PubMed · 15891785
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
Aldo Carano, Birte Melsen. 2005. Implants in orthodontics. Interview.. https://pubmed.ncbi.nlm.nih.gov/15891785/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Navigation procedures in orthopedic surgery require fixation of reference markers to the anatomic region of interest. Inadequate fixation might lead to micromotion or loosening of the reference marker, consequently causing registration failures or errors in navigation. Osseous rigid fixation is usually achieved by minimally invasive Schanz screws or pins. The goal of this study was to evaluate a non invasive external fixation device, a headband so far used in cranial navigation, as an alternative invasive fixation technique to reference markers in the femur. A common navigation system with an adapted trauma software application was used to track the positions of the soft tissue-attached headband relative to an invasive reference marker on the femur during manipulations of the thigh. Relative translative and rotational movements of the headband were measured during defined movements of the hip and knee and manipulations of the headband itself. The results revealed high translative and rotational movements, up to 6 mm and 3 degrees , respectively, due to minor manipulations of the affected lower extremity. Noninvasive soft tissue fixation with a headband does not allow rigid fixation for accurate navigated registration or operative procedures at the femur. Necessary intraoperative movements or manipulations would cause substantial registration failures. Invasive fixation techniques with screws or pins are still the method of choice.
Computer-assisted orthopaedic surgery has developed considerably during the past few years. Several manufacturers produce hardware and software for use in trauma surgery. Validation of these systems before clinical application is mandatory to be sure they work accurately and safely. The accuracy of surgical performance is highly correlated with the cut-out percentages of hip screws. In a standardized operative setting, three cannulated hip screws were inserted in each of 20 sawbones. The screws were positioned either by fluoroscopic navigation technique or by conventional operative technique depending on randomization. Our primary aim was to assess whether computer-navigated screw fixation is equally safe compared with conventional screw fixation using fluoroscopy. To determine safety, we investigated number of drilling attempts, screw position, and radiation time. Secondary to these safety parameters, we also compared the operating time between the two procedures to assess the efficiency of computer navigation. Statistical analysis showed no differences regarding accuracy of screw position. Computer-assisted surgery resulted in fewer drilling attempts and less radiation time, with a similar operation time. We believe the currently used navigation system is safe and accurate.
BACKGROUND: Owing to the complexity and magnitude of functional forces transferred to the bone-implant interface, the mechanical strength of the interface is of great importance. The purpose of this study was to determine the intraosseous torsional shear strength of an osseointegrated oral implant using 3-D finite element (FE) stress analysis implemented by in vivo failure torque data of an implant. METHODS: A Ø 3.5 mm x 12 mm ITI hollow screw dental implant in a patient was subjected to torque failure test using a custom-made strain-gauged manual torque wrench connected to a data acquisition system. The 3-D FE model of the implant and peri-implant circumstances was constructed. The in vivo strain data was converted to torque units (N x cm) to involve in loading definition of FE analysis. Upon processing of the FE analysis, the shear stress of peri-implant bone was evaluated to assume torsional shear stress strength of the bone-implant interface. RESULTS: The in vivo torque failure test yielded 5952 microstrains at custom-made manual torque wrench level and conversion of the strain data resulted in 750 N.cm. FE revealed that highest shear stress value in the trabecular bone, 121 MPa, was located at the first intimate contact with implant. Trabecular bone in contact with external surface of hollow implant body participated shear stress distribution, but not the bone resting inside of the hollow. CONCLUSION: The torsional strength of hollow-screw implants is basically provided by the marginal bone and the hollow part has negligible effect on interfacial shear strength.