The Spinal Navigation Trial - Surgical Navigation or Free Hand Technique in Spine Surgery (SPINAV)

The spinal navigation trial (SPINAV) is a randomized controlled trial (RCT) evaluating the use of computer-assisted navigation in surgery for spinal deformity

Spinal deformity is a common reason for spinal surgery at youth. In addition, the incidence of surgery for spinal deformity in older adults is increasing. Spinal deformity surgery is by far the most complex spine surgery. One complexity lies in the correct placement of implants in the severely deformed spine. Today, the most common surgical procedures for spinal deformity involve placement of screws in the vertebral pedicle in the instrumented part of the spine. This gives good bone purchase, which is important for deformity correction. The pedicle is narrow and misplaced pedicle screws can result in vascular, pulmonary or neural injuries, or inadequate bone purchase. Compared to the conventional free-hand surgical technique, which relies on the knowledge of anatomy, computer-assisted navigation using intraoperative 3D imaging has been shown to improve screw placement accuracy and reduce complications due to screw misplacements. As a consequence, navigation may also reduce the frequency of postoperative revision surgery compared to free hand. However, navigation still takes time, and is associated with higher intraoperative radiation than the free hand technique. As of yet, the majority of data in this area are based on retrospectively collected series, and some prospectively collected series, while randomized controlled trials on spinal deformity are lacking. In this randomized controlled trial the accuracy of pedicle screw placement using augmented reality surgical navigation (ARSN), infra-red surgical navigation (IRSN) and conventional free-hand technique will be investigated. Patients of age 12 years and older with spinal deformities are randomized into one of the three surgical techniques mentioned above. The primary outcome variable is pedicle screw placement accuracy at 1st attempt assessed using the Gertzbein scale.

Augmented reality surgical navigation (ARSN). Pedicle screw placement using the Philips ClarifEye system combined with Philips Allura for imaging.

Infrared surgical navigation (IRSN). Pedicle screw placement using Brainlab Curve 1.2 combined with Medtronic o-arm for imaging.

Spinal deformity correction. Pedicle screws are inserted using free hand technique with the help of intraoperative fluoroscopy if needed.

Spinal deformity correction. Pedicle screws are inserted using augmented reality surgical navigation (ARSN) with the ClarifEye navigation system and the Philips Allura 2D/3D imaging system.

Spinal deformity correction. Pedicle screws are inserted using infra-red surgical navigation (IRSN) with the Brainlab Curve 1.2 navigation system combined with the Medtronic O-arm 2D/3D imaging system.

The primary endpoint is the percentage of accurately placed pedicle screws assessed using the Gertzbein scale and based on intraoperative verification scan cone beam computed tomography (CBCT).

Deviation from planned navigated path in mm at bone entry and screw tip measured on the postoperative computed tomography (CT)

Deviation from navigated path in mm at bone entry and screw tip measured on the postoperative computed tomography (CT)

Angular deviation (degrees) of the placed screw compared to the planned navigated path measured on the postoperative computed tomography (CT)

Angular deviation of the placed screw compared to the navigated path measured on the postoperative computed tomography (CT)

Accuracy at 1st attempt = (Screws placed at first attempt according to intraoperative protocols and graded 0 or 1) / (total number of placed screws). Assessed on intraoperative CBCT

Final accuracy of placed pedicle screws is calculated as: number of accurately placed screws (Gertzbein grade 0+1) according to postoperative CT / total number of placed screws.

The study aims for 100% pedicle screw density. Hooks may be placed as rescue or if screw placement fails.

Pedicle diameters are measured on preoperative and intraoperative CT. Pedicle screw placement measured on intraoperative and postoperative CT.

Patient radiation exposure (ED in mSv) for the whole procedure, Patient radiation exposure (ED in mSv) for fluoroscopy Patient radiation exposure (ED in mSv) for each CBCT

Total procedure time as well as normalized to number of spinal levels from the upper to the lower instrumented vertebra.

Intraoperative planning time (from start of planning in navigation software until last screw planned) (only when treated with ARSN or IRSN)

Instrumentation time (total time for navigated/FH screw placement from first to last screw placement)

Measured from day of surgery until day of discharge. Usual length of stay is less than one week, and maximum two weeks.

Inclusion Criteria: Written informed consent by patient or legal guardian Age 12 years and older Spinal deformity surgery Exclusion Criteria: Unable to give informed consent Surgery without pedicle screws Previous surgery with pedicle screws in the planned surgical area

Manuscripts will be submitted for publication in peer-reviewed journals. Quality-controlled raw data as well as processed data used in publications will be made available at the time of publication.

The detailed protocol, including the statistical analysis plan will be submitted for publication after study start. No end date.