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Evidence supports that surgeons are at high risk for work-related musculoskeletal disorders.
The objective of the study was to compare the effect of different chairs on work-related musculoskeletal discomfort for surgeons during vaginal operations.
This crossover study randomly assigned 4 surgeons to 4 chair types using a 4 × 4 Latin square model: a conventional round stool, a round stool with a backrest, a saddle chair with a backrest, and a Capisco chair. Subjective assessments of surgeon discomfort were performed with a validated body discomfort survey, and workload was assessed with the surgical task load index. The objective postural load was quantified with inertial measurement units of the modified rapid upper limb assessment limits. Subjective and objective assessments of chair comfort were performed with an 11 point scale and seat interface pressure–mapped distributions, respectively. The primary outcome was the difference in body discomfort scores between pre- and postsurgery measurements. Secondary outcomes were the differences in chair comfort scores, postural load, and seating interface pressure–mapped distribution. For each outcome, comparisons among the chair types were based on fitting a linear mixed model that handled the surgeon as a random effect and the chair type as a fixed effect.
Data were collected for 48 vaginal procedures performed for pelvic organ prolapse. Mean (SD) duration of surgery was 122.3 (25.1) minutes. Surgeons reported body discomfort during 31 procedures (67.4%). Subjective increase in discomfort from the preoperative state was noted most commonly in the lower back (n = 14, 30.4%), followed by right shoulder (n = 12, 26.1%), upper back (n = 8, 17.4%), hips and buttocks (n = 7, 15.2%), left shoulder (n = 6, 13.0%), right or left thigh (n = 6, 13.0%), and neck (n = 6, 13.0%). Pre- and postsurgery body discomfort scores did not differ with respect to chair type. Chair discomfort scores for the round stool and the saddle chair were significantly higher than the round stool with backrest and the Capisco chair (P < .001). Although the average modified rapid upper limb assessment postural scores showed moderate to high musculoskeletal risk of neck and shoulder discomfort across the 4 surgeons; chair type did not affect postural scores. The saddle chair had significantly reduced dispersion of seated pressure vs the round stool with backrest (P ≤ .001), depicted by the number of cells with pressure values >5 mm Hg. An increased dispersion of pressure across the chair surface was associated with increased comfort (Spearman correlation, 0.40, P = .006).
Musculoskeletal strain and associated discomfort for surgeons are very high during vaginal operations. Chair type can affect comfort, and chairs with more uniform distribution and fewer pressure points are more comfortable. However, the chair type used in surgery did not influence the musculoskeletal postural load findings.
To adapt to the new challenges, surgeons have subjected themselves to work in poor ergonomic conditions for long periods in the operating room. The resulting fatigue and discomfort may impair their concentration and jeopardize their performance and thereby affect patient safety.
A nonergonomic work environment also may result in occupational injuries to surgeons that may affect their career longevity.
Evidence supports that surgeons are at high risk for work-related musculoskeletal disorders. About 88% of surgeons and gynecologists who perform minimally invasive procedures have reported discomfort or pain after performing an operation.
reported that 97% of surgeons expressed the need for ergonomic improvements in the operating room. With the prediction of a worsening shortage of surgeons in the United States, as well as an aging surgeon workforce, surgeons may be required to perform operations until older ages.
In gynecological surgery, the vaginal route is a traditional approach and involves working in a constrained space and in unfavorable postures for long durations. A survey of gynecological surgeons showed that 86.7% of surgeons performing vaginal surgery experienced work-related musculoskeletal discomfort.
objectively measured and quantified postural load of surgeons during vaginal procedures and reported it to be great, especially during vaginal hysterectomy.
We assessed the magnitude of musculoskeletal disorders among gynecologists who perform vaginal surgery and compared the effect of different chair types on work-related musculoskeletal discomfort and load during a procedure.
Materials and Methods
This crossover study randomly assigned 4 gynecologists to use 4 chair types while performing vaginal procedures for pelvic organ prolapse. The chairs studied were the round stool, the round stool with a backrest, the saddle chair with a backrest,
and the Capisco chair (Figure 1). The 4 types were randomly assigned to the surgeons using 3 separate 4 × 4 Latin squares. This strategy allowed us to block on surgeon and chair order and to have 3 replications per surgeon-chair combination.
Demographic data collected for the participants included age, body mass index, years of surgical experience, handedness, previous injury or illness, average number of surgical operations performed per month, and percentage of time spent performing vaginal or abdominal procedures. The physical activity of an individual surgeon was assessed using the validated World Health Organization Global Physical Activity Questionnaire.
to assess the baseline discomfort status of the surgeon. Before surgery, pressure mats with pressure sensors were placed on the seat pan of each chair. We recorded body postures and movements in the operating room using inertial measurement units (12M, SXT version; APDM, Inc, Portland, OR)
Four inertial measurement units were attached to each surgeon’s body at the forehead, at the upper chest, and on bilateral arms above the elbows. Immediately after the procedures, the surgeons were asked to complete the first postsurgery questionnaire. The surgeons completed the second postsurgery questionnaire the day after the recorded surgery.
The first postsurgery questionnaire asked details of the surgery, including procedure type, duration, an 11 point visual analog scale assessment of comfort of the chair and chair seat pan, the Surgical Task Load Index
When the surgeon performed >1 vaginal hysterectomy in a day, only the first case was included in the study. Similarly, when the surgeon performed a vaginal procedure for prolapse on 2 consecutive days, the procedure performed on the second day was not included. This inclusion strategy allowed for a washout period between the interventions and increased the study’s internal validity. When the surgeon performed a vaginal procedure on 2 consecutive days, the surgeon was asked to complete the postsurgery questionnaire early the second day before the upcoming procedure.
The primary outcome was the difference between the pre- and postsurgery Cornell Musculoskeletal Discomfort Questionnaire ratings that provided a subjective assessment of surgeon discomfort. Secondary outcomes were postural load
for each body part, with the data collected by the inertial measurement units (Table 1). The body angles measured with inertial measurement units were neck flexion and extension, trunk flexion and extension, and bilateral shoulder elevation.
Table 1Definition of risk category for each body part per modified rapid upper limb assessment
Reproduced, with permission, from the Mayo Foundation for Medical Education and Research.
Neck flexion and extension
Trunk flexion and extension
Flexion between 0° and 10°
Flexion at 0°
Elevation between 0° and 20°
Flexion between 10° and 20°
Flexion between 0° and 20°
Elevation between 20° and 45°
Flexion between 20° and 60°
Elevation between 45° and 90°
Singh et al. Chair types during vaginal surgery. Am J Obstet Gynecol 2016.
For each procedure, we calculated the percentage of time spent in a specified range of risk categories for each body part (Table 1). These percentages of time were multiplied by the modified rapid upper limb assessment risk score for the specific category, and the products were summed to reach an overall risk score for each body part measured.
Seating interface pressures using pressure mapping
The pressure map reading for each surgical procedure was visually inspected by television for continuity or abnormal readings. The resolution of each mapping session was 256 cells; the range of pressure at each cell was 5–200 mm Hg. Data were extracted from 10 random frames of the final 10 minutes of the pressure mapping. The following values were calculated for each pressure map:
Average pressure, defined as the average pressure of all cells with >5 mm Hg pressure.
Frequency of pressure, defined as the total number of cells with pressure values ≥200 mm Hg.
Surface area, defined as the total number of cells among 256 cells that have values >5 mm Hg. This measurement captures the dispersion of seated pressure across the chair seat pan surface.
Percentage frequency, defined as the percentage of cells with values of ≥200 mm Hg in 1 frame.
The sample size for this project was chosen on the basis of feasibility. Given that 4 surgeons participated and the option of 4 or 5 chairs, we decided on 4 chairs to design the randomization using a 4 × 4 Latin square. The choice of replications per surgeon-chair combination was selected on the basis of the desired replications but without overburdening the participants.
Statistical analysis was performed using a software package (SAS statistical software, version 9.3; SAS Institute Inc, Cary, NC). For each outcome measure, comparisons between chair types were based on fitting a linear mixed model that handled the individual surgeon as a random effect and the individual chair type as a fixed effect. A square root transformation was applied to the percentage of time spent in risk category 3 or 4 from the inertial measurement unit measurements, before fitting the models.
P values were 2 sided, and values of P < .05 were considered statistically significant. When the overall test for differences among chair types was statistically significant, pairwise comparisons between chair types were evaluated without adjusting for multiple comparisons.
The mean (SD) age of surgeon participants was 43.8 (4.8) years. The 4 surgeons were right-handed and, per the baseline questionnaire, usually operated 2 or 3 days per week and for 5–8 hours on a typical surgery day. Two surgeons preferred the round stool when performing vaginal operations; the other 2 surgeons preferred the round stool with a backrest. Of the surgeons, 3 (75.0%) devoted more than one-half of their total surgical time toward performing vaginal procedures.
The 4 surgeons responded with a somewhat agree when asked whether they were exhausted when they got home from work, and they reported experiencing work-related musculoskeletal discomfort previously. The body parts most commonly involved were neck (100%), lower back (100%), shoulders (75.0%), upper back (75.0%), and fingers or thumb (75.0%).
Factors contributing to the musculoskeletal discomfort were open abdominal operations, vaginal procedures, surgery duration >2 hours, and operating days >6 hours. Although the surgeons denied having any medical condition that may contribute to the discomfort, they admitted seeking medical help for the musculoskeletal discomfort. As per the World Health Organization Global Physical Activity Questionnaire recommendations, the 4 surgeons reported engaging in physical activity of moderate and vigorous intensity for >600 metabolic equivalent minutes per week.
Data were collected on 48 operations performed by 4 surgeons. The mean (SD) case duration was 122.3 (25.1) minutes. The surgeries included vaginal hysterectomy and modified McCall’s culdoplasty (100%), along with anterior colporrhaphy (93.8%), posterior colporrhaphy (83.3%), midurethral sling (35.4%), and suprapubic catheter placement (68.8%). For all dimensions, the mean (SD) surgical task load index score was 39.6 (13.7) on a scale of 0–100.
Surgeons reported experiencing body discomfort (assessed by a modified Cornell Musculoskeletal Discomfort Questionnaire) while performing 31 of the 46 surgeries. (67.4%) Body discomfort was present both before and immediately after surgery (Figure 4). A change in body discomfort score was assessed by calculating the difference between the reported body discomfort ratings from the preoperative state and from immediately after the procedure.
Overall, an increase in body discomfort immediately after the operation was noted most commonly in the lower back (n = 14, 30.4%), followed by right shoulder (n = 12, 26.1%), upper back (n = 8, 17.4%), hips and buttocks (n = 7, 15.2%), left shoulder (n = 6, 13.0%), right or left thigh (n = 6, 13.0%), and neck (n = 6, 13.0%).
A tendency existed for surgeons to have increased upper back discomfort after using the round stool compared with the Capisco chair and increased lower back discomfort after using either of the round stools compared with the Capisco chair (Figure 5). However, these comparisons, as well as all other chair comparisons, did not reach statistical significance.
When body discomfort scores were assessed on the day after the surgical procedure, surgeons noted increased discomfort most commonly in the right shoulder (n = 11, 24.0%), followed by neck (n = 9, 19.6%), upper back (n = 9, 19.6%), lower back (n = 8, 17.4%), and left shoulder (n = 6, 13.0%). The neck and left shoulder discomfort was noted to increase on the day after surgery as compared with immediately after the procedure (n = 6, 13%). On the contrary, the discomfort in right shoulder (n = 6, 13%), upper back (n = 8, 17%), and lower back (n = 13, 27.6%) improved on the day after surgery.
Throughout a procedure, the surgeon’s neck spent a median of 11.1% of the time flexed >20° (risk category 3) and a median of 46.3% extended >0° (risk category 4) (data not shown). However, when compared across the chair types, the median percentage of time when the neck was in a position of risk category 3 or 4 was not significantly different (P = .27) (Table 2). Similarly, significant differences were not observed among the chair types for percentage of time spent with the trunk flexed >20° or either shoulder elevated >45°.
Table 2Comparison of the percentage of time during the vaginal procedure spent in risk category 3 or 4
The chair and chair seat pan discomfort scores (Figure 6) showed that both the round stool and the saddle chair were significantly more uncomfortable than the round stool with a backrest and the Capisco chair (each P < .05); all other comparisons among chairs were not statistically significant.
The mean (SD) seating pressure was 94.7 (27.0) mm Hg and did not differ across the chairs or the surgeons (Figure 7A). Similarly, no difference was found in the frequency and the percentage frequency of the cells with seating pressure >200 mm Hg across the chairs (Figures 7, B and D). However, the saddle chair was noted to have significantly reduced dispersion of the seat pressures (ie, surface area) compared with the round stool with backrest (P = .001), the round stool (P = .01), and the Capisco chair (P = .01) (Figure 7C).
An increased dispersion of seat pressure across the chair surface (ie, surface area) was significantly associated with increased chair comfort (Spearman correlation, 0.40, P = .006). Such a correlation was not observed between chair comfort and the rest of the pressure mapping variables (data not shown).
Our study showed that the surgeon participants experienced discomfort during 67.4% of vaginal procedures. The reported discomfort was mostly observed in the back, shoulders, and neck, and these have been shown to be the commonly affected body parts among surgeons.
The postural risk categories, calculated with the modified rapid upper limb assessment, stayed in moderate or severe risk (category 3 or 4) for the upper body for a majority of time, which is a matter of concern. Zhu et al
assessed and quantified the postural load during vaginal procedures and all the surgeons stood during the entire procedure. Similar to our findings, the authors noted that the neck was most affected during vaginal surgery. However, the percentage duration of time when the neck was in nonergonomic posture (deviation >30°) was less when the surgeons were standing (31–44% as reported by Zhu et al) as compared with the seated position (51–64%, as reported in our study). In addition, Zhu et al used Ergo PART for assessing postural load, which visually assessed posture by applying tape on the back of the surgeon. This tool is less accurate for measuring postural load than the inertial measurement unit sensors used in our study.
In view of serious physical strain on surgeons noted during vaginal operations, it is imperative that strategies be developed that are aimed toward decreasing the risk of occupational injuries among the surgeons. The surgeon participants reported that the round stool with a backrest and the Capisco chair were more comfortable than the saddle chair and the round stool.
In addition, we noted that the saddle chair had significantly reduced surface (ie, dispersion) of seating pressure. Investigators have demonstrated that chair types with greater surface or dispersion of seating interface pressure tend to be preferred by surgeon study participants.
However, we did not observe a difference in the body part discomfort scores or postural load with respect to the chairs.
The unfavorable postural loads observed across the 4 chairs underscore the need to adopt other interventions in addition to using a comfortable chair to further decrease postural load. Implementation of intraoperative breaks has been shown to decrease physical and mental fatigue among surgeons performing abdominal and laparoscopic procedures.
The effect of intraoperative breaks to decrease strain during vaginal surgery is promising, but it has not been explored.
The present study has several strengths. It is a randomized prospective study and uses such validated instruments as the Cornell Musculoskeletal Discomfort Questionnaire and the surgical task load index. The comparison of chairs during vaginal surgery is a novel idea. Data were collected in real time during the entire procedure instead of in a simulation laboratory. Postural load and chair comfort were evaluated objectively using the inertial measurement units and pressure map. Compared with the other methods of measuring the postural load, such as the original observational rapid upper limb assessment methodology,
However, a difference in chair design may affect the seating interface pressures, which may be a drawback of this technique.
Another limitation of this study is the limited number of surgeon participants. The study is subjected to bias because the surgeons could not be blinded to the chairs and the preferred chair for 2 surgeons prior to the study was a round stool with a backrest.
Surgeons are prone to substantial musculoskeletal strain while performing vaginal procedures. The round stool with a backrest and the Capisco chair were reported to be more comfortable than the saddle chair and the round stool. Nonetheless, the chair type did not influence musculoskeletal discomfort and postural load. Hence, new strategies need to be formulated to minimize the musculoskeletal discomfort among vaginal surgeons.
The views expressed herein are those of the authors and do not necessarily represent the official views of the National Institutes of Health.
This study was supported by Clinical and Translational Science Awards grant UL1 TR000135 from the National Center for Advancing Translational Science. S.H. received a research grant from Stryker Endoscopy, and J.B.G. serves on the advisory board of Astora Women’s Health LLC and receives royalties from UpToDate, Inc and Elsevier BV.
The authors report no conflict of interest.
Cite this article as: Singh R, Carranza Leon DA, Morrow MM, et al. Effect of chair types on work-related musculoskeletal discomfort during vaginal surgery. Am J Obstet Gynecol 2016;215:648.e1-9.