Optimal angle of needle insertion for fluoroscopy-guided transforaminal epidural injection of L5

Relationship between needle depth for lumbar transforaminal epidural injection and patients' height and weight using magnetic resonance imaging

Background

Optimal needle depth in transforaminal epidural injection (TFEI) is determined by body measurements and is influenced by the needle entry angle. Physician can choose the appropriate needle length and perform the procedure more effectively if depth is predicted in advance.

Methods

This retrospective study included patients with lumbosacral pain from a single university hospital. The skin depth from the target point was measured using magnetic resonance imaging transverse images. The depth was measured bilaterally for L4 and L5 TFEIs at 15°, 20°, and 25° oblique angles from the spinous process.

Results

A total of 4,632 measurements of 386 patients were included. The lengths of the left and right TFEI at the same level and oblique angle were assessed, and no statistical differences were identified. Therefore, linear regression analysis was performed for bilateral L4 and L5 TFEIs. The R-squared values of height and weight combined were higher than the height, weight, and body mass index (BMI). The following equation was established Depth (mm) = a – b (height, cm) + c (weight, kg). Based on the equation, maximal BMI capable with a 23G, 3.5-inch, Quincke-type point spinal needle was presented for three different angles (15°, 20°, and 25°) at lumbar levels L4 and L5.

Conclusions

The maximal BMI that derived from the formulated equation is listed on the table, which can help in preparations for morbid obesity. If a patient has bigger BMI than the one in the table, the clinician should prepare longer needle than the usual spinal needle.

Does the Position of the Polyaxial Screw Head in Patients With L5-S1 Stabilization Lead to an Increased Difficulty in L5 Transforaminal Nerve Injection? A Three-Dimensional Computerized Tomography Study

Background

Challenges may be encountered if transforaminal nerve injection (TFNI) is required in patients who have undergone posterior transpedicular stabilization (PTS) surgery to the L5-S1 level. In this study, we investigated the contributory factors that lead to these challenges.

Methods

We selected 125 patients who underwent PTS surgery involving the L5-S1 segment, between 18 to 70 years of age to be included in the study. The demographic data of the patients, body mass indexes (BMI), postoperative spondylolisthesis grades, heights of the iliac crest, and the positions of the polyaxial screw head were assessed. The shortest trajectory of L5-TFNI, the distance of the needle entry point (NEP) to the midline, and optimum viewing angles (VA) were measured on the three-dimensional computed tomography (CT) sections.

Results

Pre-PTS surgery, in males compared to females, NEP was noted to be more medial (p=0.007), the needle trajectory was shorter (p=0.001), and the optimal VA was narrower (p=0.001). Increasing BMI and increasing height of the iliac crest caused the TFNI trajectory to become longer. Post-PTS surgery, angulation of polyaxial screw heads of more than 15 degrees laterally in both genders significantly caused a decrease in VA (p=0.001).

Conclusions

Using the reconstruction technique in 3D CT, we demonstrated that pedicle screw heads angled laterally, a higher iliac crest height, and an increased BMI make L5-TFNI difficult to be performed. Locking the stabilization system while targeting the most neutral position for polyaxial screw heads during surgery may facilitate the L5-TFNI.

Comparison between anteroposterior and oblique "Scotty dog" approach during S1 transforaminal epidural steroid injection: A randomized controlled trial

BACKGROUND

Traditionally, S1 transforaminal epidural steroid injection (TFESI) has been performed using an anteroposterior (AP) fluoroscopic view. In 2007, the oblique "Scotty dog" (OS) approach was introduced as an alternative technique. We compared passage time of the needle into S1 foramen (Tf) between the anteroposterior (AP) and oblique "Scotty dog" (OS) approach during S1 TFESI.

METHODS

In this prospective randomized controlled trial, seventy patients scheduled S1 TFESI were randomly allocated into AP or OS groups. In the AP group, a slight cephalad-caudad tilt was used. In the OS group, the C-arm was rotated ipsilateral oblique degrees to view the S1 Scotty dog. Both groups received injection of steroid mixed with local anesthetics. We measured the passage time of the needle into S1 foramen (Tf), primary outcome, and total procedure time (Tt) between the groups. We also recorded presence of intravascular injection, patients-assessed pain relief for one month and complications.

RESULTS

The Tf and Tt were shorter in the OS than in the AP group (24.4 ± 24.0 s vs 47. 8 ± 53.2seconds; 93.3 ± 35.0 seconds vs 160.0 ± 98.7 seconds, P < .001, both). Incidence of intravascular injection (AP, 8 [22.8%]; OS, 4 [11.4%], P = .205), pain score, and complication rates were not statistically different between the two groups. In logistic regression analysis, the body mass index (BMI) was a risk factor for longer Tt (odds ratio [OR] = 1.27, 95% CI: 1.02-1.58, P = .030).

CONCLUSION

The passage time of the needle into S1 foramen was shorter in OS approach and the OS approach reduced the procedure time compared with the AP approach during S1 TFESI. The practitioners should note that procedure time can be prolonged in obese patients.

Deep Learning-Based Automatic Segmentation of Lumbosacral Nerves on CT for Spinal Intervention: A Translational Study

BACKGROUND AND PURPOSE

3D reconstruction of a targeted area ("safe" triangle and Kambin triangle) may benefit the viability assessment of transforaminal epidural steroid injection, especially at the L5/S1 level. However, manual segmentation of lumbosacral nerves for 3D reconstruction is time-consuming. The aim of this study was to investigate the feasibility of deep learning-based segmentation of lumbosacral nerves on CT and the reconstruction of the safe triangle and Kambin triangle.

MATERIALS AND METHODS

A total of 50 cases of spinal CT were manually labeled for lumbosacral nerves and bones using Slicer 4.8. The ratio of training/validation/testing was 32:8:10. A 3D U-Net was adopted to build the model SPINECT for automatic segmentations of lumbosacral structures. The Dice score, pixel accuracy, and Intersection over Union were computed to assess the segmentation performance of SPINECT. The areas of Kambin and safe triangles were measured to validate the 3D reconstruction.

RESULTS

The results revealed successful segmentation of lumbosacral bone and nerve on CT. The average pixel accuracy for bone was 0.940, and for nerve, 0.918. The average Intersection over Union for bone was 0.897 and for nerve, 0.827. The Dice score for bone was 0.945, and for nerve, it was 0.905. There were no significant differences in the quantified Kambin triangle or safe triangle between manually segmented images and automatically segmented images (P > .05).

CONCLUSIONS

Deep learning-based automatic segmentation of lumbosacral structures (nerves and bone) on routine CT is feasible, and SPINECT-based 3D reconstruction of safe and Kambin triangles is also validated.

The Effect of Skin Pressure on Needle Entry Point Accuracy During Fluoroscopically Guided Lumbar Transforaminal Epidural Injections: A Randomized Clinical Trial

OBJECTIVE

The aim of this study was to investigate the effect of skin pressure on needle entry point accuracy during fluoroscopically guided lumbar transforaminal epidural injection.

DESIGN

This study is a prospective randomized clinical trial; 64 patients with a body mass index of 25 kg/m or greater were enrolled. For patients in the pressing group, the operator marked the needle entry point on the patient's back while pressing the patient's skin with the tip of an indicator. For patients in the nonpressing group, the tip of the indicator was gently positioned on the patient's skin. The data related to technical performance and radiation exposure during the procedure were compared.

RESULTS

Sixty patients (nonpressing group, n = 30; pressing group, n = 30) were analyzed. There were more attempts to reposition the needle (n) and increased procedure time (in seconds) in the pressing group (median, 5 vs. 4 [P = 0.019]; 400.0 vs. 358.5 [P = 0.033]). The fluoroscopy time (in seconds) and the kerma-area product (in cGy cm) were also significantly longer and greater in the pressing group, respectively (median, 63.5 vs. 50.5 [P = 0.038]; 416.3 vs. 318.6 [P = 0.014]).

CONCLUSIONS

This study shows that practitioners should not press the skin with a radiopaque indicator when determining the needle entry point by fluoroscopy during lumbar transforaminal epidural injection.