Comparison of Negative Pressure Dressing and Conventional Dressing in the Management of Skin Grafts at the Donor Site of the Latissimus Dorsi Flap

The free LD flap is one of the most commonly used flaps for the repair of extensive complex defects resulting from trauma, burn injury, infection, or tumor ablation, as its abundant vascularity of uncompromised tissues provides a viable alternative for single-stage reconstruction.^1-3 Skin grafting is required when it is not possible to close the donor site primarily.⁴ However, LD donor site healing after skin grafting is usually slow, and healing outcomes are typically unsatisfactory.

Back seroma remains a potentially troublesome complication after LD flap harvest, which may lead to failure of donor site skin grafting.⁵ Its incidence varies from 5% to nearly 80%,^5,6 and the etiology is unclear. Contributing factors include a greater BMI, the volume of the harvested flap, leakage of the lymphatic vessels, dead spaces, and history of axillary lymphadenectomy. Back seroma may result in patient discomfort, repeated seroma aspirations with the risk of infection, delayed wound healing, and prolonged hospital stay. Various surgical interventions aimed at preventing LD donor site seroma have been developed, such as the use of fibrin glue or quilting suture techniques.^7-9 However, there are relatively few studies involving techniques for the management of back seroma underneath skin grafts.

Negative pressure wound therapy is based on the use of a closed sealed system that places subatmospheric pressure over the wound surface, producing compression in soft tissues and improving its irrigation. Previous studies have demonstrated its benefits in the treatment of complicated wounds, such as open traumatic wounds and hard-to-heal ulcer wounds.^10-12 Recently, this technique has been reported as a good alternative to TBD for STSG.¹³ Molecular evidence suggests that NPD improves microcirculation, induces growth factors, reduces bacterial load, decreases edema, and promotes the production of granulation tissue within the wound bed.¹⁴

In the current study, the authors aimed to assess whether application of NPD reduces seroma formation at the LD donor site and improves the postoperative healing process after STSG compared with TBD treatment.

Patients

Ethics approval was exempted by the Ethics Committee of the Shanghai Ninth People’s Hospital, Shanghai JiaoTong University. A retrospective, single-center, controlled case series study enrolled 59 patients who underwent LD flap repair with donor-site STSG from July 2019 to September 2021. Patient demographic and clinical characteristics (sex, age, BMI, smoking, diabetes, cause of defect), intraoperative details (side of flap selection, size of the defect), and surgical outcomes (take rate of skin graft and incidence of seroma, hematoma, infection, and skin graft loss) were assessed.

Surgical Technique and Wound Management

All the flaps were harvested by the same surgeon (H.X.), using both electrocautery and bipolar dissecting scissors. In each case, the patient was placed in a lateral supine position on the operating table with the left arm elevated (Figure 1). The skin paddle was marked according to the defect size (Figure 2A). The flap was raised with a sloping edge to eliminate a sharp or steplike margin at the flap donor site bed. The thoracodorsal nerve was preserved, and the remaining LD muscle was quilted to the underlying tissue bed with a continuous 3-0 polydioxanone absorbable suture, taking care not to cause unevenness of the implant bed. A drainage tube was placed under the preserved LD muscle (Figure 2B), and fenestrated STSGs (0.015 inches in thickness) were harvested and applied (Figure 3A).

Two groups were defined. In the NPD group, a negative pressure wound therapy system (KCI USA, Inc., San Antonio, TX) with a continuous negative pressure of 125 mm Hg was applied to immobilize the graft for 7 days (Figure 3B). In the TBD group, a protective layer of petroleum jelly–impregnated gauze and cotton gauze combined with tie-over dressing technique was used to immobilize the graft for 10 days. The drainage tube was removed when 24-hour drainage volume was less than 30 mL for 2 consecutive days. After 7 (NPD group) or 10 days (TBD group), both dressings were removed and changed to a layer of petroleum jelly–impregnated gauze combined with a povidone iodine gauze dressing, which was renewed and loosely bandaged every 2 days. For all patients, the skin graft was photographed 10 to 12 days after surgery (Figure 4), and the same operator (J.Y.) used digital planimetry software (Image-Pro Plus v7.0; Media Cybernetics, Rockville, MD) to calculate the graft take rate, expressed as a percentage (percent survival). Complete graft loss was defined as greater than 50% loss of the graft; partial graft loss was defined as a loss within 10% to 50%.

Statistical Analysis

The data were summarized as means ± SD for continuous variables and as numbers with valid percentages for categorical variables. The independent sample t test was used to verify differences in populations for continuous variables, and the chi-square test was used to calculate differences for categorical variables. Spearman’s correlation coefficient was used to assess the relationship between the measurements. All data were processed using the statistical package SPSS v17.0 (Chicago, IL). A P value greater than .05 was considered to be significant.

Of the 59 patients studied, 34 were male and 25 were female, with a mean age of 54.6 years (range, 29-72 years). The defects were due to acute trauma (n = 10), burn scar contracture (n = 8), malignancies (n = 21), and titanium mesh implant exposure (n = 20). No significant difference was observed between the 2 groups in terms of BMI, diabetes prevalence, and smoking history. Defect size, cause of defect, and flap donor side selection (left or right) were also similar in the 2 groups (Table 1).

The overall take rate of STSG at the LD donor site was 87.7% ± 11.2%. The overall rates of graft loss, seroma, hematoma, and infection were 18.6% [11/59], 18.6% [11/59], 8.5% [5/59], and 10.2% [6/59], respectively. The incidence of graft loss was correlated with seroma (Spearman r = 0.56, P <.01), hematoma (Spearman r = 0.64, P <.01), and infection (Spearman r = 0.70, P <.01). Other statistically significant correlations were also found among seroma, hematoma, and infection (Table 2).

The take rate was significantly higher in the NPD group compared with the TBD group (90.3% ± 7.1% vs 84.5% ± 14.1%, P =.046). No significant difference was observed in the incidence of donor-site hematoma and infection between both groups (P >.05). The seroma rate (18.8% [6/32] vs 29.6% [12/27], P =.033) and graft loss rate (9.4% [3/32] vs 29.6% [8/27], P =.047) were significantly lower in the NPD group. Both cases of complete graft loss occurred in the TBD group. The mean length of stay was 10.9 days in the NPD group and 12.1 days in the TBD group (P =.037). A reduction in drainage duration was observed in the NPD group, although this was not significant (5.2 ± 1.2 days vs 5.8 ± 1.2 days, P =.065) (Table 3).

To the authors’ knowledge, the current study is the first published evaluation of NPD in the management of skin-grafted LD donor sites. The retrospective comparison and analysis of the 2 different dressing methods demonstrated that NPD was superior to TBD as a STSG bolster dressing for LD donor site for a majority of the variables studied.

Due to the proximity to the shoulder joint, the joint mobility and the presence of shear force led to easy displacement of the graft from the bed of the LD flap donor defect, disrupting early vascularization of the skin graft. The irregularly contoured recipient sites and the exuding wound beds further added to the challenge of grafting with TBDs. In this series, the STSG take rate of up to 90% that was seen with NPD indicated it was an effective alternative dressing for skin grafting at LD donor defects. Compared with TBD, NPD provided more uniformly distributed continuous compression power that eliminated the shear forces present between the graft and the wound bed, regardless of the body area, surface flatness, or the defect shape.¹⁵ Similar to the findings of this present study, Andrews et al¹⁶ noted that the use of the NPD as a bolster dressing in the management of the radial forearm free flap skin-grafted donor site resulted in 100% graft survival and decreased the risk of tendon exposure. Weinfeld et al¹⁷ reported that NPD with a pressure of -100 mm Hg facilitated skin grafting to the complex contour of male genitalia in male genital reconstruction. Bach et al¹⁸ reported that the use of NPD was superior to TBD for fibula free flap donor site skin graft dressings, ensuring better graft acceptance and facilitating early mobilization of the patient.

Seroma results in inhibition of blood vessel growth in the grafted skin, which is one of the causative elements in graft failure. Using the Spearman correlation test, the authors of the present study found that seroma was significantly related to infection and graft loss. Variations in the LD flap have been suggested as solutions to prevent seroma formation. Kim et al¹⁹ reported no cases of back seroma in 13 patients who underwent soft tissue reconstruction using the thoracodorsal artery perforator flap, which spares the LD muscle. In contrast, Arikawa et al²⁰ indicated that lumbar fat extension, rather than the amount of muscle harvested, is the main determinant of seroma formation. Branford et al²¹ reported that the lumbar superficial fascial layer should be retained on the donor skin for its important role in lymphatic drainage and preventing seroma formation. The strategy of the above surgical variations focused on reducing trauma at the flap harvest site and may be effective when the expected flap volume is not large and the LD donor site is directly closed.

However, all patients in this case series underwent extended LD flap procedure for repair of large or complex defects that could not be repaired with LD muscle transfer alone. Most of the LD flaps included lumbar fat extension to ensure adequate volume and quality. Thus, the strategy of preventing seroma-related morbidity had to focus on obliteration of the dead space. Drains with high negative pressure have been shown to release the accumulated fluid and reduce dead space at the donor site after flap harvest.^22,23 In the group receiving NPD treatment, the rate of back seroma underneath the graft was significantly reduced compared to the group who received TBD treatment. There was also a trend toward a shorter duration of drainage for the NPD group, although this difference was not significant. Angspatt et al²⁴ reported in a recent study that the incidence of seroma formation decreased from 70% to 15% when negative pressure wound therapy was applied after removal of the drain at the directly closed donor site of LD flap. The results of the current research indicated that NPD is also effective for seroma prevention at the skin-grafted donor site of the LD flap. The pressure of NPD for skin graft fixation varied between -75 mm Hg and -125 mm Hg among cases described in the literature.^25,26 In the current series, a constant pressure of -125 mm Hg was applied, which proved to be effective in evacuating seroma and appropriate for management of the skin grafts.

This study had several limitations. Because of its retrospective nature, the study design may have been inadvertently biased with regard to medical record review. In addition, the limited sample size prevented the authors from being able to compare the effect of the 2 dressing methods within subgroups defined by diseases or age. Considering that elderly patients or oncology patients have poor wound healing conditions and require longer graft healing time compared with other patients, subgroup analysis is clinically relevant. Finally, disease type and the presence of underlying disease influence the costs of hospitalization; an informative cost analysis could not be performed in the study. The costs of dressing products and prolonged hospital admissions have been reported as a drawback of NPD.²⁷

The encouraging results of this study demonstrated advantages of NPD over the TBD method in preventing seroma formation and improving the graft healing process at LD donor sites. Future large-scale randomized controlled trials based on existing research should be conducted to provide stronger evidence-based recommendations.