Time to Surgical Closure of Complex Infectious Wounds: A Single-center Retrospective Cohort Study

A simple, effective algorithm guides clinicians when determining the optimal means of wound closure.¹ This algorithm, traditionally known as the reconstructive ladder, provides a framework for reconstruction that attempts coverage with the simplest, least morbid technique possible to optimize the delicate balance between risks and benefits.² Overall, the objective is to achieve timely and adequate wound closure.

Traumatic soft tissue injury and NSTIs are a significant health care burden. Necrotizing soft tissue infections encompass infections of the soft tissue compartment, including dermis, subcutaneous tissue, superficial fascia, deep fascia, and muscle. Management of NSTIs requires fluid resuscitation, antibiotics, and complete surgical debridement.³ In particular, early surgical debridement is a significant determinant of morbidity, mortality, and clinical outcomes.^4,5 Surgical management of necrotizing infections and traumatic injuries can result in complex wounds for which primary wound closure is often impossible. Patients can require multiple surgical procedures for further debridement and eventual closure; an average of between 2 and 7 procedures have been reported in the literature to achieve adequate infection control.^4,6,7 Additionally, patients often have associated injuries or hemodynamic instability, and therefore require a longer hospital LOS and considerable resources (financial, operational, and human).

Both patient and wound factors influence healing and selection of wound closure technique, especially when surgical intervention is considered. Such factors include patient comorbidities such as diabetes, peripheral vascular disease, age, body mass index, immunosuppression status, and alcohol use.^8,9 Local factors to consider include bacterial burden, maceration, necrosis, trauma, pressure, and edema.¹⁰

The primary objective of this study is to describe the sociodemographic factors of and time to closure for patients who required surgical wound closure owing to an NSTI. The secondary objective is to identify possible predictors of time to closure.

Design and setting

This retrospective cohort study was conducted in a single tertiary care center, following approval by the Research Ethics Board. Data reviewed consisted of patient demographics (age, sex, smoking status, comorbidities), wound characteristics (location, size, etiology), and surgical reconstructive procedures (number, LOS, complications).

Data sources

Data were retrieved from patients’ medical charts, including surgical procedure reports, discharge summaries, and follow-up notes. For patients who were referred to the tertiary care center following initial treatment at another hospital, admission and discharge records were reviewed to accurately extract data.

Study population

The study population consisted of patients aged 18 years or older with a complex wound or wounds requiring surgical intervention to achieve definitive closure. The wound etiology of interest was NSTI. Patients undergoing surgical reconstruction for burn-related wounds or wounds related to oncologic or traumatic causes were excluded. Patients who died before wound closure was achieved, or for whom incomplete or minimal information had been documented, were also excluded.

Outcomes

The primary outcome was time to surgical closure of the complex wound. This timing was defined by the time between the first surgical debridement or exploration of the wound and the final surgical procedure to achieve wound closure.

Statistical analysis

Descriptive statistics were calculated for all variables. Time-to-closure curves were calculated using the Kaplan-Meier method, and differences were formally tested using log-rank tests. An adjusted multivariable Cox-proportional hazards regression model was used to assess the independent relationship between patient and wound characteristics and time to closure. Age and sex were selected a priori for inclusion in a multivariable model; variables deemed to be significant based on unadjusted analyses and those determined using forward stepwise regression and backward stepwise regression were added as well. All tests were 2-sided, and an alpha level of less than .05 was considered significant.

Patient characteristics

The medical records of 106 patients treated at the authors’ institution between 2007 and 2017 were reviewed, and 47 patients met the inclusion criteria. Descriptive statistics of patients’ medical comorbidities, medications, and substance use were analyzed (Table 1). Most patients were middle aged (mean age, 50.3 years; range, 20-81 years). The cohort of patients was nearly equally divided by sex (49% male, 51% female). Review of medical comorbidities demonstrated that 50% of patients were healthy and not using any medications. Twelve patients (25%) had type 1 or 2 diabetes, 16 (34%) had hypertension, and 10 (21%) had a history of prior cardiac events. Three patients (6%) were taking aspirin, and 5 (11%) were receiving therapeutic anticoagulation (warfarin or heparin). Six patients (13%) had an alcohol use disorder, and 12 patients (25%) used recreational substances. Only 2 patients (4%) were current smokers at the time of admission, and 8 (17%) were former smokers.

Surgical characteristics

Of 47 patients, the percent TBSA of wounds was described in only 19 cases (40%). Of these, the median percent TBSA was 16%. Average LOS was 30.0 days ± 20.2 SD, and average time to closure from the first debridement to the last surgical closure was 31.2 days ± 20.1 SD, requiring an average of 4.8 procedures ± 3.0. The majority of patients (n = 30 [64%]) underwent between 1 and 5 surgical procedures during their stay. For those patients with a LOS longer than 30 days, the average number of surgical procedures was 9.9. Wound-related complications were present in 14 patients (30%), and 14 patients (30%) experienced a deep vein thrombosis during their stay.
 

Wound characteristics

There were 24 patients (51%) in which NSTI primarily caused the wound. In the remaining 23 patients (49%), NSTI either was caused by trauma, purpura fulminans, or necrotizing vasculitis, or it occurred after a surgical procedure. Wounds were located on the head and neck in 1 patient (2%); the thorax, back, and abdomen in 6 patients (13%); the upper extremity in 4 patients (8%); the lower extremity in 23 patients (49%); and the groin in 8 patients (17%). In 5 patients (11%), wounds were located on multiple areas of the body. Final closure was achieved with autograft in 33 patients (70%), with pedicled local flap in 4 patients (9%), and with both techniques in 10 patients (21%) (Table 2).

Association with time to closure

Associations between predictor variables and time to closure were determined (Table 3). There was no significant association between time to closure and medical comorbidities, substance use, or medication use. Local flap closure (P =.016) and increased number of surgical procedures (P =.0007) were associated with increased time to closure. A multiple regression model was used to determine the association between significant predictor variables and time to closure (Table 4). Local flap closure (P =.02) and increased number of surgical procedures (P =.003) were found to be associated with increased time to closure based on multivariable regression analysis.

Although wound and surgical factors influencing mortality and LOS associated with NSTIs have been well described, few data have been reported on factors that influence time to closure of such complex infectious wounds. This study better determined the characteristics of such a patient population that is otherwise mostly healthy. Moreover, the use of a flap for closure and an increased number of surgical procedures—the latter of which is indicative of numerous debridements—were identified as important predictors of increased time to wound closure.

In this cohort of 47 patients, the average time to closure was 31.2 days, requiring an average of 4.8 procedures, with the majority of wounds achieving closure with 1 to 5 procedures. Prior studies have reported the need for a mean of 2 to 7 procedures to achieve closure of infectious wounds.^4,6,7 The rates in this study are similar to those reported by Faucher et al,⁸ who found that patients treated at their tertiary care burn center for NSTI underwent a mean of 4.1 procedures and required a mean LOS of 28.5 days. These high numbers emphasize the complex clinical course of patients admitted for NSTIs and the significant health care burden of such infections.⁹ In the present study, patients whose LOS was greater than 30 days underwent an average of 9.9 surgical procedures. This suggests that for patients who are admitted for longer than 1 month, the number of procedures and associated morbidities as well as the ultimate health care burden are much higher than for patients with a shorter LOS. Conversely, this also suggests that increased numbers of procedures may require patients to remain in the hospital for progressively longer periods of time. In the United States, the mean cost of care for patients admitted for NSTIs ranges in the thousands of dollars per day, with average total costs of approximately $50 000 to $100 000 per case, which highlights the high financial burden on the health care system.^10-12

In this study, most patients who required surgical management of their wounds following NSTI were immunocompetent and nondiabetic upon admission. There was no association between substance use (alcohol, smoking, or other), anticoagulant medication use, or medical comorbidities and time to closure. Although factors associated with mortality resulting from NSTI have been studied, there is limited evidence about time to closure. Previous studies reported that immunosuppression, patient comorbidities, and increased age are associated with increased mortality resulting from NSTI.^12,13 Mulla et al¹¹ found that patients aged 44 years or older had an increased LOS resulting from NSTI. Data from the current study suggest that comorbidities and medication use may have little influence on ultimate time to closure of NSTIs in patients who survive NSTI infections or trauma and who subsequently present with wounds that require closure. In a study published in 2004, Tillou et al¹⁴ found no independent risk factors of mortality or intensive care unit admission in patients with NSTIs. Other studies suggest the primary determinants of mortality outcomes may be early diagnosis and surgical management, regardless of patient demographics.^11,15-17

Analysis of wound-related factors in the current study showed that primary NSTI was the most common etiology of such complex infectious wounds encountered in the authors’ tertiary care center. In contrast, NSTI that occurred following traumatic injury, NSTI in association with purpura fulminans or necrotizing vasculitis, or NSTI occurring postoperatively represented a minority of cases. Most wounds were located on the lower extremities. Closure was achieved mainly with autograft (70%), with a few cases requiring either local flap (9%) or both autograft and local flap (21%). On both analyses, local flap closure was associated with increased time to closure (P =.02 for both analysis types). This may suggest that more complex wounds (ie, those that require more time and more procedures to achieve closure) may ultimately also require the use of local flaps to achieve definitive closure. It is also possible that surgeons are hesitant to use flaps because of concern for persistent infection, using them only when absolutely necessary and when more time has passed. Moreover, a large postinfectious wound with healthy granulation tissue is more likely to be treated with skin grafting than with a more complex reconstructive procedure, such as a flap, and may thus result in timelier wound closure. A thorough chart review showed that percent TBSA was described in only 19 cases (40%), with a median percent TBSA of 16%. Although NSTIs may require as many resources as burns, if not more,¹⁸ it is interesting to note that such record keeping suggests that NSTI may not be viewed similarly to burns by physicians on the burn unit.

In this study, increased numbers of surgical procedures (representing wounds requiring increased numbers of debridements) and use of more reconstruction procedures (grafts and flaps) were associated with increased time to closure, independent of percent TBSA or wound location. In patients for whom time to closure was longer than 30 days, a mean of 9.9 procedures were necessary to achieve definitive closure. This suggests that not only do patients with a longer time to closure require multiple surgical procedures, resulting in a significant health care burden, but also that independent of the wound size (percent TBSA) and location, when greater numbers of procedures (debridements, grafts, and reconstruction) are used for closure, the time to closure will be longer. Further, this may suggest that surgical planning should take into account not only severity and extent of NSTI, but also achieving definitive wound closure more quickly using the fewest surgical procedures possible.

This study is limited by its focus on time to closure of NSTIs at a single tertiary burn center. Future studies investigating NSTI closure would benefit from inclusion of additional academic centers to achieve a larger sample size and to compare rates between the centers. Further work could be done to investigate factors associated with surgical management, such as time to diagnosis and time to surgical intervention, to determine the influence of such factors on time-to-closure outcomes. However, it may be challenging to conduct this at tertiary referral centers, because patients may often be referred after already undergoing several debridement procedures.

Necrotizing soft tissue infections are a considerable health care burden, and they can result in complex wounds for which closure is often difficult or complicated to achieve. The goal of this study was to determine patient, wound, and surgical factors associated with time to closure of complex wounds resulting from NSTIs. Patients who presented to a single tertiary care center between 2007 and 2017 with an NSTI requiring surgical closure were included in the study. The data suggest that factors including use of local flaps to achieve closure and increased numbers of surgical procedures (particularly debridement) may be associated with increased time to closure of complex wounds resulting from NSTIs.