Initial Outcomes of a Novel High-Visibility Endoscopic Carpal Tunnel Release Technique

Abstract

Background  A large variety of endoscopic carpal tunnel release methods have been described in efforts to shorten recovery time, reduce scar discomfort, and allow earlier return to work. The majority of existing techniques are the modifications of the Agee, Chow, and Menon techniques, all of which require dedicated equipment that can increase facility and surgical fees for the patient and institution. We present a novel high-visibility endoscopic carpal tunnel release technique that uses common hand surgery instruments available in all surgical units, without requiring disposable or custom devices.

Description of Technique  The cases were performed under local anesthesia using routine reusable instruments and a conventional 2.5-mm 30-degree small joint arthroscope. Following proximal dissection, a clear, colorless, plastic shield was created from a standard syringe that offered a 360-degree vision of the carpal tunnel and protection of the median nerve. Release of the transverse carpal ligament was performed under full arthroscopic vision using Metzenbaum dissection scissors.

Methods  This pilot study analyses the first nine cases in eight patients who were operated on using this technique, with a minimum of 6 months of follow-up.

Results  No peri- or postoperative complications were encountered. All patients demonstrated significant improvements in the Disabilities of the Arm, Shoulder, and Hand score, the Boston Carpal Tunnel Questionnaire score, and a visual analog score for pain.

Conclusion  The high-visibility endoscopic carpal tunnel release technique is safe and effective, and offers a viable cost-reducing alternative to the existing endoscopic methods for carpal tunnel syndrome. Future comparative trials are required to validate these findings in a larger series.

Level of Evidence  This is a Level IV study.

Carpal tunnel syndrome (CTS) is the most common compression neuropathy. ¹ Open carpal tunnel release (OCTR) has historically been the gold standard of treatment, but it is not without complications. ² These include persistent weakness, tenderness of the scar, and pillar pain in the thenar or hypothenar area. ^{3 4} Even when completely successful, the length of perioperative disability and the extended recovery interval after OCTR may be expensive for both patients and employers. ⁵

In efforts to reduce scar discomfort after surgery for CTS, several endoscopic techniques have been introduced. These can be broadly divided into three main groups: the Agee single-portal technique, ^{6 7} the Chow dual-portal technique, ^{8 9} and the Menon technique. ^{10 11} All of these aims to section the transverse carpal ligament (TCL) while preserving the integrity of the volar structures. They have been demonstrated to significantly shorten recovery time and allow earlier return to work when compared with OCTR, but they have not been proven to reduce the incidence of major complications, reoperations, and recurrence of symptoms. ^{1 12} The vast majority of the published techniques require the use of dedicated instrumentation that can only be used for endoscopic carpal tunnel release (ECTR), such as the Agee carpal tunnel release system, the disposable Concept carpal tunnel relief kit from Linvatec, and the Chow ECTRA disposable kit. These systems are costly, reflected in increased facility and renumeration fees, ¹³ and may be unviable for all hospitals, particularly for those in a publicly funded health care model.

We present a novel cost-saving “high-visibility” single-portal technique that utilises common hand surgery instruments available in all surgical units, without requiring disposable or custom ECTR devices.

Indications and Surgical Technique

Video 1 Arthroscopic video of the release of the transverse carpal ligament under vision.

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Video 2 Arthroscopic video demonstrating the end of the endoscopic release.

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Patients with CTS usually present with characteristic history and symptoms such as nocturnal pain and paresthesia, numbness to the distribution of the median nerve in the fingers, and weakness of the thenar muscles in advanced cases. We reserve the high-visibility ECTR for patients with positive CTS symptoms that have failed conservative therapy in the form of splinting and a local corticosteroid injection in the carpal tunnel for at least 3 months. Contraindications for this technique include space-occupying lesions, limited wrist extension, congenital wrist anomalies, and a history of previous wrist or carpal surgery.

Required instrumentation includes 2.5-mm 30-degree conventional small joint arthroscope, Metzenbaum dissection scissors, a Freer elevator, Catspaw retractors, and a standard 10-mL syringe. Patients are positioned supine with the arm resting on a hand table. The wrist is extended by placing a small rolled towel under the distal forearm. Local anesthesia infiltration is performed with 20 mL of 0.5% bupivacaine.

We routinely mark out the planned incision on the patient's volar skin. A longitudinal line is drawn along the ulnar border of the middle finger, and Kaplan's line is drawn along the abducted thumb. ¹⁴ The intersection between these two lines indicates the location of the distal end of the TCL. The radial border of the palmaris longus (PL) tendon is palpated, and a transverse planned incision line is drawn at the distal wrist crease from the radial border of the PL ulnarly for 1 cm ( Fig. 1 ). For patients with absent PL, the incision is centered on the line drawn from the ulnar border of the middle finger.

Fig. 1.

The planned incision is marked on the patient wrist.

Once the surface bearings have been drawn, the transverse incision is made in the skin and the subcutaneous tissue is bluntly dissected off the volar forearm fascia. The PL tendon is dissected and retracted radially to protect the palmar cutaneous branch of the median nerve. A Freer elevator is used to free the palmar aponeurosis from the TCL, creating a space that can accommodate a retractor. A transverse incision is made in the antebrachial fascia to expose the median nerve, and the Freer elevator is inserted between the median nerve and the TCL to free any adhesions that may be present ( Fig. 2 ). A colorless, clear, see-through, 5 cm × 1 cm gently curved plastic shield is created by cutting out a piece of the 10-mL syringe, ensuring that the distal edge is smooth and free of sharp corners ( Fig. 3 ). This is carefully placed between the TCL and median nerve in the carpal tunnel ( Fig. 4 ). In contrast to the previously published methods, the clear shield used in this technique is significantly thinner than the existing ECTR devices ^{6 9} and cannulas, ^{10 11 15} which consequently applies less pressure to the already stenotic median nerve. It also offers a 360-degree view of the carpal tunnel throughout the procedure, improving surgical control and safety.

Fig. 2.

A Freer elevator is used to free adhesions between the median nerve and transverse carpal ligament.

Fig. 3.

( A, B ) A clear plastic shield is created from a 10 mL syringe.

Fig. 4.

The clear shield is introduced between the median nerve and transverse carpal ligament.

With the clear shield in position protecting the median nerve, the proximal part of the TCL is cut under direct vision. The arthroscope is then maneuvered proximal to the TCL aiming distally and volarly. A Catspaw retractor is used to elevate the palmar aponeurosis above the TCL, creating a small window of space that can accommodate the superior blade of the Metzenbaum scissors. The inferior blade rests in the space formed from the gentle curve of the plastic shield under the TCL ( Fig. 5 ). With the scissors and arthroscope coordinated to ensure an unhindered view, the surgeon begins to cut the TCL in an antegrade direction under arthroscopic vision( Fig. 6 , Video 1 ). As the scissor advances along the TCL, the arthroscope is also advanced closely behind in the pocket of space formed above the released TCL to maintain optimal vision. The release is complete when the distal end of the TCL and the fat proximal to the superficial palmar arch are seen on the scope ( Fig. 7 , Video 2 ). Complete release is confirmed at the end of the procedure by passing the Freer elevator along the carpal tunnel to ensure that no stenotic areas remain.

Fig. 5.

The Metzenbaum scissors is introduced between the arthroscope and retractor.

Fig. 6.

The transverse carpal ligament is cut in an anterograde direction. L, released transverse carpal ligament; P, clear shield; S, scissors.

Fig. 7.

The distal end of the endoscopic release. L, released transverse carpal ligament; P, clear shield; S, scissors.

Postoperatively, the wound is closed with a 5–0 nonabsorbable nylon suture that is removed at 2 weeks. Active hand therapy is initiated at 2 days following surgery to improve hand strength and prevent stiffness.

Patients and Methods

This pilot study was performed at a national tertiary referral center for hand surgery and was approved by the Institutional Review Board. The clinical records of all patients who underwent the high-visibility ECTR technique by a single surgeon with a minimum follow-up of 6 months were analyzed.

Patient-reported outcomes were obtained preoperatively and at the 6-month follow-up by a dedicated hand therapist. Outcome assessments taken included the Disabilities of the Arm, Shoulder, and Hand (DASH) score, the Boston Carpal Tunnel Questionnaire, and a visual analog score (VAS) for pain (range: 0, no pain, to 10, maximum pain). We also asked patients if they were satisfied with the procedure outcome and if they would undergo this procedure again at the final follow-up.

The data were assessed for normality using the Shapiro–Wilk test. Nonparametric data were evaluated with the Wilcoxon signed-rank test. Significance was defined at 0.05.

Results

We performed this technique in nine hands (eight patients). The mean age of patients was 60 years (range: 39–82 years). All patients were females. The mean duration of symptoms prior to surgery was 51 months (range: 6–240 months).

We did not encounter any perioperative or postoperative complications. No patients developed pillar pain or excessive scar hypersensitivity in this series. There were no neurovascular injuries or symptoms of transient neurapraxia. No patients required reoperation or developed recurrent symptoms.

All patients demonstrated significant improvements in patient-reported outcome scores at the 6-month follow-up compared with before surgery, particularly in the DASH score and VAS ( Table 1 ). All patients were satisfied with the procedure and stated they would undergo this surgery again should they experience the same symptoms in the opposite hand.

Table 1. Median patient-reported outcomes.

	Preoperative	Six months postoperative	p -Value
DASH score	30	5	<0.05 a
BCTQ symptom severity scale	2.5	1.2	<0.05 a
BCTQ functional severity scale	1.8	1.3	<0.05 a
VAS score	4.8	0.5	<0.05 a

Abbreviations: BCTQ, Boston Carpal Tunnel Questionnaire; DASH, Disabilities of the Arm, Shoulder, and Hand; VAS, visual analog score.

^aStatistically significant.

Discussion

Although ETCR allows earlier return to work and may be more cost-effective on a societal basis, ¹⁶ the economics have not been replicated on a per-case basis. ^{5 13} Part of this could be because of the requirements of dedicated instrumentation purely for the use of ECTR, which would undoubtedly incur additional purchase, maintenance, and training costs. Our novel cost-saving ECTR technique employs standard reusable instruments found routinely in hand surgery units and can be performed by all operating room teams familiar with small joint arthroscopy without the need for additional training.

Unlike the existing published methods, our technique does not require the use of dilators, bulky cannulas, or specialist endoscopes to enlarge the space under the palmar aponeurosis or within the already stenotic carpal tunnel. ^{6 7 8 9 10 11 15} These devices can further compress the median nerve intraoperatively and may potentially cause iatrogenic injury. The clear shield fashioned from a 10-mL syringe is thin, simple to create, and affords high-visibility of both the nerve and TCL, allowing easy identification of possible anatomic variations. This is different from the majority of the existing specialist ECTR kits on the market, which are constructed from metal ^{6 7 8 9 17} or opaque plastics. ¹¹ These kits have a significantly restricted vision of the carpal tunnel and are thus more difficult to operate compared with our see-through implementation. The current technique also uses conventional Metzenbaum scissors to cut the TCL, offering better tactile feedback to the surgeon than hook knives ^{8 9} or beaver blades, ^{6 7} thereby improving surgical control and potentially reducing perioperative complications.

The clinical results in demonstrated in this study are comparable, if not superior, to the existing published randomized controlled trial outcomes and meta-analysis results for ECTR. ^{1 18 19 20} We acknowledge the main limitations of this study, are the small number of participants and its retrospective nature. We are also aware that there is no cohort for comparison with, such as a traditional ECTR method or OCTR. However, this study does introduce a novel technique for ECTR that would be particularly suitable for use in publicly funded health care organizations or financially constrained institutions.

Conclusion

The high-visibility ECTR technique is safe and effective, and offers a viable alternative to the existing methods for the surgical treatment of CTS. It provides enhanced surgical vision, a lower learning curve, and reduced risk of iatrogenic nerve injury than the existing published methods. It also only requires routine, nondisposable instruments and is suitable for use in hospitals of all budgets. Although the initial results are promising, the case numbers in this pilot study are limited, and further larger comparative trials are required to validate these findings.

Funding Statement

Funding The study was funded by the Beijing Municipal Administration of Hospitals Incubating Program (PX2018018) and Beijing Ji Shui Tan Hospital High-level Talents “Key Researcher” Program (XKGG201801).