By Dr. Sachin M, Junior resident, Dept of Orthopaedics, SMCH, Silchar

1. ROBOTICS AND
NAVIGATION IN
ORTHOPAEDICS
Presented by : Dr. Sachin M
PGT, Dept of Orthopaedics, SMCH.
Moderator: Dr. A. K. Sipani
Professor and HOD, Dept of Orthopaedics, SMCH.

2. HISTORY
• Mid 1980s for neurosurgery.
• ROBODOC (1992) – first robotic technology in Orthopaedic
surgery used for the planning and performance of THR.
• Dr. Howard Paul and Dr. William Bargar.
• “Robot” derived from the Polish word robota – forced labour.
• It’s a machine that carries out a variety of tasks automatically
or with a minimum of external impulse, especially one that is
programmable.

3. ROBOTIC SURGERY SYSTEMS
• Types of Robotic surgery systems:
• Haptic or tactile
• Autonomous
• Passive Surgery systems
• Haptic systems - allow the surgeon to use or drive the robot to
perform the operation.
• Requires constant input from the surgeon.
• Autonomous systems – require surgeon to perform the
approach and set up the machine.
• Once engaged, the robot completes the surgery without the
surgeon’s help.

4. Robotic Systems

5. Robotic Surgery -Advantages
• Ability to perform MIS.
• Improved accuracy of implant placement.
• Improved radiological alignment of extremities.
• Short hospital stay, less blood loss, greater accuracy.

6. Robotic Surgery - Pitfalls
• The setup required is expensive.
• Constant software upgradations and calibrations will add to the
cost.
• Long term outcome studies are necessary to demonstrate
superiority and cost efficiency of Robotic surgery in routine
practice.
• Unable to manage soft tissue dissection by itself for
orthopaedic practice.
• The ROBODOC fell into disrepute because it was associated
with increased risk of infection, blood loss, neurological
damage and perhaps an increased rate of litigation.

7. CAOS
• Computer assisted orthopaedic surgery is defined as the use of
computers and robotic technology to assist the orthopaedician
in providing musculoskeletal care.
• Includes:
• Pre-operative planners
• Intraoperative navigation equipment
• Smart tools
• Remote surgery technologies
• Fundamental characteristics:
• Geometric precision
• Reproducibility
• Perfect memory
• Lack of fatigue.

8. NAVIGATION
• Tracking: Determines in real time the location of moving
objects in space.
• Registration: Establishes a common reference frame between
the moving objects and the images.
• Visualization: Creates navigation images showing the location
of moving objects with respect to the anatomy.
• Validation: It ensures that the updated images match the
clinical intra-operative situation.

9. COMPONENTS OF NAVIGATION UNIT
• Computer unit
• Tracking unit
• Tracker mounting hardware

10. Mode of Operation
• The tracking base unit receives and integrates the signals from
the position sensor and the trackers.
• The computer integrates these signals with images and
instrument models (registration), and creates one or more
views for display (visualization).
• The navigated images are updated in real time by the computer
as the instruments and anatomy move.
• The tool calibration unit is used to obtain geometric data of
surgical tools fitted with trackers, such as tool tip’s offset.
• These geometric data are used to create the instrument model
for display.

11. TRACKING
• Position sensor and trackers.
• Position sensor – determines the spatial location of the
trackers at any given point of time.
• By attaching trackers to surgical tools and bone structures,
their relative spatial position can be continuously be followed
and updated in the computer display.
• Trackers are rigidly mounted on tools and bones with tracker
mounting jigs, which are mechanical jigs similar to screws and
clamps.
• When fluoroscopic radiography images are used for
navigation, the computer unit is also connected to a C-arm and
imports images acquired with it.

12. TRACKING
• The C-arm is usually fitted with its own tracker to determine
its relative location with respect to the tracked objects and
imaged anatomy.
• Two types of tracking technologies are available:
• Optical tracking – most commonly used
• Magnetic tracking

13. OPTICALTRACKING
• Position sensor consists of two or more optical cameras that
detect the light emitted or reflected by markers.
• Triangulation:
• Each camera measures distance of the markers from the camera.
• Because the base distance between the optical cameras is known,
the position of the marker with respect to the camera’s base line
can be computed by a method known as TRIANGULATION.
• A tracker consists of three or more markers mounted on a
rigid base.
• A key requirement is the maintenance of an unobstructed line
of sight between the position sensor and the trackers.
• Optical tracking systems can be active, passive or hybrid.

14. OPTICALTRACKING
• Active tracking: uses active markers, which are light emitting
diodes (LEDs) that are strobbed in tandem by the base unit.
• Passive tracking: Uses passive markers, which can be
reflective spheres or printed patterns. These passive markers
are not controlled by the tracking base unit and are seen
simultaneously by the cameras.
• Hybrid tracking: incorporates both active and passive
tracking, thus providing the advantages of both technologies.

15. MAGNETIC TRACKING
• Works by measuring variations of generated magnetic fields.
• Position sensor consists of a magnet that generates a uniform
magnetic field and a sensor that measures its phase and
intensity variations.
• Trackers consist of one or more miniature coils mounted on a
rigid base that generate a local magnetic field from an
electric current, either AC or DC.
• The location of the tracker is computed from the relative
variations of the sensor’s intensity and its phase magnetic field.
• A key requirement is the maintenance of a uniform magnetic
field, which is altered by the vicinity of magnetic fields from
other electronic devices and the nearby ferromagnetic objects.

16. TECHNICALISSUES OF TRACKING
• Tracking systems measure the position of markers in a
predefined volume in space, called the tracking work volume.
• Simple in shape, like sphere, pyramid or cube.
• The distance between the position sensor and the tracking
work volume is fixed.
• Factors influencing tracking accuracy are:
• Position sensor accuracy
• Marker accuracy
• Tracker accuracy
• Tracker system accuracy
• Accuracy is usually highest at the center, with decay toward
the boundaries of the tracking work volume.
• Hence, the position sensor should always be placed as close as
possible to the center of the expected work volume.

17. REGISTRATION
• It is the process of establishing a common reference frame
between objects and images.
• It is a pre-requisite for creating a reliable image of the
intraoperative situation, accurately showing the relative
locations of the anatomy and the surgical tools of interest with
respect to the preoperative and/or intraoperative images.
• It is achieved by transformations between the objects’
coordinate frames at all times.
• A coordinate frame serves as a reference within which the
spatial locations of objects can be described.
• Each object of interest has its own coordinate frame.
• By describing the location of B’s coordinate frame with respect
to A, the relative location of the objects can be described.

18. REGISTRATION
• The transformation is static when the relative locations of A
and B do not change or dynamic when one or both of the
objects move.
• The relative locations of objects are obtained by chaining
transformations – location of C with respect to A is obtained
from the location of B with respect to A and the location of C
with respect to B.
• The registration involves four types of transformations
• Tracker transformations
• Tool transformations
• Image transformations
• Display transformations

19. REGISTRATION
• Registration accuracy – depends on the accuracy of each
transformation and the cumulative effect of transformation
chaining.
• Tracking transformation – accuracy of the tracking system
and on the location of the tracker with respect to the center of
the position senor working volume.
• Tool transformation – accuracy of tool calibration and on the
relative location of the tracker with respect to the tool tip.
• Image transformation – accuracy of the imaging modality
used and the tracking system’s accuracy.
• Display transformation – accuracy is very high as it only
involves numerical computations.

20. VISUALIZATION
• It creates updated images that show the location of moving
objects with respect to the anatomy.
• The navigation images are created by merging the preoperative
and intraoperative images with the tools and bone location
information.
• The type of navigation images created depends on the
preoperative and intraoperative images that are used, on the
surgical tools and on the surgical procedure.
• Fluoroscopic-based navigation systems – consists of images
from C-arm (AP, lateral and oblique) with the surgical tool
silhouette at its present location superimposed on them.
• CT based navigation systems – consists of sagittal, coronal
and transverse CT cross sections, and a spatial view with the
preoperative plan, with the surgical tool’s silhouette at its
current location superimposed on them.

21. VISUALIZATION
• It provides the surgeon with
• Various image processing
• Viewpoint selection
• Information display features such as contrast enhancement,
viewpoint rotation and translation.
• Window selection
• Tool silhouette thickness
• Color control

22. VALIDATION
• It is the task of verifying that the images and data used for
intraoperative navigation closely correspond to the clinical
situation.
• It is an integral part of the navigation surgical protocol.
• It is performed both before the surgery starts and at key points
during the surgery.
• Without validation, the data can mislead the surgeon and yield
unwanted results.
• There are 3 main types of verification:
• Tool calibration verification
• Dynamic reference frame verification
• Registration accuracy verification

23. VALIDATION
• The validation procedure depends on the type of surgery, the
navigated surgical tools, and the images used.
• Tool calibration verification: verifying with a calibration jig
that the tool tip is at its computed location.
• Dynamic reference frame and registration accuracy
verification: verifying that the tracked bones and tools are
indeed where the navigated images indicate.
• Registration accuracy is quantified by measuring the drift
between the actual and the computed location of tools and
anatomic landmarks.
• When registration accuracy is inadequate, the surgeon must
repeat the registration process.

24. NAVIGATION SYSTEMS
• There are two types of navigation systems for CAOS
• Fluoroscopy based systems
• CT-based systems
• Fluoroscopy based systems.
• They create navigation images by superimposing the surgical
tool silhouette onto conventional fluoroscopy images and
updating its location in real time, thereby creating the
impression of continuous fluoroscopy without the ensuing
radiation.
• The resulting effect is called Virtual fluoroscopy.
• Two types of Fluoroscopy-based navigation based systems:
• Conventional C-arm fluoroscopy
• Three dimensional fluoroscopy.

25. NAVIGATION SYSTEMS
• 3D fluoroscopy
• New imaging modality that allows for the acquisition of CT-
like images during surgery by taking about 100 fluoroscopic
radiography images at one degree intervals with a
motorized isocentric C-arm.
• Can also be used as Conventional C-arm.
• Advantages:
• The radiation dose is about half of the dose of a regular CT
• Accurately reflects the actual intraoperative situation
• Disadvantages:
• Quality of images are not as high as those obtained with a
preoperative CT
• Can only be used to image limbs

26. NAVIGATION SYSTEMS
• CT – based systems
• They create navigation images by superimposing the surgical
tool silhouette onto preoperative CT cross-sectional and spatial
images and updating its location in real time.
• Only feasible when a CT data set is available.
• A key step in the protocol is the CT registration procedure.
• The relationship between the CT and the intraoperative
situation is established by matching a set of points on the
surface of the bone region to the corresponding points on the
CT surface model.

27. NAVIGATION SYSTEMS
• CT – based systems
• Advantages over conventional fluoroscopy are:
• They provide axial and spatial, real time multi-image visualization
of bony anatomy and surgical tools.
• They significantly reduce the use of fluoroscopy in the operating
room.

28. Advantages of CAOS
• Facilitates minimal invasive surgery (MIS) by reducing the
soft tissue damage, thus shortening the postoperative
rehabilitation process.
• Improves the accuracy of fracture reduction and implant
placement compared with that obtained with conventional
methods and reduces outcome variability.
• Significantly reduces radiation exposure to both the patient
and the surgeon.
• Creates a powerful educational and quality control tool.

29. Applications of Computers and
Navigation in Orthopaedics
• Trajectory navigation – drill guide applications (hip and pelvic
fractures, tumor biopsies, pedicle screw placements, drill and
entry point placements in trauma surgeries).
• Fracture reduction and assessment.
• Intra-articular fracture fixation.
• Localization of bone lesions or removal of surgical hardware
and shrapnel.
• Navigation arthroplasty of Hip and Knee.
• Spinal stabilization.
• Individualizing tunnel placement in ligament surgery.
• Open wedge osteotomy.
• Ligament reconstruction and balancing and tensioning of the
ligaments during the procedure.

30. Applications of Computers and
Navigation in Orthopaedics
• Surgical technical skills training.
• Bone morphing – in implant designing and sizing templates for
new implants taking average anthropometric cadaveric data.
• Designing patient specific implants.
• CAM (Computer Assisted Manufacturing) and CAD
(Computer Assisted Designing) of implants, prosthesis and
megaprosthesis.

31. COMPLICATIONS
• Loss of line of sight
• Occurs when the view between the optical camera and the
trackers is obstructed by the surgeon or another member of the
surgical team, the patient’s body, the C-arm, the overhead
lamps, or any other object in the vicinity of the surgical filed.
• Can be remedied by moving the object causing the
interference, by repositioning the optical camera, or by
changing the surgical team’s location around the patient.

32. COMPLICATIONS
• Shift of the dynamic reference frame rigid bone mounting
• Rigid attachment of the bone tracker to the bone throughout
surgery is essential for registration accuracy.
• Shifting is usually due to bone fixation loosening, poor jig
fixation, or unintentionally pushing or hitting the tracker and
its mounting jig.
• Surgeon must make sure that the tracker mounting jig is
securely fixated to the bone structure.
• The only way to detect dynamic reference frame motion is by
validation, which should be performed at key points during
surgery and always when in doubt.

33. COMPLICATIONS
• Tool decalibration
• Occurs when the geometric data of the tracked tool does not
match its actual geometry.
• Caused by tool wear and tear.
• Surgeon must verify tool calibration before surgery, at key
points during the surgery, and always when in doubt.
• Custom calibration software and hardware.

34. COMPLICATIONS
• Navigation image inaccuracy
• It is the mismatch between the displayed images and the
intraoperative situation.
• Result of errors in the registration chains.
• Main causes: shift of dynamic reference frame, tool
decalibration, the shift of the C-arm tracker ring.
• Secondary causes: tracking system drift over time, navigation
at the edge of the position sensor working volume.
• Other causes are related to images themselves.
• Optimization of these navigation images is crucial and should
be done during the image acquisition stage, before surgery
begins.

35. COMPLICATIONS
• System robustness issues
• Robustness is the ability of a system to perform its intended
tasks with a minimum number of failures over time.
• Depends on both software and hardware.
• Software failures: flaws in the computer operating system, in
the custom-designed software, and in the tracking base unit
controller.
• Hardware failures: failure of the computer unit, poor cable
connections, and failure of the tracking unit.

36. COMPLICATIONS
• Verification of surgical tool and implant spatial position.
• Adaptation to different surgical techniques.

37. Limitations of CAOS
• Support for implants and instrumentation
• The choice of supported implants and instruments depend on the
decisions made by the navigation and instrument companies,
which are primarily dictated by commercial interests.
• Support for surgical procedures
• Navigation systems require software modules (software surgical
protocols) that implement the surgical protocol for navigation for
specific procedures.
• Improvements in tracking technology
• Current tracking technology has several drawbacks like line of
sight, size of trackers, cables, number of trackers, accuracy and
cost.

38. Limitations of CAOS
• Image-based CT registration
• CT-based navigation systems require the surgeon to acquire points
on the surface of the anatomy of interest to perform the
registration between the CT data set and the intra-operative
situation.
• This precludes its use in percutaneous procedures as it is time
consuming and error prone and produces suboptimal registration
results.
• Planning
• Current intra-operative planning is either nonexistent or limited at
its best.
• The blurring of the distinction between preoperative and
intraoperative planning opens the door for better planning and
consequently better and consistent results.

39. Limitations of CAOS
• Spatial visualization without CT
• A drawback of fluoroscopy-based navigation systems is that they
do not show spatial views of the intraoperative situation, which
can only be produced when CT data are available.
• Ergonometric factors
• Most operating rooms were not designed with new technology in
mind in terms of size; placement of the computer, computer
screen, and cables etc.
• The machine occupies space.
• Its positioning is dictated by the line of sight between the tracker
sensor and the markers.

40. Telesurgery
• By using robotics and/or computer-assisted devices,
experienced surgeon can supervise, assist or perform surgical
procedures at remote locations.
• In 2001, New York surgeons performed Cholecystectomy on
68 year old lady by remotely manipulating robotic tools.
• Other surgical procedures like Hernia repair and bowel
resection and also in other specialities like Urology and
Neurosurgery.
• In Orthopaedics, Telesurgery is not yet well developed.