Hysteroscopy in daily practice
Dongen, H. van
Citation
Dongen, H. van. (2009, February 26). Hysteroscopy in daily practice.
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Chapter 4
Hysteroscopic morcellator for removal of intrauterine polyps and myomas:
a randomised controlled study among residents in training
Heleen van Dongen Mark Hans Emanuel Ron Wolterbeek J. Baptist M.Z. Trimbos Frank Willem Jansen Adapted from J Minim Invasive Gynecol 2008;15:466-471
Chapter 4 30
Introduction
Since the 1970s, operative hysteroscopy has been adopted as a surgical proce- dure mainly in order to treat intrauterine pathology. The preferred technique for the removal of intrauterine abnormalities, such as endometrial polyps or submucous myo- mas, became resectoscopy with a monopolar high frequency electrical current. This technique can only be performed with a non-conducting, electrolyte-free fluid to irri- gate and distend the uterine cavity. Although this treatment has rendered good results [Emanuel 1999], an excessive intravasation of distension fluid can be life-threatening [Vulgaropulos 1992]. A meticulous monitoring of fluid balance is therefore necessary to prevent a fluid overload. In case of an imminent fluid overload it is recommended that the procedure be aborted. Since the introduction of bipolar resection techniques that use normal saline, the risk of fluid overload has become a less important limiting factor during hysteroscopic removal [Kung 1999]. Recently, the hysteroscopic morcella- tor, a new technique designed for this purpose, was introduced and uses normal saline as irrigation fluid as well. Another advantage of the morcellator technique is that tissue fragments can be removed easily by means of suction through the instrument, and are thereafter still available for histological analysis. A previously published study showed that this method reduces the operating time significantly [Emanuel 2005]. Since acquir- ing skills at hysteroscopic resectoscopy is time-consuming, it has been suggested that the hysteroscopic morcellator for the treatment of intrauterine abnormalities may be easier to master than conventional resectoscopy [Emanuel 2005]. Therefore, the aim of this study was to compare the standard conventional electrosurgical resection technique with the hysteroscopic morcellator performed by residents in training to estimate the learning curve associated with both techniques.
Methods
This study was conducted from January 2005 until April 2006 at a university-affiliated teaching hospital (Spaarne Hospital, Heemstede/Hoofddorp, The Netherlands) and a university hospital (Leiden University Medical Center, Leiden, The Netherlands). Patients were eligible to participate if they were diagnosed preoperatively with an intrauterine polyp or a type 0 or type I submucous myoma smaller than 30mm diameter and if there was an indication for removal, irrespective of age, parity, menopausal or general health state. Diagnosis was made by transvaginal ultrasound and/or saline infusion sonography.
Exclusion criteria were type II myomas (see chapter 2 for the classification of submu- cous myomas), suspicion of malignancy or contra-indications for hysteroscopic surgery.
Ethical approval for this study was obtained from the Leiden University Medical Center Ethics Committee and the local medical ethic committee of the Spaarne Hospital.
Patients gave written consent.
We were interested in the learning curve of hysteroscopic removal by the resectoscope and the hysteroscopic morcellator. Since there were no previous data available on this
issue, no power calculation could be performed. For this reason the group size for this pilot study was set at 2x30 patients. According to a randomly permuted block design sequences of ten procedures for six residents in training were created by random per- mutation tables. The purpose of this assignment of treatments was to ensure a random order of the two procedures and to ensure that each intervention was applied by each surgeon an equal number of times [Cox 1958]. The sequence was concealed with a series of sealed opaque envelopes. Randomisation envelopes were drawn just prior to the scheduled procedure. Two study groups of equal size were generated: (A) conven- tional resectoscope, (B) hysteroscopic morcellator.
Hysteroscopic removal was performed by six residents in training for obstetrics & gyn- aecology. Though each of them had experience in the operating theatre, they had only limited experience with hysteroscopy. All procedures were supervised by experienced hysteroscopists (MHE and FWJ) and performed in an inpatient setting under general or spinal anaesthesia.
The hysteroscopic removal of intrauterine disorders among patients allocated to conven- tional resectoscopy (group A), was performed with a rigid 9mm resectoscope (Olympus Winter&Ibe, Hamburg, Germany) equipped with a 12º optic. Sorbitol (5%) was used for distension and irrigation of the uterine cavity. The fluid balance was closely monitored.
Further details have been previously described [Corson 1991; Wamsteker 1993b].
The hysteroscopic removal in group B was performed with a hysteroscopic morcellator (Smith&Nephew, Andover MASS, USA). This instrument consists of a rigid inner tube, that rotates within an outer tube (diameter 4.5mm). Both tubes have a window-opening at the end with cutting edges. A vacuum connected to the inner tube sucks the tissue into the window opening and cuts it as the inner tube rotates. This tissue is discharged through the device and collected in a pouch, so that it is available for histopathological analysis. The hysteroscopic morcellator is introduced into the uterine cavity through the working channel of a continuous flow 9mm rigid endoscope (Smith&Nephew, Andover MASS, USA). For the latter procedure, normal saline was used for distension and irriga- tion of the uterine cavity. Again, the fluid balance was closely monitored. Further details of this technique have been previously described [Emanuel 2005].
Trainers were requested to take control of the procedure, if intravasation exceeded 500ml without sufficient progression of the removal, in order to avoid incomplete removal or fluid overload.
The primary outcome measure was the operating time, defined as the time between the introduction of the hysteroscope until the removal of the instrument at the end of the procedure. A comparison of operating times was used to investigate the learning curve differences. Secondary outcome measures were the amount of distension medium used, the amount of fluid deficit, the number of insertions of the instrument, whether the trainer had to take over before the procedure was completed, and subjective scores
Chapter 4 32
regarding the use of the instrument by both the surgeon (resident in training) and the trainer on a visual analogue scale (VAS; range 0=poor, 10=very comfortable). The failure of the procedure by means of conversion to other techniques, incomplete removal, and complications was determined as well.
Study outcomes were evaluated based on the intention-to-treat principle. The results were collected in the statistical SPSS-program (SPSS, version 12, SPSS Inc., Chicago, IL).
Data were analysed with the Student’s t-test and the ANCOVA (analysis of co-variance) test for normally distributed continuous variables, the Mann-Whitney U-test for skewed data and the Pearson’s Chi-square test to compare dichotomous data. Confidence inter- vals (95%-CI) and standard deviations (SD) of the mean were calculated for normally distributed continuous variables. Residual plots were used to evaluate normality. If continuous variables were not normally distributed, the median and range were given.
Categorical data were presented as frequency and percentage. Since the operating time could be influenced by the size of the lesion to be removed, a multiple linear regres- sion analysis was performed with the volume of the intrauterine abnormality and the technique as predicting variables to determine whether operating time varied between both techniques. The volume of the intrauterine abnormality was estimated according to the following formula 4/3πr3 (volume of sphere, r=radius). The radius was derived from the diameter of the intrauterine abnormality measured by ultrasound. Likewise, multiple linear regression analysis was also used to estimate the relationship between the total amount of distension medium and the amount of fluid deficit of both techniques and the operating time. To determine whether a learning curve was present, multiple linear regression was performed with operating time set as the outcome, and surgeon, trainer, volume of the lesion, and the sequence of the procedures set as predicting variables. The model assumptions were checked by plotting unstandardised residuals against predicted values, eyeballing histograms of residuals and assessing homogeneity of variances with the Levene’s test [Levene 1960].
Results
Of the 74 patients approached, fourteen patients were excluded due to several rea- sons (figure 1). Eight patients did not meet the inclusion criteria; of these five patients appeared not to have an intracavitary lesion and three had an intracavitary submucous myoma with an intramural extension of more than 50% (type II myoma). Six patients refused to participate.
The patients’ characteristics of the randomised groups are featured in table 1. There were no significant differences between both groups. The mean age of residents participating in the study was 33.7 years (SD 4.0; 95%-CI 30.7-36.7), four of them were female and two were male. Two residents had performed less than twenty hysteroscopic procedures
before participating in this study, and the other four residents less than ten procedures.
Although there was no stratification by type of lesion (myoma or polyp) at randomisa- tion, the number of polypectomies and myomectomies performed by each surgeon did not differ (χ2: p=0.431). Surgery characteristics are detailed in table 2. The mean operat- ing times for conventional resectoscopy and hysteroscopic morcellator were 17.0 min (SD 8.4; 95%-CI 14.1-19.9) and 10.6 min (SD 9.5; 95%-CI 7.3-14.0) respectively (95%- CI for the difference 1.8-10.9; p=0.008). Multiple linear regression analysis showed that operating time was increased significantly, irrespective of technique, as the volume of the intrauterine disorder increased. Use of the morcellator instead of the conventional Figure 1 | Consort diagram depicting the outcome of patients recruited for the study.
Assessed for eligibility (n=74)
Excluded (n=14)
• Not meeting inclusion criteria (n=8)
• Refused to participate (n=6)
Randomised (n=60)
Allocated to conventional resectoscope (n=30)
• Received allocated intervention (n=29)
• Did not receive allocated intervention (n=1)
Allocated to hysteroscopic morcellator (n=30)
• Received allocated intervention (n=30)
Analysed (n=29) Excluded from analysis (n=1)
Analysed (n=30)
A B
Chapter 4 34
Table 1 | Patient characteristics of randomised groups: conventional resectoscope and hysteroscopic morcellator.
Resectoscope (n=30)
Morcellator
(n=30) p-value
Mean age in years (SD; 95%-CI)
48.2 (12.4; 43.8-52.6)
49.0
(10.9; 45.1-52.9) 0.775a
Median parity (range) 2 (0-4) 2 (0-5) 0.057b
Menopausal state 1.000c
Premenopausal 22 (73%) 21 (73%)
Postmenopausal 8 (27%) 9 (27%)
Indication for surgery 0.737c
Abnormal uterine bleeding 27 (73%) 25 (83%)
Dysmenorrhoe 1 (3%) 2 (7%)
Infertility 2 (7%) 3 (10%)
Preoperative diagnosis 0.529c
Polyp 18 (60%) 20 (67%)
Myoma 12 (40%) 10 (33%)
Mean size intrauterine abnormality (SD; 95%-CI)
Diameter in mm 15.0 (6.7; 12.6-17.4) 17.7 (7.4; 15-20.4) 0.140a Volume in cm3 3.0 (4.0; 1.6-4.4) 4.7 (7.1; 2.1-7.3) 0.240a
aStudent’s t-test, bMann-Whitney U-test, cPearson’s Chi-square test
Table 2 | Outcome measures of surgery of the two randomised groups: conventional resectoscope and hysteroscopic morcellator.
Outcome measures Resectoscope Morcellator p-value
Operating time in min (SD; 95%-CI)
17.0 (8.4; 14.1-19.9)
10.6
(9.5; 7.3-14.0) 0.008a Total distension medium in ml
(SD; 95%-CI)
5050 (2594; 4106-5994)
3413
(3416; 2209-4617) 0.041a Total fluid deficit in ml
(SD; 95%-CI)
545 (382; 406-684)
409
(511; 229-589) 0.224a Median number of insertions
(range) 7 (3-50) 1 (1-2) <0.001b
Total number taken over
by trainer 5 (17%) 1 (3%) <0.001c
aStudent’s t-test, bMann-Whitney U-test, cPearson’s Chi-square test
resectoscope reduced operating time by more than eight minutes, corrected for vol- ume of the intrauterine abnormality. The coefficients and regression curves of the linear regression model of operating time in association with the volume of the intrauterine abnormality and the technique are detailed in table 3 and figure 2 respectively. For both techniques the number of procedures performed previously, and the variation in surgeons or trainers did not appear to affect the time needed for the removal of an intra- uterine abnormality (data not shown). The only predicting factor of significant influence on the operating time appeared to be the volume of the intrauterine abnormality. Also shown in table 3 are the coefficients of multiple regression analysis of the total amount of distension medium and fluid deficit with the operating time and technique as predict- ing variables. Technique neither influenced the total amount of distension fluid nor the amount of fluid deficit.
The resident and trainer scores on a visual analogue scale for both techniques are illus- trated in figures 3 and 4 respectively.
Of the 60 patients randomised, one patient, who was allocated to removal by resec- toscope, did not receive the intended procedure due to a perforation during cervical dilatation. Another patient, who was diagnosed preoperatively with a submucous type I myoma and treated with the hysteroscopic morcellator, had an incomplete resection;
Table 3 | Coefficients of multiple linear regression analysis, predicting operating time, total amount of distension fluid and amount of fluid deficit.
Operating time (min)† Coefficient* Standard error p-value
Constant 13.65 (β0) 1.203 < 0.001
Volume of lesion (X) 1.10 (β1) 0.138 < 0.001
Technique (Z) -8.23 (β2) -0.450 < 0.001
Total distension fluid (ml)‡ Coefficient* Standard error p-value
Constant -212.60 (β0) 410.062 0.606
Operating time (X) 310.19 (β1) 19.565 <0.001
Technique (Z) 326.87 (β2) 359.667 0.367
Fluid deficit (ml)§ Coefficient* Standard error p-value
Constant -91.91 (β0) 96.711 0.346
Operating time (X) 37.59 (β1) 4.614 <0.001
Technique (Z) 94.51 (β2) 0.270 0.326
*Regression coefficients assuming a generic regression model of: Y=β0+β1*X+β2*Z, where Z=0 and Z=1 represent resectoscopy and hysteroscopic morcellation respectively: † R2=0.59; ‡ R2=0.83; § R2 =0.55.
Chapter 4 36
0 5 10 15 20 25 30 35 40 45
0 2 4 6 8 10 12 14 16
Volume of intrauterine lesion (cm3)
Operating time (min)
Resectoscope Morcellator
Raw data Resectoscope Raw data Morcellator
Figure 2 | The regression curves of the linear regression model of operating time in association with the volume of intrauterine abnormality and technique.
Model: Resectoscopy: Y=13.65 + 1.10*X Morcellator: Y=5.42 + 1.10*X
Y=operating time in min, X=volume of intrauterine abnormality in cm3
Figure 3 | The surgeon scores on a visual analogue scale (VAS) regarding the use of the instrument.
Range: 0=poor; 10=very comfortable.
0 2 4 6 8 10 12 14 16
0 1 2 3 4 5 6 7 8 9 10
Convenience with technique (VAS)
Number of procedures
Resectoscope Morcellator
0 2 4 6 8 10 12 14 16
0 1 2 3 4 5 6 7 8 9 10
Convenience with technique (VAS)
Number of procedures
Resectoscope Morcellator
0 2 4 6 8 10 12 14 16
Volume of intrauterine lesions (cm3)
the procedure had to be aborted prematurely due to an imminent fluid overload. No further complications were reported.
In two cases histological analysis of the specimen revealed a malignant endometrial carcinoma. One patient was postmenopausal and was diagnosed preoperatively with an intrauterine polyp and a type 0 myoma, whereas the other patient was premeno- pausal and diagnosed with a type 0 myoma. Both of these patients were treated with the hysteroscopic morcellator and subsequently underwent a hysterectomy with a bilateral salpingo-oophorectomy. Two other preoperatively identified myomas were diagnosed as endometrial polyps at histological analysis.
Discussion
This randomised controlled study demonstrated that the new hysteroscopic morcella- tor technique for the removal of endometrial polyps and submucous myomas offers an effective alternative to conventional resectoscopy in inexperienced hands. First of all, the operating time was reduced with the hysteroscopic morcellator when compared to the removal with the conventional resectoscope. As a consequence, the amount of fluid deficit was reduced as well. Since complications are related to the amount of fluid deficit, and normal saline is used as a distension medium with the hysteroscopic Figure 4 | The subjective trainer scores on a visual analogue scale (VAS) for the easiness of use by the resident for the conventional resectoscope and the hysteroscopic morcellator. Range: 0=poor;
10=very comfortable.
0 2 4 6 8 10 12 14 16 18 20
1 2 3 4 5 6 7 8 9 10
Resectoscope Morcellator
Number of procedures
Convenience with technique (VAS) 0
2 4 6 8 10 12 14 16
0 1 2 3 4 5 6 7 8 9 10
Convenience with technique (VAS)
Number of procedures
Resectoscope Morcellator
Chapter 4 38
morcellator (instead of electrolyte-free solution), the risk of fluid overload decreased considerably when using this method. Furthermore, the residents and their trainers felt more comfortable using the morcellator than using the conventional resectoscope.
The benefit of hysteroscopy as a surgical tool in combination with women’s desire to preserve their uterus in spite of dysfunction has made hysteroscopic surgery an important therapy, especially in cases of abnormal uterine bleeding and infertility. Like all endo- scopic procedures, practicing hysteroscopic surgery requires training and experience.
Moreover, the safety and outcome of surgical procedures are clearly linked to adequate training [Whitted 2003]. Learning conventional resectoscopy is time-consuming. With this technique, the surgeon must pass both the hysteroscope and resectoscope a numer- ous times in and out of the uterine cavity to remove excised tissue. This increases the risk of perforating the uterus.
In our opinion the advantages of the morcellator technique are twofold. First, remov- ing intrauterine disorders with the morcellator requires less complicated movements than with the resectoscope. Second, and of greater importance, tissue fragments are removed through the instrument which prevents chips from accumulating and obscur- ing the hysteroscopic view. The instrument therefore makes fewer entries reducing the risk of damaging the uterus.
An important goal of this study was to determine whether a difference in learning curve could be identified regarding the two procedures. The results show that the number of procedures performed previously does not seem to affect the time needed to remove intrauterine disorders. This might be explained by the following. To start with, the first procedures that a resident performs require intensive trainer supervision, whereas dur- ing later procedures the resident is considered able to work more independently. Under such circumstances the operating time of the first procedures might be influenced posi- tively. Videotaping the procedures and subsequently scoring the intensity of the trainer’s guidance might have helped to correct for this possible confounder [Schijven 2005].
In addition, since learning hysteroscopic techniques is commonly believed to be dif- ficult, the sample size may have been too small as each resident performed only five procedures of each technique. But also, since each patient is different -and although we corrected for the volume of the intrauterine disorder- other variables (e.g. localisation of the lesion or bleeding) could have been responsible for certain difficulties of the hystero- scopic removal. These may have contributed to an obscured view of a possible learning curve as well. Finally, it is noteworthy that approximately 20% of the resectoscopy pro- cedures were taken over by the trainer, whereas only 3% of the morcellator procedures could not be finished by the residents themselves. If this had not happened, procedure time differences might have been more pronounced.
A training simulator could overcome these limitations; no doubt, however, that some difficulties encountered in the operating room cannot be imitated. Although our study
could not provide adequate information on a possible learning curve, residents felt significantly more comfortable with the hysteroscopic morcellator than with the con- ventional resectoscope. Likewise, the trainer’s evaluation of the resident’s skills was also in favour of the morcellator.
In our opinion surgery techniques should be user friendly, not only to prevent distraction due to technique related difficulties but also for teaching purposes.
Unfortunately, literature deals with this subject sparsely. To the best of our knowledge this is the first study on this subject in hysteroscopic surgery. In contrast to other stud- ies describing alternative techniques (e.g. bipolar resectoscopy), we randomly assigned patients to either removal with the conventional resectoscope or with the hysteroscopic morcellator in order to make an adequate comparison.
