Introduction:

The use of image-guided navigation for pedicle screw placement has been on the rise in the past decade – with its proponents citing an increased accuracy of screw placement leading to a lower risk of clinical complications. The high upfront cost of image-guided navigation systems deter its widespread use in developing countries, particularly due to the absence of Level-1 studies demonstrating definite superiority of navigation-guided pedicle screw placement over free-hand pedicle screw placement. The objective of this prospective, randomized controlled study was to compare free-hand (FH) and O-arm navigation guided (ON) pedicle screw placement in the lumbar spine.

Methods:

Adult patients undergoing single-level lumbar interbody fusion by an open, posterior approach were prospectively recruited – patients with lumbar scoliosis, pedicle dysmorphia or high-grade spondylolisthesis were excluded. All patients were operated upon by a single chief surgeon with more than 5 years of experience in spine surgery. Patients were randomly assigned to either free-hand (FH) pedicle screw placement or O-arm navigation guided (ON) pedicle screw placement. The outcome measures compared between the two groups were: i) accuracy of pedicle screw placement – assessed using Gertzbein-Robbins classification of pedicle screw position and deviation from the ‘ideal’ coaxial intrapedicular trajectory (in degrees), ii) surgical time taken by the surgeon exclusively for pedicle screw placement (minutes), iii) radiation exposure (seconds fluoroscopy), iv) incidence of cranial facet violation (%) and, v) clinical complications attributable to malpositioned pedicle screws. 

Results:

A total of 80 patients (45 males, 35 females) comprised the study population – 40 patients were randomly allocated to each group (FH and ON); a total of 160 pedicle screws (4 per patient for single-level lumbar fusion) were inserted by each of the two techniques. The two groups were comparable with regards to baseline demographic and clinical variables as well as the indications for surgery. Although the accuracy of screw placement (ON: 97% v/s FH: 93%) and incidence of cranial facet violation (ON: 12% v/s FH: 22%) was better in the ON group, this difference was not statistically significant. However, placement of screws in the FH group deviated significantly more (FH: 11.8° v/s ON: 3.6°) from the ideal coaxial intrapedicular trajectory. Both the surgical time for screw placement (ON: 28 ± 14.4 minutes v/s FH: 15.6 ± 7.5 minutes) and radiation exposure (ON: 54.2 seconds v/s FH: 32.2 seconds) were significantly more in the ON group. Two patients in the FH group and one patient in the ON group had radicular pain in the postoperative period due to screw malpositioning and underwent revision surgery for the same.

Discussion:

In the hands of an experienced surgeon, O-arm navigation guided pedicle screw placement in the lumbar spine provides no added advantage over free-hand pedicle screw placement, despite increasing the surgical time for screw placement and the radiation exposure to the patient.