Subcutaneous or submuscular anterior transposition of the ulnar nerve?

SUBCUTANEOUS TRANSPOSITION

OR SUBMUSCULAR OF THE ULNAR

M. STUFFER, W. JUNGWIRTH,

ANTERIOR NERVE?

H. HUSSL and E. SCHMUTZHARDT

From the Department of Plastic and Reconstructive Surgery, and Neurology, Universityof Innsbruck, Austria

Precise clinical and electroneurograpbic examinations were made of 51 patients before and after anterior transposition of the ulnar nerve. The mean follow-up period was 9.6 years. In 86%, hand function improved, while in 10% it remained unchanged. Subcutaneous transposition was better than submuscular transposition, especially with regard to sensation. This method is simple and involves low morbidity for patients. Journal of Hand Surgery

(British Volume, 1991) 17B: 248-250

Neurophysiologicalfindings

Surgical treatment of ulnar neuropathy at the elbow has been performed according to a wide variety of techniques since the end of the last century. These range from simple decompression (Osborne, 1957) to various forms of nerve transposition (Nigst, 1953; Sunderland, 1968) and medial epicondylectomy (King and Morgan, 1959). The published results of these surgical methods can hardly be compared with one another. Chan (1980) compared two surgical methods : simple decompression and anterior transposition of the nerve. Our paper evaluates the results after anterior transposition of the ulnar nerve using objective parameters and compares the results of submuscular and subcutaneous transposition.

b)

Nerve conduction velocities at the level of the elbow (motor conduction velocity and antidromic sensory neurography). Nerve conduction velocities in the forearm (motor conduction velocity and antidromic sensory neurography).

We rated overall hand function in four categories. Each criterion examined in the follow-up period was rated on a scale of 0 to 2 points. The best possible score was thus 8 points (Table 1). Table l-Our

rating system for hand function

Patients and method

Criterion

0 points

I point

Zpoints

From 1972 to 1987, 113 patients underwent surgery at our clinic for ulnar neuropathy at the elbow. Follow-up investigations covered 51 patients. The mean age at operation of the patients followed up was 45 years and ranged from 15 to 70 years. The nerve lesion was due to injury in 17 cases, chronic subluxation of the nerve in three and in one case was caused by iatrogenic damage from faulty positioning during surgery. In 30 patients, the aetiology remained undefined. In 33 patients a subcutaneous and in 18 patients a submuscular anterior transposition was performed, with additional neurolysis in 18 cases. In 25 patients, the nerve was seen at operation to be clearly constricted at and distended proximal to the compression site. The following assessment was made before operation and at the follow-up examination :

Pain Sensation Muscle strength Muscle atrophy

Severe Lacking Paralysis Severe

Slight Diminished Weakness Moderate

None Normal Normal None

O-2 poor, 3-4

moderate, 5-6 satisfactory,7-8 good

Results The mean follow-up period was 9.6 f 3.6 years, with a minimum of two years after operation. The longest follow-up period was 17 years. The results for pain, sensation, muscle strength and muscle atrophy are shown in Tables 2 to 5. Poor to moderate function (O-4 points) was found in 75% of patients before operation, but in only 24% afterwards. Satisfactory to good hand function (5-8 points) was found in 76% of all the operated patients (Fig. 1).

Clinical examination

4 Pain: severe with nocturnal pain at rest, slight, no

Table Z-Severity

pain. b) Sensation: static two-point discrimination measured by the device of Greulich (1976). 4 Muscle strength: rated on a scale of M 0 to M 5 (Highet, 1954). 4 Muscle atrophy.

of pain before and after operation

Pre-operative Severe Slight None 248

23 (45%) 16 (31%) 12 (24%)

Post-operative 5 (10%) 13 (25%) 33 (65%)

ANTERIOR

TRANSPOSITION

Table 3-Two-point and after operation

-

OF THE

ULNAR

249

NERVE

discrimination on the tip of the little linger before

Pre-operative

Post-operative

7 (14%) 21(41%) 23 (45%)

28 (55%) 12 (23%) 1102%)

Up to 6 mm. 7-15 mm. Over 15 mm.

Nerve Conduction Velocity in the SulcusNervi Ulnaris-

soC

30

m/set 20

Table 4--Muscle strength before and after operation

MO Ml M2 M3 M4 M5 -

Pre-operative

Post-operative

15 (29%) 6 (12%) 16 (31%) 6 (12%) 3 (6%) 5 (10%)

2 (4%) 4 (8%) g (16%) 10 (19%) g (16%) 19 (37%)

Table !5--Muscle atrophy before and after operation Post-operative Pre-operative None Moderate Severe

15 (29%) 23 (45%) 13 (26%)

31(61%) 16 (31%) 4 (8%)

0 Sensation

Motor

Fig. 2

Comparison of nerve conduction velocities (measured sulcus nervi ulnaris) before and after operation.

transposition. The difference is statistically not significant. The sensory nerve conduction velocity for subcutaneous transposition increased by 26 m./second and for submuscular transposition by 20 m./second (Table 6). The paired t test shows this difference to be p -C0.0292 and thus statistically significant. Table 6-Comparkos of post-operative according to surgical techniques

nerve conduction velocities

Motor

Motor nerve conduction velocity at the elbow level increased from a mean of 34 m./second pre-operatively to 45.8 m./second post-operatively and the sensory antidromal conduction velocity from 8 m./second to 31 m./ second (Fig. 2). The difference in motor and sensory nzrve conduction speeds between the elbow and the forearm exceeded 30% before operation and 12% afterwards. Only a difference of over 30% in nerve conduction velocity is considered pathognomonic of ulnar neuropathy at the elbow (Green, 1988). In the case of subcutaneous transposition the motor n:erve conduction velocity at the elbow increased by 13 m./second and by 10.1 m./second for submuscular

Overall Rating-

at the

Transposition

pre-op.

Submuscular Subcutaneous

30.0 36.3

post-op. 40.1 m./second 49.3 m./second

Sensory pre-op. 5.0 10.0

post-op. 25.0 m./second 36.0 m./second

Electroneurographic findings also correlate with the clinical findings for sensation. Before subcutaneous transposition, three patients (9%) and before submuscular transposition, four patients (21%) had a normal twopoint discrimination. After subcutaneous transposition, 21 patients (65%) had a normal two-point discrimination, while this figure was seven (35%) after submuscular transposition. According to our rating system for overall hand function, 82% of patients had satisfactory or good function after subcutaneous transposition and 62% after submuscular transposition (Fig. 3). Discussion

poor

Fig. 1

(O-2)

moderate

Overall hand function

(3-4) satisfactory

(5

before and after operation.

good (7-S)

Anterior transposition of the ulnar nerve is regarded by many authors as the method of choice (Hagstrbm, 1977; Harrison, 1970; Eaha, 1979; Macnicol, 1979). Subcutaneous transposition is viewed critically by some (Jones, 1979; King, 1959), who feared that the nerve would continue to be prone to trauma due to its superficial position and that it might dislocate back into the sulcus. Formation of a fascial loop to prevent this is rejected because of possible compression (Broudy, 1978), but

250

THE JOURNAL

100

ll-

Post-op Overall Rating According to Surgical Technique

1

OF HAND SURGERY

VOL. 17B No. 3 JUNE 1992

Vogel (1987) found that compression damages sensitive nerve fibres sooner and more severely than it does motor fibres. The long follow-up period disproves the theory of an increased relapse rate due to vulnerability of the nerve after subcutaneous transposition.

Conclusion

64

5:s Points

Fig. 3

Hand function

after operation

by the two surgical

techniques.

Eaton (1980) advocated a “non-compressing” fascioderma1 sling. This study covers 51 patients documented precisely before and after operation by clinical and electroneurographic findings. To compare overall hand function in the various patients, we have combined the four features studied into one rating system. In 86% of cases, a clinical improvement was achieved. After operation 75% of patients were rated satisfactory or good (5-8 points). Two patients were worse and five showed no change. Clinical findings were confirmed by the electroneurographic findings. The choice of surgical method, whether subcutaneous or submuscular anterior transposition, was decided purely by the operator’s preference. Although the patients who underwent submuscular transposition had worse nerve conduction to start with, the difference between the two groups was statistically not significant. Comparison of the two surgical techniques brought a particularly interesting result. The above-mentioned objections to subcutaneous anterior transposition were refuted. After subcutaneous transposition, 82% of patients scored 5 to 8 points, while this was only achieved by 62% of the patients following submuscular transposition. Patients with subcutaneous transposition had good results, especially with regard to sensation. Similarily, a comparison of the nerve conduction velocities showed better results after subcutaneous anterior transposition. This difference is statistically significant for sensory antidromal nerve conduction velocity. In our opinion, submuscular transposition involves more surgical trauma. The lesser improvement in sensation nerve conduction velocity after submuscular transposition may be due to increased compression.

From our experience over 17 years, we regard subcutaneous anterior transposition as the operation of choice for ulnar neuropathy at the elbow. The procedure is simple and causes little morbidity. The results are better than after submuscular transposition, both clinically and electrically.

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35, A-6020 Innsbruck,

0 1992 The

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Society

Austria.

for Surgery

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Surgery,

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