Abstract
Transfer of the abductor pollicis longus tendon to restore index abduction was performed simultaneously with ulnar nerve decompression in severe cases of cubital tunnel syndrome. Eighteen elbows in 18 patients were evaluated with an average follow-up period of 46 (range 12–120) months. The status of the ulnar nerve palsy was evaluated by the Yasutake’s scoring method. The mean score improved from 48 points pre-operatively to 78 points at final follow-up (maximum score 100 points). Pinch strength improved from 39% of the opposite side pre-operatively to 81% finally and it reached a plateau one year postoperatively. Despite this improvement in pinch strength, atrophy of the interosseous muscle did not disappear in nine of 12 patients with a follow-up of more than two years. All patients were satisfied with the results of increased strength and stability in pinching ability. No complications occurred.
Keywords
Pinch is a principal hand function. Usually, disturbance of pinch movement is the main motor problem for patients in severe cubital tunnel syndrome, with clawing being less intrusive on hand function. Saito et al. (1989) showed, in an electrophysiological study, that the abductor pollicis longus and first dorsal interosseous work together to spread the thumb and fingers and, thus, achieve powerful pinch between the thumb and index finger. Consequently, the first dorsal interosseus muscle is the most important muscle involved in pinching, which is easily impaired by weakness of this muscle. For the thumb movement in pinching, the flexor pollicis longus muscle plays a more important role than the adductor pollicis muscle and often compensates for weakness of the latter. Therefore, in ulnar nerve motor palsy, early restoration of abduction of the index finger, rather than adductorplasty, is most important for the patient in terms of strength and stability of pinch. Tendon transfer can be used simultaneously with primary ulnar nerve surgery in patients who desire a quick recovery from impaired pinch movement.
In this study, we evaluated the results of abductor pollicis longus transfer (Neviaser et al., 1980), to restore index finger abduction, when performed simultaneously with ulnar nerve decompression, in 18 severe cases of cubital tunnel syndrome.
PATIENTS AND METHODS
Operative procedures
The abductor pollicis longus tendon transfer was performed as described by Neviaser et al. (1980). One of the slips of the abductor pollicis longus muscle which was not inserted onto the first metacarpal was identified at the first dorsal compartment and elongated, usually with the palmaris longus tendon using a Pulvertaft weave. The elongated tendon was then passed through a subcutaneous tunnel and anchored to the insertion of the first dorsal interosseous tendon (Fig 1). The tendon transfer was tensioned at surgery to abduct the index finger slightly. Postoperatively, a plaster cast was applied from the elbow to the tip of the index finger for four weeks. Thereafter, exercises of pinch movement were begun.
The operative procedure for ulnar nerve decompression was a simple decompression in nine cases and a simple decompression and a partial medial epicondy-lectomy in nine cases. The operative procedure for the ulnar nerve was based on the operative findings: if the ulnar nerve moved anteriorly onto the medial epicondyle when the elbow was flexed beyond 90°, then a partial medial epicondylectomy was performed (Amako et al., 2000). If not, simple decompression only was performed.
We performed this tendon transfer simultaneously with decompression surgery of the ulnar nerve on 21 elbows in 20 patients with severe cubital tunnel syndrome between 1993 and 2004. Of these patients, 18 elbows of 18 patients whose follow-up period was more than one year were evaluated. The average follow-up period was 46 (range 12–20) months. The cases included 14 men and four women . Their average age at operation was 59.5 (range 42–76) years. Four cases demonstrated severe ulnar nerve palsy because of humeral malunion, or nonunion. Cervical spondylosis was also present in all cases and diabetes in two cases. Their working status was as follows: clerks: 6; manual workers: 7; retired manual worker: 1; soldier: 1; housewives: 3.
The upper limb which underwent surgery was the right in nine and the left in five cases. Bilateral surgery was carried out in four patients. Among the bilateral cases, ulnar nerve decompression and tendon transfer were performed on the worst (right) side in one case (case 15), ulnar nerve decompression was performed on both sides but tendon transfer only on the worst (right) side in two cases (cases 5 and 16) and ulnar nerve decompression and tendon transfer were performed on both sides in one case (case 7). In this latter case, the follow-up period of the left side was less than one year, so the left side was excluded from the evaluation. Therefore, the right side was evaluated in 13 cases and the left side in five cases.
The pre-operative and postoperative status of the ulnar nerve palsy was evaluated by Yasutake’s scoring method for cubital tunnel syndrome (Yasutake, 1983) (Table 1). This method assigns a maximum of 100 points to the disability, based on the following symptoms: prickling sensation and pain (30 points), muscle weakness and atrophy (30 points), deformity (20 points) and sensory disturbance (20 points).
Key pinch strength was measured with the middle, ring and little fingers fully flexed, so that they could not support the index finger. The key pinch strength of the assessed hand was scored as a percentage of the same for the other side. Patients in whom both sides were affected were excluded from the evaluation of pinch strength.
The degree of first interosseous muscle atrophy was evaluated as obvious, slight or none in all patients preoperatively and at final follow-up. The meaning of each number was as follows: 1: obvious muscle atrophy; 2: slight atrophy; 3: no atrophy.
Subjective assessment of patient satisfaction, especially with increase of strength and stability of pinch, was carried out. Enquiry was made as to return to previous occupation in those working and improvement, or otherwise, of activities of daily living.
Complications both at operation and in the use of the hand for pinch were recorded. Tightness or slackness of the transferred tendon was checked.
A paired t-analysis was used for the statistical analysis of the Yasutake score and the key pinch strength changes. The differences were regarded as significant when the P-value was less than 0.05.
RESULTS
All patients had two, or more, abductor pollicis longus tendon slips: four patients had two slips, 12 had three slips and two had four slips. Therefore, the tendon transfer described by Neviaser et al. (1980) was possible in all cases.
Evaluation of the results in 18 elbows in 18 patients is shown in Table 2.
The mean Yasutake score (n = 18) significantly improved from 48 (SD 11) points pre-operatively to 78 (SD 10) points at final follow-up (P< 0.0001). The score reached a plateau two years postoperatively, with the score changing to 67 (SD 13) at six months, 72 (SD 13) at one year, 79 (SD 13) at two years, and 78 (SD 11) at three years (Fig 2).
Key pinch strength (n = 13) significantly improved from 36 (SD 15)% of that of the contralateral side pre-operatively to 80 (SD 17)% at final follow-up (P< 0.0001). Key pinch strength reached a plateau one year postoperatively, with the strength changing to 58 (SD 11)% at six months, 75 (SD 8)% at one year, 84 (SD 7)% at two years, and 80 (SD 18)% at three years (Fig 3).
The original atrophy of the first dorsal interosseus muscle did not disappear in nine of 12 patients at the final follow-up of more than two years after surgery. Obvious muscle atrophy was observed in nine patients, slight atrophy in two patients and no atrophy in only one patient. Six cases were excluded from the evaluation because the follow-up period was less than two years. Before surgery, all patients had presented severe and obvious atrophy of the first dorsal interosseous muscle.
All patients were satisfied with the results, especially with the increased strength and stability in pinch. All patients returned to their previous occupations. All reported substantial improvement of their activities of daily living.
No complications were observed. The tendon transfer was tensioned at surgery to abduct the index finger slightly. Having used this degree of tensioning, we experienced no cases of over-correction, leaving the index finger in an abducted position at rest.
Although it is not strictly a complication of this procedure, this study identified a septum separating the abductor pollicis longus tendon from the extensor pollicis brevis tendon within the first dorsal extensor compartment in eight out of 18 patients in which the tendon transfer was carried out. The incidence of this septum has previously been reported byLeslie et al., 1990 as 34% and by Mahakkanukrauh and Mahakka-nukrauh (2000) as 77.5%. Therefore, surgeons must watch for its existence when exploring this compartment, for whatever reason.
Case report (Case 11)
The patient was a 76 year-old male retired car mechanic. He was referred to us from a nearby clinic with a complaint of paraesthesiae and a loss of fine movement of the right hand. His right first dorsal interosseous muscle was in a severely wasted state (Fig 4a). He had a cubitus valgus deformity of the left elbow (30°) due to a probable supracondylar fracture of the right humerus at the age of ten. The range of motion of the left elbow was −40° in extension and 100° in flexion. An X-ray showed severe osteoarthritic changes in the elbow. He also had cervical spondylosis at the C4/5/6/7 level. He was diagnosed as having a severe cubital tunnel syndrome. An electrophysiological study confirmed the diagnosis. The pre-operative Yasutake’s score was 35 points and the pinch strength was 34% of the contralateral side.
Neurolysis of the ulnar nerve and Neviaser’s tendon transfer procedure were performed. The abductor pollicis longus had three tendon slips. Postoperatively, ulnar nerve palsy was improved, but the first dorsal interosseous muscle atrophy did not recover at all. However, he obtained a strong pinch and good dexterity again. The Yasutake score was 60 points and the pinch strength was 100% of the contralateral side 54 months postoperatively. He was satisfied with the increased strength and stability of pinch (Fig 4b).
DISCUSSION
Neviaser and his colleagues observed that 54 of 56 cadaver wrists had two or more tendinous slips of the abductor pollicis longus muscle (Neviaser et al., 1980). Khoury et al. (1991) reported that 76% of the 54 hands which they studied had two or more slips of the abductor pollicis longus muscle. Gonzalez et al. (1995) reported that multiple slips of the abductor pollicis longus tendons were present in 38 of 66 cadaver hands and accessory slips were observed to insert into the trapezium and thenar musculature. In our study, all patients had two or more tendon slips of the abductor pollicis longus muscle. Therefore, tendon transfer of one slip of the abductor pollicis longus tendon, to restore first dorsal interosseous muscle function, is likely to be feasible in most cases in which this tendon transfer is indicated.
Prior to 1980, several alternative procedures had been described to restore first dorsal interosseous muscle function, including transfer of the extensor indicis proprius, the flexor digitorum superficialis of the ring finger and the extensor pollicis brevis (Bruner, 1948; Calandruccio and Jobe, 2003; Graham and Riordan, 1947; Omer, 1988). The extensor indicis proprius is not ideal because the muscle force is weak and the force direction is parallel to the second metacarpal. Sacrificing the flexor digitorum superficialis of the ring finger reduces grip strength. The extensor pollicis brevis is better spared because the muscle plays an important role in stabilising the interphalangeal joint of the thumb.
Since the original paper by Neviaser et al. (1980), satisfactory use of the procedure in cases of ulnar nerve palsy has been reported in 38 cases (Futami et al., 1989; Nemoto et al., 1997; Saito et al., 1989; Takahira et al., 1994). This study confirms the usefulness of this procedure as key pinch strength was improved from 36% to 58% of that of the contralateral hand within six months of surgery and to 75% within one year. So, pinch movement was restored very quickly after operation. Conversely, the original atrophy of the first dorsal interosseus muscle did not disappear at all in nine of 12 cases in whom the follow-up period was more than two years and abduction of the index finger was regained solely by the tendon transfer in these nine cases. Because some people say that the muscle atrophy may recover over a long time period after ulnar nerve decompression surgery, we evaluated the state of the muscle atrophy more than two years after surgery and confirmed that severe muscle atrophy of the first dorsal interosseous did not recover after ulnar nerve decompression in this time period in a considerable proportion of our cases and that tendon transfer was, therefore, necessary.
This tendon transfer produces strong abduction of the index finger, increasing the strength and stability of pinch, making it very useful in restoring pinch in severe cases of cubital tunnel syndrome. Simultaneous use of the tendon transfer at the time of ulnar nerve decompression is logical as it achieves a quick recovery of the disturbed pinch movement in all cases and the only possibility of this at all in those whose first dorsal interosseous palsy does not recover.
This procedure is used, mainly, in cases with complete paralysis of the first dorsal interosseous muscle, in which there is little, or no, possibility of recovery. However, it is also applicable for cases in which there is a possibility of recovery of the muscle because the tendon transfer does not interfere with the first dorsal interosseous muscle in any way. The procedure is also useful for the treatment of a substantial loss of the first dorsal interosseous muscle as a result of trauma or tumour resection (Nemoto, 2002).