Keywords
intervention - tent - technique
Introduction
Several techniques have recently been described in the literature to aid image-guided
biopsy of osseous lesions.[1]
[2]
[3] All of them rely on a relatively even or flat skin surface to ensure needle stability.
In cases where there is uneven skin surface/dip in skin contour, a conventional biopsy
approach can be challenging. This is also true for parts of the body where prominent
angulation is needed, for example, in the posterior neck (cervical spine) or in cortical
and periosteal lesions where there is paucity of overlying soft tissue. We describe
an innovative, inexpensive, and simple technique of stabilizing and manipulating the
biopsy needle in the described situations. This has been termed the “Birmingham intervention
tent technique (BITT).”
Technique
BITT uses the surgical plastic forceps clamp, which is readily available in most operating
theater dressing packs. The clamp is applied directly to the biopsy needle. Depending
on the angle required, the clamp can be attached anywhere along the needle until stability
is achieved. The finger rings of the forceps are rested on the table or similar structure.
The angle made between the biopsy needle and clamp takes the shape of a tent ([Fig. 1]). A more obtuse angle is made by placing the clamp close to the needle tip; conversely,
a sharper angle is made by placing the clamp closer to the proximal end of the biopsy
needle. The clamp finger rings provide enough stability; in other words, no fixation
is needed for the patient. Furthermore, the weight of the applied clamp and two finger
rings is enough to counteract the weight of the biopsy needle, again ensuring stability.
If the needle needs to be advanced further, the clamp can be removed, the needle repositioned,
and clamp reapplied until it is firmly anchored in the bone. Informed consent were
obtained from patients.
Fig. 1 Illustration of the “XXXX intervention tent technique (BITT).” The biopsy needle
is held with a plastics forceps clamp, which is not attached to the drape. The weight
of the clamp alone is enough to support the weight of the biopsy needle.
Discussion
In the authors’ experience, BITT is an effective method for biopsying lesions where
a direct approach is not possible due to an uneven skin surface or difficult anatomic
access. It can also be used in lesions where an angulated approach, not directly perpendicular
to the CT beam, is needed. In such cases, using the biopsy needle alone in an angulated
manner with no accessory stabilizing force may result in instability and the needle
being displaced.
[Fig. 2] demonstrates the described technique. The lesion for biopsy was within the lateral
aspect of the C2 vertebral body. The natural hump of the shoulder and upper back meant
that the “SAHNA” technique was not possible, and presence of hair made use of the
“dual steristrip” technique difficult. To tackle this, an angulated approach was used
by attaching forceps clamp to the biopsy needle. The clamp allowed an angle to be
maintained without the needle falling out.
Fig. 2 The lesion within the left lateral aspect of the C2 vertebral body was to be biopsied.
As the shoulder was in the way for a direct approach, the clamp could be applied to
the needle and biopsied using an angulated entry point (A and B). The images (C and D) show how the clamp is positioned to the side of the patient, avoiding difficult
maneuvering over the shoulder/upper back.
BITT can also be used in other CT biopsy procedures. It can act as a guide to ensure
correct trajectory is maintained. It is especially helpful in cases where an angulated
entry point is required. [Fig. 3] illustrates the technique being used in biopsying lesions within the tibia and superior
pubic ramus. When the practitioner advances the needle, the clamp position aids the
radiologist to maintain the correct direction and angle. This is useful for osseous
lesions, where a direct approach perpendicular to the scanning plane is not feasible.
The technique is also helpful for bones where an angled approach may be used, for
example, the clavicle or pubic rami which have a natural anatomical angular inclination.
This should avoid angling the needle too inferior or superior, possibly missing the
correct part of the lesion. The clamp is also ideal for lesions where there is abundant
soft tissue, requiring a longer needle length, such as the posterior neck seen in
([Fig. 2]). Attaching the clamp as demonstrated is enough to balance even longer length needles.
Fig. 3 Lesions within the anterior tibia (A) and superior pubic ramus (B) biopsied using the “XXXXX intervention tent technique (BITT).” The correct biopsy
plane and trajectory can be easily planned and maintained by applying a clamp to the
biopsy needle.
In most institutions, radiologists may place a small needle tip in the skin to decide
a trajectory after local anesthetic is administered. With a clamp, the biopsy needle
tract can be optimized after skin entry, and then modified and maintained throughout
the procedure.
Currently, there are only three published techniques highlighting methods for stabilizing
CT biopsy needles. In the “dual steristrip” technique devised by McLoughlin and authors,
one steristrip is placed on the biopsy needle, proximal to the entry site, and the
other at roughly 90 degrees on the skin surface, away from needle entry point.[1] However, in cases where an angulated entry point is required, more steristrips are
needed for stabilization. There is always a risk that the steristrips will not hold
if stretched, leading to needle instability. Nabi and coauthors have recommended using
an inverted gallipot with a central hole to stabilize the biopsy needle.[2] The hole is made via a bone drill and then placed over the skin entry site. The
needle is then advanced through the hole and into the lesion. However, angling or
repositioning the needle may prove to be difficult, given the narrow hole aperture.
With a wider entry point, the angle may be too obtuse for the needle to fit through
the hole at the required position.
The “SAHNA” technique uses a mepore dressing, stuck down to the clamp roughly halfway
up its length.[3] This is ideal for balancing the needle in superficial osseous lesions where not
much bony purchase exists. However, it again may not be suitable for cases requiring
an angulated approach. Sticking the clamp down may even alter the angle of entry slightly;
the SAHNA technique is mainly recommended for superficial osseous lesions perpendicular
to the scanning plane.
Commercially available needle holders such as Seestar (Apriomed) and Simplify (NeoRad
AS) have been developed.[4] These are external devices which attach around the biopsy needle, forming a construct
to help in effective planning. However, they tend to increase biopsy time and there
is equivocal evidence as to whether they reduce hand radiation when compared with
a free hand technique.[5] It would also be very laborious to detach and reapply the device if multiple needle
adjustments are needed. The lack of extra radiation dose and ease of manipulation
in real-time allows the BITT to be used even in the most technically challenging situations.
