Rhee_Ch030.indd

314

Operative Techniques in Spine Surgery

T E C H N I Q U E S

■ The needle position is adjusted to be coaxial with the teardrop and then advanced 10 mm past the SI joint. ■ Next, a 1.45-mm guidewire is passed through the Jamshidi needle, again angling toward the AIIS. ■ The Jamshidi needle is removed, and the guidewire is advanced into the ilium through the cancellous bone between the cortices of the ilium until the adequate length is reached ( TECH FIG 7B ). ■ Positioning and angulation of the wire can be confirmed with fluoroscopic views as needed. ■ Screw lengths are then measured by marking the depth of the guidewire. Screw sizes of 8 to 10 mm by 80 to 100 mm are common in adults.

■ The hole is manually tapped over the guidewire using a can- nulated tap ( TECH FIG 7C ), and an appropriate length screw is placed ( TECH FIG 7D ). ■ Because the screws are in line with the rest of the spinal con- struct, no additional cross-connectors are required for assembly. ■ In cases in which a percutaneous lumbar spinal procedure has also been performed, the S2AI screw can be attached to the main spinal construct by threading a rod under the skin and muscles from proximal to distal and maneuvering the rod with a premade rod-guidance tube. ■ The final trajectory and placement of the screw is identical to that of the open S2AI technique.

A

B

C

D TECH FIG 7 ● A. Representative fluoroscopic teardrop view is obtained by rolling the C-arm roughly 30 degrees over the table and tilting it roughly 30 degrees cephalad, which creates an overlap of the AIIS and PSIS and the image of a teardrop. B. Percutaneous guidewire placement. C. A cannulated handheld tap is used to tap the screw hole over the guidewire. D. The screw is placed with a handheld drill (green handle). In cases in which a minimally invasive lumbar spine procedure has also been done, the rod can be attached to the main spinal construct by passing it underneath the skin with the assistance of premade rod guidance tubes. ( A,D: From Martin CT, Witham T, Kebaish KM. Sacropelvic fixation: two case reports of a new percutaneous technique. Spine 2011;36[9]:e618–e621.)