Secondary outcome indicators
Surgical duration
Eight studies15-22 described the surgical duration for
submandibular gland resection through the retroauricular hairline
approach. A total of 330 patients underwent submandibular gland
resections; 144 through the retroauricular hairline approach and 186
through the conventional approach. The surgical duration for the
retroauricular hairline approach was significantly longer than that for
the conventional approach (WMD: 27.26; 95% CI: 6.35–48.18; P = 0.01;
Fig. 5), and there was significant heterogeneity among the studies (χ2 =
613.23, df = 7, P = 0.01, I2 = 99%; Fig. 5). Visual assessment of the
funnel plot indicated a slight publication bias. However, the Egger’s
test was not statistically significant (p = 0.126) (Fig 6).
3.3 Wound length
Four of the studies15-17, 22 described the wound
length in 126 patients; 62 and 64 in the retroauricular and conventional
approach groups, respectively. The retroauricular hairline group had
significantly longer wound lengths compared to the conventional group
(WMD: 4.65; 95% CI: 1.94–7.36; P = 0.0008; Fig. 7). There was
significant heterogeneity among the studies (χ2 =
120.03, df = 3, P = 0.0008, I2 = 98%; Fig. 7).
3.4 Intraoperative bleeding
Intraoperative bleeding volume was described in two of the
studies16, 22, with a total of 88 patients; 43 and 45
in the retroauricular and conventional approach groups, respectively.
There were no statistically significant differences between the two
surgical approaches (WMD: −7.39; 95% CI: −28.40–43.61; P = 0.49; Fig
8). There was significant heterogeneity among the studies
(χ2 = 28.85, df = 1, P = 0.00001, I2= 97%; Fig. 8).
3.5 Postoperative drainage
Postoperative drainage was described in three of the
studies18, 19, 22, with a total of 130 patients; 64
and 66 in the retroauricular hairline and conventional approach groups,
respectively. Data pooling showed no significant differences in
postoperative drainage between the two approaches (WMD: 17.49; 95% CI:
−4.36–39.34; P = 0.12; Fig 9). There was significant heterogeneity
among the studies (χ2 =28.93, df = 2, P<0.00001,
I2 = 93%; Fig. 9).
3.6 Length of hospital stay
Five of the studies reported the duration of
hospitalization15, 17-20, 22. A total of 168 patients
underwent submandibular gland resection; 83 and 85 through the
retroauricular hairline and conventional approaches, respectively. The
results showed no significant difference in the number of hospital days
between the two groups (WMD: −0.25; 95% CI: −0.99–0.49; P = 0.51; Fig
10).
3.7 Cosmetic effects
Two of the studies [15-16] described cosmetic effects using a visual
analogue scale (VAS) in 58 patients, 28 and 30 in the retroauricular and
conventional approach groups, respectively. The VAS uses objective
content satisfaction scores on a scale of 0–10; the higher the score,
the higher the satisfaction level. The retroauricular hairline group had
significantly better cosmetic effects than the conventional group. The
difference in cosmetic effects between the two surgical approaches was
statistically significant (WMD: 3.83; 95% CI: 2.50–5.16; P<0.00001;
Fig 11). There was greater heterogeneity among the studies
(χ2 =2.62, df = 1, P = 0.11, I2 =
62%; Fig. 11).
Only two of the studies reported the intraoperative bleeding
volume16, 22, which made it difficult to perform a
subgroup analysis. Furthermore, postoperative drainage and cosmetic
effects were not reported adequately to perform a subgroup analysis.
3.8.1 Open submandibular gland excision
Compared to the original analysis, there were no significant differences
in the subgroup analysis for surgical durations of open submandibular
gland excision through the two approaches (WMD: 0.60; 95% CI:
−18.00–19.20; P = 0.95; Fig 5).
3.8.2 Endoscopic submandibular gland excision
Compared to the original analysis, the subgroup analysis was consistent
with the original data analysis for surgical duration (WMD: 30.83; 95%
CI: 7.39–54.27; P = 0.010; Fig 5), wound length (WMD: 5.76; 95% CI:
5.22–6.29; P < 0.00001; Fig 7), and length of hospital stay
(WMD: −0.77; 95% CI: −2.20–0.67; P = 0.30; Fig 10).
3.8.3 Robotic submandibular gland excision
Compared to the original analysis, there were no significant differences
in the subgroup analysis for surgical duration between the two groups
(WMD: 48.24; 95% CI: −14.27–110.75; P = 0.13; Fig 5).
3.9 Sensitivity analysis
To evaluate the robustness and reliability of our results, we performed
a sensitivity analysis. For articles with a significant percentage, we
excluded and re-analyzed the data.
3.9.1 Forest plot and
meta-analysis for temporary injury to other nerves.
In this study by Carlos et al, there was a significantly higher
proportion of the outcome metric of temporary injury to other nerves
than in other literature. After excluding this study, the outcome was
consistent with the original data analysist (OR: 0.77; 95% CI:
0.24–2.40; P = 0.65; Fig. 12). This was consistent with the original
consolidated results and showed that the results were stable.