Complex biomechanical properties of non-augmented and augmented pedicle screws in human vertebrae with reduced bone density

[Cement augmentation in spinal surgery]

Bone cement has been used in spinal surgery for as long as 50 years. In contemporary spinal surgery, cement augmentation of fractured osteoporotic vertebrae in the form of vertebroplasty/kyphoplasty as well as cement augmentation of pedicle screws in instrumented procedures of any etiology are established as standard procedures. Both procedures are very effective, although the benefits of vertebroplasty/kyphoplasty procedures have been controversially discussed in the past. Overall, complications rarely occur. The most relevant complication is cement leakage, which is asymptomatic in the majority of cases but in the worst case might lead to neurological deficits, embolic events and even circulatory collapse. Prevention of cement leakage is therefore crucial. Risk factors for cement leakage and preventive measures are presented in a comprehensive review based on the available literature.

THE KEY RESEARCH OF SPORTS IN MAINTAINING HUMAN HEALTH

ABSTRACT Introduction One of the evaluation factors of human health is bone health, and an evaluation index of bone health is osteoporosis. Sports are an effective way to improve the human body. Objective The paper discusses the effects of different exercise intensities on human bone health. Methods The thesis selected 51 female college students, designed different exercise intensities of fitness running intervention programs, and conducted a 12-month exercise intervention. We divide female college students into three groups. The subjects’ bone mineral density (BMD), serum alkaline phosphatase (ALP), and serum osteocalcin (BGP) were tested before and after the experiment. Results The differences in femoral BMD, serum ALP, serum BGP, and lumbar spine BMD of the three groups of volunteers were significant (P<0.05), while the differences in ulna and radius BMD were not significant. Conclusions Sports can promote human bone health. At the same time, the effect of fitness running on human BMD is site-specific. Level of evidence II; Therapeutic studies - investigation of treatment results.

A Biomechanical Model for Testing Cage Subsidence in Spine Specimens with Osteopenia or Osteoporosis Under Permanent Maximum Load

BACKGROUND

Intervertebral fusions in cases of reduced bone density are a tough challenge. From a biomechanical point of view, most current studies have focused on the range of motion or have shown test setups for single-component tests. Definitive setups for biomechanical testing of the primary stability of a 360° fusion using a screw-rod system and cage on osteoporotic spine are missing. The aim of this study was to develop a test stand to provide information about the bone-implant interface under reproducible conditions.

METHODS

After pretesting with artificial bone, functional spine units were tested with 360° fusion in the transforaminal lumbar interbody fusion technique. The movement sequences were conducted in flexion/extension, right and left lateral bending, and right and left axial rotation on a human model with osteopenia or osteoporosis under permanent maximum load with 7.5 N-m.

RESULTS

During the testing of human cadavers, 4 vertebrae were fully tested and were inconspicuous even after radiological and macroscopic examination. One vertebra showed a subsidence of 2 mm, and 1 vertebra had a cage collapsed into the vertebra.

CONCLUSIONS

This setup is suitable for biomechanical testing of cyclical continuous loads on the spine with reduced bone quality or osteoporosis. The embedding method is stable and ensures a purely single-level setup with different trajectories, especially when using the cortical bone trajectory. Optical monitoring provides a very accurate indication of cage movement, which correlates with the macroscopic and radiological results.