal tunnel syndrome.

The pronator teres syndrome is often confused with carpal tunnel syndrome, and two conditions may occur simultaneously(double crush syndrome)23.

In cases of isolated motor symptoms, the anterior interosseous nerve syndrome (motor branch of the median nerve) is suspected38. This motor syndrome is seen as an isolated entity in a ratio of 1 to 40 with the pronator syndrome and these two conditions occasionally 39. 

Because of the Martin Gruber nerve anastomosis  (present between the ulnar and median nerves or ulnar and anterior interosseous nerves) distal nerve entrapment syndromes can present with mixed symptoms.

Anatomic variations causing impingement include  reduplicate [1]lacertus fibrosus, the Gantzer muscle, the palmaris profundus40, or flexor carpi radialis brevis40, vascular perforations, and tethers.

16.4 Treatment

16.4.1 Conservative Treatment

Conservative measures are sometimes effective and should be the first line treatment. 

Stretching, global postural re-education, medications that stimulate the synthesis of the myelin sheath and the neuronal cell membrane, muscle relaxants, anti-depressives and corticosteroids may all be used.

16.4.2 Open Surgical Treatment

Each part of the nerve has its own characteristics and knowledge of  anatomy and function should lead the surgeon locate the precise spot of nerve impingement.

If at surgical exploration the nerve appears intact but compressed by scar, neurolysis is indicated. If a neuroma in continuity is present, that does not conduct a nerve action potential41, resection of the neuroma and primary grafting should be considered. If a rupture or transection of the nerve is discovered, primary reapproximation or grafting are options.

 The neurolysis is accompanied by an excision of a triangular wedge of the biceps tendon overlying the nerve for musculocutaneous nerve(fig.2).

Surgical procedures include posterior exploration of the quadrilateral space and release of scar or fibrous bands to achieve decompression of the axillary nerve.3,4

For suprascapular nerve the open approach to release of the structures that compress the nerve are is technically difficult to perform.42

The surgical treatment of the thoracic outlet syndrome depends on the structures involved in the pathology. Resection of cervical rib, calvicular osteotomies and osteosynthesis for fractures or fracture sequelae, release of the pectoralis minor, scalenectomy(fig.3) and simple release are all surgical otions. Excellent and good results have been achieved in around 86% of these surgical procedures14.

The nerve release may be performed to remove scar tissue and neuromas for spinal accessory nerve entrapment, and grafting may be necessary. If the nerve presents complete lesions another options appear to achieve most  satisfactory outcomes.[2]

Surgical options are available for treating injury to the long thoracic nerve in the early stages. Some have favored neurolysis of the nerve with decompression at the level of the scalenus medius or scalenectomy.22 Another strategies is to perform neurotization (or nerve transfer) using one or two intercostal nerves, or the thoracodorsal nerve, or in late cases muscle transfer and scapula-thoracic fusion.43-45 

The dorsal scapular nerve may need scalenectomy of the scalenus medius and neurolysis in order to be decompressed.

For radial nerve the surgeon have to take special care in the region of the nerve division as well as the arcade of Frohse, where the nerve spreads out branches(fig.4).

The surgical treatment is the neurolysis and the release of the structures associated to the radial nerve compression.

For Watenberg Syndrome, the brachioradialis fascia is released by freeing the radial sensory nerve from distal to proximal. Any fibrous bands over the nerve distal to the brachioradialis fascia should also be released.

For Ulnar nerve the surgical options are neurolysis alone, neurolysis and anterior translocation of the ulnar nerve (subcutaneous or submuscle) or neurolysis, and epicondylectomy. 

In other conditions such as hypertrophied medial head of triceps (such as occurs in body builders), in the presence of the snapping triceps, the tardy ulnar palsy (a condition caused by the valgus’ elbow deformity and consequent nerve stretching) 46, hypermobility or subluxation of the nerve (congenital or due to previous trauma) the only surgical possibilities are epicondylectomy or anterior translocation of the ulnar nerve(subcutaneous or submuscular). An excision of a triangular wedge of the triceps tendon may be also necessary.

For anconeus epitrochlearis this anomalous muscle release is also necessary to liberate the ulnar nerve. When the ulnar nerve is compressed in Guyon’s canal in the wrist, the surgeon can release the pisohamate ligament.

The release of the Struthers ligament and supracondyloid process, lacertus fibrosus, bridge of the flexor digitorum sublimis muscle, teres pronator(fig.5), carpal tunnel or anomalous structures are all surgical options.

16.4.3 Endoscopic treatment

Endoscopic treatment for nerve release has been used successfully in many nerve entrapment syndromes such as the carpal tunnel, suprascapular and cubital tunnel. Endoscopic release of the ulnar nerve requires advanced endoscopic skillsand the surgeon must believethat anterior translocation is unnecessary47. 

The carpal tunnel endoscopic release is easy, fast and presents the advantages of a minimally invasive procedure48.

The suprascapular nerve release (fig.6) has a high rate successful outcomes, but demands a high level of arthroscopic/endoscopic expertise49,50. 

Cadaveric studies have also reported of brachial plexus endoscopic exploration. For live patients, endoscopic decompression for pectoralis minor syndrome(fig.7) and anterior axilary nerve release(fig.8) have been reported.

A major limit of endoscopic treatment is the two-dimensional view (absence of depth perception) The instruments are also limited, and need to have 3 degrees of freedom in order to better access some nerve entrapments sites.

Future improvement of endoscopic devices may expand indications for endoscopic release of nerve entrapment.

16.4.4 Robotic Treatment

The robotic telesurgical system consists of a three-dimensional stereoscopic vision system with three robotic slave [3]arms. The instruments have 3 degrees of freedom and are controlled by the surgeon from a console.   

If the surgeon has to perform a nerve graft  because neuroma, the tremor filtration is a very important advantage, allowing for robotic anastomosis of the nerve.

The techniques forusing endo-robotic (robotic endoscopic) surgery instead of open robotic surgery are still in development in cadaveric models. Our research suggests that in the near future, the surgeon will be able to decompress thoracic outlet syndrome, pronator teres syndrome, perform the anterior translocation of the ulnar nerve, as well as acubital tunnel release, all endorobotically.  

 We have successfully started endo-robotic procedures using novel port locations in cadaveric models, but these procedures are still experimental at this time51.

 For thoracic outlet syndrome we used anesthetic block landmarks in order to establish the portals. 

The first supraclavicular portal was made at the lateral border of the sternocleidomastoid muscle, approximately 5 cm above its point of insertion on the clavicle, and the second one just above the middle of the clavicle. 

For further procedures we are still studying the best choice of portal locations.

At this time, we are using open robotic surgery following the same steps of conventional open surgery mentioned above for some procedures in live patients (fig.9, 10 and 11). 

 Some endorobotic procedures, such as suprascapular nerve release, require new tools and different optical angles(30º and 70º) in order to be feasible.  Some procedures, such as the carpal tunnel syndrome are already feasible(fig.12) 52, but the open and endoscopic techniques are faster and cheaper.

In the near future, we will be able to better choose between open/endoscopic and robotic/non robotic. 

The robot is a great tool that can help the surgeon become more dextrous.  

Robotic assisted surgery allows performance of high dexterity operations with the help of robotic arms and improves technique due to tremor filtration, motion scaling, and ergonomics. The surgeon actually performs a better, more precise, and highly controlled surgical procedure under high magnification, which may result in an optimal surgical outcome. 

Other advantages are assepsia,instead of antisepsia, and protection of the patient and the surgeon from possible accidents that can cause contagious diseases. 

Options for augmented reality also exist. In the future, while the surgeon is performing the surgery, he may simultaneously be able to access 3D patient exams, consult a colleague who is also using a robot on line, and browse the internet for further information. 

 The sub-micron in-vivo histology with real-time functional imaging and diagnosis may help the surgeon in making decision for compressive syndromes secondary to tumors and rheumatic diseases.  

Specific antibodies and fluorescing markers will be helpful for recognizing structures we want to access and structures we want to avoid.

The principle problems of using the robotic surgery are surgery cost and the absence of tactile sensibility.

Many different tools need to be developed for future surgical procedures.

The absence of tactile sensibility is likely to be solved in the next generation of robots 53. 

The anatomic characteristics of the pathologic process and the surgeon’s expertise and judgement in specific cases remain important in determining surgical approach (open vs endoscopic vs robotic).

16.5 References

1. Steinmann SP and Spinner RJ in The Shoulder, Rokwood and Matsen 4th edition,Philadelphia, 2009.

2. Basset FH and Nunley JA: Compression of the musculocutaneous nerve at the elbow. J Bone Joint Surg  1982;64A:1050-1052.

3. Francel TJ, Dellon AL, Campbell JN. Quadrilateral space syndrome: diagnosis and operative decompression technique. Plast Reconstr Surg 1991;87:911-6.

4. Cahill BR, Palmer RE: Quadrilateral space syndrome.  J Hand Surg, 1983; 8A:65-69.

5.  Alon M, Weiss S, Fishel B, Dekel S: Bilateral suprascapular nerve entrapment syndrome due to an anomalous transverse scapular ligament. Clin Orthop Relat Res 1988:31-33. 

6. Hirayama T, Takemitsu Y: Compression of the suprascapular nerve by a ganglion at the suprascapular notch. Clin Orthop Relat Res 1981:95-96. 

7. Rengachary SS, Burr D, Lucas S, Brackett CE: Suprascapular entrapment neuropathy: A clinical, anatomical, and comparative study. Part 3: Comparative study. Neurosurgery 1979; 5:452-455. 

8. Ticker JB, Djurasovic M, Strauch RJ, et al: The incidence of ganglion cysts and other variations in anatomy along the course of the suprascapular nerve. J Shoulder Elbow Surg 1998;7:472-478. 

9. McIlveen SJ, Duralde XA, D’Alessandro DF, Bigliani LU: Isolated nerve injuries about the shoulder. Clin Orthop Relat Res 1994:54-63.  

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12.  Sandow MJ, Ilic J: Suprascapular nerve rotator cuff compression syndrome in volleyball players. J Shoulder Elbow Surg 1998;7:516-521. 

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26. Sharrard WJW. Posterior interosseous  neuritis. J. Bone Joint Surg 1966;48B:777.

27. Millender LH, Nalebuff EA and Holdsworth DE: Posterior interosseous syndrome secundary to rheumatoid synovitis. J Bone Joint Surg 1973;55A:753-757. 

28. Capener N: The vulnerability of the posterior interosseous nerve of the forearm. J Bone Joint Surg 1966;48B:770. 

29. Marmor  L, Lawrence JF and Dubois E. Posterior interosseous nerve paralysis due to rheumatoid arthritis. J. Bone Joint Surg. 49A:381,1967.

30. Marshall SC and Murray WR. Deep radial nerve palsy associated with rheumatoid arthritis. Clin. Orthop. 103:157, 1974.

31. Ritts GD, Wood MB, Linscheid RL: Radial tunnel syndrome: a ten year experience. Clin Orthop Rel Res 1987;219:201-205.

32. Roles NC, Maudsley RH: Radial tunnel syndrome: resistant tennis elbow as a nerve entrapment. J Bone Joint Surg 1972;54B:499-508.

33. Lazaro L III: Ulnar nerve instability: Ulnar nerve injury due to elbow flexion. South Med J 1977; 70:36-40.

34. Adelaar RS, Foster WC and McDowell C: The treatment of the cubital tunnel syndrome. J Hand Surg. 1984; 9A:90-95.

35. Werner CO, Ohlin P and Elmqvist D: Pressures recorded in ulnar neuropathy. Acta Orthop Scand 1985; 56:404-406.

36. Hartz CR, Linscheid RL, Granse RR and Daube JR: Pronator teres syndrome: compressive neuropathy of the median nerve. J Bone Joint Surg 1981; 63A:885.

37. Gross PT and Tolomeo EA: Proximal Median Neuropaties. Neurol Clin 1999; 17:425-445

38. Kiloh LG and Nevin S: Isolated neuritis of the anterior interosseous nerve. Br Med J 1952; 1:850-851.

39. Hill HA, Howard FM and Huffer BR: The incomplete anterior interosseous nerve syndrome. J Hand Surg 1985; 10A:4.

40. Spinner M: Injuries to the major branches of the forearm. 2nd Ed. Philadelphia WB Saunders, 1978. 

41. Kline DG, Hudson AR: Nerve Injuries: Operative Results for Major Nerve Injuries, Entrapments and Tumors,  Philadelphia, WB Saunders, 1995.

42. Post M and Grinblat E: Suprascapular nerve entrapment: Diagnosis and results of treatment. J Shoulder Elbow Surg., 1993;2:190-197.

43. Novak CB, Mackinnon SE: Surgical treatment of a long thoracic nerve palsy.  Ann Thoracic Surg  2002; 73:1643-1645.

44. Povacz P and Resch H: Dynamic stabilization of winging scapula by direct split pectoralis major transfer: A technical note. J Shoulder Elbow Surg 2000;9:76-78.

45. Jeon IH, Neumann L and Wallace WA. Scapulothoracic fusion for painful winging of the scapula in nondystrophic patients. J Shoulder Elbow Surg 2005;14:400-406.

46. Hunt JR: Tardy or late paralysis of the ulnar nerve: A form of chronic progressive neuritis developing many years after fracture dislocation  of the elbow joint. J Am Med Assoc 1916, 66:11-15.

47. Hoffmann R, Siemionow M. The endoscopic management of cubital tunnel syndrome. J Hand Surg. 2006;31B:23–29

48. Okutsu I, Ninomiya S, Takatori Y, Ugawa Y. Endoscopic management of carpal tunnel syndrome. Arthroscopy. 1989;5:11–18

49. Lafosse L, Piper Kalman and Lanz Ulrich: Arthroscopic suprascapular nerve release: indications and technique. J Shoulder Elbow Surg 2011; 20:S9-S13

50. Garcia JC: Arthroscopic decompression of the suprascapular nerve:surgical technique. Tech Shoulder Elbow Surg 2009; 10:157-159. 

51. Mantovani G, Liverneaux P, Garcia JC, Berner SH, Bednar MS and Mohr CJ: Endoscopic exploration and repair of Brachial plexus with telerobotic manipulation: a cadaver trial laboratory investigation. J Neurosurg 2011;(online first)

52. Guldmann R, Pourtales MC Liverneaux P: Is possible to use robots for carpal tunnel release? J Orthop Sci 2010;15:430-433.

53. Garcia JC, Mantovani G, Gouzou S and Liverneaux P. Telerobotic anterior translocation of the ulnar nerve. J Robotic Surg. 2011;5:153-156.