Cause, Diagnosis and Management
Cubital tunnel syndrome is the most common form of entrapment of the ulnar nerve and the second most common nerve compression syndrome of the upper extremity after carpal tunnel syndrome.

Surgical anatomy of ulnar nerve
In the middle one third of the arm, the ulnar nerve accompanies the superior ulnar collateral artery posteriorly through the intermuscular septum to lie on the anterior aspect of the medial head of the triceps muscle. The nerve travels on the posterior surface of the intermuscular septum medial to the humerus, to reach the elbow. It traverses the elbow region bounded medially and anteriorly (superiorly) by the medial humeral epicondyle, laterally by the olecranon and by a connective tissue roof spanning the two bony prominences-the “epicondylar groove.” The nerve then enters the “cubital tunnel” by passing deep to the arcuate ligament (Osborne’s ligament), which connects the ulnar and humeral heads of the flexor carpi ulnaris (FCU) muscle. The nerve then passes between the two heads of the FCU and passes deep to the deep flexor pronator aponeurosis. It then travels through the forearm between the FCU and flexor digitorum profundus (FDP), giving off motor branches to the FDP of the small and ring fingers. The nerve enters the wrist through Guyon’s canal; a fibro-osseous canal, extending 4 cm from the palmar carpal ligament to the fibrous edge of the hypothenar muscles. This is also a common site of ulnar nerve entrapment.

With flexion of the elbow, the aponeurosis covering the cubital tunnel stretches, changing the cross-sectional geometry of the cubital tunnel from smooth and round to flattened and triangular. This both decreases the volume of the tunnel by 55%,² and significantly increases the intraneural pressure, therefore putting the nerve at risk of ischaemia. Intraneural pressure can be increased up to 600% with shoulder abduction, elbow flexion, and wrist extension. ³ Moreover, contraction of the FCU muscle may increase the pressure on the ulnar nerve.⁴ Normally, the ulnar nerve at the cubital tunnel is known to elongate 4.7 mm during elbow flexion. Should the nerve be tethered by perineural fibrosis (e.g., postoperative, post-trauma), it can no longer elongate and may experience up to doubled intraneural pressures.³
There is increasing evidence that cumulative or repetitive trauma work disorders are a cause of cubital tunnel syndrome. Keyboard operators, for instance, appear to be at increased risk. It is postulated that poor seating is a significant ergonomic factor; the keyboard placed too high and too close to the operator causes shoulder flexion, elbow flexion, wrist extension, and, therefore, traction on the uInar nerve .^{5, 17}

McGowan established the following classification system:
Grade I – Mild lesions with paresthesias in the ulnar nerve distribution and a feeling of clumsiness in the affected hand; no wasting or weakness of the intrinsic muscles
Grade II – Intermediate lesions with weak interossei and muscle wasting
Grade III – Severe lesions with paralysis of the interossei and a marked weakness of the hand.

Symptoms may primarily involve numbness and tingling in the little and ring fingers in the ulnar nerve distribution. These complaints occur or worsen when the elbow is bent, as when: 1) holding a telephone in the hand, 2) resting the head on the hand, 3) crossing the arms over the chest, 4) curling the arm under the body during the night while sleeping.

The physical examination
Look for increased the carrying angle, examine for ulnar nerve subluxation. A positive Tinel sign finding is typically present in cubital tunnel syndrome. The elbow flexion test, a provocative test, is analogous to Phalen’s test for carpal tunnel syndrome is the most diagnostic test for cubital tunnel syndrome. The test involves the patient flexing the elbow past 90 degrees, supinating the forearm, and extending the wrist. Results are positive if discomfort is reproduced or paresthesia occurs within 60 seconds. The addition of shoulder abduction may enhance the diagnostic capacity of this test.
Examine for ulnar nerve involvement, like intrinsic muscle weakness, clawing or abduction of the small finger with extension (Wartenberg sign) and Froment sign. Record grip and pinch strength. Check for 2-point discrimination. Evaluation of sensation, especially the area on the ulnar dorsum of the hand supplied by the dorsal ulnar sensory nerve is done; hypoaesthesia in this area suggests a lesion proximal to the Guyon canal.
Differential diagnosis should include other causes of dysesthesias and weakness along the C8-T1 distribution, such as cervical disk disease or arthritis, thoracic outlet syndrome, or ulnar nerve impingement at the Guyon canal.
EMG and nerve conduction studies are also helpful. In some circumstances, however, the studies may prove to be normal in a clinically diagnosed case of cubital tunnel syndrome (often mild and intermittent). One review noted nerve conduction study abnormalities ranged from 23% to 93% in classic cases of cubital tunnel syndrome.1Moreover, the severity of the clinical manifestations does not always correlate with the objective electrodiagnostic changes .⁶
Some authors believe that nerve conduction studies are not necessary if the diagnosis of cubital tunnel syndrome is obvious.^{7, 8} While, others have stated that a normal electrophysiologic study is a contraindication to surgery.^{9, 10}
Urbaniak¹⁰ believes following patients should undergo a trial of conservative treatment:

1. Early symptoms and/or intermittent episodes.
2. Mild paresthesias without significant pain.
3. Minimal physical findings (slight numbness), with normal motor examination.

Conservative treatment
Avoiding aggravating factors (i.e., pressure on the elbow, repetitive flexion/extension) Avoiding full flexion (particularly at night).
Effective measures include the avoidance of pressure with elbow pads,^11-13 Night splints to prevent elbow flexion. ^{11, 12}
Avoidance of repetitive movements, and ergonomic workplace modification.⁵
The use of nonsteroidal anti-inflammatory drugs¹² may be beneficial.
Patients should be followed at 1 to 3 month intervals until improvement is noted and maintained. It is well recognized that those with severe findings of weakness, decreased two-point discrimination, and electromyographic evidence of denervation potentials should undergo operative exploration without a trial conservative treatment.^{11, 14, 15}

Surgical treatment
Local decompression of the ulnar nerve can be achieved in situ by either simple decompression with/without medial epicondylectomy or combined with anterior transposition. In situ decompression involves the release of the deep fascia overlying the nerve in the epicondylar groove and of the FCU aponeurosis.
Ferlic16 recommended decompression alone in following conditions
(1) Symptoms are mild or intermittent.
(2) There is no subluxation or instability of the uInar nerve (anterior to the epicondyle).
(3) There is absence of pain.
(4) Osseous architecture of the elbow is normal.

Medial epicondylectomy
Make a longitudinal incision 10-15 cm in length over the course of the nerve, and center it 1 cm anterior to the tip of the medial epicondyle. Again, identify and protect the posterior branches of the medial brachial and antebrachial cutaneous nerves and decompress the nerve as above. Make a longitudinal incision over the medial epicondyle and expose this by subperiosteal dissection. Detach the flexor pronator origin from the epicondyle and reflect it distally. Remove the medial epicondyle, or a portion of it, with an osteotome. Do not enter the elbow joint or cut the ulnar collateral ligament. Reattach the flexor pronator origin with the elbow in extension to help prevent development of a flexion contracture. Allow the ulnar nerve to slide anteriorly.

Anterior transposition
Make a longitudinal incision 15 cm in length over the course of the nerve and decompress the nerve as described earlier. Excise 3-4 cm of the medial intermuscular septum proximal to the medial epicondyle to prevent kinking of the nerve postoperatively. Distally look for the additional, common aponeurosis between the FDS to the ring finger and the humeral head of the FCU. Excise this, if present, to prevent kinking. Identify, protect, and preserve the motor branches to the FCU and FDP. Dissect out the first motor branch to the FCU from the ulnar nerve proper if necessary to prevent kinking. Transpose the nerve into the subcutaneous plane.
Anterior transposition procedures move the ulnar nerve anterior to the axis of elbow motion and thereby theoretically decrease the traction and compressive forces upon the nerve. ¹⁷ There are three types of transposition-subcutaneous, submuscular, and intramuscular. Subcutaneous transposition moves the nerve into the subcutaneous plane and holds it there with a fascial sling. ^{18, 19} Submuscular transposition moves the nerve deep to the flexor pronator mass .¹⁷ Intramuscular transposition places the nerve in a channel within the flexor pronator mass without damaging the muscle origin.^{20, 21}

The Endoscopic Management of Cubital Tunnel Syndrome
Endoscopic release allows local decompression with the ability to decompress the nerve at all potential sites of compression. The potential advantages of this technique include limited invasiveness, reduced complication rates, and quicker rehabilitation.

Tsai et al²² performed an endoscopic cubital tunnel release on 85 elbows in 76 patients and monitored them for an average of 32 months. 42% had excellent results, 45% had good results, 11% had fair results, and 2% had poor results. These results are comparable to the other decompressive techniques, which overall result in 85-90% good-to-excellent results.

Hoffmann et al²³ reported their results of endoscopic ulnar nerve decompression at the elbow in 75 patients (76 cases). They were able to release the ulnar nerve over a distance of approximately 17 cm through an incision averaging 2.8 cm in length. The mean follow-up interval was 11 months (range, 1-34 months). Using the modified Bishop Rating System, the authors found good to excellent results in 94% of patients. The authors also reported their observations from dissecting 12 cadaver arms. They found 3 distinct fascial bands covering the ulnar nerve in the proximal forearm. The bands extended from 3 to 9 cm distal to the midpoint of the retrocondylar groove and all three bands could be released endoscopically. Similarly we did our first case in India of endoscopic cubital tunnel release 4 months back with excellent result. In India Ulnar nerve involvement following trauma to elbow is common and such cases require ulnar nerve decompression along with anterior transposition of ulnar nerve.

References

1. Dawson DM, Hallett M, Millender LH: Entrapment Neuropathies. Boston, Little, Brown, 1983, pp 99-116.
2. Apfelberg DB, Larson SJ: Dynamic anatomy of the u1nar nerve at the elbow. Plast Reconstr Surg 51:7681, 1973
3. Pechan J, Julius 1: The pressure measurement in the ulnar nerve: A contribution to the pathophysiology of the cubital tunnel syndrome. J Biomech 8:75-79, 1975.
4. Rayan GM: Proximal u1nar nerve compression. Hand Clin 8:325-336, 1992.
5. Mackinnon SE, Novak CB: Clinical commentary: Pathogenesis of cumulative trauma disorder. J Hand Surg Am 19A:873-883,1994
6. Kleinman WB: Revision u1nar neuroplasty. Hand Clin 10:461-477, 1994.
7. Mackinnon SE, Dellon AL: Surgery of the Peripheral Nerve. New York, Thierne, 1988.
8. MacPherson SA, Meals RA: Cubital tunnel syndrome. Orthop Clin North Am 23:111-123, 1992.
9. Craven PR, Green DP: Cubital tunnel syndrome: Treatment by medial epicondylectomy. J Bone joint Surg Am 62A:986-989, 1980.
10. Urbaniak JR, Gabel GT: Perspectives on the operative treatment of cubital tunnel syndrome. In Gelberman RH (ed): Operative Nerve Repair and Reconstruction. Philadelphia, JB Lippincott, 1991, pp 1121-1130.
11. Dellon AL, Hament W, Gittelshon A: Nonoperative management of cubital tunnel syndrome: An 8-year prospective study. Neurology 43:1673-1677, 1993.
12. Dimond ML, Lister GD: Cubital tunnel syndrome treated by long-arm splintage. J Hand Surg Am 10:430, 1985.
13. Ferlic DC: Clinical assessment and conservative treatment of cubital tunnel syndrome. In Gelberman RH (ed): Operative Nerve Repair and Reconstruction. Philadelphia, JB Lippincott, 1991, pp 1055-1062.
14. Bednar MS, Blair SJ, Light TR: Complications of treatment of cubital tunnel syndrome. Hand Clin 10:8392,1994.
15. Ferlic DC: Clinical assessment and conservative treatment of cubital tunnel syndrome. In Gelberman RH (ed): Operative Nerve Repair and Reconstruction. Philadelphia, JB Lippincott, 1991, pp 1055-1062.
16. Ferlic DC: In situ decompression of the uInar nerve at the elbow. In Gelberman RH (ed): Operative Nerve Repair and Reconstruction. Philadelphia, JB Lippin cott, 1991, pp 1063-1068.
17. Rayan GM: Proximal u1nar nerve compression. Hand Clin 8:325-336, 1992.
18. Eaton RG: Anterior subcutaneous transposition. In Gelberman RH (ed): Operative Nerve Repair and Reconstruction. Philadelphia, JB Lippincott, 1991, pp 1077-1086.
19. Eaton RG, Crowe JF, Parkes JC: Anterior transposition of the u1nar nerve using a noncompressing fasciodermal sling. J Bone Joint Surg 62A:820-825, 1980.
20. Kleinman WB: Anterior intramuscular transposition. In Gelberman RH (ed): Operative Nerve Repair and Reconstruction. Philadelphia, JB Lippincott, 1991, pp 1069-1076.
21. Kleinman WB: Revision u1nar neuroplasty. Hand Clin 10:461-477, 1994.
22. Tsai TM, Chen IC, Majd ME: Cubital tunnel release with endoscopic assistance: results of a new technique. J Hand Surg [Am] 1999 Jan; 24(1): 21-9.
23. Hoffmann R, Siemionow M. The Endoscopic Management of Cubital Tunnel Syndrome. J Hand Surg 31B:23-29, 2006.

Dr. VIKAS GUPTA
Cheif & Head of Hand and Upper Extremity
Max Hospital (Saket & Gurugram)
E mail: handsurgeryclinic@gmail.com
Visit us at www.handsurgeryclinic.com