- Email: [email protected]
The Presacral Space and its Impact on Sacral Neuromodulator Implantation
Voiding Dysfunction The Presacral Space and its Impact on Sacral Neuromodulator Implantation Nicole Saint Clair,* Sarah Hamilton Boyles, Amanda Clark, S. Renee Edwards, Mary Anna Denman and W. Thomas Gregory From the Oregon Health & Science University, Portland, Oregon
Purpose: We describe the presacral space and its potential impact on sacral neuromodulator implantation and bowel injury. Materials and Methods: Parasagittal images containing bilateral sacral foramina (S2–S4) were examined on 45 pelvic magnetic resonance images. Images were excluded from analysis if they were poor quality or had any history causing distortion of normal anatomy. We measured the natural angle between the foramina and the dorsal skin to approximate the needle angulation during neuromodulator electrode placement. Using these angles we measured the distance from the skin to any bowel (D1), the skin to the dorsal sacrum (D2) and then calculated the distance from the dorsal sacrum to any bowel (D3). Results: Mean subject age was 45 years (range 19 to 78) and body mass index was 27.9 kg/m2 (range 18.6 to 56.2). At S3 the mean foraminal angle and D3 were 46 ⫾ 8.4 degrees and 27.4 ⫾ 11.7 mm, respectively. Increasing age was moderately correlated to widening D3 at each foramina (r ⫽ 0.3, Pearson’s p ⬍0.05). Body mass index did not consistently vary with D3 at any foramina. Conclusions: Our measurements suggest that the presacral space can be expected to be approximately 27 mm at the level of S3 where the neuromodulator electrode is implanted. It is possible to encounter bowel while performing this implantation using standard techniques and equipment. We recommend the standard use of fluoroscopy during placement. Key Words: humans; electrodes, implanted; urination disorders/therapy; urinary incontinence, urge/surgery; electric stimulation therapy/instrumentation
space risks bowel injury. The FDA Center for Devices and Radiological Health Manufacturer and User Facility Device Experience (MAUDE) Database yielded 2 reports of bowel complications. One report involved the lead found passed within a stool the day following implantation and the other was of spontaneous lead extrusion from the rectum.6 No information was provided regarding implantation technique or patient medical history. Of previous studies measuring the presacral space the majority used lateral x-ray views with barium enemas and used the boundary of the ventral surface of the sacrum to the posterior wall of the rectum.7–11 More recent studies have used computerized tomography and MRI for evaluation.12,13 A study by Oto et al assessing sagittal MRI described median midline widths of the presacral space at the level of S1, S2 and S3.13 To our knowledge there are no studies that examine the presacral space in the region of the foramina. These studies are not directly applicable to InterStim placement due to the midline location of the measurement and may underestimate or overestimate the space more laterally. In this study we measured the size of the presacral space at the parasagittal foraminal locations, thereby establishing a reference for use in InterStim placement.
he InterStim® sacral neurostimulator has been FDA approved for use in the United States since 1997, and is used to treat a variety of urinary dysfunctions and pelvic pain syndromes. Medtronic reports more than 25,000 devices have been implanted since approval.1 Several studies have confirmed its efficacy and safety as a treatment option.2– 4 The InterStim device is implanted by threading an electrode wire with a tined lead through a needle introducer to lie along the S3 nerve root. The 2 available introducer needle sizes are 3.5 and 5 inches. Traditionally the introducer is placed with the use of bony landmarks. Nerve stimulation and subsequent bellows reflex are used to confirm placement in the S3 foramen. Fluoroscopy can be used to facilitate lead placement.5 By demarcating the bony structures before introducer insertion the initial placement can be outlined more precisely (figs. 1 and 2). In addition, after entry into the spinal foramen lead depth can be accurately adjusted using the radiopaque markers on the tined lead. Variation in foramen structure among patients can result in placement of the introducer into the presacral space and beyond. Increasing depth of placement beyond the presacral
T
Submitted for publication January 17, 2008. * Correspondence: Department of Obstetrics and Gynecology, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, Oregon 97239 (telephone: 503-494-3106; FAX: 503-4945680; e-mail: [email protected]).
METHODS To measure the lateral presacral space at the location of the sacral foramina we designed a case study using MRI technology. Pelvic T2-weighted fast spin echo MRIs were evalu-
For another article on a related topic see page 1173.
0022-5347/08/1803-0988/0 THE JOURNAL OF UROLOGY® Copyright © 2008 by AMERICAN UROLOGICAL ASSOCIATION
988
Vol. 180, 988-991, September 2008 Printed in U.S.A. DOI:10.1016/j.juro.2008.05.032
PRESACRAL SPACE AND SACRAL NEUROMODULATOR IMPLANTATION
989
FIG. 1. Bony landmarks demarcated for insertion
ated in the sagittal view. Measurements were taken at S2, S3 and S4 on the right and left sides. The images used for measurement were the most medial slice available that included a clear view of the foramen. In actual practice the site on the skin where the needle is placed or the starting skin point is blind to the angle of the sacral foramina. To standardize our measurements the starting skin point was chosen to mimic an idealized needle course that would pass through the center of the foramen and mirror the natural angle of the foramen. That natural angle was recorded along with a minimum and maximum angle that would pass through the foramen from the same starting skin point. Distance measurements were made using the natural angle of the foramen, and included distance from the skin to the bowel or first presenting abdominal organ if bowel was not visible (D1) and distance from skin to the dorsal surface of the sacrum (D2). The distance from the dorsal sacrum to the presenting organ (D3) was then calculated by subtracting D2 from D1 (fig. 3). If we assume a significance of 0.05, power of 0.8, and state that the mean distance between the posterior aspect of the rectum and the ventral aspect of the sacrum is 10 mm with
FIG. 3. Schematic of measurements. Foramina angle is shown in yellow. Distance from skin to dorsal sacrum (D2) is shown in blue. Distance from skin to posterior rectum (D1) is shown in red. Presacral space (D3) is calculated as D1 ⫺ D2.
a standard deviation of 4 mm, 34 patients would need to be sampled to determine if the mean was 20% discordant with the null hypothesis. Pelvic MRI studies were reviewed using a picture archiving and communication system in a retrograde fashion beginning with the most recent and continuing back in time in 6-month increments until we achieved our planned sample size. Radiologist final diagnoses and review of each subject medical record were used to exclude inappropriate studies from analysis. Studies were excluded if the uterus was enlarged (greater than 10 ⫻ 8 ⫻ 6 cm) or if evidence of pelvic disease was present. Subjects were also excluded from analysis if they had a history of bowel surgery, bowel disease, prior pelvic irradiation, or spinal surgery or anatomical abnormality because it has been previously described that inflammatory, neoplastic or radiation related changes can artificially widen the presacral space. Patients with a history of benign hysterectomy were included in study as these women represent a common subset of the urogynecological patient population. All data were collected and analyzed using SPSS® v. 11.0. RESULTS
FIG. 2. Fluoroscopic confirmation of lead placement through S3 foramen.
We reviewed 45 MRIs. Of these 39 were of females (87%). Mean patient age was 45 years with a range of 19 to 78. BMI data were collected from patient charts as close as possible to the date of study. Mean BMI was 27.9 ⫾ 7.9 kg/m2 with a range of 18.6 to 56.2. Within our population the indications for MRI were varied (table 1). Of the studies ordered for evaluation of malignancy none revealed evidence of spread to surrounding structures. For the S3 foramina mean measured D3 was 27.4 mm. There was no significant difference between left and right side measurements at any level, and these were combined to
990
PRESACRAL SPACE AND SACRAL NEUROMODULATOR IMPLANTATION TABLE 1. Indications for MRI
TABLE 3. BMI and measurement correlations No. Participating Studies
Evaluation of malignancy Pelvic pain Thrombosis, vascular concerns or varicosities Dysmenorrhea or menometrorrhagia Evaluation for possible uterine anomaly Suspected fibroid or evaluation for uterine artery embolization Evaluation of hernia Followup of previously abnormal imaging study Abnormal physical examination Possible enterovaginal fistula
13 7 7 7 2 2 2 2 2 1
determine means and standard deviations. The minimum D3 at S3 was 10 mm. The remainder of the mean (and standard deviation) measured distances and angles is summarized in table 2. We found a positive correlation between BMI, and length of D1 and D2 at all sacral levels (table 3). However, there was no correlation between BMI and D3. DISCUSSION Our findings uniquely characterize the presacral space near the S2–S4 foramina in the lateral position relevant to InterStim placement. It is clear from our measurements and previous reports that under common circumstances it is possible to place an InterStim trocar or needle through the presacral space and encounter the bowel or other intraabdominal organs. Knowing now that the width of the presacral space is independent of patient BMI at a lateral position, we can be somewhat confident that once we encounter the dorsal sacrum during placement there should be a minimum additional 1 cm space before we are at risk for intra-abdominal organ injury in a patient without confounding pathology. Our results suggest a presacral space larger than that previously reported. This is due to a notable difference in our study compared to others in that we used the dorsal surface of the sacrum as the posterior marker as opposed to the ventral surface. The decision to use this parameter was made because the dorsal surface of the sacrum is a useful and easily detected landmark in InterStim placement and, thus, is more clinically relevant. It would be expected then that this strategy would yield larger results. Oto et al assessed sagittal MRI described median midline widths of the presacral space at the level of S1, S2 and S3 of 16.2, 14.9 and 13.0 mm for men and 11.9, 11.2 and 10.6 mm for women, respectively.13 Other studies have also suggested the presacral space to be larger in men than in women in the midline.11 Our study was not designed to evaluate for a gender specific comparison. In addition, the
BMI (r ⫽) S2, S2, S2, S3, S3, S3, S4, S4, S4,
D1 D2 D3 D1 D2 D3 D1 D2 D3
0.65 0.66 0.24 0.58 0.60 0.21 0.58 0.51 0.36
study was not powered to evaluate age related differences, although it has also been described that individuals older than 46 years may have an enlarged presacral space without accompanying pathology compared to their younger counterparts.9 Previous studies have not shown a correlation between BMI and presacral space, which is in line with our finding of a lack of correlation between BMI and D3. Medtronic recommends initially inserting the InterStim introducer at a 60-degree angle to the skin surface.14 As previously stated we evaluated the natural angle of the foramen from our chosen point of entry as well as the minimum and maximum angle that could pass through the foramen from the same point on the skin. From this we yielded angle measurements that were more acute than the recommended 60 degrees, although there was a large variation from subject to subject. Our study does have several limitations. The MRIs that we used are of patients in a supine position. When the electrode is implanted the patients are prone. This difference can affect the width of the presacral space due to gravitational pull drawing the bowel away from the sacrum in the prone position and, thus, possibly yielding a larger width. Prone patients are often flexed during positioning and this can affect the insertion angle. Adding further variability to the insertion angle would be the location of the starting skin point. We have the benefit of being able to see the foramen and its angle to select the starting skin point for this study whereas this would not be an option in actual practice. Some of these limitations could potentially be addressed in a prospective MRI study with patients positioned in a manner similar to surgical positioning. CONCLUSIONS While it is generally a commonly accepted practice, based on our results we recommend that fluoroscopy be used to aid in all InterStim placements. Preoperative bowel preparation could also decrease bowel distention. However, additional studies are needed to assess if this would provide a clinical benefit.
Abbreviations and Acronyms TABLE 2. Mean distances and angles
D1 (mm skin to organ) D2 (mm skin to dorsal sacrum) D3 (mm presacral space)* Mean degrees natural angle Rounded to the nearest tenth. * Dorsal sacrum to organ.
S2
S3
S4
87.8 ⫾ 24.6 55.8 ⫾ 19.6 33.5 ⫾ 12.2 40.6 ⫾ 8.7
67.3 ⫾ 20.8 40.3 ⫾ 13 27.4 ⫾ 11.7 46 ⫾ 8.4
58.5 ⫾ 21 35.5 ⫾ 14.3 22.8 ⫾ 11.4 45.1 ⫾ 14.4
BMI ⫽ body mass index FDA ⫽ Food and Drug Administration MRI ⫽ magnetic resonance imaging REFERENCES 1. http://www.medtronic.com/physician/interstim/index.html. 2. Siegel SW, Catanzaro F, Dijkema HE, Elhilali MM, Fowler CJ, Gajewski JB et al: Long-term results of a multicenter study
PRESACRAL SPACE AND SACRAL NEUROMODULATOR IMPLANTATION
3.
4.
5.
6. 7.
on sacral nerve stimulation for treatment of urinary urge incontinence, urgency-frequency, and retention. Urology 2000; 56: 87. Hassouna MM, Siegel SW, Nÿeholt AA, Elhilali MM, van Kerrebroeck PE, Das AK et al: Sacral neuromodulation in the treatment of urgency-frequency symptoms: a multicenter study on efficacy and safety. J Urol 2000; 163: 1849. van Kerrebroeck PE, van Voskuilen AC, Heesakkers JP, Lycklama a Nijholt AA, Siegel S, Jonas U et al: Results of sacral neuromodulation therapy for urinary voiding dysfunction: outcomes of a prospective, worldwide clinical study. J Urol 2007; 178: 2029. Chai TC and Mamo GJ: Modified techniques of S3 foramen localization and lead implantation in S3 neuromodulation. Urology 2001; 58: 786. http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfMAUDE/ search.cfm. Teplick SK, Stark P, Clark RE, Metz JR and Shapiro JH: The retrorectal space. Clin Radiol 1978; 29: 177.
8.
9. 10.
11. 12.
13.
14.
991
Alp MH, Sage MR and Grant AK: The significance of widening of the presacral space at contrast radiography in inflammatory bowel disease. Aust N Z J Surg 1978; 48: 175. Kattan KR and King AY: Presacral space revisited. AJR Am J Roentgenol 1979; 132: 437. Beneventano TC, Frager DD and Wolf EL: The widened retrorectal space: some radiographic-clinical considerations. Mt Sinai J Med 1984; 51: 467. Akamaguna AI and Odita JC: Width of the presacral space in Nigerian adults. Gastrointest Radiol 1986; 11: 370. Crommelynck M, Lampaert A, De Rycke D, De Feyter I, Kunnen M and Van de Velde E: The retrorectal space reviewed by CT. J Belge Radiol 1988; 71: 356. Oto A, Peynircioglu B, Eryilmaz M, Besim A, Sürücü HS and Celik HH: Determination of the width of the presacral space on magnetic resonance imaging. Clin Anat 2004; 17: 14. Chai TC: Surgical techniques of sacral implantation. Urol Clin North Am 2005; 32: 27.
Purpose: We describe the presacral space and its potential impact on sacral neuromodulator implantation and bowel injury. Materials and Methods: Parasagittal images containing bilateral sacral foramina (S2–S4) were examined on 45 pelvic magnetic resonance images. Images were excluded from analysis if they were poor quality or had any history causing distortion of normal anatomy. We measured the natural angle between the foramina and the dorsal skin to approximate the needle angulation during neuromodulator electrode placement. Using these angles we measured the distance from the skin to any bowel (D1), the skin to the dorsal sacrum (D2) and then calculated the distance from the dorsal sacrum to any bowel (D3). Results: Mean subject age was 45 years (range 19 to 78) and body mass index was 27.9 kg/m2 (range 18.6 to 56.2). At S3 the mean foraminal angle and D3 were 46 ⫾ 8.4 degrees and 27.4 ⫾ 11.7 mm, respectively. Increasing age was moderately correlated to widening D3 at each foramina (r ⫽ 0.3, Pearson’s p ⬍0.05). Body mass index did not consistently vary with D3 at any foramina. Conclusions: Our measurements suggest that the presacral space can be expected to be approximately 27 mm at the level of S3 where the neuromodulator electrode is implanted. It is possible to encounter bowel while performing this implantation using standard techniques and equipment. We recommend the standard use of fluoroscopy during placement. Key Words: humans; electrodes, implanted; urination disorders/therapy; urinary incontinence, urge/surgery; electric stimulation therapy/instrumentation
space risks bowel injury. The FDA Center for Devices and Radiological Health Manufacturer and User Facility Device Experience (MAUDE) Database yielded 2 reports of bowel complications. One report involved the lead found passed within a stool the day following implantation and the other was of spontaneous lead extrusion from the rectum.6 No information was provided regarding implantation technique or patient medical history. Of previous studies measuring the presacral space the majority used lateral x-ray views with barium enemas and used the boundary of the ventral surface of the sacrum to the posterior wall of the rectum.7–11 More recent studies have used computerized tomography and MRI for evaluation.12,13 A study by Oto et al assessing sagittal MRI described median midline widths of the presacral space at the level of S1, S2 and S3.13 To our knowledge there are no studies that examine the presacral space in the region of the foramina. These studies are not directly applicable to InterStim placement due to the midline location of the measurement and may underestimate or overestimate the space more laterally. In this study we measured the size of the presacral space at the parasagittal foraminal locations, thereby establishing a reference for use in InterStim placement.
he InterStim® sacral neurostimulator has been FDA approved for use in the United States since 1997, and is used to treat a variety of urinary dysfunctions and pelvic pain syndromes. Medtronic reports more than 25,000 devices have been implanted since approval.1 Several studies have confirmed its efficacy and safety as a treatment option.2– 4 The InterStim device is implanted by threading an electrode wire with a tined lead through a needle introducer to lie along the S3 nerve root. The 2 available introducer needle sizes are 3.5 and 5 inches. Traditionally the introducer is placed with the use of bony landmarks. Nerve stimulation and subsequent bellows reflex are used to confirm placement in the S3 foramen. Fluoroscopy can be used to facilitate lead placement.5 By demarcating the bony structures before introducer insertion the initial placement can be outlined more precisely (figs. 1 and 2). In addition, after entry into the spinal foramen lead depth can be accurately adjusted using the radiopaque markers on the tined lead. Variation in foramen structure among patients can result in placement of the introducer into the presacral space and beyond. Increasing depth of placement beyond the presacral
T
Submitted for publication January 17, 2008. * Correspondence: Department of Obstetrics and Gynecology, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, Oregon 97239 (telephone: 503-494-3106; FAX: 503-4945680; e-mail: [email protected]).
METHODS To measure the lateral presacral space at the location of the sacral foramina we designed a case study using MRI technology. Pelvic T2-weighted fast spin echo MRIs were evalu-
For another article on a related topic see page 1173.
0022-5347/08/1803-0988/0 THE JOURNAL OF UROLOGY® Copyright © 2008 by AMERICAN UROLOGICAL ASSOCIATION
988
Vol. 180, 988-991, September 2008 Printed in U.S.A. DOI:10.1016/j.juro.2008.05.032
PRESACRAL SPACE AND SACRAL NEUROMODULATOR IMPLANTATION
989
FIG. 1. Bony landmarks demarcated for insertion
ated in the sagittal view. Measurements were taken at S2, S3 and S4 on the right and left sides. The images used for measurement were the most medial slice available that included a clear view of the foramen. In actual practice the site on the skin where the needle is placed or the starting skin point is blind to the angle of the sacral foramina. To standardize our measurements the starting skin point was chosen to mimic an idealized needle course that would pass through the center of the foramen and mirror the natural angle of the foramen. That natural angle was recorded along with a minimum and maximum angle that would pass through the foramen from the same starting skin point. Distance measurements were made using the natural angle of the foramen, and included distance from the skin to the bowel or first presenting abdominal organ if bowel was not visible (D1) and distance from skin to the dorsal surface of the sacrum (D2). The distance from the dorsal sacrum to the presenting organ (D3) was then calculated by subtracting D2 from D1 (fig. 3). If we assume a significance of 0.05, power of 0.8, and state that the mean distance between the posterior aspect of the rectum and the ventral aspect of the sacrum is 10 mm with
FIG. 3. Schematic of measurements. Foramina angle is shown in yellow. Distance from skin to dorsal sacrum (D2) is shown in blue. Distance from skin to posterior rectum (D1) is shown in red. Presacral space (D3) is calculated as D1 ⫺ D2.
a standard deviation of 4 mm, 34 patients would need to be sampled to determine if the mean was 20% discordant with the null hypothesis. Pelvic MRI studies were reviewed using a picture archiving and communication system in a retrograde fashion beginning with the most recent and continuing back in time in 6-month increments until we achieved our planned sample size. Radiologist final diagnoses and review of each subject medical record were used to exclude inappropriate studies from analysis. Studies were excluded if the uterus was enlarged (greater than 10 ⫻ 8 ⫻ 6 cm) or if evidence of pelvic disease was present. Subjects were also excluded from analysis if they had a history of bowel surgery, bowel disease, prior pelvic irradiation, or spinal surgery or anatomical abnormality because it has been previously described that inflammatory, neoplastic or radiation related changes can artificially widen the presacral space. Patients with a history of benign hysterectomy were included in study as these women represent a common subset of the urogynecological patient population. All data were collected and analyzed using SPSS® v. 11.0. RESULTS
FIG. 2. Fluoroscopic confirmation of lead placement through S3 foramen.
We reviewed 45 MRIs. Of these 39 were of females (87%). Mean patient age was 45 years with a range of 19 to 78. BMI data were collected from patient charts as close as possible to the date of study. Mean BMI was 27.9 ⫾ 7.9 kg/m2 with a range of 18.6 to 56.2. Within our population the indications for MRI were varied (table 1). Of the studies ordered for evaluation of malignancy none revealed evidence of spread to surrounding structures. For the S3 foramina mean measured D3 was 27.4 mm. There was no significant difference between left and right side measurements at any level, and these were combined to
990
PRESACRAL SPACE AND SACRAL NEUROMODULATOR IMPLANTATION TABLE 1. Indications for MRI
TABLE 3. BMI and measurement correlations No. Participating Studies
Evaluation of malignancy Pelvic pain Thrombosis, vascular concerns or varicosities Dysmenorrhea or menometrorrhagia Evaluation for possible uterine anomaly Suspected fibroid or evaluation for uterine artery embolization Evaluation of hernia Followup of previously abnormal imaging study Abnormal physical examination Possible enterovaginal fistula
13 7 7 7 2 2 2 2 2 1
determine means and standard deviations. The minimum D3 at S3 was 10 mm. The remainder of the mean (and standard deviation) measured distances and angles is summarized in table 2. We found a positive correlation between BMI, and length of D1 and D2 at all sacral levels (table 3). However, there was no correlation between BMI and D3. DISCUSSION Our findings uniquely characterize the presacral space near the S2–S4 foramina in the lateral position relevant to InterStim placement. It is clear from our measurements and previous reports that under common circumstances it is possible to place an InterStim trocar or needle through the presacral space and encounter the bowel or other intraabdominal organs. Knowing now that the width of the presacral space is independent of patient BMI at a lateral position, we can be somewhat confident that once we encounter the dorsal sacrum during placement there should be a minimum additional 1 cm space before we are at risk for intra-abdominal organ injury in a patient without confounding pathology. Our results suggest a presacral space larger than that previously reported. This is due to a notable difference in our study compared to others in that we used the dorsal surface of the sacrum as the posterior marker as opposed to the ventral surface. The decision to use this parameter was made because the dorsal surface of the sacrum is a useful and easily detected landmark in InterStim placement and, thus, is more clinically relevant. It would be expected then that this strategy would yield larger results. Oto et al assessed sagittal MRI described median midline widths of the presacral space at the level of S1, S2 and S3 of 16.2, 14.9 and 13.0 mm for men and 11.9, 11.2 and 10.6 mm for women, respectively.13 Other studies have also suggested the presacral space to be larger in men than in women in the midline.11 Our study was not designed to evaluate for a gender specific comparison. In addition, the
BMI (r ⫽) S2, S2, S2, S3, S3, S3, S4, S4, S4,
D1 D2 D3 D1 D2 D3 D1 D2 D3
0.65 0.66 0.24 0.58 0.60 0.21 0.58 0.51 0.36
study was not powered to evaluate age related differences, although it has also been described that individuals older than 46 years may have an enlarged presacral space without accompanying pathology compared to their younger counterparts.9 Previous studies have not shown a correlation between BMI and presacral space, which is in line with our finding of a lack of correlation between BMI and D3. Medtronic recommends initially inserting the InterStim introducer at a 60-degree angle to the skin surface.14 As previously stated we evaluated the natural angle of the foramen from our chosen point of entry as well as the minimum and maximum angle that could pass through the foramen from the same point on the skin. From this we yielded angle measurements that were more acute than the recommended 60 degrees, although there was a large variation from subject to subject. Our study does have several limitations. The MRIs that we used are of patients in a supine position. When the electrode is implanted the patients are prone. This difference can affect the width of the presacral space due to gravitational pull drawing the bowel away from the sacrum in the prone position and, thus, possibly yielding a larger width. Prone patients are often flexed during positioning and this can affect the insertion angle. Adding further variability to the insertion angle would be the location of the starting skin point. We have the benefit of being able to see the foramen and its angle to select the starting skin point for this study whereas this would not be an option in actual practice. Some of these limitations could potentially be addressed in a prospective MRI study with patients positioned in a manner similar to surgical positioning. CONCLUSIONS While it is generally a commonly accepted practice, based on our results we recommend that fluoroscopy be used to aid in all InterStim placements. Preoperative bowel preparation could also decrease bowel distention. However, additional studies are needed to assess if this would provide a clinical benefit.
Abbreviations and Acronyms TABLE 2. Mean distances and angles
D1 (mm skin to organ) D2 (mm skin to dorsal sacrum) D3 (mm presacral space)* Mean degrees natural angle Rounded to the nearest tenth. * Dorsal sacrum to organ.
S2
S3
S4
87.8 ⫾ 24.6 55.8 ⫾ 19.6 33.5 ⫾ 12.2 40.6 ⫾ 8.7
67.3 ⫾ 20.8 40.3 ⫾ 13 27.4 ⫾ 11.7 46 ⫾ 8.4
58.5 ⫾ 21 35.5 ⫾ 14.3 22.8 ⫾ 11.4 45.1 ⫾ 14.4
BMI ⫽ body mass index FDA ⫽ Food and Drug Administration MRI ⫽ magnetic resonance imaging REFERENCES 1. http://www.medtronic.com/physician/interstim/index.html. 2. Siegel SW, Catanzaro F, Dijkema HE, Elhilali MM, Fowler CJ, Gajewski JB et al: Long-term results of a multicenter study
PRESACRAL SPACE AND SACRAL NEUROMODULATOR IMPLANTATION
3.
4.
5.
6. 7.
on sacral nerve stimulation for treatment of urinary urge incontinence, urgency-frequency, and retention. Urology 2000; 56: 87. Hassouna MM, Siegel SW, Nÿeholt AA, Elhilali MM, van Kerrebroeck PE, Das AK et al: Sacral neuromodulation in the treatment of urgency-frequency symptoms: a multicenter study on efficacy and safety. J Urol 2000; 163: 1849. van Kerrebroeck PE, van Voskuilen AC, Heesakkers JP, Lycklama a Nijholt AA, Siegel S, Jonas U et al: Results of sacral neuromodulation therapy for urinary voiding dysfunction: outcomes of a prospective, worldwide clinical study. J Urol 2007; 178: 2029. Chai TC and Mamo GJ: Modified techniques of S3 foramen localization and lead implantation in S3 neuromodulation. Urology 2001; 58: 786. http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfMAUDE/ search.cfm. Teplick SK, Stark P, Clark RE, Metz JR and Shapiro JH: The retrorectal space. Clin Radiol 1978; 29: 177.
8.
9. 10.
11. 12.
13.
14.
991
Alp MH, Sage MR and Grant AK: The significance of widening of the presacral space at contrast radiography in inflammatory bowel disease. Aust N Z J Surg 1978; 48: 175. Kattan KR and King AY: Presacral space revisited. AJR Am J Roentgenol 1979; 132: 437. Beneventano TC, Frager DD and Wolf EL: The widened retrorectal space: some radiographic-clinical considerations. Mt Sinai J Med 1984; 51: 467. Akamaguna AI and Odita JC: Width of the presacral space in Nigerian adults. Gastrointest Radiol 1986; 11: 370. Crommelynck M, Lampaert A, De Rycke D, De Feyter I, Kunnen M and Van de Velde E: The retrorectal space reviewed by CT. J Belge Radiol 1988; 71: 356. Oto A, Peynircioglu B, Eryilmaz M, Besim A, Sürücü HS and Celik HH: Determination of the width of the presacral space on magnetic resonance imaging. Clin Anat 2004; 17: 14. Chai TC: Surgical techniques of sacral implantation. Urol Clin North Am 2005; 32: 27.