3D Navigation May Improve Accuracy of SI Screw Placement

Patients with sacral dysmorphism may see even greater benefit

Peter Pollack

Data presented in poster presentation P476 suggest that three-dimensional (3D) navigation may increase the accuracy of percutaneous sacroiliac (SI) screw placement, as compared with conventional fluoroscopic technique or two-dimensional (2D) navigation.

The authors conducted a retrospective review of data collected in a multicenter, prospective, randomized controlled study. They identified 130 patients in the database whose records contained all the information needed for analysis. The patients were categorized into two groups based on the presence or absence of associated sacral dysmorphism.

“Sacral dysmorphism was evaluated on computed tomography (CT) scans,” write the authors. “It was defined as an acutely sloped sacral ala precluding the safe use of the iliac cortical densities as a radiographic landmark.”

The authors evaluated screw placement using an independent pelvic surgeon and five of the operative pelvic surgeons, all of whom were blinded to surgical technique and patient demographics. Evaluations took place at least 1 year after initial surgery. For a case to be included in the final analysis, at least two of the six evaluators had to agree that a screw was misplaced.

No misplaced screws in 3D subsets
The authors found that 11.9 percent of patients in the non-dysmorphic group had misplaced screws. However, none of the patients in the 3D-navigation segment of this group had misplaced screws.

Among the 16.1 percent of patients who fell into the dysmorphic group, 28.6 percent of patients had misplaced screws. Similarly, none of the patients in this group who were treated using 3D navigation had misplaced screws.

Overall, there was 32 percent raw agreement between the six evaluators regarding the misplaced screws. Overall agreement was 69 percent.

Based on these data, the authors recommend the use of 3D navigation, where available, for SI screw insertion. They point out that this may be especially important in patients with dysmorphic proximal sacral segments.

The study was conducted by Amir Matityahu, MD; David M. Kahler, MD; Christian Krettek, MD; Ulrich Stöckle, MD; Peter Messmer, MD; Jan Ljungqvist; and Florian T. Gebhard, MD.

Scientific Poster P476, “Sacroiliac Screw Placement in Dysmorphic Sacrum is More Accurate with 3D Navigation than 2D or Fluoroscopy” is on view in Academy Hall B through Friday.

Disclosures: Dr. Matityahu—DePuy Synthes, Anthem Orthopaedics, PDP Holdings, Stryker; Dr. Kahler—Johnson & Johnson, Journal of Orthopaedics and Traumatology; Dr. Krettek—Synthes, Stryker, Saunders/Mosby-Elsevier, Springer; Dr. Stöckle—Aesculap/B.Braun, Synthes, Zeitschrift für Orthopädie und Unfallchirurgie; Drs. Messmer and Gebhard, Mr. Ljungqvist—no conflicts.

2013 Annual Meeting News
Tuesday through Friday, February 19 – 23, 2013.
http://www.aaos.org/news/acadnews/2013/AAOS11_3_20.asp