This study aimed to describe the learning curve of surgeons performing tibial cortex transverse transport (TTT) and explore the safety and effectiveness of TTT during the initial stages of surgeon’s learning.

The clinical data of patients with diabetic foot ulcers classified as Wagner grade ≥2, who underwent TTT at our hospital from January 2020 to July 2021, were included in this retrospective analysis. All procedures were performed by the same physician. The patients were numbered according to the chronological order of their surgery dates. The cumulative sum and piecewise linear regression were used to evaluate the surgeon's learning curve, identify the cutoff point, and divide the patients into the learning group and the mastery group. A minimum follow-up period of 3 months was ensured for all patients. Baseline data, perioperative parameters, complications, and efficacy evaluation indicators were recorded and compared between the two groups.

The patients were numbered according to the date of operation. The learning curve based on operation time was calculated by the CUSUM analysis [25-27]. The equation was defined as: CUSUM=, where yi indicated the operation time for each case,  represented the average operation time for all cases [28], and n represented the number of consecutive cases. A scatter plot was generated with consecutive cases and CUSUM values, and the scatter plot was fitted using IBM SPSS, version 25.0 (IBM Corp, Armonk, NY, USA) to obtain the functional equation. The slope of the equation was used to estimate the cutoff point of the learning curve, dividing the 60 patients into the learning group and the mastery group. The cutoff point corresponded to the minimum number of cases required for the physician to through the stage of experience accumulation[28]. It was assumed that the best-fit line in the scatter plot of case-time consisted of two straight lines connected at the cutoff point. Thus, the fitting equation was defined as: y = a - bn (n ≤ n'), y = c (n > n'), where y represented the operation time, n represented the number of cases, n' represented the cutoff point, and a, b, and c were constants. The degree of fit of this model was evaluated. The fitting degree of the curve was judged by the coefficient of determination R²: the closer the coefficient was to 1, the higher the degree of the model fitting was.

Based on inclusion and exclusion criteria, a total of 60 patients were included in this study. After the completion of 20 TTT surgeries, the surgeon reached the cutoff point of the learning curve. Compared to the learning group, the mastery group demonstrated a significant reduction in the average duration of the surgical procedure (34.88 minutes vs. 54.20 minutes, P < 0.05), along with a notable decrease in the frequency of intraoperative fluoroscopy (9.75 times vs. 16.9 times, P < 0.05), while there was no significant difference found in terms of intraoperative blood loss (P = 0.318). Of the total patient cohort, 7 individuals (11.7%) experienced complications, with 3 cases (15%) occurring during the learning phase and 4 cases (10%) during the mastery phase. The postoperative ulcer area exhibited a significant reduction, and the overall healing rate reached 94.8%. Notably, there were significant improvements observed in postoperative VAS scores, ABI index, and WIFI classification (P < 0.05). And there were no statistically significant differences in the occurrence of complications and efficacy indicators between the learning group and the mastery group (P > 0.05).

Surgeons can master the skills of TTT after completing approximately 20 procedures. TTT emerges as an easy, secure, and highly efficient therapeutic approach for addressing diabetic foot ulcers. Furthermore, the application of TTT by surgeons can achieve almost consistent clinical outcomes in the initial stages of implementation comparable to the mastery phase.