Accurate Orientation of the t-Branch Off-the-Shelf Multibranched Endograft After Deployment in Urgent Cases

Purpose: To evaluate the orientation of the standardized off-the-shelf multibranched t-Branch after implantation in urgent thoracoabdominal aortic aneurysm (TAAA) repairs, to characterize the impact of branch malorientation on procedural success, and to identify any predictive factors associated with malorientation. Methods: A retrospective analysis was conducted of 42 consecutive patients (mean age 73.3±7 years; 25 men) with urgent TAAA presentation treated with the t-Branch from January 2014 to June 2017. The primary objective was to quantify the preoperative clock position of the target vessels and determine any rotational deviation between the pre- and postoperative measurements and between the postoperative measurements and the standard branch configuration. Secondary outcomes were to identify factors influencing malorientation (>2 clock face hours) that could affect outcome. Results were compared for early (learning curve; n=18) vs late (n=24) experience and for adherence to (n=23) vs nonobservance of (n=19) the instructions for use (IFU). Results: Technical success was 93% (39/42). No significant difference in rotational deviation was identified between patients treated within the IFU vs outside the IFU. Seven (17%) patients had at least one target vessel maloriented after the procedure, which was not associated with total procedure time, fluoroscopy time, contrast volume, radiation dose, or adherence to the IFU. Female gender was associated with increased rotational deviation in postprocedure measurement for the celiac trunk (p=0.044) and superior mesenteric artery (SMA; p=0.006). Female gender was also associated with increased rotational deviation between the branch origin after deployment and the standard configuration of the t-Branch for every target vessel [celiac trunk (p=0.005), SMA (p=0.001), right renal artery (p=0.037), and left renal artery (p=0.003)]. Conclusion: The implantation of the t-Branch device in urgent cases achieved accurate apposition without rotational deviation between the target vessels and the position of the endograft branches. Gender may have an impact on orientation of the device. The t-Branch appears to have a “forgiving” nature for higher malorientation with no effect on procedure time, target vessel revascularization, or early branch patency.

In Vivo Tibial Fit and Rotational Analysis of a Customized, Patient-Specific TKA versus Off-the-Shelf TKA

In total knee arthroplasty (TKA), surgeons often face the decision of maximizing tibial component fit and achieving correct rotational alignment at the same time. Customized implants (CIMs) address this difficulty by aiming to replicate the anatomical joint structure, utilizing data from patient-specific knee geometry during the manufacturing. We intraoperatively compared component fit in four tibial zones of a CIM to that of three different off-the-shelf (OTS) TKA designs in 44 knees. Additionally, we assessed the rotational alignment of the tibia using computed tomography (CT)-based computer aided design model analysis. Overall the CIM device showed significantly better component fit than the OTS TKAs. While 18% of OTS designs presented an implant overhang of 3 mm or more, none of the CIM components did (p < 0.05). There was a larger percentage of CIMs seen with optimal fit (≤1 mm implant overhang to ≤1 mm tibial bone undercoverage) than in OTS TKAs. Also, OTS implants showed significantly more component underhang of ≥3 mm than the CIM design (37 vs. 18%). The rotational analysis revealed that 45% of the OTS tibial components showed a rotational deviation of more than 5 degrees and 4% of more than 10 degrees to a tibial rotational axis described by Cobb et al. No deviation was seen for the CIM, as the device is designed along this axis. Using the medial one-third of the tibial tubercle as the rotational landmark, 95% of the OTS trays demonstrated a rotational deviation of more than 5 degrees and 73% of more than 10 degrees compared with 73% of CIM tibial trays with more than 5 degrees and 27% with more than 10 degrees. Based on our findings, we believe that the CIM TKA provides both better rotational alignment and tibial fit without causing overhang of the tibial tray than the three examined OTS implants.

Dimensional Accuracy of Optical Bite Registration in Single and Multiple Unit Restorations

SUMMARY The dimensional accuracy of optical bite registration in the CEREC system was compared to that of the conventional physical method in vitro using a bite registration material. Maxillary and mandibular full-arch dentate epoxy models mounted on an articulator were used to measure the interarch distance and the angles created by the occlusal planes. The preparations for a single restoration on the maxillary first molar or for multiple restorations on the maxillary posterior quadrant were made on the model. Optical impression and bite registration data were collected to construct virtual models using computer-aided design software. A silicone material was used for the physical method, and the dimensional accuracy was measured by means of the coordinate measuring machine. The discrepancy relative to the baseline before preparation was analyzed in each registration record. For the single restoration, the optical method created a mean discrepancy of 243.2 μm relative to baseline at the prepared tooth, which was insignificantly but slightly lower than the mean discrepancy of 311.1 μm obtained with the physical method. The mean rotational deviation in the horizontal plane was significantly lower for the optical method. For the multiple preparations, the optical method showed significantly larger discrepancy on the right molar and on the left premolar and molar sites. In the frontal view, the optical method created significantly larger rotational deviation than the physical method. The result indicates that the optical bite registration was effective in terms of dimensional accuracy for single posterior restorations.

Study on Machining Error of Globoidal Cam Profile Resulting from Rotational Deviation of Location of Part in Machining

The profile error of a globoidal cam, resulting from rotational deviation of the location of the part in machining on a NC machine tool which has two coordinated rotational axes, is studied. A novel method of solving profile error is presented. According to this method, the minimum distance from a point on the profile actually machined to the desired profile is referred to as the profile error. Then, the mathematic model of profile error resulting from the rotational deviation of the part to be machined is built. After that, the type TC40 globoidal cam is employed as an example to solve the machining error. And the experiment of machining a globoidal cam is done. The experimental result is compared with the computed result, and they are mostly identical.