International Journal of Computer Assisted Radiology and Surgery (2018) 13:895–904
Robotic ultrasound-guided facet joint insertion
· Walter Simson
· Sebastian Requena Witzig
· Anna Rienmüller
· Salvatore Virga
· Oliver Zettinig
· Drazen Sakara
· Yu-Mi Ryang
· Nassir Navab
· Christoph Hennersperger
Received: 27 January 2018 / Accepted: 27 March 2018 / Published online: 18 April 2018
© CARS 2018
Purpose Facet joint insertion is a common treatment of chronic pain in the back and spine. This procedure is often performed
under ﬂuoroscopic guidance, where the staff’s repetitive radiation exposure remains an unsolved problem. Robotic ultrasound
(rUS) has the potential to reduce or even eliminate the use of radiation by using ultrasound with a robotic-guided needle
insertion. This work presents ﬁrst clinical data of rUS-based needle insertions extending previous work of our group.
Methods Our system implements an automatic US acquisition protocol combined with a calibrated needle targeting system.
This approach assists the physician by positioning the needle holder on a trajectory selected in a 3D US volume of the spine.
Results By the time of submission, nine facets were treated with our approach as ﬁrst data from an ongoing clinical study.
The insertion success rate was shown to be comparable to current clinical practice. Furthermore, US imaging offers additional
anatomical context for needle trajectory planning.
Conclusion This work shows ﬁrst clinical data for robotic ultrasound-assisted facet joint insertion as a promising solution
that can easily be incorporated into the clinical workﬂow. Presented results show the clinical value of such a system.
Keywords Robotic ultrasound · Neurosurgery · Needle guidance · Facet joint inﬁltration · Surgical planning
Like any spinal synovial joint degeneration, inﬂamma-
tion can lead to pain while moving, initiating a cycle of
physical degradation, irritation of facet innervations and
muscle spasms. Image-guided insertion of local anesthet-
ics and steroids into or around the facet joint aims to break
this vicious cycle and thereby provide pain relief. Facet
joint injections are the reference treatment when dealing
with facet-related spinal pain caused by joint degeneration,
inﬂammation or injury . Treatment is usually ambula-
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s11548-018-1759-x) contains supplementary
material, which is available to authorized users.
Technical University of Munich, Garching bei München,
Imfusion GmbH, Munich, Germany
Medidee Services SA, Epalinges, Switzerland
Klinikum rechts der Isar, Munich, Germany
Johns Hopkins University, Baltimore, USA
tory and performed under ﬂuoroscopic guidance . X-ray
images are used in order to both ﬁnd the initial needle inser-
tion point and correct the needle trajectory once it has been
inserted. This leads to a high variability in accuracy, duration
and radiation exposure depending on the physician’s level of
experience  and the particular patient’s anatomy. The
physician’s accumulated exposure motivates the search for
alternatives to ﬂuoroscopic guidance.
Ultrasound imaging (US) has been proven to be effective
in facet joint insertion by providing complementary informa-
tion to physical examination . Compared to ﬂuoroscopy,
the reported success rate, analgesic effect and functional
improvement showed no signiﬁcant differences . How-
ever, the coordination between the use of free-hand US and
the simultaneous insertion of the needle creates difﬁcul-
ties. Furthermore, in clinical practice, the ultrasound plane
is commonly acquired orthogonally to the x-ray projection,
requiring the physicians to adjust their perception of the pro-
cedure accordingly. The inherent physics of US combined
with complex bone structures in the spinal anatomy increase
the difﬁculty of free-hand US needle insertions and therefore
require extensive expertise  and special training .
Guidance system has shown to improve the results of the
surgery . In this document, the rUS solution shown in