Clinical results of carpal tunnel Re-release revision surgery and synovial wrap for recurrent carpal tunnel syndrome

Abstract

Introduction

Carpal tunnel syndrome is a challenging condition when conventional carpal tunnel revision surgery fails to alleviate symptoms. This study aims to assess the outcomes of combining carpal tunnel revision surgery with a synovial wrap for cases of recurrent carpal tunnel syndrome in patients who had adhered median nerve, with a minimum 1-year follow-up.

Patients and methods

A retrospective analysis was conducted on 10 patients (mean age: 73.7 years, nine females and one male) who underwent treatment for recurrent carpal tunnel syndrome. The approach involved carpal tunnel revision surgery coupled with a median nerve synovial wrap. Patients were followed up for a minimum of 1 year. The procedure involved harvesting a 3.5 cm × 4 cm section of the flexor synovial membrane with a distal ulnar pedicle, which was then wrapped around the adherent site of the median nerve. Physical assessments included the pain visual analogue scale (VAS), Tinel sign in the carpal tunnel, thenar muscle atrophy, the Semmes-Weinstein monofilament test (SW test), manual muscle test (MMT) as assessed on the 5-point British Medical Research Council Scale (5/5, normal; 0/5, absent), and the Disabilities of the Arm, Shoulder, and Hand (Quick DASH) questionnaire. The physical variables were compared before surgery and at final follow-up.

Results

All patients showed some improvement in SW test. The MMT for the abductor pollicis brevis showed significant improvement at final follow-up (3 for four patients, 4 for four patients, and 5 for two patients) compared to pre-surgery assessments (2 for six patients, 3 for two patients, and 4 for two patients). The mean VAS score and DASH score at final follow-up (13.0 ± 10.3, 19.3 ± 12.7, respectively) were significantly lower than those recorded before surgery (76.5 ± 11.1, 52.4 ± 17.1, respectively). The Tinel sign and the thenar muscle atrophy significantly improved from before surgery to final follow-up.

Conclusion

Carpal tunnel release with a synovial wrap demonstrated significant improvements in muscle strength, pain relief and function. The synovial wrap method is an effective procedure for treating recurrent carpal tunnel syndrome.

1. Introduction

The recurrence rate after carpal tunnel release in carpal tunnel syndrome ranges from 3 % to 19 %, with reoperation cases reaching up to 12 %.¹ The leading causes of recurrence include incomplete release of the flexor retinaculum and scarring of the median nerve.² In cases of incomplete release, a simple complete release of the carpal tunnel is effective. However, in instances of true recurrence, where symptoms initially improved but later re-occurred, a simple re-release of the carpal tunnel is ineffective due to potential scarring of the nerve itself.³

In revision surgery for carpal tunnel syndrome, studies indicate that decompression followed by additional vascularized flap coverage yields a higher success rate than simple decompression.3, 4, 5, 6 The principles guiding surgical revisions for recurrent carpal tunnel syndrome involve flexor retinaculum re-release, scar tissue removal, and median nerve coverage with a vascularized flap. This comprehensive approach prevents perineural scarring, fosters neovascularization, and facilitates nerve gliding.⁵ Nonetheless, consensus is lacking on the choice of vascularized flap for median nerve coverage in revision surgery for carpal tunnel syndrome.³

This study aims to report the treatment outcomes of synovial wrap in revision surgery for carpal tunnel syndrome. We hypothesized that this procedure will improve patients’ symptoms and functionality.

2. Patients and Methods

This was a retrospective observational study. Between January 2016 and December 2020, we treated 10 patients who underwent carpal tunnel re-release with median nerve synovial wrap for recurrent carpal tunnel syndrome. We designed a retrospective study with data obtained with a follow-up of one year or more. This study was approved by the Ethics Committee of Kyoto University Hospital. All patients signed written informed consent. We reviewed all medical records retrospectively to obtain surgical results.

The patients who had undergone previous surgery for carpal tunnel syndrome by other doctors at other hospitals, improved symptom for certain time period, and recurrences of its symptom were included. Indications for surgery were symptoms (numbness and pain in the median nerve territory and nocturnal numbness) despite a minimum of 3 months of nonsurgical treatment including wrist splint and carpal tunnel steroid injection. Before surgery, all patients were evaluated with nerve conduction study. In the revision surgery, if the median nerve adhesion to surrounding tissues was found after carpal tunnel re-release, the synovial wrap was performed. Patients who underwent surgery to address carpal tunnel re-release combined with median nerve synovial wrap were followed up at least one year after surgery. Contraindications included rheumatoid arthritis, pathological tenosynovitis (such as infections or synovial tumors), and kidney dialysis treatment due to synovial membrane disorder.

3. Surgical technique

General anesthesia is used with tourniquet control. The patient lies in a supine position and the hand is placed on the operating table. A zig-zag incision of about 10 cm is made on the palmar side of the wrist and hand. Subcutaneous tissues are divided along the skin incision, and forearm fascia and flexor retinaculum are incised to open the carpal tunnel ulnar to the nerve. If the median nerve is adhered to the surrounding tissues, scar tissue removal without epineurectomy or internal neurolysis, and synovial wrap are performed. Synovial flap dissection is begun radially and 6 cm proximally to the wrist crease because the synovial sheath is supplied by direct branches of the ulnar arteries. A 3.5 × 4-cm section of flexor synovial membrane with distal ulnar pedicle is harvested. The adherent site of median nerve is wrapped with the outer surface inward (Fig. 1). The tourniquet was deflated and the wound was closed. A volar splint is applied. Ten days after the operation, sutures and splint are removed and range-of-motion and median nerve gliding exercise is started.

Fig. 1.

Surgical technique or synovial wrap in revision surgery for carpal tunnel syndrome

a) Skin incision

b) After carpal tunnel release, dissection of the median nerve and removal of scar tissue are performed. The arrow is flap pedicle

c) Synovial flap is harvested with ulnar-side pedicle. The arrow is flap pedicle. The flap was turned over. The asterisk is radial side of the flap.

d) Synovial wrap for median nerve is performed.

4. Evaluation

Patients completed the pain visual analogue scale (VAS), the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire, the Semmes-Weinstein monofilament test in the median nerve area (SW test), and the manual muscle test of the abductor pollicis brevis muscle (MMT) as assessed on the 5-point British Medical Research Council Scale (5/5, normal; 0/5, absent). The Tinel sign in the carpal tunnel was checked, and thenar muscle atrophy by a visual inspection before surgery and at final follow-up (more than one year post-surgery) were also measured. The examinations were retrospectively assessed before surgery and at final follow-up by one of the authors (who did not perform the surgery in these patients). The VAS for the affected wrist was marked on a 10-cm line with 21 markers at 5-mm intervals. The 0-mm point indicated that the patient felt no pain, and the 100-mm point indicated maximum unendurable pain. Complications from the revision surgery were also retrospectively collected from patient medical records.

Student's t tests were used to compare the assessment results before surgery with those at final examination for VAS and DASH. Mann-Whitney U test was used to analyze the results of the MMT, and Fisher's exact test was used for Tinel sign and thenar muscle atrophy. Statistical significance was set at p < 0.05.

5. Results

We treated 23 patients who underwent carpal tunnel re-release for recurrent carpal tunnel syndrome. Among these patients, 10 patients had adhered median nerve and we performed median nerve synovial wrap. 13 patients were excluded. No patient withdrew from the follow-up study. Mean follow-up period was 44.8 months (13–74 months). The demographic data are shown in Table 1. The physical findings and nerve conduction velocity data are shown in Table 2.

Table 1.

Demographic data of patients.

Demographic Variables	Total Cases, n (%)
Patients, n	10 (100)
Sex of patients
Male	1 (10)
Female	9 (90)
Operated side
Left	3 (30)
Right	7 (70)
Age at operation, y
Mean	73.7
Range	67–84
Recurrent carpal tunnel syndrome
Yes	10 (100)
No	0 (0)
Months from primary to revision surgery
Mean	11.9
Range	7–24
Follow-up, m
Mean	44.8
Range	13–74

Table 2.

Patients’ data before surgery and at final follow up.

Pre; before surgery.

Post; at final follow-up.

DL; Distal latency in nerve conduction study (mS). N; not detected

VAS; pain visual analogue scale.

Tinel; Tinel sign in the carpal tunnel.

qDASH; Quick DASH.

Atrophy; Thenar muscle atrophy.

SW; the Semmes-Weinstein monofilament test.

MMT; the manual muscle test of the abductor pollicis brevis muscle.

Patient No	Age (y)	Sex	Pre DL	Pre VAS	Post VAS	Pre Tinel	Post Tinel	Pre qDASH	Post qDASH	Pre Atrophy	Post Atrophy	Pre SW	Post SW	Pre MMT	Post MMT
1	67	F	8.2	80	30	+	–	65	20	+	–	5.18 red	3.84purple	2	3
2	69	F	N	80	10	+	–	23	6.5	+	–	4.56 red	2.83 green	2	4
3	70	F	6.1	70	0	+	–	45.5	31	–	–	4.31 purple	2.83 green	4	5
4	71	M	8.55	60	0	+	–	39	9	+	–	4.31 purple	3.22 blue	2	4
5	72	F	5.3	70	20	+	–	56	15	+	–	3.84 purple	2.83 green	2	3
6	84	F	4	85	25	+	–	56	25	+	–	3.61 blue	3.22 blue	2	3
7	81	F	5.1	100	20	–	–	63	9	–	–	3.84 purple	3.61 blue	4	4
8	72	F	6.8	80	10	+	–	69	9	+	–	4.31 purple	3.61 blue	3	5
9	81	F	5	70	5	+	–	75	47	+	+	4.17 purple	3.61 blue	2	3
10	70	F	4.3	70	10	+	–	31	22	+	–	3.84 purple	3.22 blue	3	4

The mean VAS score was 76.5 ± 11.1 before surgery and 13.0 ± 10.3 at final follow-up (Table 2). The mean VAS score at final follow-up was significantly lower than that before surgery (p < 0.0001). The mean DASH scores were 52.4 ± 17.1 before surgery and 19.3 ± 12.7 at final follow-up (Table 2). The mean DASH score at final follow-up was significantly lower than that before surgery (p = 0.0002). The SW test before surgery was red for two patients, purple for six patients and blue for two patients (Table 2). The SW test at final follow-up was purple for one patient, blue for six patients and green for three patients. The MMT before surgery was 2 for six patients, 3 for two patients and 4 for two patients (Table 2). The MMT at final follow-up was 3 for four patients, 4 for four patients and 5 for two patients. The MMT significantly improved from before surgery to final follow-up (p = 0.0107). Nine patients had the Tinel sign in the carpal tunnel before surgery (Table 2). No patient had the Tinel sign in the carpal tunnel at final follow-up. The Tinel sign significantly improved from before surgery to final follow-up (p = 0.0001). Eight patients had thenar muscle atrophy before surgery (Table 2). Thenar muscle atrophy in seven patients improved at final follow-up (Fig. 2). Thenar muscle atrophy significantly improved from before surgery to final follow-up (p = 0.0019). No patient had complications from the revision surgery or required additional surgery.

Fig. 2.

Thenar muscle atrophy before surgery and at final follow-up

a) Thenar muscle atrophy was observed before surgery. Arrow indicates thenar muscle atrophy

b) Improvement was observed at final follow-up. Arrow indicates thenar muscle recovery.

6. Discussion

In the current study, the VAS score, DASH scores, SW test, MMT, Tinel sign and thenar muscle atrophy significantly improved after carpal tunnel re-release with synovial wrap. Some reports have described the results of the synovial flap technique in revision carpal tunnel surgery.^7,8 Wulle reported the results of 27 patients who underwent revision carpal tunnel surgery with the synovial flap technique.⁷ The patients showed excellent (6), good (16), satisfactory (3), and poor (2) results.⁷ Except for one patient, all had increased sensibility and strength, less pain, and no recurrence of night pain.⁷ Stutz et al. compared the synovial flap and hypothenar fat flap technique for treating patients with previous failed carpal tunnel decompression.⁸ In the synovial flap group, they reported reduced brachial nocturnal pain (25 %), pillar pain (25 %), a positive Tinel's sign (25 %), a positive Phalen's test (13 %), thenar atrophy (44 %), and paresthesia (62 %).⁸ The overall patient satisfaction was 56 %, and the DASH score was 37 points in the synovial flap group.⁸ The patients' improvement in the current study regarding pain relief, muscle strength, sensory disturbance and DASH scores is consistent with these studies.^7,8

In revision surgery for recurrent carpal tunnel syndrome, in addition to dissection of the median nerve and removal of scar tissue, it is necessary to wrap the median nerve with a well-vascularized flap to prevent the median nerve from re-adhesion to the surrounding tissues.⁶ In recurrent carpal tunnel syndrome, carpal tunnel re-release alone is reported to show clinically important improvements.⁶ However, there are some cases in which carpal tunnel re-release alone does not improve the symptoms.^9,10 After dissecting the median nerve and removing the surrounding scar tissue, wrapping the dissected median nerve with a well-vascularized synovial flap eliminated the nerve irritation, leading to a negative Tinel sign and decreased VAS score. The blood flow improvement in the scarred median nerve produced by wrapping it with a well-vascularized flap allowed improved nerve recovery, which was reflected in better SW test, MMT and thenar muscle atrophy indices. Finally, all of these factors caused the improvement of the DASH score, which is a patient-reported outcome regarding activities of daily living. In addition, synovial wrap prevented the nerve from recurrent scarring. All this indicates that the synovial wrap for recurrent carpal tunnel syndrome is an effective treatment option. We applied volar splint for ten days after the surgery. The postoperative splints have some theoretical advantages including prevention of flexor tendon bowstringing, prevention of nerve subluxation and prolapse into the healing wound, reduction of immediate postoperative pain, and lower rates of wound-healing complications and symptom recurrence.¹¹

For wrapping the median nerve in recurrent carpal tunnel syndrome, other methods have been reported, including pronator quadratus muscle flaps, palmaris brevis muscle flaps, flexor digitorum superficialis muscle flaps, hypothenar fat flaps, reverse radial artery perforator fascial flaps, reverse ulnar artery perforator fascial flaps, vein-graft wrapping, autologous fat transfer and nerve wrap protector.^6,12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 All of these procedures have disadvantages, including inadequate flap size and limitation of mobility because of the course of the pedicle. The synovial flap is easy to harvest and additional skin incision is not required, leading to shorter operation time. The synovial flap is thin and adequate to wrap the median nerve without bulkiness, which can cause re-entrapment of the median nerve. Pelissier et al. reported that, at the level of the wrist and carpal tunnel, the synovial sheath is supplied by direct branches of the ulnar arteries and the mean flap length and width were 4.8 cm and 3.5 cm, respectively.²³ So, in harvesting the synovial flap, it is essential to keep intact the blood flow on the ulnar side.

This study has several limitations. First, this study was a retrospective observational study without a control group. To describe the advantages of this procedure, carpal tunnel re-release and synovial wrap should be compared with carpal tunnel rerelease alone, or a randomized control trial with a control procedure should be performed. However, in recurrent carpal tunnel syndrome, the scarred median nerve condition differs for each patient. Patients treated with the control procedure would require an additional surgery after completing the observation period. We used general anesthesia to dissect the scarred median nerves. It can be performed under local subcutaneous infiltration combined with ulnar and median nerve blocks. Second, the current procedure consists of carpal tunnel re-release and synovial wrap. It is difficult to evaluate effectiveness of the synovial wrap by itself because the procedure includes median nerve decompression by carpal tunnel re-release. We set the surgical indication for synovial wrap as median nerve adhesion to surrounding tissues after carpal tunnel re-release. In cases without median nerve adhesion, we only perform carpal tunnel re-release. So, it is clear that synovial wrap for median nerve adhesion has some advantages. Third, the number of patients was low. As described above we performed synovial wrap to treat median nerve adhesion to surrounding tissues. We selected carpal tunnel re-release alone for median nerve compression without adhesion. So, the number of patients tended to be low. However, all of the patients improved some of their symptom and the synovial wrap method has some effectiveness. Finally, we have insufficient nerve conduction study data before primary operation which was performed by previous hospitals. It is helpful to decide initial carpal tunnel release was effective or not. However, we performed nerve conduction studies before the revision surgeries to make a differential diagnosis for compression of the median nerve in flexor digitorum superficialis arch, pronator tunnel syndrome, cervical radiculopathy, and other known factors.

In conclusion, A significant improvement in sensory disturbance, muscle strength, pain relief and the patient-reported outcomes were obtained after carpal tunnel re-release with synovial wrap. Synovial flap is harvested easily in the same operation fields in comparison with other flaps. It is clear that the synovial wrap method is an effective procedure for treating recurrent carpal tunnel syndrome with median nerve adehesions.

Funding

None.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.