Reliable Alignment in Total Knee Arthroplasty by the Use ofan iPod-Based Navigation System

Axial alignment is one of the main objectives in total knee arthroplasty (TKA). Computer-assisted surgery (CAS) is more accurateregarding limb alignment reconstruction compared to the conventional technique. The aim of this study was to analyse theprecision of the innovative navigation system DASHby Brainlab and to evaluate the reliability of intraoperatively acquireddata. A retrospective analysis of 40 patients was performed, who underwent CAS TKA using the iPod-based navigation systemDASH. Pre- and postoperative axial alignment were measured on standardized radiographs by two independent observers. Thesedata were compared with the navigation data. Furthermore, interobserver reliability was measured. The duration of surgery wasmonitored. The mean difference between the preoperative mechanical axis by X-ray and the first intraoperatively measured limbaxis by the navigation system was 2.4∘. The postoperative X-rays showed a mean difference of 1.3∘compared to the final navigationmeasurement. According to radiographic measurements, 88% of arthroplasties had a postoperative limb axis within±3∘.Themeanadditional time needed for navigation was 5 minutes. We could prove very good precision for the DASH system, which is comparableto established navigation devices with only negligible expenditure of time compared to conventional TKA.