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Thursday, October 7, 2010, 10:20-11:00Session A3: Bearing Mobility IssuesAn Independent Analysis of the First Sixteen Mobile Bearing LateralUnicompartmental Knee Replacements. Is There a Learning Curve?Introduction.*Sebastiaan Schelfaut - AZ St-Lucas Hospital - Brugge, Belgium*Email: sebastiaanschelfaut@msn.comDespite the theoretical advantages of mobile bearings for lateral unicompartmental kneereplacement (UKR), the failure rate in the initial published series of the lateral Oxford UKR’swas unacceptably high. The main cause of failure was early dislocation. In contrast, dislocationsof bearings in medial UKR’s are rare. The lateral compartment present a higher laxity in flexionthan the medial. An adaptation of the lateral design by introducing a convex tibial componentand biconcave bearing should tackle this difference in kinematics.The risk of dislocation increased substantially if the lateral tibial joint line was elevated,quantified by the proximal tibial varus angle. This angle had a significant relationship todislocation.A recent kinematic study identified roughly 3 times as much posterior translation of the tibiaduring deep knee bend activities after lateral UKR compared to the normal knee, possibly alsoresulting in a higher incidence of bearing dislocation.With the exception of dislocation, the overall early complication ratio in the initial publishedseries of lateral Oxford UKR was also rather high compared to the last published series. Is therea learning curve?Materials and Methods.Between January 2009 and April 2010, 16 domed lateral Oxford unicompartmental kneereplacements were implanted by the senior author. The valgus deformity was in 2 cases notcompletely correctable. All femoral components were positioned anatomically. In no case thepopliteus tendon was divided. A partial iliotibial band (ITB) release was done in 2 cases. Themost common tracking deviation of the bearing peroperatively was a small lift off in deepflexion, seen in 6 cases.file:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]