Compared with non-degradable materials, biodegradable biomaterials play an increasingly important role in the repairing of severe bone defects, and have attracted extensive attention from researchers. In the treatment of bone defects, scaffolds made of biodegradable materials can provide a crawling bridge for new bone tissue in the gap and a platform for cells and growth factors to play a physiological role, which will eventually be degraded and absorbed in the body and be replaced by the new bone tissue. Traditional biodegradable materials include polymers, ceramics and metals, which have been used in bone defect repairing for many years. Although these materials have more or fewer shortcomings, they are still the cornerstone of our development of a new generation of degradable materials. With the rapid development of modern science and technology, in the twenty-first century, more and more kinds of new biodegradable materials emerge in endlessly, such as new intelligent micro-nano materials and cell-based products. At the same time, there are many new fabrication technologies of improving biodegradable materials, such as modular fabrication, 3D and 4D printing, interface reinforcement and nanotechnology. This review will introduce various kinds of biodegradable materials commonly used in bone defect repairing, especially the newly emerging materials and their fabrication technology in recent years, and look forward to the future research direction, hoping to provide researchers in the field with some inspiration and reference.

Intraarticular CS is more effective on pain relief than intraarticular HA in short term (up to 1 month), while HA is more effective in long term (up to 6 months). Two therapies benefit similarly for knee function improvement. Both two methods are relatively safe, but intraarticular HA causes more topical adverse effects compared with intraarticular CS.

Purpose: Glucocorticoid-induced osteonecrosis of the femoral head (GIONFH) is a common disease after long-term or high-dose glucocorticoid use. The pathogenesis of GIONFH is still controversial, and abnormal bone metabolism caused by glucocorticoids may be one of the important factors. Exosomes, owing to their positive effect on bone repair, show promising therapeutic effects on bone-related diseases. In this study, we hypothesised that exosomes reduce osteocyte apoptosis in rat GIONFH via the miR-21-PTEN-AKT signalling pathway.Methods: To evaluate the effects of exosomes in GIONFH, a dexamethasone-treated or exosome-treated in vitro cell model and a methylprednisolone-treated in vivo rat model were set up. In vitro, a CCK-8 assay and 5-ethynyl-2′-deoxyuridine staining were performed to evaluate the proliferation of osteocytes. Further, a terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay, annexin V-fluorescein isothiocyanate-propidium iodide staining, and western blotting were conducted to evaluate the apoptosis of osteocytes. In vivo, we used micro-computed tomography and histological and immunohistochemical analyses to assess the effects of exosomes. Moreover, the mechanism of exosome action on osteocyte apoptosis through the miR-21-PTEN-AKT pathway was investigated by high-throughput RNA sequencing, fluorescence in situ hybridisation, luciferase reporter assays, and western blotting.Results: High-throughput RNA sequencing results showed that the AKT signalling pathway was up-regulated in the exosome group. Quantitative PCR and western blotting confirmed that the relative expression of genes in the AKT pathway was up-regulated. Western blotting revealed that AKT activated by exosomes inhibited osteocyte apoptosis. RNA fluorescence in situ hybridisation and luciferase reporter assays were performed to confirm the interaction between miR-21 and PTEN. According to the experiment in vivo, exosomes prevented GIONFH in a rat model as evidenced by micro-computed tomography scanning and histological and immunohistochemical analyses.Conclusions: Exosomes are effective at inhibiting osteocyte apoptosis (in MLO-Y4 cells) and at preventing rat GIONFH. These beneficial effects are mediated by the miR-21-PTEN-AKT signalling pathway.

Objective To assess the safety and efficacy of balloon kyphoplasty (KP) compared with percutaneous vertebroplasty (VP) and provide recommendations for using these procedures to treat osteoporotic vertebral compression fractures (OVCF). Methods A systematic search of all studies published through March 2012 was conducted using the MEDLINE, EMBASE, OVID, ScienceDirect and Cochrane CENTRAL databases. The randomized controlled trials (RCTs) and non-randomized controlled trials that compared KP to VP and provided data on safety and clinical effects were identified. Demographic characteristics, adverse events and clinical outcomes were manually extracted from all of the selected studies. The evidence quality levels and recommendations were assessed using the GRADE system. Results Twelve studies encompassing 1,081 patients met the inclusion criteria. Subgroup meta-analyses were performed according to the study design. In the RCT subgroup, there were significant differences between the two procedures in short-term visual analog scale (VAS), long-term kyphosis angles, operative times and anterior vertebrae heights. In the cohort study subgroup, there were significant differences between the two procedures in short-and longterm VAS, short-and long-term Oswestry Disability Index (ODI), cement leakage rates, short-and long-term kyphosis angles, operative times and anterior vertebrae heights. However, there were no significant differences in long-term VAS or adjacent vertebral fracture rates in the RCT subgroup. There were no significant differences in short-or long-term VAS, short-or long-term ODI, cement leakage rates, adjacent vertebral fracture rates, short-or long-term kyphosis angles or anterior vertebrae heights in the CCT subgroup, and the adjacent vertebral fracture rates did not differ significantly in the cohort study subgroup. The overall GRADE system evidence quality was very low, which lowers our confidence in their recommendations. Conclusions KP and VP are both safe and effective surgical procedures for treating OVCF. KP may be superior to VP in patients with large kyphosis angles, vertebral fissures, fractures in the posterior edge of the vertebral body or significant height loss in the fractured vertebrae. Due to the poor quality of the evidence currently available, highquality RCTs are required.

Objective To identify the independent risk factors, based on available evidence in the literature, for patients developing surgical site infections (SSI) after spinal surgery. Methods Non-interventional studies evaluating the independent risk factors for patients developing SSI following spinal surgery were searched in Medline, Embase, Sciencedirect and OVID. The quality of the included studies was assessed by a modified quality assessment tool that had been previously designed for observational studies. The effects of studies were combined with the study quality score using a best-evidence synthesis model. Results Thirty-six observational studies involving 2,439 patients with SSI after spinal surgery were identified. The included studies covered a wide range of indications and surgical procedures. These articles were published between 1998 and 2012. According to the quality assessment criteria for included studies, 15 studies were deemed to be high-quality studies, 5 were moderate-quality studies, and 16 were low-quality studies. A total of 46 independent factors were evaluated for risk of SSI. There was strong evidence for six factors, including obesity/BMI, longer operation times, diabetes, smoking, history of previous SSI and type of surgical procedure. We also identified 8 moderate-evidence, 31 limited-evidence and 1 conflictingevidence factors. Conclusion Although there is no conclusive evidence for why postoperative SSI occurs, these data provide evidence to guide clinicians in admitting patients who will have spinal operations and to choose an optimal prophylactic strategy. Further research is still required to evaluate the effects of these above risk factors.

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