DISCUSSION
Facial nerve preservation is the most important problem in parotidectomy with benign tumors. However, quality of life after parotidectomy should not also be ignored. FS and facial aesthetic have the potential to profoundly impact quality of life after parotidectomy. So, the purpose of this study was to evaluate the complication, including FS, and aesthetic effects of insertion of ADM after parotidectomy with the method of propensity score matched analysis.
One of the mechanisms of FS is caused by an aberrant regeneration between the postganglionic parasympathetic nerve fibers that innervate secretion of the parotid glands and the sympathetic nerve fibers that control the subcutaneous sweat glands and vessels after parotidectomy. (21) The reported that the overall incidence of FS following parotidectomy has been great difference. Most previous reported the subjective incidences of FS are between 10% and 40%, and the objective incidences are up to 90%.(22) One reason for this difference may lose to estimate the no clinic symptoms of gustatory sweating and and gustatory flushing. The other reason may the differences research methods. A reported that the incidence of FS in a prospective group was higher than in a retrospective one. The differences may be clarify that the prospective group was more aware of the possible incidence of FS and symptoms of FS may disappear with time in the retrospective group.
A variety of treatment have been reported over time with advantages and disadvantages. Botulinum toxin type A has become the first-line therapy. However, the durations effect may short from 12.1 months to 17.3 months. (23) Scholars have also reported that building a barrier in the surgical site after parotidectomy can help to prevent FS, including the sternocleidomastoid muscle flap, the temporoparietal fascia flap, the superficial musculoaponeurotic system flap(SMAS), the free or vascularized dermal fat graft, and ADM.
The SMAS layer is the superficial cervicofacial fascia. The SMAS flap is placed between the skin and the surgical site of the parotid region. The SMAS flap can effectively prevent the occurrence of FS following a parotidectomy in benign tumors. (24) The use of SMAS flap is limited in the malignant tumors or the obese patients, which is being resection or sometimes insufficient to cover the surgical site. Another limitation of the SMAS flap may more injure to the marginal mandibular branch or cervical branch of the facial nerve.
The free fat graft is also common barrier after parotidectomy. A reported that ADM and free fat grafts were an equal effective in preventing FS and other complications, including facial palsy, sialocele or salivary fistulas, and sensory deficit. (25) Nosan et al. (26) used free abdominal dermal-fat grafts to preserve the periauricular depression of 9 patients undergoing parotidectomy, and the results showed that the aesthetic scores was improving without significant complications. However, the shortcoming of grafts may be the need of a second surgical site with potential wound infection. The other shortcoming is the potentially unpredictable reabsorption rate without continuous efficiency. Some previous reported reabsorption rates were high with vary from 20% to 90%. (11)
In recent years, ADM has been used in plastic surgery and parotidectomy. Hartzell et al. (27) reported ADM have a satisfactory effect and safe material for breast augmentation. In 2007, Chen et al. (28) reported ADM provided a satisfactory aesthetic result with a low incidence of FS in parotid haemangiomas. Govindaraj et al. (7) reported the use of ADM in the prevention of FS compare with control group for superficial parotidectomy. 64 patients were randomly equal assigned to two groups. The results demonstrated the subjective incidences of FS were 9.3% in control group and 3.1% in ADM group. The objective incidence of FS was 40% in control group and 0% in ADM group. However, the complication rate of 25% in ADM group was higher than 9% in control group. In 2008, Wei et al(29) reported similar conclusion in the incidence of FS after superficial and partial superficial parotidectomy. The subjective and objective incidences of FS were recorded in 61% and 23% from the control group and 2% and2% from the ADM group. Furthermore, the complication of sialocele or salivary fistula in 17% from the control group was higher than that 2% from the ADM group. Luo et al. (19) reported the subjective incidences of FS in ADM group was 1 patient (3.4%) lower than that 14 patients (34.1%) in the control group for total parotidectomy. No cases of complication were observed in either group.
In our study, the subjective incidences of FS in ADM group were 1 patient (3%) lower than that 9 patients (30%) in the control group(P =0.015). And the overall complication rate of 5(17%) in ADM group was lower than 13(43%) in control group(P =0.024). The incidence of FS for both group in our study was resemble to the previous literature. (7, 19, 28, 29) The results of complication have been analogue to the conclusion of Wei et al(29), while difference from the conclusion of Govindaraj et al(7). The reason of difference may partly because the research methods were difference. Although our study has used retrospective study as same as the previous literature, we matched the baseline data according a propensity score matched analysis. We matched some important data including age, gender, type of tumor, size of tumor, volume of specimen, type of parotidectomy, hypertension and diabetes mellitus, which may reduce the bias of data and increase the persuasiveness of conclusions.
In our study, the complication of facial palsy and sensory deficit were no statistical significance. The incidence is related to the surgical technique, tumor size and location, individual feeling etc. The incidence rate of Sialocele or Salivary 1(3%) in ADM group was lower than 6(20%) in control group(P =0.108). However, postoperative drainage and time were significantly decreased or lower in the ADM group compared with the Control group (Fig. 2A and 2B). In the present study, Although the incidence rate of Sialocele or Salivary was no statistical significance, ADM patients experienced a lower rate of postoperative drainage and time when compared with control group. This difference of Sialocele or Salivary and postoperative drainage were thought to be related to the use of the barrier of ADM. Some previous study has shown similar conclusion. Ye et al. (29) reported one salivary fistula was noted in the ADM group, while 18 cases developed in the control group (P = 0.002). We consider that the ADM should completely cover the exposed parotid and facial nerve surface. ADM graft may replace fascia to reduce secretion and promptly eliminate the dead space. When the postoperative drainage is less than 10 ml drainage tube can be removed, and a proper pressure dressing used for about 3-5 days. So, the ADM graft may promote the quality of life after parotidectomy.
The aesthetic score after parotidectomy should also be important considerations. In our study, the subjective aesthetic score for patients in the ADM group was higher than those in the Control group (P =0.040). In 2012, a study reported the use of ADM may reduce postoperative facial contour deformities following total parotidectomy. (19) Ciuman et al(30) also reported that the extent of parotidectomy was related to aesthetic score. In 2019, Kim et al. (9) shown insertion of ADM after parotidectomy, including partial, superficial, and total parotidectomy, may improve aesthetic score. The results also demonstrated the aesthetic score was related to gender and complications. Interestingly, the results showed that women were more satisfied than men. We consider the subjective aesthetic score may no difference in both group before the study. Our research results indicated the factor of subjective aesthetic score are manifold. We guess the factor is related to the age, gender, incision, size of tumor, sample volume, complications, individual feelings etc. There are need further study.
Our study was limited by the small sample, relatively short follow-up time. The FS and aesthetic score were evaluated by subjective methods without objectively assess. The reason is the FS and aesthetic score are higher related to the subjective evaluation than the objective evaluation. So, even if the starch iodine test is positive, or the aesthetic score is low, if a patient suffers no symptoms or satisfied then no intervention is required.
In conclusion, the present clinical study suggests that ADM graft are effective in preventing FS and improving aesthetic score after parotidectomy. More RCTs are needed to confirm
this conclusion and prove the influencing factors of aesthetic score.