Altered mechano-chemical environment in hip articular cartilage: effect of obesity

Finite element analysis of two-level discontinuous cervical hybrid revision surgery strategy to reduce biomechanical responses of adjacent segments

Background

Hybrid surgery (HS) combined cervical disc arthroplasty (CDA) with anterior cervical discectomy and fusion (ACDF) is emerging, but its biomechanical effects as a revision surgery (RS) on adjacent segments were unclear.

Objectives

This finite element (FE) study aimed to investigate the biomechanical characteristics of HS to treat two-level discontinuous ASD in ACDF RS.

Methods

A C2-T1 intact FE model was established and modified to a primary C5/6 ACDF model and five RS models. These RS models' segments C4/5 and C6/7 were revised using cage plus plate (C), zero-profile devices (P), and Bryan disc (D), respectively, generating C-C-C, P-C-P, D-C-P, P-C-D, and D-C-D models. In the intact and C5/6 ACDF models, a 1.0 Nm moment was used to produce the range of motion (ROM). A displacement load was applied to all RS models, to achieve a total ROM match that of the primary C5/6 ACDF model.

Results

In the P-C-P model, biomechanical responses including ROM, Intradiscal pressure (IDP), Facet joint force (FJF), and Maximum von Mises stresses of discs at segments C3/4 and C7/T1 were slightly lower than the C-C-C model. The biomechanical response parameters at segments C3/4 and C7/T1 of P-C-D, D-C-P, and D-C-D were smaller than those in C-C-C and P-C-P models. D-C-D had the most significant effect on reducing all biomechanical responses among all RS models in segments C3/4 and C7/T1. Moreover, the disc stress cloud maps showed that the maximum von Mises stress of the C3/4 disc was higher than that of C7/T1.

Conclusions

D-C-D, P-C-D, and D-C-P are good RS choices for reducing the biomechanical responses, and D-C-D was the best choice. P-C-P can be the best recommendation when it does not meet the CDA indications. This study provided a biomechanical reference for hybrid surgical decision-making in the ACDF RS for preventing ASD recurrence.

Biomechanical study between percutaneous vertebroplasty combined with cement pedicle plasty improves vertebral biomechanical stability: A finite element analysis

OBJECTIVE

To investigate the biomechanical effects of percutaneous vertebroplasty combined with cement pedicle plasty (PVCPP) on the unstable osteoporotic vertebral fractures (OVFs) through finite element (FE) analysis. The study compares the biomechanical stability of finite element models between percutaneous vertebroplasty (PVP) and percutaneous vertebroplasty combined with cement pedicle plasty.

METHODS

Two patients with unstable OVFs underwent computed tomography (CT) examination at the thoracolumbar vertebral body levels, respectively. The CT images were reconstructed into three-dimensional finite element models to simulate stress conditions across six dimensions and to evaluate the vertebral von Mises stress before and after bone cement reinforcement.

RESULTS

The study found that stress distribution differed between groups mainly at the pedicle base. In the surgical vertebral bodies, the maximum stress in the PVP group decreased during flexion and left bending, while it increased in other states. In the PVCPP group, all maximum stresses decreased. In the inferior vertebral bodies, the maximum stress in the PVP group generally increased, while it decreased in the PVCPP group. In the superior vertebral bodies, postoperatively, the maximum stress in the PVP group generally increased, while it almost remained unchanged in the PVCPP group. PVP group had higher cement stress and displacement.

CONCLUSION

PVCPP is an effective treatment method for patients with unstable OVFs. It can quickly relieve pain and enhance the stability of the three columns, thereby reducing the risk of some complications.

Smart Shoe Insole Based on Polydimethylsiloxane Composite Capacitive Sensors

Nowadays, the study of the gait by analyzing the distribution of plantar pressure is a well-established technique. The use of intelligent insoles allows real-time monitoring of the user. Thus, collecting and analyzing information is a more accurate process than consultations in so-called gait laboratories. Most of the previous published studies consider the composition and operation of these insoles based on resistive sensors. However, the use of capacitive sensors could provide better results, in terms of linear behavior under the pressure exerted. This behavior depends on the properties of the dielectric used. In this work, the design and implementation of an intelligent plantar insole composed of capacitive sensors is proposed. The dielectric used is a polydimethylsiloxane (PDMS)-based composition. The sensorized plantar insole developed achieves its purpose as a tool for collecting pressure in different areas of the sole of the foot. The fundamentals and details of the composition, manufacture, and implementation of the insole and the system used to collect data, as well as the data samples, are shown. Finally, a comparison of the behavior of both insoles, resistive and capacitive sensor-equipped, is made. The prototype presented lays the foundation for the development of a tool to support the diagnosis of gait abnormalities.

Microarray analysis of the molecular mechanisms associated with age and body mass index in human meniscal injury

The aim of the present study was to identify genes and functional pathways associated with meniscal injuries affected by age or body mass index (BMI) using microarray analysis. The GSE45233 gene expression dataset with 12 injured meniscus samples associated with age and BMI and GSE66635 dataset with 12 injured and 12 normal meniscus samples were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were identified based on age or BMI in GSE45233. DEGs between injured and normal meniscus samples in GSE66635 were also identified. Common DEGs between GSE45233 and GSE66635 were identified as feature genes associated with age or BMI, followed by protein-protein interaction (PPI) network and functional pathway enrichment analyses for the feature genes. Finally, the GSE51588 genome-wide expression profile was then downloaded from the GEO database to validate the results. A total of 1,328 DEGs were identified. Of these, 28 age-associated and 20 BMI-associated meniscal injury genes were obtained. B-cell lymphoma-2 (Bcl-2) and matrix metalloproteinase-14 were identified as hub genes in the PPI networks. Functional pathway enrichment analysis revealed that vascular endothelial growth factor A (VEGFA), transferrin (TF) and Bcl-2 were involved in the hypoxia-inducible factor 1 signaling pathway. TF was involved in the mineral absorption function pathway associated with BMI. Additionally, TF and VEGFA were identified to be overlapping candidate genes of GSE45233 and GSE66635, and DEGs in GSE51588. Therefore, VEGFA, TF, and Bcl-2 may be important genes for human meniscal injuries. Additional evaluations of these results are required.

Obesity and Knee Arthroscopy – a Review

Obesity is currently a global epidemic, often referred to as “globesity”, impacting the life of millions worldwide. A risk factor for many diseases, obesity can also be linked to developing intra-articular lesions of the knee, affecting the menisci, ligaments and cartilage. Furthermore, obesity has been shown to influence the outcome of surgical interventions, including those of the musculoskeletal system. Although many studies addressed the relationship of obesity and joint replacement, articles relating to arthroscopy and obesity, and knee arthroscopy in particular, are a bit scarcer. The majority of data suggest that an increase in BMI leads to a similar increase in the rates of intra- and postoperative complications, and most authors agree that a higher body mass index can influence both the procedure itself and its outcomes, including the subjective results reported by the patients. Still, some studies show different results, especially in patients that are overweight or with low-grade obesity, where the outcomes are comparable to those of the non-obese population. Thus, it can be concluded that obesity is an important patient characteristic that needs to be taken into consideration when planning, performing, and assessing the results of knee arthroscopy.

Effects of Tobacco Smoking on the Degeneration of the Intervertebral Disc: A Finite Element Study

Tobacco smoking is associated with numerous pathological conditions. Compelling experimental evidence associates smoking to the degeneration of the intervertebral disc (IVD). In particular, it has been shown that nicotine down-regulates both the proliferation rate and glycosaminoglycan (GAG) biosynthesis of disc cells. Moreover, tobacco smoking causes the constriction of the vascular network surrounding the IVD, thus reducing the exchange of nutrients and anabolic agents from the blood vessels to the disc. It has been hypothesized that both nicotine presence in the IVD and the reduced solute exchange are responsible for the degeneration of the disc due to tobacco smoking, but their effects on tissue homeostasis have never been quantified. In this study, a previously presented computational model describing the homeostasis of the IVD was deployed to investigate the effects of impaired solute supply and nicotine-mediated down-regulation of cell proliferation and biosynthetic activity on the health of the disc. We found that the nicotine-mediated down-regulation of cell anabolism mostly affected the GAG concentration at the cartilage endplate, reducing it up to 65% of the value attained in normal physiological conditions. In contrast, the reduction of solutes exchange between blood vessels and disc tissue mostly affected the nucleus pulposus, whose cell density and GAG levels were reduced up to 50% of their normal physiological levels. The effectiveness of quitting smoking on the regeneration of a degenerated IVD was also investigated, and showed to have limited benefit on the health of the disc. A cell-based therapy in conjunction with smoke cessation provided significant improvements in disc health, suggesting that, besides quitting smoking, additional treatments should be implemented in the attempt to recover the health of an IVD degenerated by tobacco smoking.