Get to Know RJB

Preoperative templating of the trajectory of the pedicle or cortical trajectory screws with the CT scan or MRI scan is recommended. Angle of the optimal trajectory relative to the anteroposterior line for each instrumented level will ensure maximal accuracy during screw placement. Starting point of the pedicle screw with traditional trajectory or cortical screw trajectory (CBT) can be determined preoperatively in the axial plane. It is suggested that for reproducibility that the edge of the lateral superior facet be used. The same principle of a radiographically consistent starting point in the axial plane should be done for cortical bone trajectory. By using a consistently reproducible landmark on MR/CT scan — preoperative templating can be done by other personnel rather than the surgeon laboriously templating each pedicle. The axial angle can be directed through the widest part of the pedicle.

The sagittal orientation of the screw can be obtained via lateral fluoroscopy or intraoperative radiographs during surgery and is not typically preoperatively templated due to variations of the sagittal balance that happen during positioning of the patient on the operative table.

With the patient positioned on the operating table, rotate the table with the fluoroscopy machine in the true vertical position so that the fluoro beam is perpendicular to the floor. The AP or PA view of the spine should have the spinous process bisecting the pedicles.

This is critical to accurately use the RJB. The RJB orients to gravity, not the patient. The patient must be oriented to gravity by ensuring the anteroposterior line through the patient spine is in line with gravity.

Use starting point of screw as per common technique. Fluoroscopic confirmation of sagittal angle is recommended. Once the starting point is opened using burr or awl, the trajectory of the instrument on the sagittal is recorded, and the axial trajectory from the preoperative templating is combined with the sagittal trajectory to advance the initial pedicle probe.

Technique tip: RJB is internally oriented to gravity only. It is critical that the flat portion of the RJB module remain parallel to the craniocaudal axis of the patient to maintain consistent measurements. If there is coronal scoliosis/angulation, the flat portion of the RJB module should be facing the opposite pedicle. It is recommended that the probe be advanced, stopped, orientation checked then sagittal and axial angles obtained, then the process repeated until the depth desired is reached.

Technique Tip: Locate and burr a starting hole on both sides while using the fluoroscopy. This will enable the surgeon to immediately place both screws at that level, rather than place one screw and bring in the fluoroscopy machine for the starting point of the other side.

Straight or curved Lenke probes are usable. Confirm the trajectory of the pedicle screw insertion screwdriver matches that of the Lenke probe's trajectory as the screw is being advanced.

The contralateral side can immediately be done with maintaining the same sagittal and axial angle.

Determine the new sagittal angle at each new level to be instrumented.

Dispose of the RJB. The RJB is single use disposable only with a battery life rated as a maximum of 10 hours. It cannot be resterilized.