Trans-isthmic pars interarticularis screw fixation under CT and fluoroscopic guidance. Technical success and clinical outcome in patients with symptomatic low-grade lumbar isthmic lysis

To assess the technical success of trans-isthmic screw fixation with simultaneous CT and fluoroscopic guidance in patients with symptomatic low-grade isthmic spondylolisthesis. Fifty patients (28 women and 22 men; mean age $\pm$ standard deviation: 50 years $\pm$18.9) presenting with symptomatic low back pain with isthmic spondylolisthesis refractory to medical management were treated by means of trans-isthmic pars interarticularis percutaneous screw fixation. The procedure was performed under local anesthesia with double CT and fluoroscopic guidance. Primary outcome was technical success of the procedure, which was assessed with a post-procedure CT using the same success criteria as surgical screw placement with regard to entry point, trajectory, and screw tip. Secondary outcome was pain decrease assessed by the Visual Analog Scale (VAS). Ninety-nine procedures were performed in 50 patients and 99 screws were inserted. Postoperative CT assessment showed satisfactory screw placement in 96 cases, reflecting a technical success rate of 96.9%. No complications occurred during or after the procedure. Pain assessment showed a pain decrease of VAS score from a median of 7 (min 5, max 10; MAD 1.4) to 2 (p < 0.0001) (min 0, max 7, MAD 1.7) with a mean follow-up of 39 months. Trans-isthmic screw fixation performed under CT and fluoroscopic guidance presents a high technical success and appears as a safe procedure and effective procedure in patients with symptomatic low-grade isthmic lysis.