Robotic-Guided S2AI Screw Placement Offers Accurate and Efficient Sacropelvic Fixation

Isador H. Lieberman, MD, and Dennis Devito, MD, comment

Peer Reviewed

Robotic-guided S2-alar iliac (S2AI) screw placement was found to be accurate and efficient in sacropelvic fixation in a recent retrospective review published in the March issue of the European Spine Journal.

The benefits of robotic-assisted sacropelvic fixation using S2AI screw placement include “precision and efficiency,” said lead author Isador H. Lieberman, MD, Director of the Scoliosis & Spine Tumor Center, Texas Back Institute, Texas Health Presbyterian Hospital Plano, Texas. He added that the procedure is safe and effective relative to standard screw placement.

“A robot does not make a bad surgeon good, it makes a good surgeon more efficient and precise,” Dr. Lieberman told SpineUniverse.

surgeon pointing to medical treatment options“A robot does not make a bad surgeon good, it makes a good surgeon more efficient and precise”. Photo Source: LifetimeStock.

Study Rationale and Design

The S2AI screw is placed across the sacroiliac joint into the ilium, and can be placed via traditional midline incision to minimize collateral damage. Because accurate placement of S2AI screws can be challenging even with biplane fluoroscopic guidance, Dr. Lieberman and colleagues investigated the feasibility and accuracy of using robotic guidance.

The study analyzed 35 S2AI screws placed in 18 patients (mean age, 60 years) using the Renaissance robotic guidance system. The researchers describe the steps involved in the procedure in their paper.

Preoperative and postoperative CT scans used to determine screw placement and possible deviation from the preoperative plan. The planned versus actual screw placement was compared using the software’s measurement tool in axial and lateral views, at entry point to the S2 pedicle and at a 30 mm depth at the screws’ mid-shaft, in a resolution of 0.1 mm.

Robotic Guidance Considered Successful in All Screw Placements

Robotic guidance was considered successful in all 35 screws, with postoperative CT scans showing that all trajectories were accurate. No intra-operative complications occurred, and no violations of the iliac cortex or breaches of the anterior sacrum were noted.  

Screw placement deviated from the preoperative plan by 3.0 ± 2.2 mm in the axial plane and 1.8 ± 1.6 mm in the lateral plane. At 30-mm depth, the deviations were 2.1 ± 1.3 mm and 1.2 ± 1.1 mm, respectively.

“I have had a similar experience using robotic guidance for difficult trajectories like the S2AI screw,” commented Dennis Devito, MD, who is a pediatric orthopaedist at Children’s Orthopaedics of Atlanta. “The need for C-arm is greatly reduced,” said Dr. Devito, who added that he agreed with the findings by Dr. Lieberman and colleagues.

Updated on: 05/04/19
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Isador H. Lieberman, MD, MBA, FRCSC
Orthopaedic and Spinal Surgeon
Texas Back Institute
Plano, TX

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