Model-Based State Recognition of Bone Drilling with Robotic
Orthopedic Surgery System
Haiyang Jin, Ying Hu*, Zhen Deng, Peng Zhang, Zhangjun Song and Jianwei Zhang
Abstract— Screw path drilling is an important process a-
mong many orthopedic surgeries. To guarantee the safety
and correctness of this process, a model-based drilling state
recognition method is proposed in this paper. The thrust force
in the drilling process is modeled based on an accurate 3D
bone model restructured by means of Micro-CT images. In
theoretical modeling of the thrust force, the resistance and the
elasticity of the bone tissues are considered. The cutting energy
and elastic modulus are defined as the material parameters in
the theoretical model, which are identified via a least square
method. Some key parameters are proposed to support the
state recognition: the peak forces in the first and the second
cortical layers, the average force in the cancellous layer and the
thickness of each layer. Based on these key parameters in the
model, a state recognition strategy with a robotic orthopedic
surgery system is proposed to recognize the switch position
of each layer. Experiments are performed to demonstrate the
effectiveness of the modeling approach and the state recognition
method.
Keywords— orthopedic surgery; Micro-CT; bone drilling;
state recognition
I. INTRODUCTION
In many orthopedic surgeries, bone drilling is one of the
most important procedures for inserting bone screws [1].
As many important vessels and nerves surround the bones,
incorrect screw path drilling may cause patients irreparable
damage. Using a robotic surgery system to perform this
drilling process can help surgeons to improve their accuracy
and lower the risk.
The requirements of bone drilling are different in different
surgeries. For example, in operations with interlocking in-
tramedullary nailing, the screw path crosses the entire bone
layers [2]; while in transpedicular fixation operations, the
screw path stops at the second cortical layer of the vertebral
bone [3]. Therefore, to recognize the drilling state in the bone
drilling process, real-time thrust force feedback is being used
in robotic systems by many scholars.
*This research supported by the National Natural Science Foundation
of China (No.61175124 and No.51005227), Key Research Program of the
Chinese Academy of Sciences (No.KJZD-EW-TZ-L03) and Guangdong
Innovative Research Team Program (No. 201001D0104648280).
Haiyang Jin is with Harbin Institutes of Technology Shenzhen Grad-
uate School. Guangdong Provincial Key Laboratory of Robotics and
Intelligent System, Shenzhen Institutes of Advanced Technology, Chi-
nese Academy of Sciences. The Chinese University of Hong Kong
(hy.jin@siat.ac.cn)
Ying Hu*(corresponding author), Zhen Deng, Peng Zhang and Zhangjun
Song are with Guangdong Provincial Key Laboratory of Robotic-
s and Intelligent System, Shenzhen Institutes of Advanced Technolo-
gy, Chinese Academy of Sciences. The Chinese University of Hong
Kong (ying.hu@siat.ac.cn, zhen.deng@siat.ac.cn,
zhangpeng@siat.ac.cn and zj.song@siat.ac.cn)
Jianwei Zhang is with University of Hamburg, Germany
(zhang@infomatik.uni-hamburg.de)
Most existing studies in drilling state recognition focus
on a general model of the drilling thrust force, which is
obtained via an analysis of a large number of experiments.
Examples of this are the bone drilling systems developed
by Bouazza-Marouf and Ong from Loughborough University
(UK)[4], Louredo et al. from the University of Navarra
(Spain) [5], Lee et al. from Lunghwa University of Science
and Technology (Taiwan) [6], etc. However, these kinds of
drilling state recognition are not aimed at each single screw
path. In current clinical manual operation, surgeons will
estimate the depth of the planned screw path. This estimation
provides a previous prediction for drilling processes. Based
on this idea, Wang et al. from Beihang University (China)
developed a 3D navigation and monitoring system for spinal
milling operation based on the registration between multi-
planar uoroscopy and CT images [7]. We have proposed an
image-force fusion method for state recognition in previous
research [8]. However, the model in the approach is based on
normal CT or MR images, which can only provide the shape
of the bone without the inner microstructure of the bone.
That causes the low recognition rate between the cortical
and cancellous layers in the bone. An accurate 3D model of
the bone can help to improve the drilling state recognition.
For modeling the relationship between the 3D model of the
bone and operation force feedback of the drilling process, a
number of approaches for bone modeling have been present-
ed [9-11]. Agus et al. [9] propose a patient-specific volumet-
ric object model to represent the bone, and the thrust force
is presented based on the Hertz contact theory. Petersik et al.
[10] represent a bone model by volumetric pixels (voxels),
and the spherical drill bit is illustrated by an array of sample
points that cover its surface. A multi-point collision detection
approach is introduced in their research. Mohammadreza et
al. [11] present a voxel representation of the virtual bone,
and the drill bits are modeled as a set of small chips with an
estimated thickness and known material stiffness. The total
force is calculated by integrating all forces over all thrust
chips. These volume-based or voxel-based methods are all
built on graphic simplification of the real structure of bones,
and they can hardly show the complex microscopic bone
structures. However, the mechanical characteristics of the
bone are significantly influenced by the inner microstructure.
Considering the above challenges, in this paper, a new
method for modeling thrust force of bone drilling is proposed
based on an accurate 3D point cloud model. The 3D point
cloud model is gained by Micro-CT scanning so that the
inner microstructure of the bone remains. For modeling
the theoretical thrust force, resistance and elasticity issues
2014 IEEE International Conference on Robotics & Automation (ICRA)
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