The subjects were 111 patients who underwent surgery in the Department of Surgery, Kangwon National University Hospital, from March 2008 to December 2008. As the research method, medical records, pathological results, and tests performed at the time of admission were examined retrospectively.

At the time of admission, surgical methods were determined by considering the underlying diseases and general conditions of the patients, and in cases in which perforated appendicitis had been diagnosed on pre-surgical examination, an open appendectomy was performed. Regardless of the method of surgery, surgeries were performed by a single resident under the supervision of a surgeon. The resident who performed the surgery was a second year resident who had performed more than 30 open appendectomies prior to performing a laparoscopic appendectomy, and he was the attending physician of the patients who underwent open, as well as laparoscopic, appendectomies from March 2008 to December 2008.

Among the 111 patients, the medical records of 2 patients were not sufficient; thus, they were excluded. In the patient group who received an open appendectomy, 6 patients who received spinal and epidural anesthesia were excluded. The mean age of the remaining 103 patients was 34.6 years (range, 5 to 87 years), the number of males was 58 (56.3%), and the number of females was 45 (43.7%). Among the 103 patients, a laparoscopic appendectomy was performed on 50 patients, and an open appendectomy was performed on 53 patients. The patient group receiving an open appendectomy was called group A, and the patient group receiving a laparoscopic appendectomy was called group B. By obtaining the consecutive moving average, 30 patients who underwent a laparoscopic appendectomy in the early period (before the learning curve) were identified as group C, and 20 patients who underwent a laparoscopic appendectomy later (after the learning curve) were identified as group D.

In the open appendectomies, the transverse incision performed by Davis-Rokey was applied, and blood vessels and adjacent tissues were sutured with black silk 3-0. In the appendectomy, ligation was performed using black silk 2-0 [6, 7]. In the laparoscopic appendectomies, three trocars (10 mm, 5 mm, and 5 mm) were used. A 10-mm trocar was inserted into the area below the navel, a 5-mm trocar was inserted into the left lower abdomen, and another 5-mm trocar was inserted into the suprapubic area.

The laparoscope was inserted by using an open method, and for the ligation of blood vessels, the vessel sealing system (Ligasure, Covidien, Boulder, CO, USA) was used. For the resection of the appendix, the base was ligated using the Vicryl endoloop, and for the distal area, the leakage was blocked using clips. Afterwards, the resected appendix was inserted into a specimen retrieval bag and removed from the abdominal cavity through the insertion site of the 10-mm trocar [1, 6].

According to pathological results, acute appendicitis was classified as acute early focal appendicitis, acute suppurative appendicitis, acute gangrenous appendicitis, and perforated appendicitis. The pathological grades were determined by the progression level of inflammation. Early acute appendicitis is 1 point, acute suppurative appendicitis is 2 points, acute necrotic appendicitis is 3 points, and perforated appendicitis is 4 points.

Through a consecutive comparison of operation times, the trend in the changes was analyzed, the moving average was used to predict a learning curve, and the two groups, one prior to and one after the predicted learning curve, were analyzed by using the ANOVA (SPSS ver. 18.0, SPSS Inc., Chicago, IL, USA) program. Cases with P-values < 0.05 were determined to be statistically significant.

The mean ages of the group A and the group B were 40.39 ± 22.16 years and 27.76 ± 15.76 years, respectively, and a statistically significant difference was shown (P-value, 0.001). No difference in the gender ratios of group A and group B was detected (P-value, 0.74). The average operation time of group A was 64.41 ± 29.88 minutes and that of group B was 58.20 ± 20.72 minutes, but this difference was not significant (P-value, 0.225).

The classification of acute appendicitis was converted to a score based on the pathological diagnosis, the score of group A was 2.26 points, that of group B was 1.96 points, a significant difference (P-value, 0.034) (Table 1). The incidences of early focal appendicitis, acute suppurative appendicitis, and acute gangrenous appendicitis of the two groups were not different, but the incidence of perforated appendicitis of the two groups did show a difference (P-value, 0.018).

The average hospitalization period of group A was 5.26 ± 2.09 days, and that of group B was 3.7 ± 1.51 days, which was significantly shorter for group A (P-value < 0.001). Postsurgical complications in group A occurred in 6 cases (11%), and those in group B occurred in 3 cases (6%), but this difference was not significant (P-value, 0.34) (Table 2).

In regard to the complications that developed in the group A after surgery, heart failure occurred in 1 case, a myocardial infarction in 1 case, acute renal failure in 1 case, surgical wound infection in 2 cases, and death after surgery in 1 case. In the group B, surgical wound infection occurred in 3 cases, and all wound infections developed in the area through which the 10-mm trocar had been inserted.

Group B, who received a laparoscopic appendectomy, was divided into 5 groups, 10 patients each, according to the order of the time at which the surgery was performed, assigned as groups 1, 2, 3, 4, and 5, and the moving average was obtained (Fig. 1). At the time of the transition from group 2 to group 3, a shortening of the operation time was shown. Between group 2 and group, 3 no significant difference in the average operation times was shown. A significant difference in the average operation times between group 3 and group 4 (P-value, 0.026), as well as between group 3 and group 5 (P-value < 0.006) was shown; thus, one could hypothesize that the learning curve is 30 cases.

Assuming that the learning curve is 30 cases based on the moving average, the group prior to the learning curve was defined as C group and that after the learning curve was defined as group D, and the differences between the two groups were analyzed by using the ANOVA program. Between group C and group D, the age (P-value, 0.77) and the gender (P-value, 0.053) were not statistically different. The average operation time of C group was 66.83 ± 21.55 minutes, and that of D group was 45.25 ± 10.19 minutes, which is a statistically significantly difference (P-value < 0.0001). In group C, complications developed in 3 cases, and in the group D, complications were not shown (P-value, 0.151). In addition, significant differences were not shown in the hospitalization period and histological examination; thus, 30 cases could, indeed, be defined as the learning curve (Table 3, Fig. 2)