gms | German Medical Science

64th Annual Meeting of the German Society of Neurosurgery (DGNC)

German Society of Neurosurgery (DGNC)

26 - 29 May 2013, Düsseldorf

Analysis of pedicle screw misplacement in robotic-guided percutaneous instrumentation surgery of the thoracic and lumbar spine

Meeting Abstract

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  • Ramon Martinez - Klinik für Neurochirurgie, Universitätsmedizin Göttingen
  • Anina Hahn - Klinik für Neurochirurgie, Universitätsmedizin Göttingen
  • Veit Rohde - Klinik für Neurochirurgie, Universitätsmedizin Göttingen

Deutsche Gesellschaft für Neurochirurgie. 64. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC). Düsseldorf, 26.-29.05.2013. Düsseldorf: German Medical Science GMS Publishing House; 2013. DocMO.02.06

doi: 10.3205/13dgnc015, urn:nbn:de:0183-13dgnc0157

Published: May 21, 2013

© 2013 Martinez et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Objective: Pedicle screw fixation is the standard of care for stabilization of the thoracic and lumbar spine in a variety of pathologies. Robotic-guided screw placement has been shown to be a valuable tool reaching high accuracy rates. Percutaneous techniques represent a challenge to appropriate screw placement. The reported rate of screw misplacement using open techniques is well described, however data is lacking on the exact failure rate of the percutaneous robotic-guided technique.

Method: 217 consecutive patients underwent from 2008 to 2012 percutaneous, robotic-guided pedicle screw fixation for degenerative-, tumoral or infectious pathologies in the thoracic and lumbar spine. A spinous process mounted robotic device (SpineAssist™, Mazor Robotics, Israel) was used. CT scans were performed pre- and postoperatively. Evaluation of screw position was done using a four-grade score: grade 0 (screw entirely within cortex of pedicle), grade 1 (encroachment of the pedicle cortex), grade 2 (deviation of less than 3 mm outside the pedicle cortex), grade 3 (deviation from 3 to 6 mm) and grade 4 (deviation of more than 6 mm). Spine torsional deformity angle was assessed by Ho’s method. Statistical analysis was performed with the student t-test or Wilcoxon test. Significance was assumed by p<0.05.

Results: There were 44 thoracic procedures (20.3%), whereas in 31 cases (70%) instrumentation included 3 or more levels. Lumbar surgery was done in 173 patients (79.7%), with instrumentation of 3 or more levels in 100 patients (57.8%). Misplacements of screws were observed in 17/217 cases (7%). Of these, the majority were grade 2 violations (15 patients, 88.2%). Spinal deformities were observed in 14/17 patients (82.3%), mainly degenerative torsion scoliosis (8/14 patients, 57.1%). In these cases the torsional deformity angle was 7.9±5.3 degrees (mean ± SD). Spondylolisthesis Meyerding grade II was observed in 6/14 cases, (42.8%). By means of quantitative CT osteodensitometry, osteoporosis was detected in 9/17 patients (52.9%). 5/17 patients (29.4%) were diagnosed of adipositas (BMI >30 kg/m2). Only the presence of torsion scoliosis was significantly associated with pedicle screw misplacement.

Conclusions: The use of robotic-guidance in percutaneous screw implantation is an accurate technique in experienced hands. The misplacement rate is below the rates reported in the literature for open procedures. Nevertheless, failure in position of screws is a concern in patients showing relevant spinal deformities.