Keywords
CT-guided spinal biopsy - C-arm guided spinal biopsy - vertebral biopsy - transpedicular
vertebral biopsy
Introduction
The technological advancements in magnetic resonance imaging (MRI) have increased
our understanding of the nature of spinal lesions; still, biopsy is needed in most
cases for histopathological confirmation and/ or microbiological assessment.[1] Historically, spinal biopsies were performed via open surgery, which involved increased
morbidity, a higher risk of complications, extended hospital stays, and a greater
likelihood of tumor spillage or contamination of adjacent tissues. In contrast, percutaneous
spine biopsy offers advantages such as being minimally invasive with lower infection
risk and “wound-related complications,” and it can usually be done on an outpatient
basis with local anesthesia. Complication rates for percutaneous biopsy are much lower
(1–3%) compared with open biopsy (16%).[1]
[2] Common approaches for spinal biopsy include computed tomography (CT) and C-arm guidance,
which enable precise needle placement. In this review article, we compare two different
imaging guidance methods based on patient-related and technical factors.
Preprocedural Planning and Preparation
Preprocedural Planning and Preparation
The planning for an image-guided spinal biopsy involves several critical steps to
ensure the procedure's safety and efficacy. This includes assessing the patient's
medical history, including their coagulation profile and any prior spinal procedures
or surgeries; reviewing previous spinal imaging to identify the target lesion and
nearby anatomy; and obtaining informed consent from the patient after explaining the
procedure, risks, and benefits. Additionally, determining the optimal approach and
trajectory for the biopsy needle based on the lesion's location and adjacent critical
structures is essential.
Image-guided spinal biopsy is generally safe when performed by an experienced interventional
radiologist; however, certain contraindications and considerations must be taken into
account to ensure patient safety and minimize risks. Absolute contraindications include
patient refusal or inability to provide informed consent, unstable vital signs or
severe coexisting medical conditions that pose a high risk during the procedure, severe
coagulopathy or bleeding disorders, and local skin infection at the biopsy site. Relative
contraindications include lesions located near critical structures such as major blood
vessels, the spinal cord, or nerve roots, pregnancy, and allergy to contrast media
(if contrast-enhanced imaging is needed). Although major complications from the percutaneous
biopsy are rare, they can include bleeding, infection, neurological compromise, pleural
puncture, and lung injury, tumor seeding, technical failure, and the risk of sinus
tract or fistula formation secondary to infection.[2]
[3]
Imaging Review and Site Selection
Imaging Review and Site Selection
Reviewing all pertinent imaging is essential in prebiopsy planning to optimize biopsy
success. Lesion enhancement observed on both MRI and CT scans assists in identifying
viable tissue for targeting. The increasing use of positron emission tomography in
assessing and staging spinal lesions, especially malignancies, aids in pinpointing
hypermetabolic areas that correlate with viable or hypercellular tissue, thus enhancing
diagnostic accuracy ([Fig. 1]). CT angiography may be required if there is a risk of vascular injury during the
biopsy procedure, particularly during cervical spine biopsies. In cases involving
multiple lesions, selecting the safest and most accessible lesion while balancing
procedural risk with diagnostic yield is critical.
Fig. 1 (A, B) A 34-year-old male with multiple avid lesions on positron emission tomography (PET);
(A) lesion in the left sacral ala was chosen for biopsy (arrow); and (B) computed tomography (CT)-guided biopsy of the left sacral was performed which revealed
lymphomatous infiltrate on histopathological evaluation.
The biopsy target is typically the hypermetabolic, enhancing, or most diffusion-restricting
part of the lesion to increase the likelihood of obtaining a diagnostic specimen.
Necrotic and cystic areas within the lesion are generally avoided. In cases where
the lesion contains both soft tissue and bony components, sampling both may be necessary
to acquire the complete histological spectrum. The type of lesion significantly affects
diagnostic yield, with metastatic lesions yielding more than primary neoplasms and
primary malignancies yielding more than benign lesions. Lesions characterized by osteolysis
or a mix of osteolytic and sclerotic features typically have higher diagnostic yields
than purely sclerotic lesions. Lesions associated with lower diagnostic yield include
lesions having fibrous and collagenous matrix, nonneoplastic inflammatory lesions,
and lesions having cystic spaces for example aneurysmal bone cysts and hemangiomas.
The size of the lesion also affects diagnostic yield; lesions smaller than 2 cm. are
associated with lower yield.[4]
[5]
The needle trajectory should avoid crossing critical neurovascular structures, for
example, exiting nerve roots, dural sac, and spinal cord, and must not pass through
infected areas to prevent the unintended spread or seeding of infection.[5]
Patient Positioning
Achieving the desired trajectory for a biopsy requires careful consideration of optimal
patient positioning. Patient comfort is paramount to ensure they can remain still
and cooperative during the procedure, especially if it is performed under local anesthesia
or conscious sedation. It is crucial to assess whether the patient can comfortably
maintain a specific position for an extended period.
For thoracic, lumbar, and sacral spinal biopsies, patients are positioned prone. For
cervical spine biopsies, the patient may be positioned prone, supine, or in lateral
decubitus depending on the specific level being targeted. The choice of position is
determined by the accessibility of the lesion and ensuring the patient's comfort and
safety throughout the procedure.
Needle Selection and Technical Factors
Needle Selection and Technical Factors
Different types of needles used in biopsy procedures can be categorized into three
main groups: “aspiration needles,” “core (cutting) needles,” and “trephine needles.”
The choice of needle depends on factors such as the nature of the lesion (whether
osseous or soft tissue) and its location.[6]
[7] In fine-needle aspiration cytology, the interventionist typically uses a small needle
bore (22–27 gauge) to obtain cytologic samples, which are mainly used to detect malignant
cells or diagnose infections. As the sample size obtained by this method is typically
small, this process suffers from lower diagnostic yield. Moreover, pathologists cannot
comment on tissue architecture or histologic grade making it a less preferred method
for diagnosing most musculoskeletal neoplasms.[7]
Core (cutting) needles are commonly used for lesions with accessible soft-tissue components.
Samples obtained with this method generally preserve the tissue architecture and allow
grading of musculoskeletal neoplasms. In cases where there is no accessible soft-tissue
component and the bone cortex needs to be punctured to access the pathologic tissue,
trephine needles come into the role. These needles are typically larger gauge needles
and have a “serrated or saw-tooth” cutting edge. Larger bore needles are associated
with an increased complication risk.
Utilizing a coaxial technique for biopsy allows multiple core samples to be obtained
from one access point while minimizing damage to surrounding structures and enhancing
patient comfort. The coaxial access needle can be used to control bleeding during
the procedure by replacing the stylet between passes to ensure hemostasis and injecting
autologous clots/gel foam or slurry.[7]
With the increasing demand for comprehensive testing of specimens, such as flow cytometry,
immunohistochemistry, and chromosomal analysis, larger tissue volumes are now preferred.
Therefore, core or trephine biopsy techniques are routinely employed to ensure adequate
sample collection. Crush artifact refers to specimen damage during the biopsy procedure,
which can be minimized by using a larger gauge needle to reduce tissue trauma.[7] In our institution, the minimum needle caliber used for soft tissue biopsies utilizing
a core biopsy needle is 16 gauge, while 11 gauge is used for bone biopsies utilizing
a trephine needle, or 13-gauge trephine needle for thinner pedicles and in pediatric
patients. This ensures sufficient tissue sampling while balancing the risk of complications
associated with larger needle sizes.
CT or C-Arm Guidance
CT-guided biopsy has become the preferred method for spinal biopsies due to its high
safety and accuracy rates exceeding 90%, with complication rates typically ranging
from 0 to 2%.[8] However, traditional CT imaging has drawbacks such as increased radiation exposure,
longer procedural times, and limited real-time guidance capabilities, particularly
in achieving a wide range of needle approach angles compared with C-arm. Axial imaging
of the curved spine can pose challenges in achieving optimal needle trajectories toward
lesions. Features like real or virtual gantry tilt can help address some of these
limitations, but certain situations may still require craniocaudal tilt or out-of-plane
imaging, complicating the procedure.[2]
C-arm guidance, when performed by experienced operators, offers advantages such as
reduced radiation exposure and shorter procedural durations. However, it has limitations
in visualizing soft-tissue structures and can be challenging in the complex anatomy
of critical areas like the cervical and upper thoracic spine. It has proven efficacy
in lower thoracic and lumbar biopsies. The development of CT-C-arm/C-arm cone-beam
CT with flat panel detector combines the cross-sectional imaging capabilities of CT
with real-time C-arm, enabling faster procedures and improved needle control during
intervention. It allows a complete volumetric data set acquisition covering a large
anatomic region of interest from which submillimeter isotropic reconstructions can
be created. CT fluoroscopy also combines the advantages of cross-sectional imaging
of CT and real-time tracking of fluoroscopy. Despite these benefits, CT-C-arm and
CT fluoroscopy involve significantly higher radiation exposure than traditional C-arm.
To mitigate this risk, thorough preoperative planning, adoption of low-dose protocols,
and careful monitoring of radiation exposure are essential measures.
Lumbar Spine
The transpedicular approach is commonly used for lumbar vertebral biopsy, whether
under CT or C-arm guidance, and is applicable across the spine where feasible to reduce
risks associated with bleeding and unintended seeding ([Fig. 2]). However, the posterior-central aspect of the vertebral body can represent a “potential
blind spot” with transpedicular approach, particularly under C-arm. C-arm is as effective
as CT for performing transpedicular lumbar vertebral biopsy, and patient preparation
remains consistent regardless of the imaging method used. Under CT guidance, the patient
is positioned prone, and the area of interest is cleaned and sterilized. Initial scout
images are acquired, followed by cross-sectional images covering the specific area
of interest to minimize radiation exposure. The interventional radiologist reviews
these images carefully to plan the entry site and needle trajectory, avoiding critical
structures while precisely targeting the lesion within the vertebral body ([Fig. 3]). Multiple images are captured during needle advancement to confirm accurate positioning
relative to the target lesion.[9]
Fig. 2 Schematic diagram demonstrates transpedicular (red arrow) and extrapedicular (blue
arrow) approaches of lumbar vertebral biopsy.
Fig. 3 (A, B) A 24-year-old female with suspicion of infective spondylodiscitis; (A) changes of spondylodiscitis L4 vertebral body (arrow); (B) transpedicular lumbar biopsy with a trephine biopsy needle having a coaxial system
was performed.
Under C-arm guidance, the target pedicle is identified using true anteroposterior
(AP) and lateral views. The C-arm is rotated to bring the medial cortex of the target
to the middle third of the vertebral body (barrel view). The vertebrae adopt a “Scottish
dog” configuration, for end-on needle placement (ipsilateral oblique by 15–20 degrees).
An optimal entry point is chosen, typically the center of the pedicle (Barrel view),
and the needle is advanced under real-time guidance on lateral view. It is crucial
to ensure the needle does not breach the medial border of the pedicle. Once the needle
reaches the posterior border of the vertebral body on the lateral view, an AP image
is obtained to confirm proper positioning within the pedicle. After that, the needle
can be safely advanced with a cephalocaudal inclination to reach the target area within
the vertebral body on lateral view ([Fig. 4]). After reaching the desired location, multiple tissue samples are collected from
various angles or depths to ensure diagnostic adequacy. It is important to choose
the trephine needle diameter relative to the pedicular size to avoid iatrogenic fracture
during insertion.[7]
Fig. 4 (A, B) A 29-year-old male with chronic back pain and fever underwent a C-arm-guided L3
vertebral biopsy. (A) Left anterior oblique (patient prone) C-arm image of the lumbar spine demonstrates
biopsy needle in end-on position over the left pedicle. (B) Lateral C-arm image of the lumbar spine demonstrates transpedicular vertebral biopsy
using a trephine needle with a coaxial system.
When the transpedicular approach becomes difficult and nonfeasible due to circumstances
like thin lumbar pedicles, or an open wound or scar in the posterior cutaneous or
subcutaneous plane, a posterolateral extrapedicular approach can be used. In this
technique, the needle trajectory is directed through the psoas muscle, or posteromedial
to the psoas outside pedicle to access the vertebral body ([Fig. 5]). Care must be taken to avoid misdirection of the needle posteromedial toward the
neural foramen and anteromedially toward the aorta/iliac arteries. However, this approach
carries potential risks, including injury to the aberrant spinal artery or radicular
artery, as well as an increased risk of retroperitoneal hematoma or pseudoaneurysm
formation. It is important to note that this approach is not suitable for use under
C-arm guidance.[9]
Fig. 5 Axial prone computed tomography (CT) image of D11 vertebrae having right pedicular
erosion demonstrates the posterolateral approach of vertebral biopsy.
Dorsal Spine
For biopsy of lesions located in the dorsal spine, CT guidance is preferred over C-arm
guidance, particularly in the upper dorsal spine, due to the proximity of critical
structures such as the lungs, pleura, and aorta, which present significant challenges
for selecting a biopsy approach. In the dorsal spine, needles can be approached through
various methods, including transpedicular, transforaminal, or costotransverse approaches
([Fig. 6]).[10] The costotransverse approach is favored in the dorsal spine, with the inferior costotransverse
approach used in the upper dorsal spine and the superior costotransverse approach
employed in the mid and lower dorsal spine ([Fig. 7]). In this approach, the interventionist uses costotransverse space, a potential
space between ribs and transverse process of the dorsal vertebra. This approach minimizes
the risk of injury to the pleura and nerve roots; however, due to fixation of the
needle in the space makes it difficult to change the needle trajectory, thus limiting
the area available to sample.[9] This approach can become difficult to use in cases of costovertebral joint arthrosis.
Fig. 6 Schematic diagram demonstrates transpedicular (red arrow) and costotransverse (blue
arrow) approaches of dorsal vertebral biopsy.
Fig. 7 (A, B) Axial prone computed tomography (CT) images of D4 vertebrae (A) and D10 vertebrae (B) demonstrate inferior costotransverse and superior costotransverse approaches of
vertebral biopsy, respectively.
The lower dorsal vertebrae can be approached safely under C-arm guidance by experienced
hands through transpedicular approach, provided the pedicular width is sufficient
for the biopsy needle to pass safely without breaching to medial cortex of the pedicle
([Fig. 8]). However, in narrow pedicle, costotransverse approach can be employed. On the oblique
C-arm view, the needle is targeted to the costotransverse joint lateral to the pedicle.
Once the needle is fixed into the costotransverse space, and at the posterior vertebral
margin on the lateral view, the fluoroscope is rotated to the AP view, to check the
needle at the superolateral/lateral margin of the pedicle. The medial cortex of the
pedicle should not be breached. The needle is then inserted into the vertebral body
and tracked on the lateral view. After reaching the desired location, a biopsy is
taken ([Fig. 9]).
Fig. 8 (A, B) C-arm images of the dorsolumbar spine demonstrate a biopsy needle in an end-on position
over the left pedicle of D12 vertebrae on left anterior oblique projection (A), and a transpedicular approach of vertebral biopsy using a trephine needle on lateral
projection (B).
Fig. 9 (A, B) C-arm images of the dorsal spine demonstrate a biopsy needle at the costotransverse
joint of D7 vertebrae on left anterior oblique projection (A), and the costotransverse approach of vertebral biopsy using trephine needle on lateral
projection (B).
For the lower dorsal spine, CT and C-arm both are considered safe. However, for upper
dorsal vertebrae, CT is preferable to C-arm for vertebral biopsy.
Sacrum
For nearly all sacral lesions, a straightforward posterior or posterolateral approach
using CT or C-arm is considered feasible and should be utilized whenever possible
([Fig. 10]). It is important to avoid transrectal and transabdominal approaches due to the
significant risk of biopsy tract contamination and potential tumor seeding.
Fig. 10 Lateral C-arm image of sacrum demonstrates biopsy of S2 vertebrae.
Cervical Spine
For biopsies of lesions located in the cervical spine, it is recommended to use CT
guidance rather than C-arm guidance to ensure precision and accuracy. Given the proximity
of vital structures such as the carotid artery, vertebral artery, jugular vein, trachea,
and esophagus, these procedures should always be performed by experienced professionals
under CT guidance to minimize the risk of serious complications. Various approaches
can be employed depending on the specific location of the lesion within the cervical
spine, with the patient positioned supine, in lateral decubitus, or prone position.
A small amount of nonionic intravenous iodinated contrast should be injected to highlight
key vascular structures (carotid artery, jugular vein, vertebral artery) and prevent
accidental vessel injury.
In the anterolateral/lateral approach, the biopsy needle is advanced anterior to the
sternocleidomastoid muscle and posteromedial to carotid sheath and the trachea ([Fig. 11]). The right side is preferred to prevent injury to the esophagus. Through this approach,
the interventionist can target the anterior aspect of the vertebral bodies, intervertebral
discs, and transverse processes. In the posterolateral approach, the needle trajectory
is through the sternocleidomastoid muscle and just posterior to the carotid sheath
to target lesions involving lateral masses, pedicles, transverse processes, and lamina.
Caution must be exercised as the vertebral artery is particularly vulnerable due to
its passage through the transverse foramen ([Fig. 12]). The posterior approach can be used to target posterior element lesions by advancing
the needle through the paraspinal muscles with caution to avoid penetrating spinal
canal and dural lining.
Fig. 11 Schematic diagram demonstrating anterolateral/lateral (red arrow) approach of cervical
vertebral biopsy.
Fig. 12 (A, B) Axial computed tomography (CT) image of the cervical spine demonstrates the right
lateral approach of C5 vertebral body biopsy (A) and posterolateral approach of C2 posterior element biopsy (B).
The transoral approach can be used for lesions located in the C1 and C2 vertebrae.
The needle is typically advanced through the posterior pharynx, retropharyngeal space,
and prevertebral musculature to reach the bone avoiding critical neurovascular structures.
Each of these approaches has specific considerations and potential risks, highlighting
the importance of precise planning and execution under CT guidance to ensure the safety
and efficacy of cervical spine biopsies.[9]
[11]
In a systematic review and meta-analysis by Michalopoulos et al, CT-guided biopsies
for spinal lesions demonstrated a “high diagnostic yield of 91%” and “diagnostic accuracy
of 86%,” with a “low complication rate of 1%.” The diagnostic yield was consistent
across different lesion locations, lesion types (lytic, sclerotic, mixed), and needle
types (wide- and thin-bore).[8] Similarly, Daniels and Chazen reported comparable findings in their study.[12]
Zakaria Mohamad et al compared C-arm and CT-guided transpedicular biopsy for spinal
lesions and found no statistically significant difference in accuracy (p = 0.731) and adequacy (p = 0.492) between the two methods.[13] Diffre et al evaluated disco-vertebral biopsy under C-arm versus CT guidance in
patients with pyogenic vertebral osteomyelitis with negative blood cultures. They
reported a higher yield (69.4%) under C-arm guidance compared with CT guidance (33.3%).[14]
Lee et al conducted a prospective randomized trial comparing C-arm and CT-guided biopsy
techniques and found similar accuracy, procedure time, complication rate, and pain
score between both groups.[15] Oka et al also reported no difference in diagnostic accuracy between C-arm and CT-guided
biopsies.[16]
Mireles-Cano et al demonstrated an effectiveness of 83% for diagnosing vertebral destruction
syndrome using transpedicular percutaneous biopsy guided by C-arm.[17] Overall, these studies highlight the efficacy and safety of both CT-guided and C-arm-guided
biopsy techniques for diagnosing spinal lesions, with comparable diagnostic outcomes
and complication rates.
Special Considerations
In cases of spondylodiscitis, a biopsy should be obtained from the endplate as well
as the disc ([Fig. 13]). It is recommended to withhold antimicrobial therapy for up to 2 weeks to maximize
microbiological yield, although this recommendation is based on limited literature.
Targeting paraspinal fluid collections or soft tissue abnormalities for sampling,
acquiring multiple core samples if possible, and using larger gauge needles can improve
yield.[18]
[19] The microbiological yield of repeat CT-guided biopsy for suspected infectious spondylodiscitis
is generally low, with higher yield observed in younger patients not exposed to prebiopsy
antibiotics.[20] Paravertebral soft-tissue changes, even in the absence of a paravertebral abscess,
may be considered a viable target for biopsy in cases of spondylodiscitis.[21] Factors affecting microbiologic yield in CT-guided spine biopsies include the time
from the initial referral of spinal symptoms to the procedure, with earlier biopsies
in the acute phase of infection associated with increased yield. Needle size (11–13G
vs. 16–18G) and site of biopsy (disc vs. bone vs. disc plus endplate) do not significantly
affect yield. However, thin or degenerated intervertebral discs on MRI are negative
factors for positive cultures.[22] Biopsies performed with handheld drill require less conscious sedation compared
with manual biopsies and yield longer bone core specimens for histopathologic evaluation.[23]
[24] For cystic osseous lesions, the conventional approach using a trephine or tru-cut
biopsy needle often fails to provide sufficient samples, necessitating aspiration
biopsy instead. To perform a successful aspiration biopsy, it is essential to extract
the lesion's contents and scrape its walls. This process involves maintaining consistent
negative pressure on the syringe, which can be challenging during bone biopsies where
one hand must exert significant pressure on the plunger while the other manipulates
the needle within the lesion. In such cases, a practical new method called the “needle
cap technique” can be utilized, enabling the operator to work with both hands for
better control and manipulation of the biopsy needle.[25]
Fig. 13 (A, B) Sagittal reconstructed computed tomography (CT) (A) and lateral C-arm (B) images of the lumbosacral spine of two different patients demonstrate endplate-disc
complex biopsy through a transpedicular approach.
Postbiopsy Consideration and Handling of Samples
Postbiopsy Consideration and Handling of Samples
After completing the biopsy, the needle is withdrawn, and pressure is applied to the
biopsy site to control bleeding, followed by the application of a sterile dressing.
The patient is monitored briefly in the recovery area to ensure stability and detect
any immediate postprocedure complications. Following a dorsal spine biopsy, a postprocedure
CT scan of the lungs may be necessary if pneumothorax is suspected. The duration of
postbiopsy observation varies depending on the procedure's invasiveness and whether
sedation was used.
Institutions have varying protocols for handling specimens based on suspected diagnoses;
it is crucial to communicate with the pathologist to ensure proper processing postcollection.
Typically, specimens are placed in separate sterile containers with normal saline
and formalin. Both saline and formalin containers are sent regardless of imaging findings
to rule out atypical infection in suspected malignancies and potential malignancy
in suspected infections.
Despite adequate preparation and technique, approximately 8 to 10% of biopsies yield
nondiagnostic or insufficient samples.[18] After a negative result, one may consider repeating the percutaneous biopsy, attempting
an open biopsy, targeting a different site, or opting to monitor the lesion with serial
imaging. A multidisciplinary tumor board's input is essential for decision-making.
For heterogeneous lesions or suspected infections, a repeat biopsy is often performed.
In one study, a second needle biopsy provided a diagnosis in 60% of spondylodiscitis
cases that initially had negative results. Generally, biopsy attempts are limited
to three or four times due to low diagnostic yield beyond this threshold.[19]
Conclusion
In conclusion, image-guided percutaneous spinal biopsy, utilizing CT or C-arm guidance,
is a highly effective and minimally invasive procedure for diagnosing spinal lesions.
A comparative analysis between the two modalities is summarized in [Table 1]. Both imaging techniques offer distinct advantages depending on the location and
complexity of the lesion. CT guidance excels in its accuracy and ability to visualize
soft tissue, making it ideal for anatomically challenging regions such as the cervical
and upper thoracic spine. On the other hand, C-arm guidance offers reduced radiation
exposure and shorter procedural times, particularly in the lumbar and lower thoracic
regions. When a lesion with both osseous as well as soft tissue components needs to
be sampled, CT scores over C-arm. The choice between these two techniques is often
guided by patient-specific factors, such as lesion location, proximity to critical
structures, procedural risk, as well as the expertise of an intervention radiologist
in using the particular modality. Regardless of the imaging modality, proper preprocedural
planning, site selection, and needle technique are crucial for maximizing diagnostic
yield while minimizing complications.
Table 1
A comparative analysis of CT- versus C-arm-guided spinal biopsy
|
CT
|
C-arm
|
|
Plane of acquisition
|
Axial
|
End-on view, profile view, oblique view
|
|
Contrast resolution
|
High
|
Low
|
|
Real time monitoring
|
Limited
|
Yes
|
|
Radiation exposure
|
More
|
Less
|
|
Procedure time
|
More
|
Less
|
|
Lumbar spine biopsy
|
Both CT and C-arm are equally effective
|
|
Dorsal spine biopsy
|
CT is preferable than C-arm, particularly for upper dorsal spine
|
|
Cervical spine biopsy
|
CT is recommended
|
|
Sacral biopsy
|
Both CT and C-arm are equally effective
|
Abbreviation: CT, computed tomography.
