Outcome analysis of cubital tunnel decompression

Introduction

Cubital tunnel syndrome is the second most common nerve entrapment syndrome affecting the upper extremity and is the most common nerve entrapment around the elbow. ¹ Feindel and Stratford ² termed it ‘cubital tunnel syndrome’. Approximately, 75,000 cases of ulnar nerve entrapment syndrome are reported annually in the United States. ³

The cubital tunnel is formed by the cubital tunnel retinaculum that straddles a gap of approximately 4 mm between the medial epicondyle and the olecranon. ⁴ The floor of the tunnel is formed by olecranon, capsule and the posterior band of the medial collateral ligament of the elbow joint. The most important structure in the cubital tunnel is the ulnar nerve. The anatomical arrangement allows the nerve to pass through a relatively constrained path and lies close to the axis of rotation of the joint. Consequently, the nerve is more exposed to stretching and sliding during elbow motion. The unusual anatomy and well-recognised increase in intraneural pressure during elbow flexion play key roles in pathogenesis of cubital tunnel syndrome. ⁵

The few potential sites of compression of the ulnar nerve during its course in the upper limb are the arcade of Struthers, the medial intermuscular septum, the anconeus epitrochlearis, the medial epicondyle, Osborne’s ligament, and, in the forearm, between the two heads of the flexor carpi ulnaris. ⁶

Males are affected more than females which may be attributed to an association with occupational activities. ⁵ Patients present with tingling and numbness of the little finger and ulnar aspect of the ring finger. In delayed presentations, patients may present with weakness of the muscles on the medial side of the hand, resulting in clawing of the ring and little fingers and weakness of interossei muscles. Tinel’s sign may be positive in patients when the nerve is tapped along its path starting proximally to the medial epicondyle. Electrophysiological studies (nerve conduction studies (NCS) and electromyography) are good diagnostic tools to localise the site and the extent of compression although this can potentially cause overestimation of nerve conduction velocity resulting in false-negative results. ⁷

Medical management in the form of physiotherapy, avoiding flexion of the elbow for long periods, night splints in extension, local steroid injections and analgesics are used as standard treatments. Surgery is indicated in patients who suffer persistent signs and symptoms, despite medical management.

Despite the fact that ulnar nerve entrapment syndrome is so common, only a few studies have assessed the outcome of ulnar nerve decompression. Most of the currently available literature compares the result of one surgical technique over the other with still no general consensus on the most appropriate surgical technique for the disease.

This current study assesses the outcome of ulnar nerve decompression. The objectives of the study were to assess the surgical outcome and to review the pre-op symptoms, NCS, co-morbidities and surgical techniques in an attempt to identify prognostic factors, particularly in cases of persistent post-operative symptoms.

Methods and materials

Local institutional committee (Caldicott Guardian) approval was obtained prior to reviewing patient medical records. A total of 174 ulnar nerve decompression operations were identified from our upper limb database. These operations were performed over a six-year period in the three local hospitals between August 2003 and July 2009. Diagnosis was based on clinical symptoms and signs including provocative tests with electrophysiological confirmation.

A structured proforma was created for recording relevant details from patients’ medical records. This was performed between January and May 2010. The demographic details of each patient, their history, predisposing factors and associated problems in the extremity with cubital tunnel syndrome were recorded. Clinical features, provocative tests (Froment’s sign and Tinel’s test), pre-operative nerve conduction study findings, surgical and follow-up details and complications were recorded in the proforma. No patient related scoring system was used. The outcome of the procedure was inferred from the review notes, and the grading system used is illustrated in Table 1.

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Table 1.

Outcome grading.

Completely relieved	Complete relief of his or her symptoms
Improved	Most pre-operative pain has been relieved
Unchanged	Symptoms did not improve
Worse	Symptoms worsened after surgery

Analysis of data was carried out using the Statistical Package for the Social Sciences (SPSS) software (Version 16.0; SPSS Inc, Chicago, IL). Descriptive analysis of the variables was performed, and frequencies were recorded for categorical data. Pearson’s Chi-square test for categorical data was used to investigate the relationship between outcome and the method of surgery. The significance level was set at 5%.

Results

Full notes were available for 136 cases with 60.8% of these cases being male and 39.2% female. The range of age varied from 17 to 84 years, and the age distribution showed a peak in the fourth to sixth decade with a mean age of 51 years. The duration of the onset of symptoms to the date of surgery varied from six months to six years with 68% of cases having had symptoms for over one year prior to surgery (Table 2).

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Table 2.

Duration of symptoms from onset to surgery.

Duration of symptoms	Number of cases	%
<6 months	10	7.35
6 – <12 months	28	20.59
>12 months	84	61.76
Not known	14	10.29

Numbness and paraesthesia in area of ulnar nerve distribution were most common symptoms present in 95% (129) of cases. It was recorded that 75 cases had interossei weakness or hypothenar wasting at the time of decompression whilst in the remainder, status of muscular wasting was not mentioned in case notes. Froment’s sign was present in 30 cases, absent in 76 cases and was not recorded in 30 cases. Tinel’s test was positive in 43 cases, negative in 74 cases and was not recorded in 19 cases. Association of different concomitant conditions with cubital tunnel syndrome in our series is shown in Table 3.

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Table 3.

Concomitant conditions.

Previous carpal tunnel release	(19 cases)
Dupuytren’s contracture	(12 cases)
Alcoholism	(21 cases)
Type 2 diabetes mellitus	(23 cases)

In 12 cases, instability of ulnar nerve was noted pre-operatively and in five cases with instability of ulnar nerve classical pin and needles or numbness in ulnar nerve distribution was not present.

NCS were positive for ulnar nerve compression at the elbow in 95 cases and were negative in eight cases. Of these eight cases with negative NCS, three cases had ulnar nerve instability at the elbow. In 17 cases, NCS were not performed prior to surgery as the consultant surgeon felt the symptom and signs were classical to ulnar nerve entrapment at elbow and proceeded for surgery. In 16 cases, there was no documentation in the notes or in clinic letters if the investigation had been performed.

All procedures were undertaken under general anaesthesia with the patient in a supine position with the arm resting on an arm board. The elbow was flexed and shoulder externally rotated to expose the medial aspect of the elbow. The olecranon and medial epicondyle were marked, and a curvilinear incision was made and then the ulnar nerve was exposed in the cubital tunnel. The ulnar nerve was released both proximally and distally. Cause of compression and any anomalies were noted. If the patient had pre-operative instability or the ulnar nerve was found to be unstable with flexion after decompression, anterior transposition was undertaken. Closure of wound was in layers. Local anaesthetic was infiltrated around the surgical wound for pain relief.

Simple decompression was performed in 110 (80.88%) cases, and anterior subcutaneous transposition was performed in 26 (19.12%) cases. These operations were performed by eight different consultants (including three with special interest in hand surgery) and by trainees under direct supervision. A summary of the causes of compression of the ulnar nerve concluded during the operations is listed in Table 4.

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Table 4.

Causes for compression of ulnar nerve.

Cause	Number of cases (136)	%
Idiopathic	79	58.2
Flexor carpi ulnaris aponeurosis	50	36.7
Arcade of Struthers	7	5.1

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Table 5.

Outcome analysis of ulnar nerve decompression.

Outcome	Number of cases (124)	%
Completely relieved	28	22.6
Improved	79	63.7
Unchanged	13	10.5
Worse	4	3.2

All patients were called for routine out-patient clinic follow-up at six weeks’ post-surgery. At this first review, 70 cases were discharged while 55 required more than one visit. Eleven cases were lost to follow-up and in one case there was no documentation of the outcome in the patient records.

On their final visit to the out-patient clinic, 86% of cases that attended the follow-up (124) reported that their symptoms were either completely relieved or improved. In 13 cases, the symptoms were unchanged. In four cases, the patients felt that they were worse after the operation. Persistence of numbness to some extent was seen in 44 (33.5%) of the 124 cases at final clinic appointment. Complications including scar tenderness or sensitivity were seen in 15 (12%) of the 124 cases. One case developed superficial wound infection which resolved with oral antibiotics (flucloxacillin). Reflex sympathetic dystrophy was seen in one case which was one of the four patients who felt they were worse following operation.

We specifically investigated the outcome following surgery in the group where NCS were negative for ulnar nerve entrapment (eight cases). Three cases in this group had ulnar nerve instability. Of the eight cases with normal NCS, three reported that their symptoms had not changed and one was worse following surgery. Of the group (17 cases) where the NCS were not undertaken as the surgeon felt confident with the classical symptoms and signs and proceeded to surgery, six cases felt that their symptoms were unchanged.

Pearson’s Chi-square test was used to find an association of outcome with the type of surgery undertaken, this was statistically insignificant (p = 0.677). Similarly, no association was found with the presence of co-morbidities and the outcome following surgery (p = 0.778). In addition, it was noted that in patients with duration of symptoms longer than 12 months (84 cases), the outcome was satisfactory in 90% cases.

Discussion

Various surgical ulnar nerve decompression techniques such as simple decompression, ³ anterior subcutaneous transposition, ⁶ submuscular or intramuscular transposition, and medial epicondylectomy ⁸ have shown promising results in the treatment of cubital tunnel syndrome.

This study has shown that ulnar nerve symptoms were completely relieved or improved in 107 (86%) of the 124 cases. The outcome of both simple decompression and anterior subcutaneous transposition was satisfactory and statistically insignificant in our series. These findings were similar to the study by Zlowodzki et al. ³ In their meta-analysis, they noted no difference in clinical outcome scores between simple decompression and transposition for the treatment of idiopathic ulnar nerve compression at the elbow.

The commonest cause found for ulnar nerve compression in the series was a narrowing of the cubital tunnel (idiopathic) as opposed to the presence of space occupying lesions. This finding was different to of Macnicol, ⁹ who found flexor carpi ulnaris aponeurosis to be the most common cause of ulnar nerve compression (50%) followed by idiopathic (25%). The high percentage of unknown causes encountered may be attributed to friction and traction which the nerve undergoes during elbow motion. ¹⁰ There was no statistically significant association of concomitant conditions found in the current study.

The effect of duration of symptoms on clinical outcome has been emphasised by Macnicol ⁹ who suggested that recovery was greatest when surgery was performed within three months of the onset of symptoms. However, the results of the current study were more encouraging and showed that only eight cases with history of more than 12 months had unsatisfactory outcome.

NCS are most commonly used to ascertain diagnosis, site of lesion and the extent of damage. Dunselman and Visser ¹¹ showed the clinical, electrophysiological and prognostic heterogeneity of ulnar nerve entrapment and emphasised on assessment based on both clinical examination and electrodiagnostic studies. Interestingly, in the current series of the eight cases that had normal NCS, 50% reported unchanged symptoms or were worse off following surgery. Although these numbers are very small to draw any firm conclusions they do warn of guarded results in patients with normal NCS and it is recommended to investigate other causes of the symptoms before proceeding to surgery.

Of the group (17cases) where the NCS were not undertaken, 35% of cases felt that their symptoms were unchanged and again this may have been due to concomitant carpal tunnel syndrome or polyneuropathy which was not identified on clinical examination. Again it is recommended to use NCS as a pre-operative tool in all patients to confirm the diagnosis.

The current study suffers from the limitations and drawbacks of a retrospective study. The study included patients who had concurrent surgical procedures in the extremity and also those who had associated systemic problems that could possibly confound the results of ulnar nerve decompression, although analysis at glance does not suggest the same. The criteria employed to describe the outcome was a four-point grading system that was based on follow-up notes but we are confident that this has served its objective in identifying the outcomes in patients.

Conclusion

This is the largest review of the results of ulnar nerve decompression at elbow to date. It has revealed satisfactory results following nerve decompression in 86% of cases. Most cases of cubital tunnel syndrome were idiopathic, and aberrant anatomical findings and space occupying lesions in cubital tunnel are rare. The study noted no difference in patients with co-morbidities when comparing simple decompression surgery to anterior transposition or the duration of symptoms. In patients with symptoms of cubital tunnel syndrome but normal NCS, we advise exploring alternative diagnoses before recommending decompression surgery.

It is hoped that the results of the current study will help general practitioners, junior doctors and surgeons in their management and pre-operative consultation with patients having cubital tunnel syndrome.