Degradation and osteogenic potential of a novel poly(lactic acid)/nano-sized ß-tricalcium phosphate scaffold.

The purpose of this study was to investigate the influence of nano-sized ß-tricalcium phosphate (ß-TCP) on the biological performance of poly (lactic acid) (PLA) composite scaffolds by using in vitro degradation and an in vivo model of heterotopic bone formation. Nano-sized ß-TCP (nß-TCP) was prepared with a wet grinding method from micro-sized ß-TCP (mß-TCP), and composite scaffolds containing 0, 10, 30, or 50 wt% nß-TCP or 30 wt% mß-TCP were generated using a freeze-drying method. Degradation was assessed by monitoring changes in microstructure, pH, weight, and compressive strength over a 26-week period of hydrolysis. Composite scaffolds were processed into blocks, and implanted into muscular pockets of rabbits after loading with recombinant human bone morphogenetic protein-2 (rhBMP-2). New bone formation was evaluated based on histological and immunohistochemical analysis 2, 4, and 8 weeks after implantation. The in vitro results indicated that the buffering effect of nß-TCP was stronger than mß-TCP, which was positively correlated with the content of nß-TCP. The in vivo findings demonstrated that nß-TCP enhanced the osteoconductivity of the scaffolds. Although composite scaffolds containing 30% nß-TCP exhibited similar osteoconductivity to 50% nß-TCP, they had better mechanical properties than the 50% nß-TCP scaffolds. This study supports the potential application of a composite scaffold containing 30% nß-TCP as a promising scaffold for bone regeneration.

[Percutaneous plate fixation of three and four-part proximal humerus fractures in elderly patients].

OBJECTIVE: To evaluate the treatment effect of three and four-part fractures of proximal humerus in elder patients using indirect reduction combined with locking proximal humeral plate (LPHP) fixation. METHODS: From November 2004 to May 2008, 24 cases of proximal humeral three and four-part fracture were treated with percutaneous plate fixation using LPHP included 6 males and 18 females with an average age of 70 years old ranging from 55 to 88 years. The surgery was performed through antrolateral transdeoltoid approach. After extra articular capsule indirect reduction, the plate was inserted through the incision, and then an incision was made distal to previous incision to expose distal plate. The proximal fragments were fixed with 4 to 6 screws, and distal fragments were fixed with 3 screws. Shoulder exercises were performed at the 2nd to 3rd day after operation. Two weeks after operation, active shoulder exercise was done, which was gradually intensified 3 weeks after operation. The functional outcomes of the shoulder were assessed according to Constant score. RESULTS: All the fractures united clinically and radiologically. The mean healing time was 10.5 weeks (8 to 21 weeks). The mean Constant score was 81.6 points (49 to 92 points). A total of 20 patients had excellent or satisfactory result, with only one scored as poor. CONCLUSION: The technique of extra articular capsule indirect reduction combined LPHP internal fixation has the advantages of stable, easy to operate, less vascular damage and so on. It can effectively treat the proximal humerus three-and four-part fractures, especially to elder patients.