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n tips & techniquesSection Editor: Steven F. Harwin, MD

Cubital tunnel syndrome is the second most com-

mon nerve compression syn-drome in the upper extremity after carpal tunnel syndrome.1 Until recently, surgeons fo-cused on open decompression combined with submuscular or subcutaneous transposition of the nerve. Decompression was usually limited to the me-

dial epicondyle region, with a decompression range of 10 to 12 cm. Accordingly, the result-ing scars and related morbid-ity were large. Conversely, endoscopic decompression according to Hoffmann and Siemionow2 is a relatively new method for treating cubital tunnel syndrome by which a decompression range of 20 to

30 cm can be managed with a 1.8- to 2-cm skin incision. Anatomic studies and obser-vations of this method show that transverse, ligament-like thickenings of the submus-cular membrane are possible causes of nerve compression in this area.3

AnAtomyIn the area of the elbow, 5

common points of compres-sion can be identified: the arcade of Struthers, the me-dial intermuscular septum, the medial epicondyle, Osborne’s

ligament, and the fascia of the deep flexor pronator mus-cles.4,5 The ulnar nerve fol-lows the axillary artery at the upper arm medially into the sulcus bicipitalis medialis and perforates the medial inter-muscular septum to reach the dorsal side of the upper arm. An aponeurotic rim of the triceps muscle is sometimes present at the upper arm and the arcade of Struther, which is a fibrotic ligament between the triceps muscle and the in-termuscular septum. Although detected in only 13.5% of ca-

Abstract: The authors review the relevant anatomy and provide technical tips for endoscopic decompression of the cubital tunnel. Cubital tunnel syndrome is the second most common nerve compression syndrome in the upper extrem-ity. Until recently, surgeons focused on open decompression combined with submuscular or subcutaneous transposition of the nerve. Decompression was usually limited to the region of the medial epicondyle, and related morbidity was relatively high. Endoscopic decompression is a promising technique be-cause the dissection range can be extended and the scar length can be reduced. The authors review the relevant anatomy for the endoscopic approach and give some recommendations concerning the details of the surgical technique.

The authors are from the Department of Plastic, Aesthetic and Hand Surgery, Otto-von-Guericke-University, Magdeburg, Germany.

The authors have no relevant financial relationships to disclose.Correspondence should be addressed to: Armin Kraus, MD, Department

of Plastic, Aesthetic and Hand Surgery, Otto-von-Guericke-University, Leipziger Strasse 44, D-39120, Magdeburg, Germany (armin.kraus@ hotmail.com).

doi: 10.3928/01477447-20130426-04

Operative Decisions for Endoscopic Treatment of Cubital Tunnel SyndromeHans-Georg Damert, MD; Silke Altmann, MD; Manfred Infanger, MD; Armin Kraus, MD

1Figure 1: Illustration showing cubital tunnel with a distal exit. Reprinted with permission from: Siemionow M, Agaoglu G, Hoffmann R. Anatomic charac-teristics of a fascia and its bands overlying the ulnar nerve in the proximal forearm: a cadaver study. J Hand Surg Eur Vol. 2007; 32(3):302-307.

Cover Story

Cover illustration © Jennifer E. Fairman

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daveric specimens in 1 study,6 this structure can be a site of compression, particularly af-ter previous anterior transpo-sition of the nerve. The nerve continues distally between the medial intermuscular septum (which extends from the coracobrachialis muscle proximally to the medial epicondyle) and the triceps muscle. Vascular anomalies or thickening of the nerve itself may cause compression in this region.7 The nerve reaches the cubital tunnel, which is located between the medial

epicondyle and the olecranon (Figure 1). The cubital tun-nel is covered by a ligament-like thickening of the fascia, known as Osborne’s ligament (also called the ulnar collateral ligament, cubital retinaculum, or arcuate ligament), which is a thickened transverse band between the medial epicon-dyle and the olecranon.8

The more distal ligament extending between the 2 heads of the flexor carpi ul-naris (FCU) muscle is called Osborne’s fascia. According to anatomic studies, subtle

variations of this ligament may cause higher tension on the nerve at elbow flexion and predispose some individuals to compression symptoms.8 The ulnar nerve courses under this ligament toward the pal-mar side of the forearm. After leaving the distal entrance of Osborne’s ligament, the nerve is covered by the fascia of the deep flexor pronator muscles, which is the most distal com-mon site of compression at the elbow. It continues its course along the lateral side of its reference muscle (the FCU muscle). Less often, atypical muscle tissue, known as the epitrochleoanconeus muscle, is found in the cubital tunnel.

In the area of the medial epicondyle, the nerve branches to the dorsal parts of the elbow (ramus articularis cubiti). It further branches to the FCU muscle and to the ulnar part of the flexor digitorum profun-dus muscles. A dorsal branch leaves the nerve but not usu-ally before the distal one-third of the forearm. The bottom of the cubital tunnel consists of the channel between the me-dial epicondyle and the olec-

ranon. Osseous deformations, such as arthritic osteophytes or valgus deformity, may cause compression. The entrance of the cubital tunnel roof is built by the fibrous humeroulnar arcade, which becomes the fascia of the FCU muscle be-tween its 2 heads.

Anatomic studies of cubital tunnel syndrome show fibrous strands of the deep fascia in various diameters in a rela-tively constant distance to the retrocondylar groove.3,9 Two types of fascia that have either 3 or 4 fibrous strands, type 1 or 2 fascia, respectively, in a constant distance from the retrocondylar groove can be distinguished (Figure 2). If the nerve is transposed and these strands are not cut, kinking of the nerve is possible and can cause continuous symptoms or recurrence.

Patients susceptible to ul-nar nerve compression at the elbow are those with frequent flexion of the elbow, such as what occurs when holding telephones or working with vibrating machines.10 Diabetes mellitus is also a risk fac-tor because it compromises microcirculation and the in-nate metabolism of the nerve. Playing sports with overhead-throwing actions, where strong flexion and acceleration occur, is also a predisposing factor.

SymptomSParesis commonly has a

sudden onset (ie, overnight). Patients report intermittent numbness in the ring and small fingers or in the hypothenar. Tearing pain in the forearm and elbow are also reported. In

2A 2BFigure 2: Illustrations showing a type 1 fascia with 3 ligament sections in the fascia (A) and a type 2 fascia with 4 liga-ment parts (B). Reprinted with permission from: Siemionow M, Agaoglu G, Hoffmann R. Anatomic characteristics of a fascia and its bands overlying the ulnar nerve in the proximal forearm: a cadaver study. J Hand Surg Eur Vol. 2007; 32(3):302-307.

3Figure 3: Photograph showing advanced cubital tunnel syndrome with atro-phy of the intrinsic muscles innervated by the ulnar nerve, as indicated by hypothenar atrophy, atrophy of the first interdigital grove, and atrophy of the interosseous muscle in the right hand.

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more advanced stages, patients have a loss of strength in the affected hand and some loss of skillfulness in the most impor-tant types of grip. Due to pare-sis of the intrinsic muscles, pa-tients may be unable to adduct the small finger. In late stages, the interosseous muscles and the adductor pollicis muscle become atrophic (Figure 3). Dellon’s classification can be used to grade cubital tunnel syndrome into 3 stages: stage 1 (mild), intermittent paresthe-sia, subjective weakness; stage 2 (moderate), intermittent par-esthesia, measurable weak-ness; stage 3 (severe), perma-nent paresthesia, palsy.11

EndoScopic dEcomprESSion

In addition to the instru-ments required for open de-compression, a lighted specu-lum, a dissector with 4-mm optics (Figure 4), and a camera with a monitor are needed.

Surgical TechniqueGenerally, the operation

is performed with the patient under general anesthesia and with the use of an upper-arm tourniquet. The arm is posi-tioned on an arm table with the shoulder in 90° of abduction. The elbow is flexed, and the wrist is supinated. After pal-pation of the nerve behind the epicondyle, a 2-cm incision is made along the retrocondylar groove (Figure 5). The roof of the cubital tunnel is exposed and opened. The nerve is easy to spot due to its bright color and its longitudinal commit-tant veins. After identifying the nerve, the roof is cut over a

short distance in proximal and distal directions. The tunnel is bluntly dissected on the fascia using forceps.

Using this method, the separation of the fascia from subcutaneous tissue is usu-ally straightforward (Figure 6). The lighted speculum is inserted into the dissected tun-nel to cut Osborne’s ligament (). The FCU fascia can also be dissected under vision by the speculum. In a proximal direction, the fascia of the up-per arm is dissected as far as possible by using the specu-lum. The endoscope with the dissector can then be inserted to continue decompression. Dissection at the upper arm is usually easier because the nerve is only covered by the fascia. Often, it is even pos-sible to dissect right under the tourniquet. A firm Struther arcade is sometimes found at the upper arm, which must be dissected to complete de-compression. Distal dissection is more challenging because several layers of tissue must be removed to decompress the nerve. Then, dissection of the forearm fascia is continued. Crossing blood vessels can be undermined and preserved (Figure 8).

After that, the 2 bellies of the FCU muscle, which are connected by a muscle bridge, are divided. At the proximal end of the muscle bridge, the sharp-edged tendon arcade of the FCU muscle is located 3 cm distal to the retrocondylar groove (Figure 9). After sepa-ration, decompression of the FCU muscle from the nerve is continued. The deep fascia

with its submuscular mem-branes is dissected at a length of 10 to 15 cm starting from the groove (Figures 10, 11). As in the superficial layers, nerve branches and crossing vessels can be identified and

preserved. In adipose patients, dissection is sometimes more difficult to perform due to pro-truding fat. Electrocautery is rarely necessary except at the incision rims, and a drain is sel-dom required. Intracutaneous

5A 5BFigure 5: Photographs showing the length of the incision at the elbow (A, B).

6Figure 6: Endoscopic image showing the space between the subcutaneous tissue and the fascia with a crossing vein.

7Figure 7: Endoscopic image show-ing the ulnar nerve in the cubital tunnel after transection of Osborne’s ligament (white structure in upper section). The scissor tip is pointing toward the nerve).

Figure 4: Photograph of the instruments needed for endoscopic decompres-sion of the cubital tunnel (KARL STORZ GmbH & Co, KG, Tuttlingen, Germa-ny). The camera and monitor unit are not shown. Reprinted with permission from KARL STORZ GmbH & Co, KG.

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hematomas sometimes occur, but they usually heal sponta-neously.

Postoperative Treatment Elastic gauze is used in ad-

dition to the dressing (Figure 12) to restrict elbow movement for 10 days postoperatively. The drape is applied with the elbow in 45° of flexion and allows light movement but prevents com-plete flexion and extension. If

patient compliance is limited, an upper-arm cast can also be used. Beginning on postoperative day 11, an elbow bandage is used for another 4 weeks.

diScuSSionCubital tunnel syndrome

is a compression syndrome of the ulnar nerve in the upper arm and forearm. Recently, a trend toward less-invasive procedures for ulnar nerve

decompression, instead of open transposition (submus-cular or subcutaneous) toward endoscopic decompression has been observed. Massive scarring and neuroma forma-tion are common, particu-larly after open decompres-sion and nerve transposition. Transposition is justified for selected indications, particu-larly in posttraumatic cases. Endoscopically, longer de-compression distances are possible with minimal trauma compared with the traditional approach. Decompression can be performed atraumati-cally, and collateral nerves and vessels can be preserved. Devascularization of the nerve and damage of the collateral nerves does not occur with this method, as is possible with transposition. In the litera-ture, decompression without transposition is recommend-ed for primary surgery, both open and endoscopic, even in severe cases.12 This is also recommended for cases with luxation tendency of the nerve and slight deformation of the elbow.

However, severe defor-mations of the elbow, such as strong valgus deformity, arthritis with osteophytes im-pinging into the cubital tunnel, or massive and long-standing elbow contractures requiring release, are contraindications to the endoscopic procedure.13 A previous open procedure is sometimes regarded as a con-traindication. However, the au-thors successfully performed endoscopic decompression after a failed open surgery but did not do it in cases of previ-

ous transposition of the nerve or when supposed massive scarring was observed. A situ-ation where subluxation of the ulnar nerve over the medial epicondyle is supposed to be the main reason of symptoms is regarded as a relative con-traindication for endoscopic release.4,13 In these cases, de-compression without trans-position may even aggravate symptoms by increasing the instability of the nerve.

The authors regard epi-neural dissection to be rarely indicated and interfascicular dissection to be never indi-cated. Assmus14 reported a series of 523 open decompres-sions without transposition. He found a recovery time in cases of light and medium severity of 2 to 4 months and a recovery time of up to 12 months in patients of high se-verity on average.14 Hoffmann and Siemionow2 reported good and very good results in 94% of cases, with 95% of the pa-tients describing symptoms of improvement within 24 hours or a few days, and no recur-rence occurred. Very good results were also observed in Dellon stage II (97%) and III (89%). According to the au-thors, this contradicts the pre-vailing opinion that the surgi-cal approach in cubital tunnel syndrome should be adapted to its stage. Superficial hema-tomas and loss of sensation in the ulnar forearm were re-ported as complications, were temporary, and occurred in 8% of the patients initially. After blunt dissection of the tunnel was performed more cautious-ly, this complication was not

11Figure 11: Endoscopic image show-ing the completion of decompression.

12Figure 12: Photograph showing the elastic dressing for immobilization of the elbow.

10A 10BFigure 10: Endoscopic image showing dissection of the deep fascia (A) and the submuscular membrane (B).

8Figure 8: Endoscopic image show-ing dissection of the forearm fas-cia, undermined crossing vessels (12-o’clock position) and the nerve at the 6-o’clock position.

9Figure 9: Endoscopic image showing the tendon arcade of the flexor carpi ulnaris muscle.

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observed any more according to the author.2

Operative time is con-siderably shorter for the endoscopic than the open approach when performed by an experienced surgeon. Learning time in this method is short for a skilled surgeon. However, profound experi-ence in nerve surgery and mastering the open technique are requirements for using the endoscopic method. Higher requirements in technical equipment and higher costs are drawbacks of this method. However, patient satisfaction is considerably higher due to a more aesthetically pleasing scar and reduced pain. Other compression syndromes, such as the anterior interosseous

syndrome, the supinator syn-drome, or Wartenberg’s syn-drome, could also be treated endoscopically with minimal invasiveness.

concluSionFor the endoscopic treat-

ment of cubital tunnel syn-drome, knowledge of relevant anatomy and experience with the open technique are re-quired. The endoscopic ap-proach may become the stan-dard treatment for cubital tun-nel syndrome.

rEfErEncES 1. Nakano KK. Nerve entrapment

syndromes. Curr Opin Rheu-matol. 1997; 9(2):165-173.

2. Hoffmann R, Siemionow M. The endoscopic management of cubital tunnel syndrome. J

Hand Surg Br. 2006; 31(1):23-29.

3. Siemionow M, Agaoglu G, Hoffmann R. Anatomic charac-teristics of a fascia and its bands overlying the ulnar nerve in the proximal forearm: a cadaver study. J Hand Surg Eur Vol. 2007; 32(3):302-307.

4. Palmer BA, Hughes TB. Cu-bital tunnel syndrome. J Hand Surg Am. 2010; 35(1):153-163.

5. Bruno W, Tsai T. Minimally in-vasive release of the cubital tunnel. Oper Tech Plast Re-constr Surg. 2003; 9(4):131-137.

6. Siqueira MG, Martins RS. The controversial arcade of Struthers. Surg Neurol. 2005; 64(suppl 1):S1:17- S1:20.

7. Jia ZR, Shi X, Sun XR. Patho-genesis and electrodiagnosis of cubital tunnel syndrome. Chin Med J (Engl). 2004; 117(9):1313-1316.

8. O’Driscoll SW, Horii E, Car-michael SW, Morrey BF. The cubital tunnel and ulnar neu-

ropathy. J Bone Joint Surg Br. 1991; 73(4):613-617.

9. Matsuzaki A. Membranous tis-sue under the flexor carpi ulna-ris muscle as a cause of cubital tunnel syndrome. Hand Surg. 2001; 6(2):191-197.

10. Cutts S. Cubital tunnel syn-drome. Postgrad Med J. 2007; 83(975):28-31.

11. Dellon AL. Clinical grading of peripheral nerve problems. Neurosurg Clin N Am. 2001; 12(2):229-240.

12. Assmus H, Antoniadis G, Bischoff C, et al. Cubital tunnel syndrome: a review and man-agement guidelines. Cen Eur Neurosurg. 2011; 72(2):90-98.

13. Cobb TK. Endoscopic cubital tunnel release. J Hand Surg Am. 2010; 35(10):1690-1697.

14. Assmus H. Simple decompres-sion of the ulnar nerve in cubi-tal tunnel syndrome with and without morphologic changes. Report of experiences based on 523 cases [in German]. Nerv-narzt. 1994; 65(12):846-853.