Critical-size bone defects are an important problem in clinical practice, which usually occurs in severe trauma, or tumor resection, and cannot heal completely and autonomously. Implantation of grafts is often required to promote the regeneration of critical-size bone defects. Metal ions play an important role in human health, as they affect the body's metabolism and the tissue function. Strontium ions (Sr 2+ ) can promote osteogenesis and angiogenesis. Herein, we prepared nano-hydroxyapatite (nHA)/ chitosan (CS) composite microspheres with a uniform particle size distribution and an extracellular matrix-like nanofiber structure using microfluidic technology and direct alkali-induced gelation. Strontium ions were stably added into the microspheres by using polydopamine (PDA) to chelate metal ions forming a bone repair material (nHA/CS@PDA-Sr) with good bioactivity. The coordination reaction of PDA can effectively control the release of strontium ions and avoid the negative effects caused by the high strontium concentration. Our in vitro experiments showed that the composite microspheres had good biocompatibility and that the PDA coating promotes cell adhesion. The slow release of strontium ions can effectively promote mesenchymal stem cells osteogenic differentiation and the vascularization of endothelial cells. In addition, we injected composite microspheres into cranial defects of rats to evaluate osseointegration in vivo. The results showed that nHA/CS@PDA-Sr could effectively promote bone regeneration in the defect area. This study demonstrates that composite microspheres stimulate bone repair providing a promising way for bone-defect regeneration.
ObjectiveTo investigate the variation of pelvic radius and related parameters in low-grade isthmic lumbar spondylolisthesis.MethodsSeventy-four patients with isthmic lumbar spondylolisthesis and 47 controls were included in this study. There were 17 males and 57 females between 30 and 66 years of age, including 30 with grade I slippages and 44 grade II slippages; diseased levels included 34 cases on L4 and 40 cases on L5. Thoracic kyphosis (TK), the pelvic radius (PR), the pelvic angle (PA), pelvic morphology (PR-S1), and total lumbopelvic lordosis (PR-T12) were assessed from radiographs.ResultsStatistically significant differences were found for the PA, PR-T12, and PR-S1 (24.5±6.6°, 83.7±9.8°, and 25.4±11.2°, respectively) of the patients with spondylolisthesis and the healthy volunteers (13.7±7.8°, 92.9±9.2°, and 40.7±8.9°, respectively). The TK/PR-T12 ratios were between 0.15 and 0.75. However, there were no differences in all the parameters between the L4 and L5 spondylolysis subgroups (p>0.05). The TK and PR-S1 of grade II were less than grade I, but the PA was greater. The PR-T12 of female patients were less than male patients, but the PA was greater (p<0.05).ConclusionPelvic morphology differed in patients with low-grade isthmic lumbar spondylolisthesis compared to controls. Gender and the grade of slippage impacted the sagittal configuration of the pelvis, but the segment of the vertebral slip did not. Overall, the spine of those with spondylolisthesis remains able to maintain sagittal balance despite abnormal pelvic morphology.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.