Regression and correlation analysis of preoperative versus intraoperative assessment of axes during navigated total knee arthroplasty.

OBJECTIVE: Modern computer assisted surgery (CAS) systems allow accurate positioning of the implants in navigated Total Knee Arthroplasty (TKA). However, when an operation is performed with a navigation system, it is important to know if the anatomical situation of the knee is reflected equally in both the preoperative image (e.g., CT) and the intraoperative navigation setup. In this study, we compared the preoperative anatomical situation to the virtual intraoperative situation of the navigation setup. MATERIAL AND METHODS: We analyzed 24 navigated operations. Intraoperatively, the condylar twist angle (CTA) was documented with the navigation system by measuring the angle between the transepicondylar axis (TEA) and posterior condyle axis (PCA). This data was compared with the preoperative data from the CT scan. RESULTS: Statistical analysis revealed that there was no correlation between the pre- and intraoperative data (r = 0.095). CONCLUSIONS: Statistically, there is no possibility of collecting the same angles and axes when using the two different methods (CT and navigation) on the same knee. It is not possible to copy the preoperative anatomical situation exactly with the virtual intraoperative data. Reasons for this include systematic errors, as well as inter- and intraobserver errors in both methods.

[Magnetic resonance tomography of the scrotum. Experiences with 129 patients]. / Magnetresonanztomographie des Skrotums. Erfahrungen an 129 Patienten.

In our study 129 patients underwent MR imaging for evaluation of the scrotum with spin-echo pulse sequence (proton density and T2-weighted images). The final diagnosis was confirmed by surgery in 54 patients. Our findings show that MRI is a powerful supplementary technique for scrotal imaging when ultrasound findings are unclear or are inconsistent with the clinical history. MRI can reduce the number of unnecessary exploratory operations on the testis, though surgery is unavoidable if the findings are equivocal. Differentiation and specification of tumours cannot be achieved by MRI, nor does it allow accurate evaluation of subacute torsion of the testis. In these cases dynamic MRT following intravenous administration of Gd-DTPA may improve the diagnostic accuracy.