Navigation in knee replacement surgery

Our orthopaedic unit covers three sites and a population of over 600,000 in the Central Belt of Scotland. I work with another 17 orthopaedic surgeons who provide care covering most musculoskeletal areas, from hand to foot and ankle surgery. I specialise in knee reconstruction surgery, and personally have over 15 years’ experience of navigation in knee replacement surgery. Our unit has been navigating most total knee replacement surgeries for 12 years, with very satisfactory audited results. We have tried various navigation possibilities in unicompartmental knee replacements but, unlike total knee replacement navigation, have not, until now, found a convincing technology to apply to the particular needs of single compartment knee replacements. 

Unicompartmental knee replacements require accurate placement for good function and longevity, especially for the fixed bearing versions. We have, however, struggled as surgeons to perform these in a consistent fashion, especially using less invasive day surgery techniques.

In Spring 2012, we became aware of the commercial introduction of the NavioPFS and identified the advantages of no pre-operative magnetic resonance imaging (MRI) or computed tomography (CT) scanning or planning, as all these stages were integrated seamlessly into the operation itself. 

Looking to improve the quality and accuracy of our surgical implantation in unicompartmental knee replacements, we agreed to trial the system and started its clinical use in late 2012, achieving the first UK application shortly after our colleague in Belgium, Professsor Johan Bellemans, had also started in Summer 2012. In the short-term, the main advantage is simply that of better quality and accuracy of implantation, with an expectation of better long-term survival and improved function.

We will, however, not know this for sure for some years. We are now at the stage that the technique takes a similar amount of time as the other currently used techniques but with the reassurance of intra-operative confirmation of accurate placement and soft tissue balancing. In view of this increased confidence in the system, I expect a gradual reduction in the use of total knee replacements and an associated reduction in bed days because it is feasible to perform the NavioPFS as an overnight procedure.

Increasing the capabilities 

We had been aware of the exciting developments in new robotic techniques, such as Acrobot Sculptor and Mako, but found the capital cost prohibitive for lower volumes of surgeries; furthermore, the planning and pre-operative imaging was an added financial barrier to their use. There is, however, an attraction in using the accuracy of robotics and navigation together to achieve the most accurate and appropriate placement of a partial knee replacement, personalised for each individual patient. Interactive real-time three-dimensional (3D) visualisation available in these emergent technologies allows the surgeon (either pre-operatively with the Sculptor and Mako or intra-operatively with the NavioPFS) to plan and model a best-fit placement for each patient and extrapolate in advance what this planned placement will achieve in terms of tissue balancing and limb alignment, both vital elements in successful replacement surgery. These technologies essentially allow a synthetic visualisation of the planned operation before the actual execution of the operation. The accepted plan is then used by the navigation system to allow the surgeon to use a reaming tool that is safely guided to remove the exact amount of bone to allow the new replacement to be inserted.  

The immediate benefit to both surgeon and patient is increased accuracy of implantation and leg alignment specific for the patient and removal of the least possible amount of bone. There are also fewer surgical instruments required for the procedure, with consequent savings in costs of sterilisation.

The operating theatre set-up is relatively conventional, with the navigation platform and touch screen being within reach of the surgeon across the operating table, with the patient lying supine. No special instruments are required apart from the navigated Anspach Drill and standard navigation trackers.

At present, only 5% of total knee replacements are navigated and, until now, only a small number of partial knee replacements utilise this technology or robotics. Barriers to introduction until now have been the significant capital cost of the equipment, the added costs of pre-operative imaging with either CT or MRI scanning and planning time. This balance is set to change with the NavioPFS, which removes the need for pre-operative imaging and provides a significantly cheaper capital cost platform. These attractions of the Navio system are reflected in the number of surgeons wanting to trial the technology and the first use in the US in February 2013.

A patient with simple medial compartment osteoarthritis previously offered a total knee replacement. He had been unwilling to risk loss of range of movement and a possibly painful knee for kneeling as he enjoyed both gardening and bowling to a high standard. He underwent a NavioPFS unicompartmental knee replacement and was discharged two days post-operatively, At six weeks, he returned satisfied with both retention of his range of movement and also being able to kneel for gardening.

Just as the public have come to expect increased accuracy in many aspects of their lives, for example, punctuality of travel providers, balance and tracking of car tyres and car navigation systems, it is unlikely that they will continue to accept poor standards in surgical implantation, especially when it is known that poorer accuracy equates to poorer outcomes. The need to measure the accuracy of our surgical actions during surgery is an inevitable consequence of societal demands for better and more consistent results. Navigation will fulfill this requirement and will also allow contemporaneous documentation of the outcome. The use of navigation-driven, semi-constrained, robotically controlled tools is also an inevitable corollary to this quest for accuracy and consistency.