## 4 Discussion  
The primary aim of this study was to show a possible reduction in the rate of wound infections following TKA. As neither group incurred primary wound infections, this study cannot state a definite benefit of NPWT over conventional wound dressing methods. However, a reduction in wound edema, which is a significant outcome of this analysis, could lead to the prevention of PJI in patients receiving elective TKA. Furthermore, we established that patients in the NPWT group received fewer dressing changes due to slippage after postoperative physiotherapy regimens, leading to a considerable reduction in person hours and dressing materials. Despite advances in surgery resulting in better outcomes for patients after TKA, the threat of wound complications leading to wound dehiscence or deep prosthetic infection is still a factor an orthopedic surgeon wishes to reduce. Due to the lack of good clinical evidence comparing different types of wound dressings and their effects on SSI, LOS, and cost efficiency, the National Institute for Health and Clinical Excellence (NICE, UK) has suggested further research in this area [26]. A study focus on the use of chronic wound dressings in acute wounds is therefore encouraged. With the known positive effects of NPWT in the healing of chronic and acute wounds, it was therefore paramount to access the benefits of such a system in the prevention of wound complications. PJI is a feared complication that results in narrowing and severe situations for the patient and leads to great financial burdens to payment systems and hospitals administering to these patients [27]. PJI inevitably leads to surgical revision of infected joints and may result in removal of the prosthesis with severe loss of function and mobility. Studies have shown that the rate of PJI following primary TKA ranges between 0.5% and 5% [28; 29]. In revision knee surgery, the risk is further increased. Impaired primary wound healing can be linked to PJI--amongst others, intrinsic factors such as rheumatoid arthritis [30], diabetes, use of steroids, obesity as well as local factors such as poor vascular perfusion andymphedema are known to lead to problems in primary wound healing and subsequently in some cases to PJI [31]. [PERSON] et al. [32] showed that patients with wound healing problems were at a significantly greater risk for further complications. Other studies suggest that SSI also prolongs the length of stay after orthopedic surgery [33]. Our study found no significant reduction in wound infection in either group as none of the included patients developed a primary infection during the trial. Wound dressings play a significant role in postoperative patient care. Not only should they create a milieu promoting tissue growth, but they should also protect newly grown tissue from damage. Adequate dressings minimize infection to the wound by being  
Figure 6: Hemoglobin change over observation time. Shown is the mean with error bars indicating 95% confidence interval. impermeable to bacteria [34] while at the same time being absorbent, especially in wounds with high exude levels. Prolonged wound drainage has been associated with an increase in LOS and postoperative morbidity in patients after TKA [35]. We observed a significant reduction in early wound edema and a tendency toward reduced secretion, both of which are known factors leading to secondary wound complications, although the latter was not statistically significant. Their reduction might therefore avert such difficulties. Considering the anatomy of the knee, it was also important to verify the resilience of such a system as it would have to function sufficiently despite a wide range of repetitive movement in the knee joint following postoperative physiotherapeutic protocols. [PERSON] et al., in their study on the effects of incisional NWPT in hip and knee arthroplasty, described a significant reduction of dressing changes while using the PICO system [25].