Healing Under Pressure: Effectiveness of Negative Pressure Wound Therapy in the Management of Complex Lower-Limb Wounds

Wounds do not fail to heal all at once. They stall. Sometimes quietly. Sometimes after appearing stable for weeks. In surgical practice, this pattern is familiar, especially in lower-limb wounds associated with diabetes, trauma, or infection. These wounds occupy beds, consume time, and resist closure longer than expected. In many cases, the initial insult is not the problem. The environment that follows is.^[1]

 

Normal wound healing depends on a sequence of events that is well described but easily disturbed. Inflammation settles. Cells proliferate. New vessels form. Remodeling follows. In reality, this sequence is rarely allowed to progress without interruption. Persistent edema, repeated contamination, and poor perfusion interfere early, often before granulation becomes established.^[2] Once this disruption occurs, the wound shifts course. Healing slows. Dressings multiply. Outcomes drift.

 

Wet-to-moist dressing (WMD) remains widely used in such situations. It is simple, accessible, and familiar. Yet familiarity does not imply adequacy. While moisture is maintained, other contributors to delayed healing are largely untouched. Exudate accumulates. Dressings require frequent changes. Newly formed tissue is exposed repeatedly. Over time, the wound bed improves, but often not enough. Progress is incremental and uncertain.^[3]

 

Negative pressure wound therapy (NPWT) was introduced to address these gaps rather than to replace conventional care outright. By applying controlled sub-atmospheric pressure within a closed system, NPWT alters several wound characteristics simultaneously. Excess fluid is removed. Tissue edema decreases. Mechanical forces act directly on the wound surface. At the cellular level, these forces influence fibroblast behavior, angiogenesis, and matrix deposition.^[4] These mechanisms are not speculative. They have been demonstrated consistently across experimental and clinical studies.

 

Clinical comparisons between NPWT and traditional dressings have repeatedly shown differences that matter in practice. Wounds treated with NPWT tend to contract earlier. Granulation appears sooner. Readiness for definitive coverage is achieved faster.^[5] In diabetic foot ulcers, where vascular compromise and neuropathy complicate even minor wounds, randomized trials have shown higher closure rates and reduced time to healing with NPWT compared to standard dressing protocols.^[6]

 

In the Indian clinical setting, these observations carry additional relevance. Diabetic foot disease is common, often advanced at presentation, and frequently managed in overcrowded surgical units. Prolonged inpatient care is rarely feasible. Delays increase cost, infection risk, and patient attrition. Techniques that shorten the interval between debridement and definitive closure therefore assume practical importance. Despite increasing use of NPWT, objective outcome data from routine surgical practice remain limited.

 

The present study was undertaken to evaluate the effectiveness of negative pressure wound therapy in the management of complex wounds. Healing was assessed using measurable parameters, including reduction in wound surface area, reduction in wound volume, and progression of granulation tissue formation. These outcomes were examined against conventional wet-to-moist dressing benchmarks, with the intention of assessing clinical performance rather than theoretical advantage.

This study was designed as a longitudinal prospective observational analysis conducted in the Department of Surgery at K S Hegde Hospital, Mangalore. Patients presenting with complex wounds requiring active surgical management were evaluated in both outpatient and inpatient settings over the study period from August 2024 to August 2025.

 

A total of forty patients were included. Selection was performed using a random sampling approach from eligible cases encountered during routine clinical practice. Both male and female patients below the age of eighty years were considered. Wounds eligible for inclusion measured between 5 × 5 cm and 20 × 20 cm and included arterial ulcers, venous ulcers, neuropathic ulcers, and traumatic wounds involving the lower limb. Patients above eighty years of age who were deemed unfit for surgical intervention were excluded.

 

Initial wound assessment focused on size, depth, tissue viability, and presence of necrotic material. All patients underwent surgical debridement as required, followed by a period of daily conventional dressing for one week. This phase was intended to stabilize the wound bed, control overt infection, and allow demarcation of non-viable tissue before definitive therapy.

 

Negative pressure wound therapy was then instituted using a vacuum-assisted closure system. The wound was covered with a sterile foam dressing tailored to wound dimensions and sealed with an occlusive adhesive drape to ensure an airtight environment. Controlled sub-atmospheric pressure was applied continuously. Dressings were changed at regular intervals, and the wound bed was reassessed at each change.

 

Wound healing was evaluated using objective parameters. Surface area reduction was assessed by measuring wound dimensions at predefined time points. Wound volume was estimated clinically based on depth and area progression. Granulation tissue formation was documented as a percentage of the wound bed showing healthy granulation. Assessments were performed serially over a 20-day period following initiation of negative pressure therapy.

 

Clinical endpoints included reduction in wound size, improvement in granulation tissue coverage, readiness for split-skin grafting, and overall progression toward definitive closure. Adverse events, if any, were noted during follow-up.

 

All observations were recorded systematically and compiled for comparative analysis against conventional wet-to-moist dressing outcome benchmarks derived from established clinical data.

 

Table 1 summarizes the demographic profile and baseline wound characteristics of the study population.

 

The diversity of wound types allowed evaluation of NPWT performance across different pathological backgrounds rather than a single disease subset.

 

Reduction in Wound Surface Area

Progressive reduction in wound surface area was observed following initiation of negative pressure wound therapy. Improvement was evident as early as day 7 and continued steadily through day 20. The pattern of reduction was gradual rather than abrupt, suggesting sustained biological response rather than transient contraction.

 

By day 20, mean surface area reduction approached 30%, indicating meaningful wound contraction sufficient to influence reconstructive planning.

 

These changes are illustrated in Graph 1, while comparative outcome benchmarks are summarized in Table 2.

 

Bars represent mean percentage reduction at each time point (Day 0, Day 7, Day 15, Day 20). Values are displayed above each bar.

 

Reduction in Wound Volume

Wound volume reduction followed a trajectory similar to surface area changes but with a slightly steeper slope over time. Early reduction was modest, but by day 20 a marked decrease in wound depth and cavity size was evident clinically.

 

Mean volume reduction reached approximately 35% by day 20, reflecting effective control of edema and progressive tissue infill. This reduction was particularly notable in deeper wounds, where volume change carries greater functional significance than surface contraction alone.

 

Volume changes are depicted in Graph 2 and summarized alongside surface area outcomes in Table 2.

 

Each segment represents incremental volume reduction at successive time points. Percent values are shown above segments.

 

Granulation Tissue Formation

Granulation tissue development showed the most pronounced response to negative pressure therapy. Early granulation was visible by day 7, expanding steadily across the wound bed with continued therapy. By day 20, approximately 65% of the wound surface demonstrated healthy granulation tissue.

 

This progression translated clinically into earlier readiness for split-skin grafting and reduced need for prolonged interim dressing.

 

Granulation trends are illustrated in Graph 3, while overall outcome comparison is detailed in Table 2.

Segments represent percentage of granulated versus non-granulated wound bed. Percentages are indicated in bold.

 

Comparative Outcome Analysis: NPWT versus Conventional Dressing Benchmarks

When outcomes achieved with NPWT were compared against established wet-to-moist dressing benchmarks, NPWT consistently demonstrated superior performance across all measured parameters.

 

Surface area reduction, wound volume reduction, and granulation tissue formation were all significantly greater in the NPWT group. These differences were not marginal. They were clinically apparent and influenced downstream decisions regarding grafting and discharge planning.

 

 

The relative contribution of each healing parameter to overall improvement is visualized in Graph 4.

 

Each slice represents relative improvement in surface area, volume, and granulation. Percent values are displayed clearly.

 

Clinical Outcomes and Surgical Implications

Reduction in wound size and accelerated granulation translated into tangible clinical benefits. Several wounds achieved readiness for split-skin grafting earlier than anticipated. Hospital stay was reduced, and postoperative recovery following grafting was uncomplicated in the majority of cases.

 

No significant adverse events attributable to negative pressure therapy were observed during the study period.

 

Table Linking Outcomes to Clinical Impact

To contextualize numerical outcomes within surgical decision-making, Table 3 summarizes the practical implications of NPWT-related improvements.

 

 

Clinical Photographic Documentation of Wound Progression

Serial clinical photographs were used to document wound bed changes following negative pressure wound therapy across different wound etiologies. These images provide visual confirmation of granulation tissue development, wound contraction, and readiness for split-skin grafting.

 

 

 

 

 

 

Figure 1 demonstrates a large wound over the right dorsum of the foot showing healthy granulation following NPWT and subsequent split-skin grafting. Progressive wound stabilization and surface contraction are evident.

 

Figure 2 illustrates a left-sided below-knee guillotine wound after two weeks of NPWT, highlighting uniform granulation and reduction in wound depth.

 

Figure 3 documents NPWT application following a snake bite injury of the left foot, with post-grafting epithelialization observed at one-month follow-up.

 

Figure 4 depicts an avulsion injury of the left foot and the corresponding post-split-skin graft outcome in a diabetic patient, demonstrating satisfactory graft uptake.

 

Figure 5 shows a bull-related injury over the left perineal region, where NPWT facilitated wound bed preparation prior to definitive coverage with split-skin grafting.

 

Together, these images corroborate the quantitative findings by demonstrating consistent wound bed optimization and progression toward definitive closure following NPWT.

The present study demonstrates that negative pressure wound therapy produces a coherent and sustained improvement in wound healing across multiple dimensions. Rather than influencing a single endpoint, NPWT acted on wound surface area, depth, and granulation tissue formation simultaneously. This pattern suggests biological modulation of the wound environment rather than transient mechanical contraction.

 

Progressive reduction in wound surface area, illustrated quantitatively in Graph 1, followed a steady, non-abrupt trajectory. Such gradual contraction is clinically relevant. Rapid early reduction may reflect temporary deformation, whereas sustained reduction implies structural remodeling at the wound margins. Experimental studies have shown that controlled microstrain generated by negative pressure stimulates fibroblast proliferation and extracellular matrix organization, leading to true tissue advancement rather than surface collapse.^[7] The present findings are consistent with this mechanism, particularly in wounds with larger baseline dimensions.

 

Wound volume reduction, depicted in Graph 2, was more pronounced than surface contraction over the same interval. Clinically, this manifested as visible reduction in wound depth and cavity size. Volume reduction is a critical but often underreported parameter, especially in deep or cavitary wounds where delayed closure increases the risk of infection and graft failure. Prior work has attributed this effect to improved interstitial fluid clearance and restoration of microcirculatory perfusion under negative pressure conditions.^[8] The observed reduction in wound volume in this study supports these physiological explanations and highlights the value of NPWT in stabilizing complex wound beds.

 

Granulation tissue formation represented the most prominent response to NPWT. As shown in Graph 3, a substantial proportion of the wound bed demonstrated healthy granulation by day 20. Granulation is not merely an indicator of healing but a prerequisite for successful split-skin grafting. Clinical photographs in Figures 1 and 3 visually corroborate this progression, showing uniform granulation and epithelialization following NPWT across different wound etiologies. Randomized trials in diabetic foot ulcers have similarly reported higher rates of graft-ready wounds with NPWT compared to advanced moist wound care.^[9]

 

When healing parameters were examined collectively, NPWT demonstrated superiority across all outcomes when compared with conventional wet-to-moist dressing benchmarks. Table 2 and Graph 4 together illustrate that improvements were distributed across surface area reduction, volume reduction, and granulation tissue formation, rather than being driven by a single dominant factor. This multidimensional effect distinguishes NPWT from passive dressing strategies, which primarily maintain moisture without actively modifying wound physiology.^[10]

 

The integration of quantitative outcomes with clinical photographs strengthens the interpretation of these findings. Figure 1 demonstrates post-NPWT granulation and split-skin graft outcome in a dorsum foot wound, while Figure 2 illustrates uniform wound bed preparation following NPWT in a below-knee guillotine wound. Figures 4 and 5 further show successful wound stabilization and graft uptake in avulsion and perineal injuries, respectively. Together, Figures 1–5 demonstrate that the benefits of NPWT extend across varied wound types, anatomical locations, and etiologies, supporting its broad applicability in surgical practice.

 

The practical implications of these findings are summarized in Table 3, which links numerical improvements to surgical decision-making. Earlier readiness for split-skin grafting reduced interim dressing duration and facilitated earlier discharge. These downstream effects align with larger clinical series reporting shortened hospital stay and reduced overall treatment costs with NPWT, particularly in complex lower-limb wounds.^[11] The relevance of these observations is heightened in patients with diabetes mellitus. Impaired microcirculation, neuropathy, and altered inflammatory response collectively delay wound healing in this population. Evidence from randomized and systematic reviews indicates that NPWT improves healing rates and reduces the risk of major amputation in diabetic foot ulcers when compared with standard care.^[12] Although the present study included mixed wound etiologies, the consistent response observed in diabetic wounds, as shown in Figures 3 and 4, supports these earlier findings.

 

Importantly, no significant adverse events related to negative pressure therapy were observed. This aligns with existing literature indicating that NPWT is a safe modality when applied after adequate debridement and infection control.^[13] The absence of therapy-related complications reinforces its suitability for routine surgical use rather than selective or rescue application.

 

Overall, the findings of this study support the view that negative pressure wound therapy functions as an active biological intervention rather than a passive dressing technique. The observed improvements were gradual, sustained, and clinically actionable. In surgical practice, such predictability is often more valuable than rapid but unstable closure. NPWT provided both.

Negative pressure wound therapy demonstrated consistent advantages in the management of complex wounds, producing simultaneous reduction in wound size, depth, and faster granulation. These changes translated into earlier readiness for split-skin grafting and shorter inpatient care. When applied after adequate debridement, NPWT functioned as an active biological modulator rather than a passive dressing. Despite study limitations, the findings support its routine use as an effective wound-stabilization strategy in surgical practice.

 

Conflicts of Interest

There is no conflict of interest declared in this study.

1. Armstrong DG, Boulton AJM, Bus SA. Diabetic foot ulcers and their recurrence. N Engl J Med 2017;376(24):2367-75.
2. Guo S, Dipietro LA. Factors affecting wound healing. J Dent Res 2010;89(3):219-29.
3. Jones V, Grey JE, Harding KG. Wound dressings. BMJ 2006;332(7544):777-80.
4. Saxena V, Hwang CW, Huang S, et al. Vacuum-assisted closure: microdeformations of wounds and cell proliferation. Plast Reconstr Surg 2004;114(5):1086-96.
5. Morykwas MJ, Argenta LC, Shelton-Brown EI, et al. Vacuum-assisted closure: a new method for wound control and treatment. Ann Plast Surg 1997;38(6):553-62.
6. Blume PA, Walters J, Payne W, etc al. Comparison of negative pressure wound therapy using vacuum-assisted closure with advanced moist wound therapy in the treatment of diabetic foot ulcers. Diabetes Care 2008;31(4):631-6.
7. Huang C, Leavitt T, Bayer LR, et al. Effect of negative pressure wound therapy on wound healing. Curr Probl Surg 2014;51(7):301-31.
8. Timmers MS, Le Cessie S, Banwell P, et al. The effects of varying degrees of pressure delivered by negative-pressure wound therapy on skin perfusion. Ann Plast Surg 2005;55(6):665-71.
9. Lavery LA, Boulton AJM, Niezgoda JA, et al. A comparison of diabetic foot ulcer outcomes using negative pressure wound therapy versus historical standard of care. Int Wound J 2007;4(2):103-13.
10. Vikatmaa P, Juutilainen V, Kuukasjärvi P, et al. Negative pressure wound therapy: a systematic review on effectiveness and safety. Eur J Vasc Endovasc Surg 2008;36(4):438-48.
11. Willy C, Agarwal A, Andersen CA, et al. Closed incision negative pressure therapy: international multidisciplinary consensus recommendations. Int Wound J 2017;14(2):385-98.
12. Dumville JC, Hinchliffe RJ, Cullum N, et al. Negative pressure wound therapy for treating foot wounds in people with diabetes mellitus. Cochrane Database Syst Rev 2013;(10):CD010318.

13.   Orgill DP, Bayer LR. Negative pressure wound therapy: past, present and future. Int Wound J 2013;10(Suppl 1):15-9.