
==== Front
Ann Med
Ann Med
Annals of Medicine
0785-3890
1365-2060
Taylor & Francis

39212199
10.1080/07853890.2024.2363940
2363940
Version of Record
Research Article
Medical Education
Enhancing cosmetic suturing skill acquisition in surgical residents through spaced learning training: a randomized controlled trial
X. Yan et al.
Yan Xinjian a#
Abudouresuli Adilijiang. b
Yuemaier Abudukeremu. b
Ge Yan c
Shang Shiyao d
Yang Jue a
Zhang Liulu e#
a Department of Cardiac Surgery, Guangdong Provincial People’s Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou, China
b The Center of Cardiovascular Surgery, The First People’ Hospital of Kashi Prefecture, Kashi, China
c Department of Pathology, Guangdong Provincial People’s Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou, China
d Department of Ultrasound, Guangdong Provincial People’s Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou, China
e Department of Breast Cancer, Cancer Center, Guangdong Provincial People’s Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou, China
# These authors contributed equally to the work.

Supplemental data for this article can be accessed online at https://doi.org/10.1080/07853890.2024.2363940.

CONTACT Liulu Zhang zhangliulu@gdph.org.cn Department of Breast Cancer, Cancer Center, Guangdong Provincial People’s Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou, 510080 Guangdong, China.
30 8 2024
2024
30 8 2024
56 1 236394024 8 2023
29 3 2024
31 3 2024
KnowledgeWorks Global Ltd.28 8 2024
published online in a building issue28 8 2024
© 2024 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group
2024
The Author(s)
https://creativecommons.org/licenses/by-nc/4.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent.

Abstract

Background

Previous research has strongly supported the utility of spaced learning in enhancing memory, but its effectiveness in complex surgical procedures has largely been unexplored. The main objective of this study was to evaluate whether, in comparison to concentrated learning, spaced learning improves the short-term acquisition and long-term retention of cosmetic suturing skills as outcomes of surgical resident training courses.

Methods

This randomized controlled trial was conducted from February 2023 to June 2023. Surgical residents were recruited from a teaching hospital in Guangzhou, China. The participants were randomly assigned at a 1:1 ratio to either the spaced training group (40 min of training followed by a 20-minute break) or the concentrated training group (3 h of continuous training), in which they received one-on-one training for cosmetic suturing skills. The short-term acquisition and long-term retention outcomes were evaluated by three independent raters using an objective scoring scale to assess the participants’ cosmetic suturing skills before the training (pretraining test), within one hour after the training (posttraining test), and three months after the completion of the training (follow-up test). The score for each participant was calculated as the average of three independent scores.

Results

The study included 23 surgical residents, 12 in the spaced training group and 11 in the concentrated training group. The pretraining test revealed no significant difference between the groups. However, in the post-training test, the spaced training group achieved a significantly higher total score than did the concentrated training group (74.06 ± 5.87 vs. 63.43 ± 10.73, p = 0.0070). Specifically, the suture technique scores were 28.46 ± 1.78 and 22.85 ± 3.75, respectively, which were significantly different (p = 0.0002). During the long-term follow-up test, the spaced training group consistently outperformed the concentrated training group by having significantly higher total (75.60 ± 4.78 vs. 60.68 ± 10.40, p = 0.0001), suture quality (32.26 ± 4.01 vs. 26.23 ± 4.16, p = 0.0019), suture technique (28.68 ± 2.63 vs. 22.18 ± 3.94, p = 0.0001), and suturing time scores (14.67 ± 1.15 vs. 12.27 ± 6.07, p = 0.0460).

Conclusions

Incorporating the principles of spaced learning into the instructional process of obtaining cosmetic suture skills for surgical residents not only significantly enhances short-term skill improvement but also contributes to the long-term retention of training outcomes.

KEY MESSAGES

During the post-training test conducted to evaluate short-term impacts, the spaced training group showed notably elevated overall scores, particularly in the domain of suture technique, compared to the concentrated training group.

In the long-term follow-up test, the spaced training group achieved significantly higher scores on the overall test, suture quality, suture technique, and suturing time than the concentrated training group.

By incorporating the principles of spaced learning into the instructional process of cosmetic suture skills for surgical residents, not only does it significantly enhance short-term skill improvement, but it also contributes to the long-term retention of training outcomes.

Keywords

Spaced learning
surgical residents
cosmetic suturing skills
This study was supported by grants from the Teaching Research and Reform Project at South China University of Technology, grants Science and Technology Program of Guangzhou (202201011459) and NSFC Pilot Project Funds of GDPH (8210100979, 8220020505, 8220103662).
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pmcIntroduction

The field of medical education requires learners to assimilate, retain, and apply a substantial amount of knowledge at every stage of their training. However, this endeavour is subject to the limitations of human memory. Renowned psychologist Hermann Ebbinghaus coined this phenomenon the ‘forgetfulness curve’ [1]. In essence, the information acquired by learners tends to dissipate within a few hours, with 90% of their memories fading within a week. As medical education institutions allocate diminishing amounts of time to teaching, students are confronted with dwindling opportunities to acquire essential academic knowledge while honing their practical clinical skills. Therefore, it is paramount to seek an effective teaching method that not only reduces the overall time required to achieve proficiency but also aids in the long-term retention of training outcomes.

Drawing upon the ‘forgetfulness curve’ theory, Hermann Ebbinghaus also proposed a potential approach to counteract forgetting. This method involves reintroducing newly learned information at specific time intervals along the forgetfulness curve, ideally within one hour. By doing so, the precipitous decline in retention can be mitigated [1]. The practice of incorporating active breaks and repeated studying between learning sessions to facilitate the formation of long-term memory is known as ‘spaced learning’. The potential molecular mechanism underlying spaced learning involves the activation of extracellular signal-regulated kinase 1/2 (ERK1/2) in the hippocampus, ultimately inducing the synthesis of proteins at neural marking sites (‘behavioural tagging’ hypothesis) [2]. Despite the initial description of spaced learning dating back to 1885, and its longstanding significance in the literature on educational psychology, its application in the field of medical education has gained attention only in the past decade [3].

Currently, spaced learning has been implemented in various forms in medical education, including online teaching, traditional classroom lectures, and simulation-based training for interns’ skill development. In a study involving clinical interns in medical schools, the ­delivery of educational emails on urology topics in a spaced manner yielded significantly higher scores on relevant year-end exams among students who received the emails than among their peers [4]. Another study focusing on orthopaedic residents ­preparing for a foundational science examination was found that residents who employed spaced learning techniques achieved better performance on the exam [5]. There have indeed been studies investigating the benefits of spaced learning in various domains, including radiology education, resuscitation training, psychiatric learning, dental education, and even preliminary surgical procedural training, such as the performance of surgeons’ square knots under laparoscopy [6–11]. However, prior research on the implementation of spaced learning in surgical training has focused ­primarily on medical students without surgical experience. The effectiveness of spaced learning in more advanced and specialized skill acquisition, such as cosmetic suturing skills, remains uncertain and subject to scrutiny.

In the face of patients’ increasing demands for an elevated quality of life, there is a growing necessity to extend the application of cosmetic suturing skills beyond purely cosmetic surgical procedures, particularly within domains such as breast and thyroid surgery. Spaced learning holds the potential to enhance the proficiency and durability of these skills among surgical residents. The main objective of this study was to evaluate whether, in comparison to concentrated learning, spaced learning improves the short-term acquisition and long-term retention of cosmetic suturing skills as outcomes of surgical resident training courses.

Materials and methods

This randomized controlled trial aimed to assess the short-term acquisition and long-term retention effects of spaced learning on cosmetic suturing skill training for surgical residents. The study was conducted from February 2023 to June 2023 and recruited surgical residents from a teaching hospital and its affiliated branch in Guangzhou, China, as part of an institutional quality improvement education initiative. This study was solely educational, and consultation was made with the Research Ethics Committee of Guangdong General Hospital, Guangdong Academy of Medical Sciences. They concluded that the study did not require ethical approval.

Study design and setting

Participants were randomly assigned at a 1:1 ratio (with a block size of 4) to two training groups: the experimental group, which received spaced training, and the control group, which underwent concentrated training. The training and testing procedures are illustrated in Figure 1. In the spaced training group, participants engaged in 40 min of training followed by a 20-minute rest period. During the rest interval, standardized physical activities such as outdoor brisk walking or jogging were performed, and this cycle was repeated three times. In the concentrated training group, participants underwent a continuous training session of three hours without any breaks or interruptions.

Figure 1. Study design. The surgical cosmetic suturing skills of each participant were evaluated before training (pretraining test), within one hour after training (posttraining test), and three months after the end of training (follow-up test).

Two groups of participants received one-on-one training from instructional teachers in the simulated operating rooms of the teaching hospital. The training focused on performing buried vertical mattress sutures via the use of 4-0 absorbable sutures on silicone models that simulate four types of incisions (Figure 2). Three teachers underwent previous training in the standardized Peyton’s 4-step teaching approach [12], which included the following steps: (1) ‘demonstration’, in which teachers demonstrated the suturing procedure at a normal pace without any annotations; (2) ‘deconstruction’, in which teachers repeated the process while providing detailed explanations of all necessary steps; (3) ‘comprehension’, in which students completed and explained each step under the guidance of the teachers; and (4) ‘performance’, in which students independently completed the entire task. Subsequently, participants were given additional training time to practice the procedure further and continued practicing the programme during the remaining training time. The three teachers rotated every hour.

Figure 2. Training and testing involved the use of buried vertical mattress sutures on silicone models that simulate four types of incisions via 4-0 absorbable sutures. (A) Silicone model used for test technique training; (B) four types of skin incisions; (C) (D) a buried vertical mattress suture. The suture starts at point a, passes through points b and c, and exits at point d. Then, the suture repeats symmetrically on the opposite side, entering and exiting the points accordingly.

To limit confounding factors, the use of smartphones was prohibited.

Participants

Recruitment was conducted via email. First-year surgical residents undergoing surgical training were eligible to participate in this study, and their surgical training plans within three months after the experiment were consistent. Resident physicians who had received any training in cosmetic suturing skills were excluded from the study. Prior to random assignment, written informed consent was obtained from each surgical resident participating in the study.

Conceptual framework

In the spaced training group, the timing of the three spaced training cycles was designed to leverage the educational benefits of the spacing effect. The use of ‘spaced training’ allows for lasting improvements in knowledge acquisition and retention based on the core principles of psychology and Hermann Ebbinghaus’s ‘forgetfulness curve’ theory [1, 13]. The effectiveness of spaced learning durations follows a pattern where test performance improves as the spacing interval increases from zero, reaches an optimal value, and then declines when the spacing interval exceeds that optimal value [13]. While there is currently no consensus on the exact optimal spacing interval, it is influenced by the nature of the material being learned. Psychological and neuroscientific research findings on memory formation mechanisms indicate that spaced learning is also effective with shorter spacing intervals [2]. Thus, the design of the ‘spaced training’ in this study accounted for previous research [10,11] and considered practical feasibility.

Measurement tool

The primary outcome measures utilized an objective scoring scale (see Supplementary Table 1). The objective scoring scale was derived from the standardized training and assessment criteria for resident physicians in China based on the quantifiable 5-point scale design proposed by Muresan et al. [14]. The scoring criteria for evaluating the participants included three aspects. First, the suture quality score assessed the uniformity of suture spacing, alignment of skin edges, and strength of the suture knots. Second, the suture technique score evaluated the smoothness of stitching motions, proficiency in tying knots, fluidity of scissor cutting motions, and overall execution proficiency and fluidity. Finally, the suturing time score measured the participants’ ability to complete the suturing procedure within the specified timeframe.

Data collection

To assess the short-term and long-term effects of training, each participant was scored for cosmetic suturing skills before training (pretraining test), within one hour after training (post-training test), and three months after the end of training (follow-up test) (Figure 1). Before each test evaluation, all participants received a standardized explanation of their tasks and watched a short instructional video. During the test, participants were asked to perform buried vertical mattress sutures using 4-0 absorbable sutures on silicone models that simulated four types of incisions within 60 min (Figure 2), and the operation video was recorded by a head-mounted surgical video recorder.

Each participant’s operation video was assigned a unique identifier, and three surgeons with titles of attending physician or higher independently rated each video. The group corresponding to each video identifier was blinded to the raters. The raters evaluated the content of each video based on an objective scoring scale, providing item-by-item ratings and calculating the total score (see Supplementary Table 1).

Data analysis

The lack of data on spaced training in cosmetic suturing skills training hinders the formal calculation of sample size. The sample size was estimated based on the complexity of the intervention and previous research results from similar settings [10].

The measurement data are presented as the mean, standard deviation, median, maximum, and minimum values. Count data are summarized as the frequency and percentage. The statistical analysis, including normal distribution and t-test, was performed by the statistical analysis program R (version 3.5.3). The Mann–Whitney U-test was used when the data were not normally distributed or the variance was uneven. Pearson’s test was used for correlation analysis between parameters, and statistical analysis was performed using the chi-square test or Fisher’s exact test.

Interrater reliability, defined as the degree of agreement among two or more evaluators, serves as a measure of the consistency in the implementation of a scoring methodology. The intraclass correlation coefficient (ICC) was utilized to evaluate interrater reliability in this study.

Results

To assess the short-term and long-term effects of training, each participant was scored for cosmetic suturing skills before training (pretraining test), within one hour after training (post-training test), and three months after the end of training (follow-up test). A total of 23 (numbered 1-23) surgical residents participated in this study; 65.2% (15) were male surgeons, and 34.8% (8) were female surgeons. After random assignment, 12 surgeons were assigned to the spaced training group, and the other 11 were assigned to the concentrated training group. No participant was excluded before or after allocation to a group or lost to follow-up. There was no significant difference in the distribution of sex or age between the two groups of participants (Table 1).

Table 1. Comparison of baseline characteristics and pretraining, post-training and follow-up test scores between the two training groups.

 	Spaced Training Group (n = 12)	Concentrated Training Group (n = 11)	P *	
Gender	 	 	 	
 Male	8 (66.67%)	7 (63.64%)	1.0000	
 Female	4 (33.33%)	4 (36.36%)	 	
 Age (year)	24.33 ± 2.31	23.55 ± 0.69	0.6548	
Pretraining Test	 	 	 	
 Total score	39.18 ± 8.04	40.81 ± 9.23	0.6610	
 Suture Quality Scoring	16.76 ± 5.12	16.96 ± 8.02	0.9421	
 Suture Technique Scoring	15.01 ± 3.63	14.57 ± 4.51	0.8013	
 Suturing Time Score	7.42 ± 6.47	9.27 ± 7.03	0.5242	
Posttraining Test	 	 	 	
 Total score	74.06 ± 5.87	63.43 ± 10.73	0.0070	
 Suture Quality Scoring	32.68 ± 5.01	28.49 ± 6.46	0.0951	
 Suture Technique Scoring	28.46 ± 1.78	22.85 ± 3.75	0.0002	
 Suturing Time Score	12.91 ± 4.98	12.09 ± 6.01	0.5793	
Follow-up Test	 	 	 	
 Total score	75.60 ± 4.78	60.68 ± 10.40	0.0001	
 Suture Quality Scoring	32.26 ± 4.01	26.23 ± 4.16	0.0019	
 Suture Technique Scoring	28.68 ± 2.63	22.18 ± 3.94	0.0001	
 Suturing Time Score	14.67 ± 1.15	12.27 ± 6.07	0.0460	
* Statistical analysis, including normal distribution and t-test, was performed by the statistical analysis program R (version 3.5.3). The Mann–Whitney U-test was used when the data were not normally distributed or the variance was uneven. Bold indicates statistical significance.

The inter-rater reliability

The ICC for interrater reliability was found to be 0.990 (95%CI: 0.980–0.995), 0.990 (95%CI: 0.980–0.995), and 0.991 (95%CI: 0.981–0.996) for the pre-training test, post-training test, and follow-up test, respectively.

Pre-training test

In the pre-training test of the spaced training group and concentrated training group participants, t-tests were used. The results showed that the total test scores were 39.18 ± 8.04 and 40.81 ± 9.23, respectively, with no significant difference (p = 0.6610). Additionally, there was no significant difference between the two groups in terms of the pretraining suture quality scores, suture technique scores, or suturing time scores (Table 1).

Post-training test

In the post-training test, the total score of the spaced training group was significantly higher than that of the concentrated training group (74.06 ± 5.87 vs. 63.43 ± 10.73, p = 0.0070), with suture technique scores of 28.46 ± 1.78 and 22.85 ± 3.75, respectively (p = 0.0002). The suture quality score and suturing time score of the spaced training group were both significantly higher than those of the control group (Table 1).

Follow-up test

According to the long-term follow-up test, the spaced training group had significantly higher test total scores, suture quality scores, suture technique scores, and suturing time scores than the concentrated training group (75.60 ± 4.78 vs. 60.68 ± 10.40, p = 0.0001; 32.26 ± 4.01 vs. 26.23 ± 4.16, p = 0.0019; 28.68 ± 2.63 vs. 22.18 ± 3.94, p = 0.0001; 14.67 ± 1.15 vs. 12.27 ± 6.07, p = 0.0460) (Table 1).

Figure 3 shows the trend of average scores of the two training groups and at the three testing time points for each scoring item and suturing time. The spaced training group demonstrated varying degrees of improvement in each scoring item compared to the concentrated training group, and this advantage was sustained even after 3 months.

Figure 3. Trends of the average scores of the two training groups and at the three testing time points for each scoring item and suturing time (±standard deviation). (A) even needle distance; (B) Skin edge alignment; (C) Tight suturing; (D) Knotting method; (E) Suturing method; (F) Cutting line; (G) Smoothness of movement; (H) Suturing time.

Overall, the results of the posttraining and follow-up tests revealed that the spaced training group performed better than the concentrated training group, with significantly higher total test and suture technique scores. These findings indicate that spaced training can lead to improved cosmetic suturing skills, and this advantage is sustained over a longer period.

Discussion

Attaining a proficient level in surgical procedures requires extensive and prolonged training to acquire the necessary cognitive and technical abilities. Our research findings are directly relevant to the training of surgeons. This study reveals that spaced learning significantly enhances the proficiency of surgical residents in terms of suturing quality, surgical technique, and suturing speed in cosmetic suturing training. Moreover, these skills may have long-term sustained benefits.

Short-term skill enhancement

The post-training test results demonstrated an overall improvement in performance in both groups. However, during this period, the spaced training group exhibited more significant improvement than the concentrated training group. Our results are supported by previous findings.

Historically, most medical education studies that have utilized spaced learning have employed online teaching methods, where information or questions are distributed through email on a daily, every other day, or weekly basis [15–17]. These studies have demonstrated that spaced repetition not only enhances memory retention at the level of learning theoretical knowledge but also improves learning efficiency.

While previous research has strongly supported the utility of spaced learning in enhancing memory, there has also been an increasing body of evidence indicating its potential applications beyond memory improvement. Boettcher et al. evaluated the effectiveness of spaced learning by assessing medical students’ acquisition of laparoscopic suturing and knot tying skills [10]. The results revealed that students trained through spaced learning demonstrated superior performance in terms of suturing technique, knot quality, and suture strength. However, this study did not investigate the long-term retention of acquired skills.

Long-term retention of acquired skills

During the three-month follow-up period, the surgical residents were involved in other surgical procedures and training but did not have further practice with or exposure to cosmetic suturing techniques. During long-term follow-up, the surgical residents who underwent spaced training maintained a consistent level of proficiency in suturing quality, surgical technique, and suturing speed skills, while the concentrated training group showed varying degrees of decline in these scores.

The long-term retention and recall of information pose greater challenges than short-term acquisition. German psychologist Hermann Ebbinghaus studied the ‘forgetfulness curve’, which graphically represents the exponential decay of information retention over time [1]. Despite Ebbinghaus’s occurring more than a century ago, in 2015, a group of researchers conducted a similar experiment and arrived at similar findings [18]. According to Ebbinghaus’s research, the most significant decline in information retention occurs shortly after the introduction of new information. In other words, data acquired during a lecture, for example, tend to fade within a few hours or days after leaving the classroom. Ebbinghaus also proposed a potential approach to counteract forgetting. His studies suggested that by relearning new information at specific intervals on the forgetting curve, learners can slow its rapid decay. Through several appropriately timed review sessions, nearly all the information being learned can be retained in the long term.

This conclusion has also been demonstrated in previous research related to medical education [14]. A study investigated the impact of spaced learning on online urological surgical education and found that the effects of spaced learning can persist for up to two years.

Theories about the mechanism

There are three theories about the mechanism through which spaced learning is beneficial for clinical skill learning and sustained mastery. First, the processing defect hypothesis is one of the most intuitive explanations for the spacing effect and is widely accepted. This hypothesis states that, compared with spaced presentations of learning content, massed presentations cause less brain processing in learners, so memory is worse; whether learners control their attention on the content they are learning, spaced learning increases their brain processing volume, thus having a positive impact on skill acquisition [19]. The second explanation is the neuroscientific mechanism of spaced learning; that is, spaced learning improves long-term memory by increasing the extraction and enhancing the recovery of previous neural representations [20]. Feng K et al. found that after performing electroencephalogram data analysis based on spatiotemporal pattern similarity (STPS), the more specific STPS that appeared in the right prefrontal cortex after the stimulus started at 543-727 ms, the better the learners’ memory performance; additionally, this STPS was more obvious in spaced learning than in concentrated learning [20]. Spaced learning enhances subsequent recognition memory by reducing neural repetition suppression [21]. The third explanation is the metacognitive mechanism. Metacognition, as proposed by the American psychologist Flavell J H, is cognition about cognition. Metacognitive theory can also explain the cognitive bias that appears in spaced learning. To solve this problem, Vlach et al. redefined the relationship between metacognition and spaced learning [22]. The study found that adults believe that concentrated learning is better than spaced learning because there is a concentrated learning bias; children do not initially have a concentrated learning bias, so the bias found in spaced learning research on children is less than that in research on adults.

Limitations

Our study has several limitations. Participants received training in simulated operating rooms, which limits the assessment of the transferability of the skills to real-life contexts. Various other domains, such as decision-making abilities, teamwork, understanding of anatomy, and other surgical procedural skills, were not evaluated. The sample was small, which may have reduced the statistical power to detect smaller differences between the two groups. The long-term outcomes were assessed at a follow-up period of three months after the completion of the training program, and it is unclear whether the retention of cosmetic suturing skills can be maintained over a longer period. Finally, while this study and previous research indicate that spaced learning is effective even with shorter intervals, further investigation is still needed to explore the optimal spacing duration.

In summary, our research demonstrates that spaced learning significantly improves the proficiency of surgical residents in cosmetic suturing training. The short-term results show that the spaced training group exhibited greater improvement than the concentrated training group. Previous studies have also supported the benefits of spaced learning in medical education. Moreover, our study indicates that the skills acquired through spaced training can be maintained in the long term, and the concentrated training group showed a decline in proficiency over time. Theories suggesting the mechanisms behind spaced learning include processing defects, neuroscientific mechanisms, and metacognitive processes. Further research is necessary to assess the transferability of skills to real-life contexts and determine the optimal spacing duration for effective learning.

Conclusion

Incorporating the principles of spaced learning into the instructional process of cosmetic suture skills for surgical residents not only significantly enhances short-term skill improvement but also contributes to the long-term retention of training outcomes. This study not only fills the gap in the application of spaced learning in the training of surgical residents on cosmetic suture skills but also could extend the concept of spaced learning to other projects and domains within surgical skills training. Therefore, we propose the inclusion of the concept of spaced learning in residency training programs and surgical training courses.

Supplementary Material

Supplemental Material

Authors’ contributions

Liulu Zhang is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Xinjian Yan was supported by the research fund. Xinjian Yan and Liulu Zhang devised and designed the study. All subjects were recruited by Adilijiang.Abudouresuli and Abudukeremu.Yuemaier. Yan Ge performed the statistical analysis. Shiyao Shang and Jue Yang carried out the literature search and data collection. Xinjian Yan and Liulu Zhang wrote this paper. The paper was revised and edited by Adilijiang.Abudouresuli, Abudukeremu.Yuemaier, Yan Ge, Shiyao Shang, Jue Yang.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data sharing

The datasets analysed during the current study are available from the corresponding author on reasonable request.
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