The efficacy of negative‐pressure wound therapy for head and neck wounds: A systematic review and update

Despite the established benefits of negative‐pressure wound therapy (NPWT) in various wound healing contexts, its application in head and neck surgical cases remains under‐explored. This study aimed to systematically review its effectiveness, safety, and comparative efficacy. Thirty‐one studies from a systematic literature search were identified and analyzed for wound healing response, overall success rate, improvements compared to conventional wound care, and variation in pressure settings, treatment lengths, and dressing change frequency. NPWT showed enhanced outcomes across diverse head and neck wounds, particularly complex post‐reconstructive wounds and severe infections. Despite the predominantly case report/series evidence and lack of standardized NPWT protocols, its benefits over conventional care were clear. NPWT emerges as a promising approach for head and neck wound management, potentially improving patient outcomes and reducing complications. More randomized controlled trials are needed to solidify the evidence and standardize NPWT application protocols.


| INTRODUCTION
Negative-pressure wound therapy (NPWT) is a method involving a vacuum pump connected to a topical negative-pressure dressing to apply subatmospheric pressure to a wound site (see Figure 1). 1 Despite its widespread use in treating acute and chronic wounds on the torso and limbs, NPWT has been underutilized in head and neck surgical cases. 2 NPWT can benefit various head and neck wound types, such as extensive resections, postoperative radiotherapy, comorbidities, and traumatic or infectious wounds. 3,4It can aid wound healing by promoting granulation tissue formation, reducing oedema and bacterial colonization, and increasing local blood flow. 2 NPWT also effectively treats burns 5 and reduces inflammatory mediators. 6owever, NPWT has contraindications, such as residual tumor in the operative bed 7 and ischemic or necrotic tissue. 4PWT can be used in various regions of the face, including the upper, middle, and lower thirds, 8,9 as well as neck reconstruction. 2,10,11Challenges include maintaining an occlusive seal, especially in the middle third, due to facial contours, hair-bearing skin, and facial movements. 2,4,7The complex anatomy of the region also presents difficulties in filling deep spaces with foam material. 124][15] However, this systematic review tries to encompass all of those elements.
This study aims to: • Evaluate the latest evidence on NPWT's effectiveness in promoting wound healing outcomes in head and neck wounds, including time to healing, wound closure/response rates, and complications.• Assess the safety and adverse events associated with NPWT in head and neck wounds.
• Determine, if possible, whether NPWT compared to standard wound care without NPWT results in better wound healing outcomes based on comparative studies.

| METHODS
Per the PRISMA guidelines, the review protocol was registered on the International Prospective Register of Systematic Reviews (PROSPERO) before commencing the study.The registration number is CRD42023402451.
A systematic search of the PubMed, Cochrane and Web of Science databases was conducted using the search terms "((Negative pressure wound therapy) OR (Negative pressure wound dressings) OR (vacuumassisted therapy) or (VAC)) AND ((face) OR (facial) OR (head and neck))."Cochrane's Covidence software was used to review the search-identified 351 studies.After applying inclusion and exclusion criteria and conducting full-text screening, 31 studies were included (see Figure 2).This paper aims to update the latest evidence on using negative pressure to treat recalcitrant head and neck wounds.Original research papers from the last 5 years focusing on human subjects, both adult and pediatric, were included, while animal studies, review articles, and reports of the use of NPWT on body areas other than the head and neck region were excluded.
A similar review was last conducted by Mir et al.  (2019).It should be noted that while that paper was accepted for publication in 2018, its last search was run up to the 30th of July 2017. 4Therefore, in this study, the searches in PubMed, Cochrane, and Web of Science databases were run from the 30th of July 2017 to the present (date of last search: 12th of February 2023).
Data collected on all included studies can be found in Table S1, Supporting Information.Study type, primary patient pathology, age, wound site, treatment length, pressure settings used, response to therapy, associated complications, risk factors affecting wound healing, and time to follow-up were considered.
Notably, while most units used in all domains were the same across studies, some discrepancies were present F I G U R E 3 Bubble chart showing the frequency of pathologies in studies of NPWT.The size of each bubble represents the number of papers that studied each wound type, and the color intensity represents the sample size of patients with that pathology across the papers in the review [Color figure can be viewed at wileyonlinelibrary.com] in the frequency of dressing changes during NPWT.To address this issue, data were standardized for comparison and clarity wherever possible.
Many studies used NPWT until enough granulation tissue formed for reconstruction, allowing healing to complete.Thus, treatment was considered successful (response = 100%) if the NPWT achieved its intended goal (e.g., granulation tissue formation or full closure) and 0% otherwise, unless the cohort was larger and otherwise specified.
Missing data was noted down as "NR"-for not recorded.
To assess the quality of the identified literature, three different risk-of-bias assessment tools were chosen: • The Cochrane Risk of Bias tool was used to assess the randomized controlled trials (RCTs). 17 19 The primary outcome measures were wound healing response and duration of NPWT.

| RESULTS
Thirty-one studies were included in this review.Significant heterogeneity existed between study types, with 11 case reports, 14 case series, 4 cohort studies, and 2 randomized controlled trials identified.

| Patient and wound characteristics
The review encompassed 371 patients treated with NPWT, consisting of 112 females and 259 males, with a mean patient age of 50.6 years.Deep neck space infections and abscesses were the most frequent pathologies, followed by postreconstructive fistulae and other complex wounds (Figure 3).Wound size was seldom recorded (only in 3 case reports).
Diabetes mellitus, radiotherapy, nicotine-containing product use, and high disease stage were the most frequently reported risk factors in this patient cohort, along with disorders compromising immune function (Figure 4).Five of the 31 studies did not record any comorbidities or risk factors for poor wound healing.

| Treatment settings and outcomes
Pressure settings used in the studies ranged between À50 and À200 mm Hg.The mean treatment length across all pathologies was 13.83 days.The overall wound healing response was 91.72% (see Table S1).
There was considerable variation in the frequency of dressing changes across the studies (see Figure 5), highlighting the lack of a standardized approach to wound care in the reviewed literature.
Ten studies reported no complications, while 11 did not report whether or not complications occurred.Pain was the most frequent complication (reported in only two studies), with contact dermatitis or other irritation due to the dressing reported in a few cases.Treatment had to be discontinued in only two patients (0.54%).In one fistula case, negative pressure was prematurely discontinued, resulting in the reopening of the fistulas, and treatment had to be restarted. 11Although it is difficult to comment reliably on complication rates, as so few studies reported them, previous studies have reported local skin complication rates like ulcers, infection, and wound dehiscence between 1.3% and 5.3%. 20llow-up ranged from 2 weeks to 21 months.However, most of the included studies (58%) did not report the length of follow-up.

| Comparative outcomes
A summary of the outcome measures examined by the comparative studies in this review is provided in the table below (see Table 1).Most studies compared NPWT to a control group of regular wound therapy, while Liu et al. ( 2021) compared simultaneous VAC placement to staged application. 21The multi-irrigation drain system values in Qian et al. 22 were not included but will be explored later.
These results demonstrated a clear advantage of NPWT over conventional wound care across multiple parameters.Healing time, hospitalization days, and duration of antibiotic administration were generally shorter in the NPWT group compared to the control group, with most studies showing significant differences.This improvement was further supported by a significant reduction in dressing changes and medication days observed in most studies for the NPWT group.
Additional findings highlighted the benefits of NPWT in various aspects of patient outcomes.Pain scores and scar lengths were significantly lower in the NPWT group, as reported by Zhimin et al.Furthermore, the recurrence ratio and pharyngocutaneous fistula formation were notably lower in both RCTs. 23,24Gu et al. found that white blood cell (WBC) counts after the operation were significantly lower in the NPWT group. 26Additionally, the frequency of MIC (times/day) and the number of debridements required were significantly lower in the NPWT group, as reported by Qian et al. and Liu et al., respectively. 21,22Lastly, Lin et al. identified significantly higher complication and infection prevention rates associated with NPWT compared to conventional wound care. 27However, many outcomes, such as mean time to recovery, dressing change time, and cost of treatment, were not significantly different between the groups in some studies.

| Assessments of study quality
The high heterogeneity among the studies made comparisons between study types more difficult.2, Assessments showed most studies to have at least one domain at a high or unclear risk of bias.The average MINORS score for the non-case report non-randomized studies was 13.6 out of a maximum of 24.Given that most of these studies were non-comparative and thus were limited from the outset in the number of points they could score, this is actually quite high.However, it indicates a need for more robust study design.Additionally, most of the studies' risk of bias originated from a lack of assessment of study endpoints, lack of information about statistical significance, and lack of follow-up.

| DISCUSSION
This review demonstrates that NPWT is an effective tool for aiding wound healing in various complex head and neck wounds.Previous reviews like the one by Mir et al. found that the largest numbers of NPWT studies in this region focused on neoplastic disorders, post-reconstructive fistulae, infections, trauma (from dog bites to gunshots, burns, and blast injuries), osteonecrosis and flap failure.This study has built upon this, showing that in the last 5 years, NPWT continues to be used in a wide range of non-healing wounds, particularly post-reconstructive fistulae, chylous leaks after neck dissection and other postoperative wounds, as well as deep neck abscesses, necrotising fasciitis, and in trauma. 4dditionally, this review has identified several novel indications for NPWT, such as treating non-healing wounds with foreign body exposure, specifically cochlear implant hardware.Using NPWT in these cases has shown promise in preserving the cochlear implant without resorting to explanation, which can lead to cochlear fibrosis, ossification, and other complications.
Another innovative application of NPWT is its use directly over near full thickness eyelid loss.This approach has been reported in a case study by Gillespie et al., where specific adjustments, such as tarsorrhaphy and milder pressure settings, were implemented to ensure patient safety. 32The success of this treatment underscores the potential for NPWT in managing a wider range of head and neck wounds.
In terms of outcomes, NPWT is associated with improved wound healing, reduced infection rates, and better overall success than conventional wound care methods.This may largely be attributed to providing continuous or intermittent negative pressure, promoting granulation tissue formation, enhancing perfusion, and removing infectious materials and wound exudate. 24he amount and manner of exerting pressure on the wound remain points of contention on a broad range of

Note:
The table details the comparisons made in each study, the outcomes measured, the interventions and controls used, and the significance of the results.used pressures.Many studies ignore the question entirely, and while some authors report improved results with intermittent cyclic patterns and an optimum pressure range of À80 to À125 mm Hg, 24 these are both variables that are difficult to determine in isolation, as so many other factors influence wound healing.Meanwhile, Ngo et al. advocate that settings should be considered individually for each wound and patient to ensure treatment is tailored to that specific situation. 36This may be true to a minor extent; however, the wide variation between studies highlights the need for more standardized approaches to NPWT in head and neck wounds.
Similarly, there were mixed opinions on irrigation.On the one hand, authors like Cao et al. warn that in their experience, the benefits of washing away pathogens, pus, clots, and necrotic tissue from infected wounds may be outweighed by the fact that it causes a degree of trauma in its own right and thus may interrupt the healing process and increase the odds of secondary swelling. 12owever, on the other hand, Qian et al. were such firm believers in the benefits of irrigation that they created a custom-made multifunctional irrigation-assisted vacuum drainage device which permits continuous irrigation. 22heir comparative study demonstrated the positive effect of reduced hospitalization time.They argued that their technique is more atraumatic than foam alone, as that needs to be changed frequently, without irrigation.
Despite the heterogeneity in treatment settings and wound care approaches, the overall success of NPWT in managing head and neck wounds is evident.However, establishing standardized protocols for pressure settings, treatment durations, and dressing change frequencies could further optimize treatment outcomes and facilitate study comparisons.

| LIMITATIONS OF EVIDENCE INCLUDED
NPWT is useful for many aspects of wound reconstruction.However, more robust studies with larger sample sizes conducted in a randomized controlled fashion are needed.This review has identified two RCTs conducted in this time frame and several cohort and case-control series.However, the majority of the literature in this field remains in the form of published case reports and case series.Furthermore, only 7 of the included 31 studies had a comparative element.Additionally, not all of them were comparing the same factors, making meaningful meta-analysis impossible.
Additionally, there were no patient perspectives in the included studies, and the only patient-reported measures included were related to assessing pain as a complication of the NPWT.

| IMPLICATIONS OF THE RESULTS FOR PRACTICE, POLICY, AND FUTURE RESEARCH
Although complications associated with NPWT are generally infrequent and minor, they bear mentioning.Pain, skin irritation, maceration, necrosis, bleeding, retained sponges, device malfunction, infection, and hemodynamic instability have all been reported. 4,33However, beyond these general complications, there are specific contraindications and precautions to consider, especially in the head and neck region.Direct application of NPWT over exposed or unprotected blood vessels can lead to severe bleeding due to erosive forces.It is paramount to ensure that major vessels, such as the carotid artery, are adequately protected before initiating NPWT. 6,30This is particularly crucial for patients with coagulopathies or those on anticoagulant therapy. 26Another concern is patients with high-output fistulae, who must be closely monitored to ensure fluid loss does not lead to hemodynamic instability. 3An absolute contraindication is the presence of residual malignancy in the wound, as NPWT might stimulate the proliferation of malignant tissue and thus these patients should be excluded. 7,35Steps can be taken to minimize the risk of complications, such as using lower negative-pressure settings, shielding the great vessels with non-permeable foam or a Vicryl mesh that may be integrated into the surrounding tissues. 6,30atients should also be reminded to visually monitor the area and report any early signs of trouble. 20echnical challenges, such as leaking, which occurs in 4.8% of cases, 36 must be addressed.To optimize seal formation, having a wide and well-shaved area surrounding the injury is beneficial, as is trimming the film around anatomical structures and removing hair carefully at every dressing renewal. 37Developing more malleable or shapeable foams to fit the head and neck contours could better facilitate the use of NPWT in maxillofacial applications. 2However, Cao et al. suggest that perceived challenges related to contouring foam correctly are driven by the surgeon's training in pre-shaping membranes and foam, suggesting the importance of staff education in NPWT application. 12linicians could also consider using portable rather than just bedside devices, as the advent of portable VAC devices has allowed patients to be discharged home with the NPWT device and continue ambulatory treatment. 20,31However, this may present both patient coping and funding challenges and thus should be considered on a case-by-case basis.
Future studies on NPWT should include information on the length of hospitalization and length of ICU stays if applicable, duration of antibiotic therapy, specific instillation liquids, frequency of dressing changes, and details of complications and follow-up.More robust studies with larger sample sizes conducted in a randomized controlled fashion are needed to strengthen the evidence base for NPWT in head and neck wound management. 4

| CONCLUSION
Despite limitations in the current evidence base, primarily the prevalence of case reports and case series, NPWT has shown consistent improved outcomes compared to traditional wound care methods in managing head and neck wounds.The versatility of NPWT in managing a broad range of wound types, from post-reconstructive fistulae to necrotising fasciitis, underlines its potential in this area.
The advent of portable VAC devices has opened a new chapter in the applications of NPWT as the patients can be treated on an ambulatory basis, thus reducing extra length of hospital-stay and associated costs.Obviously such ambulatory arrangements pose their own challenges as they require the patient's compliance and patient and staff education for potential early warnings of NPWT failure or wound infection.
Equally, the development of more malleable or shapeable foams, with a softer texture to ensure watertight closure without irritating the skin, could enhance the applicability and effectiveness of NPWT in maxillofacial applications.Particularly considering the thinner skin of the facial area and its significantly more complex 3D structure compared to the upper or lower extremity, these modifications are of paramount importance.Custommade devices, designed to cater to this intricate region, could therefore lead to improved treatment outcomes and user experience, positioning NPWT as an increasingly attractive option for clinicians.
Nonetheless, there is a pressing need for more robust research, including well-designed randomized controlled trials with larger sample sizes, to consolidate the evidence for NPWT in head and neck wound management.These would likely need to focus on specific patient populations and pathologies initially in order to build up a sound evidence base.Such research should also strive to establish standardized protocols for pressure settings, treatment durations, and dressing change frequencies to optimize treatment outcomes and facilitate comparison across studies.In the future, this may also include incorporating patient perspectives and patient-reported outcomes in NPWT research as a means of providing a more comprehensive understanding of its impact.This could further aid the development of best practice guidelines and patient-centered care in the application of NPWT for head and neck wounds.

F I G U R E 1
Pathophysiology of accelerated wound healing under negative pressure [Color figure can be viewed at wileyonlinelibrary.com]

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I G U R E 2 PRISMA 16 flow diagram of article selection process [Color figure can be viewed at wileyonlinelibrary.com]

F I G U R E 4
Frequency of poor wound healing risk factors [Color figure can be viewed at wileyonlinelibrary.com] -and-whisker plot illustrating the variation in the frequency of dressing changes per week for wounds treated with NPWT across the reviewed studies.The plot displays the interquartile ranges for both the minimum and maximum reported frequencies of dressing changes.The range between minimum and maximum changes highlights the variability in treatment protocols, suggesting differences in clinical practices, patient experiences, and resource allocation [Color figure can be viewed at wileyonlinelibrary.com]T A B L E 1 A summary of the studies included in this systematic review that examined outcomes in a comparative fashion sealing drainage and primary wound suture vs. control group abscess incision and drainage first, with secondary wound suture after 3-5 daysHealing time (day)

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I G U R E 6 A summary of risk of bias & quality assessments of included studies [Color figure can be viewed at wileyonlinelibrary.com]