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Mini Screws for Improving Accuracy in Navigation-assisted Spine Surgery

Ahmadi, Sebastian A. MD*; Hashemi, Amin MD; Harms, Jürgen MD, PhD; Orakcioglu, Berk MD

doi: 10.1097/BSD.0000000000000685
Surgical Technique

Study Design: Presentation of a surgical technique with accompanying video (Supplemental Digital Content 1, of an illustrative case.

Objective: The objective of this study was to present a helpful and easy-to-implement technique for improving initial referencing accuracy, as well as rereferencing accuracy in cases of multilevel instrumentation or in cases of dislocation of the reference array.

Summary of Background Data: Navigation-assisted spine surgery has become standard of care in most hospitals performing complex spine interventions. Although short-segment instrumentations are fairly straight-forward with current hardware and software solutions, obtaining ideal accuracies and troubleshooting reference array disruptions remain challenging.

Methods: A surgical technique is presented as a step-by-step guide using intraoperative videos and photographs as well as imaging data in an illustrative case of thoracic hemivertebra resection and dorsal instrumentation.

Technique/Results: After skin incision is performed at the index level, posterior soft tissue preparation is performed. Before firmly attaching the reference array to a spinous process we then insert a minimum of four 5 mm mini screws at any bony structure within the exposure. Then an intraoperative navigation scan (3-dimensional computed tomography or x-ray) is obtained, and initial referencing is performed using the previously inserted mini screws as landmarks. This yields mean accuracies of 1 mm or lower and is easily verifiable by placing the navigation probe on a mini screw head. This action can be swiftly repeated at any time to prevent reduced accuracy because of insertion forces applied during pedicle screw placement. In addition, this allows for easy rereferencing in cases of disruption or complete removal of the navigation array, eliminating the need to perform additional computed tomography or x-ray scans during the procedure.

Conclusions: The technique presented allows for rapid and highly accurate initial referencing and can be used in all cases of navigation-assisted spine surgery. It also allows for hassle-free rereferencing in cases of disruption or accidental removal of the reference array.

*Department of Neurosurgery, University Hospital Düsseldorf, Düsseldorf

Spine Surgery, Ethianum, Heidelberg, Germany

Presented at the Section for Microsurgery and Neuroanatomy of the German Society of Neurosurgery (DGNC) in Luxembourg, April 2017 and Section for Spine Surgery of the DGNC in Munich, September 2017.

The authors declare no conflict of interest.

Reprints: Berk Orakcioglu, MD, Spine Surgery, Ethianum, Voßstraße 6, 69115 Heidelberg, Germany (e-mail:

Received January 26, 2018

Accepted May 17, 2018

© 2019 by Lippincott Williams & Wilkins, Inc.