The technical feasibility and preliminary results of minimally invasive endoscopic-TLIF based on electromagnetic navigation: a case series

Abstract

Background: Uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion (Endo-TLIF) with percutaneous pedicle screw fixation is a promising, minimally invasive method for the treatment of lumbar spondylolisthesis. However, repeated radiation exposure from X-rays and the steep learning curve remain to be improved.

Methods: This retrospective study explored the effects of electromagnetic navigation on improving Endo-TLIF with percutaneous pedicle screw fixation. Clinical information from 42 patients who had received Endo-TLIF with percutaneous pedicle screw fixation from May 2019 to November 2020 was analyzed retrospectively. The procedures were assisted under electromagnetic navigation. The rate of adjustment for guide wires, frequency of X-ray exposure, operative time, accuracy of pedicle screw location, and clinical outcomes were recorded.

Results: The mean follow-up for 42 patients was 11.9 ± 3.1 months. The mean age of the patients was 56.1 ± 9.26 years, with a female/male ratio of 25:17. According to postoperative CT scans and 3D reconstructions, the excellent and good rate of pedicle screws was 96.4%. The rate of adjustment for guide wires under the assistance of electromagnetic navigation was 1.78%, and the frequency of X-ray exposure was 8.27 ± 1.83. The operative time was 167.25 ± 28.16 min, including the duration of guide wire insertion (14.63 ± 5.45 min) and duration of decompression and cage placement (75.43 ± 13.97 min). The duration of hospitalization after operation was 2.59 ± 1.16 days. The preoperative VAS score was 7.51 ± 1.91, and the preoperative ODI was 82.42 ± 8.7%. At the last follow-up, the VAS score was 2.09 ± 0.59, and the ODI was 11.09 ± 3.2%. There were statistically significant improvements in the VAS score and ODI in all patients at the follow-up (p < 0.05).

Conclusions: Electromagnetic navigation can provide accurate positioning and guidance in real time, which improves the surgical efficiency of percutaneous pedicle screw placement and endoscopic decompression in Endo-TLIF with reduced radiation exposures.

Keywords: Electromagnetic navigation; Endo-TLIF; Lumbar spondylolisthesis; Percutaneous pedicle screw.

Fig. 1

Preparation of electromagnetic navigation. a After the field generator and a patient tracker equipped with signal coils were fixed on the ilium, anteroposterior, and lateral fluoroscopic views of the lumbar segment were taken. b, c The software made surface matching on the respective vertebral body and compared the preoperative CT data in the electromagnetic coordinate system

Fig. 2

The incision design. According to C-arm positioning, bilateral iliac crest and pedicles were marked. In the electromagnetic navigation group, the incision was determined under the guidance of the Access Tracker, which could demonstrate the precise position of the trajectory to the pedicle. In the conventional group, the incision was roughly 5 cm to 6 cm away from the median spinous process

Fig. 3

The application of electromagnetic navigation in multiple procedures. a, b Guide wire insertion. In the navigation system, the procedure and track of the Access Tracker were visible in all spatial planes in real time so the operator could make quick adjustment if needed. c After the uniportal endoscope was placed, the endoscopic anatomical structures such as S1 superior facet joint, L5 inferior facet joint tip, and isthmus could be recognized by Access Tracker in the navigation system. It also could assist with recognizing the location of the intervertebral disc for severe intervertebral collapse. d The Access Tracker evaluated the depth of processed intervertebral space

Fig. 4

Images obtained in Case 1. a Preoperative images show grade 2 isthmic spondylolisthesis of L5; the intervertebral space almost disappeared, and there were huge osteophytes at the posterior margin of the vertebral body. b Electromagnetic navigation assisted with recognizing endoscopic facet joint and collapsed intervertebral space. c Postoperative images show that the reduction of spondylolisthesis and position of pedicle screws were perfect

Fig. 5

Images obtained in Case 2. a The X-ray fluoroscopy after cage insertion showed that the position of the left L5 pedicle guide wire was not satisfactory. b The surgeon adjusted the direction of the screws under the guidance of navigation again, ignoring the change in anatomical structure after slippage reset and intervertebral space restoration. c Postoperative X-ray fluoroscopy showed that the position of the left L5 pedicle screw was inward and upward, and the patient suffered from left lower extremity pain and numbness. d After a revision surgery to replace the left L5 pedicle screw, his left lower extremity symptoms were significantly relieved