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3D navigation platforms and knee osteoarthritis

Frédéric Picard spoke with Hospital Healthcare Europe to discuss his pioneering work in the area of 3D visualisation and navigation platforms in knee osteoarthritis
Frédéric Picard MD
Consultant orthopaedic surgeon
Golden Jubilee National Hospital of Glasgow, UK 
The Golden Jubilee National Hospital is a National Waiting List Initiative Hospital for patients throughout Scotland. Approximately three thousand joints are performed every year, which comprises 40% of joint arthroplasty in the West of Scotland and almost 25% of the whole of Scotland. I perform, on average, between 350 and 400 arthroplasty joints per year: 60% for knees and 40% for hips.
The NavioPFS system 
The first introduction of a NavioPFS system to the clinic was in December 2012.
Implementation took approximately one year after the first introduction of the NavioPFS, mainly because the system was neither CE marked nor US Food and Drug Administration (FDA) marked and we wanted to assess the technology through a complete process. The system was assessed first in the Bioengineering Department at Strathclyde University, where it was first evaluated on sawbones and then on cadavers. This allowed us to confirm its efficiency and accuracy 
but also allowed us to complete our training process. 
Advantages of the system
There is no evidence in the literature currently that would significantly benefit the hospital with the use of the technology. Indeed, this system has been very recently introduced to the surgical environment and there are no available data that could confirm obvious advantages to the hospital. However, cost savings might happen over time because of the accuracy and the precision of the technology, which should then allow a perfect positioning of knee implants and reduce early revision for mal-alignment or knee balancing mismanagement.
According to the National Registry in England, early revision represents almost 10% of the total number of uni-compartmental knees. Therefore, cost savings should be made over years, considering that this machine should reduce the number of revisions. 
Quicker patient turnaround is also a very difficult item to consider because uni-compartmental knees are usually performed using minimally invasive surgery, whether the conventional manual technique or computer-assisted surgery technique are used. Therefore, any enhanced recovery programme combined with the use of minimally invasive surgery certainly plays a larger role in patient turnaround than the technology itself. 
Finally, the predicted advantages of the hospital are the increasing numbers of satisfied patients, which should, according to the premise of this technology, then improve patient functional outcomes and long-term results.
Increasing capabilities
This 3D visualisation and navigation increase the capabilities in knee replacement surgery. Our hospital used computer-assisted navigation in almost 60% of knee replacements. Four of my colleagues, including myself, are using the navigation in almost 100% of the cases, which does allow us to repeatedly align and balance our knee replacements. We, and others, have proven extensively in several publications that navigation improves knee replacement alignments, balancing and reduction of complications.
NavioPFS, the first CT-free handheld robot technology in UKR, is based on concepts that have been extensively validated over the past ten years and have been proven to be very efficient in balancing and aligning total knee replacements and uni-compartmental knees. Navigation is no more than an accurate measuring tool that allows the surgeons to improve their performance and secure and reproduce repeatedly surgical steps and procedures. In fact, the use of this technology is like a computer-assisted balancing car system that the mechanics use to balance and align reproducibly the tyres or wheels of a car to reduce wear and instability.
Benefits to patient and surgeon? 
The benefits for patients, which still need to be assessed and evaluated over the coming years, should guarantee better alignment and better balancing. The system should also allow repeatable alignment and balance using minimally invasive approach. It is an accurate and precise measuring tool to assess knee kinematics, a knee factor in functional outcome. 
The benefits for surgeons are for them to have permanent feedback during surgical procedure. It should also be a fantastic tool for planning optimally the position and placement of the components prior to performing the actual bone milling. Finally, permanent control of burring bone surfaces to optimally fit the implants should help the surgeon to improve patients’ outcomes. In addition to that, all of these intra-operative data are being collected and stored and could then be copied to the patient, as we do today after knee arthroscopy, in handing over intra-articular pictures. 
Concepts of the procedure
The NavioPFS is based on two important technological equipments. The first is the navigation technology and the second is the robotic technology. 
NavioPFS is the first semi-controlled robotic technology using CT-free navigation. This robot is different from active robotics (Robodoc or former Caspar) or semi-active robotics such as Acrobots, Stanmore or Mako robots. Indeed, the data registration is done intra-operatively and there is no need for any medical imaging technology prior to surgery. Other systems require MRI or CT scans prior to the surgical intervention on which planning and implant positioning are done. NavioPFS allows intra-operative data collection to be used to build up a frame of reference on which the planning is done to accurately assess the knee kinematics and place the implants. 
Four phases are available in this machine. The set-up, which is common to many computer-assisted systems on the market, based on optical tracking technology; the registration, which is also very common; the planning, which is probably one of the best features of this system and finally the execution using the hand-held robot, which is unique. 
First, a series of anatomical data collection on the knee and around the ankle and kinematics registration on the hip and the knee define a frame of reference for the femur and a frame of reference for the tibia. (AP, lateral and transverse axes and planes are defined for optimal implant positioning.)
After the registration process, the next step is the planning, which is probably one of the best features of this system. This allows the surgeon to foresee and predict the position of the femoral component and the tibial component and also get a fine tuning and appropriate tailoring of the knee kinematics after surgery. Once the surgeon is happy with the planning phase, the next step is the execution of the planning.
Execution is the next stage, which is the robotic part (precision freehand sculpting PFS™). The robotic tool is a hand-held robot that resembles a shaver that the orthopaedic surgeons use in theatre for ACL reconstruction. The robot is equipped with passive trackers with reflective optical spheres and the tip of the instrument is equipped with a retractable burr, fitting inside a plastic or metallic sleeve. The burr spins out and retracts in or out from the sleeve. The hand-held robot is placed on the distal femur in order to ream out the bone that needs to be removed in the view to fit the femoral implants and the same procedure is required to shape the upper tibia to draw the bed of the tibial implant. 
Once the planning has been properly carried out, the burr removes the bone that has to be taken away to fit the planned sized implants. When the surgeon orientates the burr to the zone where the bone has to be removed, the burr spins out of the sleeve and reams the bone out. If the burr is out of reach or out of the pre-determined plan, then the burr comes back in the sleeve and does not then ream the bone.
This controlled robotic tool can only burr the pre-planned surface and nothing else. Therefore, using several graphical interfaces, the surgeons gradually remove the distal bone of the femur and the proximal bone of the tibia to finally level and smooth the bone to receive the implants. Once the work has been completed, a series of trial implants fit on the distal femur and the proximal tibia and the trial phase can be performed. The surgeon can assess the alignment and balancing of the legs as well as the knee kinematics. 
Is the technology widely adopted? 
If the question is related to computer-assisted technology, it is still not mainstream. However, we are definitely reaching, in most countries, between 5 and 10% of users in knee surgery. In certain countries, such as Germany, more than 30% of surgeons are using this technology on a routine basis, for knee replacements, mainly. 
If the question is related to NavioPFS, obviously its recent introduction to the market prevents this system from being widely used. However, this machine has now received a CE mark and FDA approval, which should increase its use all over the world. 
What are the potential barriers for implementation? 
The two main obstacles are cost and training.
Cost is obviously a factor. The systems will be commercialised within perhaps a price range of £100–-300K, depending on geography, but are definitely cheaper than the active robotic technology instrumentations, where prices exceed US$1million. 
The training requirements are obviously extremely important, but it is not a new concept, and most of the companies using computer navigations have access to a training programme which does allow any surgeons interested in this technology to have proper training and reduce their learning curve. For surgeons who are not used to this technology, it takes usually between ten and 20 cases to be familiar with it and then reach the threshold of the learning curve. 
Finally, the new young trainees are extremely familiar with computer technology and video games, who play regularly with sophisticated user interfaces and who will not have any problem adapting to the technology! 
A case study
A young patient with a medial osteoarthritic knee presented with constant pain when walking, who struggled with both his work and daily activities and was disturbed at night. He had a complete narrowing gap on the medial compartment with complete disappearance of the cartilage on the medial side of his knee with 10° varus knee. Fortunately, the rest of the joint was sub-normal with normal cruciate ligaments and normal lateral compartment and patellofemoral joint. This gentleman had a NavioPFS implanted. Six-week review with our Arthroplasty Service confirmed excellent clinical and radiological outcomes.
Future developments
We can already see changes in our surgical suite. For example, our surgical theatres are already equipped with a lot of computers, used by nurses, by anaesthetists and even by us, for knee or hip navigation. Optical localisers and monitor screens are already on site, integrated in our surgical theatres, and are used in a daily basis by all of us. In the future, we will definitely have more and more integrated instruments available to routine practice, such as sophisticated intelligent robotic tools. These devices will become part of the toolbox that any orthopaedic surgeon could use at any time, as we do today with power tool, screwdriver and conventional instruments.