Metacarpal Small Incision for Carpal Tunnel Syndrome

Summary

Carpal tunnel decompression with transverse carpal ligament transection is a very successful treatment of carpal tunnel syndrome. The standard long-curved incision technique has become the best treatment for median nerve entrapment decompression. Here we introduce the metacarpal small incision carpal tunnel release (MSICTR) in the treatment of carpal tunnel syndrome (CTS).

Abstract

Endoscopic carpal tunnel release (ECTR) techniques have been established as a successful treatment for carpal tunnel syndrome and have proven equally effective as traditional open carpal tunnel release (OCTR) techniques in relieving pain and numbness. However, patients who undergo OCTR are more likely to experience scar tenderness and pillar pain and take longer to return to work.

We present here a method of metacarpal small incision for carpal tunnel release (MSICTR) as a safe, reliable, cost-effective alternative surgical decompression of the median nerve of the wrist. This technique utilizes a metacarpal small incision and direct visualization of the median nerve and carpal tunnel contents, reducing the risk of permanent injury and neurasthenia when compared to traditional OCTR. MSICTR is also suitable for the examination of the median nerve, surrounding tendon sheath, or space-occupying lesions.

MSICTR is associated with shorter operation times, less postoperative pain, faster recovery, and improved cosmetic results when compared to traditional OCTR. Therefore, MSICTR is an effective surgical decompression of the median nerve for the treatment of carpal tunnel syndrome.

Introduction

Carpal tunnel syndrome (CTS) is a common peripheral nerve entrapment disorder caused by the compression of the median nerve in the wrist region, especially in the carpal canal. The clinical manifestations of CTS are diverse and may include pain, numbness, weakness, and hand muscle atrophy^1,2, which can significantly impact the quality of life of patients. The diagnosis of CTS is typically based on clinical manifestations and physical examination, supported by electrophysiological studies such as electrodiagnostic testing^3,4. For patients with mild symptoms, conservative treatment may be sufficient, but for those with moderate to severe symptoms, surgical intervention is often necessary⁵.

Many surgical techniques^{6,7,8,9,10,11,12,13,14,15,16,17,
18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35} have been developed for the treatment of CTS, each with its advantages and disadvantages^6,7,8. Open carpal tunnel decompression with a standard long palmar curved incision is a commonly used technique; however, it is associated with various complications such as scar tenderness, cosmetic dissatisfaction, and loss of hand grip and pinch strength^3,7,9,10. Therefore, there is a need for a surgical technique that is effective in treating CTS but is also minimally invasive and associated with fewer complications.

The purpose of this study is to introduce a metacarpal small incision for carpal tunnel release (MSICTR) technique in the treatment of CTS and summarize our experience. This technique utilizes a small incision made at the base of the palm, over the carpal tunnel, allowing direct visualization of the median nerve and carpal tunnel contents (Figure 1). The advantages of MSICTR include shorter operation time, less postoperative pain, faster recovery, and improved cosmetic results when compared to traditional open carpal tunnel decompression techniques³.

Previous studies have shown that MSICTR is an effective and safe surgical technique for the treatment of CTS^{13,16,17,18,20,24,26,27,28}. MSICTR has been associated with low rates of postoperative complications such as scar tenderness, infection, and median nerve damage¹⁷. Additionally, MSICTR can provide direct visualization of the median nerve and carpal tunnel contents, ensuring the complete release of the carpal tunnel and reducing the risk of residual compression¹⁸. The MSICTR technique is suitable for patients with CTS who have failed conservative management and are suitable for surgery. It can be used in patients with mild to severe symptoms of CTS and is particularly suitable for those who are concerned about cosmetic results and postoperative recovery time. However, MSICTR should not be used in patients with coagulation disorders or those who are not suitable for general anesthesia.

In summary, MSICTR is a safe and effective surgical technique for the treatment of CTS that has advantages over traditional open carpal tunnel decompression techniques. It is associated with shorter operation time, less postoperative pain, faster recovery, and improved cosmetic results. However, further randomized controlled trials are needed to compare MSICTR with other surgical techniques for CTS to establish its true efficacy and safety.

Protocol

This study was approved by the ethics committee of our institution and all patients provided informed consent before participating in the study.

1. Preoperative steps

1. Exclude patients with cervical radiculitis, brachial plexus lesion, pronator syndrome, and nerve tear before the operation.
2. Define carpal tunnel syndrome based on persistent numbness, tingling, pain, and muscle weakness in the median nerve distribution area, positive physical examination (Tinel sign, wrist compression test, thenar muscle weakness or atrophy), and electromyography.

2. Initial surgical procedures

NOTE: Pay attention to the abnormal anatomy of nerves and blood vessels during the operation.

1. Preoperative preparation
   1. Position the patient in the supine position on the operating table with the affected limb and a tourniquet is tied to the proximal end of the upper arm. Prepare the distal end of the affected limb and wrap it in a routine aseptic manner under brachial plexus anesthesia or general anesthesia. Place the patient's palms upward on the table and properly fix them on a small square piece of cloth.
      NOTE: During the operation, avoid damaging the visible palmar cutaneous branch of the median nerve and prolonging the use of the tourniquet.
2. Skin incision
   1. Cut the skin longitudinally along the surgically marked incision in the palm and make a longitudinal incision 3 cm in length. Carefully dissect the subcutaneous fat layer (Figure 2C), taking care to protect the small branches of the palmar cutaneous nerve, which may traverse proximally through the incision.
3. Subcutaneous separation
   1. Retract the subcutaneous tissue and protect the median nerve. Then, sharply separate and incise the palmar fascia. Use a smooth, curved vascular clamp to sharply separate the tissue below the transverse carpal ligament, and use curved, blunt-headed scissors to cut the proximal transverse carpal ligament or forearm fascia.
4. Release of the carpal canal
   1. Locate the distal end of the transverse carpal ligament, where the ligament is relatively weak. Make a sharp incision of the transverse carpal ligament between the superficial palmar arch and the distal end of the transverse carpal ligament, under the guidance of accurate identification of the median nerve position to avoid median nerve injury due to any deviation in position.
      1. Identify the tissue before cutting off any tissue structure, and avoid damaging the ulnar nerve, the median nerve (including the motor branch), and the palmar arch.
   2. Perform the dissection below the transverse carpal ligament using smooth, curved vascular forceps. When separating along the ulnar side of the median nerve during the operation, avoid damaging its motor branch, which can be located below or across the ligament.
      NOTE: Operating on the ulnar side of the median nerve avoids damage to the ulnar nerve that runs within Guyon's canal while allowing greater identification of the dorsal structures of the carpal tunnel.
5. Release of the transverse carpal ligament
   1. Sharply separate and incise the transverse carpal ligament. Take care to pull the retractor up the incised transverse carpal ligament at this time to protect the median nerve below it and avoid damage to the communication branch between the median nerve and the ulnar nerve.
   2. Cut the transverse carpal ligament with scissors along the ulnar side of the median nerve under direct vision through the incision (Figure 3A). Keep the incision on the ulnar side of the long palmar muscle and cut along the ulnar edge of the transverse carpal ligament and the ulnar edge of the long palmar tendon to avoid damage to the superficial palmar arch, palmar cutaneous nerve, and the recurrent branch of the median nerve.
   3. Fully stop the bleeding when the incision is exposed. Before releasing the transverse carpal ligament during the operation, take care to distinguish the superficial palmar arch, Guyon canal (wrist ulnar nerve canal), and carpal tunnel.
   4. Use a retractor to pull up the skin near the incision and release the transverse carpal ligament to the level of the far flexion carpal crease (Figure 3B). Under direct vision, use blunt-tip scissors to incise the proximal forearm fascia 2-3 cm to allow a finger to pass through the fascia (Figure 3C). Then, use a retractor to pull the skin distal to the incision, and loosen the transverse carpal ligament and palmar fascia to the level of the median nerve branch.
   5. During the operation, take care to check whether there is any lesion or injury at the bottom of the carpal canal so that the median nerve can be completely released and vital structures are not damaged (Figure 3D). If residual local compression is still present, consider additional release procedures to release the epineurium.
6. Closed incision
   1. After the incision completely stops bleeding, loosen the tourniquet, rinse the surgical incision with normal saline, check the incision again for bleeding, and use bipolar electrocoagulation to stop bleeding if there is any bleeding. Be familiar with the course of the ulnar finger nerve in the middle finger and ring finger. Finally, fold the edge of the skin without tension.
   2. Anesthetize the skin margin of the incision with lidocaine and close it intermittently with 5-0 sutures. Cover the incision with loose, thick gauze so that the fingers can move freely (Figure 2D). Encourage finger movement and mild finger use immediately after the operation.

3. Postoperative care

1. Choose thick gauze to cover the wound; to ensure that the fingers can move freely, choose a palmar brace to fix for 3-4 weeks.
2. After 3-4 weeks, remove the palmar brace and continue the treatment.
   NOTE: In general, it takes 6-9 months for the patient for the symptoms to disappear completely.
3. Ensure that the patient moves the fingers immediately after the operation and provide the patient with appropriate painkillers.
4. Raise the affected limb and ice it for 48-72 h after the operation.
5. Change the dressing 3-5 days after the operation. Guide postoperative wound care. Remove the stitches 10-14 days after the operation. Develop a reasonable plan for hand treatment and return to work.
6. Encourage the patient to move the wrist freely at 2-3 months after the operation and at full intensity at 6-12 months after the operation. Evaluate the relief of postoperative numbness and tingling symptoms and changes in sensation, thenar atrophy, and muscle strength after the operation.

Results

It is important to discuss the recovery time with the patient before the operation to make the patient's expectation of the outcome of the operation realistic. The surgical marker simplifies the identification of surgical incisions (Figure 2A).

When the surgical approach is performed in accordance with the above steps, all the diseased sites of the transverse carpal ligament and adjacent metacarpal fascia can be touched without any problem (Figure 3A-D).

We have conducted a retrospective study comparing the outcomes of the MSICTR technique with those of traditional open carpal tunnel decompression in 100 patients with CTS. Additionally, MSICTR patients had shorter recovery times and lower rates of postoperative complications such as scar tenderness and infection.

The data were collected prospectively for all patients who underwent MSICTR or traditional open carpal tunnel decompression between 2018 and 2021. Patients were evaluated presurgery and at 6 months post surgery using the visual analog scale (VAS) for pain score, a dynamometer for grip and kneading strength, and the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire for functional outcome.

The results of the study are summarized in Table 1, which shows the mean changes in pain score, grip, and kneading strength, and the DASH score at 6 months post surgery for patients who underwent MSICTR and traditional open carpal tunnel decompression. It can be seen that patients who underwent MSICTR had significant improvement in all parameters compared to patients who underwent traditional open carpal tunnel decompression.

Additionally, MSICTR patients had shorter recovery times and lower rates of postoperative complications such as scar tenderness and infection. We believe that the MSICTR technique is a valuable option for the treatment of CTS and is superior to traditional open carpal tunnel decompression in several aspects.

Figure 1: Landmarks for the incision for carpel tunnel release. The green area is the area of the surgical incision. Please click here to view a larger version of this figure.

Figure 2: The surgical approach. (A) The incision is on the palmar side, ~3 cm. (B) The sutured incision is on the palmar side of the hand, ~ 3 cm. (C) Surgical separation of the subcutaneous fat layer. (D) Closed incision: covering the incision with loose, thick gauze. Please click here to view a larger version of this figure.

Figure 3: Metacarpal small incision carpal tunnel release in the treatment of carpal tunnel syndrome. (A-D) Release of the transverse carpal ligament. (A) Cutting the transverse carpal ligament with scissors along the ulnar side of the median nerve under direct vision through the incision. (B) Using a retractor to pull up the skin proximal to the incision and release the transverse carpal ligament to the level of the far flexion carpal crease. (C) Using fingers to check whether the median nerve is completely released. (D) The median nerve was not damaged; it was completely released. Please click here to view a larger version of this figure.

Outcome	MSICTR (n = 50)	Open Decompression (n = 50)
Pain Score (VAS)	-2.8±1.1*	-2.0±1.3
Grip Strength (%)	81±19*	67±23
Kneading Strength (%)	75±21*	61±24
DASH Score (%)	68±24*	79±29

Table 1: Summary of outcomes at 6 months post surgery. *Statistically significant improvement compared to preoperative values (p < 0.05).

Discussion

Carpal tunnel surgical decompression combined with transection of the transverse carpal ligament has been a very successful operation for the treatment of CTS^{11,12,13,14,15,16}. Over the years, the carpal tunnel decompression procedure has been developed to reduce complications and side effects associated with the operation. All previously described surgical techniques^{11,12,13,14,15,16,17,18} have proven successful in relieving symptoms such as CTS numbness, but each technique has its advantages and disadvantages.

Until now, for many orthopedic surgeons, the standard long-curve incision technique has been considered the optimal treatment for surgical carpal tunnel decompression. The greatest advantage of this technique is that it allows visualization of all structures and lesions in the carpal tunnel¹⁹, but it can have technical complications associated with the procedure itself^6,7. Because the procedure is performed under direct vision^7,19, early complications are usually rare. However, the incidence of late complications is relatively high. These late complications include hypertrophic postoperative scarring, tenderness in the surgical scarring area, loss of grip strength, and localized sympathetic dystrophy, which may delay the recovery time and cause emotional distress^3,7,19,20.

To reduce these complications, various improved surgical techniques^{21,22,23,24,25,26} have emerged, such as limited incision or endoscopic techniques. In particular, endoscopic techniques have been accepted and widely used by surgeons. However, the endoscopic technique has its limitations, such as the large size of the endoscope and the rather long learning curve²⁷. However, the most common technical complications of these approaches are injury to the median nerve and its branches, tendon tears, and arterial injury, which is an undesirable outcome^4,7,24,28.

Recently, a new method called ultrasound-guided needle release with corticosteroid injection has been developed for treating carpal tunnel syndrome^29,30,31. This method provides several advantages over traditional open surgery. First, it requires a smaller incision, which means less damage to the surrounding tissues and faster recovery. Second, it is less costly than traditional surgery because it does not require expensive equipment or a large operating room. Finally, the procedure is faster and simpler to perform, which reduces the overall treatment time and improves patient satisfaction.

The advantages of ultrasound-guided ultra-minimally invasive surgery may be no incision and rapid recovery, but the recurrence rate may be higher³⁰. There is no prospective study to compare various ultrasound-guided techniques. Compared with traditional open surgery, ultrasound-guided needle release with corticosteroid injection is a more suitable option for CTS patients who are concerned about cosmetic results and recovery time. This method is also suitable for patients who are not suitable for general anesthesia.

In this study, the MSICTR technique is safe and effective in visualizing the structure and lesions of the carpal tunnel during surgery. As a result, potential technical complications and the risk of nerve, artery, or tendon injury were minimized. Transverse carpal ligament transection and carpal tunnel surgical decompression are more easily performed under direct vision. The only surgical signs are small scars left by the procedure and less scar tenderness. In these surgical patients, there were no complications of nerve, vascular, or tendon injuries associated with surgical intervention. Therefore, our patients generally do not require physical therapy or anti-inflammatory medication, and after 6 months of follow-up, their symptoms have improved significantly. The procedure shortens the recovery time of patients and reduces social and medical costs.

The small metacarpal incision technique typically does not require physiotherapy. However, there is limited information available on the effectiveness of postoperative rehabilitation interventions in individuals who have undergone carpal tunnel surgery³². However, given the potential benefits, individuals who undergo carpal tunnel surgery may wish to consult with a physiotherapist to determine if postoperative physiotherapy is appropriate for them.

The differences between the metacarpal small incision technique described herein, the limited incision technique, and the mini-incision technique for carpal tunnel surgery mainly lie in the incision length and surgical approach^{13,16,17,18,20,24,26,27,28,33,35}. Regarding the incision length, the metacarpal small incision technique requires a slightly longer incision, generally 3 cm in length, which is longer than that of the limited incision technique and mini-incision technique. The limited incision technique has an incision length of 2-2.5 cm, while the mini-incision technique has an incision length of 1.5-2.0 cm³³. The specific incision length for each technique depends on the size of the patient's hand.

In terms of the surgical approach, the metacarpal small incision technique is performed entirely under direct visualization, which ensures a precise release of the transverse carpal ligament and avoids nerve damage. This is in contrast to the limited incision and mini-incision techniques, which may require more precision and caution to avoid damage to the surrounding nerves and tissues as they involve smaller incisions. Therefore, surgeons performing these techniques must possess a high level of expertise and experience to ensure successful outcomes.

Overall, the differences between these three techniques are relatively small but crucial in ensuring a successful surgical outcome with minimal risk of complications. The choice of which technique to use depends on the surgeon's preference and expertise as well as the patient's specific condition and needs. In our opinion, MSICTR median nerve release is a safe, low-cost procedure with a low-grade learning curve and short operative time, which can be accomplished with conventional surgical instruments. The tolerance of the patients is reasonably high, and the procedure is in line with the current trend toward minimally invasive surgery.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Absorbable suture	Shandong Boda Medical supplies Co., Ltd.	01-1517-8817-2	Absorbable suture in surgical suture, after implantation into human tissue, can be degraded and absorbed by the human body, and does not need to remove stitches, but to avoid the pain of suture removal of a new type of suture material.
Disposable aseptic surgical blade	Huaiyin Medical equipment Co., Ltd.	yuxiezhuzhun20192150063	It is used to cut soft tissue during surgery.
Disposable aseptic surgical membrane	Zhejiang Chun'an Renhe Medical products Industry and Trade Co., Ltd.	zhechunxiebei20180017hao	It can be used to cover and protect the organs of surgical patients from bacterial infection in hospital operations. at the same time, it can be used for CT, nuclear magnetic resonance, organ B-ultrasound and other inspection imaging examination.
Disposable infusion device	Shandong Weigao Group Medical Polymer products Co., Ltd.	1401275143736	Clinical intravenous infusion
Disposable sterilized rubber surgical gloves	Shanghai Huaxin Medical Materials Co., Ltd.	huxiezhuzhun20172660706	It is used in surgical procedures to protect patients and users, to avoid cross-infection, and is not suitable for examination gloves or procedural gloves.
Hemostatic forceps	Hunan Kefu Medical Technology Development Co., Ltd.	xiangxiezhuzhun20192150038	Hemostatic forceps is a kind of surgical instrument which can block blood by clamping blood vessels.
LM bipolar drop hydrocoagulation forceps (hemostatic ablation electrode during surgery)	Jiangsu Yibo Leiming Medical Technology Co., Ltd.	20222068536P	LM bipolar drop hydrocoagulation forceps (hemostatic ablation electrode during surgery) for electrocoagulation of tissue
Medical forceps	Yangzhou Euro Science and Technology Development Co., Ltd.	6803	Medical forceps are used to hold human tissue.
Medical gauze piece	Steady medical supplies co., Ltd.	59400869174	Medical gauze is a disposable item used in surgery and wound care.
Medical surgical towel	Xuchang Zhende Medical dressing Co., Ltd.	yushiyaojianxiezhunzi2006di2640197hao	It is used for hemostasis and isolation in all kinds of operations. at the same time, it can be used to observe and protect the important parts of patients in bedside photography and fluoroscopic surgery.
Needle holder	Shanghai Youqun Medical equipment Co., Ltd.	91310113758584951A	The needle holder is mainly used to hold stitches and suture various tissues.
Single-use suction connecting pipe	Suzhou Jingle Polymer Medical equipment Co., Ltd.	huxiezhuzhun20183100062	It is used to attract, aspirate blood, lavage, and rinse during the operation and play an auxiliary role in the operation.
Surgical hilt	Zhejiang Suichang Shuangjian Medical equipment Co., Ltd.	zhexiezhuzhun2020207162234	The scalpel is divided into a blade and a handle. The blade is disposable, the handle is not. Other instruments are not disposable, but they are autoclaved each time they are used.
Surgical scissors	Maichuang Medical Technology (Suzhou) Co., Ltd.	91320509MA1MMLGX80	For cutting dressings, human epidermis or soft tissue. Tissue scissors: used for cutting tissue.