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allowing bone cutting to consume 25 specimens of plastic knee models.The results of this study showed a satisfactory level of accuracy with a mean alignment error of0.67º (maximum 2.5º). The mean error for bone cutting was 0.32 mm (maximum 1 mm). Thisstudy also showed that the positioning of the templates is reliable, as there was no significantintraobserver and interobserver variation for alignment, or levels of bone cutting, in both thefemur and the tibia. This is comparable with the results of a postoperative CT scan that wasdone for the patient specific templating technique in a previous study 11 , where the mean errorsfor alignment and bone cutting were within 1.7º and 0.8 mm, and maximum errors were lessthan 2.3º or 1.2 mm. The level of accuracy and reliability is better than what is reported 33,40,41for conventional techniques that had errors > 3º. This level of accuracy also comparesfavourably with the results of navigation 3,4,6,30,40 (within 3º) but less than what is reported byrobotic techniques (within 1º). 37The patient specific templating has therefore the potential to be used as a training tool, allowingcomplete planning of surgery with 3-D simulation that facilitates identification and correction oferrors in real time. Also, it allows the measurement of surgical performance, by comparingpostoperative imaging with the recorded preoperative planning. Rapid prototyping machines canproduce a patient specific model of the knee joint, based on the CT scan data of the patient.Thus, the surgeon can perform TKA on the patient’s model and evaluate the results beforeoperating on the real patient. The Patient-specific templating is suitable for patients with kneedeformities, in which intramedullary rods cannot be used. This technique also has the potentialto reduce the risk of infection, by shortening the operative time and eliminating medullaryperforation, excessive bleeding and tracking pins (in the case of navigation techniques). Since itprovides single use instruments, it may be useful in areas where there is a high risk of variantCreutzfeldt-Jakob Disease (vCJD) that requires an extraordinarily high level of sterlization. 42Other imaging modalities may be used in the future, such as MRI or 3-D radiographX-ray. 34This templating technique has the potential to be used for other procedures, such asunicompartmental knee arthroplasty.Conclusion:This study showed a satisfactory level of accuracy and reliability of the computer assistedpatient specific templating technique for total knee arthroplasty. It appears that the patientspecific templating technique has several advantages over conventional instrumentation, as iteliminates medullary guides, reduces operative time, and provides better accuracy. We believethat this technique is a practical alternative to navigation and robotic techniques for TKA.AcknowledgementAuthors would like to thank the staff at The Institute for Computer Assisted OrthopaedicSurgery (ICAOS), Western Pennsylvania Hospital, Pittsburgh, PA who participated and/orhelped in conducting this study. Also, we are grateful to the contributions of Keyworth Institute,University of Leeds; the Radiology Department, St. Luke Hospital Bradford; DePuyInternational Ltd, Leeds; Materialise, Belgium; the Engineering and Physical Sciences ResearchCouncil (EPSRC); and the Arthritis Research Council (ARC).file:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]