Examining Screw Fixation Techniques in ASD Surgery

A study by orthopedic surgeons at NYU Langone Health has demonstrated that in adult spinal deformity (ASD) correction both robotic and computed tomography (CT)–navigated pedicle screw placement offer potentially better outcomes than freehand techniques.

Although several studies have established the efficacy of robotically assisted and navigated screw placement for improved accuracy and outcomes, there remains a lack of consensus whether such approaches are beneficial in all cases.

Themistocles Protopsaltis, MD, chief of the Division of Spine Surgery, and his team began to question the reliance on freehand screw fixation for spine deformity correction, considering the potential for better outcomes with robotic and CT-navigated approaches.

“The arrival of robotic and navigational technology marks a paradigm shift in the surgical treatment of ASD,” Dr. Protopsaltis says. “In this study, we found that both techniques improved accuracy compared to freehand screw placement.”

Comparing Approaches

The retrospective study, presented at the AAOS 2025 Annual Meeting, compared 237 patients who underwent deformity correction surgery with five or more levels of fusion. Among these patients, 158 had freehand, 50 CT-navigated, and 29 robotic-guided screw fixation, with a total of 2,372 screws placed.

“We limited our study to patients with available postoperative CT scans,” explains Dr. Protopsaltis, “and analyzed outcomes up to two years.”

With respect to patient characteristics, those in the navigation group were older than those in the freehand group, and the robotic and navigation groups included more patients being seen for revision surgery compared to freehand, whereas robotic-guided patients had a higher body mass index than freehand patients.

Furthermore, navigation patients had a higher Charles Comorbidity Index score compared to robotic-guided and freehand patients.

Better Outcomes

Importantly, robotically assisted and navigation patients had superior screw accuracy, with significantly lower rates of screw malposition compared to freehand—5.5 percent vs. 6.6 percent vs. 13.8 percent, respectively.

Moreover, both robotic and navigation groups exhibited lower rates of screw-related symptoms and revisions.

In terms of surgical outcomes, patients in the freehand group had significantly more blood loss than robotic-guided patients, including a higher incidence of mass blood loss—defined as greater than 2 liters.

The researchers also found that navigation patients had significantly longer operative times than robotic-guided and freehand patients—572.54 minutes vs. 490.34 minutes vs. 446.37 minutes, respectively.

Following the procedure, while there was no difference in length of stay or overall postoperative complications, regression analysis revealed that in comparison to freehand, navigation patients had a higher rate of cardiac complications (20.0 percent vs. 4.4 percent), and robotic-guided patients had a higher rate of urinary complications (13.8 percent vs. 3.2 percent).

“The significance of safe and accurate pedicle screw insertion in ASD correction is paramount,” says Dr. Protopsaltis. “Our findings provide early evidence that robotic and navigation systems can be safely implemented to enhance radiographic screw outcomes in patients with deformity.”

Clinical Implications

In light of these findings, Dr. Protopsaltis and his team believe that for experienced surgeons, implementing robotic-guided and CT-navigated systems may improve the safety and quality of ASD surgery.

“Next-generation spinal robotics and navigation systems could play a significant role in successfully minimizing surgical trauma,” says Dr. Protopsaltis. “However, more work is needed before robotic and navigation approaches can be fully integrated into the surgical treatment of spinal deformity.”

At present, he recommends a hybrid approach of screw fixation, where surgeons can employ robotic navigation to accommodate more difficult screw maneuvers, but still utilize nonrobotic methods when placing more commonplace screws.

“In clinical practice, we don’t use the robot to place every screw, as there are nuances with each case,” he explains. “We are fortunate to have robotic technology, but if circumstances require, we can employ an alternative method.”