Background: Few studies have compared the effect of different computer navigation systems on postoperative alignment in patients who have had total knee arthroplasty (TKA). We examined 2 computed tomography (CT)-free computer navigation systems by comparing the accuracy of intraoperative measurements to postoperative alignment. Methods:Patients underwent unilateral TKA performed by a single surgeon using 1 of 2 CT-free navigation systems. We compared final intraoperative tibial and femoral coronal angles and mechanical axis with the same angles measured on standing postoperative radiographs.Results: Groups of 31 and 50 patients underwent TKA with the 2 systems, respectively. We noted a significant difference in the coronal tibial implant angle (1.29º ± 1.35º) and in the mechanical axis (1.59º ± 2.36º) for one navigation system (both p < 0.001), while only the coronal tibial implant angle showed a significant difference (1.17º ± 1.65º, p < 0.001) for the second system. The number of radiographic outliers also significantly differed. A significantly higher proportion (32%; p < 0.01) of patients in the second cohort exhibited unacceptable malalignment compared with the first cohort (24%). Conclusion:Navigation systems for TKA continue to increase in sophistication and popularity. Owing to the significant difference in the proportion of alignment outliers in the 2 navigation systems tested in this study, orthopedic surgeons should not consider all TKA navigation systems equivalent. Additional investigations are needed to compare the accuracy of a variety of CT-free and CT-based navigation systems and to confirm our finding that accuracy is system-dependent.

Ceramic-on-ceramic articulations have become an attractive option for total hip arthroplasty in young patients. In this study, we retrospectively evaluated the short- to midterm clinical and radiographic results in 51 consecutive patients (61 hips) using the newest generation of ceramic implants. Results obtained in our study showed positive clinical and radiological outcomes. Both HHS and UCLA activity scores doubled after surgery and tended to increase over time. There was one infection requiring a two-stage revision and a case of squeaking that began 2 years postoperatively after a mechanical fall. The overall survival rate of the implants was 98.4% at six years with revision for any reason as the end point. Based on these results, fourth generation ceramics offer a viable option for young and active patients.

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