The Effect of TKR on Laxity in the Knee


Project Name

The Effect of Total Knee Replacement on the Envelope of Laxity of the Knee


2010 - 2011

Project Collaborators

Prof D.Deehan
Dr. M Ghosh
Mr L. Longstaff



Project Description


From October 2010 to July 2011 work was carried out in the NSTC with a view to examining the mathematical behaviour of the native and replaced knee under a variety of controlled laxity states. The work was supported by a one off educational grant of 25K to allow for purchase of cadaveric material, surgical equipment and design and construction of a test frame to achieve accurate physiological loading of the knee through a range of full movement. The experiments were performed over a series of 12 Tuesday afternoons and late evenings with all workers giving of their time for free. The in house Freeman computer navigation system was used to record and quantify the displacement of the femur and tibia in 3d space with all knee replacement surgical kits provided by StrykerUK. The maximal displacement under loading of the tibiofemoral articulation through a range of movement in 4 axes of laxity was determined for defined conditions ( e.g. resection of the anterior cruciate ligament). The ability of a primary conforming knee without restraint to reverse such a laxity pattern was examined. All data was entered and allowed for a mathematical model of knee behaviour and using R a 3-d predictive model of knee behaviour was obtained. This is presented in the ppt presentation. This has allowed us to begin to predict knee behaviour in response to standard knee component implantation during replacement surgery. In order for a complete dataset to be obtained and to ensure validation of the predictive model, it would be necessary to expand this work to allow for study of differing patterns of laxity, types of knee component (cruciate substituting, semiconstrained, e.g. TS or TC3) and component positioning.