The adaptations of new technologies are challenges particularly in the practice of medicine [11,12,13,14,15]. There is evidence that the effect of experience is clearly cumulative and can be carried over to later performance [11,12,13,14,15,16,17,18]. With the aim to better understanding of surgeons’ performance during our experience with LKPE, we used CUSUM technology, with combination of CJ and SNL rates, to identify the number of cases that are necessary to achieve the competence of LKPE. These efforts could facilitate more effective training and improve the results of LKPE.
The CUSUM technique is widely used to analyze the learning curve for surgical procedure [11, 12] and transforms raw data into running total data deviation from their group mean, enabling investigators to visualize the milestone of learning curve. In this analysis, CUSUM yielded a parabolic curve showing two distinct phases from which correlates of the LKPE learning curve can be assessed. The median ORTs during the first and second phases were 316.3 min and 232.2 min, respectively. The first phase of steep CUSUM of ORT rapidly rise at case 1~ 20, with a relative stabilization at case 20~ 50, can be attributed to increased familiarity with the ‘basics’ of the performance. These include the optimal port placement, the full exposure of porta hepatis, the initial improvement of skills in dissection, the hemostasis, and the portoenterostomy. The phase 2 after case 50 is likely to represent the steep learning curve that reflects the surgeon’s development of ability.
As shown, patients in both groups were similar in terms of demographics, weight, and type of BA, suggesting that minimal selection bias was present to influence our results. The conversion rate from LKPE to OKPE, any perioperative complications rate, and cholangitis rate was 20, 24 and 78% in group A, each of which was significant higher than that observed in group B. In addition, the CJ rate and SNL rate in group A were worse than that in group B. All perioperative results of both groups mentioned above are highly consistent with the learning curve of LKPE, which was plotted by the cumulative calculation of CUSUM of ORT. A possible explanation for these progression observed in the late-experience period is that the surgeons became more comfortable with postoperative care as they gained experience with the operation.
Interestingly, we observed similar rates of rate of intraoperative transfusion. Although perioperative complications rate increased substantially in group B, this finding did not translate into an overall prolonged hospital length of stay. We found that the median time of oral feeding initiated after operation and the length of hospital stay was not different between two groups.
The 50 cases of learning curve in our study was more than that reported by Li et al. [19]. The authors drew the conclusion that without the usage of Cumulative sum analysis for ORT and Kaplan–Meier analysis for SNL. Nevertheless, we agree with Li that LKPE is really a demanding procedure, especially for novices and those in hospitals with low caseload of BA. In addition, the 50 cases of learning curve of LKPE is more than that of laparoscopic procedure for choledochal cyst reported by Diao’s (35 cases) [20] and that of LPCC reported by Zhe’s (37 cases) [21]. The younger age at operation, the poor exposure of porta hepatis, the difficult assessment for level of dissecting biliary fibrous cone, the challenging procedure for portoenterostomy, all of which may contribute to the “long” learning curve of LKPE.
The age at operation from 1 month to 4 months in our study means that the peritoneal space for manipulation of LKPE is limited. Usually, the full exposure of porta hepatis is often difficult, especially during the initial phase of learning curve. We found that the porta hepatis could be totally displayed by suspension of the segment IV only with percutaneous transhepatic suture. Under the magnification of laparoscopy, the view of operative field can be shown clearly and stably on the screen. Furthermore, the proper level of resecting the bilious fibrous cone is hard to be reached under laparoscopy. Our experiences are that the fibrous cone should be dissected between the first bifurcation of portal vein, and gradually pushed deeper until the leakage or oozing of bile-like liquid is found on the surface of the fibrous stump. Therefore, the base of the fibrous cone would be kept intact. When the portoenterostomy is undertaken, the seams of the anastomoses should be kept as far as possible from the surface of the stump. In addition, the rigorous steroids and prophylactic antibiotic treatment for cholangitis after operation is also necessary for achievement for better long-term results.
Although the outcomes of LKPE are not satisfied with OKPE in some reports [6, 22, 23], our recent study revealed that the 3-year and 5 year SNL rates after LKPE were not different compared to those after OKPE. Because BA is a rare disease, the experiences of LKPE are incapable to be cumulated to proficiency in a short time, especially in hospitals or centers with the low caseload of BA. However, the learning curve of LKPE can be shortened by training in the animal experiments, the training devices, such as laparoscopic box and the virtual reality laparoscopic simulator.
Our study has several limitations. Firstly, as a retrospective review, nearly all cases are typeIII non-syndromic BA, which may not fully represent the entire population of BA. Most patients of syndromic BA in our hospital were given up by their parents, which could have an impact on the learning curve of LKPE. Secondly, the learning curve may actually be shorter than 50 cases for surgeons already experienced in some facets of laparoscopic surgery. The staffs with prior laparoscopic experience and training have been able to climb this learning curve much more rapidly, especially that there are many cases of BA performed each year. Thirdly, the present learning curve analysis is based mainly on ORT, CJ and SNL, which probably failed to display constant significant improvements as a result of small sample sizes.