DFUs are a major cause of hospitalization among individuals with diabetes. Recently, 5-year survival rates associated with DFUs have increased, and amputation rates have decreased due to improvements in diabetes treatment and the development of effective treatment guidelines [14-17]. Additionally, increased knowledge about the pathophysiology of DFU formation has facilitated the development of various medical and surgical options to promote wound healing [18, 19]. Among the various emergent treatment options, the roles of NPWT cover the period from the management of the preoperative open wound to that of the postoperative flap site.
NPWT is a non-invasive intervention that promotes wound healing by removing the fluid from the wound through a sealed sponge connected to a collection canister using a vacuum device with controlled negative pressure. Argenta and Morykwas introduced the technique, and NPWT achieves its outcomes via the following elements: wound transudate removal, infection prevention, blood flow optimization, and edema minimization [20-24]. Additionally, with NPWT for open wounds, mechanical deformation plays a key role in tissue expansion . Hence, NPWT has been implemented for a wide range of specific clinical indications, including promoting wound healing and minimizing complications at incision sites [26, 27]. Particularly in the contexts of unstable or high-tension wounds, the negative pressure generated by vacuum devices enhances tissue perfusion and removes fluid and infectious components from wounds [28, 29].
Flap operations are among the most important reconstructive surgical procedures, especially for wounds involving exposed bone. Successful NPWT implementation after flap coverage is becoming progressively widespread for both traumatic and incisional wounds, and the technique has emerged as an efficient alternative to traditional flap salvage techniques, such as leech therapy and heparin injection [8-11]. NPWT has proven its efficacy for removing excess interstitial fluid from beneath flaps and for facilitating the resolution of venous congestion to promote flap viability [10, 11, 30]. The efficacy of NPWT for minimizing complication rates and improving salvage rates associated with pedicled flaps and free muscle flaps has been demonstrated, including in comparative terms relative to traditional flap management [11, 31-33]. However, no publications have reported on NPWT implementation immediately after flap reconstruction for amphibolic DFU patients.
Bi et al. introduced a modified NPWT technique, involving standard placement of the VAC sponge with a pressure of −125 mmHg, for a skin-containing free flap. This technique enabled serial flap examination by creating a small window in the distal end of the flap. However, the authors were not able to visually monitor the entire flap; therefore, they could not address the issue of NPWT safety for free flaps. Lin et al. compared NPWT (immediately after head and neck reconstruction using free flaps) with conventional wound care and found NPWT to be associated with lower complication and infection rates (9.7% vs. 37% and 0.0% vs. 14.8%, respectively). However, because of full coverage of the flap by the VAC sponge, visual and Doppler monitoring were not possible. Chen et al. immediately applied NPWT following lower extremity flap reconstruction; however, their study did not confirm the safety of direct NPWT application on flap pedicles and also the free flaps were not included.
The novel NPWT technique used in this study was developed to monitor entire flaps and address safety concerns. Flap color changes, capillary refilling status, and flap warmth can be assessed through a transparent film covering most of the flap area. Interstitial fluid removal through the sponge can proceed with no effect on flap perfusion. Moreover, a newly reported benefit is that the uncertainty over pressure-induced flap pedicle disruption (by the VAC sponge) can be eliminated by CT angiography.
A major consideration of postoperative DFU management after flap surgery is sustainable flap monitoring. Postoperative flap management is crucial for minimizing major complications. Flap maintenance relies heavily on early detection of flap problems . To date, none of the various flap monitoring methods, such as near-infrared spectroscopy, implantable Doppler, and laser Doppler flowmetry, are recognized as the diagnostic gold standard.
The first 24 h after free flap procedures are crucial for monitoring, detecting, and (planning for) managing complications [38, 39]. Frequent flap monitoring is regarded as ideal for flap salvage , but the requisite short monitoring intervals and time-consuming steps involved in conventional postoperative flap monitoring are burdensome. Moreover, flaps are susceptible to infection and vascular injury, which can lead to hematoma and seroma formation . Notably, our novel monitoring technique was associated with significantly reduced person-time requirements for postoperative flap monitoring (p < 0.05); it was also associated with a lower infection rate. Even when soft tissue inflammation did not completely resolve, transferred fresh flaps tended to improve the adjacent tissue environment and the C-reactive protein level over time. Changing the NPWT sponge on the fifth postoperative day was associated with a slight increase in monitoring time; however, the person-time requirement associated with NPWT group was still less than that associated with conventional monitoring (p < 0.05).
This study had a few limitations. First, the exact pressure map associated with NPWT was not delineated. However, the NPWT and conventional monitoring groups did not have significantly different flap failure rates from one another, and CT angiography revealed no significant pressure effect by NPWT on flap pedicles. The NPWT-generated pressure was considered minimal. Second, this retrospective study involved relatively short follow-up. Surgical characteristics, such as initial wound condition and flap types, were not evaluated, and the patients were heterogeneous in terms of medical history and flap types, which could have affected surgical outcomes, including complication and survival rates. Furthermore, there were no specific indications or criteria for selecting between conventional monitoring and the NPWT monitoring system. The novel NPWT monitoring system achieved acceptable surgical outcomes compared with those reported in previous studies of DFU patients, and the study findings support the safety of the system. Future larger-scale, prospective, and controlled investigations are warranted to validate the findings of this study, which demonstrated the simplicity and safety of a novel NPWT monitoring system in terms of comparisons with conventional manual monitoring.