Abnormal rate of intraoperative and postoperative implant positioning outliers using ``MRI-based patient-specific'' compared to ``computer assisted'' instrumentation in total knee replacement

International audienceThe aim of this study was to analyze first intraoperative alignment and reason to abandon the use of patient-specific instrumentation using intraoperative CAS measurement, secondly assess by postoperative CT analysis if CI, based on preoperative 3D-MRI data, improved postoperative component positioning (including femoral rotation) and lower limb alignment as compared with results obtained with CAS. In this randomized controlled trial, 80 consecutive patients scheduled to undergo TKA were enrolled. Eligible knees were randomized to the group of PSI-TKAs (n = 40) or to the group of CAS-TKAs (n = 40). In the CAS group, CAS determined and controlled cutting block positioning in each plane. In the PSI group, CAS allowed to measure adequacy of intraoperative alignment including femoral component rotation. At 3 months after surgery, implants position were measured and analyzed with full-weight bearing plain radiographs and CT scan. Intraoperatively, there was a significant difference concerning Sagittal Femoral mechanical, Frontal tibial mechanical angle and tibial slope between the two groups (respectively p = 0.01, p = 0.02, p = 0.046). Custom instrumentation was abandoned intraoperatively in seven knees (17.5 %). Abnormal tibial cuts were responsible of the abandon in three out of seven cases, femoral cut in 1/7 and dual abnormalities in 3/7. Postoperatively, tibial slope outliers percentage was higher in the patient specific instrumentation group with six patients (18.18 %) versus one patient (2.5 %) in the CAS group (p = 0.041). Patient specific instrumentation was associated with an important number of hazardous cut and a higher rate of outliers in our series and thus should be used with caution as related to. This study is the first to our acknowledgement to compare intra-operative ancillary and implant positioning of PSI-TKA and CAS-TKA. High rate of malposition are sustained by our findings, as such PSI-TKA should be used with caution, by surgeons capable to switch to conventional instrumentation intra-operatively. Randomized control trial, Level I

X-38 Aerothermodynamics

Dassault Aviation has been selected to conduct the aerodynamic as well as aerothermodynamic vehicle studies to be performed in Europe. The general methodology for the aerothermodynamic data basing of x-38 in the framework of the NASA-ESA cooperation on NASA X-38-CRV (Crew Return Vehicle) demonstrator progra

Synthesis of contributions to the hyperboloid-flare in F4 test case TC1.C

Communication to : Manned space transportation programme workshop 1996 reentry aerodynamics and ground-to-flight extrapolation, ESA/ESTEC, Noordwijk (The Netherlands), March 25-27, 1996SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1996 n.207 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

X-38: A Testbed for the CEVCATS-N Code

The paper focuses on today possibility of using a Navier-Stokes code as design/verification tool for the hypersonic regime, on a real engineering environment. Within the frame of Dassault Aviation work for NASA X-38 demonstrator, DLR has performed more than two hundered CFD solutions, Euler and Navier-Stokes, demonstrating that the DLR computer code CEVCATS-N satisfies all criterion to be considered a reliable tool. That is, fulfilling concepts like accuracy, efficiency, flexibility and robustness for a wide spectrum of geometrical shapes and flow conditions