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Image-Based Techniques for Percutaneous Iliosacral Screw Start-Site Localization
Iliosacral (SI) screws remain the standard of care for the vast majority of posterior pelvic ring disruptions.1,2 However, despite their routine use, the procedure remains technically demanding with repeated cases of aberrant screw placement and complications.3,4 Sacral morphology is extremely variable within a patient population and affects accurate placement and trajectory of percutaneous screws.5 Classically, it is taught that the external starting position/landmark is at an intersection point of the greater trochanter and the anterior superior iliac spine (ASIS). While this “one size fits all” approach will certainly help to coordinate a start position, it is our experience that multiple stab incisions are necessary to find the optimal start site. To our knowledge, the most common image-based technique used to guide start-point localization and placement of SI screws begins with drawing a virtual sacrum on the patient’s side, guided by the lateral image.5 This article provides a novel image-based technique to be used with, or as a replacement for, the traditional technique.
Techniques
The patient is brought to the operating room and placed supine on a radiolucent operating table. If the closed reduction of the pelvic ring is successful or can be achieved via anterior manipulation/traction, posterior percutaneous pinning is planned. Either a rolled towel or a bag of saline is used as a bolster and placed midline underneath the sacrum and lumbar spine to help “bump” the pelvis and improve the range of motion for the surgeon’s drill. The patient is brought to the edge of the table when possible (ie, a posterior ring injury requiring fixation from only 1 side) to further enhance drill motion. If bilateral screws are planned, surgeons must be careful not to position 1 side at the expense of screw placement on the contralateral side. Nitrous-based anesthetic agents are avoided, because they may collect in the bowel and obscure good radiographic visualization. Arms are placed perpendicular to the body to facilitate the inlet view. Pre-preparation anteroposterior pelvis, inlet, and outlet views are obtained to assure ability to accurately and safely assess landmarks on all projections, and to mark the C-arm position and angles. This process helps decrease “useless” radiographs obtained during the procedure. Acceptable inlet radiographs show the anterior cortex of the S1 body superimposed on the S2 body. Acceptable outlet radiographs show the superior pubic symphysis at the level of the S2 foramen and visualization of the S1/S2 sacral foramen.6 The patient is then prepared in the standard fashion. Reduction maneuvers are performed and, if acceptable alignment is achieved, posterior percutaneous screw placement begins.
Technique 1
To our knowledge, the most common image-based technique used to guide start-point localization and placement of SI screws begins with drawing a virtual sacrum on the patient’s side using the lateral image. The fluoroscopic machine is set up in a lateral position.5 A free guide wire is superimposed upon the iliac cortical density and anterior sacral slope, which is marked on the skin (Figure 1). The superior portion of S1, as well as the posterior sacral slope, can be marked as well. This process has outlined the sacrum and provides an external landmark for the “safe zone” for screw placement. The operation proceeds in the standard fashion using inlet, outlet, and lateral radiographs. However, the externally drawn sacrum can aid as a reference during guide-pin placement.
Technique 2
This technique takes into account bone anatomy and soft-tissue coverage. It is helpful to think of the abdomen/pelvis as a box. The anterior abdomen represents the top of the box and the lateral buttock represents the side of the box. The corner of the imaginary box is where the abdomen begins to slope down and transitions laterally to become the buttock. This will be referenced as the “down-sloping point” and typically corresponds to the level of the iliac crest (Figure 2).
To begin, a standard cannulated screw guide wire is placed flush on the skin of the abdomen. An inlet fluoroscopy image is taken with the guide pin on the abdomen. Imagine that the resulting image represents the planned screw trajectory (Figure 3A). When the position of the guide wire is deemed adequate, a line is marked on the abdomen, using a pen, directly adjacent to the guide wire. This line represents inlet line 1 (Figure 2). The line must continue laterally until the down-sloping point. The sagittal angle of the imaginary inlet fluoroscopic beam is noted, and a guide wire is placed in the same sagittal orientation flush with the skin on the lateral buttock (Figure 3B). The guide wire must be placed so that it intersects with the first line at the down-sloping point. The skin on the lateral aspect of buttock is marked with a second line, which represents inlet line 2 (Figure 2).
The same process is repeated using an outlet view to create outlet lines 1 and 2 (Figures 4A, 4B). At this point there are 4 lines drawn on the patient (Figure 2). A stab incision is made at the intersection of the 2 lines drawn on the lateral buttock; this represents the skin start point, labeled “start incision” (Figure 2). The procedure continues in standard fashion.
The 4 external reference lines serve multiple purposes. First, the lines mark the true lateral start point for the pin at the level of the skin. This contrasts with the standard technique in which bony landmarks are marked on the skin and the surgeon must estimate a point on the skin that will provide an appropriate trajectory to the bony start point on the ilium. Further, the lines can also be used to reorient the cartesian plane so that adjustments can be isolated to a single plane, ensuring movements only alter the position on a single radiographic view (Figure 5).
Discussion
Despite the widespread use of percutaneous screw placement for posterior pelvic ring injuries, this remains a technically demanding surgery. Recent data suggest patient pelvic anatomy is extremely varied, especially the sacrum.7 Further, screw trajectories vary depending on surgical goals, fracture pattern, and number of screws. Taken together, this implies that there is no perfect universal starting site along the external ilium. Therefore, while classic teaching states to begin screw insertion within the vicinity of the intersection of the greater trochanter and the ASIS, it is our experience that this location is often not ideal.
The inlet, outlet, and lateral radiographs are all vital to assess correct trajectory of the guide pin and drill prior to final screw insertion, but the start site remains a critical step to assure a successful surgical outcome. We present 2 techniques, used together or separately, that allow the surgeon to place the initial guide pin more accurately for percutanous iliosacral screws. Though not specifically examined in this study, we think technique 2 has the potential to save operative time and use less fluoroscopic imaging because a lateral image is not required until later in the case. Technique 2 identifies the start point at the level of the skin. This is in contrast to technique 1, which identifies the desired sacral target and requires a surgeon to select a skin start site that will provide an optimal trajectory towards the desired target. Judging trajectory can be difficult, particularly in obese patients, and technique 2 eliminates this extra variable.
It is also important to consider that criteria-based nonorthogonal imaging is required for percutaneous screw placement. In these cases, it is more difficult to judge trajectory corrections because the fluoroscopic beam cannot guide perpendicular corrections as it can in operations that use orthogonal imaging. Adjustments made perpendicular to the fluoroscopic beam will change trajectory in multiple planes.8 Moreover, because the standard cartesian frame of reference is rotated, understanding the location of the sacrum in space can be especially challenging. When using the first technique, sacral landmarks are delineated, and a virtual sacrum drawn on the patient’s exterior helps with orientation. In the second technique, the ideal pin placement is mapped, and the external reference lines guide uniplanar changes. For example, the line drawn co-planar with the inlet view is essentially marking the sacral slope. Therefore, by following this line, uniplanar changes in the cranial and caudal direction are achieved on the outlet view (Figure 5). Because this line is also in reference to the already known ideal pin placement, ideal pin placement can be maintained in 1 radiographic projection while changing the start site in the appropriate direction. In a similar fashion, the co-planar line identified on the inlet view can be used on the outlet image to affect uniplanar changes in the anteroposterior direction. This technique effectively minimizes disorientation when placing percutaneous SI screws. This can be particularly beneficial when placing screws in the prone position.
Conclusion
We have shown 2 techniques that are routinely used at our institution to help identify an accurate starting position for percutaneous screw placement in posterior pelvic ring injuries. Even experienced traumatologists can more quickly and accurately identify the correct stab incisions leading to more confidently placed screws. Further, we believe understanding the usage of fluoroscopy and the concepts involved in drawing the lines enhance trainees’ comprehension of the complex anatomy of the sacrum.
1. Matta JM, Saucedo T. Internal fixation of pelvic ring fractures. Clin Orthop Relat Res. 1989;242:83-97.
2. Routt ML Jr, Kregor PJ, Simonian PT, Mayo KA. Early results of percutaneous iliosacral screws placed with the patient in the supine position. J Orthop Trauma. 1995;9(3):207-214.
3. Sagi HC, Lindvall EM. Inadvertent intraforaminal iliosacral screw placement despite apparent appropriate positioning on intraoperative fluoroscopy.
J Orthop Trauma. 2005;19(2):130-133.
4. Routt ML Jr, Simonian PT, Mills WJ. Iliosacral screw fixation: early complications of the percutaneous technique. J Orthop Trauma. 1997;11(8):584-589.
5. Routt ML Jr, Simonian PT, Agnew SG, Mann FA. Radiographic recognition of the sacral alar slope for optimal placement of iliosacral screws: a cadaveric and clinical study. J Orthop Trauma. 1996;10(3):171-177.
6. Gardner MJ, Ferrell ED, Nork SE, Segina DN, Routt ML Jr. Percutaneous placement of iliosacral screws without electrodiagnostic monitoring. J Trauma. 2009;66(5):1411-1415.
7. Miller AN, Routt ML Jr. Variations in sacral morphology and implications for iliosacral screw fixation. J Am Acad Orthop Surg. 2012;20(1):8-16.
8. Graves ML, Routt ML. Iliosacral screw placement: are uniplanar changes realistic based on standard fluoroscopic imaging? J Orthop Trauma. 2011;71(1):204-208.
Iliosacral (SI) screws remain the standard of care for the vast majority of posterior pelvic ring disruptions.1,2 However, despite their routine use, the procedure remains technically demanding with repeated cases of aberrant screw placement and complications.3,4 Sacral morphology is extremely variable within a patient population and affects accurate placement and trajectory of percutaneous screws.5 Classically, it is taught that the external starting position/landmark is at an intersection point of the greater trochanter and the anterior superior iliac spine (ASIS). While this “one size fits all” approach will certainly help to coordinate a start position, it is our experience that multiple stab incisions are necessary to find the optimal start site. To our knowledge, the most common image-based technique used to guide start-point localization and placement of SI screws begins with drawing a virtual sacrum on the patient’s side, guided by the lateral image.5 This article provides a novel image-based technique to be used with, or as a replacement for, the traditional technique.
Techniques
The patient is brought to the operating room and placed supine on a radiolucent operating table. If the closed reduction of the pelvic ring is successful or can be achieved via anterior manipulation/traction, posterior percutaneous pinning is planned. Either a rolled towel or a bag of saline is used as a bolster and placed midline underneath the sacrum and lumbar spine to help “bump” the pelvis and improve the range of motion for the surgeon’s drill. The patient is brought to the edge of the table when possible (ie, a posterior ring injury requiring fixation from only 1 side) to further enhance drill motion. If bilateral screws are planned, surgeons must be careful not to position 1 side at the expense of screw placement on the contralateral side. Nitrous-based anesthetic agents are avoided, because they may collect in the bowel and obscure good radiographic visualization. Arms are placed perpendicular to the body to facilitate the inlet view. Pre-preparation anteroposterior pelvis, inlet, and outlet views are obtained to assure ability to accurately and safely assess landmarks on all projections, and to mark the C-arm position and angles. This process helps decrease “useless” radiographs obtained during the procedure. Acceptable inlet radiographs show the anterior cortex of the S1 body superimposed on the S2 body. Acceptable outlet radiographs show the superior pubic symphysis at the level of the S2 foramen and visualization of the S1/S2 sacral foramen.6 The patient is then prepared in the standard fashion. Reduction maneuvers are performed and, if acceptable alignment is achieved, posterior percutaneous screw placement begins.
Technique 1
To our knowledge, the most common image-based technique used to guide start-point localization and placement of SI screws begins with drawing a virtual sacrum on the patient’s side using the lateral image. The fluoroscopic machine is set up in a lateral position.5 A free guide wire is superimposed upon the iliac cortical density and anterior sacral slope, which is marked on the skin (Figure 1). The superior portion of S1, as well as the posterior sacral slope, can be marked as well. This process has outlined the sacrum and provides an external landmark for the “safe zone” for screw placement. The operation proceeds in the standard fashion using inlet, outlet, and lateral radiographs. However, the externally drawn sacrum can aid as a reference during guide-pin placement.
Technique 2
This technique takes into account bone anatomy and soft-tissue coverage. It is helpful to think of the abdomen/pelvis as a box. The anterior abdomen represents the top of the box and the lateral buttock represents the side of the box. The corner of the imaginary box is where the abdomen begins to slope down and transitions laterally to become the buttock. This will be referenced as the “down-sloping point” and typically corresponds to the level of the iliac crest (Figure 2).
To begin, a standard cannulated screw guide wire is placed flush on the skin of the abdomen. An inlet fluoroscopy image is taken with the guide pin on the abdomen. Imagine that the resulting image represents the planned screw trajectory (Figure 3A). When the position of the guide wire is deemed adequate, a line is marked on the abdomen, using a pen, directly adjacent to the guide wire. This line represents inlet line 1 (Figure 2). The line must continue laterally until the down-sloping point. The sagittal angle of the imaginary inlet fluoroscopic beam is noted, and a guide wire is placed in the same sagittal orientation flush with the skin on the lateral buttock (Figure 3B). The guide wire must be placed so that it intersects with the first line at the down-sloping point. The skin on the lateral aspect of buttock is marked with a second line, which represents inlet line 2 (Figure 2).
The same process is repeated using an outlet view to create outlet lines 1 and 2 (Figures 4A, 4B). At this point there are 4 lines drawn on the patient (Figure 2). A stab incision is made at the intersection of the 2 lines drawn on the lateral buttock; this represents the skin start point, labeled “start incision” (Figure 2). The procedure continues in standard fashion.
The 4 external reference lines serve multiple purposes. First, the lines mark the true lateral start point for the pin at the level of the skin. This contrasts with the standard technique in which bony landmarks are marked on the skin and the surgeon must estimate a point on the skin that will provide an appropriate trajectory to the bony start point on the ilium. Further, the lines can also be used to reorient the cartesian plane so that adjustments can be isolated to a single plane, ensuring movements only alter the position on a single radiographic view (Figure 5).
Discussion
Despite the widespread use of percutaneous screw placement for posterior pelvic ring injuries, this remains a technically demanding surgery. Recent data suggest patient pelvic anatomy is extremely varied, especially the sacrum.7 Further, screw trajectories vary depending on surgical goals, fracture pattern, and number of screws. Taken together, this implies that there is no perfect universal starting site along the external ilium. Therefore, while classic teaching states to begin screw insertion within the vicinity of the intersection of the greater trochanter and the ASIS, it is our experience that this location is often not ideal.
The inlet, outlet, and lateral radiographs are all vital to assess correct trajectory of the guide pin and drill prior to final screw insertion, but the start site remains a critical step to assure a successful surgical outcome. We present 2 techniques, used together or separately, that allow the surgeon to place the initial guide pin more accurately for percutanous iliosacral screws. Though not specifically examined in this study, we think technique 2 has the potential to save operative time and use less fluoroscopic imaging because a lateral image is not required until later in the case. Technique 2 identifies the start point at the level of the skin. This is in contrast to technique 1, which identifies the desired sacral target and requires a surgeon to select a skin start site that will provide an optimal trajectory towards the desired target. Judging trajectory can be difficult, particularly in obese patients, and technique 2 eliminates this extra variable.
It is also important to consider that criteria-based nonorthogonal imaging is required for percutaneous screw placement. In these cases, it is more difficult to judge trajectory corrections because the fluoroscopic beam cannot guide perpendicular corrections as it can in operations that use orthogonal imaging. Adjustments made perpendicular to the fluoroscopic beam will change trajectory in multiple planes.8 Moreover, because the standard cartesian frame of reference is rotated, understanding the location of the sacrum in space can be especially challenging. When using the first technique, sacral landmarks are delineated, and a virtual sacrum drawn on the patient’s exterior helps with orientation. In the second technique, the ideal pin placement is mapped, and the external reference lines guide uniplanar changes. For example, the line drawn co-planar with the inlet view is essentially marking the sacral slope. Therefore, by following this line, uniplanar changes in the cranial and caudal direction are achieved on the outlet view (Figure 5). Because this line is also in reference to the already known ideal pin placement, ideal pin placement can be maintained in 1 radiographic projection while changing the start site in the appropriate direction. In a similar fashion, the co-planar line identified on the inlet view can be used on the outlet image to affect uniplanar changes in the anteroposterior direction. This technique effectively minimizes disorientation when placing percutaneous SI screws. This can be particularly beneficial when placing screws in the prone position.
Conclusion
We have shown 2 techniques that are routinely used at our institution to help identify an accurate starting position for percutaneous screw placement in posterior pelvic ring injuries. Even experienced traumatologists can more quickly and accurately identify the correct stab incisions leading to more confidently placed screws. Further, we believe understanding the usage of fluoroscopy and the concepts involved in drawing the lines enhance trainees’ comprehension of the complex anatomy of the sacrum.
Iliosacral (SI) screws remain the standard of care for the vast majority of posterior pelvic ring disruptions.1,2 However, despite their routine use, the procedure remains technically demanding with repeated cases of aberrant screw placement and complications.3,4 Sacral morphology is extremely variable within a patient population and affects accurate placement and trajectory of percutaneous screws.5 Classically, it is taught that the external starting position/landmark is at an intersection point of the greater trochanter and the anterior superior iliac spine (ASIS). While this “one size fits all” approach will certainly help to coordinate a start position, it is our experience that multiple stab incisions are necessary to find the optimal start site. To our knowledge, the most common image-based technique used to guide start-point localization and placement of SI screws begins with drawing a virtual sacrum on the patient’s side, guided by the lateral image.5 This article provides a novel image-based technique to be used with, or as a replacement for, the traditional technique.
Techniques
The patient is brought to the operating room and placed supine on a radiolucent operating table. If the closed reduction of the pelvic ring is successful or can be achieved via anterior manipulation/traction, posterior percutaneous pinning is planned. Either a rolled towel or a bag of saline is used as a bolster and placed midline underneath the sacrum and lumbar spine to help “bump” the pelvis and improve the range of motion for the surgeon’s drill. The patient is brought to the edge of the table when possible (ie, a posterior ring injury requiring fixation from only 1 side) to further enhance drill motion. If bilateral screws are planned, surgeons must be careful not to position 1 side at the expense of screw placement on the contralateral side. Nitrous-based anesthetic agents are avoided, because they may collect in the bowel and obscure good radiographic visualization. Arms are placed perpendicular to the body to facilitate the inlet view. Pre-preparation anteroposterior pelvis, inlet, and outlet views are obtained to assure ability to accurately and safely assess landmarks on all projections, and to mark the C-arm position and angles. This process helps decrease “useless” radiographs obtained during the procedure. Acceptable inlet radiographs show the anterior cortex of the S1 body superimposed on the S2 body. Acceptable outlet radiographs show the superior pubic symphysis at the level of the S2 foramen and visualization of the S1/S2 sacral foramen.6 The patient is then prepared in the standard fashion. Reduction maneuvers are performed and, if acceptable alignment is achieved, posterior percutaneous screw placement begins.
Technique 1
To our knowledge, the most common image-based technique used to guide start-point localization and placement of SI screws begins with drawing a virtual sacrum on the patient’s side using the lateral image. The fluoroscopic machine is set up in a lateral position.5 A free guide wire is superimposed upon the iliac cortical density and anterior sacral slope, which is marked on the skin (Figure 1). The superior portion of S1, as well as the posterior sacral slope, can be marked as well. This process has outlined the sacrum and provides an external landmark for the “safe zone” for screw placement. The operation proceeds in the standard fashion using inlet, outlet, and lateral radiographs. However, the externally drawn sacrum can aid as a reference during guide-pin placement.
Technique 2
This technique takes into account bone anatomy and soft-tissue coverage. It is helpful to think of the abdomen/pelvis as a box. The anterior abdomen represents the top of the box and the lateral buttock represents the side of the box. The corner of the imaginary box is where the abdomen begins to slope down and transitions laterally to become the buttock. This will be referenced as the “down-sloping point” and typically corresponds to the level of the iliac crest (Figure 2).
To begin, a standard cannulated screw guide wire is placed flush on the skin of the abdomen. An inlet fluoroscopy image is taken with the guide pin on the abdomen. Imagine that the resulting image represents the planned screw trajectory (Figure 3A). When the position of the guide wire is deemed adequate, a line is marked on the abdomen, using a pen, directly adjacent to the guide wire. This line represents inlet line 1 (Figure 2). The line must continue laterally until the down-sloping point. The sagittal angle of the imaginary inlet fluoroscopic beam is noted, and a guide wire is placed in the same sagittal orientation flush with the skin on the lateral buttock (Figure 3B). The guide wire must be placed so that it intersects with the first line at the down-sloping point. The skin on the lateral aspect of buttock is marked with a second line, which represents inlet line 2 (Figure 2).
The same process is repeated using an outlet view to create outlet lines 1 and 2 (Figures 4A, 4B). At this point there are 4 lines drawn on the patient (Figure 2). A stab incision is made at the intersection of the 2 lines drawn on the lateral buttock; this represents the skin start point, labeled “start incision” (Figure 2). The procedure continues in standard fashion.
The 4 external reference lines serve multiple purposes. First, the lines mark the true lateral start point for the pin at the level of the skin. This contrasts with the standard technique in which bony landmarks are marked on the skin and the surgeon must estimate a point on the skin that will provide an appropriate trajectory to the bony start point on the ilium. Further, the lines can also be used to reorient the cartesian plane so that adjustments can be isolated to a single plane, ensuring movements only alter the position on a single radiographic view (Figure 5).
Discussion
Despite the widespread use of percutaneous screw placement for posterior pelvic ring injuries, this remains a technically demanding surgery. Recent data suggest patient pelvic anatomy is extremely varied, especially the sacrum.7 Further, screw trajectories vary depending on surgical goals, fracture pattern, and number of screws. Taken together, this implies that there is no perfect universal starting site along the external ilium. Therefore, while classic teaching states to begin screw insertion within the vicinity of the intersection of the greater trochanter and the ASIS, it is our experience that this location is often not ideal.
The inlet, outlet, and lateral radiographs are all vital to assess correct trajectory of the guide pin and drill prior to final screw insertion, but the start site remains a critical step to assure a successful surgical outcome. We present 2 techniques, used together or separately, that allow the surgeon to place the initial guide pin more accurately for percutanous iliosacral screws. Though not specifically examined in this study, we think technique 2 has the potential to save operative time and use less fluoroscopic imaging because a lateral image is not required until later in the case. Technique 2 identifies the start point at the level of the skin. This is in contrast to technique 1, which identifies the desired sacral target and requires a surgeon to select a skin start site that will provide an optimal trajectory towards the desired target. Judging trajectory can be difficult, particularly in obese patients, and technique 2 eliminates this extra variable.
It is also important to consider that criteria-based nonorthogonal imaging is required for percutaneous screw placement. In these cases, it is more difficult to judge trajectory corrections because the fluoroscopic beam cannot guide perpendicular corrections as it can in operations that use orthogonal imaging. Adjustments made perpendicular to the fluoroscopic beam will change trajectory in multiple planes.8 Moreover, because the standard cartesian frame of reference is rotated, understanding the location of the sacrum in space can be especially challenging. When using the first technique, sacral landmarks are delineated, and a virtual sacrum drawn on the patient’s exterior helps with orientation. In the second technique, the ideal pin placement is mapped, and the external reference lines guide uniplanar changes. For example, the line drawn co-planar with the inlet view is essentially marking the sacral slope. Therefore, by following this line, uniplanar changes in the cranial and caudal direction are achieved on the outlet view (Figure 5). Because this line is also in reference to the already known ideal pin placement, ideal pin placement can be maintained in 1 radiographic projection while changing the start site in the appropriate direction. In a similar fashion, the co-planar line identified on the inlet view can be used on the outlet image to affect uniplanar changes in the anteroposterior direction. This technique effectively minimizes disorientation when placing percutaneous SI screws. This can be particularly beneficial when placing screws in the prone position.
Conclusion
We have shown 2 techniques that are routinely used at our institution to help identify an accurate starting position for percutaneous screw placement in posterior pelvic ring injuries. Even experienced traumatologists can more quickly and accurately identify the correct stab incisions leading to more confidently placed screws. Further, we believe understanding the usage of fluoroscopy and the concepts involved in drawing the lines enhance trainees’ comprehension of the complex anatomy of the sacrum.
1. Matta JM, Saucedo T. Internal fixation of pelvic ring fractures. Clin Orthop Relat Res. 1989;242:83-97.
2. Routt ML Jr, Kregor PJ, Simonian PT, Mayo KA. Early results of percutaneous iliosacral screws placed with the patient in the supine position. J Orthop Trauma. 1995;9(3):207-214.
3. Sagi HC, Lindvall EM. Inadvertent intraforaminal iliosacral screw placement despite apparent appropriate positioning on intraoperative fluoroscopy.
J Orthop Trauma. 2005;19(2):130-133.
4. Routt ML Jr, Simonian PT, Mills WJ. Iliosacral screw fixation: early complications of the percutaneous technique. J Orthop Trauma. 1997;11(8):584-589.
5. Routt ML Jr, Simonian PT, Agnew SG, Mann FA. Radiographic recognition of the sacral alar slope for optimal placement of iliosacral screws: a cadaveric and clinical study. J Orthop Trauma. 1996;10(3):171-177.
6. Gardner MJ, Ferrell ED, Nork SE, Segina DN, Routt ML Jr. Percutaneous placement of iliosacral screws without electrodiagnostic monitoring. J Trauma. 2009;66(5):1411-1415.
7. Miller AN, Routt ML Jr. Variations in sacral morphology and implications for iliosacral screw fixation. J Am Acad Orthop Surg. 2012;20(1):8-16.
8. Graves ML, Routt ML. Iliosacral screw placement: are uniplanar changes realistic based on standard fluoroscopic imaging? J Orthop Trauma. 2011;71(1):204-208.
1. Matta JM, Saucedo T. Internal fixation of pelvic ring fractures. Clin Orthop Relat Res. 1989;242:83-97.
2. Routt ML Jr, Kregor PJ, Simonian PT, Mayo KA. Early results of percutaneous iliosacral screws placed with the patient in the supine position. J Orthop Trauma. 1995;9(3):207-214.
3. Sagi HC, Lindvall EM. Inadvertent intraforaminal iliosacral screw placement despite apparent appropriate positioning on intraoperative fluoroscopy.
J Orthop Trauma. 2005;19(2):130-133.
4. Routt ML Jr, Simonian PT, Mills WJ. Iliosacral screw fixation: early complications of the percutaneous technique. J Orthop Trauma. 1997;11(8):584-589.
5. Routt ML Jr, Simonian PT, Agnew SG, Mann FA. Radiographic recognition of the sacral alar slope for optimal placement of iliosacral screws: a cadaveric and clinical study. J Orthop Trauma. 1996;10(3):171-177.
6. Gardner MJ, Ferrell ED, Nork SE, Segina DN, Routt ML Jr. Percutaneous placement of iliosacral screws without electrodiagnostic monitoring. J Trauma. 2009;66(5):1411-1415.
7. Miller AN, Routt ML Jr. Variations in sacral morphology and implications for iliosacral screw fixation. J Am Acad Orthop Surg. 2012;20(1):8-16.
8. Graves ML, Routt ML. Iliosacral screw placement: are uniplanar changes realistic based on standard fluoroscopic imaging? J Orthop Trauma. 2011;71(1):204-208.
