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Orthopaedic Surgery Navigation
Incorporation of Tracking Technology, Navigation and Computer-assisted
Solutions in Orthopaedic Surgery
a report by
Thomas Mattes, R Decking, T Kocak and H Reichel
Department of Orthopaedics, University of Ulm
Continuous progress has made computer-assisted solutions (CAS) more passive reflector arrays, like the NavitrakER devices (ORTHOsoft,
and more common in orthopaedic surgery in recent years. Several Montreal, Canada) compensate for the disadvantages of the common
hundred navigation systems are in routine use in operation theatres, with reflectors with a special geometry and fluid insensible reflecting surface.
a focus on total knee replacement and spinal instrumentation. Both tracking technologies have been validated and have shown
Sophisticated applications are also available for total hip replacement, improved accuracy in axis alignment in total knee replacement and
total hip resurfacing and correction osteotomies. The main goal of pedicle instrumentation in spinal surgery.
1–3
navigated surgery is a higher precision of implant positioning and
reduction of surgical complications. New tracking technologies, Progress in software technology and detecting of disturbances recently
dedicated instruments and ergonomic software make navigation easy to presented by Zimmer (Zimmer, Warsaw, US) and Medtronic (Medtronic
use and precise in results. Also, for traditional approaches as in minimal Navigation, Louisville, US) are setting new standards in EM tracking.
invasive surgery, navigation can help surgeons, patients and healthcare Particularly in minimal invasive surgical approaches, the overlap of large
systems in improved visualisation of instruments and implants related to optical arrays around small incisions could make navigation difficult or
patients’ anatomy. A reduction of aseptic loosening, better functional impossible. The same problem is known for tracking small bones like the
results and reduction of complications are expected. In the long term, vertebrae of the cervical spine.
cost reduction is possible.
Small emitter coils in EM tracking enable placement of dynamic reference
Tracking Technologies – Is Optical Tracking Sufficient or frames via small incisions under soft tissue or direct into small bones
Renaissance of Electromagnetic Technology? without any overlapping problems and sight. Nevertheless, electrical or
The perception of surgical tools and anatomic objects follows the ferromagnetic arrays can interrupt EM tracking systems, and special
principle of dynamic referencing (tracking). Although about 10 years operating room set-ups are necessary for EM navigation. Dependent on
ago one of the first studies
1
with the Navitrack system (ORTHOsoft, surgical technique, used implants and given operating room settings for
Montreal, Canada) could prove the benefit of navigation with most indications and intervention optical tracking would be first choice;
electromagnetic (EM) tracking, disturbance of ferromagnetic in special indications second-generation EM tracking could be an
instruments and operating room equipment impeded wide alternative solution.
implementation of this technology, especially in joint replacement.
Optical tracking systems with passive or active tracing arrays became Navigation – What is Proven?
standard in navigated joint replacement. The main advantage of active Spinal Navigation
arrays is ruggedness without disturbance by soiling. The active tracker The longest navigation experience exists in spinal navigation. In pedicle
systems can also be used as remote control for the system. The instrumentation of the lumbar and thoracic spine, numerous studies
disadvantage of the system is the necessity of a single-use battery for have proven the benefit of navigation. A pre-operative CT scan with
each tracker. intra-operative matching to the patient´s anatomy by intra-operative
fluoroscopy or intra-operative 3-D imaging is the basis for spinal
Most navigation systems work at the current time with passive optical navigation. In a study for pedicle instrumentation for the Dynesys
®
tracking. An infrared-emitting camera and reflector balls on instrument Dynamic Stabilization System (Zimmer, Warsaw, US), the manual
and patient side detect the 3-D position of the objects. These systems technique was compared with CT-based and fluoroscopic-based
are easy to use; reflector balls are reusable and can be changed one by navigation. As in other studies for spinal instrumentation, screw position
one. The downside of the reflector balls is their sensitivity to was more exact in the navigated groups, with a slight edge for the CT-
contamination with fluids. Visibility can be reduced during surgery and based technique. In cervical spine instrumentation navigation similar
time-consuming cleaning sometimes extends surgery time. Newer results were obtained with high precise instrumentation of the upper
cervical spine with the VectorVision
®
spine system (BrainLAB,
Feldkirchen, Germany).
Thomas Mattes is an Orthopaedic and Trauma Surgeon and
Deputy Head of the Department of Orthopaedics at the
University of Ulm, Germany. He has been involved in Total Knee Replacement
computer navigation development and clinical testing,
Most experiences and thousands of navigated surgeries have been
focused on total joint replacement and spinal
instrumentation, since 1998.
undertaken in total knee replacement. Prospective randomised studies
could show that axis alignment is more precise and outliers could be
E:
thomas.mattes@medizin.uni-ulm.de
avoided compared with manual alignment techniques.
4–6
Patient
44 © TOUCH BRIEFINGS 2007
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