Laparoscopy has replaced laparotomy in most gynaecological procedures, and laparoscopic cystectomy is currently the mainstay of treatment for apparently benign ovarian cysts. However, the absence of depth perception and limited instrument dexterity are major drawbacks of laparoscopy. Advances in three-dimensional (3D) video imaging technology allow 3D laparoscopy to provide better precision than conventional two-dimensional (2D) laparoscopy, especially in depth perception and spatial orientation. This increased precision may help improve surgeon’s performance during laparoscopic surgery.

Studies have shown that 3D laparoscopy objectively1 2 and subjectively3 4 improves surgical performance, especially during complex tasks.5 In addition, 3D laparoscopy lessens the learning curve for beginners.6 The durations of laparoscopic cholecystectomy and pelvic lymphadenectomy have also been shortened when performed using 3D technologies.7 8 However, the clinical value of 3D laparoscopy in benign gynaecological surgery remains uncertain. This study aimed to evaluate any advantages of using 3D laparoscopy over 2D laparoscopy for ovarian cystectomy.

This prospective randomised study was conducted from May 2014 to May 2016 at the Queen Mary Hospital, Hong Kong, a teaching hospital affiliated with The University of Hong Kong. Women with apparently benign ovarian cysts who were scheduled for elective laparoscopic ovarian cystectomy and who were eligible for the study were invited at the pre-admission clinic to enrol in the study. Inclusion criteria were being older than 18 years; ability to understand Cantonese, Putonghua, or English; and ability to understand the study information during the consent process. Patients who were intra-operatively found to have no ovarian cyst were excluded from further analysis.

Patients were allocated by block randomisation to undergo surgery with 2D laparoscopy (2D group) or 3D laparoscopy (3D group) according to a computer-generated random sequence, in blocks of five. The group allocation for each patient was disclosed to the surgeon on the day before the surgery using a consecutively numbered, opaque, sealed envelope. Demographic data of patients and duration of surgeries were collected by a research nurse.

A pneumoperitoneum was created using a Veress needle to provide visually guided closed access. For 3D laparoscopy, a 10-mm 3D telescopic videoscope was used (Endoeye Flex 3D; Olympus, Center Valley [PA], US). All surgeons were trained for 3D laparoscopy using a pelvic trainer with standardised tasks including peg transfer, precision cutting, duct cannulation, and suturing with knot tying. The 3D laparoscopy training was continued until the surgeons could confidently operate using 3D images. All non-specialist surgeons were supervised by a laparoscopist accredited at the advanced level in gynaecological laparoscopic surgery, according to the Hong Kong College of Obstetricians and Gynaecologists.9 At their discretion, surgeons were allowed to switch from 3D laparoscopy to traditional 2D laparoscopy if difficulty was encountered during surgery. All 2D laparoscopies were performed using a 10-mm laparoscope (26033AP; Karl Storz Endoscopy-America Inc, Culver City [CA], US). The same 32-inch high-definition monitor (LMD-3215MT; Sony Corporation, Tokyo, Japan) was used for all operations. In the 2D and 3D groups, cystectomy was performed in the usual manner, using two or three 5-mm accessory ports inserted in the lower abdomen under direct vision. The start time of the operation (first skin incision), insertion of primary trocar, completion of cystectomy, and end of operation (final skin closure) were recorded by the research nurse.

After the operation, all surgeons were required to self-evaluate their performance by using the Global Operative Assessment of Laparoscopic Skills (GOALS) assessment tool.10 The five-item GOALS score includes assessment of depth perception, bimanual dexterity, efficiency, tissue handling, and autonomy. Any operator discomfort encountered during the surgery, any need to convert to 2D laparoscopy, and the surgeon’s preference for the type of laparoscopy based on experience were also recorded. Demographic data and operative findings, such as size and laterality of cysts, operative duration, and presence of adhesions were analysed. Duration of cystectomy was defined as the time from completion of primary port insertion to separation of the cyst from the ovary and completion of haemostasis. The time spent on specimen retrieval was not included, owing to variations in the specimen retrieval method with or without use of a specimen bag.

The primary outcome of the present study was the difference between the GOALS score of 2D and 3D groups. The secondary outcomes were the duration of cystectomy and surgeon’s preferences and reported adverse effects. Subgroup analysis was performed to compare the outcomes for different experience levels among the surgeons. The surgeons were categorised according to their experience in performing laparoscopic surgery (≤5 years or >5 years). Surgeons with more than 5 years of experience had achieved competency in gynaecological laparoscopic surgery to at least an intermediate level, according to the Hong Kong College of Obstetricians and Gynaecologists, and had completed a required number of laparoscopic operations as requested by the College.9

A sample size of 36 patients was required in each group, as calculated using an alpha of 0.05 and a beta of 0.2 for detection of a difference in the sum of four items of the GOALS score (excluding tissue handling) of 13 (interquartile range [IQR], 11-16) in the 2D group and 16 (IQR, 12-18) in the 3D group, as based on a previous study,11 using a two-sided test. To allow for a 10% dropout rate, 40 patients were recruited into each group. For randomised patients whose operations were subsequently rescheduled outside the study period, treatment assignment numbers were reallocated to subsequent eligible patients who provided consent. Statistical analysis was performed using SPSS Windows version 21.0 (IBM Corp, Armonk [NY], US). Data were presented as proportions or mean and standard deviation. Student’s t test and Chi squared test were used for statistical analyses. A P value of <0.05 was considered statistically significant.

Of the 83 patients recruited into the study from May 2014 to May 2016, operations were rescheduled for three patients who were therefore withdrawn from the study; 80 patients completed the trial (Fig). Of these 80 patients, two from the 2D group and three from the 3D group were excluded from analysis because no cysts were identified. Finally, 38 patients in the 2D group and 37 patients in the 3D group were included for analysis. Patient characteristics and surgical outcomes are presented in Table 1. There were no significant differences between the 2D and 3D groups in terms of patient age, laterality of the ovarian cyst, histological diagnosis of the cyst, presence of severe adhesions, volume of blood loss, and experience level of the surgeon. Three accessory ports were used in four patients in the 2D group and in five patients in the 3D group. In all other patients, two accessory ports were used. The mean (standard deviation) diameter of the ovarian cyst was smaller in the 3D group than that in the 2D group (5.1 [2.1] cm vs 6.1 cm [2.1] cm; P=0.031). Body mass index in the 2D group was significantly higher than that in the 3D group (23.4 [4.4] kg/m² vs 21.3 [2.6] kg/m²; P=0.011). Severe adhesion was defined as a score of >20 for adnexal adhesion unilaterally12 or a score of >40 for endometriosis,13 according to the American Society for Reproductive Medicine classifications.

The differences between 2D and 3D groups in terms of GOALS score and duration of cystectomy are presented in Table 2. A total of 15 surgeons participated in the study and there were 13 in each group: 11 in both, while two for each were involved in 2D and 3D groups, respectively. Participating surgeons in the 2D group reported more efficient tissue handling than did those in the 3D group. Adverse effects, including nausea, dizziness, ocular fatigue, and blurring of vision were reported less frequently by participating surgeons in 2D group than those in 3D group (Table 3). However, none of the participating surgeons requested intra-operative conversion from 3D to 2D laparoscopy. At the end of surgery, more participating surgeons in the 3D group expressed a preference for 2D laparoscopy (43.3%) than for 3D laparoscopy (18.9%), whereas 37.8% had no preference. A subgroup analysis of participating surgeons in the two groups did not show statistically significant differences in terms of GOALS score (2D vs 3D; 28.9 [5.1] vs 28.2 [46.0]; P=0.585), tissue handling (4.2 [0.8] vs 3.9 [0.8]; P=0.060), and duration of cystectomy (93.7 [46.1] min vs 97.7 [52.2] min; P=0.737).

Subgroup analyses according to the experience level of the surgeon and the presence of dense adhesions are shown in Tables 4 and 5, respectively. Two of the surgeons in the 3D group and three of the surgeons in the 2D laparoscopy are accredited at the advanced level in gynaecological laparoscopic surgery by the Hong Kong College of Obstetricians and Gynaecologists. Surgeons with more than 5 years of laparoscopic experience reported lower scores in tissue handling and efficiency when using 3D laparoscopy. There were no differences in terms of GOALS score and duration of cystectomy in the subgroup with dense adhesions.

Three-dimensional laparoscopy is gaining popularity in modern gynaecological surgery owing to improved depth perception and spatial orientation compared with 2D laparoscopy. Improved effectiveness using 3D laparoscopy has been shown extensively in training models, especially when performing complex tasks5 and in beginners.6 8 14 However, our study was unable to show an improvement in terms of GOALS score and duration of operation (Table 2) despite the 3D laparoscopy group having a smaller mean ovarian cyst diameter (Table 1). This finding contradicts a recent meta-analysis that 3D laparoscopy was associated with shortened surgical time and hospital study, less blood loss, and fewer perioperative complications.15

The addition of binocular vision and depth perception in 3D laparoscopy is associated with more frequent adverse effects such as ocular fatigue, nausea, and dizziness.16 In the present study, participating surgeons in the 3D group more frequently reported nausea, dizziness, ocular fatigue, and blurring of vision than did those in the 2D group. However, this result may be because the participating surgeons were unfamiliar with 3D images; with experience, this discomfort may be lessened. Maintaining stability of the telescope is of utmost importance during 3D laparoscopy; therefore, familiarity with 3D images is important for assistants to mitigate adverse effects. Furthermore, maintaining an appropriate distance between the screen and the surgeon also alleviates nausea and ocular fatigue.16

Previous studies have shown that 3D laparoscopy is beneficial for less experienced surgeons6 8 14 and for any surgeon performing complex tasks.5 However, in our subgroup analysis, we were unable to confirm any benefits of 3D laparoscopy in relation to the experience level of the surgeons. All participating surgeons were much more familiar with 2D laparoscopy and, thus, the difference between groups might simply reflect the surgeon’s assessment of what they are used to. This familiarity effect may explain the lower scores in tissue handling and efficiency with 3D laparoscopy attained by the more experienced surgeons.

The surgeon’s preference for 2D laparoscopy and the heterogeneity of the participating surgeons and patients make the subgroup analyses underpowered and represents a constitute limitation of the present study. The differences in mean diameter of the ovarian cysts and body mass index between the two groups also suggest ineffective randomisation. Other limitations include ineffective randomisation, withdrawal of patients after randomisation, and surgeon’s lack of experience with 3D laparoscopy. During data analysis, there were also no controls for possible confounding factors, such as experience of each surgeon with 3D laparoscopy or significant differences in patient characteristics between the groups.

In conclusion, the results show that there is no significant benefit to using 3D laparoscopy for ovarian cystectomy compared with conventional 2D laparoscopy. Moreover, 3D laparoscopy is associated with more frequent adverse effects for surgeons. However, it is possible that more complex procedures, such as those involving laparoscopic suturing and knot tying, might be easier to perform with 3D laparoscopy than with 2D laparoscopy. Therefore, further evaluation of the clinical performance of 3D laparoscopy in operations of different complexities and of surgeons with different experience levels are warranted.

All authors have made substantial contributions to the concept of this study; acquisition of data; analysis or interpretation of data; drafting of the article; and critical revision for important intellectual content.

We wish to thank Ms Wai-ki Choi for helping in patient recruitment and data collection.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

The authors have no conflicts of interest to disclose. All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity. The study was presented as oral presentation in the 25th Asian and Oceanic Congress of Obstetrics and Gynaecology, 16 June 2017, Hong Kong.

Ethical approval was obtained from the Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster. Written informed consent was obtained from all participating patients and surgeons. The study was registered with ClinicalTrials.gov (NCT02775344).

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