An easily identifiable anatomic landmark for fluoroscopically guided sacroplasty: anatomic description and validation with treatment in 13 patients

Abstract

Background and purpose: Percutaneous sacroplasty has recently gained attention as a potential treatment for sacral insufficiency fractures. We describe a readily identifiable fluoroscopic landmark that facilitates needle placement and validate this with virtual needle placement by using CT data and fluoroscopically guided treatment in 13 patients.

Materials and methods: From CTs of 100 consecutive patients, the optimal target zone for needle placement in the sacral ala was defined at the intersection of lines from each of the corners of the first sacral segment, which is readily identifiable on lateral fluoroscopy. We then measured the distance from that virtual target point to the anterior sacral cortex by using the CT data for 3 specific trajectories: 1) parallel to the L5-S1 disk, 2) axial with respect to the patient, and 3) along the long axis of the sacrum. Case records of 13 consecutive patients treated by using this technique were also reviewed.

Results: The mean distances for the 3 trajectories were 11.3 mm, 11.2 mm, and 12.8 mm, respectively. Needle placement would have been outside the anterior sacral cortex in 3 patients. Review of preprocedure imaging easily identified this potential breach. During treatment, needle placement by using the landmark was successful in all patients, and there were no complications.

Conclusions: A safe target for sacroplasty needle placement in the superolateral sacral ala can be defined by using the intersection of lines drawn from the corners of the first sacral segment. We validated this landmark by using it for treatment in 13 patients. Further studies evaluating clinical outcomes following sacroplasty will be necessary.

Fig 1.

Demonstration of measurements made during virtual needle placement on a CT scan of the pelvis in a 65-year-old woman. A, On a sagittal midline reconstructed image, note the target (asterisk) by the intersection of line A (from the posterosuperior corner of S1 to the anteroinferior corner of S1) with line B (from the anterosuperior corner of S1 to the posteroinferior corner of S1). Three possible needle trajectories have been described and are indicated by the numbered white lines: 1) parallel to the L5-S1 disk space, 2) neutral or axial with respect to the patient, and 3) along the sacral long axis. B, Axial image taken along line 2 (axial plane) from the same patient demonstrates the target zones (asterisks) for each sacral ala. Line A represents the projection of line A from the sagittal image (A). Note how the 2 needle trajectories (black lines) are both parallel to their respective sacroiliac joints. C, Sagittal oblique image obtained along a line parallel to the sacroiliac joint shows the relative location of the target (asterisk) within the lateral sacrum. The distance from the target point to the anterior sacral cortex was obtained for the 3 needle trajectories described previously.

Fig 2.

Use of a fluoroscopic landmark in performing sacroplasty in a 76-year-old woman. A, Initial lateral image shows the needle in position at the intersection of lines as defined in Fig 1. B and C, Posttreatment frontal (B) and lateral (C) projections demonstrate polymethylmethacrylate cement in both sacral alas with no presacral extravasation.

Fig 3.

Example of a potential breach of the anterior sacral cortex in an 88-year-old woman with lumbarization of S1. A, Midline sagittal reformatted image from a CT scan shows the target zone (arrow) within S1 as described in Fig 1. B, Left parasagittal reformatted image shows that needle placement (arrow) would be anterior to the sacral cortex.