Radiographic anatomical analysis of the pelvic Teepee view / 中国骨伤

<p><b>OBJECTIVES</b>To research radiographic anatomy of the main structure of the pelvic Teepee view, including its azimuth direction and view anatomy structure.</p><p><b>METHODS</b>From June 2013 to June 2014 adult pelvic CT examination results were filtered, excluding skeletal deformities and pelvic osseous destruction caused by tumors, trauma, etc. The data of 2.0 mm contiguous CT scan of 9 adults' intact pelves was,selected and input into Mimics 10.01 involving 7 males and 2 females with an average age of (41.2±10.3) years old. Utilizing the software, the 3D CT reconstructions of the pelves were completed. Setting the transparency being high,the pelvic 3D reconstructions were manipulated from the pelvic anteroposterior view to the combined obturator oblique outlet view and fine-tuned till the regular Teepee-or teardrop-shaped appearance emerges. Cutting tools of the software were at the moment applied to separate the "Teepee" from the main pelvis for each reconstruction. Then the "Teepee" and the rest (main) part of the pelvis were displayed in different color to facilitate the analysis on the Teepee, iliac-oblique, and anteroposterior views.</p><p><b>RESULTS</b>The "Teepee" started from the posterolateral aspect of the anterior inferior iliac spine and finished at the cortex between the posterior superior iliac spine and the posterior inferior iliac spine in a direction of being from caudal-anterior-lateral to cranial-posterior-medial. The radiographic anatomical composition of the "Teepee" contained one tip, one base,and two aspects. With the inner and outer iliac tables being the inner and outer aspects of the "Teepee", the tip is consequently formed by their intersection. The base is imaged from the cortex of the greater sciatic notch. The medial-inferior-posterior portion of the "Teepee" contains a small part of sacroiliac joint and its corresponding side of bone of the sacrum.</p><p><b>CONCLUSIONS</b>The "Teepee" is a zone of ample osseous structures of the pelvis, aside from a small medial-inferior-posterior portion, the main zone of which can be accepted as a safe osseous zone for the anchor of implants stabilizing certain pelvic and acetabular fracture patterns. The Teepee view can be utilized as guidance for the safe percutaneous insertion of such implants.</p>

Radiographic analysis of the osseous fixation zone for the iliac crest external fixation with Schanz screws / 中国骨伤

<p><b>OBJECTIVE</b>To radiographically analyze the osseous fixation zone for the iliac crest external fixation with Schanz screws and in order to guide their placement.</p><p><b>METHODS</b>Nine adults with 2.0-mm-slice continuous pelvic axial CT scans were selected as research subjects. Each CT scan data was imported into MIMICS 10.0. The osseous fixation zone the upper portion of the anterior column of the acetabulum which is located between the anterior superior iliac spine and the gluteal medius pillar and between the iliac crest and the acetabulum-for the iliac crest external fixation with Schanz screws was reconstructed into true sagittal and true coronal planes by using the software. Then the measurements were taken on the reconstructed planes with measuring tools. Finally, the measured data was analyzed.</p><p><b>RESULTS</b>The palpable iliac crest segment, which was of 49.6 mm width and located 16.5 mm posterior to the anterior superior iliac spine could be used to locate the start points of the Schanz screws. Under the above-mentioned iliac crest segment, the osseous zone was deep, got ample bony materials and could intraosseously contain Schanz screws with 5.0 mm diameter. The screws could be safely inserted to a minimal depth of 71.7 mm towards the acetabular dome and to a maximal depth of 143.5 mm posterior to the acetabulum.</p><p><b>CONCLUSION</b>The study can guide the effective insertion of the iliac crest Schanz screws. By setting a suitable start point in the above-mentioned iliac crest region and angling correctly relative to the acetabulum,the Schanz screw can be inserted into the relative strong cancellous bone above or posterior to the acetabulum with a considerable depth, to getting more bone engagement.</p>

S2 iliosacral screw insertion technique / 中国骨伤

<p><b>OBJECTIVE</b>To introduce a technique pertaining to S2 iliosacral screw insertion.</p><p><b>METHODS</b>The screw pathway was first measured on the preoperative pelvic CT scan or the standard sacral lateral radiograph to make sure the existence of the "safe zone" in the S2 segment for screw insertion. Under general anesthesia, patients were positioned supine or prone, depending on the injury pattern of pelvic ring or associated injuries requiring concomitant operation. The operation field was routinely sterilized using iodine and subsequent alcohol solution and draped. The tip of a guide wire was inserted through a stab wound to the posterior outer iliac table, manipulated in the "safe zone" being enclosed by the anterior aspect of the S2 nerve root tunnel, the anterior aspect of the sacral vertebrae, and the inferior aspect of the S1 foramen under the guidance of the standard sacral lateral fluoroscopy, and then the tip was hammered one to two millimeters into the iliac cortex. The guide wire progressed along the trajectory between the inferior aspect of the S1 foramen and the superior aspect of the S2 foramen on the pelvic outlet fluoroscopic view, and then along the posterior to the anterior aspect of the S2 sacral vertebrae and alae on the pelvic inlet fluoroscopic view with a predetermined length. At that moment, in order to ensure the safety, another standard sacral lateral view was imaged to detect the guide wire's tip which should locate posterior to the anterior aspect of the sacral vertebrae and anterior to the anterior aspect of the S2 nerve root tunnel. Subsequently, the depth was measured, the trajectory was drilled and tapped, and the screw was inserted. Following the removal of the guide wire, the wound was irrigated and sutured.</p><p><b>RESULTS</b>Utilizing this insertion technique, there were 30 S2 iliosacral screws in total being placed to stabilize the injured and unstable posterior pelvic ring in 27 patients. Each S2 screw was accompanied by an ipsilateral S1 screw. The S2 screw location was completely intraosseous in all patients, which was verified by postoperative pelvic outlet and inlet radiographs and CT scans. The insertion accuracy was 100 percent in the present series.</p><p><b>CONCLUSION</b>The S2 iliosacral screw insertion technique is safe and reproducible to guide the placement of the S2 screw, enhancing the stability for the compromised posterior pelvic ring.</p>

Classification of upper sacral segment based on continuous axial pelvic computed tomography scan / 中国骨伤

<p><b>OBJECTIVES</b>To introduce a classification system of upper sacral segment and its significance based on the continuous pelvic axial computed tomography scan.</p><p><b>METHODS</b>The whole pelvis 2.0 mm thick axial scan images of 127 cases were observed, the sacroiliac screw channel of S1 were measured, according to the size of the transverse screw channel the upper sacral segment were classified. Such as transverse screw channel existed and in at least 4 layer scan images its width was > 7.3 mm, it was defined as sacral segment of the normal type. Such as transverse screw channel existed and its maximum width was 7.3 mm or less on scanning level, it was defined as a transitional. Such as transverse channel did not exist, or its width on all scanning level was 0 mm or less, it was defined as dysplastic. Various cases,percentage, and the average of the transverse screw channel were calculated.</p><p><b>RESULTS</b>There were 58 normal (45.7%),42 transitional (33.1%), and 27 dysplastic (21.2%) upper sacral segments with an averaged width of the tansverse screw channel of 13.9 mm, 5.2 mm, and 0.9 mm, respectively. Each specimen could be defined as one of the three types of upper sacral segment without exceptions.</p><p><b>CONCLUSION</b>It is possible to insert a transverse iliosacral screw into a normal upper sacral segment when indicated because of the capacious transverse screw channel. The transverse iliosacral screw placement into the transitional and dysplastic upper sacral segments was contraindicated because of the limited or none transverse screw channel. The transitional upper sacral segment was superior to the dysplastic segment due to its starting point location restriction on the true lateral sacral view.</p>

Influence of the included angle between anterior aspects of S2 and S1 vertebral bodies on pelvic inlet imaging in mid-line sagittal plane / 中国骨伤

<p><b>OBJECTIVE</b>To analyze the influence of included angle between the anterior aspects of S2 and S vertebral bodies on pelvic inlet imaging in the pelvic midline sagittal plane.</p><p><b>METHODS</b>Totally 58 axial pelvic CT scans were chosen as study objects including 43 males and 15 females,with an average age of 40.7 years old (ranged,18 to 68 years old). The angles between the anterior aspects of S2 and S1, vertebral bodies and the horizontal plane on midline sagittal CT reconstruction were measured to simulate the optimal S2 and S1 inlet angles. The included angle between the anterior aspects of S2 and S1 vertebral bodies was calculated by subtrocting the S1,inlet angle from the S2 inlet angle defined as a base number. Then, the impact of the calculated included angles on the pelvic inlet imaging was analyzed. Results:The S2 inlet angles averaged (30.5±6.5) degrees; the S inlet angles averaged (25.7±5.9) degrees. The difference between them was significant (t=3.35, P=0.001). Ten patients had zero angle between the anterior aspects of S2 and S1 vertebral bodies; 14 patients had negative angle, averaged-(8.9±8.1) degrees; 34 patients had positive angle,averaged (11.8+6.4) degrees.</p><p><b>CONCLUSION</b>The difference of included angle between the anterior aspects of S2 and S1 vertebral bodies leads to the difference between S1 inlet view and S2 inlet view in most cases, complicating the pelvic inlet imaging,and affecting the reliability of the application of pelvic inlet view. Utilizing the angles measured on the preoperative midlihe sagittal CT reconstruction to obatin the patient-customized S1 and S2 inlet views could accurately guide the S1 and S2 iliosacral screw insertion.</p>

Effect of the anterior aspect of sacral nerve root tunnel on iliosacral screw placement on the standard lateral image of sacrum / 中国骨伤

<p><b>OBJECTIVE</b>To introduce the location and course of S1, S2 sacral nerve root tunnel and to clarify the significance of the anterior aspect of sacral nerve root tunnel on placement of iliosacral screw on the standard lateral sacral view.</p><p><b>METHODS</b>Firstly the data of 2.0 mm slice pelvic axial CT images were imported into Mimics 10.0, and the sacrum, innominate bones, and sacral nerve root tunnels were reconstructed into 3D views respectively, which were rotated to the standard lateral sacral views, pelvic outlet and inlet views. Then the location and course of the S1, S2 sacral nerve root tunnel on each view were observed.</p><p><b>RESULTS</b>The sacral nerve root tunnel started from the cranial end and anterior aspect of the vertebral canal of the same segment and ended up to the anterior sacral foramen with a direction from cranial-posterior-medial to caudal-anterior-lateral. The tunnel had a lower density than the iliac cortex and greater sciatic notch on the pelvic X-rays,especially on the standard sacral lateral view, on which it showed up as a disrupted are line and required more careful recognition.</p><p><b>CONCLUSION</b>It can prevent the iliosacral screw from penetrating the sacral nerve root tunnel and vertebral canal when recognizing the anterior aspect of sacral nerve root tunnel and choosing it as the caudal-posterior boundary of the "safe zone" on the standard lateral sacral view.</p>