Kambin's Triangle Approach of Lumbar Transforaminal Epidural Injection with Spinal Stenosis

Abstract

Objective: To compare the short-term effect and advantage of transforaminal epidural steroid injection (TFESI) performed using the Kambin's triangle and subpedicular approaches.

Method: Forty-two patients with radicular pain from lumbar spinal stenosis were enrolled. Subjects were randomly assigned to one of two groups. All procedures were performed using C-arm KMC 950. The frequency of complications during the procedure and the effect of TFESI at 2 and 4 weeks after the procedure between the two groups were compared. Short-term outcomes were measured using a visual numeric scale (VNS) and a five-grade scale. Multiple logistic regression analyses were performed to evaluate the relationship between possible outcome predictors (Kambin's triangle or subpedicular approach, age, duration of symptoms and sex) and the therapeutic effect.

Results: VNS was improved 2 weeks after the injection and continued to improve until 4 weeks in both groups. There were no statistical differences in changes of VNS, effectiveness and contrast spread pattern between these two groups. No correlation was found between the other variables tested and therapeutic effect. Spinal nerve pricking occurred in five cases of the subpedicular and in none of the cases of the Kambin's triangle approach (p<0.05).

Conclusion: The Kambin's triangle approach is as efficacious as the subpedicular approach for short-term effect and offers considerable advantages (i.e., less spinal nerve pricking during procedure). The Kambin's triangle approach maybe an alternative method for transforaminal epidural steroid injection in cases where needle tip positioning in the anterior epidural space is difficult.

Keywords: Kambin's triangle; Lumbar; Stenosis; Transforaminal.

Fig. 1

Schematic description of the "Kambin's triangle". The triangle is defined by the hypotenuse, base, and height. The hypotenuse is the exiting nerve; the base is the caudad vertebral body; and the height is the traversing nerve root.

Fig. 2

Schematic description for transforaminal epidural steroid injection with the Kambin's triangle versus the subpedicular approach (target L5 nerve root).

Fig. 3

(A) Anterior-posteior view of the lumbar spine, with superimposed line (1) bisecting the pedicle. This line was drawn halfway between the farthest medial (2) and farthest lateral (3) points on the pedicle. (B) Lateral view of the lumbar spine, with the quadrant system superimposed. First, a line was drawn tangent to the curve of the spine at the level of interest along the posterior vertebral line. (1) A second line (2) was drawn parallel to the third at the posterior margina of the foramen. Next, two lines perpendicular to lines 1 and 2 were drawn at the superior and inferior margins of the foramen (3 and 4, respectively). Finally, line 5 was drawn bisecting 1 and 2, and, likewise, line 6 bisecting 3 and 4. This divided the foramen into four quadrants Arrow: needle position.

Fig. 4

Kambin's triangle approach of the L5 nerve root. (A) In the oblique view, the needle tip is advanced slowly and cautiously past the superior articular process lateral surface. (B) The anterior-posterior view will most often demonstrate the tip in the interpedicular line. (C) The lateral radiography should also be used while advancing past the SAP to minimize the risk of the penetration until the needle tip is at the posterior and inferior aspect of intervertebral neural foramen. (D) A small amount of contrast is used to confirm epidural spread.

Fig. 5

Subpedicular approach of the L5 nerve root. (A) In oblique view, needle tip lies directly inferior to the pedicle and inferolateral to the pars interarticularis. (B) The anterior-posterior view showing the proper location of the needle at the base of pedicle. (C) The lateral radiography should also be used while the needle is advanced until the needle tip is at the anterior and superior aspect of intervertebral neural foramen. (D) A small amount of contrast is used to confirm epidural spread.