Percutaneous iliac screws for minimally invasive spinal deformity surgery

Abstract

Introduction. Adult spinal deformity (ASD) surgeries carry significant morbidity, and this has led many surgeons to apply minimally invasive surgery (MIS) techniques to reduce the blood loss, infections, and other peri-operative complications. A spectrum of techniques for MIS correction of ASD has thus evolved, most recently the application of percutaneous iliac screws. Methods. Over an 18 months 10 patients with thoracolumbar scoliosis underwent MIS surgery. The mean age was 73 years (70% females). Patients were treated with multi-level facet osteotomies and interbody fusion using expandable cages followed by percutaneous screw fixation. Percutaneous iliac screws were placed bilaterally using the obturator outlet view to target the ischial body. Results. All patients were successfully instrumented without conversion to an open technique. Mean operative time was 302 minutes and the mean blood loss was 480 cc, with no intraoperative complications. A total of 20 screws were placed successfully as judged by CT scanning to confirm no bony violations. Complications included: two asymptomatic medial breaches at T10 and L5, and one patient requiring delayed epidural hematoma evacuation. Conclusions. Percutaneous iliac screws can be placed safely in patients with ASD. This MIS technique allows for successful caudal anchoring to stress-shield the sacrum and L5-S1 fusion site in long-segment constructs.

Figure 1

Obturator outlet view showing the “teardrop” target for iliac screw placement. Cannulation of this space provides a safe corridor completely within the bony confines.

Figure 2

Cannulated 8 mm diameter by 80 mm long screws for iliac fixation and cannulated cancellous bone probe.

Figure 3

Recession of the iliac screw saddles into the bone to avoid hardware prominence as seen on this postoperative (a) axial and (b) sagittal reconstruction CT scan.

Figure 4

Case example showing a T9 to Iliac MIS fusion with interbody grafts at L2-S1. (a) and (b) Pre- and postoperative AP, and (c) and (d) Pre- and postoperative lateral 36” X-Ray images. (e) Intraoperative view.

Figure 5

Two plane rods bending in the (a) sagittal and (b) coronal planes to facilitate connection to the more laterally located iliac screw saddles.