Objective To study the relationship between throid hormone and chronic heart failure in patients and its clinical significance. Methods The free thriiodothyronine( FT3 ), the total thriiodothyronine(TT3 ), the free thyroxine(FT4 ), the total thyroxine (TT4 ), the rebellion thriiodothyronine ( rT3 ), the thyroid stimulating hormone (TSH) in 100 patients with chronic heart failure and 50 normal people were determined by particle glimmer. Results The levels of T3 in patients with chronic heart failure were markedly lower than those in normal controls;The heart failure in low thriiodothyronine state case was severe. Conclusion The level of T3 in elderly patients with chronic heart failure was decreased, and it was correlated with the severity of heart failure.

Objective To construct three-dimensional finite element model of lumbar spondylolysis,then to verify its validity by comparison of biomechanics in vitro.Method According to the radiological data of a patient with lumbar spondylolysis,the bone and intervertebral disc of L4-S1 were reconstructed by Simpleware software.The lumbar attaching ligaments and articular capsule were added into simulating model by Ansys software.The three-dimensional finite element model of lumbar spondylolysis was finally simulated successfully,and validated by lumbar spondylolysis biomechanical experiment in vitro.Results The reconstruction of digital model contained the bones of lumbar spine which include vertebral cortical bone,cancellous bone,facet joint,pedicle,lamina,transverse process and spinous process,as well as the annulus fibrosus,nucleus pulposus,superior and inferior end-plates.Besides,anterior and posterior longitudinal ligaments,flavum ligament,supraspinal and interspinal ligaments and articular capsule of facet joint are also attached.The model consisted of 281,261 nodes and 661,150 elements.Imitation of spondylolysis is well done in this model.The validity of the model was verified by comparison of the results of biomechanics in vitro which involved in the trends under loading of stress/strain of L4 inferior facet process,L5 superior and inferior facet process,S1 superior facet process and the trends of stress/strain of lateral and medial L4 inferior facet process.Conclusions Three-dimensional model of lumbar spondylolysis is reconstructed using finite element analysis,and can be further used in the research in biomechanics of lumbar spondylolysis.

Axial pedicle screw fixation technique, as a classic posterior fixation technique, is the first choice and gold standard of posterior axial screw fixation. Since it can pass through the whole vertebrae and play the role of three-column fixation, it has excellent biomechanical properties and is widely used in cervical spine surgery. However, with the deepening of clinical research, some scholars found that the application of axial pedicle screws was limited in patients with pedicle hypoplasia, high-riding vertebral artery and irreducible atlantoaxial dislocation. At the same time, in order to expose bone markers during screw placement, the muscle dissection of pedicle screws is wider compared with that of isthmus screws. Isthmus screw fixation, as a complementary technique for pedicle screw technique, has gradually attracted the attention of scholars in recent years and has been applied in the surgical treatment of various types of cervical spine diseases. The entry point of axial isthmus screw is closer to the midline of the spine and the inferior facet joint than pedicle screw, to avoid extensive muscle dissection during the operation, so that the paravertebral muscles can be protected, which make the surgery more minimally invasive and the invasion of the operation further reduced. At the same time, compared with the lateral mass or pedicle screw of the atlas combined with axial pedicle screw fixation, the lateral mass or pedicle screw of the atlas combined with axial isthmus screw fixation can increase the anteroposterior and vertical distance between the heads of C 1 and C 2 screws due to the change of screw entry points, which can provide a wider operative space for the three dimensional reduction of atlantoaxial dislocation. However, since the axis is a transitional vertebra between the upper and lower cervical spine which has complexity and variability in anatomical structure, many scholars have limited understanding of this new technique. There are no unified standards for screw placement and surgical details, which are mostly based on the personal experience of clinicians. Meanwhile, the biomechanical properties, surgical complications and long-term efficacy of this technique have received little attention and concern, resulting in the limitation of clinical application and promotion for this technique. This review evaluates the relative advantages of axial isthmus screws according to existing literature reports, and analyzes the anatomy, biomechanics, clinical applications and surgical complications of axial isthmus screw fixation technique, aiming to provide a reference for the safety and feasibility of axial isthmus screw placement.