Session VII - Pelvis

Fri., 10/6/06 Pelvis, Paper #36, 3:12 pm

S2 Iliosacral Screw Fixation for Unstable Posterior Pelvic Ring Injuries in Patients with Upper Sacral Segment Dysmorphism

Joe M. Conflitti, MD1 (n); Matt L Graves, MD2 (n);
M. L. (Chip) Routt, MD2 (n);
1East Texas Medical Center, Tyler, Texas, USA (*);
2Harborview Medical Center, Seattle, Washington, USA

Purpose: Approximately 30% of the population have upper sacral segment dysmorphism that affects iliosacral screw placement. In these cases, placement of iliosacral screws into the upper sacral segment is typically limited by a smaller zone of safety. Directing screws into the second sacral segment is often advantageous. The purpose of this study was to evaluate the safety of treating patients with upper sacral segment dysmorphism and unstable posterior pelvic ring injuries with iliosacral screws directed into the second sacral segment.

Methods: 156 patients with unstable posterior pelvic ring injuries were treated operatively over a 15-month period. Of these, 24 (15.4%) were treated with placement of S2 iliosacral screws. Inclusion criteria included patients with: (1) unstable posterior pelvic ring injuries, (2) signs of upper sacral segment dysmorphism, (3) a narrowed "safe zone" for insertion of S1 screws as noted on CT scan, and (4) adequate space for insertion of iliosacral screws into the S2 segment (defined as a""safe zone" width of at least 10 mm on two consecutive 3-mm CT slices). There were 17 males and 7 females with an average age of 41 years (range, 19-74). Pre- and postoperative radiographic imaging included inlet/outlet pelvic radiographs and a two-dimensional pelvic CT scan with 3-mm slices. The smallest width of the""safe zone" (the area bounded anteriorly by the alar cortex and posteriorly by the sacral neural foramen) was measured at the S1 and S2 level on the preoperative CT scan. Screw position was judged by the postoperative CT scan to be intraosseous, juxtaforaminal (threads abutting but not within the neurologic tunnel), or intraforaminal/extruded. Neurologic exams were completed postoperatively.

Results: There were no iatrogenic neurologic injuries related to the surgical procedure. 19 of 24 patients (79%) had screws graded as intraosseous, and the screws of the remaining five (21%) were juxtaforaminal. The S1 safe zone averaged 16.1 mm (range, 10.5-25.4), and the S2 safe zone averaged 19.6 mm (range, 10.6-30.3).

Conclusions/Significance: Using consistent intraoperative fluoroscopic imaging and a detailed preoperative plan, percutaneous iliosacral screw insertion within the second sacral segment can be predictably accomplished in patients with signs of upper sacral segment dysmorphism.

If noted, the author indicates something of value received. The codes are identified as a-research or institutional support; b-miscellaneous funding; c-royalties; d-stock options; e-consultant or employee; n-no conflicts disclosed, and *disclosure not available at time of printing.
· The FDA has not cleared this drug and/or medical device for the use described in this presentation (i.e., the drug or medical device is being discussed for an "off label" use). · · FDA information not available at time of printing.