The development of local wound complications, such as seroma, sialocele, and salivary fistula, which are generally considered to be due to constant fluid secretion from saliva-producing parenchyma, has been reported in 5−39% of parotid surgeries [31,32]. These complications worsen the wound and decrease the quality of life [33]. Although they inevitably occur when operating on the salivary glands, it is believed that they can be reduced by improvements in surgical techniques [26]. For instance, some surgeons suggest that techniques to reduce dead space, including drain placement, pressure dressing, or fibrin glue, can reduce the incidence of postoperative seroma [26]. Retrospective studies with approximately 100 patients and one randomized control study of 22 patients reported inconclusive results on the reduction of wound complications with the use of fibrin glue in parotidectomy [34]. To our knowledge, there is currently no study reporting the use of a fixed combination of a collagen sponge patch with a fibrinogen and thrombin layer product.

TachoSil^®® is a ready-to-use third-generation agent based on a collagen patch coated with a mixture of human fibrinogen and thrombin [18], and was originally developed for hemostasis. However, its efficacy for tissue sealing has also been confirmed in liver, lung, and kidney surgery [34]. Its beneficial properties in terms of hemostatic efficacy and high adhesive strength have been reported for controlling diffuse oozing-type and suture-hole bleeding, and to occlude structures such as the bronchioles, lymph vessels, bile ducts, and organ ruptures [3,18]. Given these clinical properties, we hypothesized that using TachoSil^®® as a fibrinogen-thrombin-impregnated collagen patch may reduce postoperative drainage and other complications associated with saliva leakage in parotid gland surgery. To the best of our knowledge, this is the first study evaluating the effect of a fibrinogen-thrombin-impregnated collagen patch on decreasing postoperative drainage and other complications in parotid surgery.

We also demonstrated that the application of a fibrinogen-thrombin-collagen sponge patch can prevent Frey’s syndrome and is effective for surgical depression. We were able to contact all our patients via phone to assess their subjective symptoms and found that 7% (11 of 157) reported Frey’s syndrome. Generally, 10% of patients complain of symptoms, approximately 30 to 40% admit to symptoms with questioning, and 90% have some degree of gustatory sweating with the starch iodine test [35,36]; the rate of incidence for Frey’s syndrome was low in our study [35]. As the follow-up period in this study may not have been sufficient to confirm Frey’s syndrome, its incidence may increase over time, presumably due to the time necessary for nerve regrowth. Intriguingly, Frey’s syndrome tended to occur less frequently in the fibrinogen-thrombin-impregnated collagen patch group even in the adjusted model. This is probably because the physical barrier formed by the collagen patch prevented parasympathetic nerve branches to the cutaneous sweat glands [37,38]. Numerous studies have tried to prevent the development of Frey’s syndrome with a similar concept using sternocleidomastoid muscle flaps [39], platysma muscle flaps [40], temporalis fascia flaps [41], SMAS flaps [17], adipose tissue [41], fascia lata [42], dermal matrix [37], Gore-Tex [43], and lipolyzed dura [44] with varying results. Govindaraj et al. reported that placement of allograft dermis implants decreased the incidence of Frey’s syndrome with a subjective rate of 9% vs. 3% in control vs. implanted groups, respectively, and with objective testing revealing gustatory sweating in 40% vs. 0% in the control and implanted groups, respectively [45]. Similarly, our data showed that the incidence of Frey’s syndrome decreased from 10.8% in the control group to 2.7% in the patch group. However, our data still has a limitation in that the statistical power is not high because the incidence of most complications, including Frey’s syndrome, is not high in both groups. More studies are needed to confirm the results.

In addition, because depression of the facial contour after parotidectomy remains challenging to surgeons, and facial contour asymmetry and cosmetic results may affect patients’ quality of life, surgical adjuvant techniques have been attempted to minimize surgical depression induced by resection of the gland parenchyma; these include the SMAS advancement flap, fascia lata flap, and sternocleidomastoid muscle flap [46]. However, these methods may cause donor site morbidity. To avoid this additional risk, we tried to elucidate whether the fibrinogen-thrombin collagen sponge patch could improve facial deformity. Although it is an important factor influencing the quality of life, there is no objective analysis of facial asymmetry after parotid surgery; instead, relatively subjective methods, such as questionnaires or visual analog scales, have been used [47,48]. In this study, we attempted an objective analysis using 2D and 3D photometry to compare facial contouring after parotidectomy for the first time. Initially, the asymmetry ratio was positive in both groups when the region of interest (ROI) was defined as the surgical site, due to protrusion caused by the tumor mass. However, after surgery, a significant portion of the salivary glands, including the tumor, was removed; therefore, the ratio decreased in both groups, but the degree of reduction was significantly less in the collagen patch group than that in the control group. As a result, the asymmetry index was negative in the control group, while it remained positive in the collagen patch group; we do not consider that the patch alone filled the defect. Given that, however, the number of total parotidectomies tended to be higher in the control group, and a statistically significantly larger amount of tissue was surgically removed in the fibrinogen-thrombin-collagen sponge patch group, our data highlight the possible effect of fibrinogen-thrombin-collagen sponge patch on postoperative facial asymmetry.

One previous study in a canine model histologically demonstrated that TachoSil^®® could repair a pleural defect by providing a mechanical scaffold on which healing could proceed without negatively affecting the lung parenchyma, followed by complete biodegradation; thus, we presume that it acted as a scaffold for neo-tissue formation in our study [18]. Although the exact mechanism for fibrotic neo-tissue formation remains unknown, we demonstrated that TachoSil^®® was replaced by fibrotic neo-tissue 1-month postoperatively, with resolved early-stage inflammation in a nude mouse salivary gland surgery model. Moreover, this was indirectly inferred on the patient’s ultrasound examination after surgery. However, in future studies, an objective comparison of soft tissue contours at least 1 to 2 years after surgery will be necessary to confirm our findings.