CTNav technique increases accuracy of pedicle screw placement compared with fluoroscopy technique: study

Percutaneous pedicle screw (PPS) placement is a key step in several minimally invasive spinal surgery (MISS) procedures. Traditional technique for PPS makes use of C-arm fluoroscopy assistance (FA). More recently, newer intraoperative imaging techniques have been developed for PPS, including CT-guided navigation (CTNav).

Rocca et al conducted a study to compare FA and CTNav techniques for PPS with regard to accuracy, complications, and radiation dosage.

A total of 192 patients with degenerative lumbar spondylolisthesis and canal stenosis who underwent MISS posterior fusion±interbody fusion through transforaminal approach (TLIF) were retrospectively reviewed.

In the FA group, a standard C-arm fluoroscopy was used for pedicle screw placement.

In the CTNav group, an AIRO mobile intraoperative CT scanner was used for pedicle screw placement. A small midline lumbar incision at the level of the intercristal line was performed, and a spinous process clamp was placed. The spinous process clamp was used as a reference guide for CT scanning. Following 3D reconstruction of the surgical area, a navigated drill guide was used to drill the holes for PPS placement. After PPS placement, an intraoperative CT scan was performed again to check for the accuracy of screws placement. After screw placement, a midline incision for laminoartrectomy and dural sac/roots decompression was performed in both groups.

Intraoperative effective dose (ED, mSv) was measured. Screw placement accuracy was assessed postoperatively on a CT scan using Gertzbein and Robbins classification (grades A–E). Oswestry disability index (ODI) and visual analog scale (VAS) scores were compared in both groups before and after surgery.

Key findings of the study were:

• A total of 101 and 91 procedures were performed with FA (FA group) and CTNav approach (CTNav group), respectively.

• Median age was 61 years in both groups, and the most commonly treated level was L4–L5.

• Median ED received from patients was 1.504 mSv (0.494–4.406) in FA technique and 21.130 mSv (10.840–30.390) in CTNav approach (p< 0.001).

• Percentage of grade A and B screws was significantly higher for the CTNav group (96.4% versus 92%, p <0.001), whereas there were 16 grade E screws in the FA group and 0 grade E screws in the CTNav group (p< 0.001).

• A total of seven and five complications were reported in the FA and CTNav group, respectively (p=0.771).

The authors commented – "In conclusion, CTNav technique is a safe adjunct to spinal surgery. It reduces surgeon and staff radiation exposure (although it does increase radiation dose for patients) and increases the accuracy of screw placement without affecting operation time. Nevertheless, no significant difference was noted in terms of reoperation rate due to screw malpositioning between CTNav and FA techniques."

Level of Evidence: Level 3

Further reading:

Intraoperative CT-guided navigation versus fluoroscopy for percutaneous pedicle screw placement in 192 patients: a comparative analysis Giuseppe La Rocca, Edoardo Mazzucchi et al Journal of Orthopaedics and Traumatology (2022) 23:44 https://doi.org/10.1186/s10195-022-00661-8