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gap balancing and providing reasonably accurate alignments of limb and components alike.However, such routine navigation technique fails to use the full potential of the registeredinformation. Current technique provides reasonable static stability information in the coronalplane, but with axial and sagittal planes less well considered. A more dynamic approach seemsto be necessary to define ‘potential envelopes of motion’, seeming to be the best possible wayin which CASN will finally show fundamental improvements over ‘conventional’ technique.Enhanced dynamic assessment using an upgraded CASN system (Brainlab) is now capable ofimproved ROM analysis and contact point observations. This consists of storing dynamicinformation including a) epicondylar axis motion, b) valgus and varus alignments, c) anteroposteriorshifts, as well as d) flexion and extension gaps. Tracking values for both tibiofemoraland patellofemoral motion can also be obtained after performing registration of the prosthetictrochlea.Observations can be made using a set of standardised dynamic tests. Firstly, the lower legcan be placed in neutral alignment and the knee put through a flexion-extension cycle.Secondly the test can be repeated but with the lower leg being placed into varus and internalrotation. The third test can be performed with the lower leg in valgus and external rotation.Also a new passive technique of ‘Drop and Push Testing’ into a) flexion and b) extension isgiving new information which may prove useful a) in terms of over-stuffing of the extensormechanism and tightness of flexion gap and b) provision of hyperextension to assist gait.Upgraded software prompts can improve workflows to facilitate optimisation of joint dynamics.Twenty total knee arthroplasties have been studied using these techniques with particularreference to the patterns of instability found. Marked intra-operative variation in the stabilitycharacteristics of the trial implanted joints has been quantified before corrections have beenmade and final assessments performed. These corrections have also been analysed in terms ofchange in antero-posterior translations, rotations and contact points. Edge loading andexcessive paradoxical motions have been identified and corrective measures carried out, therebyimproving PCL tensioning. Component rotations, tibial slope angles, insert thicknesses andfemoral sizing have had to be adjusted to optimise range of motion and stability characteristics.Certain cases have been identified where use of more congruent or even stabilised componentswas considered necessary. Patellar tracking has also been observed during such dynamic testsand appropriate adjustments made to components and soft tissue balancing.In summary, this study has enabled intra-operative observation, classification andquantification of patterns of instability in 6 degrees of freedom using simple stress testsfollowed by appropriate adjustments.Thursday, October 7, 2010, 10:20-10:50Session B3: Cartilage Repair/RegenerationMethods to Determine Indications for Partial Resurfacing in the KneeIncluding Arthroscopic Cartilage Mapping and Radiographic Analysis*Robin Strachan - Imperial College NHS Trust - Fulham Palace Road, London, Unitedfile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]