No abstract

In this study, articular cartilage was decellularized preserving a majority of the inherent proteins, cytokines, growth factors and sGAGs. The decellularized cartilage matrix (dCM) was then encapsulated in poly(lactic acid) microspheres (MS+dCM) via double emulsion. Blank microspheres without dCM, MS(-), were also produced. The microspheres were spherical in shape and protein encapsulation efficiency within MS+dCM was 63.4%. The sustained release of proteins from MS+dCM was observed over 4 weeks in vitro. Both MS+dCM and MS(-) were cytocompatible. The sustained delivery of retained growth factors and cytokines from MS+dCM promoted cell migration in contrast to MS(-). Subsequently, chondrogenesis of hMSCs was upregulated in presence of MS+dCM as evidenced from immunohistochemistry, biochemical quantification and qPCR studies. Specifically, collagen II, aggrecan and SOX 9 gene expression were increased in the presence of MS+dCM by an order or more in magnitude compared to MS(-) with concomitant downregulation of hypertrophic genes (COL X) despite being cultured in the absence of chondrogenic media, (p<0.05). Lastly, microspheres containing alkaline phosphatase (MS+ALP), a surrogate to assess the thermal stability of dCM proteins, incorporated within poly(caprolactone) filaments showed that the enzyme remained functional after filament production by melt extrusion. The establishment of a novel, thermally stable process for producing filaments containing chondroinductive microspheres provides evidence supporting subsequent development of a clinically-relevant, 3D scaffold fabricated from them for osteochondral regeneration and repair.

No abstract

No abstract

Sufficient stabilization of comminuted mid-shaft clavicle fractures via plate fixation is difficult to achieve. Various augmentations, including interfragmentary screws and cerclage wiring, have been adopted to reinforce fixation stability. The present study aimed to assess the biomechanical stability of augmented plate fixations using the finite element method. First, a clavicle fracture model was created from CT data. Fixation was then induced using a locking compressive plate (LCP) with the following four augmentations: i) Double inner cerclage wirings (DICW), ii) double outer cerclage wirings (DOCW), iii) a single interfragmentary screw (SIS) and iv) double interfragmentary screws (DIS). Compressive and bending forces of 100 N were subsequently applied at the acromial region of the clavicle. The stress distribution, displacement and fracture micro-motions of the model were assessed and compared. The DOCW resulted in the highest stress exerted on the LCP, followed by SIS, DICW and DIS. For the clavicle fracture, DICW, DOCW and SIS resulted in high stress levels. However, DIS fixation alone resulted in levels of stress that were below the yield strength of cortical bone. Displacement analysis revealed that DOCW fixation resulted in the greatest degree of displacement and fracture micro-motions, followed by SIS, DICW and DIS. The results indicated that SIS, DIS and DOCW may be used as augmentations of LCP fixation for comminuted mid-shaft clavicle fractures. However, DIS was the recommended augmentation due to it exerting the lowest stress and the highest stability compared with the other fixations. The DICW may be used to aid fracture reduction and plate placement in surgery but should be avoided for permanent fixation.