Real-Time Prediction of Temperature Elevation During Robotic Bone
Drilling Using the Torque Signal
Institute for Surgical Technology and Biomechanics, Stauffacherstr. 78, 3014 Bern, Switzerland;
ARTORG Center for
Biomedical Engineering Research, Murtenstr. 50, 3010 Bern, Switzerland; and
University of Bern, Bern, Switzerland
(Received 25 November 2016; accepted 26 April 2017; published online 5 May 2017)
Associate Editor Mona Kamal Marei oversaw the review of this article.
Abstract—Bone drilling is a surgical procedure commonly
required in many surgical ﬁelds, particularly orthopedics,
dentistry and head and neck surgeries. While the long-term
effects of thermal bone necrosis are unknown, the thermal
damage to nerves in spinal or otolaryngological surgeries
might lead to partial paralysis. Previous models to predict the
temperature elevation have been suggested, but were not
validated or have the disadvantages of computation time and
complexity which does not allow real time predictions.
Within this study, an analytical temperature prediction
model is proposed which uses the torque signal of the
drilling process to model the heat production of the drill bit.
A simple Green’s disk source function is used to solve the
three dimensional heat equation along the drilling axis.
Additionally, an extensive experimental study was carried
out to validate the model. A custom CNC-setup with a load
cell and a thermal camera was used to measure the axial
drilling torque and force as well as temperature elevations.
Bones with different sets of bone volume fraction were drilled
with two drill bits (;1.8 mm and ;2.5 mm) and repeated eight
times. The model was calibrated with 5 of 40 measurements
and successfully validated with the rest of the data
¼ 0:9034; SEE ¼ 7:582
C). It was also found that the
temperature elevation can be predicted using only the torque
signal of the drilling process. In the future, the model could
be used to monitor and control the drilling process of
surgeries close to vulnerable structures.
Keywords—Bone drilling, Temperature prediction model,
Drilling model, Force–torque model, Temperature elevation
during bone drilling, Bone necrosis, Thermal tissue damage.
Bone drilling is a frequently utilized surgical task in
a number of medical domains including orthopedic
surgery, dentistry, neurosurgery and head and neck
surgery. Due to the risk posed to surrounding tissue
due to thermal damage, a recent scientiﬁc eﬀort to
optimize and model the drilling process has been
undertaken. Unlike metal, human bone has a low
which conﬁnes and accumulates
drilling heat within a small region around the drilled
hole. It is not known if bone damage causes long term
complications in orthopedic surgeries (e.g., screw
loosening), it was found that it affects the osseointe-
gration of dental implants.
It is even more prob-
lematic if the bone drilling occurs in close proximity to
more vulnerable structures such as nerves. This is be-
cause the thermal damage of a bone cutting process
can lead to permanent nerve damage.
A newly described approach to the inner ear for
cochlear implantation, in which a direct tunnel is
drilled using stereotactic guidance through the close
lying nerves of the facial recess (facial nerve and
chorda tympani), is a procedure in which a drill bit
may possibly be required to pass within 0.5 mm from
Recent studies have shown, that drilling
this access might lead to thermal damage of the facial
nerve and thus partial or complete unilateral paralysis
or paresis of the facial muscles.
have been made to reduce this risk by optimizing drill
bit design and drilling process parameters.
In general, there has been a great eﬀort in investi-
gating bone drilling as reviewed and summarized by
The previous work suggests a
low rotational speed (ca. 1000 RPM) and a high feed
rate (ca. 1 mm/s) with sufﬁcient irrigation helps to
Address correspondence to Arne Feldmann, Institute for Sur-
gical Technology and Biomechanics, Stauffacherstr. 78, 3014 Bern,
Switzerland. Electronic mail: email@example.com
Annals of Biomedical Engineering, Vol. 45, No. 9, September 2017 (
2017) pp. 2088–2097
2017 Biomedical Engineering Society