Tunneling Wounds 101: Essential Tips for Practitioners

The skin is the largest organ in the body and provides an effective barrier between the body and potential harmful forces, which makes it a very important organ to keep working properly and healthy. Maintaining skin integrity is crucial to overall function of most bodily systems. Everyone has experienced wounds, most of which do heal with minimal effort. But when the need arises, healthcare practitioners get involved for more severe or complex wounds. Of those treated frequently by practitioners, one category of wounds, tunneling wounds, provides particular challenges for both the patient and their healthcare provider.

Just what are tunneling wounds? They’re not your everyday scrape or slice, or as broad as diabetic ulcers or pressure injuries. Also called sinus tracts, this type of wound often results from a chronic wound or slow-healing injury. Ulcers and sores that remain exposed can lead to persistent inflammation and wound changes, which in turn encourage the formation of tunnels.

Tunnels are usually narrow channels or tracts that extend deep into the surrounding subcutaneous tissue or muscle, as the name might suggest. These tunnels create pockets or passages in the underlying tissue, which can present a complication to the wound’s healing. To make matters worse, the tunnel’s path can be tortuous and unpredictable. The pockets created by these wounds are an ideal environment for bacterial growth, increasing the risk of infection and subsequent delayed wound closure. 

Practitioners should also know what an  undermining wound is. These are similar, but undermining wounds actually refers to the dead space under the wound edges, which creates a shelf. These wounds are often also classified as tunneled, as the wound can then extend beyond the shelf in any direction.

Causes and Risk Factors of Tunneling Wounds

Several factors increase the risk of developing tunneling wounds: preexisting conditions, wound-related factors, patient-related factors, and environmental factors.

Treating tunneling wounds involves addressing the underlying causes and managing infections effectively to optimize healing and improve patient outcomes.

Pre-Existing Conditions

These factors tend to be chronic, so unfortunately, these should be monitored frequently to catch deep wounds and tunneling wounds early.

• Pressure injuries, particularly those in stage III or IV
• Diabetes – with poor circulation and nerve damage as sequelae of this disease, diabetic foot ulcers are common sources of tunneled wounds
• Vascular insufficiency
• Inflammatory conditions (e.g. hidradenitis suppurativa)
• Malnutrition – deficiencies in several vitamins and minerals, especially zinc, can increase the risk of tunneling wounds
• Obesity
• Alcohol use disorder
• Drug interactions (corticosteroids, NSAIDs, chemotherapy or immunosuppressants)

These factors are a bit more acute, as they only present once a wound has formed.

• Prolonged inflammation
• Immobility – those who are bedridden or have mobility limitations are susceptible to pressure injuries, which, as previously mentioned, can lead to tunneling
• Incontinence – prolonged exposure to urine and feces can lead to skin breakdown, causing open sores, especially for those who are immobile, as above

Environmental Factors

Somewhere in the middle of the two above categories, these factors are always present, but may not always present an imminent risk of forming tunneling wounds on the surface of the skin.

• Improper wound care – this can be caused by under or overpacking the wound
• Inadequate pressure mobilization – especially with pressure injuries, alleviating the cause of the pressure is necessary for healing
• Excessive moisture or dryness around the wound

Knowledge of these risk factors and conditions will help practitioners anticipate those most at risk and assist in managing tunneling wounds and those they stem from.

Diagnosis and Treatment

Diagnosis of tunneled wounds is essential for developing the most effective treatment plan, especially when they stem from other existing wounds which may already have a path to treatment. Initial and subsequent examinations should involve the following:

1. Visual examination: Inspect wound and surfaces for possible tunneling.
2. Probing: Use a soft, non-fibrous probe such as a soft polyethylene catheter to assess the location and depth of the wound. While depth is important in assessing all wounds, the deep and winding shape unique to tunneling wounds is key to diagnosis.
3. Measurement: For tunneled wounds, the clock face method is most commonly used to indicate the location and depth of the wound. Using 12:00 as the head of the patient, document the time and length. For example: 12:00, 2 cm.
4. Imaging: Visualization may not be sufficient, especially for tunneling wounds, which may be deeper, hard to see, or obscured by another wound they stem from, like a bed sore. Often, CT or MRI are necessary for complete assessment.
5. Tissue assessment: Evaluate for possible infection, necrosis, or dead tissue.
6. Exudate evaluation: Assess color, amount, and consistency. Differences in type of exudate can indicate different types of wounds and stages of healing.
7. Pain Assessment: Document pain levels before and during examination.
8. Photographic Documentation: Take photos to track wound progression, and always measure to document changes.

Consistent practice of these elements will assist all team members involved in the treatment. One protocol for wound assessment is the ABCDEFGHI approach, developed to create an easy-to-remember and follow process for clinicians that combined international best practices and outcomes.

Complications and Prognosis

Tunneled wounds are already a complication from other wounds, but, left untreated or improperly managed, can cause other problems, such as increased infection, delayed wound healing, abscess formation, tissue necrosis, and even sepsis.

The prognosis for treating tunneled wounds depends on many factors, including the underlying cause, patient factors, and the quality of care. Disruptions in the healing process can lead to more severe complications, so maintaining proper wound care practices and monitoring is crucial. With proper treatment, tunneled wounds can heal successfully, though it may take weeks or even months for this to occur. Luckily, there are standard and up-and-coming treatment options available to practitioners.

Treatment Approaches

Treatment of tunneled wounds is multifactorial and needs to be tailored to each patient, adjusting as needed as healing progresses.

Employing effective strategies is crucial to optimize wound healing.

Wound Cleansing and Debridement

Thorough cleansing and debridement must be used regularly to remove necrotic tissue and address damage across tissue layers. This helps reduce the bacterial load and promotes healthy granulation. Techniques such as irrigation with sterile saline and enzymatic and mechanical debridement are used most often, but other techniques are also available if needed.

Wound Packing

Proper packing of these wounds will promote healing and prevent premature closure of the skin surface. In preparation for packing wounds, consider the choice of packing materials (antimicrobial gauze, alginate ropes), and ensure that the packing material is sufficient without overpacking. Packing material should be changed at appropriate intervals to maintain a moist, but not wet, wound environment.

In choosing the proper dressing for these, the following factors must be considered: the absorbency level to manage exudates, antimicrobial properties to prevent further infection, and ease of application and removal.

Advanced Wound Treatment Techniques

In addition to basic wound cleansing and debridement as described above, other advanced techniques exist to help with healing, especially for complex injuries like tunnel wounds.

Negative Pressure Wound Therapy

Negative pressure wound therapy (NWPT) is a technique that can be effective for complex tunneling wounds. It uses controlled negative pressure on the wound bed, promoting granulation tissue formation. If used properly, it also helps reduce edema and bacterial colonization, helping create wound contraction.

NPWT should be considered for wounds that have not responded to conventional treatment or those with significant tunneling.

Medication Management

The choice of antibiotics, both systemic and topical, are another component of wound treatment, and this remains true for tunneling wounds. In addition to antibiotics, pain management and medication should be considered, especially during wound dressing changes.

Surgical Interventions

Despite optimal care, many complex wounds end up requiring surgical intervention. This may be necessary to further excision necrotic tissue or close deep tunnels. In particularly difficult cases, flap procedures for large defects may be required for complete healing.

Wound Care Best Practices

Evidence-based techniques that should be applied to wound management, regardless of whether they’re tunneling or not, include maintaining wound moisture, infection, control measures, pressure redistribution, management of comorbidities, and careful monitoring and follow-up. Wound tunneling, characterized by a narrow channel extending from the wound’s surface into deeper tissues, often seen in conditions such as pressure ulcers and diabetic foot ulcers, requires particular attention to infection management and thorough wound assessment. Wound care clinicians would consider these their bread and butter, but they’re important for practitioners of all specialties to keep in mind when treating a patient with a significant wound.

Wound Environment Moisture

Maintaining a moisture balance is necessary for tissue granulation and epithelialization. Healthcare personnel should choose dressings that help maintain moisture and avoid overdrawing and possible wound maceration. On top this, exudate needs to be monitored carefully to make sure healing is progressing.

Infection Control Measures

As these wounds are already often the result of infection, care must be taken to avoid further infection by maintaining strict hygiene and aseptic techniques. Monitor medication to make sure it’s the best fit for the patient’s condition.

Redistribution of Pressure

For pressure wounds, pressure-relieving strategies can include specialized support surfaces (e.g., air-fluidized beds), regular repositioning schedules, and education of patients and family members on proper positioning.

Management of Comorbidities

Dietary supplements, such as proteins, vitamins, and minerals, should be added to the regimen for diabetic patients and those with poor nutritional status. If necessary, consult with a dietitian for complex cases.

Monitoring and Follow-up

Even in the best of circumstances, these wounds will require lengthy follow-up. Regular wound assessments should be made at least weekly, including documentation of wound changes such as size, depth, and appearance. Healthcare providers should be prepared to modify treatment approaches if the wounds fail to show signs of improvement within two to four weeks.

Prevention Strategies

Not all tunneling wounds can be prevented, but certain proactive strategies can be used to reduce their incidence. Prevention is always preferable to treatment when possible, so these are important to keep in mind, especially when risk factors are present.

• Conduct regular assessments for high-risk patients
• Use pressure redistribution protocols
• Provide patient education on proper skin and wound care
• Address comorbidities that may contribute to poor or delayed wound healing
• Ensure adequate nutrition and hydration for all patients

Potential New Treatments

Wound management research continues on several platforms. While some address healing, others involve assessment by both providers and patients.

Skin Temperatures

One promising area of development is skin temperature assessment. Research has shown that increasing skin temperature can indicate the presence of inflammation or infection. In a 2023 study, a wearable device made of fabric was used to monitor skin temperature and electrical skin impedance, giving clues to areas at risk for pressure ulcers and tunneled wounds.

At the Medical University of South Carolina, nurse researchers used infrared thermometers to assess skin temperature and trained patients to monitor at home using this technique.

Use of Active Coagulation Whole Blood Clot

Another emerging approach is active whole blood coagulation clot therapy. This involves using the patient’s blood to create a clot, which is applied directly to the wound site. It results in a fibrin-rich clot containing growth factors and other molecules that are important in wound healing.

Use of Silver-Impregnated Glass Fibers

A technique combining the antimicrobial properties of silver with bioactive glass addresses two critical components of wound healing: tissue regeneration and infection control.

When in contact with biological fluids, bioactive glass forms a layer that increases bonding with soft tissues, stimulating natural healing processes. The addition of silver to these fibers adds an antimicrobial component that may help prevent infection. Known for its broad-spectrum antibacterial properties, silver is effective against many resistant strains of bacteria.

Tunneling Wounds Are Complex, But Not Impossible

Tunneled wounds are complicated and challenging for the healthcare team as well as the patient, but both standard and advanced treatment options are available. Effective wound treatment involves a multidisciplinary approach, including wound specialists, nursing, nutrition, pharmacy, and physical therapy. As previously mentioned, these wounds can take weeks or months to heal. Having a solid team approach, including patient education, can make this process smoother for everyone involved and hopefully result in a fully healed patient.ists, nursing, nutrition, pharmacy, and physical therapy. As previously mentioned, these wounds can take weeks or months to heal. Having a solid team approach, including patient education, can make this process smoother for everyone involved and hopefully result in a fully healed patient.