Comparison of Piezosurgery and Conventional Osteotomy for Orbital Hypertelorism Surgical Correction.

The purpose of this study was to compare the safety and effect of piezosurgery with conventional osteotomy in a box-shifting procedure for orbital hypertelorism (ORH) correction surgery. This study retrospectively analyzed the clinical record of 10 ORH patients aged from 5 to 12 years, and they were second-degree ORH with an interorbital distance (IOD) of 35 to 37.8 mm. Three of them received the osteotomy with piezosurgery (the piezosurgery group), whereas the other 7 patients received osteotomy with the conventional osteotomy method (the control group). They were compared with age and preoperative IOD. All the patients' IOD was effectively improved to normal range after the surgery. The results showed that the application of piezosurgery did not prolong the surgery time (piezosurgery group: 8.3±0.5 hours; control group: 8.7±1.4 hours, P =0.68). Furthermore, the patients in the piezosurgery group had less drainage volume (piezosurgery group: 79.1±12 mL; the control group: 170±41.3 mL, P =0.0065) and shorter postoperative hospital stay (piezosurgery group: 8.3±2.0 d; control group: 12.43±2.29 d, P =0.029). There were 2 patients who had wound infections, 1 in the piezosurgery group and 1 in the control group, respectively. However, 1 patient in the control group suffered from cerebrospinal fluid leakage. On the basis of the results, the application of piezosurgery benefited the patients on a better and smoother recovery course with less drainage and shorter hospital stays. The advantages of piezosurgery are the fine and precise osteotomy and the protection for soft tissue, which make it a comparatively safe and effective tool for craniofacial surgery, especially for young patients.

On the Evolution of Temperature and Combined Stress in a Work Roll under Cyclic Thermo-Mechanical Loadings during Hot Strip Rolling and Idling.

An accurate prediction of temperature and stress evolution in work rolls is crucial to assess the service life of the work roll. In this paper, a finite element method (FEM) model with a deformable work roll and a meshed, rigid body considering complex thermal boundary conditions over the roll surface is proposed to assess the temperature and the thermal stress in work rolls during hot rolling and subsequent idling. After that, work rolls affected by the combined action of temperature gradient and rolling pressure are investigated by taking account of the hot strip. The accuracy of the proposed model is verified through comparison with the calculation results obtained from the mathematical model. The results show that thermal stress is dominant in the bite region of work rolls during hot rolling. Afterwards, the heat treatment residual stresses which are related to thermal fatigue are simulated and introduced into the work roll as the initial stress to evaluate the redistribution under the thermal cyclic loads during the hot rolling process. Results show that the residual stress significantly changed near the roll surface.