A number of microRNAs (miRNAs, miRs) have been shown to play a role in skeletal muscle atrophy, but their role is not completely understood. Here we show that miR-29b promotes skeletal muscle atrophy in response to different atrophic stimuli in cells and in mouse models. miR-29b promotes atrophy of myotubes differentiated from C2C12 or primary myoblasts, and conversely, its inhibition attenuates atrophy induced by dexamethasone (Dex), TNF-α and H₂O₂ treatment. Targeting of IGF-1 and PI3K(p85α) by miR-29b is required for induction of muscle atrophy. In vivo, miR-29b overexpression is sufficient to promote muscle atrophy while inhibition of miR-29b attenuates atrophy induced by denervation and immobilization. These data suggest that miR-29b contributes to multiple types of muscle atrophy via targeting of IGF-1 and PI3K(p85α), and that suppression of miR-29b may represent a therapeutic approach for muscle atrophy induced by different stimuli.

Facetectomy is an important intervention for spinal stenosis but may lead to spinal instability. Biomechanical knowledge for facetectomy can be beneficial when deciding whether fusion is necessary. Therefore, the aim of this study was to investigate the biomechanical effect of different grades of facetectomy. A three-dimensional nonlinear finite element model of L3–L5 was constructed. The mobility of the model and the intradiscal pressure (IDP) of L4-L5 for standing were inside the data from the literature. The effect of graded facetectomy on intervertebral rotation, IDP, facet joint forces, and maximum von Mises equivalent stresses in the annuli was analyzed under flexion, extension, left/right lateral bending, and left/right axial rotation. Compared with the intact model, under extension, unilateral facetectomy increased the range of intervertebral rotation (IVR) by 11.7% and IDP by 10.7%, while the bilateral facetectomy increased IVR by 40.7% and IDP by 23.6%. Under axial rotation, the unilateral facetectomy and the bilateral facetectomy increased the IVR by 101.3% and 354.3%, respectively, when turned to the right and by 1.1% and 265.3%, respectively, when turned to the left. The results conclude that, after unilateral and bilateral facetectomy, care must be taken when placing the spine into extension and axial rotation posture from the biomechanical point of view.

The purpose was to explore possible risk factors of facet joint violation induced by adjacent superior vertebral pedicle screw during the minimally invasive surgery transforaminal lumbar interbody fusion (MIS-TLIF). A total of 69 patients with lumbar degenerative disease, who underwent MIS-TLIF were retrospectively reviewed. Postoperative computed tomography images were used to assess the facet joint violation. The correlation of facet joint violations with gender, age, body mass index (BMI), the adjacent superior vertebral level, fusion segment numbers, position of screw insertion, straight leg-raising test (SLRT) results, clinical diseases and renal dysfunction were analyzed by Chi-square tests and binary logistic regression analysis. The incidence of adjacent superior facet joint violations was 25.4 %. Chi-square test showed the patients with age <60 and high BMI (≥30 kg/m2) were more prone to have facet joint violations (P = 0.007; P = 0.006). The single segment fusion presented more facet joint violations than the double segments fusion (P = 0.048). The vertebral pedicle screw implant location at L5 showed more facet joint violations compared with that at L3 and L4 (P = 0.035). No correlation was found between gender, screw implant position, SLRT results, clinical diseases and renal dysfunction and facet joint violations. Logistic regression analysis revealed that age <60 years (OR: 2.902; 95 % CI 1.227–6.864; P = 0.015) and BMI ≥30 kg/m2 (OR: 2.825; 95 % CI 1.191–6.700; P = 0.018 < 0.05) were significantly associated with facet joint violation. These results found a high incidence of adjacent superior vertebral facet joint violation in the MIS-TLIF. Age <60 and BMI ≥30 kg/m2 might be risk factors of facet joint violation. Evidence level: Level 4.