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\begin{document}

\title{Effects of acellular dermal matrix on the prevention of complications
and aesthetic outcome after parotidectomy}



\author[1]{Jian-hui Wu}%
\author[1]{Wei  Zeng}%
\author[1]{Min-Yi  Fu}%
\author[1]{Fei  Ye}%
\affil[1]{Sun Yat-Sen University}%


\vspace{-1em}



  
  \date{May 16, 2024}


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\selectlanguage{english}
\begin{abstract}
Objective: The present study was designed to investigate whether
acellular dermal matrix (ADM) graft could prevent Frey's syndrome (FS)
and improve aesthetic score following parotidectomy. Study Design:
Retrospective study. A propensity score matched analysis. Setting:From
January 2015 to December 2019, 175 patients underwent parotidectomy.
Methods: We divided the patients into two groups with ADM group and
Control group. We included each group of 30 patients according a
propensity score matched analysis. Results: The subjective of FS was
recorded in 1 patient (3\%) from the ADM group and 9 patients (30\%)
from the Control group(P=0.015). Patients in the ADM group had a
subjective aesthetic score of 6.1+1.7 compared with 5.2+1.7 in the
Control group. The subjective aesthetic score for patients in the ADM
group was higher than those in the Control group (P =0.040). Conclusion:
The present clinical study suggests that ADM graft are effective in
preventing FS and improving aesthetic score after parotidectomy.%
\end{abstract}%



\sloppy


\textbf{INTRODUCTION}

The approximately 80\% of parotid tumors are benign tumor, and surgical
removal is the primary treatment for parotid tumors. (1) Benign tumors
are commonly located in the superficial lobe. Complete excision of
benign parotid tumors with an adequate margin of normal tissue is
recommended, resulting in partial superficial, superficial, or even
subtotal and total parotidectomy. (2, 3)

This parotid surgery has several adverse effects, including facial
palsy, sialocele or salivary fistula, sensory deficit, Frey's syndrome
(FS), scars, and facial depression. (4, 5) Normally, the majority of
facial palsy were temporary facial paresis. FS is common complication
with affecting the quality of life. FS, also known as Gustatory Sweating
syndrome, is characterized by gustatory sweating and gustatory flushing.
(6) The incidence of FS has been reported in many articles with variable
percentages. The overall average for FS is between 12.5\% and 62\% for
subjective method and 86\% to 98\% when objective testing is performed
with Minor's Starch-Iodine Test. (7, 8) Some patients report even having
distressing symptoms. (9) Botulinum toxin A has been proved effective in
the treatment of FS,7 however, its therapeutic modalities are rarely
permanent in efficacy. (10) So, the trends of treatment have been build
a barrier between skin and parotid gland. (8, 11)

The facial depression in the periauricular and retromandibular areas
were almost unavoidable with the removal of the parotid gland and
tumors, which causing apparent asymmetry. The leads low aesthetic score,
particularly in young people and those benign tumor patients. (12, 13)
So, the areas need to be reconstructed with other tissues.

Some previous study have reported a variety of measures to prevent FS
and the facial depression in the periauricular and retromandibular
areas, such as a sternocleidomastoid, superficial muscular aponeurotic
system, vascularized free flap, temporoparietal fascial flap,

the free or vascularized dermal-fat graft, etc. (14-16) Those measures
have its advantages and disadvantages. (11)

Acellular dermal matrix (ADM) can act as a biological scaffold for
re-epithelialisation, neovascularisation, and infiltration of
fibroblasts, but it does not produce an immune response. (17) It acts as
an ideal alternative for tissue augmentation and barrier to preventing
FS and facial depression after parotidectomy. (18, 19) The purpose of
the present retrospective study was to investigate the complications and
aesthetic effects of ADM after parotidectomy.

\textbf{METHODS}

Our study ruled the Declaration of Helsinki regarding ethics guidelines.
The study protocol was approved by the '{[}removed for blind peer
review{]}'. The latter waived written informed consent because of the
retrospective nature of our study. Our ethics committee ('{[}removed for
blind peer review{]}') approved the waiver of informed consent for this
study.

All consecutive patients undergoing partial superficial or superficial
or subtotal or total parotidectomy between January 2015 and December
2019 were included in this study. All patients underwent preoperative
diagnosis by ultrasound or computed tomography (CT) scan. Patients were
excluded from the study for the following reasons: (1) postoperative
pathology suggests malignancy tumor; (2) previous history of radiation
therapy or operated to the head and neck region; (3) incomplete medical
records or follow-up. We collected all kinds of data including sex, age,
type of tumor, type of parotidectomy, and tumor size, specimen volume,
diabetes mellitus, hypertension, etc. The postoperative complication,
drainage, aesthetic score outcome were analyzed. All patients were
followed up for at least 6 months.

Parotidectomy was performed in the standard manner (Fig 1A, 1B). All
parotid operations were performed by 1 of 2 experienced chief physician.
The marginal mandibular of the facial nerve was first identified, and
then a retrograde dissection of the nerve was performed. The acellular
dermal matrix (ADM) used in our study was J1-ADM (Beijing Jayyalife
Biological Technology Co. Ltd., Beijing, China). The ADM size was
selected by the actual needs of operation. All patients were placed on
prophylactic antibiotics for the duration their drain was in place.

Frey's syndrome (FS) and aesthetic score was evaluated by subjective
methods. For the subjective FS evaluation, patients were queried about
warming, flushing, or sweating over the preauricular regions during the
follow-up period. For the subjective aesthetic score was achieved by
asking patients to complete a questionnaire designed to assess their
satisfaction with the resulting scar and upper cervical and
retromandibular contour. Subjective aesthetic score was scaled from 1 to
10 (1 representing very dissatisfied; 10 representing very
satisfied).(20)

The mean and variance were used as continuous variables and n (\%) were
used as categorical variables. T test was used for continuous variables
and Pearson Chi-square test or Fisher's exact test were used for
categorical variables. \emph{P} \textless{} 0.05 was considered
statistically significant. Statistical analysis was performed using SPSS
22.0 for Windows.

\textbf{RESULTS}

Patient profiles

Table 1 shows patient profiles before and after propensity score
matching. A total of 175 patients with 33 patients in ADM group were
enrolled in this study. Before propensity score-matching, the ADM group
contained lower age, size of tumor, and volume of specimen, than those
in the Control group. Moreover, the type of parotidectomy in the Control
group were significantly difference than the type in the ADM group
(\emph{P} = 0.008). As a result, the rate of male and hypertension in
both groups was similar (\emph{P} = 0.447, \emph{P} =0.902). After
propensity score-matching, both groups were well matched in all
parameters. 30 patients each were allocated to the ADM group and the
Control group. Pleomorphic adenomas and Warthin's tumors were the most
frequent histological type in two groups. 25 patients (83\%) or 23
patients (77\%) underwent partial superficial parotidectomy, followed by
superficial parotidectomy (4 patients in ADM group and 6 patients in
Control group).

Complications

Overall complication rates are shown in Table 2. ADM group were
associated with a total of 5 complications (17\%), whereas Control group
were associated with a total of 13 complications (43\%) (\emph{P}
=0.024).

Postoperative facial function was graded on the House-Brackmann scale in
all patients. 3 patients (10\%) in the ADM group and 4 patients (13\%)
in the Control group had facial palsy, with initially founded on the
first day after operation. The postoperative facial palsy did not get
statistical significance between two groups. All patients except the two
Nerve Schwannoma patients fully regained normal facial function within 6
months. The two Nerve Schwannoma patients in either group developed
permanent facial palsy with grade IV.

1 patient (3\%) in the ADM group and 6 patients (20\%) in the Control
group developed a sialocele or salivary fistula. No significant
difference was achieved between the two groups (\emph{P} =0.108).

1(3\%) patient in the ADM group and 9(30\%) patients in the Control
group experienced sweating over the preauricular regions 6 months after
the operation. There was statistically significant difference between
the two groups in subjective Frey syndrome (FS) (\emph{P} =0.015).

The most common complication was sensory deficit in both groups.
Numbness in the infra-auricular region occurred in 4 patients (13\%) in
the ADM group and in 7 patients (23\%) in the Control group (\emph{P}
=0.317). 9 of the 11 patients with sensory deficit recovered sensation
within 6 months after the operation.

None of the patients in the ADM group experienced complications at the
donor site. No patient in either group had tumor recurrence and seromas
during the follow-up period.

Postoperative drainage

The postoperative drainage in the ADM group was 59.7\emph{+} 26.0 mL,
whereas the postoperative drainage in the Control group was
110.0\emph{+} 78.7mL. Postoperative drainage was significantly decreased
in the ADM group compared with the Control group (Fig. 2A) (\emph{P}
=0.002). The postoperative drainage time in the ADM group was
3.6\emph{+} 0.8 days, whereas the postoperative drainage time in the
Control group was 4.7\emph{+} 1.7days. Postoperative drainage time was
significantly lower in the ADM group compared with the Control group
(Fig. 2B) (\emph{P} =0.001).

Expect the sialocele or salivary fistula patients, the postoperative
drainage in the ADM group (29 patients) was 58.3\emph{+} 25.3 mL,
whereas the postoperative drainage in the Control group (24 patients)
was 95.3\emph{+} 72.6mL. Postoperative drainage was also significantly
decreased in the ADM group compared with the Control group (\emph{P}
=0.013). The postoperative drainage time in the ADM group was
3.6\emph{+} 0.8 days, whereas the postoperative drainage time in the
Control group was 4.5\emph{+} 1.6days. Postoperative drainage time was
also significantly lower in the ADM group compared with the Control
group (\emph{P} =0.010).

Subjective aesthetic score

Patients in the ADM group had a subjective aesthetic score of
6.1\emph{+} 1.7 compared with 5.2\emph{+} 1.7 in the Control group (Fig.
3). The subjective aesthetic score for patients in the ADM group was
higher than those in the Control group (\emph{P} =0.040).

\textbf{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(\emph{P} =0.015). And the overall complication rate of 5(17\%) in
ADM group was lower than 13(43\%) in control group(\emph{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(\emph{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
(\emph{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
(\emph{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.

\textbf{Data availability statement}

The datasets generated and analyzed during the current study are
available from the corresponding author on reasonable request.

\textbf{Conflict of interest statement:} The authors declare no
potential conflicts of interest.

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\textbf{Figure legends}

Fig 1. (A) Partial resection of superficial lobe and tumor. (B)
acellular dermal matrix implantation.

Fig 2. (A)Comparison of postoperative drainage between two groups. (B)
Comparison of postoperative drainage time between two groups.

Fig 3. Comparison of aesthetic scores between two groups.\selectlanguage{english}
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