In order to evaluate the ability of fibrochondrocytes to synthesize collagen and proteoglycan, human medial meniscal cells were cultured in a monolayer. Meniscal cells were prepared from the two regions (outer 1/3 and inner 2/3) in consideration of the difference in vascular supply, and articular chondrocytes were also obtained from the same knee joint. Regarding total collagen synthesis, regional differences were not found, but age-related differences were found in human medial meniscus. In contrast, proteoglycan synthesis revealed significant regional differences; meniscal cells from the inner 2/3 synthesized a greater amount of proteoglycan. After long-term monolayer culturing, proteoglycan synthesis by meniscal cells decreased in a time-dependent manner, and morphological changes to fibroblast-like cells were found. In the presence of transforming growth factor (TGF)-beta, proteoglycan synthesis increased in a dose-dependent manner. These findings suggest that the inner regions of the human meniscus contain cells with a chondrocytic phenotype.

Although our cervical spine CT data were suggestive of possible ethnic differences in spinal canal morphology, our analysis failed to identify significant ethnic disparity in pedicle dimensions despite potential differences in physique between populations.

Most of the implanted porous beta-tricalcium phosphate (beta-TCP) can be resorbed. However, beta-TCP block with 75% porosity is inadequate for weight-bearing sites until bone incorporation occurs. Thus, the authors have recently developed beta-TCP block with 60% porosity, which is approximately sevenfold greater in terms of compressive strength than that of beta-TCP with 75% porosity. The authors investigated bone formation and resorption of beta-TCP after implantation in patients of beta-TCP blocks with two different porosities. From May 2003 to November 2004, medial opening high tibial osteotomy was performed in 25 patients with a mean age of 66 years. The opened defect was fixed with a Puddu plate. Then 6-8 cm(3) of beta-TCP block with 75% porosity was used to fill the cancellous bone defect, except on the medial side where 2.83-3.18 cm(3) of wedge-shaped beta-TCP block with 60% porosity was implanted. At least 2 years after surgery, the 25 patients had no correction loss, and bone formation was noted in all cases. Complete or nearly complete resorption of beta-TCP with 60 and 75% porosity was obtained within 3.5 years. Thirteen biopsy samples obtained from the 60% porosity implantation sites showed good lamellar bone formation, and the percentage of beta-TCP remaining relative to the newly formed bone plus beta-TCP ranged from 0.3 to 14.5%, with a mean of 6.7%. The authors suspect that mechanical stress loading to the medial side of the tibia facilitated bone formation and resorption of beta-TCP with 60% porosity.

The aim of this study was to determine the effects of alendronate (ALN) on osteoclastic resorption of beta-tricalcium phosphate (beta-TCP) and bone formation. beta-TCP blocks of 75% porosity, with or without ALN treatment, were implanted into cavities drilled in rabbit femoral condyles. New bone formation, residual amount of beta-TCP, and the number of tartrate-resistant acid phosphatase-positive cells were evaluated 2 weeks after surgery. The results show that local application of ALN at a concentration of 10(-2) to 10(-6)M reduced the number of osteoclasts on the surface of beta-TCP. New bone formation was also inhibited by ALN in a dose-dependent manner. Thus, inhibition of osteoclast formation resulted in reduced beta-TCP resorption and bone formation. These results suggest that osteoclast-mediated resorption plays an important role in bone formation and a coupling-like phenomenon could occur in beta-TCP-filled bone defects.