The prospective, randomized clinical study, which was approved by the Investigational Review Board at our medical center, included fifty hands (forty-four patients) that were treated operatively by one of us (N. L. H., III) from November 1986 through July 1989. The criteria for inclusion were clinical signs and symptoms of dysfunction of the median nerve due to compression in the carpal canal that were not responsive to non-operative treatment as well as an electromyogram that demonstrated fibrillations suggesting an advanced degree of nerve compression. Patients who either had had a previous operation in the carpal canal or could not fulfill the follow-up requirements were excluded.
The hands were randomly chosen to receive one of two types of treatment: operative decompression of the median nerve by longitudinal incision of the transverse carpal ligament alone (Group 1) or operative decompression of the median nerve and longitudinal opening of the epineurium in the region of the carpal canal (Group 2). The hands were randomized by the placement of numbers 1 through 50 (to represent the hands) in a bin. A second bin contained twenty-five epineurotomy tags and twenty-five non-epineurotomy tags. A number was drawn from the first bin and was matched to a tag drawn from the second bin. Thus, twenty-five hands were randomly selected for an epineurotomy and twenty-five, for treatment without an epineurotomy. Because each hand was considered separately, with no regard for which procedure (if any) was done on the contralateral side, some patients who had symptoms in both hands had the same procedure performed on both and some had an epineurotomy on one side but not on the other.
The patients were evaluated twelve months postoperatively by a physician who was blinded with regard to the treatment. In addition, all of the patients had an electrophysiological study performed, both preoperatively and at twelve months postoperatively, by an independent physician (J. W. S.), who also was blinded to the treatment.
Twenty-two patients (twenty-five hands) were randomly assigned to Group 1 (no epineurotomy). There were fourteen women and eight men, and the average age was 65.7 years (range, thirty-nine to 100 years). Associated medical conditions included hypertension (three patients), diabetes mellitus (two patients), and arteriosclerotic cardiovascular disease (one patient). Nineteen hands had pain, altered sensibility, paresthesia, and loss of manual dexterity, and the remaining six hands had three of the four symptoms. The average duration of symptoms was 2.3 years (range, three months to fourteen years). The average duration of follow-up was twenty months (range, twelve to seventy-six months).
Twenty-two patients (twenty-five hands) were randomized to Group 2 (epineurotomy). There were twelve women and ten men with an average age of sixty-four years (range, thirty-eight to eighty-eight years). Four patients also had hypertension, one had diabetes mellitus, and one had arteriosclerotic cardiovascular disease. Fifteen hands had pain, altered sensibility, paresthesia, and loss of manual dexterity, and ten hands had three of the four symptoms. The average duration of symptoms was three years (range, three months to ten years). The average duration of follow-up was 16.7 months (range, twelve to forty-eight months).
On physical examination, the average two-point discrimination in the distribution of the median nerve in Group 1 was 7.0 millimeters (range, three to more than fifteen millimeters), as measured with static two-point-discrimination techniques. The average strength of the abductor pollicis brevis muscle, as determined by manual muscle-testing in opposition6, was 3.9 (range, 3 to 5) of 5. Tapping over the median nerve at the wrist elicited the Tinel sign11 in sixteen hands and the Phalen maneuver11 of flexing the wrist for a period of one minute elicited symptoms in fifteen hands.
The average two-point discrimination in the distribution of the median nerve in Group 2 was 6.9 millimeters (range, three to more than twelve millimeters). The average strength of the abductor pollicis brevis muscle was 3.7 (range, 3 to 5) of 5. The Tinel sign was elicited in seventeen hands, and the Phalen maneuver elicited symptoms in seventeen hands.
The preoperative electrophysiological testing in Group 1 revealed an average distal sensory latency of 5.1 milliseconds (range, 4.0 milliseconds to no response) (3.8 milliseconds is the upper limit of normal) in the fifteen hands in which it could be measured. Of note is that, in ten hands, the distal latencies were compromised to the point that they could not be measured. Preoperative electromyography revealed fibrillations in the abductor pollicis brevis and opponens pollicis muscles.
The preoperative electrophysiological testing in Group 2 revealed an average distal sensory latency of 5.2 milliseconds (range, 4.0 milliseconds to no response) in the sixteen hands in which it could be measured. The distal latencies in nine hands were so compromised that they could not be measured. Preoperative electromyography revealed fibrillations in the abductor pollicis brevis and opponens pollicis muscles.
Operative Technique
All of the operative procedures were performed on an outpatient basis with local infiltration of anesthesia supplemented with parenteral sedation. All of the procedures were performed by the same surgeon with use of a standardized operative technique14 under pneumatic tourniquet control. The incision was made in the hypothenar area just ulnar to the mid-palmar crease, with an attempt made to preserve the palmaris brevis muscle whenever possible. The distal edge of the transverse carpal ligament was identified and divided longitudinally.
At this point, if the hand had been randomized to Group 1, the wound was copiously irrigated with sterile saline solution and only the skin was sutured. A standardized postoperative dressing, which included a volar plaster splint, was applied. If the hand had been randomized to Group 2, the epineurotomy was performed under 3.5-times operative-loupe magnification with the use of micro-forceps to open the epineurium on the ulnar side of the nerve, with care being taken not to disturb any fascicular areas of the nerve. The wound closure and the postoperative dressing were the same as those for Group 1. A flexor tenosynovectomy was not performed on any hand in this study.
Follow-up
The dressing was removed ten days postoperatively, at which time the patient was taught specific rehabilitation exercises. The patient was seen again at one week, six weeks, six months, and twelve months postoperatively. An analysis of the symptoms, as well as of objective findings compared with those seen preoperatively, was conducted by a physician who was blinded with regard to the type of operative treatment. Twelve months postoperatively, all patients had a repeat electrophysiological test performed by a physician who was also blinded with regard to the operative treatment. The data were analyzed statistically, by an independent examiner, with use of the chi-square and t tests.
Because the data were incomplete for both groups at the six-week and six-month follow-up examinations, the results of the study were based on the data obtained at the twelve-month follow-up evaluation, which were complete for all of the patients.
At the twelve-month follow-up evaluation, fifteen hands in Group 1 and fourteen hands in Group 2 no longer had any symptoms referable to the dysfunction of the median nerve. With the numbers available for study, we could not show this difference to be significant.
On physical examination, the average two-point discrimination in the distribution of the median nerve was 5.1 millimeters (range, three to eleven millimeters) in Group 1 and 4.7 millimeters (range, three to ten millimeters) in Group 2. This difference could not be shown to be significant. The strength of the abductor pollicis brevis muscle in Group 1 had improved to an average of 4.3 (range, 3 to 5), compared with an average of 4.2 (range, 3 to 5) in Group 2. This difference also was not shown to be significant. Six hands in Group 1 and eleven hands in Group 2 had a positive Tinel sign11. The Phalen maneuver11 elicited symptoms in two hands in Group 1 and in four hands in Group 2. Again, these differences were not shown to be significant.
The twelve-month results of the electrophysiological tests revealed an average sensory latency of 4.1 milliseconds (range, 3.4 to 5.0 milliseconds) for the twenty-four hands in Group 1 for which it could be measured, as compared with 4.1 milliseconds (range, 3.2 to 5.3 milliseconds) in Group 2. Only one hand in Group 1 still had unmeasurable latency, whereas none of the hands in Group 2 did. This difference was not shown to be significant.
We detected no significant difference between the outcome for the hands treated with division of the transverse carpal ligament alone and that of the hands that had had adjuvant epineurotomy of the median nerve.
The t test showed no significant differences between the two groups at twelve months (p > 0.05), and chi-square analysis showed that the proportions in Groups 1 and 2 were not independent of each other at twelve months.
Several authors have addressed the issue of nerve manipulation, especially epineurotomy, in relation to the outcome of decompression of the median nerve in the carpal canal3,8. Duncan et al. polled members of the American Society for Surgery of the Hand and found that 369 (79 per cent) of the 467 who completed the survey performed a linear epineurotomy through the constricted area of the median nerve during carpal tunnel release.
Foulkes et al. performed a prospective clinical study of thirty-six wrists (thirty-three patients) that had been randomized to operative treatment of carpal tunnel syndrome with or without an epineurotomy. The patients were evaluated preoperatively and at six or twelve months postoperatively, with fifteen evaluated at both postoperative time-points. Sensory testing showed over-all improvement postoperatively in both groups. The conclusion of that study and ours was that the addition of an adjuvant epineurotomy, although safe, is of no clinical benefit. The study by Foulkes et al. differed from ours in that not all of the patients had electromyographic changes indicative of denervation of the thenar muscles. However, in both studies, epineurotomy did not cause any significant difference in the outcome of treatment of primary carpal tunnel syndrome.
The use of adjuvant manipulation of the median nerve has been questioned. Curtis and Eversmann found that internal neurolysis resulted in a return of sensation and improvement in thenar function in patients who had had constant sensory loss and atrophy or palsy of thenar muscles. However, Gelberman et al. found no significant difference in outcome between patients who had had an internal neurolysis and those who had not.
On the basis of the results of the present study, we concluded that a gain of muscle strength after operative decompression of the carpal canal is possible, although such a gain may not be evident for at least twelve months after the treatment of an advanced lesion. Second, and most importantly, there is no difference in outcome when an adjuvant epineurotomy is performed compared with when a ligament release is performed alone for the most advanced forms of carpal tunnel syndrome.
NOTE: The authors thank Jean Piccicuto, M.S., chairperson and statistical consultant at Alvernia College, for performing the statistical analysis.