Ahmed A. Aoude, Maryse Fortin, Rainer Figueiredo, Peter Jarzem, Jean Ouellet, Michael H. Weber

April 2015, Volume 24, Issue 5, pp 990 - 1004 Review Read Full Article 10.1007/s00586-015-3853-x

First Online: 07 March 2015

Study design

Systematic review.


The aims of this systematic review were: (1) to determine the most commonly used methods for assessing pedicle screw placement accuracy, and (2) assess the difference in pedicle screw placement accuracy between navigation and free-hand techniques according to the classification method.

Background data

Pedicle screw fixation and spine surgery have almost become synonymous. However, there is currently no gold standard method to assess pedicle screw placement accuracy. We reviewed the literature to determine current techniques used by spine surgeons for the assessment of pedicle screw accuracy.


We systematically reviewed the medical literature (OVID Medline, Embase, PubMed) to identify all articles published between 2010 and 2013 that have assessed pedicle screw placement accuracy in humans. Two independent reviewers with a third independent mediator performed study screening, selection and data extraction using a blinded and objective protocol.


A total of 68 relevant articles were included in this systematic review, for a total of 3442 patients, 60 cadavers and 43,305 pedicle screws. The most widely used method (37 articles) was based on 2 mm breach increments measured on computer tomography images. The second most widely used method consisted of an “in” or “out” classification system (16 articles). The remaining 15 articles used variable classification systems. Our result suggests that an average of 91.4 % of pedicle screws placed with free-hand or fluoroscopy technique where within the safe zone (<2 mm breach) in comparison to an average of 97.3 % of pedicle screws using navigation (p < 0.001) for the 2 mm increment method. Similarly, the in or out classification also showed statistically significant difference between free-hand and navigated techniques (p < 0.001).


The grading system based on 2 mm increments seems to be the most widely accepted method for determining pedicle screw placement accuracy. All grading systems were based on imaging alone without taking into account the direction of the breach or patient’s symptoms.

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