David J. Slutsky

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3475 Torrance Blvd., Ste F
Torrance, CA 90503

Appointments: 310.792.1809
Fax: 310.792.1811

Office hours: M-F, 9am – 5 pm

Worker’s compensation, Medicare and most insurance plans accepted.

In September 2008, we will be moving to a beautiful new 4,400 sq ft, state of the art dedicated hand center located at 2808 Columbia Ave in Torrance, CA., which will feature onsite nerve conduction studies, occupational hand therapy and digital x-ray.



The ulnar nerve is most commonly entrapped at the elbow (see cubital tunnel syndrome). There are circumstances however in which it can be compressed at the wrist level. This syndrome was well described by a Frenchman named Guyon in the 1900’s and hence now bears his name.

The ulnar tunnel or Guyon’s canal is approximately 4 cm in length, which begins at the proximal edge of the carpal transverse ligament and ends at the fibrous arch of the hypothenar arch. It is bounded medially by the pisiform, and radially by the hamate hook. The floor consists of the carpal transverse ligament and the roof consists of the continuation of the deep forearm fascia i.e the volar carpal ligament. The ulnar nerve has 15 to 25 fascicles at the wrist. It can be clearly divided into a volar sensory component and a dorsal motor component. At the wrist, the ulnar nerve passes over the TCL, medial to the ulnar artery, through Guyon’s canal. The deep motor branch is given off at the pisiform and passes underneath a fibrous arch to lie on the palmar surface of the interossei. It crosses the palm deep to the flexor tendons, to terminate in the adductor pollicus and ulnar head of the flexor pollicus brevis.

The standard teaching divides the sites of compression in Guyon’s canal into 3 zones. In zone 1, nerve compression leads to mixed motor and sensory symptoms. In zone II symptoms are purely sensory and in zone III symptoms are purely motor and restricted to muscles innervated by the deep ulnar motor branch. Two sites of entrapment distal to the abductor digiti minimi have also been described. In these cases the ADM will be preserved while there is weakness and wasting of the intrinsics (link to guyons 1,2).

The patient may also present with complaints of numbness and tingling of the small and/or ring finger. The dorsoulnar aspect of the hand however is not affected. The patient may give a history of repetitive percussion using the hypothenar eminence which may occur with autobody technicians, martial artists and percussionists. Bicyclists who ride for extended periods in the crouch position may entrap the deep motor branch against the hamate hook while grasping the handle bars. A history of Raynaud’s symptoms should alert one to the possibility of ulnar artery thrombosis.

There are no characteristic findings of ulnar tunnel entrapment per se. A tinel’s sign may be present at the wrist but not the elbow unless there is an associated cubital tunnel entrapment. Intrinsic atrophy may also occur in chronic compression, but the forearm muscles i.e. the flexor carpi ulnaris and the flexor digitorum profundus flexor tendons to the fingers are not affected. There should be a negative tinel’s at the elbow and a negative elbow flexion test. If there is an associated ulnar artery aneurysm there may be a palpable thrill and an audible bruit. With ulnar artery thrombosis the Allen’s test will be positive for ulnar artery occlusion. With an associated fracture of the hook of the hamate, there will be localized tenderness in the palm, 1 cm radial and 1 cm distal to the pisiform. Ancillary testing such as ultrasound, CT, angiography and MRI may be employed to aid in the diagnosis of these associated entities.

Electrodiagnostic Studies
Ulnar motor studies are more popular than ulnar sensory studies. The distal motor latency is determined by recording from an electrode placed over the midpoint of the abductor digiti minimi (ADM) while stimulating the ulnar nerve 8 cm proximally (S1). Normal values include a DML # 3.6 ms and amplitude > 4.0 MV. Alternatively, the latencies can be measured from the first dorsal interosseous (FDI), which then assesses conduction through the deep motor branch of the ulnar nerve. The FDI to ADM latency should not exceed 2.0 ms. The ulnar nerve is then stimulated 4 cm distal to the medial epicondyle (S2). By subtracting the latency for S1 from S2 and measuring the intervening distance, the forearm conduction velocity is obtained. Ulnar nerve conduction across the cubital tunnel is calculated by stimulating the nerve at S3, which is 12 cm proximal to S2, and subtracting the latencies. Most labs measure conduction with the elbow flexed between 90 - 135°. Normal forearm NCV is > 48 m/s. Across the cubital tunnel the NCV should be > 45 m/s. More than 10 m/s of slowing between the above and below elbow NCV is abnormal. Amplitude drops of > 20% are a more sensitive indicator of conduction block or axonal loss.

Ulnar nerve sensory studies
Ring electrodes are placed on the small finger and the ulnar nerve is stimulated 14 cm proximally. Recordings are also taken from the ring finger after stimulation of both the ulnar and median nerves. This allows for comparison of the ulnar to the median SNAPs. Normal peak sensory latencies are # 3.5 ms and < 0.5 ms median - ulnar difference. Mixed palmar orthodromic studies can be elicited by stimulating the ulnar nerve in the 4th webspace and recording over the ulnar nerve at the wrist 8 cm proximally. This measures the sensory nerve conduction through Guyon’s canal. Normal values are < 2.2 ms.

The usual nerve conduction studies are inadequate at assessing ulnar nerve entrapment in the palm. Short segment incremental studies (SSIS) is a sensitive and specific way to assess the deep motor branch since focal conduction abnormalities also tend to be normalized over the distance between the ADM and the FDI. The ulnar nerve is stimulated in 1 cm increments from 3 - 4 cm proximal and distal to the wrist crease. Abnormal values include a > 0.5 ms jump or a >120% drop in amplitude. When this is combined with FDI conduction and interosseous-latency differences the diagnostic yield increases.

Quantitative sensory testing
The 2PS to the small finger is the first to go, followed by an abnormal 1 PS. The dorsoulnar carpus should remain normal unless there is an associated C8-T1 radiculopathy.

Nonoperative treatment
The mainstay of treatment is activity modification. Bicyclists should avoid riding in the crouch position with their hands low on the handlebars since this is a recognized precipitant of symptoms, and change their hand position frequently. Autobody repair technicians, martial artists and percussionists should avoid repetitive hammering using the ulnar border of their palm. Wrist splinting and cortisone injections have no role in this condition.

Surgical Indications
Intrinisic wasting and/or sensory loss are a sine qua non for decompression. The presence of a mass occupying lesion also mandates surgical treatment. Ulnar artery thrombosis or aneurym may be treated with ulnar artery repair or ligation.

Ulnar motor and/or sensory disturbances due to more proximal causes preclude a distal release. Ulnar sensory disturbances in CTS were a common indication for release in the 80's, but has now become an infrequent indication for the release of Guyon’s canal since the majority of patients experience improvement following a CTR.

Surgical technique
The ulnar nerve is identified proximal to the distal wrist crease between the FCU and the flexor tendons through a curving incision which crosses the wrist obliquely, and bisects the interval between the pisiform and the hook of the hamate. The ulnar nerve is followed distally as the volar carpal ligament is released. The ulnar artery is inspected for thrombosis or aneurysm. The fibrous arch of the hypothenar muscles is incised and the floor of the canal is explored for masses, fibrous bands or anomalous muscles(link to guyons 3). With entrapment in the palm, the deep motor branch is followed distally as it traverses the palm lying on the interosseous fascia, deep to the flexor tendons and superficial palmar arch. The dissection is completed as the motor branch ends in the muscle belly of the adductor pollicus. I frequently employ intraoperative nerve conduction studies to ensure that the nerve is completely decompressed (link to guyons 4).

These are mostly related to injury to the branches of the ulnar nerve or artery. Injury to the palmar cutaneous branches of the ulnar nerve or the nerve of Henlé (if present) may result in scar tenderness and hypoesthesiae. Uncommonly injury to the pisiform ligament complex can result in instability of the pisotriquetral joint.

Clinical recovery is seen in the majority of patients when the ulnar nerve entrapment is due to a space occupying lesion. Motor recovery is less predictable when compared to sensory recovery, especially when the compression is due to a fibrotic hypothenar arch or of a longstanding nature, but good results can be obtained (link to guyons 5).

Work Considerations
Most people can perform one-handed work activity by the 2nd week followed by light duty including clerical work at 6-8 weeks. Heavy manual labor can often be resumed by 8 -12 weeks.