Objective To study the mechanical properties of titanium mesh and three-dimensional(3D)-printed metal vertebral body substitutes(VBS)to provide guidance for the selection and structural optimization of artificial vertebral implants in clinical practice.Methods The equivalent elastic modulus,equivalent yield strength,and structural failure mode of titanium mesh and 3D-printed porous,truss,and topologically optimized VBS were systematically investigated using compression tests.Results The elastic modulus of the titanium mesh(2 908.73±287.39 MPa)was only lower than that of the topologically optimized VBS.However,their structural strengths and stabilities were inadequate.The yield strength of the titanium mesh(46.61±4.85 MPa)was only higher than that of the porous VBS and it was the first to yield during compression.The porous VBS was insufficient for use as the vertebral implant owing to its poor mechanical strength(18.14±0.17 MPa-25.79±0.40 MPa).The truss VBS had good elastic modulus(2 477.86±55.19 MPa-2 620.08±194.36 MPa)and strength(77.61±0.50 MPa-88.42±1.07 MPa).However,the structural stability of the truss VBS was insufficient,and instability occurred easily during compression.The topologically optimized VBS had the highest elastic modulus(3 746.28±183.80 MPa)and yield strength(177.43±3.82 MPa)among all the tested VBS types,which could provide improved security and stability for artificial vertebral implant in vivo services.Conclusions Topology optimization results in a high strength and high stability VBS design.Moreover,it provides a large design space and great safety margin to provide increased possibilities for lightweight and new material design of future artificial vertebral implants.

Objective Aiming at the clinical problem of the low matching degree with the patient’s anatomical morphology for traditional cervical fusion cage, a cervical fusion cage with the function of adjustable height and the shape matched with the vertebral body was established, and its biomechanical properties were evaluated. Methods A cervical C4-5 segment fusion model was established according to anterior cervical discectomy and fusion (ACDF), so as to simulate different motion conditions, i.e. anterior flexion, posterior extension, left/right lateral flexion, left/right rotation, and stress of the fusion cage and vertebral endplate was calculated. After three-dimensional (3D) printing of the fusion cage, an in vitro mechanical experiment was conducted to explore safety and stability of the fusion cage. ResultsThe fusion cage could keep the range of motion (ROM) of cervical vertebrae at the fusion segment with 1°-2.8° and reduce the ROM to 40%-80% of the natural segment. In the in vitro compression test, the yield load of the fusion cage was (2 721.67±209) N, which met the maximum demand of the physiological load in service state. Conclusions The designed fusion device with adjustable height shows better biomechanical properties and can reduce the selection step in operation.

BACKGROUNDRat renal transplantation is an essential experimental model and requires greater microsurgical skills. Thus, training novices to perform quick and reliable microvascular anastomosis is of vital importance for rat renal transplantation. In this study, we developed and evaluated a staged microvascular anastomosis training program for novices, harvesting and transplanting both kidneys from one rat donor.

METHODSFive trainees without any prior microsurgical experience underwent a training program in which the goals were staged according to difficulty. Each trainee had to achieve satisfactory results as evaluated by a mentor before entering the next stage. Rat renal transplantation was accomplished by end-to-end technique with a bladder patch. In the intensive rat renal transplantation stage, the trainees required an average of 20 independent attempts at isotransplantation as final training assessment.

RESULTSAfter 2 months of intensive practice, all trainees had achieved stable and reproducible rat renal transplantation, with a satisfactory survival rate of 85.9% at postoperative Day 7. The total mean operative time was 78.0 minutes and the mean hot ischemia time was 26.2 minutes. With experience increasing, the operative time for each trainee showed a decreasing trend, from 90-100 minutes to 60-70 minutes. After 20 cases, the mean operative time of the trainees was not statistically significantly different from that of the mentor.

CONCLUSIONHarvesting and transplanting both kidneys from one rat donor after a staged microvascular anastomosis training program is feasible for novices without any prior microsurgical skills.

Animals ; Kidney Transplantation ; education ; Male ; Microsurgery ; education ; Operative Time ; Rats ; Rats, Sprague-Dawley ; Tissue and Organ Harvesting ; education

Objective: To investigate the relationship between duration of sleep and all-cause mortality in patients with type 2 diabetes. Methods: A total of 17 452 type 2 diabetic patients who were under the National Basic Public Health Service Project, in Changshu county, Qinghe district and Huai’an district in Huai’an city of Jiangsu province, were recruited as participants. Cox proportional hazards regression models were used to estimate the associations between different levels on the duration of sleep and all-cause mortality. Stratified analysis was performed according to factors as gender, age, and lifestyle. Results: Among the 67 912 person-years of observation, from the fo1low- up program, the median time of follow-up was 4 years, with 1 057 deaths occurred during the follow-up period. Taking patients with duration of sleep as 7 h/d for reference, the multivariate adjusted hazard ratios (95%CI) of all-cause mortality appeared as ≤6, 8, 9 and ≥10 h/d were 1.14 (0.94-1.37), 1.10 (0.91-1.32), 1.33 (1.05-1.70), and 1.52 (1.24-1.87), respectively which were associated with the duration of sleep. Data from the subgroup analysis showed that this was consistent with the whole population. Longer duration of sleep was associated with the all-cause mortality but no significant association was found between shorter duration of sleep and the all-cause mortality. Conclusion Longer duration of sleep seemed to have increased the risk of all-cause mortality in type 2 diabetic patients.