This retrospective cohort study included patients who were diagnosed with acute appendicitis and underwent laparoscopic appendectomy at Armed Forces Yangju Hospital between May 2022 and December 2024.

Acute appendicitis was diagnosed using abdominal computed tomography (CT) scans. The severity of appendicitis was graded as simple, suppurative, periappendiceal abscess, or perforated based on the preoperative CT findings. Umbilical depth on CT was measured from the peritoneal level to the highest level of the skin surface adjacent to the umbilicus (Figure 1A).

This institution performs fewer than 120 laparoscopic surgeries annually by four surgeons, primarily appendectomies. There are no specialized surgical assistants, and one of the circulating nurses rotates randomly to act as the scopist. Conventional laparoscopic appendectomy (CLA) has been the standard treatment in Korean Armed Forces Hospitals. However, a single surgeon introduced SPLA to the Armed Forces Yangju Hospital, while other surgeons continued performing CLA. This surgeon completed four years of residency and one year of fellowship training at a tertiary hospital but had no prior experience in single-port laparoscopic surgery.

Patients were allocated to SPLA or CLA based on both patient preference and the surgeon's clinical judgment. In the early period, patients with severe inflammation (periappendiceal abscess or perforated appendicitis) were treated with CLA, while SPLA was offered to patients with simple or suppurative appendicitis. Patients who declined SPLA also underwent CLA. As the surgeon's experience increased, the indication for SPLA gradually expanded to more advanced inflammation.

The clinical outcomes of patients undergoing SPLA were compared with those undergoing CLA. The learning curve was assessed based on the outcomes of SPLA. Clinical data from electronic medical records were retrospectively reviewed. The study was approved by the Institutional Review Board of Armed Forces Medical Command (2024-01-009), which waived the requirement for informed consent because of its retrospective nature.

All patients received a dose of preoperative empiric antibiotics (intravenous ceftriaxone 2 g) 30 min before the incision was made. SPLA was performed in the following three procedures.

In the opening procedure, the patient was placed in a supine position. A 15–20 mm transumbilical incision was made using the open Hasson technique. A single-port device (Lemon Single, Islemon, South Korea) was inserted, and a pneumoperitoneum was created.

In the appendectomy procedure, the operator stood to the left of the scopist, and used only straight rigid laparoscopic instruments, including a 5 mm scope with a 30-degree angle (Figure 1B). The mesoappendix and the appendiceal artery were resected using an ultrasonic surgical device (Figure 1C). The appendix base was ligated with two Endo-loops (GEMSLOOP-PDO, GEMS, South Korea). The specimens were extracted directly through the port with a grasper during the first 41 cases. After the 42nd case, specimen retrieval bags were used to reduce contamination risk. No surgical drains were placed. If necessary, an additional 5 mm trocar was inserted during surgery in the left lower quadrant area.

In the closure procedure, the fascia was closed with three interrupted sutures, including a figure-of-eight suture at the center. Care was taken to ensure the proper fascia closure to prevent incisional hernia. Both ends of the subcutaneous layer were sutured to minimize dead space. Dermis sutures were completed (Figure 1D).

CLA was performed using the 3-port method. A 12 mm trocar was inserted at the subumbilical area using the open Hasson technique. Additional two 5 mm trocars were placed in the suprapubic and left lower quadrants. The appendectomy followed the same method as in SPLA. The subumbilical fascia was closed, whereas the fascia of the 5 mm port sites was left unclosed. The skin was closed using either a skin stapler or a nylon suture.

Patients were allowed to sip water 8 h after surgery, followed by a solid diet on the next day, regardless of flatus. The progression of the diet was adjusted based on the patient's condition and the surgeon's judgment. Postoperative antibiotics (intravenous ceftriaxone 2 g) were administered the day after surgery if the operative findings indicated a contaminated field. Routine preemptive analgesics (intravenous acetaminophen 1 g) were given immediately after surgery and again before sleep, with oral analgesics starting the following day.

Given the patient's status as a soldier, discharge was generally scheduled after more than seven postoperative days (POD). Patients underwent open follow-up after discharge. For those who requested earlier discharge, it was permitted only after confirming adequate pain control and diet tolerance through physical examination. Those discharged before seven POD underwent follow-up within 1–2 weeks after discharge.

Postoperative pain was assessed based on the number of rescue analgesics administered (9, 10). Additional rescue analgesics (intravenous ketorolac 30 mg) were given when patients reported pain with a numerical rating scale score of 4 or higher, with a minimum interval of 4 h between doses (11).

Postoperative surgical complications were graded according to Clavien-Dindo classification (12). The overall postoperative surgical complication rate was defined as Clavien-Dindo grade I or higher. Wound dehiscence referred to superficial skin separation or serosal discharge from the subcutaneous layer, since fascia dehiscence was not reported in overall patients.

Readmissions related to appendectomy were recorded without a limit on duration.

The operation time was analyzed using three methods to assess the learning curve of SPLA.

First, the moving average method smooths short-term fluctuations in operation time, highlighting long-term trends. A moving average order of 10 was used.

Second, cumulative sum (CUSUM) analysis presents the sequential difference between individual operation time and the mean operation time. It is calculated by the following equation, where xi is the individual operation time, and μ is the mean of the overall operation time.CUSUM=∑i=1n(xi−μ)Third, piecewise linear analysis detects changes in trends by dividing the data into distinct segments. A two-breakpoint regression model was applied to the CUSUM results.

IBM SPSS Statistics for Windows, version 27.0 (IBM Corp., Armonk, NY, USA) was used for statistical analyses. The piecewise linear regression analysis was conducted using the R statistical package (version 4.4.3). Categorical variables are presented as numbers and percentages, and were analyzed by the chi-square test, Fisher's exact test, or linear-by-linear test. Continuous variables are presented as the means and ranges, and were analyzed by one-way analysis of variance (ANOVA) among groups. Univariate analysis was performed to identify potential preoperative clinical factors associated with the operation time of SPLA. A Student's t-test was used for binary variables, ANOVA for variables with three or more categories, and a correlation analysis with Spearman's test for continuous variables. Factors with a P-value of less than 0.10 in univariate analysis were subsequently included in multiple linear regression analyses. A P-value of less than 0.05 was considered statistically significant.

Among 303 patients who underwent laparoscopic appendectomy between May 2022 and December 2024, one patient who requested a privacy policy for clinical records was excluded. A total of 125 patients who underwent SPLA and 177 patients who underwent CLA were included in the analysis (Figure 2).

Patient demographics and clinical characteristics are summarized in Table 1. The mean (range) age was 22.3 (18–49), similar in both groups. The mean (range) body mass index was 23.9 kg/m² (16.9–34.9) in SPLA, 24.2 kg/m² (17.2–36.8) in CLA. There were no statistically significant differences in the severity of appendicitis between SPLA and CLA groups (P = 0.862). The mean operation time showed no significant differences between the two groups (SPLA 48.6 min vs. CLA 47.1 min, P = 0.582). However, SPLA was associated with significantly less blood loss and an earlier solid diet start (Blood loss: SPLA 4.4 mL vs. CLA 6.3 mL, P = 0.027; POD of solid diet start: SPLA 1.1 vs. CLA 1.3, P < 0.001). The overall postoperative surgical complication rates did not differ significantly (SPLA 4.8% vs. CLA 5.1%, P = 0.911).

In the SPLA group, wound dehiscence occurred in five patients (4.0%). Two patients (1.6%) required readmission and bedside wound repair, while the other three (2.4%) were treated with simple dressing. One patient (0.8%) underwent reoperation due to an intra-abdominal abscess and a dropped appendicolith. This occurred in the 39th case, where the patient was initially discharged on POD 4 and readmitted on POD 20 due to aggravation of abdominal pain. The CT revealed a 20 mm intra-abdominal abscess with a dropped 2 mm appendicolith inside. As the abdominal pain was not relieved with antibiotic treatment, laparoscopic exploration and removal of the appendicolith were performed on POD 34 (Figure 3).

In the CLA group, wound dehiscence occurred in five patients (2.8%), all managed with simple dressing. One patient (0.6%) developed postoperative ileus on POD 3, which improved with nasogastric tube insertion and fluid therapy. Three patients (1.7%) underwent reoperation after CLA, two patients (1.1%) for intra-abdominal abscess, and one patient (0.6%) for postoperative bleeding.

The moving average method was applied to the operation time of SPLA to visualize trends (Figure 4A). In the piecewise linear analysis of CUSUM, two breakpoints were identified (adjusted R² = 0.918). The first breakpoint was at 13.3 (95% confidence interval, 10.9–15.7) and the second was at 36.0 (95% confidence interval, 29.9–42.1) (Figure 4B). Based on these breakpoints, three learning phases were divided: the initial phase (1st–13th), the competent phase (14th–36th), and the mastery phase (37th–125th).

In the mastery phase, the proportions of the average time consumed for each step of the SPLA were as follows: opening of the abdominal wall, 17.3% (mean 7.7 min, range 3–29); appendectomy, 50.3% (mean 22.4 min, range 9–90); and closure of the abdominal wall, 32.4% (mean 14.4 min, range 5–42).

Patient characteristics and postoperative outcomes of SPLA were compared across the three phases (Table 2). Although the inclusion of SPLA expanded to appendicitis with periappendiceal abscess or perforated appendicitis in the later phases, there was no significant difference in the severity of appendicitis across the phases (P = 0.119). Four patients (3.2%) required additional trocars, and no open conversions were necessary for the overall phases. The mean operation time significantly decreased throughout the phases (70.6 min vs. 52.0 min vs. 44.5 min, P < 0.001). There was a trend toward reduced use of additional rescue analgesics and postoperative surgical complication rates in the mastery phase, but there were no statistical differences (Additional rescue analgesics: 38.5% vs. 39.1% vs. 20.2%, P = 0.068; Postoperative surgical complication rate: 15.4% vs. 4.3% vs. 3.4%, P = 0.101).

Univariate analysis identified that the learning phase, body mass index, umbilical depth, and severity of appendicitis on preoperative CT were potentially associated with the operation time of SPLA (Table 3). Multiple linear regression analysis confirmed that the learning phase, umbilical depth, and severity of appendicitis on preoperative CT were significantly associated factors, whereas body mass index was not (Overall regression P < 0.001, adjusted R² = 0.468, Durbin-Watson = 1.981) (Table 4).