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Caudal Epidural Steroid Injection
Caudal Epidural Steroid Injection: Ultrasound Guidance Denise Norton, Paul S. Lin, and Michael B. Furman This approach utilizes ultrasound for sacral cornua identification and allows driving live under in-plane guidance into the caudal epidural space. This view is similar to a fluoroscopic lateral view but with no radiation.
Note: Please see pages ii and iii for a list of anatomic terms/abbreviations used throughout this book.
CHAPTER
7C
Chapter 7C Caudal Epidural Steroid Injection: Ultrasound Guidance
In-Plane Technique (Fig. 7C.1) Have the patient in the prone position and place pillows under the pelvis to help with anatomic visualization. Ultrasound image on the opposite side as interventionist and in line with the transducer (see Fig 7C.1A and Chapter 4). n Utilize a curvilinear transducer for patients with more posterior adipose tissue and a gel stand off for patients with limited adipose tissue (not shown). n If the tissue obscures the transducer, consider taping the buttocks laterally to obtain the appropriate field for needle placement. n Tent the patient’s skin prior to needle insertion. n Palpate the sacral hiatus with a sterile gloved hand. This is the entry point for the spinal needle. The sacral hiatus should be palpated prior to placing the ultrasound probe. n Begin with the transducer in the short axis to the sacrum, midline and proximal to the sacral hiatus, and then track distally over the two sacral cornua. The sacral cornua appear as two hyperechoic reversed U-shaped structures. In the center of the image is a hypoechoic region, the sacral hiatus, bordered by two hyperechoic bands, the sacrococcygeal ligament superiorly and the dorsal surface of the sacrum inferiorly. n Rotate the transducer by 90 degrees with the long axis to the sacrum, visualizing the sacrum and sacral canal. n Insert the spinal needle from caudad to cephalad into the sacral epidural space with an in-plane technique. A “pop” is felt once the sacrococcygeal ligament is pierced. n Scan the needle and sacral hiatus in long and short axes to verify that the needle is traveling along the midline. The needle tip can also be directed to allow the injectate toward the more symptomatic side. n The initial placement can be made in short axis, out-of-plane, and rotating 90 degrees to confirm the placement before advancing in long axis in-plane. n Once the needle is advanced into the sacral canal, within the caudal epidural space, it cannot be visualized with ultrasound. n n
II
A Fig. 7C.1. A, Room and interventionalist setup for injection.
142
In-Plane Technique Median L5 spinous sacral crest process Sacrum Sacral hiatus S1 foramen
Multiplanar view
II
B D
Sacral hiatus
Multiplanar view Coccyx
Safety view
Sacrum
Bowel
SN
C
Fig. 7C.1. B, Ultrasound image of caudal epidural needle placement within the sacral canal in-plane or long axis. C, Drawing of relevant radiolucent structures. Yellow dashed line represents borders of the image seen on ultrasound in Fig. 7C.1A. Note the intestine in pink, which is not visible with ultrasound. D, Skeleton with the probe. Proper placement of ultrasound transducer for in-plane or long-axis placement.
In-Plane Technique Safety Considerations Too steep of an entry angle will not allow needle entry superiorly into the sacral canal. This is a common mistake when first performing this injection. n A steep trajectory angle has more potential to pass through the sacrum into the viscera. n Stay below S3 to avoid dural puncture. n
143
Chapter 7C Caudal Epidural Steroid Injection: Ultrasound Guidance
Out-of-Plane Confirmation (Fig. 7C.2) After epidural placement with in-plane technique, rotate the probe 90 degrees to an out-of-plane, short-axis view to reconfirm the epidural needle tip position. n This view is helpful to ensure that the needle is midline or ipsilateral to the side of pain depending on clinical goals. n
II Median L5 spinous sacral crest process Sacrum Sacral hiatus S1 foramen
Multiplanar view
Out-of-plane
A
Sacral cornu
Sacral hiatus
C
Multiplanar view Filum terminale Safety view
B
Fig. 7C.2. A, Ultrasound image of the sacral canal with the spinal needle in the caudal epidural space in short-axis, out-of-plane confirmation. B, Drawing of relevant structures. Yellow dashed line represents borders of image seen in Fig. 7C.2A. Note the yellow dot within the sacral canal; this represents the filum terminale, which is not visible with ultrasound. C, Skeleton with probe. Proper placement of ultrasound probe for out-of-plane or short-axis confirmation.
Out-of-Plane Technique Safety Considerations Same considerations as for the in-plane technique.
n
144
Suboptimal Image
Optimal Images Placement in the epidural space is confirmed with contrast-enhanced real-time fluoroscopy. Ideally, the contrast flow should be more localized to the symptomatic side. n Epidural fat gives an irregular appearance. n The contrast should spread cephalad to the symptomatic level. However, this may be limited in cases of central stenosis or prior surgery. For optimal and suboptimal fluoroscopically guided images, see Chapter 7A, Caudal Epidural Steroid Injection—Shallow Angle Approach. n n
Suboptimal
In plane
Fig. 7C.3. Ultrasound image of needle too shallow. Epidural access will not be achieved without needle repositioning.
145
II
Suboptimal Image (Fig. 7C.3)
Note: Please see pages ii and iii for a list of anatomic terms/abbreviations used throughout this book.
CHAPTER
7C
Chapter 7C Caudal Epidural Steroid Injection: Ultrasound Guidance
In-Plane Technique (Fig. 7C.1) Have the patient in the prone position and place pillows under the pelvis to help with anatomic visualization. Ultrasound image on the opposite side as interventionist and in line with the transducer (see Fig 7C.1A and Chapter 4). n Utilize a curvilinear transducer for patients with more posterior adipose tissue and a gel stand off for patients with limited adipose tissue (not shown). n If the tissue obscures the transducer, consider taping the buttocks laterally to obtain the appropriate field for needle placement. n Tent the patient’s skin prior to needle insertion. n Palpate the sacral hiatus with a sterile gloved hand. This is the entry point for the spinal needle. The sacral hiatus should be palpated prior to placing the ultrasound probe. n Begin with the transducer in the short axis to the sacrum, midline and proximal to the sacral hiatus, and then track distally over the two sacral cornua. The sacral cornua appear as two hyperechoic reversed U-shaped structures. In the center of the image is a hypoechoic region, the sacral hiatus, bordered by two hyperechoic bands, the sacrococcygeal ligament superiorly and the dorsal surface of the sacrum inferiorly. n Rotate the transducer by 90 degrees with the long axis to the sacrum, visualizing the sacrum and sacral canal. n Insert the spinal needle from caudad to cephalad into the sacral epidural space with an in-plane technique. A “pop” is felt once the sacrococcygeal ligament is pierced. n Scan the needle and sacral hiatus in long and short axes to verify that the needle is traveling along the midline. The needle tip can also be directed to allow the injectate toward the more symptomatic side. n The initial placement can be made in short axis, out-of-plane, and rotating 90 degrees to confirm the placement before advancing in long axis in-plane. n Once the needle is advanced into the sacral canal, within the caudal epidural space, it cannot be visualized with ultrasound. n n
II
A Fig. 7C.1. A, Room and interventionalist setup for injection.
142
In-Plane Technique Median L5 spinous sacral crest process Sacrum Sacral hiatus S1 foramen
Multiplanar view
II
B D
Sacral hiatus
Multiplanar view Coccyx
Safety view
Sacrum
Bowel
SN
C
Fig. 7C.1. B, Ultrasound image of caudal epidural needle placement within the sacral canal in-plane or long axis. C, Drawing of relevant radiolucent structures. Yellow dashed line represents borders of the image seen on ultrasound in Fig. 7C.1A. Note the intestine in pink, which is not visible with ultrasound. D, Skeleton with the probe. Proper placement of ultrasound transducer for in-plane or long-axis placement.
In-Plane Technique Safety Considerations Too steep of an entry angle will not allow needle entry superiorly into the sacral canal. This is a common mistake when first performing this injection. n A steep trajectory angle has more potential to pass through the sacrum into the viscera. n Stay below S3 to avoid dural puncture. n
143
Chapter 7C Caudal Epidural Steroid Injection: Ultrasound Guidance
Out-of-Plane Confirmation (Fig. 7C.2) After epidural placement with in-plane technique, rotate the probe 90 degrees to an out-of-plane, short-axis view to reconfirm the epidural needle tip position. n This view is helpful to ensure that the needle is midline or ipsilateral to the side of pain depending on clinical goals. n
II Median L5 spinous sacral crest process Sacrum Sacral hiatus S1 foramen
Multiplanar view
Out-of-plane
A
Sacral cornu
Sacral hiatus
C
Multiplanar view Filum terminale Safety view
B
Fig. 7C.2. A, Ultrasound image of the sacral canal with the spinal needle in the caudal epidural space in short-axis, out-of-plane confirmation. B, Drawing of relevant structures. Yellow dashed line represents borders of image seen in Fig. 7C.2A. Note the yellow dot within the sacral canal; this represents the filum terminale, which is not visible with ultrasound. C, Skeleton with probe. Proper placement of ultrasound probe for out-of-plane or short-axis confirmation.
Out-of-Plane Technique Safety Considerations Same considerations as for the in-plane technique.
n
144
Suboptimal Image
Optimal Images Placement in the epidural space is confirmed with contrast-enhanced real-time fluoroscopy. Ideally, the contrast flow should be more localized to the symptomatic side. n Epidural fat gives an irregular appearance. n The contrast should spread cephalad to the symptomatic level. However, this may be limited in cases of central stenosis or prior surgery. For optimal and suboptimal fluoroscopically guided images, see Chapter 7A, Caudal Epidural Steroid Injection—Shallow Angle Approach. n n
Suboptimal
In plane
Fig. 7C.3. Ultrasound image of needle too shallow. Epidural access will not be achieved without needle repositioning.
145
II
Suboptimal Image (Fig. 7C.3)