- Email: [email protected]
Variance in Abdominal Wall Anatomy and Port Placement in Women Undergoing Robotic Gynecologic Surgery
Original Article
Variance in Abdominal Wall Anatomy and Port Placement in Women Undergoing Robotic Gynecologic Surgery Catherine A. Matthews, MD*, Christine M. Schubert, PhD, Ashley P. Woodward, MD, and Edward J. Gill, MD From the Departments of Obstetrics and Gynecology (Drs. Matthews, Woodward, and Gill) and Biostatistics (Dr. Schubert), Virginia Commonwealth University Medical Center, Richmond.
ABSTRACT Study Objectives: To estimate whether variability in the size and ratios of the lower and upper abdomen exist in women undergoing robotic gynecologic surgery and whether demographic variables are significantly associated, and to determine the association between abdominal wall dimensions and supraumbilical robotic port placement. Design: Prospective cohort study (Canadian Task Force classification II-2). Setting: University teaching hospital. Patients: Seventy-eight women undergoing robotic surgery between May 2008 and March 2009. Intervention: Measurements from the symphysis pubis to the umbilicus (lower abdomen), umbilicus to the xyphoid process (upper abdomen), and distance between the anterior superior iliac crests were obtained at surgery. A multiple linear regression model was created to determine the relationships between abdominal wall measurements, demographic variables, and need for supraumbilical robotic port placement. Measurements and Main Results: Fifty-six white and 22 black women were enrolled. Mean lower abdominal length was significantly affected by body mass index (BMI) (p ,.001) and race (p 5 .006), with white women having longer measurements (17.1 cm vs 15 cm). Mean lower abdominal width was independent of age (p 5 .95) or race (p 5 .98), but was significantly correlated with BMI (p ,.001). Mean upper abdominal length correlated with BMI (p ,.001) and age (p 5 .03) but not race (p 5 .13). Ratios of bottom to top were significantly affected by race (p 5 .002) and age (p 5 .008) but not BMI (p 5 .07). Adjustments to port placement above the umbilicus were made in 44 of the 74 women (59.5%). Those who required supraumbilical port placement had a significantly shorter mean (SD) distance between the symphysis pubis and the umbilicus (14.99 [1.36] vs 18.55 [2.21]; p ,.001). Conclusions: Significant variability in abdominal wall anatomy exists in women undergoing robotic gynecologic surgery, and the need for supraumbilical robotic port placement is common. Journal of Minimally Invasive Gynecology (2010) 17, 583–586 Ó 2010 AAGL. All rights reserved. Keywords:
Abdominal wall anatomy; Ethnic differences; Port placement; Robotic surgery
Laparoscopic port placement for pelvic surgery has traditionally centered on the most prominent external landmark, the umbilicus. This likely evolved because of cosmetic reasons [1] and ease of establishing peritoneal access through the thinnest dimension of the abdominal wall. Surgeons The authors have no commercial, proprietary, or financial interest in the products or companies described in this article. Presented at the 38th Annual American Association of Gynecologic Laparoscopists, Orlando, Florida, November 15–19, 2009. Corresponding author: Catherine A. Matthews, MD, Department of Obstetrics and Gynecology, Virginia Commonwealth University Medical Center,1250 E. Marshall St. Box 980034, Richmond, VA 23298. E-mail: [email protected] Submitted December 6, 2009. Accepted for publication April 23, 2010. Available at www.sciencedirect.com and www.jmig.org 1553-4650/$ - see front matter Ó 2010 AAGL. All rights reserved. doi:10.1016/j.jmig.2010.04.008
may also assume that the umbilicus is located in the vertical midline, making it an optimal site for a central camera location. Several studies, however, have demonstrated significant variability in umbilical location and that its position is negatively correlated with body mass index (BMI) [2–4]. Selection of an optimal abdominal wall location for port arrangements is important in every laparoscopic operation, but becomes critical in robotic surgery because of the fixed location of the camera, limited mobility of each robotic arm, and potential for robotic arm interference when robotic ports are not positioned at least 10 cm apart [5]. In an article describing the nuances of optimum robotic port placement after 1200 cases, Hemal et al [6] commented that individual variations in patient height, weight, BMI, and muscularity can affect the variable mobility of the robotic arms and that
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individual patient consideration is essential for surgical success [6,7]. This subjective observation is supported by a study of abdominal wall dimensions and umbilical position in 259 male and female patients that found significant variability in torso length and abdominal girth with BMI, and a clear relationship between increasing BMI and a more caudal umbilical position [2]. When performing our first 10 robotic procedures, we noted that in women with relatively short dimensions of the lower half of the abdomen, we frequently had to place the camera port, accessory port, and at least 1 robotic port above the umbilicus to accommodate the need for larger interport distances to prevent robotic arm collisions. In our early clinical experience, we noted a wide variance in the relative dimensions of the upper and lower abdomen and how often a more caudally positioned umbilicus presented a less desirable location for robotic port placement. We hypothesized that demographic variables other than BMI may potentially account for variation in the relative abdominal wall dimensions. The objective of the present study, therefore, was to estimate whether variability in the size and ratios of the lower and upper abdomen existed in women undergoing robotic gynecologic surgery, whether any demographic variables are significantly associated, and whether subsequent robotic port placement above the umbilicus was necessary. Material and Methods We performed a prospective cohort study of 74 women undergoing robotic gynecologic surgery because of benign indications at Virginia Commonwealth University Medical Center between May 2008 and March 2009. Institutional review board approval was obtained, and patients provided informed consent. All eligible patients were included in the study. After induction of anesthesia, 3 measurements were made of the abdominal wall using a paper tape measure: distance from the symphysis pubis to the umbilicus (lower abdomen), distance from the umbilicus to the xiphoid process (upper abdomen), and distance between the left and right anterior superior iliac crests. Ratios of the upper to lower abdominal dimensions were then calculated. Demographic data including age, race, and BMI were obtained and recorded on data sheets. Operative reports were reviewed to determine the frequency of robotic port placement above the umbilicus. Statistical analysis was performed using commercially available software (SAS version 9.1; SAS Institute, Inc., Cary, NC). To investigate the effect of each independent demographic variable on the abdominal wall measurements, regression models that included age, BMI, and race were examined with each measurement and ratio as the outcome. Least square means were computed and compared between racial groups when race was significant. Least squares means, as opposed to arithmetic means, are adjusted (or weighted) means computed to describe the mean levels for each group (here, race) after accounting for the effects of the other pre-
dictors in the model (age and BMI). Arithmetic means do not make these adjustments and, thus, reflect racial differences without considering other, possibly significant, predictors [8]. Frequency counts for supraumbilical port placement and t tests were used to describe anatomical differences between those women who required changes in port placement vs those who did not. In addition, logistic regression was used to examine the odds of requiring adjustments to port placement based on anatomical measurement. In all statistical comparisons, p ,.05 was considered significant. Results Fifty-six white and 22 African American women were enrolled. White women were significantly older (mean [SD], 55.4 [12.7] years vs 43.6 [12.7] years; p 5 .005), and African American women were significantly heavier (BMI, 35.3 [9.3] vs 27.6 [6.12]; p 5 .001). The demographic variables and mean value of each abdominal wall dimension according to racial group are given in Table 1. Surgical procedures performed included 26 sacrocolpopexies, 30 supracervical hysterectomies with cervicosacropexy, and 18 total robotic hysterectomies. All procedures were completed robotically without significant arm interference. In the multiple linear regression model, the relationships between abdominal wall measurements and demographic variables were as follows: for the distance between the anterior superior iliac crests, there were no effects of age (p 5 .95) or race (p 5 .98); however, BMI was significantly associated (p ,.001). Accounting for age and race, every unit increase in BMI was associated with an increase of 0.74 cm in the horizontal lower abdominal dimension. For the distance between the symphysis pubis and the umbilicus (lower vertical abdomen), there were significant effects of BMI (p ,.001) and race (p 5 .006). Every unit increase in BMI was associated with an increase of 0.18 cm in the lower abdomen, irrespective of race. White women had significantly longer lower vertical dimensions (16.51 cm; 95% confidence interval [CI], 16.5–17.6) compared with Table 1
Demographic and abdominal wall dimensions according to race* Race Variable
Black (n 5 22)
White (n 5 52)
p Value
Age, yr BMI kg/m ASIS to ASIS SP to Umb Umb to Xyp Ratio of bottom to top Ratio of length to width
43.68 (12.7) 35.33 (9.32) 33.77 (6.84) 16.25 (2.58) 21.89 (3.60) 0.76 (0.14) 1.16 (0.18)
55.44 (12.7) 27.67 (6.12) 28.17 (7.73) 16.51 (2.46) 18.84 (3.43) 0.90 (0.18) 1.29 (0.20)
.005 .001 .004 .68 .009 .002 .008
ASIS to ASIS 5 distance between anterior superior iliac crests; BMI 5 body mass index, calculated as weight in kilograms divided by height in meters squared; Sp to Umb 5 distance between symphysis pubis and umbilicus; Umb to Xyp 5 distance between umbilicus and xiphoid process. * Values are given as mean (SD).
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Abdominal Wall Anatomy and Port Placement in Women Undergoing Robotic Gynecologic Surgery
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The ratio of the bottom to top half of the abdomen was significantly affected by race (p 5 .002) and age (p 5 .008) but not BMI (p 5 .07). White women had significantly higher ratios of bottom to top compared with African American women (0.90; CI, 0.85–0.95 and 0.75; 95% CI, 0.67–0.82, respectively; Fig. 1), and increase in age was associated with a decrease in this ratio. The ratio of length to width was affected only by BMI (p 5 .001), and for every unit increase in BMI, the ratio of length to width decreased by 0.01. Adjustments to port placement above the umbilicus were made in 44 of the 74 women (59.5%), and these adjustments were similar for both races (59.1% of African American women and 59.6% of white women). Women who required supraumbilical port placement had a significantly shorter mean (SD) distance between the symphysis pubis and the umbilicus (14.99 [1.36] vs 18.55 [2.21]; p ,.001), lower mean BMI (27.33 [5.93] vs 33.79 [9.06]; p 5 .001), and shorter ratios of bottom to top half of the abdomen (0.80 [0.14] vs 0.94 [0.21]; p 5 .003) (Table 2). There was a 2.3-cm difference between the 95% CIs for the distance between the symphysis pubis and the umbilicus in women who required adjustment (95% CI, 14.57–15.40) vs those who did not (95% CI, 17.72–19.38) (Fig. 2). Using stepwise procedures, the distance between the symphysis pubis and the umbilicus was the most and only significant predictor remaining in the model for the need to change port placement (receiver operating characteristic area under the curve, 0.96). Fig. 1. Model estimated lengths and ratios, with 95% confidence intervals, according to race after adjustment for age and body mass index.
African American women (16.25; 95% CI, 14.0–15.9), with a mean difference of 2.10 cm (Fig. 1). Age was not significantly associated (p 5 .06) with the distance between the symphysis pubis and the umbilicus. For the distance between the umbilicus and the xiphoid process (upper abdomen), there were significant effects of BMI (p ,.001) and age (p 5 .03) but not race (p 5 .13). Every unit increase in BMI was associated with an increase of 0.33 cm, and for each additional year of age, the dimension of the upper abdomen was 0.06 cm longer.
Discussion The results of the present study demonstrate significant variability in the relative dimensions of the abdominal wall in women undergoing robotic gynecologic surgery, with a corresponding effect on robotic port placement. Of women with a mean distance of less than 16 cm from the symphysis pubis to the umbilicus, 100% required port placement above the umbilicus. While much of the observed variability was attributable to BMI, race was significantly associated with lower abdominal dimensions, and age was significantly associated with upper abdominal dimensions. It is logical that as a woman ages and loses abdominal muscle tone, the
Table 2
Abdominal wall measurements and supraumbilical port placement No change in port placement (n 5 30)
Change in port placement (n 5 44)
Difference in mean between groups
Variable
Mean
SD
Mean
SD
Mean difference
SD
p Value
Age BMI ASIS to ASIS Sp to Umb Umb to Xyp Ratio of bottom to top Ratio of length to width
47.67 33.79 32.43 18.55 20.55 0.94 1.26
13.13 9.06 9.88 2.22 4.08 0.21 0.22
54.86 27.33 28.07 14.99 19.19 0.80 1.25
13.50 5.93 5.59 1.36 3.40 0.14 0.19
27.20 6.46 4.37 3.56 1.36 0.13 0.01
13.35 7.35 7.61 1.76 3.69 0.17 0.21
.03 .03 .001 ,.001 .13 .003 .78
ASIS to ASIS 5 distance between anterior superior iliac crests; Sp to Umb 5 distance between symphysis pubis and umbilicus; Umb to Xyp 5 distance between umbilicus and xiphoid process; BMI 5 body mass index, calculated as weight in kilograms divided by height in meters squared.
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Fig. 2. Ninety-five percent confidence intervals for change in port placement to a supraumbilical site. A mean difference of 2.3 cm existed between women who required supraunbilical port placement vs those who did not.
umbilicus may sag and assume a relatively lower position on the abdominal wall. This would correspond with a longer mean distance from the umbilicus to the xiphoid process and decreasing ratio of lower to upper abdominal dimensions. A rational explanation for our observed racial differences in lower abdominal dimensions may also exist based on observations of significant ethnic variability in pelvic structure. In an anthropologic study from the University of Michigan, pelvises from age-matched African American women and European American women were compared. After controlling for height, African American women had a 5.1% smaller pelvic floor area compared with European American women. This was attributable to a 10.4% smaller posterior area, whereas the anterior areas were similar [9]. Similar results were reported from studies using magnetic resonance imaging in women of varying race/ethnicity. White women were consistently noted to have a larger levator hiatus and bony pelvis compared with nonwhite women [10–12]. Smaller pelvises could, in theory, be associated with relatively shorter dimensions from the symphysis pubis to the umbilicus. The clinical implications of our study findings are significant. When performing robotic surgery, careful attention must be made to the location of the umbilicus in reference to the symphysis pubis because a distance less than 16 cm will likely require supraumbilical port placement. Robotic surgeons, particularly those just adopting this technology, must be aware that in many women, the relative dimensions of the upper abdomen are much larger than those of the lower abdomen, and port placement above the umbilicus may be routine. Patients should be counseled about this preoperatively because cosmetic implications may exist. A potential limitation of the present study includes the absence of data about the relative dimensions of the abdominal wall after insufflation of the peritoneal cavity, which could have a significant effect on appropriate port placement. Abdominal wall elasticity could have a more profound effect on robotic port placement than the actual position of the umbilicus. In our clinical experience, however, regardless of the ease of abdominal distention, placement of the camera
through the umbilicus in women with short lower abdominal dimensions remains problematic. A second limitation is our limited sample size of African American women. Because, to our knowledge, no published data exist regarding ethnic variability in abdominal wall anatomy, we were not able to perform an accurate power calculation to verify the potential effect of race. It is possible that selection bias resulted in our observed ethnic differences; however, because all eligible women were enrolled, this was minimized. In conclusion, women undergoing robotic surgery to treat benign gynecologic conditions demonstrated significant variability in the relative dimensions of the abdominal wall, and individual consideration of this anatomy was paramount in the successful completion of the planned procedure. While the umbilicus serves as a technically and cosmetically appealing site of entry, it may not be appropriately situated on the abdominal wall to facilitate a robotic procedure. Gynecologic surgeons must extend their expertise to placing robotic ports in the upper abdomen in women with limited lower abdominal dimensions.
References 1. Muhe E. Long-term follow-up after laparoscopic cholecystectomy. Endoscopy. 1992;24:754–758. 2. Ambardar S, Cabot J, Cekic V, et al. Abdominal wall dimensions and umbilical position vary widely with BMI and should be taken into account when choosing port locations. Surg Endosc. 2009;23:1995–2000. 3. Hurd WW, Bude RO, DeLancey JO, Pearl ML. The relationship of the umbilicus to the aortic bifurcation: implications for laparoscopic technique. Obstet Gynecol. 1992;80:48–51. 4. Nezhat F, Brill AI, Nezhat CH, Nezhat A, Seidman DS, Nezhat C. Laparoscopic appraisal of the anatomic relationship of the umbilicus to the aortic bifurcation. J Am Assoc Gynecol Laparosc. 1998;5:135–140. 5. Eun D, Bhandari A, Boris R, Rogers C, Bhandari M, Menon M. Concurrent upper and lower urinary tract robotic surgery: strategies for success. BJU Int. 2007;100:1121–1125. 6. Hemal AK, Eun D, Tewari A, Menon M. Nuances in the optimum placement of ports in pelvic and upper urinary tract surgery using the da Vinci robot. Urol Clin North Am. 2004;31:683–692. 7. Advincula AP, Wang K. Evolving role and current state of robotics in minimally invasive gynecologic surgery. J Minim Invasive Gynecol. 2009;16:291–301. 8. Neter JWW, Kutner MH. Applied Linear Statistical Models. Homewood, IL: Richard D. Irwin, Inc.; 1974:888–890. 9. Baragi RV, Delancey JO, Caspari R, Howard DH, Ashton-Miller JA. Differences in pelvic floor area between African American and European American women. Am J Obstet Gynecol. 2002;187:111–115. 10. Hoyte L, Thomas J, Foster RT, Shott S, Jakab M, Weidner AC. Racial differences in pelvic morphology among asymptomatic nulliparous women as seen on three-dimensional magnetic resonance images. Am J Obstet Gynecol. 2005;193:2035–2040. 11. Handa VL, Lockhart ME, Fielding JR, et al. Racial differences in pelvic anatomy by magnetic resonance imaging. Obstet Gynecol. 2008;111: 914–920. 12. Rizk DE, Czechowski J, Ekelund L. Dynamic assessment of pelvic floor and bony pelvis morphologic condition with the use of magnetic resonance imaging in a multiethnic, nulliparous, and healthy female population. Am J Obstet Gynecol. 2004;191:83–89.
Variance in Abdominal Wall Anatomy and Port Placement in Women Undergoing Robotic Gynecologic Surgery Catherine A. Matthews, MD*, Christine M. Schubert, PhD, Ashley P. Woodward, MD, and Edward J. Gill, MD From the Departments of Obstetrics and Gynecology (Drs. Matthews, Woodward, and Gill) and Biostatistics (Dr. Schubert), Virginia Commonwealth University Medical Center, Richmond.
ABSTRACT Study Objectives: To estimate whether variability in the size and ratios of the lower and upper abdomen exist in women undergoing robotic gynecologic surgery and whether demographic variables are significantly associated, and to determine the association between abdominal wall dimensions and supraumbilical robotic port placement. Design: Prospective cohort study (Canadian Task Force classification II-2). Setting: University teaching hospital. Patients: Seventy-eight women undergoing robotic surgery between May 2008 and March 2009. Intervention: Measurements from the symphysis pubis to the umbilicus (lower abdomen), umbilicus to the xyphoid process (upper abdomen), and distance between the anterior superior iliac crests were obtained at surgery. A multiple linear regression model was created to determine the relationships between abdominal wall measurements, demographic variables, and need for supraumbilical robotic port placement. Measurements and Main Results: Fifty-six white and 22 black women were enrolled. Mean lower abdominal length was significantly affected by body mass index (BMI) (p ,.001) and race (p 5 .006), with white women having longer measurements (17.1 cm vs 15 cm). Mean lower abdominal width was independent of age (p 5 .95) or race (p 5 .98), but was significantly correlated with BMI (p ,.001). Mean upper abdominal length correlated with BMI (p ,.001) and age (p 5 .03) but not race (p 5 .13). Ratios of bottom to top were significantly affected by race (p 5 .002) and age (p 5 .008) but not BMI (p 5 .07). Adjustments to port placement above the umbilicus were made in 44 of the 74 women (59.5%). Those who required supraumbilical port placement had a significantly shorter mean (SD) distance between the symphysis pubis and the umbilicus (14.99 [1.36] vs 18.55 [2.21]; p ,.001). Conclusions: Significant variability in abdominal wall anatomy exists in women undergoing robotic gynecologic surgery, and the need for supraumbilical robotic port placement is common. Journal of Minimally Invasive Gynecology (2010) 17, 583–586 Ó 2010 AAGL. All rights reserved. Keywords:
Abdominal wall anatomy; Ethnic differences; Port placement; Robotic surgery
Laparoscopic port placement for pelvic surgery has traditionally centered on the most prominent external landmark, the umbilicus. This likely evolved because of cosmetic reasons [1] and ease of establishing peritoneal access through the thinnest dimension of the abdominal wall. Surgeons The authors have no commercial, proprietary, or financial interest in the products or companies described in this article. Presented at the 38th Annual American Association of Gynecologic Laparoscopists, Orlando, Florida, November 15–19, 2009. Corresponding author: Catherine A. Matthews, MD, Department of Obstetrics and Gynecology, Virginia Commonwealth University Medical Center,1250 E. Marshall St. Box 980034, Richmond, VA 23298. E-mail: [email protected] Submitted December 6, 2009. Accepted for publication April 23, 2010. Available at www.sciencedirect.com and www.jmig.org 1553-4650/$ - see front matter Ó 2010 AAGL. All rights reserved. doi:10.1016/j.jmig.2010.04.008
may also assume that the umbilicus is located in the vertical midline, making it an optimal site for a central camera location. Several studies, however, have demonstrated significant variability in umbilical location and that its position is negatively correlated with body mass index (BMI) [2–4]. Selection of an optimal abdominal wall location for port arrangements is important in every laparoscopic operation, but becomes critical in robotic surgery because of the fixed location of the camera, limited mobility of each robotic arm, and potential for robotic arm interference when robotic ports are not positioned at least 10 cm apart [5]. In an article describing the nuances of optimum robotic port placement after 1200 cases, Hemal et al [6] commented that individual variations in patient height, weight, BMI, and muscularity can affect the variable mobility of the robotic arms and that
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Journal of Minimally Invasive Gynecology, Vol 17, No 5, September/October 2010
individual patient consideration is essential for surgical success [6,7]. This subjective observation is supported by a study of abdominal wall dimensions and umbilical position in 259 male and female patients that found significant variability in torso length and abdominal girth with BMI, and a clear relationship between increasing BMI and a more caudal umbilical position [2]. When performing our first 10 robotic procedures, we noted that in women with relatively short dimensions of the lower half of the abdomen, we frequently had to place the camera port, accessory port, and at least 1 robotic port above the umbilicus to accommodate the need for larger interport distances to prevent robotic arm collisions. In our early clinical experience, we noted a wide variance in the relative dimensions of the upper and lower abdomen and how often a more caudally positioned umbilicus presented a less desirable location for robotic port placement. We hypothesized that demographic variables other than BMI may potentially account for variation in the relative abdominal wall dimensions. The objective of the present study, therefore, was to estimate whether variability in the size and ratios of the lower and upper abdomen existed in women undergoing robotic gynecologic surgery, whether any demographic variables are significantly associated, and whether subsequent robotic port placement above the umbilicus was necessary. Material and Methods We performed a prospective cohort study of 74 women undergoing robotic gynecologic surgery because of benign indications at Virginia Commonwealth University Medical Center between May 2008 and March 2009. Institutional review board approval was obtained, and patients provided informed consent. All eligible patients were included in the study. After induction of anesthesia, 3 measurements were made of the abdominal wall using a paper tape measure: distance from the symphysis pubis to the umbilicus (lower abdomen), distance from the umbilicus to the xiphoid process (upper abdomen), and distance between the left and right anterior superior iliac crests. Ratios of the upper to lower abdominal dimensions were then calculated. Demographic data including age, race, and BMI were obtained and recorded on data sheets. Operative reports were reviewed to determine the frequency of robotic port placement above the umbilicus. Statistical analysis was performed using commercially available software (SAS version 9.1; SAS Institute, Inc., Cary, NC). To investigate the effect of each independent demographic variable on the abdominal wall measurements, regression models that included age, BMI, and race were examined with each measurement and ratio as the outcome. Least square means were computed and compared between racial groups when race was significant. Least squares means, as opposed to arithmetic means, are adjusted (or weighted) means computed to describe the mean levels for each group (here, race) after accounting for the effects of the other pre-
dictors in the model (age and BMI). Arithmetic means do not make these adjustments and, thus, reflect racial differences without considering other, possibly significant, predictors [8]. Frequency counts for supraumbilical port placement and t tests were used to describe anatomical differences between those women who required changes in port placement vs those who did not. In addition, logistic regression was used to examine the odds of requiring adjustments to port placement based on anatomical measurement. In all statistical comparisons, p ,.05 was considered significant. Results Fifty-six white and 22 African American women were enrolled. White women were significantly older (mean [SD], 55.4 [12.7] years vs 43.6 [12.7] years; p 5 .005), and African American women were significantly heavier (BMI, 35.3 [9.3] vs 27.6 [6.12]; p 5 .001). The demographic variables and mean value of each abdominal wall dimension according to racial group are given in Table 1. Surgical procedures performed included 26 sacrocolpopexies, 30 supracervical hysterectomies with cervicosacropexy, and 18 total robotic hysterectomies. All procedures were completed robotically without significant arm interference. In the multiple linear regression model, the relationships between abdominal wall measurements and demographic variables were as follows: for the distance between the anterior superior iliac crests, there were no effects of age (p 5 .95) or race (p 5 .98); however, BMI was significantly associated (p ,.001). Accounting for age and race, every unit increase in BMI was associated with an increase of 0.74 cm in the horizontal lower abdominal dimension. For the distance between the symphysis pubis and the umbilicus (lower vertical abdomen), there were significant effects of BMI (p ,.001) and race (p 5 .006). Every unit increase in BMI was associated with an increase of 0.18 cm in the lower abdomen, irrespective of race. White women had significantly longer lower vertical dimensions (16.51 cm; 95% confidence interval [CI], 16.5–17.6) compared with Table 1
Demographic and abdominal wall dimensions according to race* Race Variable
Black (n 5 22)
White (n 5 52)
p Value
Age, yr BMI kg/m ASIS to ASIS SP to Umb Umb to Xyp Ratio of bottom to top Ratio of length to width
43.68 (12.7) 35.33 (9.32) 33.77 (6.84) 16.25 (2.58) 21.89 (3.60) 0.76 (0.14) 1.16 (0.18)
55.44 (12.7) 27.67 (6.12) 28.17 (7.73) 16.51 (2.46) 18.84 (3.43) 0.90 (0.18) 1.29 (0.20)
.005 .001 .004 .68 .009 .002 .008
ASIS to ASIS 5 distance between anterior superior iliac crests; BMI 5 body mass index, calculated as weight in kilograms divided by height in meters squared; Sp to Umb 5 distance between symphysis pubis and umbilicus; Umb to Xyp 5 distance between umbilicus and xiphoid process. * Values are given as mean (SD).
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Abdominal Wall Anatomy and Port Placement in Women Undergoing Robotic Gynecologic Surgery
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The ratio of the bottom to top half of the abdomen was significantly affected by race (p 5 .002) and age (p 5 .008) but not BMI (p 5 .07). White women had significantly higher ratios of bottom to top compared with African American women (0.90; CI, 0.85–0.95 and 0.75; 95% CI, 0.67–0.82, respectively; Fig. 1), and increase in age was associated with a decrease in this ratio. The ratio of length to width was affected only by BMI (p 5 .001), and for every unit increase in BMI, the ratio of length to width decreased by 0.01. Adjustments to port placement above the umbilicus were made in 44 of the 74 women (59.5%), and these adjustments were similar for both races (59.1% of African American women and 59.6% of white women). Women who required supraumbilical port placement had a significantly shorter mean (SD) distance between the symphysis pubis and the umbilicus (14.99 [1.36] vs 18.55 [2.21]; p ,.001), lower mean BMI (27.33 [5.93] vs 33.79 [9.06]; p 5 .001), and shorter ratios of bottom to top half of the abdomen (0.80 [0.14] vs 0.94 [0.21]; p 5 .003) (Table 2). There was a 2.3-cm difference between the 95% CIs for the distance between the symphysis pubis and the umbilicus in women who required adjustment (95% CI, 14.57–15.40) vs those who did not (95% CI, 17.72–19.38) (Fig. 2). Using stepwise procedures, the distance between the symphysis pubis and the umbilicus was the most and only significant predictor remaining in the model for the need to change port placement (receiver operating characteristic area under the curve, 0.96). Fig. 1. Model estimated lengths and ratios, with 95% confidence intervals, according to race after adjustment for age and body mass index.
African American women (16.25; 95% CI, 14.0–15.9), with a mean difference of 2.10 cm (Fig. 1). Age was not significantly associated (p 5 .06) with the distance between the symphysis pubis and the umbilicus. For the distance between the umbilicus and the xiphoid process (upper abdomen), there were significant effects of BMI (p ,.001) and age (p 5 .03) but not race (p 5 .13). Every unit increase in BMI was associated with an increase of 0.33 cm, and for each additional year of age, the dimension of the upper abdomen was 0.06 cm longer.
Discussion The results of the present study demonstrate significant variability in the relative dimensions of the abdominal wall in women undergoing robotic gynecologic surgery, with a corresponding effect on robotic port placement. Of women with a mean distance of less than 16 cm from the symphysis pubis to the umbilicus, 100% required port placement above the umbilicus. While much of the observed variability was attributable to BMI, race was significantly associated with lower abdominal dimensions, and age was significantly associated with upper abdominal dimensions. It is logical that as a woman ages and loses abdominal muscle tone, the
Table 2
Abdominal wall measurements and supraumbilical port placement No change in port placement (n 5 30)
Change in port placement (n 5 44)
Difference in mean between groups
Variable
Mean
SD
Mean
SD
Mean difference
SD
p Value
Age BMI ASIS to ASIS Sp to Umb Umb to Xyp Ratio of bottom to top Ratio of length to width
47.67 33.79 32.43 18.55 20.55 0.94 1.26
13.13 9.06 9.88 2.22 4.08 0.21 0.22
54.86 27.33 28.07 14.99 19.19 0.80 1.25
13.50 5.93 5.59 1.36 3.40 0.14 0.19
27.20 6.46 4.37 3.56 1.36 0.13 0.01
13.35 7.35 7.61 1.76 3.69 0.17 0.21
.03 .03 .001 ,.001 .13 .003 .78
ASIS to ASIS 5 distance between anterior superior iliac crests; Sp to Umb 5 distance between symphysis pubis and umbilicus; Umb to Xyp 5 distance between umbilicus and xiphoid process; BMI 5 body mass index, calculated as weight in kilograms divided by height in meters squared.
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Journal of Minimally Invasive Gynecology, Vol 17, No 5, September/October 2010
Fig. 2. Ninety-five percent confidence intervals for change in port placement to a supraumbilical site. A mean difference of 2.3 cm existed between women who required supraunbilical port placement vs those who did not.
umbilicus may sag and assume a relatively lower position on the abdominal wall. This would correspond with a longer mean distance from the umbilicus to the xiphoid process and decreasing ratio of lower to upper abdominal dimensions. A rational explanation for our observed racial differences in lower abdominal dimensions may also exist based on observations of significant ethnic variability in pelvic structure. In an anthropologic study from the University of Michigan, pelvises from age-matched African American women and European American women were compared. After controlling for height, African American women had a 5.1% smaller pelvic floor area compared with European American women. This was attributable to a 10.4% smaller posterior area, whereas the anterior areas were similar [9]. Similar results were reported from studies using magnetic resonance imaging in women of varying race/ethnicity. White women were consistently noted to have a larger levator hiatus and bony pelvis compared with nonwhite women [10–12]. Smaller pelvises could, in theory, be associated with relatively shorter dimensions from the symphysis pubis to the umbilicus. The clinical implications of our study findings are significant. When performing robotic surgery, careful attention must be made to the location of the umbilicus in reference to the symphysis pubis because a distance less than 16 cm will likely require supraumbilical port placement. Robotic surgeons, particularly those just adopting this technology, must be aware that in many women, the relative dimensions of the upper abdomen are much larger than those of the lower abdomen, and port placement above the umbilicus may be routine. Patients should be counseled about this preoperatively because cosmetic implications may exist. A potential limitation of the present study includes the absence of data about the relative dimensions of the abdominal wall after insufflation of the peritoneal cavity, which could have a significant effect on appropriate port placement. Abdominal wall elasticity could have a more profound effect on robotic port placement than the actual position of the umbilicus. In our clinical experience, however, regardless of the ease of abdominal distention, placement of the camera
through the umbilicus in women with short lower abdominal dimensions remains problematic. A second limitation is our limited sample size of African American women. Because, to our knowledge, no published data exist regarding ethnic variability in abdominal wall anatomy, we were not able to perform an accurate power calculation to verify the potential effect of race. It is possible that selection bias resulted in our observed ethnic differences; however, because all eligible women were enrolled, this was minimized. In conclusion, women undergoing robotic surgery to treat benign gynecologic conditions demonstrated significant variability in the relative dimensions of the abdominal wall, and individual consideration of this anatomy was paramount in the successful completion of the planned procedure. While the umbilicus serves as a technically and cosmetically appealing site of entry, it may not be appropriately situated on the abdominal wall to facilitate a robotic procedure. Gynecologic surgeons must extend their expertise to placing robotic ports in the upper abdomen in women with limited lower abdominal dimensions.
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