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to 8% of THA patients have cups malaligned in version by more than ±10º outside of theLewinnek safe zone. This type of malalignment may result in dislocation of the femoral headand instability of the joint within the first year, requiring reoperation. Reported incidences ofreoperation are 1-9% depending on surgical skills and technique. In addition, cup malalignmentis becoming increasingly important as adoption of hard on hard bearings increases as thesuccess of large head hard on hard bearings seems to be more sensitive to cup positioning. Thisstudy reports the accuracy of a haptic robotic system to ream the acetabulum and impact anacetabular cup compared to manual instrumentation.MethodsSix fresh frozen cadaveric acetabula were CT scanned and three-dimensional templating of thecenter of rotation, anteversion and inclination of the cup was determined pre-operatively. Halfof the specimens were prepared with manual instrumentation while half were prepared withrobotic guidance. Haptic and visual feedback were provided through robotics and an associatednavigation system to guide reaming and impaction of the cup. The robot constrained theorientation and position of the instruments thus constraining the inclination, anteversion andcenter of rotation of the reamer, trial and the final cup. Post-operative CT’s were used todetermine the achieved cup placement and compared to the pre-operative plans.ResultsIn all cases, robotic guidance resulted in placement of the acetabular cup within ±3° ofanteversion, ±3° of relative to the pre-op plan. The average absolute inclination error was1.5±1.2° and the average absolute anteversion error 1.3±1.4°. Cup placement with roboticassistance was significantly more accurate and precise than with manual instrumentation. Withmanual instrumentation the errors were, on average, 4.2 times higher in inclination and 4.8times higher in anteversion compared to robotic instrumentation.ConclusionThis haptic robotic system substantially improved the accuracy of acetabular reaming andplacement of the final cup compared to traditional manual techniques. With greater knowledgeof ideal acetabular cup position, highly accurate techniques may allow surgeons to decrease therisk of dislocation, promote durability and improve the ability to restore appropriate leg lengthand offset. Haptic robotics has proven to be safe and effective in both knee and hip surgery andprovides the potential to redefine the “instrument set” used for orthopedic procedures.Friday, October 8, 2010, 15:20-16:00Session B14: Hip ResurfacingFunctional Outcome of the Birmingham Hip Resurfacing: 300 PatientsWith a 2 to 7 Year Follow-Up in a Non-Designer Centre*Erwin Jansegers - Sint-Augustinus Hospital - Wilrijk/Antwerp, Belgium*Email: jansegerserwin@yahoo.comfile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]