Carpal tunnel release using the KnifeLight technique: An alternative to endoscopic approach?

Abstract

Introduction and importance

Carpal tunnel syndrome (CTS) is caused by compression of the median nerve, leading to both sensory and motor dysfunction in the hand. Traditional open carpal tunnel release (CTR) is a proven treatment but often results in longer recovery times, visible scarring, and postoperative issues like pillar pain. Endoscopic techniques, while reducing recovery time and limiting incision size, present risks such as incomplete ligament release and possible nerve injury. This underscores the need for a surgical approach that combines the advantages of both methods while minimizing their downsides.

Surgical technique and Case presentation

This article introduces a minimally invasive surgical technique for CTR using the KnifeLight instrument. The procedure involves a small incision and integrates a light source for improved visualization. This setup enables precise division of the transverse carpal ligament, reducing the risk of damage to surrounding structures. Each step of the procedure is detailed, highlighting its advantages over both traditional open and endoscopic CTR.

Clinical discussion

The KnifeLight technique enables more controlled and accurate ligament release, resulting in reduced scarring and quicker recovery. Initial data indicate that patients experience less postoperative discomfort and shorter rehabilitation compared to traditional CTR. This method's precision also reduces the risk of complications, such as nerve damage or incomplete ligament release. The KnifeLight procedure represents a promising middle ground between open and endoscopic CTR. It combines the visual clarity and precision of open surgery with the benefits of a smaller incision and quicker recovery typical of endoscopic methods. The built-in light source enhances visualization, ensuring both patient safety and effective ligament release. However, further comparative studies are needed to fully assess its long-term outcomes and potential complications.

Conclusion

The KnifeLight technique for carpal tunnel release offers a strong alternative to both open and endoscopic CTR methods. It minimizes scarring, shortens recovery time, and improves overall patient outcomes, making it a potential future standard for treating CTS. Further research and broader clinical adoption are necessary to confirm its long-term efficacy and safety.

Highlights

• •Alternative to Endoscopic Technique: The KnifeLight technique offers a minimally invasive alternative to endoscopic carpal tunnel release, combining the benefits of both open and endoscopic methods.
• •Faster Recovery: Compared to traditional open surgery, this method leads to shorter recovery times with less postoperative discomfort and quicker return to daily activities.
• •Minimal Scarring: The small incision minimizes scarring, making the procedure more cosmetically appealing and reducing potential for pillar pain.
• •Promising Alternative: The KnifeLight technique bridges the gap between traditional and endoscopic CTR, offering a safer, simpler, and effective alternative for carpal tunnel release.

1. Introduction

Carpal tunnel syndrome (CTS) results from compression of the median nerve within the carpal tunnel. This condition impairs both sensory and motor functions in the hand, particularly affecting the thenar eminence and the lateral two lumbricals. The primary treatment for CTS has traditionally been open carpal tunnel release (OCTR), which involves a lengthy incision from the mid-palm to the wrist crease, providing excellent access for direct visualization and complete division of the transverse carpal ligament. However, this approach is frequently associated with significant postoperative complications, including unsightly scarring, pillar pain, and extended recovery periods [1,2].

To address these issues, endoscopic carpal tunnel release techniques (ECTR) were developed, which reduce incision size and promote faster recovery by utilizing a small, endoscope-guided approach. Despite these advantages, endoscopic methods present challenges such as a steep learning curve, risks of incomplete ligament release, and high complication rates between 10 and 25 % depending on patient factors and surgeon experience. ECTR, also, reduces incision size and recovery time but introduces specific risks due to limited visualization of the transverse carpal ligament (TCL), including nerve injury and incomplete release, with complication rates ranging from 5 to 15 %. Notably, these risks increase when surgeons attempt to continue ECTR despite poor visualization, rather than converting to OCTR, which can significantly decrease surgical morbidity. Given these limitations, there is a clear clinical need for a minimally invasive technique that maintains OCTR's precision while minimizing ECTR's visualization challenges. The KnifeLight approach addresses this by enhancing intraoperative visualization with a built-in light source, allowing for controlled ligament release through a smaller incision, and ultimately aiming to lower complication rates associated with both OCTR and ECTR [2,3].

In light of these considerations, a new minimally invasive technique using the KnifeLight instrument (Stryker, Kalamazoo, MI) has emerged. This technique aims to combine the benefits of both traditional open and endoscopic approaches while mitigating their respective drawbacks. The KnifeLight method employs a shorter, palmar incision and provides direct visualization of the carpal tunnel, which enhances precision and potentially reduces postoperative complications without the need for complex endoscopic equipment [[1], [2], [3]].

This paper aims to describe the surgical technique of minimally invasive carpal tunnel decompression using the KnifeLight. We will detail the procedural steps, assess the advantages of this technique over traditional methods, and evaluate early outcomes to determine its effectiveness in reducing recovery time and improving patient satisfaction. This work has been reported in line with the SCARE criteria [4].

2. Surgical technique:

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  Patient preparation

  • o
    Positioning and Anesthesia: Following anesthesia (general or local), position the patient supine with the arm extended on an armboard. Ensure the palmar surface of the wrist and hand is facing upwards for optimal access.
  • o
    Sterilization and Draping: Sterilize the operative field and drape the patient's wrist and hand, ensuring free access to the palmar aspect of the wrist and hand.
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  Anatomical marking

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    Landmarks (Fig. 1):

    • 1.
      Transverse line at the distal wrist crease over the transverse carpal ligament.
    • 2.
      Palmaris longus line, extending along the axis of the fourth finger.
    • 3.
      Longitudinal line from the radial border of the ring finger intersecting the midpoint of the distal wrist crease.
    • 4.
      Kaplan's line: A transverse line across the palm at the distal border of the outstretched thumb web.
    • 5.
      Line between the pisiform and the head of the second metacarpal bone.

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  Incision and Initial Exposure (Fig. 2)

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    Skin Incision: Make a small 10-mm transverse incision at the midpoint and on ulnar side of the distal wrist crease.
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    Initial Access to the Transverse Carpal Ligament: Create a small opening in the transverse carpal ligament using a fine scalpel or iridectomy scissors.
  • o
    Median Nerve Identification: Under direct visualization, identify the median nerve to avoid inadvertent injury. Introduce a closed scissor to gently recline the palmar cutaneous branch of the median nerve away from the surgical field.

• ▪
  Insertion of KnifeLight Instrument (Fig. 3)

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    Placement of KnifeLight: Insert the KnifeLight instrument into the incision, positioning its blunt plastic tips above and below the transverse carpal ligament. Ensure the longer skid of the KnifeLight is placed beneath the ligament and the shorter skid remains on top.
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    Activation of the Light Source: Dim the overhead lights and activate the KnifeLight's integrated light source to enhance visual clarity of the surgical site.
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    Distal Release of Transverse Carpal Ligament:

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      Protection: Place one hand over the center of the palm to prevent overshooting distally.
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      Cutting Distal Ligament: start advancing the KnifeLight distally, cutting the ligament towards the ulnar side of the palmaris longus tendon and the radial border of the ring finger. Ensure the cut is directed from ulnar to radial, maintaining visualization through the illuminated skids.
  • o
    Proximal Release of Transverse Carpal Ligament:

    • o
      It can be performed using KnifeLight or just a Metzenbaum scissors. Begin dividing the ligament proximally by advancing the KnifeLight in small increments, guided by the illuminated tips. Ensure a controlled, steady movement to avoid nerve injury. Continue advancing until the light is visible at the proximal extent of the wrist.

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  Verification of Complete Ligament Division

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    Visual Inspection: Verify complete division of the transverse carpal ligament by observing the light source along the full length of the tunnel from the wrist to the palm.
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    Palpation: Pass a Macdonald dissector under the divided ligament to check for any remnants that may require further cutting.
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  Final Steps

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    Haemostasis: Once the ligament is fully divided, remove the KnifeLight instrument and achieve haemostasis using electrocautery or pressure.
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    Skin Closure: Close the skin using subcuticular absorbable sutures, ensuring a cosmetic closure with minimal scarring.
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    Dressing: Apply a sterile dressing and small gauze pad to the wound. Avoid heavy immobilization of the wrist and hand.
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  Postoperative Care

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    Early Mobilization: Postoperatively, avoid hand immobilization. Encourage patients to gently use their hands for light activities, avoiding any forceful gripping or heavy lifting for the first 3 weeks.
  • o
    Wound Care: Advise patients to keep the incision clean and dry, and provide instructions for suture care, if necessary.
  • o
    Follow-Up: Schedule follow-up appointments to assess wound healing, confirm recovery of motor and sensory functions, and address any postoperative concerns.

Fig. 1.

Anatomical marking of landmarks.

Fig. 2.

10 mm transverse skin incision at the midpoint and on ulnar side of the distal wrist crease (left) - Introduction of closed scissor to gently recline the palmar cutaneous branch of the median nerve (right).

Fig. 3.

Insertion of KnifeLight Instrument and the activation of the light source (left) – Release of the Transverse Carpal Ligament by advancing the KnifeLight under light control (middle) - Visual Inspection of the transverse carpal ligament by observing the light source along the full length of the tunnel (right).

3. Discussion

Minimally invasive techniques for carpal tunnel release (CTR), such as the KnifeLight-assisted approach, offer several advantages over traditional open and endoscopic methods. This technique merges the benefits of both approaches, providing enhanced safety, reduced scarring, and a quicker recovery for patients, while minimizing the risks associated with blind techniques [3,5].

The KnifeLight (Stryker, Kalamazoo, MI) is a disposable instrument specifically designed for minimally invasive carpal tunnel release. It features a battery-powered light source integrated into the handle, illuminating the surgical site via transparent plastic skids and a cutting blade sandwiched between two blunt skids, enabling controlled cutting of the transverse carpal ligament while protecting surrounding tissues [6].

3.1. Advantages over traditional open CTR

The primary advantage of the open carpal tunnel release technique is the ability to directly visualize the anatomy, allowing for precise identification of vulnerable structures such as the median nerve and palmar cutaneous branch. This reduces the risk of inadvertent injury, a major benefit in carpal tunnel surgeries. However, the open approach requires a larger incision, typically extending beyond the wrist flexion crease, which can lead to unsightly scarring and scar tenderness. The larger wound size also increases the likelihood of prolonged healing times and postoperative complications, such as infection or pillar pain (tenderness over the thenar and hypothenar eminences) [6,7].

The KnifeLight technique, on the other hand, requires only a small incision, hidden in the distal wrist crease, which minimizes postoperative scarring and improves cosmetic outcomes. By limiting trauma to the overlying tissues and making a more discrete incision, this method reduces the likelihood of complications such as pillar pain and scar tenderness. The lighted blade further enhances safety by providing improved visualization during the cutting process, preventing accidental injury to nearby structures [7].

3.2. Comparison with blind techniques

Blind techniques, such as those using a transverse wrist incision, offer the advantage of a smaller incision but carry significant risks of incomplete flexor retinaculum release or inadvertent injury to critical structures like the superficial palmar arch. Studies have shown that blind approaches can result in injury to the superficial palmar arch in 1 out of 28 hands during cadaveric dissections. The flexor retinaculum release may also be incomplete, leading to persistent carpal tunnel symptoms and the need for repeat surgery [8].

In contrast, the KnifeLight technique offers a higher level of safety due to its integrated light source, which allows for precise visualization of the instrument's position relative to the flexor retinaculum and adjacent structures. This reduces the risk of incomplete release and injury to the superficial palmar arch. Furthermore, the KnifeLight's blunt plastic tips, which surround the cutting blade, serve to protect vulnerable structures during ligament division. The illuminated skids make this a semi-blind technique, but the light-guided visualization mitigates many of the risks associated with purely blind methods [7,8].

3.3. Advantages over endoscopic CTR

Endoscopic CTR has been praised for its ability to minimize incision size and reduce recovery time compared to traditional open surgery. However, it has its limitations. Endoscopic approaches can be associated with a higher risk of nerve injuries. Some studies have reported a threefold increase in nerve injury risk with endoscopic CTR compared to open CTR. Injuries to the median nerve, common digital nerves, and the palmar cutaneous branch have all been documented, often due to inadequate visualization during the endoscopic procedure. Additionally, complex anatomical variations, such as a transligamentous or extraligamentous motor branch of the median nerve, can make endoscopic techniques more dangerous [2,9].

The KnifeLight technique combines the advantages of endoscopic visualization with the simplicity of an open technique, without the need for expensive or complex endoscopic equipment. The integrated light source provides sufficient illumination to safely guide the surgeon in dividing the flexor retinaculum while avoiding injury to surrounding structures. Moreover, this technique does not require the prolonged setup time of endoscopic procedures, which can extend surgery times to 20–35 min. In contrast, KnifeLight-assisted CTR typically takes only 5 min, significantly reducing operating time and associated risks [1,3,9].

3.4. Enhanced safety and efficacy

One of the key advantages of the KnifeLight technique is the reduction in risk to vital structures. Studies have shown that the motor branch of the median nerve, which is most vulnerable during carpal tunnel release, lies on the radial side of the line drawn from the third web space to the ulnar border of the palmaris longus tendon. With KnifeLight CTR, strict adherence to anatomical landmarks ensures that the surgeon remains safely within the ulnar side of this line, thus protecting the motor branch of the median nerve. Similarly, the superficial palmar arch, which lies just beyond the distal border of the flexor retinaculum, is also protected due to the improved visualization provided by the KnifeLight [3,7].

This enhanced safety translates to fewer complications and a quicker return to function. In comparison to traditional open methods, where time to return to work can range from 30 to 120 days, KnifeLight CTR patients return to work significantly faster, with average recovery times as short as 7 days. This is comparable to, or even better than, the recovery times reported for endoscopic CTR, which range from 16 to 38 days [7,10].

3.5. Reduced complications and improved recovery

Postoperative complications such as pillar pain and scar tenderness are common concerns following carpal tunnel release surgery. Pillar pain is thought to result from damage to the subcutaneous neural structures during the procedure. With the KnifeLight technique, the minimal incision and careful dissection deep to the palmar fascia reduce the trauma to these structures, decreasing the likelihood of neuroma formation and pillar pain [3,10].

Studies have also shown that smaller incisions, as used in KnifeLight CTR, are associated with faster recovery of grip and pinch strength compared to longer incisions used in conventional methods. This allows patients to regain normal function sooner, reducing the overall socioeconomic impact of the procedure by shortening recovery times and hastening the return to work [1,3,9].

3.6. Cost considerations

While the KnifeLight tool is disposable and costs approximately $60 per unit, the technique's overall cost-effectiveness is improved by its ability to reduce surgical time, minimize complications, and expedite recovery. The faster return to work and reduced need for follow-up interventions make this a cost-efficient option for carpal tunnel release, even when compared to endoscopic techniques, which require specialized equipment and training [1,5].

4. Conclusion

KnifeLight-assisted minimally invasive carpal tunnel release offers significant advantages over both traditional open and endoscopic techniques. The small, well-concealed incision minimizes scarring and reduces the risk of postoperative complications such as pillar pain and scar tenderness. The light-guided cutting instrument enhances safety by providing precise visualization of the surgical site, minimizing the risk of injury to critical structures. Additionally, the shorter operating time and faster recovery allow patients to return to normal activities sooner, making this an efficient and cost-effective option for carpal tunnel release. Although long-term studies with larger patient populations are needed to confirm these findings, preliminary data suggest that the KnifeLight technique is a valuable and safer alternative for treating carpal tunnel syndrome.

KnifeLight-assisted minimally invasive carpal tunnel release offers significant advantages over both traditional open and endoscopic techniques. The small, well-concealed incision minimizes scarring and reduces the risk of postoperative complications such as pillar pain and scar tenderness. The light-guided cutting instrument enhances safety by providing precise visualization of the surgical site, minimizing the risk of injury to critical structures. Additionally, the shorter operating time and faster recovery allow patients to return to normal activities sooner, making this an efficient and cost-effective option for carpal tunnel release. Ideal candidates for the KnifeLight technique include patients with mild to moderate carpal tunnel syndrome who may benefit from faster recovery times and reduced postoperative pain. Patients without significant anatomical abnormalities or complex cases, where visualization and precision are essential, are particularly well-suited for this approach. Although long-term studies with larger patient populations are needed to confirm these findings, preliminary data suggest that the KnifeLight technique is a valuable and safer alternative for treating carpal tunnel syndrome.

Author contribution

Omar Fadili: designed the study, wrote the protocol and the first draft of the manuscript.

Mohammed Khodja: managed the analyses, and the correction of the manuscript.

Mohammad Reza Azarpira: managed the analyses, and the correction of the manuscript.

Consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Ethical approval

This study is exempt from ethical approval from the institution: Service de Traumatologie Orthopédie et Chirurgie Réparatrice - Centre Hospitalier Universitaire Ibn Rochd de Casablanca.

Guarantor

Omar Fadili.

Provenance and peer review

Not commissioned, externally peer-reviewed.

Research registration number

None.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Conflict of interest statement

None.