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observers were able to do the experiment without surgical assistants. They found the templatesto be user-friendly and could be uniquely positioned, and held with one or 2 hands.DISCUSSIONMany authors 3,4,16,20,40 have questioned the accuracy of the surgical techniques for TKA, usingconventional instrumentation. The outcome of TKA is dependent on surgical techniques 7,8,36 ,and technical errors such as malalignment, may lead to early failure. 15,17,33,44 Variations insurgical performance and outliers in TKA still occur, and they may affect the outcome. 15-17,41Although the reported long-term implant survival for TKA in elderly patients is 90–95% after10–15 years. 12,32,33 , some authors have questioned the high success rates due, to pitfalls inoutcome measurement. 27,28 There is also a need to improve the relatively inferior outcomeresults of TKA for young, active patients, and revision surgery 32,35,38 , where the accuracy ofbone cutting is critical and errors can result in depletion of bone stock.Navigation and robotic techniques have recently been introduced, and several authors reportedtheir higher level of accuracy, compared with conventional instrumentations. 3,4,6,30,37,40However, navigation techniques still rely on conventional instrumentation for making thevarious bone cuts, and they require additional instruments and insertion of tracking pins. Thisdouble instrumentation system (navigation and conventional instrumentations) may overloadhospital inventory, sterilization services, and operating room time. The need to improveergonomics in the surgical workplace 39 would be more difficult with bulky navigation devicesthat require registration and continuous line of sight for tracking.Patient specific templating is another form of computer-assisted surgery and is based on theapplication of rapid prototyping technology. The latter has been used in dentistry andmaxillofacial surgery but its medical applications are still in their infancy. 24 Radermacher 31 firstreported this technique in orthopaedic applications, and there are few scattered reports 2,9 in theliterature describing its use for producing customized models and guides. A new generation ofpatient specific templating has been reported 10,11 , where templates act as a complete set ofinstruments for TKA that replace conventional instrumentation. The results of using thistechnique in 45 experimental TKA procedures, on 16 cadaveric and 29 plastic specimens werereported 11 . The templates eliminated medullary guides and significantly reduced operative time.The accuracy results were based on the analysis of postoperative CT scans for 6 randomcadaveric specimens. However, there was concern about the accuracy and reproducibility ofpositioning patient specific templates, particularly for new users.The technique of patient specific templating has its own drawbacks, as it requires CT scans,which are not a routine requirement for TKA. Unlike navigation, templating techniques do notnormally provide intraoperative measurements, since sizing, alignment and bone cutting aredetermined preoperatively. This study also has some limitations. The measurements for femoralrotation were only done for 3 observers, and were not complete. This was justified in theMethods section. Measurements were also done before, rather than after bone cutting. This hadthe advantage of eliminating errors, which are surgeon-dependent, rather than templatedependent.Intraoperative measurements using the current navigation techniques are routinelyperformed before bone cutting, as the cutting process itself cannot be navigated due to thevibration of the saw blades. It was also found to be unnecessary to waste resources and time, byfile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]