Discussion
This meta-analysis included four prospective and four retrospective
studies, with a total of 330 patients, comparing the retroauricular
hairline and conventional approaches for submandibular gland resection.
The retroauricular hairline approach was found to be safe, with better
cosmetic results and similar risk of postoperative nerve damage compared
to the conventional approach. There was no significant difference in the
intraoperative bleeding volume, postoperative drainage, and length of
hospital stay between the two approaches.
Minimally-invasive surgical techniques emerged in the 1980s, and are now
used in various surgical specialties, including abdominal, thoracic, and
gynecological surgery. In recent years, head and neck surgery has made
great strides in minimally-invasive surgery, aiming for improved
esthetics, reduced blood loss, shorter hospital stays, and fewer
complications23, 24. Technological developments and
the demand for improved esthetics have changed the choice of surgical
modalities for submandibular gland removal. The patients also expect
perfect cosmetic results after submandibular gland surgery.
Submandibular gland removal through the transcervical approach may
result in unsightly keloids or hyperplastic scarring. This has led to
the development of various techniques, including intraoral and
retroauricular approaches, to reduce scar formation. Traditional
submandibular gland resection is performed through a transcervical
approach, which is a relatively safe procedure, but can lead to
postoperative neurological complications. In young individuals, the scar
is visible on the exposed part of the neck, which is cosmetically
undesirable, particularly in cases of keloid formation. This places a
tremendous burden on the patients and can have negative psychological
and social effects. Based on the cosmetic requirements,
minimally-invasive approaches for submandibular gland removal, including
the transoral endoscopic approach25, smaller incisions
combined with endoscopic assistance, and retroauricular hairline
approach, have been investigated in the recent years. Intraoral
submandibular gland surgery was described several years ago, but had
limited applicability. Although intraoral surgery results in perfect
cosmetic outcomes, it requires a higher level of surgical expertise, and
the narrow surgical field can make it difficult to ligate the facial
artery. This has limited the wider application of this approach, but it
has been reintroduced in recent years with the development of
robot-assisted surgery [26]. Despite the reduced
length of neck incision, an important disadvantage of small neck
incisions combined with endoscopy is the high level of surgical
expertise required to handle the endoscope. Surgeons must be accustomed
to endoscopic surgical views, and be able to handle a wide variety of
instruments, including endoscopes, grasping forceps, harmonic scalpels,
etc. In terms of cosmetic results, the posterior auricular approach
offers significant advantages compared to conventional submandibular
gland resection.
This meta-analysis demonstrates the feasibility of retroauricular
hairline approach for submandibular gland resections. Although the
retroauricular incision line is approximately 4–6 cm longer than the
traditional transcervical incision, a “scarless” effect is achieved
because the scar is hidden behind the ear and in the hairline,
especially when covered by long hair. This meta-analysis compared the
operative times, wound lengths, intraoperative bleeding volumes,
postoperative drainage, durations of hospital stay, and postoperative
nerve injuries between the postauricular hairline and conventional
approaches for submandibular gland resection. The operative time and
wound length were longer in the postauricular group compared to the
conventional group. However, there were no statistically significant
differences in the intraoperative bleeding volumes, postoperative
drainage, and lengths of hospital stay between the approaches. The
retroauricular hairline group had a higher risk of earlobe numbness, but
this resolved during the follow-up period. There were no differences in
the risk of damage to other nerves between the two approaches. The
present meta-analysis had several limitations. First, half of the
included studies were cohort studies; further prospective randomized
controlled studies are needed to increase the level of evidence. Second,
the differences in the study populations, surgical skill levels, and
other factors could have contributed to heterogeneity among the studies.
In the present study, the heterogeneity for continuous variables was
greater than that for dichotomous variables, so we performed subgroup
and sensitivity analyses. The subgroup analysis for the postauricular
hairline group was performed by dividing the procedures into open,
endoscopic, and robotic surgeries. There was significant heterogeneity
in the surgical duration among the open, endoscopic, and robot-assisted
retroauricular hairline submandibular gland resection subgroups. The
heterogeneity was greater when the three groups were combined
(I2 = 99%; Fig 2), indicating that grouping factors
may not be the source of heterogeneity. In terms of wound lengths
(I2 = 99%), there was no heterogeneity in the
subgroup analysis for the endoscopic retroauricular hairline approach
(I2 = 0%; Fig 3). This indicates that grouping
factors may be the source of heterogeneity. Comparing the lengths of
hospital stay between the two approaches (I2 = 89%;
Fig 6), subgroup analysis revealed no heterogeneity for the
robot-assisted retroauricular hairline submandibular gland resection
(I2 = 0%). However, the heterogeneity was greater in
the endoscopic group, indicating that subgroup factors may be the source
of heterogeneity. Meanwhile, intraoperative bleeding volumes and
postoperative drainage were more heterogeneous, but could not be
analyzed in subgroups because of insufficient data. This was another
important limitation of this meta-analysis.
This study showed that submandibular gland excision by the
retroauricular hairline approach had significantly higher postoperative
cosmetic outcome scores than the traditional approach; the
retroauricular hairline group patients under the age of 30 years had
four times higher postoperative cosmetic outcome scores than the
traditional group21. This difference may be
significant for patients with a cicatricial constitution. The
retroauricular approach was also safer than the traditional cervical
incision because no large neck vessels become exposed if sutures are
lost, leading to necrosis or rupture, which prevents the risk of
catastrophic bleeding27. However, surgeons may be
uncomfortable with the top-to-bottom anatomical orientation for the
retroauricular approach, and the limited access and visibility for
anterior lesions. Although endoscopic surgery provides a magnified of
the narrow surgical space, the assistant must keep the endoscope in
place and move it in concert with the surgeon’s movements. This requires
a close and skilled coordination between the assistant and surgeon.
Robotic submandibular gland resection solves this problem as the surgeon
controls the two robotic arms remotely from a console to perform the
procedure. However, robotic and endoscopic submandibular gland
resections were found to have comparable surgical and cosmetic
outcomes28. With the advent of artificial
intelligence, robotic surgery is emerging as a viable alternative to
traditional open surgery, with potential safety and esthetic advantages.
De Virgilio proposed that the first step in robotic submandibular gland
resection through the retroauricular incision was to identify and ligate
the facial artery and other major arterial and venous branches. This
minimizes the risk of bleeding and improves visibility, further
demonstrating that a large incision does not necessarily lead to poorer
postoperative outcomes10. The robotic retroauricular
hairline approach reduces the incidence of surgical complications
associated with the postauricular anatomy because it does not require
the creation of a surgical tunnel and postauricular flap elevation. It
also reduces the risk of postoperative complications, including seromas
and hematomas, caused by flap elevation. Because the robotic system is
equipped with a magnifying camera and dexterous instruments, the gland
boundaries are clearly identifiable, which facilitates the submandibular
gland stripping and excision29. However, the use of
robotic systems is technically demanding. The advantages of the
retroauricular hairline approach are based on a smaller incision along
the hairline. The large robotic arms of the currently available systems
make the docking process critical, which makes the surgical technique
and placement of robotic instruments more difficult. Without proper arm
positioning, frequent collisions of surgical instruments may occur,
making the procedure more time consuming and
difficult30. The robotic systems are expensive and not
widely available, particularly in developing countries. Although cost
comparison was not done in the present study, it may be a deciding
factor for the clinical application of robotic surgeries. Considering
the economic realities of most countries, the endoscopic technique may
be a more feasible alternative to conventional surgery for the
optimization of esthetic and functional outcomes in selected head and
neck tumor patients.