Influential factors of surgical decompression for ulnar nerve neuropathy in Guyon’s canal

Abstract

Background:

Guyon’s canal syndrome is nerve compressive pathology which can lead to sensory and/or motor function deficits. This problem is usually difficult to distinguish from cubital tunnel syndrome and relatively less common than cubital tunnel syndrome. This study evaluated the functional results and patient-reported outcomes following decompression of the ulnar nerve in Guyon’s canal.

Methods:

Patients who were diagnosed with Guyon’s canal syndrome confirmed by electrodiagnostic studies and underwent nerve decompression surgery were included in this study. The functional improvement by examining the Froment’s sign, Wartenberg’s sign, static two-point discrimination, and Semmes Weinstein monofilament examination as physical examination scores was evaluated. The visual analogue scale of satisfaction and the disabilities of the arm, shoulder, and hand questionnaire were used for the postoperative patient-reported outcome evaluation.

Results:

From 2003 to 2019, 38 cases had been enrolled with a mean age of 53 years, ranging from 19 to 85 years. There were seven patients with comorbidity of diabetes mellitus and 28 patients who received additional neurolysis combined with the Guyon’s release procedure. There were 19 patients with a good response to surgery and 10 patients with a poor surgical outcome due to persistent paresthesia or weakness. After statistical analysis, it was revealed that several influential factors could have been related to a compromised functional outcome, including a symptom duration of more than 3 months, combination with additional neurolysis of ipsilateral extremity, and/or comorbidity with diabetes mellitus.

Conclusion:

It was concluded that promising functional outcomes after surgical release of ulnar neuropathy in Guyon’s canal could be achieved if the patients did not need additional neurolysis or the symptom duration was within 3 months.

1. INTRODUCTION

The ulnar nerve neuropathy in Guyon’s canal, or Guyon’s canal syndrome, is a less common peripheral neuropathy, which is far less than carpal tunnel syndrome.¹ Patients with Guyon’s canal syndrome display motor weakness of the hypothenar, adductor pollicis, flexor pollicis brevis, and first interosseous, as well as the sensory involvement mostly involving the hypothenar eminence, the fifth digit, and the ulnar portion of the fourth digit.² Physical examinations (PEs) as well as electrodiagnostic and imaging studies are essential to identify the locations of lesions. Diagnosis other than compressive ulnar neuropathy, including the central nervous system, such as cervical disc herniation, acute brachial neuritis, and systemic pathologies, such as multiple myeloma, polyneuropathy, and alcoholism, should be considered.

For treatment options, it has been reported that patients with very mild symptoms, which are defined as minimal numbness, pain, motor weakness, or atrophy of the intrinsic muscles of the hand, to moderate symptoms with a symptom duration of less than 3 months can be treated nonsurgically, including splinting and antiinflammatory medication; patients whose severity of symptoms ranges from moderate to very severe with a symptom duration of at least 2 months should be treated by surgical intervention.³ Although treatment option selections can be judged from the severity and duration of the symptoms and previous treatment management, the functional outcome from literature reviews has been limited, and there is still no information of prognosis of surgical decompression of ulnar neuropathy in Guyon’s canal with additional neurolysis, which is not uncommon in clinical practice.⁴ Meanwhile, it has been reported that there was a discrepancy between the functional outcome and patient-reported satisfaction in some diseases,⁵ and whether this phenomenon can also be observed in surgical decompression of Guyon’s canal is worth studying.

Based on the limited information of the surgical treatment outcome of ulnar neuropathy in Guyon’s canal, a retrospective case series study to evaluate the outcome of surgical decompression of ulnar nerve neuropathy in Guyon’s canal has been conducted. It has been hypothesized there could be some influential factors, such as a poor grade of a preoperative PE result, a prolonged symptom duration before surgery, additional neurolysis of ipsilateral extremity, diabetes mellitus, and a patient’s age, any of which would affect a clinician’s reported functional outcome of surgical decompression of ulnar nerve neuropathy in Guyon’s canal and that of a patient’s. It has also been hypothesized there might be a discrepancy between improved functional outcome and patient-reported outcome statistically.

2. METHODS

2.1. Inclusion and exclusion criteria

The patient database of two medical center hospitals with diagnosis of ulnar nerve neuropathy in Guyon’s canal treated with surgical decompression between 2003 and 2019 was retrospectively searched. The medical records were also reviewed for the following analysis of influential factors. Prior to surgical decompression, all the patients had received conservative treatment with splinting for at least 3 months. The indication of surgical decompression for Guyon’s canal syndrome was for the patients who had moderate to severe symptoms of ulnar neuropathy and had failed from the conservative treatment for at least 3 months.³ Before surgical decompression, an image study and an electromyographic study were also arranged. For the image study, ultrasound was used for all the patients in identifying the possible space-occupying lesions. Magnetic resonance imaging was not routinely performed unless the space-occupying lesion was suspected, yet the ultrasound examinations could not provide the definitive diagnosis.

Inclusion criteria of surgical decompression of Guyon’s canal include (1) progressive weakness or atrophy of the hypothenar muscles, the adductor pollicis, and the flexor pollicis brevis, (2) sensory abnormality involving the hypothenar eminence, the fifth digit, and ulnar portion of the fourth digit, and (3) electromyographic evidence of a Guyon’s canal lesion.⁶ Patients with at least two or three of the inclusion criteria with the electromyographic evidence would be included. Exclusion criteria include central nervous system diseases, cervical radiculopathy, concomitant brachial plexus lesions, noncompressive polyneuropathy, and previous ipsilateral hand or wrist surgery. Patients who lacked at least 1-year follow-up were also excluded. This retrospective study was approved by the institutional review board at the Taipei Veterans General Hospital (TPEVGH IRB No.: 2019-10-009BC).

2.2. Clinical evaluation, functional outcome, and patient-reported outcome assessment

For clinical evaluation, the Froment’s sign, Wartenberg’s sign, the two-point discrimination test, Semmes Weinstein monofilament examination, Duchenne’s sign (a claw hand), and grip strength measurement were evaluated during preoperative and postoperative evaluations. For quantification of the physical exam results, four PEs, including the Froment’s sign, Wartenberg’s sign, the two-point discrimination test, and Semmes Weinstein monofilament examination, as scoring items, were chosen, and each of them equally represented one point; therefore, the PE score ranged from zero point (no abnormal finding) to four points (abnormal findings in all PEs).

The disabilities of the arm, shoulder, and hand (DASH) score and visual analogue scale (VAS) of satisfaction of Guyon’s canal release surgery were utilized as the bases for the patient-reported outcome. A poor patient-reported outcome was defined as the VAS of satisfaction ranging from zero to two, and a good outcome was defined as the VAS of satisfaction ranging from eight to 10.⁷ For the following subgroup analysis, a patient’s age, diabetes mellitus, additional neurolysis, and the symptom duration before surgery were chosen as the influential factors. The group whose age was over 60 was defined as the elderly group, and the group whose age was younger than 60 was defined as the nonelderly group; additional neurolysis was defined as ipsilateral surgical decompression for peripheral neuropathy other than ulnar nerve neuropathy in Guyon canal, such as carpal tunnel syndrome and cubital tunnel syndrome.

2.3. Surgical technique

Surgical decompression of Guyon’s canal based on previous literature presentations⁸ was performed under general anesthesia, and the patient was placed in the supine position with the pneumatic tourniquet control. Loupe magnification was routinely used for all the operations. The incision was made longitudinally from the wrist crease with a mild curve on the radial border of the hypothenar eminence. It extended proximally from the wrist about 3 cm with a Brunner type incision crossing the wrist crease and then went along the radial border of the flexor carpi ulnaris. The tight fascia around the wrist crease was released. The roof of the Guyon’s canal was released carefully from the margin of the hamate hook. The superficial sensitive branches and the deep branch of the ulnar nerve were then identified, and the ulnar neurovascular bundles were protected well with a vessel loop during the whole surgery. The fascia/ligament was pulled by the right-angle forceps and was incised in a stepwise manner and so were the compression lesions, until the Guyon’s canal was completely released. After the decompression of Guyon’s canal was done completely, the pneumatic tourniquet would be released, and hemostasis was done carefully. Finally, the incision wound was closed by 4-O nylon and dressed heavily. A soft short arm splint was applied immediately after the surgery for at least 3 days.

As for the patients combined with ipsilateral carpal tunnel syndrome or cubital tunnel syndrome, a carpal tunnel release or cubital tunnel release was performed at the same time if the surgical release was indicated due to the failure from conservative treatment and electromyographic evidence.

2.4. Postoperative protocols

After the surgery, all the patients were evaluated every 2 weeks in the first month, every 3 months in the first year, and then every 6 months thereafter. An annual follow-up was arranged if the neurogenic recovery became stagnant after 2 years. Additional visits were arranged if needed.

2.5. Statistical analysis

Continuous variables were reported as mean ± SD. For statistical analyses, a p value <0.05 was considered statistically significant in the Wilcoxon signed-rank test for comparison of the PE/DASH score between the preoperative status and postoperative status. The Mann-Whitney U test was used for the subgroup comparison of the VAS of satisfaction. The one-way analysis of covariance (ANCOVA) was used for the subgroup analysis of the correlation between the PE/DASH score and suspected influential factors, including the patients’ ages, diabetes mellitus, additional neurolysis, and symptom durations before the surgery. The correlation between the PE/DASH score and the VAS of the satisfaction score was verified by the Fisher’s exam test. All the static analyses were done by the IBM SPSS Statistics for Windows, Version 25.0 (IBM Corp., Armonk, NY).

3. RESULTS

There were a total of 38 patients in this retrospective study, 27 males and 11 females. There were 24 patients who suffered from their dominate hands. The mean age was 53 years, ranging from 19 to 85 years, SD: 16.2, including seven wrists diagnosed with diabetes mellitus. The mean duration from the beginning of the symptoms to the surgical decompression was 16.2 months, ranging from 3 to 60 months, SD: 14. The mean follow-up was 61.6 months, ranging from 12 to 197 months, SD: 60. Before the surgery, the mean PE score was 3.3, ranging from 2 to 4, SD: 2.0, and the mean DASH score was 31.8, ranging from 8.3 to 53.3, SD 13.3. After the surgery, there were 27 patients with an improved PE score with the mean of 1.37, ranging from 0 to 4, SD 1.7, and 34 patients with an improved DASH score with the mean of 17, ranging from 0 to 45.8, SD 13.3. For the VAS of satisfaction, there were 10 patients with a poor patient-reported outcome and 19 patients with a good patient-reported outcome with the mean of 6, ranging from 0 to 10, SD 3.5. For the patients with a poor patient-reported outcome, there was one patient with an improved PE score and seven patients with an improved DASH score. Furthermore, the Fisher’s exact test showed no statistic correlation between the improved DASH/PE score and good patient-reported outcome (p > 0.05). No serious complication, such as deep infection or iatrogenic neurovascular injury, was noted. The demographic and clinical data were listed in Table 1.

Table 1.

Patient demographic information and patient reported outcome, functional score

Demographic data
Patient volume, N	38
Mean duration from injury to surgery, mo (range; SD)	15.4 (3-60; 14.7)
Mean age, y (range; SD)	53 (19-85; 16)
Gender, N (male to female)	27/11
Hand side, N (right to left)	25/13
Dominant hand, N (percentage of all cases)	23 (61)
Etiology of ulnar neuropathy in Guyon’s canal, N
Idiopathic	35
Ganglion cyst	3
Clinical and patient-reported outcome
Physical examination score
Preoperative status, N (range, SD)	3.26 (2-4; 1.0)
Postoperative status, N (range, SD)	1.37 (0-4; 1.7)
DASH score
Preoperative status, N (range, SD)	31.8 (8.3-53.3; 13.3)
Postoperative status, N (range, SD)	17 (0-45.8; 13.3)
VAS of satisfaction, N (range; SD)	6 (0-10; 3.5)

DASH = disabilities of the arm, shoulder, and hand; VAS = visual analog scale.

To further evaluate the influential factors of the surgical decompression of Guyon’s canal, the patients’ ages, comorbidity of diabetes mellitus, symptom durations before the surgery, and additional neurolysis in ipsilateral extremity were included for further subgroup analysis (Table 2). Overall, it was noted that there was statistical improvement between the preoperative PE/DASH score and postoperative PE/DASH score in every subgroup analysis (p ≦ 0.05) except the patients with diabetes mellitus (p = 0.74), and there was statistical correlation between diabetes mellitus and the DASH score (p < 0.01) from the one-way ANCOVA. Meanwhile, there were significant difference s in the VAS of satisfaction in the subgroup comparison of diabetes mellitus, symptom durations before the surgery, and additional neurolysis (p ≦ 0.05). The detailed subgroup analysis was listed in Table 2.

Table 2.

Subgroup analysis of patient series

Subgroup entity	Case number	Physical examination score		p a	p c	DASH score		p a	p c	VAS of satisfaction (mean ± SD)	p b
		Preoperative status (mean ± SD)	Postoperative status (mean ± SD)			Preoperative status (mean ± SD)	Postoperative status (mean ± SD)
Age, y					0.067				3.44		0.11
>60	12	3.3 ± 1.0	2.1 ± 1.8	0.03		29.5 ± 12.9	19.0 ± 9.4	0.04		4.8 ± 3.5
≦60	26	3.2 ± 1.0	1.0 ± 1.5	<0.01		32.9 ± 13.6	16.1 ± 14.9	<0.01		6.6 ± 3.4
Diabetes mellitus					0.087				0.001		0.05
Yes	7	3.7 ± 0.8	2.6 ± 0.6	0.10		33.6 ± 8.4	31.1 ± 7.3	0.74		3.9 ± 2.9
No	31	3.2 ± 1.0	1.1 ± 1.6	<0.01		31.4 ± 14.2	13.9 ± 12.4	<0.01		6.5 ± 3.4
Additional neurolysis					--				--		<0.01
Yes	28	3.3 ± 1.0	1.9 ± 1.7	<0.01		33.0 ± 10.9	20.2 ± 13.7	<0.01		4.9 ± 3.3
No	10	3.2 ± 1.0	0	<0.01		28.5 ± 18.6	8.2 ± 7.4	<0.01		9.2 ± 0.9
Symptom duration before surgery, mo					--				--		<0.01
>3	24	3.3 ± 1.0	2.1 ± 1.7	<0.01		31.2 ± 12.0	21.6 ± 14.2	<0.01		4.5 ± 3.4
≦3	14	3.1 ± 1.0	0.1 ± 0.5	<0.01		32.9 ± 15.7	9.3 ± 6.9	<0.01		8.7 ± 1.0

DASH = disabilities of the arm, shoulder, and hand; VAS = visual analog scale.

^aWilcoxon Signed-Rank test between preoperative status and postoperative status.

^bMann-Whitney U test in subgroup comparison.

^cOne-way ANCOVA in subgroup comparison.

^dFailed from test of homogeneity.

4. DISCUSSION

Ulnar neuropathy in Guyon’s canal is a relatively unusual yet well-recognized peripheral neuropathy in upper extremity. From this study, diabetes mellitus posed as an influential factor affecting both the clinical results and patient-reported outcome after the surgical decompression of ulnar nerve neuropathy in Guyon’s canal, and there was indeed a discrepancy between functional improvement and patient-reported satisfaction in the case series in this study.

The etiology from the series comprised ganglion cysts and idiopathic causes. Causes of compression of the ulnar nerve are multiple according to literature reviews, including repeated microtrauma,⁹ fractures of the carpal bone,¹⁰ abnormal muscle insertions or fibrous bands,¹¹ and benign lesions such as ganglion cysts and lipomas.² Although there was not a large number of ulnar nerve neuropathy in Guyon’s canal, there were some rare case reports in literature reviews.^12–16 Some studies estimated that 30% to 40% of ulnar nerve neuropathy in Guyon’s canal was caused by ganglion cysts.¹⁷ In this study, 7.9% of the case series resulted from ganglion cysts. This difference might be caused by the limitation of the retrospective case series study. Nevertheless, the improvement of the PE score and DASH score and the high VAS of satisfaction were noted in the cases caused by ganglion cysts, which was compatible with those in the published case report.¹⁸ For the ages of patients, there were other peripheral compression neuropathy reports that there were a higher prevalence of severe carpal tunnel syndrome and a lower success rate among elderly patients due to delayed recovery after the release surgery.¹⁹ However, there seemed to be no significant difference between the elderly group and nonelderly group in our case series of ulnar nerve neuropathy in Guyon canal.

There were seven cases with comorbidity of diabetes mellitus. A poor postoperative function outcome with a low VAS of satisfaction was noted. The diabetes mellitus disease impaired the peripheral nerves in nerve axonal degeneration.²⁰ In cases with comorbidity of diabetes mellitus who received carpal tunnel release, no significant difference was noted in improvements of all various outcomes except sensory conduction velocities after the carpal tunnel syndrome (CTS) surgery between diabetic and nondiabetic patients. Better diabetic neuropathy care is recommended to achieve better sensory recovery after the CTS surgery in diabetic patients.²¹ However, in our case series, ulnar nerve neuropathy with Guyon’s release in the diabetic patients had worse outcome.

Additional neurolysis was not uncommon in our case series. Eleven patients received carpal tunnel release, and 22 patients received cubital tunnel release; many patients were workers whose elbow symptoms could affect their work performance. The possibility of coexisting carpal tunnel syndrome or double crush syndrome would exacerbate the patients’ symptoms.⁴ It has been reported that there was a high possibility of an anatomic connection of the ulnar and median nerves at the wrist level, thereby resulting in mutual interference when each of them suffered from compression neuropathy, and thus it may be helpful to further ease ulnar nerve neuropathy by carpal tunnel release.²² Although the release of the combined median and ulnar nerve compression at the wrist level did not show superior outcomes for the patients who had the Guyon’s canal problem and was treated separately, it is still worth suggesting using a combined release due to the fact that the median nerve compression in the carpal tunnel has already been built. In addition, serious complications of combined release were not noticed in our case series.

Seror²³ found cases with ulnar neuropathy at the wrist level would be less severe if they were sport related rather than those that were nonsport related. The reason could be that athletes are more sensitive to symptoms and changes in their physical performance, and they are prone to have early detection and diagnosis, thereby receiving medical treatment at an early stage. This finding might explain that most patients with shorter symptom durations and better functional recovery after surgical decompression in our case series were young workers who were also sensitive to symptoms and changes in their physical performance. Meanwhile, the symptom durations before diagnosis would also influence the surgical outcome in cases with carpal tunnel syndrome.²⁴

The limitation of this study is its retrospective nature and a small number of cases. In addition, the involvement of multiple surgeons could also cause bias.

In conclusion, for surgical decompression of ulnar nerve neuropathy in Guyon’s canal, it was showed in our results that patients with earlier treatment could have better functional recovery; patients diagnosed with diabetes mellitus, ulnar neuropathy in Guyon’s canal combined with double crush syndrome or carpal tunnel syndromes, and prolonged symptom durations before surgery had inferior prognosis. There was also a discrepancy between the functional outcome and patient-reported satisfaction in the surgical decompression for Guyon’s canal release. Nevertheless, a surgical release of Guyon’s canal is a reliable procedure, especially for patients who are diagnosed early but do not respond to conservative treatment.

ACKNOWLEDGMENTS

This work was supported, in part, by grants from the Taipei Veterans General Hospital (106-2314-B-075-060), Taipei City Hospital-Zhongxiao Branch (110-38), and the Ministry of Science and Technology (MOST105-2314-B-075 -049).