Objective To design an atlantoaxial lateral mass fusion cage and evaluate its biomechanical stability when it is combined with atlantoaxial vertebral pedicle screw fixation.Methods Forty-six sets of CT 3D reconstruction pieces of the normal atlantoaxial junction were chosen to measure sagittal diameter and transverse diameter of atlantoaxial lateral mass joint,sagittal diameter and transverse diameter of epistropheus lateral mass and space height of atlantoaxial lateral mass joint.An atlantoaxial lateral mass fusion cage was designed on this basis.Six fresh human cadaveric cervical spines (C0-C4) were used as samples to measure 3D motion range of C1,and 2 segments under 1.5 N · m load.3D motion range of samples under the following situations was measured at random:intact state,unstable state (ligament around odontoid process was cut off),fixation with atlantoaxial joint screw+Gallie steel wire,atlantoaxial pedicle screw,atlantoaxial lateral mass joint fusion cage+atlantoaxial vertebral pedicle screw.Results Corresponding width/length of fusion cage is 8/11,9/12,10/13 mm,respectively,and the height is designed to 3.5,4.0,and 4.5 mm,respectively.The motion range of three internal fixation methods is less than that under intact state and unstable state.The difference has statistical significance.The C1+C2+cage fixation produces the least motion range in lateral bending and axial rotation directions and generates the highest motion range in flexion/extension direction.But,the difference has no statistical significance.Conclusion The C1+C2+cage internal fixation technique has similar stability with common atlantoaxial intemal fixation method and can provide extra atlantoaxial fusion spots.Thus,it may be a feasible alternative for atlantoaxial fusion when the posterior arch of the atlas is absent.

Objective To evaluate the outcome of posterior screw-rod fixation system in reduction and internal fixation of atlantoaxial dislocation. Methods A retrospective study was done on 27 patients with atlantoaxial instability including 18 male and 9 female (at age range of 13-51 years, mean 31 years) from January 2007 to May 2009. There were 11 patients with chronic odontoid fractures, five with isolated bone odontoid, seven with transverse ligament rupture of atlas and four with rheumatoid arthritis. Skeletal reduction was performed in all the patients. The anterior atlantodens interval (ADI)ranged from 8 mm to 15 mm, average 11 mm. All the patients underwent an intraoperative reduction by posterior C1 lateral mass and C2 pedicle screws with rod fixation. According to American Spine Injury Association (ASIA) impairment scale, there were eight patients at grade B, 15 at grade C and four at grade D. Results All patients were followed up for 6-24 months (average 13 months), which showed that the neck symptoms were improved, with bony union. The ADI was reduced to 2-4 mm (average 2.8 mm)postoperatively. Postoperative ASIA scale was grade C in four patients, grade D in 12 and grade E in 11.There were no neurologic or vascular complications occurred, or no failure of the internal fixtors, pseudarthrosis or instability. Conclusion Posterior screw-rod fixation system has advantages of simple procedures, few complications and good results and can be used for intraoperative reduction of atlantoaxial dislocation.

Mass spectrometry imaging (MSI), a label-free molecular imaging technique, has been applied widely in the spatial localization of small molecule metabolites, lipids, peptides, and proteins, with its unique advantage of high spatial resolving power compared to traditional liquid chromatography-mass spectrometry (LC-MS).With the nonstop advancement of its achievable sensitivity and spatial resolution, MSI technique has been providing novel perspectives into the preclinical studies of drugs, such as in vivo localization of drugs and their metabolites, visualization of drug metabolism, and drug delivery tracking.This review introduces the basics of MSI techniques, including basic principles, key features, technical advantages, and limitations, with particular highlight of the recent applications of MSI in drug efficacy and safety evaluation, drug distribution research, drug delivery research, and analysis of Chinese medicine from recent publications, aiming to promote the utilization and further expansion of MSI in the research and development of drugs.

Lumbar spondylolysis is one of the common diseases of low back pain caused by spinal surgery. Its treatment options vary depending on different conditions, from early conservative ones to late surgical ones. There are still disputes over various conservative treatments, choice of surgical methods and the biomechanics of different internal fixation techniques to repair spondylolysis. Therefore, this review summarizes the clinical outcomes of previous clinical treatments of lumbar spondylolysis and the biomechanical characteristics of various techniques to find the mechanical and evidence-based clinical data that may facilitate the treatment of lumbar spondylolysis.

Objective:To design an improved lamina hook system and compare its biomechanical properties with traditional lamina hook system in fixation of lumbar spondylolysis.Methods:The thin layer CT data of the lumbosacral vertebrae of 20 healthy young male servicemen who underwent physical examination in the outpatient department of the 940th Hospital of Joint Logistics Support Force of PLA from January 2021 to August 2022 were collected. The age of the subjects was 20-30 years [(25.0±3.0)years]. A 3-dimensional model of the L 5 vertebral body was constructed using the 3-dimensional modeling software. The new improved lamina hook was designed according to the measurements including the thickness of the middle area, the longest longitudinal diameter, the curvature radius of the lower edge, the angle between the upper and lower tail ends, the thickness of the lower edge, and the longest diameter of the lower edge of the bilateral L 5 vertebral plates. One serviceman was selected from the aforementioned group to construct a linear finite element model of segments L 4-S using the 3-dimensional virtual software (normal model, model A), based on which, the L 5 bilateral spondylolysis model (model B), improved lamina hook model (model C) and traditional lamina hook models (model D) were designed. By constraining both sides of the sacrum and applying a longitudinal load of 400 N on the L 4 vertebral body, the upper 1/3 gravity of the body was simulated, and with a bending moment of 10 N·m along the X, Y, and Z directions, motions of forward flexion, backward extension, lateral bending, rotation, etc were simulated. The range of motion of segment L 4/5 and L 5/S 1 of model A was evaluated and compared with the findings of the previous researches to verify its effectiveness. The overall range of motion of models A, B, C, and D, the range of motion of segment L 4/5 and L 5/S 1, the maximum overall displacement, the maximum displacement and stress of the isthmus, the stress distribution and maximum stress of internal fixation of models C and D, and the stress distribution and maximum stress of the vertebral body of models C and D were compared. Results:(1) During forward flexion, backward extension, lateral bending and rotation, the range of motion of model A was 5.01°, 4.03°, 3.91° and 1.42° in segment L 4/5, and was 4.62°, 2.51°, 2.40° and 1.23° in segment L 5/S 1. (2) The overall range of motion, range of motion of segment L 4/5 and L 5/S 1 and maximum overall displacement of models A, C, and D were similar in axial compression, forward flexion, backward extension, left bending, and left rotation, while those of model B were significantly increased. (3) There was no significant difference in the maximum displacement of the isthmus of models A, C, and D under different motion modes, while the maximum displacement of model B in the isthmus was significantly larger than that of models A, C, and D, especially during rotation, increased by 295%, 277%, and 276% respectively. The maximum stress of the isthmus of model C was 0.938 MPa, 1.698 MPa, 0.410 MPa, 2.775 MPa, and 1.554 MPa respectively. The maximum stress in the isthmus of model D was 0.590 MPa, 1.297 MPa, 0.520 MPa, 3.088 MPa, and 2.072 MPa respectively. The maximum stress of the isthmus of models C and D was similar during axial compression and forward flexion, while the stress of the isthmus of model C was smaller than that of model D during backward extension, lateral bending, and rotation, decreased by 21.1%, 10.2%, and 25.0% respectively compared with model D. (4) The maximum stress of internal fixation in models C and D during forward flexion, backward extension, left bending, and left rotation was 135.220 MPa, 130.180 MPa, 200.940 MPa and 306.340 MPa respectively, and was 131.840 MPa, 112.280 MPa, 349.980 MPa and 370.140 MPa respectively. The maximum stress of internal fixation in the two models of internal fixation during forward flexion and backward extension was similar, while it was decreased by 42.6% and 17.2% in model C during left bending and left rotation, compared with model D. (5) The maximum stress of the vertebral body during forward flexion, backward extension, left bending, and left rotation was 79.787 MPa, 36.857 MPa, 37.943 MPa and 96.965 MPa respectively in model C, but was 80.104 MPa, 64.236 MPa, 196.010 MPa and 193.020 MPa respectively in model D. The maximum stress of models C and D was all distributed in the contact area with the internal fixation, and especially during backward extension, left bending, and left rotation, when it was reduced by 42.6%, 80.6%, and 49.8% of model C respectively, compared with that of model D. Conclusions:The improved laminar hook is more consistent with the Chinese anatomized structure of the lamina. Compared with the traditional lamina hook system, the improved lamina hook system can effectively reduce the displacement in all directions and range of motion of lumbar spondylolysis, therefor can significantly reduce the stress of internal fixation and vertebral body and has better biomechanical performance.