Traction-assisted Internal Negative Pressure Wound Therapy With Bridging Retention Sutures to Facilitate Staged Closure of High-risk Wounds Under Tension

Background/Objective. Loss of domain often complicates attempts at delayed wound closure in regions of high tension. Wound temporization with traction-assisted internal negative pressure wound therapy (NPWT), using bridging retention sutures, can minimize the effects of edema and elastic recoil that contribute to progressive tissue retraction over time. The investigators evaluated the safety and efficacy of this technique for complex wound closure. Materials and Methods. Between May 2015 and November 2015, 18 consecutive patients underwent staged reconstruction of complex and/or contaminated soft tissue defects utilizing either conventional NPWT or modified NPWT with instillation and continuous dermatotraction via bridging retention sutures. Instillation of antimicrobial solution was reserved for wounds containing infected/exposed hardware or prosthetic devices. Demographic data, wound characteristics, reconstructive outcomes, and complications were reviewed retrospectively. Results. Eighteen wounds were treated with traction-assisted internal NPWT using the conventional (n = 11) or modified instillation (n = 7) technique. Defects involved the lower extremity (n = 14), trunk (n = 3), and proximal upper extremity (n = 1), with positive cultures identified in 12 wounds (67%). Therapy continued for 3 to 8 days (mean, 4.3 days), resulting in an average wound surface area reduction of 78% (149 cm² vs. 33 cm²) at definitive closure. Seventeen wounds (94%) were closed directly, whereas the remaining defect required coverage with a local muscle flap and skin graft. At final follow-up (mean, 12 months), 89% of wounds remained closed. In 2 patients with delayed, recurrent periprosthetic infection (mean, 7.5 weeks), serial debridement/hardware removal mandated free tissue transfer for composite defect reconstruction. Conclusion. Traction-assisted internal NPWT provides a safe and effective alternative to reduce wound burden and facilitate definitive closure in cases where delayed reconstruction of high-tension wounds is planned.

Loss of domain is a common problem associated with large open wounds in areas of increased tension. At issue are 3 contributing factors: progressive marginal retraction by elastic recoil and/or loss of fascial retention, surrounding tissue edema, and soft tissue deficit from operative resection.¹ This situation is frequently encountered during closure of prior fasciotomies or delayed reconstruction of traumatic/contaminated abdominal wall defects.^2-4 Pending negative cultures and final tissue pathology also influence the timing of definitive closure in patients undergoing staged replacement of infected total joints and oncologic reconstruction, respectively.^5-8 Wounds that remain open without regard for the forces acting on them will continue to widen, indurate, and scar.⁹ Over time, direct primary closure becomes difficult, if not impossible, and is often plagued by high rates of dehiscence and early complications.^1-4,9

When used as an adjunct in wound reconstruction, negative pressure wound therapy (NPWT) potentiates healing through increased local blood flow and granulation, reduced tissue edema, and controlled bacterial proliferation.^10,11 Modifications of this technology (including incisional internal vacuum-assisted therapy, which utilizes a partially buried sponge and closed suction drainage through a small skin opening) have been shown to expedite cavity collapse and facilitate delayed primary closure of large and/or contaminated wounds.^12,13 While effective, this technique has been described mainly for defects in which near-complete primary closure is possible. For wounds that are not amenable to direct approximation, combined reconstructive modalities are typically required to achieve definitive coverage.

In these situations, incorporation of continuous dermatotraction can expedite wound reapposition by capitalizing on the viscoelastic properties of skin to induce mechanical creep.^2,9,14-17 As skin is stretched, straightening and elongation of collagen fibers along the vector of force occur within minutes.¹⁸ This effect is amplified through adequate tissue undermining, which untethers the dermal elastin fibers within skin, allowing them to stretch beyond the limits of their inherent extensibility.¹⁶ Maintenance of tension over time reduces the natural retractive forces of skin (ie, stress-relaxation) and serves as a mechanical stimulus for tissue regeneration (ie, biologic creep). The expanded surface area achieved by this process increases the overall availability of the skin and soft tissue envelope to provide coverage.^19-21

Although simultaneous application of NPWT and continuous dermatotraction has been described previously, significant heterogeneity among reported techniques and lack of quantitative outcome data have limited recommendations regarding the efficacy of this approach for complex wound closure.^{9,16,17,22,23} The purpose of this retrospective study is to evaluate the utility of traction-assisted internal NPWT and use of bridging retention sutures as an adjunct to reduce wound burden and achieve delayed primary closure in a variety of high-tension wounds.

Between May 2015 and November 2015, 18 consecutive patients underwent staged closure of complex and/or contaminated soft tissue defects utilizing a modified internal vacuum-assisted closure technique, which combines NPWT and continuous dermatotraction with bridging retention sutures. Wounds were serially debrided and closed in a delayed primary fashion when possible. Patients with defects that were amenable to tension-free closure during initial debridement as well as those undergoing single-stage debridement and reconstruction with skin grafts, regional flaps, and/or free tissue transfer were excluded. Demographic data, defect type and location, and length of follow-up were documented for all patients. Reconstructive characteristics and outcome measures of interest included timing and method of definitive wound closure, number of surgical interventions, percentage reduction in wound surface area (WSA), and device-related complications. This study was approved by the MedStar Georgetown University Hospital Institutional Review Board.

Conventional technique
Following adequate debridement, wound bed preparation proceeds with tangential excision of senescent wound margins, subcutaneous debulking, and judicial resection of indurated soft tissues. Wound edges that are not easily approximated are undermined to permit adjacent tissue recruitment and midline centralization. Bridging 2-0 polypropylene vertical mattress retention sutures are placed 1 cm to 2 cm from the wound edge and about 3 cm apart along the length of the wound to support adequate tension while minimizing the risk of suture pull-through and ischemic injury during closure. Untied suture ends are secured with hemostat clamps in series and retracted to allow placement of an open cell sponge into the wound cavity (Figure 1A). Tension is subsequently applied to the overlying suture bridge, bringing the wound edges into approximation over the partially buried foam. Adequate tension is determined by the initial loss and subsequent return of marginal capillary refill within minutes. Traction on each suture is adjusted as needed to ensure sufficient marginal perfusion is maintained. Then, the sutures are tied sequentially, beginning at the periphery, with care taken to avoid skin tearing and/or sustained blanching from increased tension as closure progresses centrally (Figure 1B). Clear plastic adhesive provides a water-tight seal, leaving only a small opening for the drainage tubing to connect (Figure 1C). With the device in place, NPWT (V.A.C. Ulta Therapy System; KCI, San Antonio, TX) is maintained at -125 mm Hg continuous suction for 3 to 5 days and may be repeated to further reduce wound burden and/or facilitate definitive closure (Figure 1D). 

Modified technique for infected and/or exposed hardware
In the setting of infected and/or exposed hardware, the aforementioned technique is modified to incorporate NPWT with instillation (NPWTi; V.A.C. Ulta Therapy System with VeraFlo Instillation; KCI, San Antonio, TX). The open cell sponge and sutures are applied as previously described and connected to an instillation-capable device. This technology combines NPWT (-125 mm Hg) with automated intermittent instillation of a polyhexanide-containing antimicrobial solution and is set to irrigate at 2-hour intervals with a 20-minute dwell time. To prevent ongoing maceration of wound margins by the instillate, the wound edges are lined with 2-cm wide strips of protective plastic adhesive prior to placing the foam and bridging retention sutures. Again, therapy is continued for 3 to 5 days and may be repeated as necessary.

Eighteen patients underwent combined internal NPWT with bridging retention sutures using either the conventional (n = 11) or modified instillation (n = 7) technique. Defects in this series were highly variable and encompassed a broad range of anatomic locations, including the thigh (n = 3), knee (n = 4), leg (n = 2), ankle (n = 2), foot (n = 3), spine (n = 2), abdomen (n = 1), and proximal upper extremity (n = 1). Active infection was documented via positive cultures in 12 wounds (67%), which includes 4 of the 7 with exposed hardware or bypass grafts. Five defects (28%) involved open communication with a joint space, resulting in exposure of either a permanent prosthesis (n = 3) or antibiotic spacer (n = 2). On average, patients underwent 2.2 operative debridements, with a mean time to definitive coverage of 4.3 days (r = 3–8 days).  A second cycle of interval NPWT was required to prevent loss of domain in 3 patients who persistently had positive cultures after initial debridement. Seventeen wounds (94%) were closed in a delayed primary fashion. The remaining patient required a medial gastrocnemius flap and split-thickness skin graft for coverage of a composite total knee defect with exposed antibiotic spacer. Mean WSA at the time of presentation and definitive wound closure was 149 cm² (r = 20 cm²–576 cm²) and 33 cm² (r = 4 cm²–108 cm²), respectively, indicating an average reduction of 78% over the treatment period.

Overall, 16 of 18 (89%) wounds remained closed over an average follow-up period of 12 months (r = 10–14 months). Two patients with an infected ankle arthrodesis presented with recurrent infection and skin necrosis within 8 weeks of definitive closure, ultimately mandating repeat serial debridement, hardware removal in 1 patient, and definitive reconstruction with free tissue transfer. Complications in this series were otherwise minimal and consisted of minor incisional dehiscence in 2 patients, which was successfully managed with local wound care. No cases of blistering, wound-edge maceration, or marginal skin necrosis related to the use of the NPWT device and/or bridging retention sutures were observed. A summary of patient demographics, wound characteristics, reconstructive outcomes, and complications are provided in the eTable. 

Case 1
A 58-year-old woman with end stage renal disease presented with an infected left upper extremity arteriovenous fistula and overlying soft tissue necrosis. She underwent wide excisional debridement and ligation of the fistula site, resulting in an 8-cm x 6-cm soft tissue deficit, which was left open and managed with wet-to-dry dressings. Cultures from the initial debridement were consistent with polymicrobial infection. The patient was taken back to the operating room 3 days later with the plastic surgery service for assistance with debridement and subsequent wound closure. At the time of secondary debridement, the wound dimensions had increased to 9 cm x 9 cm. Excision of devitalized/indurated soft tissue was performed along with subcutaneous debulking and wide adjacent undermining. The residual defect was managed with NPWT, and bridging retention sutures were placed at 3-cm intervals. Maximal tension was determined by the presence of early skin blanching and return of capillary refill. Therapy was maintained at -125 mm Hg for 4 days, leading to a reduction in wound surface area by 85% (81 cm² vs. 12 cm²). Definitive wound closure was achieved in a delayed primary fashion without complication, and the wound remained closed at final 6-month follow-up (Figure 2). 

Case 2
A 63-year-old man with an infected left total knee arthroplasty presented 4 weeks after antibiotic spacer exchange and delayed primary closure with subtotal wound dehiscence and peri-incisional necrosis. Fluid aspirated from the joint space was sterile. The patient was taken to the operating room for aggressive surgical debridement. Partial dehiscence of the capsule was noted intraoperatively and was subsequently opened, debrided, and reclosed after exchange of the antibiotic spacer. The residual soft tissue defect (15 cm x 8 cm) was managed utilizing NPWTi and bridging retention sutures. Therapy continued for 4 days, resulting in a WSA reduction of 75% (120 cm² vs. 30 cm²). Cultures from initial debridement remained negative, and tension-free closure of the wound was ultimately accomplished in a delayed primary fashion. The patient’s postoperative course was complicated by a minor (1 cm) superficial dehiscence along the inferior aspect of the incision, which was managed successfully with local wound care alone. Replacement of the permanent prosthesis was performed after 6 months (Figure 3). 

Delayed primary closure of large, composite, and/or contaminated defects is often complicated by a generalized loss of domain in areas of increased tension. As skin edges retract, relaxation of collagen/elastin fibers increases the force required to achieve direct approximation.²⁴ Wound temporization with NPWT serves to mitigate this phenomenon by minimizing the effects of edema and elastic recoil that promote induration and progressive tissue retraction.^9,25,26 When used in isolation, however, secondary healing proceeds externally through wound cavity collapse and granular tissue ingrowth. This process occurs over several weeks and is often limited by extensive scarring, inferior cosmesis, and the need for autologous resurfacing.^17,26-29 By exploiting the viscoelastic properties of skin, bridging retention sutures can augment the effects of NPWT by expanding the soft tissue envelope and expediting delayed approximation of high-tension wounds.

Although data on this approach are limited, variations on the concept of traction-assisted NPWT have been successfully applied in the management of complex abdominal wall and limb fasciotomy defects.^3,4,9,22,23 A recent systematic review and meta-analysis³ evaluating temporary closure techniques for nontraumatic open abdominal wounds reported the highest rates of delayed fascial closure among patients treated with combined NPWT and continuous fascial traction. Lee et al⁹ described the use of extended NPWT-assisted dermatotraction for the management of chronic, retracted fasciotomy wounds in 8 patients with necrotizing fasciitis. In their description, NPWT was widely applied over pretensioned dynamic vessel loops to facilitate internal traction on opposing wound margins. Therapy was continued in 2- to 3-day intervals for an average of 16 days, resulting in a mean reduction in wound burden of 95% and delayed primary closure in 5 of 8 patients. No cases of skin flap necrosis were reported; however, loss of domain resulting from delayed consultation and/or onset of dermatotraction after prolonged wound preparation (mean, 32.4 days postfasciotomy) likely contributed to the more protracted reconstructive period observed in their series.⁹

The technique described herein differs in that internal NPWT is employed in order to facilitate active mechanical debridement during the period of wound closure. The benefits of NPWT in both acute and chronic wound management are well documented and include a reduced bacterial burden, improved marginal perfusion, granular tissue ingrowth, and removal of excess interstitial fluid.^10,11 Wide application of the adhesive surgical drape and adequate undermining facilitates continuous internal traction on the underlying soft tissues, which further reduces edema and propagates ongoing creep as stress-relaxation ensues.⁹ The addition of bridging retention sutures guides dermal approximation while minimizing the volume of sponge required to fill the 3-dimensional cavity.^9,30 In the investigators’ experience, traction is best achieved with high-caliber, inelastic, monofilament suture, given its durability and capacity to withstand high-tension loads in the setting of wide and/or stiff wound margins. The synergistic effects of NPWT and continuous dermatotraction permit wound decontamination, reduction of dead space, and marginal apposition to occur simultaneously, which serves to expedite closure of large and/or contaminated defects without the morbidity and added costs associated with more advanced reconstructive modalities.¹⁷

The results with this approach have been encouraging. Early application of traction-assisted internal NPWT contributed to a satisfactory reduction in WSA by an average of 78% over the mean treatment period (4.3 days). This permitted successful delayed primary closure in 94% of patients presenting with large (mean WSA, 149 cm²), often contaminated (67%), soft tissue loss. For the patient who required a local flap/skin graft to achieve definitive closure of a composite knee defect (case 1), expansion of local tissue reduced WSA by 55%, thereby minimizing the burden of coverage and subsequent morbidity to the skin graft donor site. While the timing of closure is influenced by multiple patient/wound-related factors (ie, comorbidities, infection, perfusion status, etc), the investigators believe timely application of therapy in each case was key to achieving early wound closure in the majority of the studied patients. Interval use of traction-assisted internal NPWT maintains wound dimensions at their minimum by preventing marginal tissue retraction/stiffening between debridements. In this series, 15 wounds (83%) were closed after only 1 treatment cycle. This is in contrast to the delayed time to closure reported by Lee et al,⁹ which highlights the inherent challenges associated with reversing loss of domain and the importance of preventing its establishment early on.

Furthermore, wounds in this series varied significantly with respect to location and etiology, which supports the versatility of this combined approach for complex wound management. The addition of instillation therapy represents an important evolution in the treatment of acute/chronically infected wounds as well as defects with exposed bone, joint space, and/or orthopedic hardware.³¹ In a retrospective, historical, cohort-controlled trial examining the impact of NPWT with (n = 68) and without (n = 74) instillation in the treatment of infected wounds, NPWTi was shown to reduce the total number of operative procedures, expedite the time to wound closure, and shorten the length of hospital stay when compared with NPWT alone.³² Qualitative improvements in both gram-positive and gram-negative cultures also have been observed with NPWTi.^32-36 In the present study, 7 patients (39%) underwent modified traction-assisted internal NPWTi for wound temporization in the setting of infected/exposed hardware (n = 6) and/or prosthetic bypass grafts (n = 1). Six were closed primarily; however, 2 patients with infected ankle hardware ultimately required free flap reconstruction as a result of delayed, recurrent infection. This observation emphasizes the importance of tailoring the reconstructive plan for each patient. The simplest option is not always synonymous with the most appropriate, particularly in the distal-third of the leg, where thin overlying skin flaps provide unreliable coverage of exposed vital structures.

One theoretical concern with bridging retention sutures is the potential for skin flap necrosis during high-tension wound approximation. In this setting, skin necrosis usually results from concentrated force at the point of traction, which can compromise marginal blood flow. The addition of NPWT enhances local perfusion to the surrounding skin and offloads tension on each individual suture by sheering the skin flaps centrally toward the axis of contraction.^9,37 In doing so, traction-assisted internal NPWT safely and effectively approximates wound margins by redistributing traction forces laterally along the length of the wound. It is important to re-emphasize that the amount of tension applied to each suture is determined by the initial blanching of adjacent skin followed by return of capillary refill within minutes. Sustained blanching (beyond 10 minutes) indicates ongoing tissue strangulation and should prompt an incremental release of traction to the point where capillary refill returns. No cases of marginal tissue necrosis were observed with this technique. Furthermore, the investigators did not encounter any issues related to blistering and/or maceration of the wound margins, which are commonly reported (14% and 21%, respectively) with the use of continuous external tissue expansion devices (ie, DermaClose RC;  Wound Care Technologies, Inc, Chanhassen, MN).¹⁷

This study was limited by its retrospective design and heterogeneous population of patients who presented with wounds of various etiologies, dimensions, and anatomic locations. The relative lack of available data and absence of a control group limited the role of statistical analysis as well as the investigators’ ability to generate meaningful comparisons regarding the efficacy of traction-assisted internal NPWT using bridging retention sutures to other similar techniques for delayed primary closure. Nevertheless, data gleaned from this series demonstrate the safety and utility associated with early application of this combined approach in preventing loss of domain, reducing wound burden, and facilitating direct approximation of high-tension wounds. In addition to the benefits described, the authors speculate that traction-assisted internal NPWT contributes to a reduction in the cost of treating large soft tissue defects by expediting wound closure and minimizing the burden of care (ie, dressing changes), operative time, and duration of hospitalization and/or recovery associated with more complex reconstructive procedures. However, reliable cost-effectiveness data are needed to further quantify this potential advantage.

To the best of the authors’ knowledge, this is the first study to provide quantitative outcome data supporting the safety and efficacy of traction-assisted internal NPWT with bridging retention sutures in the management of composite and/or contaminated wounds under tension. The preliminary results indicate that high rates of delayed primary closure can be achieved with minimal complications when this combined modality is applied early in the course of reconstruction. For defects in which marginal apposition is neither feasible nor ideal, maintenance of domain and expansion of the soft tissue envelope will significantly reduce wound burden and minimize the morbidity associated with secondary reconstructive efforts. Therefore, the authors recommend the use of traction-assisted internal NPWT as an adjunct for wound temporization and/or definitive closure in cases where delayed reconstruction of high-tension wounds is planned. Further data are needed to ascertain the most appropriate indications, comparative efficacy, and cost effectiveness of this technique as an alternate solution for complex wound closure.

Affiliation: Center for Wound Healing, Department of Plastic Surgery, MedStar Georgetown University Hospital, Washington, DC

Correspondence:
Michael V. DeFazio, MD 
Department of Plastic Surgery
MedStar Georgetown University Hospital
3800 Reservoir Road NW, 1-PHC Washington, DC 20007
Michael.V.DeFazio@gunet.georgetown.edu

Disclosure: Dr. Attinger is a consultant for KCI, an Acelity company (San Antonio, TX) and Integra LifeSciences (Plainsboro, NJ).