Objective To study the effects of early mechanical strain magnitude on formation and differentiation of osteoclasts. Methods RAW 264.7 cells induced by macrophage colony-stimulating factors and osteoclast differentiation factors were subjected to 0, 1 000, 1 500, 2 000, 2 500 and 5 000 με mechanical straining for three days. The morphological changes, number of osteoclasts and proliferation of precursor cells were determined at day 7. The activity of the tartrate-reaistant acid phosphatase (TRAP) in the culture medium was detected at days 4 and 7. Results The number of osteoclasts was decreased in 2 500 με group, while it was increased in 5 000 με group. The proliferation of precursor cells was increased in 2 000 and 2 500 με group, while it was decreased significantly in 5 000 με group. There was no significant difference in the number of osteoclasts and proliferation of precursor cells among 1 000 με group, 1 500 με group and 0 με group. The activity of TRAP was decreased in 1 000, 1 500, 2 000, 2500 and 5 000 με groups at days 4 and 7 when compared with με group. Conclusions Early mechanical straining plays a direct role in formation and differentiation of osteoclasts. The high strain magnitude within physiological load inhibits osteoclast formation, while high strain magnitude beyond physiological load stimulates osteoclast formation. Low strain magnitude has nearly no impact on formation of osteoclasts. Early mechanical straining may inhibit differentiation of osteoclasts.

OBJECTIVETo explore the reasons for the complications of polyacrylamide hydrogel injection.

METHODS39 patients were included in this study, who had complications after polyacrylamide hydrogel injection in the breasts, nose, temproal area or depressed locus. The clinical manifestations of the complications were analyzed.

RESULTSPostoperative infection occurred in 5 cases, induration in 23, pain in 25, ulceration of the puncture points in 9, displacement in 6, galactostasis in 1, skin necrosis in 1, breast deformation in 3, bilateral asymmetry in 4, aseptic inflammation in 10, and skin-acne-like changes on the face in 4.

CONCLUSIONSome complications were caused mainly by incorrect manipulation and others were relative to the injected material. The applications of polyacrylamide hydrogel as a clinical implant material need further investigations. Polyacrylamide hydrogel injection should be cautiously used.

Acrylic Resins ; adverse effects ; Adult ; Bacterial Infections ; etiology ; Female ; Humans ; Injections ; Middle Aged ; Pain, Postoperative ; etiology ; Postoperative Complications ; Surgery, Plastic ; adverse effects