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In-Depth Information
12 Facet Joint Injections with Tracked Ultrasound
Snapshots
Facet joint injections are done routinely on a relatively large patient population with
chronic back pain. The current standard of practice is either
fluoroscopic or CT-
guided needle placement. Ultrasound offers a radiation-free alternative to image
guidance [
13
,
14
], but it has not become a routine clinical procedure due to its
dif
fl
culty. Tracked ultrasound improves the accuracy of needle placement when it is
fused with a previous CT scan [
15
]. However, a CT scan is not always available for
these procedures. In this section we describe the TUSS-guided facet joint injections,
which potentially facilitates ultrasound-only guidance in facet joint injections.
Since needles can access the facet joints only in a constrained range of angles,
real-time ultrasound guidance is inconvenient. TUSS allows the procedure to be
separated in an imaging phase and a needle insertion phase. Initially, the operator
finds the target facet joint, and records one or more ultrasound snapshots at the
target. Then the ultrasound transducer is not needed during needle insertion, as the
operator guides the needle tip to the targets de
ned on the snapshots.
Operator performance in TUSS-guided facet joint injections was compared to
conventional ultrasound guidance in a cadaveric lamb model [
16
] (Fig.
14
). Success
rate and insertion time improved signi
cantly in a pilot study (Table
2
).
Fig. 14 Dual 3-D navigation scene for facet joint injection with registered CT-derived spine
model in a lamb specimen. Radiographs on the right con
rm the needle position (arrows point at
the needle)
Table 2 Operator
performance in TUSS-guided
versus conventional US-
guided facet joint injections in
a lamb model
TUSS guidance
US guidance
Number of insertions
50
50
Success rate (%)
*94
44
Insertion time (s
±
SD)
*36.1
±
28.7
47.9
±
34.2
*p < 0.05 versus Freehand US guidance
