title: Inertial Measurement Unit-Assisted Implantation of Thoracic, Lumbar, and Sacral Pedicle Screws Improves Precision of a Freehand Technique.
abstract: OBJECTIVE
  A method applying inertial measurement units (IMUs) was developed to implant pedicle screws in the thoracic and lumbosacral spine. This was compared with a freehand technique.
  
  
  METHODS
  The study was done on 9 human cadavers. For each cadaver, a preoperative computed tomography (CT) scan was performed to measure the axial and sagittal tilt angles of the screw trajectories from T1 to S1. After the entry points were defined on the exposed spine, the IMU-equipped pedicle finder and screwdriver were used to reproduce these tilt angles and implant half of the screws. The other half was implanted with a freehand technique. Fluoroscopy was not used. The screw trajectories were analyzed on postoperative CTs.
  
  
  RESULTS
  A hundred and sixty-two screws were placed with use of the IMUs and 162 screws were implanted by freehand. The IMU-guided technique matched the planned trajectories significantly better than the freehand technique (axial tilt P < 0.001, sagittal tilt P < 0.001). With IMU assistance, the mean offsets between the planned and postoperatively measured tilt angles of the screws were 3.3 degrees ± 3.5 degrees for the axial plane (median 2 degrees, range 0-23 degrees) and 3.4 degrees ± 3 degrees for the sagittal plane (median 3 degrees, range 0-13 degrees). For the freehand technique, the mean offsets between the planned and postoperatively measured tilt angles of the screws were 5.6 degrees ± 4.5 degrees for the axial plane (median 5 degrees, range 0-31 degrees) and 6.7 degrees ± 5.4 degrees for the sagittal plane (median 6 degrees, range 0-33 degrees).
  
  
  CONCLUSIONS
  IMU-assisted implantation of pedicle screws may enhance the performance of a freehand technique in the thoracic and lumbosacral spine.
authors.affiliation: Department of Spine Surgery, University Hospital Basel, Basel, Switzerland. Electronic address: gregory.jost@icloud.com.
authors.forename: Gregory F
authors.initials: GF
authors.lastname: Jost
authors.affiliation: Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland.
authors.forename: Jonas
authors.initials: J
authors.lastname: Walti
authors.affiliation: Department of Neurosurgery, University Hospital Basel, Basel, Switzerland.
authors.forename: Luigi
authors.initials: L
authors.lastname: Mariani
authors.affiliation: Department of Spine Surgery, University Hospital Basel, Basel, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schaeren
authors.affiliation: Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Cattin
mesh_terms: D000054:Acceleration; D061725:Accelerometry / Q000295:instrumentation; D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D060306:Magnetometry / Q000295:instrumentation; D008297:Male; D008875:Middle Aged; D065289:Pedicle Screws; D012399:Rotation; D012447:Sacrum / Q000000981:diagnostic imaging / Q000601:surgery*; D013523:Surgical Equipment; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed
keywords: Image-guided surgery; Inertial measurement unit; Navigation; Pedicle screws; Spine