Clinical Outcomes Based on Preoperative Kambin's Triangular Working Zone Measurements on 3D CT/MR Fusion Imaging to...

Transforaminal endoscopic lumbar diskectomy (TELD) is a widely used minimally invasive surgical procedure to treat herniated disks. Postoperative dysesthesia (POD) is a significant complication that affects patient satisfaction. Several anatomical and magnetic resonance (MR) imaging studies of the intervertebral foramina showed that TELD should be avoided in patients with small Kambin's triangular working zones. Recently, some reports indicated the usefulness of three-dimensional (3D) computed tomography/magnetic resonance (CT/MR) fusion images. To date, no articles have been published in the English literature regarding the use of 3D CT/MR fusion images before TELD to evaluate Kambin's triangular working zone. Our objective was to examine clinical outcomes when preoperative Kambin's triangular working zone measurements from 3D CT/MR fusion images were used to determine the approach to TELD.

We included 31 patients who underwent TELD. We rotated the 3D CT/MR fusion images from the posteroanterior view on the approach side to the angle at which Kambin's triangular working zone appeared the largest. This was used to determine the intraoperative insertion angle for the working cannula. When the perpendicular line extending from the exiting nerve at the intervertebral disk level to the upper margin of the superior articular process (exiting nerve-superior articular process distance [ESD]) was less than or equal to 7 mm, an approach that combined foraminoplasty with an outside-in technique (F + outside-in) was used. We compared ESD and clinical outcomes, such as POD, between the approaches.

Surgical plans were based on ESD values from 22 patients. ESD was 7 mm in 21 patients, all of whom underwent F + outside-in. The inside-out approach was used in eight of nine patients who did not have ESD measurements. Of these, five patients had retrospective ESD measurements of 7 mm. The mean ESD was 6.3 ± 1.0 mm when inside-out was used and 4.4 ± 1.6 mm when F + outside-in was used, a significant difference. Significant improvements were observed in the visual analog scale scores for low back pain, lower limb pain, and lower limb paresthesia. There were no incidences of POD or intraoperative complications.

Based on preoperative Kambin's triangular working zone measurements from 3D CT/MR fusion images, F + outside-in should be selected when the working zone is smaller than the cannula diameter. This method successfully avoided POD in our study. Preoperative Kambin's triangular working zone measurements from 3D CT/MR fusion imaging can enhance patient safety during TELD.