Yoshinori Gonda

The slow resorption with replacement by bone of a hydrothermally synthesized pure calcium-deficient hydroxyapatite

A newly developed calcium-deficient hydroxyapatite composed of rod-shaped particles synthesized by the hydrothermal method (HHA) and stoichiometric hydroxyapatite (SHA) synthesized by the sintering method was used for in vivo implantation and in vitro culture systems to compare these biological responses. In the rabbit femur, implanted HHA was slowly resorbed and about 80% of the implant remained 24 weeks after implantation; however, up to 72 weeks after implantation, most of the implanted HHA was resorbed. The implanted SHA was unresorbed throughout the experimental period, but degradation by the invasion of newly formed bone was seen at 72 weeks after implantation. Bone histomorphometry showed that the volume of newly formed bone and the number of osteoclasts in the implanted region were significantly higher in HHA than in SHA 24 weeks after implantation. In vitro culture of C2C12 cells with the induction of osteoblastic phenotypes using recombinant bone morphogenetic protein-2 showed similar cell density and the induction of alkaline phosphatase activity between the cells on HHA and SHA discs. In vitro osteoclastogenesis of HHA and SHA discs using bone marrow macrophages and recombinant receptor activator of nuclear factor-kappaB ligand showed higher TRAP activity of osteoclasts cultured on HHA discs. These results showed that slow biodegradability did not always correlate to final replaceability in bone tissue, and suggested that the activity of osteoclasts correlated to the bone-forming activity of osteoblasts.

Stimulatory effect of hydrothermally synthesized biodegradable hydroxyapatite granules on osteogenesis and direct association with osteoclasts

Calcium-deficient hydroxyapatite (HA) granules with a unique spherical shape were prepared using an applied hydrothermal method. Spherical stoichiometric HA granules were also prepared by normal sintering and both granules were used for implantation into rat tibiae to compare the biological responses to each implant. Twelve and 24 weeks after implantation, the volume of calcium-deficient HA granules was significantly less than that of stoichiometric HA granules, and the biodegradability of calcium-deficient HA granules was confirmed. The larger number of osteoclasts, larger osteoblast surface and larger bone volume in the implanted area of calcium-deficient HA than those of stoichiometric HA suggested that osteoclastic resorption of calcium-deficient HA affected osteogenesis in that area. To analyze the direct contribution of osteoclasts to osteogenesis, C2C12 multipotent myoblastic cells, which have the potential to differentiate into osteoblasts in the presence of bone morphogenetic protein 2, were cultured with supernatants of osteoclasts cultured on calcium-deficient HA, stoichiometric HA, beta-tricalcium phosphate disks or plastic dishes, or bone marrow macrophages cultured on plastic dishes. Supernatants of osteoclasts but not bone marrow macrophages stimulated the expression of Runx2 and osteocalcin in C2C12 cells in concert with bone morphogenetic protein 2. The expression of alkaline phosphatase was stimulated with supernatants of osteoclasts cultured on ceramic disks. These results suggested that osteoclasts produced certain soluble factors which stimulated osteoblastic differentiation and they were thought to be associated with the induction of a larger osteoblast surface and bone volume in the animals implanted with calcium-deficient HA granules.

Promotion of normal healing of bone defects under estrogen deficiency by implantation of beta-tricalcium phosphate composed of rod-shaped particles

We compared the healing of bone defects in ovariectomized rats implanted with beta‐tricalcium phosphate (β‐TCP) composed of rod‐shaped particles, which were prepared using the applied hydrothermal method (HTCP), and that of bone defects implanted with conventional β‐TCP composed of globular‐shaped particles (CTCP), which were prepared by normal sintering. Eight‐week‐old female Wistar rats were ovariectomized, and 2 weeks after the operation, 0.5‐ to 0.6‐mm diameter spherical granules of each ceramic were implanted in a bone defect created in the distal end of the femur. Four, 8, and 12 weeks after implantation, the amount of newly formed bone implanted with HTCP was significantly larger than that implanted with CTCP and was equivalent to that in non‐ovariectomized sham‐operated rats. Without implantation, spontaneous repair of the trabecular bone was barely observed. The physiological structure of the trabecular network was maintained in the region implanted with HTCP, but that in the region implanted with CTCP was severely destroyed. Gene expression microarray analysis revealed that the expression of genes involved in interferon signaling pathways was upregulated in osteoclasts cultured on HTCP compared with that cultured on CTCP. Our results suggest that the microstructure of β‐TCP affected the biological behavior of osteoclasts and regulated local bone metabolism.

Application of Newly Developed Globular-Shaped Granules of β-Tricalcium Phosphate for Bone Substitute

Globular-shaped beta-tricalcium phosphate (β-TCP) granules were synthesized using a unique dropping slurry method and the biological response was analyzed by implantation into the rat femur. Two kinds of globular-shaped β-TCP granules, composed of either rod-shaped particles or conventional non-rod-shaped particles were synthesized, implanted into the left femurs of 8-week-old female Wistar rats, and analyzed histologically. Commercially available β-TCP granules composed of conventional non-rod-shaped particles were also implanted as a control experiment. Four weeks after the operation, part of each implant was already resorbed and the resorbed area was replaced by newly formed bone tissue and bone marrow. Eight weeks after the operation, the resorption and replacement were advanced in each implant. At 12 weeks after the operation, residual globular-shaped β-TCP granules composed of rod-shaped particles were resorbed into compact petrotic bone tissue almost completely. The formation of less compact petrotic bone tissue was observed in specimens implanted with globular-shaped β-TCP granules composed of conventional non-rod-shaped particles. Commercially available β-TCP granules composed of conventional non-rod-shaped particles were mostly resorbed into trabecular bone and the formation of compact petrotic bone tissue was rarely observed. These data suggested that both the unique spherical shape and microstructure of β-TCP particles affected bone-forming activity after the operation.

Stimulation of Osteogenesis in Bone Defects Implanted with Biodegradable Hydroxyapatite Composed of Rod-Shaped Particles under Mechanical Unloading.

The aim of this study was to evaluate the influence of mechanical unloading on the repair of bone defects with implantation of biodegradable bone substitutes. Spherical granules of biodegradable hydroxyapatite composed of rod-shaped particles (RHA) or beta-tricalcium phosphate composed of rod-shaped particles (RTCP) were implanted into a bone defect created in the distal end of the right femur of 8-week-old Wistar rats. Two, 6, 10, and 22 weeks after implantation, part of the sciatic nerve in the thigh was resected and exposed to mechanical unloading for 2 weeks. Then, 4, 8, 12 and 24 weeks after implantation, repair of the bone defect was analyzed. As a control, the bone defect without implantation of ceramic granules was also analyzed. Both RHA and RTCP tended to be reduced, but the reduction was not obvious during the experimental period. At 12 and 24 weeks after implantation, the amount of newly formed bone in the animal implanted with RHA was significantly greater than that at 4 weeks after implantation, but that in the animal implanted with RTCP or without implantation was not significantly different. The number of osteoclasts in the region implanted with RHA was significantly larger than that of the region implanted with RTCP or without implantation at 12 and 24 weeks. The activities of alkaline phosphatase in osteoblasts and tartrate-resistant acid phosphatase in osteoclasts were remarkably increased in the bone defects with implantation compared with those in the bone defects without implantation. These results suggested that RHA stimulated osteogenesis and osteoclastogenesis even after 2 weeks of mechanical unloading, and that RHA could be expected to improve the repair of bone defects in patients under the condition of skeletal unloading.

Osteoconductivity of hydrothermally synthesized beta-tricalcium phosphate composed of rod-shaped particles under mechanical unloading

Spherical beta-tricalcium phosphate (b-TCP) granules synthesized using a unique dropping slurry method expressed good osteoconductivity with prominent bone apposition and bioresorbability when implanted into the rat femur (Gonda et al., Key Eng. Mater. 361-363:1013-1016, 2008). The spherical b-TCP granules were implanted into the bone defect created in the distal end of the right femur of each 8-week-old female Wistar rat. To analyze performance of the spherical b-TCP granules as bone substitute in the bone with reduction in osteogenic potential, the right sciatic neurectomy was performed after implantation and the right hind limb was kept unloaded for 2 weeks before euthanization. Four weeks after implantation, some spherical b-TCP granules with resorption in part were surrounded by newly formed bone. Eight and 12 weeks after implantation, most of the residual b-TCP granules were embedded in newly formed bone, and total volume of the implant and newly formed bone was more than the other portions of the bone or the bone of control animals. Osteoclast activity in the implanted area was also higher than the other portions of the bone or the bone of control animals. Replacement of the intraosseous residual b-TCP granules for bone progressed at 12 weeks after implantation compared to those at 8 weeks after implantation. These data suggested that the spherical b-TCP granules stimulated osteogenesis and osteoclast activity of the unloaded bone.

Microstructure Designing of Porous β-Tricalcium Phosphate for Control of Reactions in the Bone

Porous materials of β-tricalcium phosphate (β-Ca3(PO4)2; β-TCP) were prepared from porous hydroxyapatite (Ca10(PO4)6(OH)2; HA) with calcium deficient composition of Ca/P molar ratio of 1.50 synthesized by hydrothermal method. The porous β-TCP was composed of rod-shaped particles of about 10-20 μm in length. Rod-shaped particles were locked together to make micro-pores, and the size of micro-pores formed by tangling of rod-shaped particles was about 0.1-0.5 μm. The particle size and micro-pore size could be controlled by our unique method. It must be suitable for the bone graft material and as the scaffold of cultured bone.

Midterm Clinical Results in Rugby Players Treated With the Bristow Procedure

Background: Although surgical shoulder stabilization by coracoid transfer is effective for collision athletes and has a low reinjury rate, no reports have described the midterm results of this procedure in specific patient cohorts of sufficient number or provided subjective assessments of these patients. Purpose: To evaluate midterm results after treatment of shoulder instability with the Bristow procedure in a large cohort of rugby players. Study Design: Case series; Level of evidence, 4. Methods: This study included 176 shoulders of 152 competitive rugby players who underwent shoulder stabilization surgery (Bristow procedure with Bankart repair) with a mean follow-up of 4 years (minimum of 2 years) in our institute. The primary outcome measure was the difference in the presurgical and postsurgical functional Rowe score and Western Ontario Shoulder Instability index (WOSI) score and factors affecting these scores. Complication rates and associated factors were also investigated. Results: In total, 176 shoulders of 152 patients underwent the Bristow procedure with Bankart repair, and 93.2% of the players returned to their preinjury competition level at a mean of 6.3 months postoperatively. All Rowe and WOSI scores were significantly improved after surgery. The numbers of shoulders with functional failure as indicated by the Rowe score, WOSI score, and inability to return to the previous level of play were 28 (15.9%), 54 (30.7%), and 12 (6.8%), respectively. Multiple logistic regression analyses demonstrated that reinjury after surgery (odds ratio [OR] = 35.1) and the number of shoulder dislocations (OR = 11.2-11.4) negatively affected the competition level after return to play, while reinjury (OR = 11.1-17.8), the number of shoulder subluxations (OR = 1.1-2.9), injury in the dominant shoulder (OR = 1.2-2.2), and large bone defects (OR = 1.1-11.5) negatively affected functional scores. Reinjury after shoulder stabilization occurred in 6 of 176 shoulders (3.4%). Multiple logistic regression analysis demonstrated that reinjury after surgery occurred more frequently in players at lower versus higher grade levels of competition (OR = 21.0). Although differences were not significant, a trend was noted toward higher postoperative reinjury rates in forward players, those in the upper categories (professional and college), and those with injury in the nondominant shoulder. Conclusion: The Bristow procedure provides good midterm outcomes for competitive collision athletes, while postsurgical reinjury, the number of preoperative dislocations and subluxations, and large bone defects negatively affect postsurgical shoulder function. This information may be useful for treatment of shoulder dislocations in collision athletes.