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This study examined the ability of local alendronate (ALN) administration to control β‐tricalcium phosphate (β‐TCP) resorption as well as the induction of bone formation by recombinant human bone morphogenetic protein‐2 (rhBMP‐2). A 15‐mm critical‐sized bone defect was created in the diaphysis of rabbit ulnae. Nine female rabbits (4 to 5 months‐old) were divided into 3 groups. Group 1 (n = 6 ulnae) animals received implants consisting of β‐TCP granules and 25 μg of rhBMP‐2 in 6.5% collagen gel. Group 2 (6 ulnae) and Group 3 (6 ulnae) animals received the same implants, but with 10−6 M and 10−3 M ALN‐treated TCP granules, respectively. Two weeks postsurgery, tartrate‐resistant acid phosphatase‐positive cell counts, new bone formation, and residual β‐TCP were evaluated. This study showed that a high dose of ALN strongly reduced osteoclastic resorption of β‐TCP induced by rhBMP‐2, resulting in decreased bone formation. In contrast, a low dose of ALN slightly reduced the bone resorptive effect but increased bone formation. These results suggest that osteoclast‐mediated resorption plays an important role in bone formation and a coupling‐like phenomenon could occur in the β‐TCP‐implanted area, and that administration of a low dose of ALN may solve clinical bone resorptive problems induced by rhBMP‐2. [ABSTRACT FROM AUTHOR]

Following identification of peak height velocity (PHV) by a recent study as a possible prognostic factor for curve progression in patients with idiopathic scoliosis (IS), the aim of this study was to investigate PHV curves in Japanese female patients with IS. The study subjects were 20 skeletally immature IS patients who were followed until maturity. The mean age and the mean pubertal status at the initial visit were 9.8 years and 24 months before menarche, respectively, with a follow-up period of 5.2 years. Height measurements were recorded at each visit, and HV was calculated as the change in height (cm) divided by the time interval (yr.) between visits of 6 to 12 months. The PHV, age at PHV (APHV), height at PHV (HPHV), and final height (FH) were determined. Patient HV curves were plotted using their HV data, and growth periods (GPs) were calculated from the curves. PHVs and GPs of study patients were compared to standard data from unaffected girls. The median values and interquartile ranges in PHV, APHV, HPHV, and FH were 8.5 cm/yr. (7.9-9.7), 11.8 yr. (11.2-12.1), 153.2 cm (150.1-155.8), and 160.1 cm (157.4-162.4), respectively. The median GP was 27 months. The PHV and GP values in IS female patients were higher and shorter than those in unaffected girls. These findings indicate that the patterns of height velocity curves in IS patients are different from those in unaffected girls, suggesting that curve progression in IS patients is associated with the magnitude of PHV and duration of GP. Recently, we have developed an HV reader to easily and quickly identify the present HV in patients with scoliosis, applicable for the clinical setting or school screening. We conclude that risk assessments of curve progression in patients with IS should include HV along with measures of skeletal maturity such as the Risser sign and/or digital skeletal age using hand X-rays. [ABSTRACT FROM AUTHOR]

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., (Copyright 2009 Wiley Periodicals, Inc.)

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., ((c) 2007 Wiley Periodicals, Inc.)

To evaluate the ability of a biphasic construct to repair osteochondral defects in articular cartilage, plugs made of chondrocytes in collagen gel overlying a resorbable porous beta-tricalcium phosphate (TCP) block were implanted into defects in rabbit knees. The repair tissue was evaluated at 8, 12, and 30 weeks. Eight weeks after implantation of the biphasic construct, histologic examination showed hyaline-like cartilage formation that was positive for safranin O and type II collagen. At 12 weeks, most of the beta-TCP was replaced by bone, with a small amount remaining in the underlying cartilage. In the cell-seeded layer, the newly formed middle and deep cartilage adjacent to the subchondral bone stained with safranin O, but no staining was observed in the superficial layer. In addition, cell morphology was distinctly different from the deep levels of the reparative cartilage, with hypertrophic cells at the bottom of the cartilaginous layer. At 30 weeks, beta-TCP had completely resorbed and a tidemark was observed in some areas. In contrast, controls (defects filled with a beta-TCP block alone) showed no cartilage formation but instead had subchondral bone formation. These findings indicate that beta-TCP-supported chondrocytes in collagen gel can partially repair isolated articular cartilage osteochondral defects.

The objective of this study was to evaluate the effects of a complex of beta-tricalcium phosphate (beta-TCP) granules and 3.5% hyaluronate (beta-TCP granules-HY complex) compared with a beta-TCP block, in terms of osteoconductivity and biodegradability, to determine whether this complex would be a good candidate for bone void filler. Both materials were implanted into cavities drilled in rabbit femoral condyles. New bone formation and mineral apposition rate were evaluated to analyze osteoconductivity, whereas residual beta-TCP within the defects and tartrate-resistant acid phosphatase (TRAP) cellular activity were studied for beta-TCP resorption. The results show that both the beta-TCP block and the beta-TCP granules-HY complex support bone ingrowth; however, bioresorption was rapid for beta-TCP granules-HY but weak for beta-TCP block. This biodegradation mechanism was considered to be a cell-mediated disintegration by numerous TRAP-positive giant cells. The time lag between the peak value of TRAP-positive giant cell population and that of new bone formation rate suggests that a coupling-like phenomenon could be occurring in the beta-TCP-filled bone defects. In addition, beta-TCP granules-HY complex, which is an injectable, pastelike material, has similar osteoconductive properties to beta-TCP block. Thus, this complex may be useful as a bone filler in clinical application.