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Use of a novel ligament gap balancing instrumentation system in total knee arthroplastyresulted in femoral component external rotation values which were higher on average, comparedto measured resection systems. In one hundred twenty knees in 110 patients the externalrotation averaged 6.9 degrees (+/- 2.8) and ranged from 0.6 to 12.8 degrees. The externalrotation values in this study were 4º and 2º larger, respectively, than the typical 3º and 5ºdiscrete values that are common to measured resection systems. The purpose of the presentstudy was to determine the effect of these greater external rotation values for the femoralcomponent on patellar tracking and flexion instability.METHODSOne hundred twenty knees in 110 patients were consecutively enrolled by a single surgeonusing the same implant across subjects. All patients underwent arthroplasty with tibial resectionfirst and that set external rotation of the femoral component based upon use of a ligament gapbalancing system. Following ligament tensioning / balancing, the femur was prepared. Theaccuracy of the ligament balancing system was assessed by reapplying equal tension to theligaments using a tensioning bolt and torque wrench in flexion and extension after the boneresections had been made. The resulting flexion and extension gaps were then measured todetermine rectangular shape and equality of the gaps. Postoperative Merchant views wereobtained on all of the patients and patellar tracking was assessed and compared to 120consecutive total knee arthroplasties previously performed by the same surgeon with the sameimplant using a measured resection system.RESULTSRectangular flexion and extension gaps were obtained within +/- 0.5mm in all cases. Equalityof the flexion and extension gaps was also obtained within +/- 0.5mm in all cases. Merchantviews of the total knee arthroplasties showed central patellar tracking with no tilt or subluxationin 90% of the ligament gap balanced knees and 74% of the measured resection knees.DISCUSSION AND CONCLUSIONExternal rotation values are higher on average, when ligament tensioning / balancing isemployed with this novel system compared to measured resection systems. In this study thisresulted in consistent matching of the flexion gap to the extension gap and better patellartracking. These findings suggest that limiting the surgeon to discrete rotation values may be atodds with where the femur “desires” to be, given soft tissue considerations for each patient.Thursday, October 7, 2010, 15:10-15:50Session B7: Robotic Knee SurgeryTotal Knee Arthroplasty Following High Tibial Osteotomy.*Simone Ripanti - S.giovanni Hospital - Roma, ITALYSabina Marin - S.giovanni Hospital - ome, italyGiancarlo Romani - S.giovanni Hospital - rome, italyStefano Campi - CAMPUS BIOMEDICO UNIVERSITY - ROME, ITALYfile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]