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(A) Sagittal T2-weighted magnetic resonance (MR) imaging demonstrating a high-intensity zone (HIZ, arrow) of the L5/S1 intervertebral disc (IVD) at the posterior annulus. (B) Axial ultrasound (US) imaging of the L5/S1 interlaminar space showing the in-plane injection of the L5/S1 IVD. Note the needle shaft (void arrowheads) was partially blocked by the articular processes. Dashed arrow: posterior longitudinal ligament. Arrowhead: needle tip. (C) Paramedian sagittal oblique US imaging of the lumbar spine with the window between the tip of the transverse process and the superior articular process and (D) the window for interlaminar space showing the needle tip (arrowhead) within the IVD. Note the IVD was situated between the two hyperechoic bony cortex of vertebrae (^). The small inserts illustrate the transducer position and orientation.. Abbreviations: AP, articular process; ES, erector spinae; TP, transverse process; Lam, lamina.
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The trajectory of the needle was pointed to the center of lumbar IVD, passing just under the superior articular process and was slightly cranial to caudal to avoid hitting the nerve root which also courses caudally (Figures 1B and 2B). Then, the needle was advanced slowly until the needle tip reached the annular fibers of lumbar IVD which was located at the lower third between the two adjacent transverse processes (or between the L5 transverse and the sacral alar for L5/S1 IVD) (Figures 1C and 2C). Another method to confirm whether the needle tip was positioned within the IVD was by placing the transducer in the paramedian sagittal oblique view for the interlaminar space (Figure 1D).
PMC7245455_02
(A) Sagittal T2-weighted magnetic resonance (MR) imaging demonstrating a high-intensity zone (HIZ, arrow) of the L5/S1 intervertebral disc (IVD) at the posterior annulus. (B) Axial ultrasound (US) imaging of the L5/S1 interlaminar space showing the in-plane injection of the L5/S1 IVD. Note the needle shaft (void arrowheads) was partially blocked by the articular processes. Dashed arrow: posterior longitudinal ligament. Arrowhead: needle tip. (C) Paramedian sagittal oblique US imaging of the lumbar spine with the window between the tip of the transverse process and the superior articular process and (D) the window for interlaminar space showing the needle tip (arrowhead) within the IVD. Note the IVD was situated between the two hyperechoic bony cortex of vertebrae (^). The small inserts illustrate the transducer position and orientation.. Abbreviations: AP, articular process; ES, erector spinae; TP, transverse process; Lam, lamina.
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The trajectory of the needle was pointed to the center of lumbar IVD, passing just under the superior articular process and was slightly cranial to caudal to avoid hitting the nerve root which also courses caudally (Figures 1B and 2B). Then, the needle was advanced slowly until the needle tip reached the annular fibers of lumbar IVD which was located at the lower third between the two adjacent transverse processes (or between the L5 transverse and the sacral alar for L5/S1 IVD) (Figures 1C and 2C). Another method to confirm whether the needle tip was positioned within the IVD was by placing the transducer in the paramedian sagittal oblique view for the interlaminar space (Figure 1D).
(A) Sagittal T2-weighted magnetic resonance (MR) imaging demonstrating a high-intensity zone (HIZ, arrow) of the L4/5 and L5/S1 intervertebral discs (IVDs) at the posterior annulus. (B) Axial ultrasound (US) imaging of the L4/L5 interlaminar space showing the in-plane injection of the L4/L5 IVD. Note the needle tip was blocked by the articular processes. Dashed arrow: posterior longitudinal ligament. Void arrowheads: needle shaft. (C) Paramedian sagittal oblique US imaging of the lumbar spine with the window between the tip of the transverse process and the superior articular process showing the needle tip (arrowhead) within the IVD. Note the IVD was situated between the two hyperechoic bony cortex of vertebrae (^). The small insert illustrates the transducer position and orientation.. Abbreviations: AP, articular process; ES, erector spinae; TP, transverse process.
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The MRI revealed an HIZ at the posterior L4/5 and L5-S1 IVD, respectively (Figure 2A). PRP (ACP double syringe system, Arthrex, Germany) injection (3 mL) under US guidance was performed to the IVDs which produced the concordant pain (Figure 2B and C, Supplementary Video 2). The trajectory of the needle was pointed to the center of lumbar IVD, passing just under the superior articular process and was slightly cranial to caudal to avoid hitting the nerve root which also courses caudally (Figures 1B and 2B). Then, the needle was advanced slowly until the needle tip reached the annular fibers of lumbar IVD which was located at the lower third between the two adjacent transverse processes (or between the L5 transverse and the sacral alar for L5/S1 IVD) (Figures 1C and 2C).
The Kambin triangle (red dashed line) bordered by the exiting nerve root (the hypotenuse), the thecal sac (the asterisk, the height), and the superior border of the caudal vertebra (the width). Note the anatomic relationships of the transverse process, the exiting nerve root, and the intervertebral disc and the facet joint from cranial to caudal.
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The concept of the "Kambin triangle" was utilized in which the working triangle bordered by the exiting nerve root, thecal sac, and the caudal vertebral body allowed a safe triangular corridor for access of the dorsolateral IVD (Figure 3).