Rabbit Radial Defect Research Articles

Evaluation of Antibiotic-Impregnated Microspheres for the Prevention of Implant-Associated Orthopaedic Infections

Prevention of infection associated with uncemented orthopaedic implants could lead to improved implant stability and better patient outcomes. We hypothesized that coating porous metal implants with antibiotic-containing microspheres would prevent infections in grossly contaminated wounds. Bioresorbable polymer microspheres containing tobramycin were manufactured and pressed into porous metal cylinders that were then implanted into radial defects in rabbits. Control implants that did not contain antibiotic microspheres were also implanted into the contralateral limbs. Each implant was then contaminated with Staphylococcus aureus prior to closure of the wound. The animal was euthanized after clinical signs of infection appeared, or at two weeks after surgery. Periprosthetic tissue was cultured for the presence of S. aureus, and integration of the implant with the surrounding bone was measured. The antibiotic microspheres successfully prevented infection in 100% of the eleven limbs with treated implants, which represented a significant improvement (p = 0.004) compared with the infection rate of 64% (seven of eleven) for the limbs with control implants. Implant integration averaged 38.87% ± 12.69% in the fifteen uninfected limbs, which was significantly better (p = 0.012) than the average of 19.46% ± 14.49% in the seven infected limbs. The antibiotic delivery system successfully prevented infection in 100% of the cases studied, resulting in an increase in implant integration. Antibiotic delivery utilizing the system described here may be effective in preventing implant-associated infections after orthopaedic surgery and increasing the longevity of orthopaedic implants.

Bone regeneration potential of allogeneic or autogeneic mesenchymal stem cells loaded onto cancellous bone granules in a rabbit radial defect model

For developing a clinically effective bone regeneration strategy, we compare the bone regeneration potential of cultured allogeneic bone marrow-derived mesenchymal stem cells (BM-MSCs) and of autologous BM-MSCs loaded onto allogeneic cancellous bone granule scaffolds. A critical-sized segmental bone defect was made at the mid-shaft of both radiuses in 19 New Zealand White rabbits (NWRs). In the experimental group, allogeneic BM-MSCs loaded onto small-sized allogeneic cancellous bone granules (300~700 um in diameter) were implanted in one side of a bone defect. In the control group, autologous BM-MSCs loaded onto allogeneic cancellous granules were grafted in the other side. Bone regeneration was assessed by radiographic evaluation at 4, 8, 12 and 16weeks post-implantation and by micro-computed tomography (micro-CT) and histological evaluation at 8 and 16weeks. The experimental groups showed lower bone quantity indices (BQIs) than the control groups at 12 and 16weeks (p < 0.05), although no significant difference was observed at 4 and 8weeks (p > 0.05). Micro-CT analysis revealed that both groups had similar mean total bone volume and other parameters including trabecular thickness, number and separation at either 8 or 16weeks. Only bone surface area revealed less area in the experimental group at 16weeks. Histological evaluation of 8-week and 16-week specimens showed similar biologic processes of new bone formation and maturation. There was no inflammatory reaction indicating an adverse immune response in both allogeneic and autologous MSC groups. In conclusion, allogeneic BM-MSCs loaded onto allogeneic cancellous bone granules had comparable bone regeneration potential to autologous BM-MSCs in a rabbit radial defect model.

Reconstruction of radial bone defect using gelatin sponge and a BMP-2 combination graft

Many bioactive molecules like recombinant human bone morphogenetic protein 2 (rhBMP-2) have been developed for mineralized bone grafts, for which proper scaffolds are necessary to successfully apply the bioactive molecules. In this study, we tested the osteogenic efficacy of rhBMP-2 produced in-house in combination with gelatin sponge as the scaffold carrier in a rabbit radial defect model. The efficacy of the rhBMP-2 was determined by alkaline phosphatase activity assay of C2C12 cells. Two groups of ten rabbits each were treated with rhBMP-2/gelatin sponge, or gelatin sponge only. At 4 weeks, rhBMP-2/gelatin sponge grafts showed more bone regeneration than gelatin sponge grafts, as determined by X-ray radiography, micro-computed tomography, and histological analyses. At 8 weeks, rhBMP-2/gelatin sponge grafts exerted much stronger osteogenic effects. The study demonstrates the improved osteogenic efficacy of the rhBMP-2/gelatin sponge grafts in a rabbit radial bone defect model acting as a bone-inductive material. [BMB Reports 2013; 46(6): 328-333]

Unique microstructural design of ceramic scaffolds for bone regeneration under load

During the past two decades, research on ceramic scaffolds for bone regeneration has progressed rapidly; however, currently available porous scaffolds remain unsuitable for load-bearing applications. The key to success is to apply microstructural design strategies to develop ceramic scaffolds with mechanical properties approaching those of bone. Here we report on the development of a unique microstructurally designed ceramic scaffold, strontium–hardystonite–gahnite (Sr–HT–gahnite), with 85% porosity, 500μm pore size, a competitive compressive strength of 4.1±0.3MPa and a compressive modulus of 170±20MPa. The in vitro biocompatibility of the scaffolds was studied using primary human bone-derived cells. The ability of Sr–HT–gahnite scaffolds to repair critical-sized bone defects was also investigated in a rabbit radius under normal load, with β-tricalcium phosphate/hydroxyapatite scaffolds used in the control group. Studies with primary human osteoblast cultures confirmed the bioactivity of these scaffolds, and regeneration of rabbit radial critical defects demonstrated that this material induces new bone defect bridging, with clear evidence of regeneration of original radial architecture and bone marrow environment.

The Potential Use of Allogeneic Platelet-Rich Plasma for Large Bone Defect Treatment: Immunogenicity and Defect Healing Efficacy

Autologous platelet-rich plasma (PRP) has been extensively investigated for large bone defect treatment, but its clinical application is harassed by controversial outcome, due to highly variable PRP quality among patients. Alternatively, allogeneic PRP from well-characterized donors cannot only generate more consistent and reliable therapeutic effect but also avoid harvesting large quantities of blood, an additional health burdens to patients. However, the use of allogeneic PRP for bone defect treatment is generally less investigated, especially for its immunogenicity in such application. Here, we meticulously investigated the immunogenicity of allogeneic PRP and evaluated its healing efficacy for critical-sized defect treatment. Allogeneic PRP contained 4.1-fold and 2.7- to 4.9-fold higher amount of platelets and growth factors than whole blood, respectively. The intramuscular injection of allogeneic PRP to rabbits did not trigger severe and chronic immunoresponse, evidenced by little change in muscular tissue microstructure and CD4⁺/CD8⁺ T lymphocyte subpopulation in peripheral blood. The implantation of allogeneic PRP/deproteinized bone matrix (DPB) constructs (PRP+DPB) successfully bridged 1.5-cm segmental radial defects in rabbits, achieving similar healing capacity as autologous MSC/DPB constructs (MSC+DPB), with greater bone formation (1.1-1.5×, p<0.05) and vascularization (1.3-1.6×, p<0.05) than DPB alone, shown by histomorphometric analysis, bone mineral density measurement, and radionuclide bone imaging. Furthermore, the implantation of both allogeneic PRP- and autologous MSC-mediated DPB constructs (PRP + MSC + DPB) resulted in the most robust bone regeneration (1.2-2.1×, p<0.05) and vascularization (1.3-2.0×, p<0.05) than others (PRP+DPB, MSC+DPB, or DPB alone). This study has demonstrated the promising use of allogeneic PRP for bone defect treatment with negligible immunogenicity, great healing efficacy, potentially more consistent quality, and no additional health burden to patients; additionally, the synergetic enhancing effect found between allogeneic PRP and autologous MSCs may shed a light on developing new therapeutic strategies for large bone defect treatment.

Repairing a critical-sized bone defect with highly porous modified and unmodified baghdadite scaffolds

This is the first reported study to prepare highly porous baghdadite (Ca3ZrSi2O9) scaffolds with and without surface modification and investigate their ability to repair critical-sized bone defects in a rabbit radius under normal load. The modification was carried out to improve the mechanical properties of the baghdadite scaffolds (particularly to address their brittleness) by coating their surfaces with a thin layer (∼400nm) of polycaprolactone (PCL)/bioactive glass nanoparticles (nBGs). The β-tricalcium phosphate/hydroxyapatite (TCP/HA) scaffolds with and without modification were used as the control groups. All of the tested scaffolds had an open and interconnected porous structure with a porosity of ∼85% and average pore size of 500μm. The scaffolds (six per scaffold type and size of 4mm×4mm×15mm) were implanted (press-fit) into the rabbit radial segmental defects for 12weeks. Micro-computed tomography and histological evaluations were used to determine bone ingrowth, bone quality, and implant integration after 12weeks of healing. Extensive new bone formation with complete bridging of the radial defect was evident with the baghdadite scaffolds (modified/unmodified) at the periphery and in close proximity to the ceramics within the pores, in contrast to TCP/HA scaffolds (modified/unmodified), where bone tended to grow between the ulna adjacent to the implant edge. Although the modification of the baghdadite scaffolds significantly improved their mechanical properties, it did not show any significant effect on in vivo bone formation. Our findings suggest that baghdadite scaffolds with and without modification can serve as a potential material to repair critical sized bone defects.

New bone formation in a true bone ceramic scaffold loaded with desferrioxamine in the treatment of segmental bone defect: a preliminary study

BackgroundDesferrioxamine (DFO), an iron chelator, can stimulate osteogenesis and angiogenesis by stabilizing hypoxia-inducible factor 1α. We postulate that a bone graft substitute combined with DFO is beneficial to the reconstruction of bone defects. MethodsWe implanted pure true bone ceramic (TBC) and DFO-loaded TBC (DFO/TBC) scaffolds into 15-mm rabbit radial defects for 8weeks. The bone segments were examined with X-ray, micro-CT and histology. ResultsRadiographs showed that the DFO/TBC scaffold became radiopaque, and the gaps between the scaffold and radial cut ends were often invisible. Variables from micro-CT, including the bone volume fraction (BV/TV), trabecular thickness (Tb.Th) and trabecular number (Tb.N), were significantly increased in pure TBC and DFO/TBC scaffolds that had been implanted for 8weeks compared to unimplanted TBC scaffolds (p values <0.05–0.001). Between the former two groups, BV/TV and Tb.Th were significantly increased in DFO/TBC scaffolds (p < 0.001), but Tb.N did not show significant differences. Histological examinations showed considerably increased new bone and decreased TBC trabecular remnants in DFO/TBC scaffolds compared to pure TBC scaffolds. Many cavities in the new bone area in DFO/TBC scaffolds were occupied by bone marrow elements and blood vessels. Percent of new bone with tetracycline labeling was significantly greater in DFO/TBC scaffolds than in pure TBC scaffolds (p < 0.001). ConclusionThis preliminary study reveals that DFO can effectively induce new bone growing into TBC scaffolds, suggesting that the DFO/TBC composite is a promising bone graft substitute for the treatment of bone defects.

Repair of rabbit radial defect by using xenogenic deproteinized bone scaffold

Objective To evaluate the efficiency of xenogenic deproteinized bone (DPB) based on cortical bone-derived osteoblasts as an alternative in repair of critical bone defect.Methods A total of 36 Newzealand rabbits were randomly divided into groups A,B and C.Critical bone defect with a length of 1.5 cm was created in one side of the radius.The defect was filled with a DPB scaffold seeded with osteoblasts (group A),autograft (group B) and DPB scaffold (group C).All specimens were selected for X-ray examination,bone mineral density (BMD) measurements,gross samples observation,biomechanical test and histological observation at 12th week postoperation.Results X-ray examination displayed that the radial defect which was still obvious in group C disappeared in groups A and B.BMD measurements showed that there was no significant difference in BMD between groups A and B,but that was higher in group C (P ＜ 0.05).Gross samples observation revealed that the radial defect which was still obvious in group C disappeared in groups A and B.Biomechanical testing demonstrated that the maximum bend load in groups A and B was significantly higher than in group C (P ＜ O.05 ).Histologically,there was abundant of newly bone formation in group A,the medullary cavity recanalized in group B,and a small amount of newly bone formation in group C.Conclusion Radial critical bone defect could be repaired efficiently by xenogenic DPB based on cortical bone-derived osteoblasts. Key words: Osteoblasts; Deproteinized bone; Bone defect

Comparison of the osteogenic potentials of autologous cultured osteoblasts and mesenchymal stem cells loaded onto allogeneic cancellous bone granules

We compared the bone regeneration potentials of autologous cultured osteoblasts and of bone-marrow-derived autologous MSCs in combination with allogeneic cancellous bone granules in a rabbit radial defect model. Radial shaft defects over 15mm were made in 26 New Zealand white rabbits. The animals underwent insertion of allogeneic cancellous bone granules containing autologous osteoblasts into right-side defects (the experimental group) and of allogeneic cancellous bone granules with autologous MSCs into left-side defects (the control group). To quantitatively assess bone regeneration, radiographic evaluations as well as BMD and BMC measurements were performed 3, 6, 9 and 12weeks post-implantation and histology as well as micro-CT image analysis were performed at 6 and 12weeks. Radiographic evaluations 3 weeks post-implantation showed that the experimental group had a higher mean bone quantity index (p < 0.05) and micro-CT image analysis showed that experimental sides had a greater mean total regenerated bone volume and surface area than the control sides (p < 0.05). Histologic evaluations obtained at 6 and 12weeks revealed distinctly greater granule resorption and new bone formation in the experimental group. This in vivo study demonstrates that a combination of autologous osteoblasts and small-sized, allogeneic cancellous bone granules leads to more rapid bone regeneration than autologous MSCs and small-sized, allogeneic cancellous bone granules.

Enhanced bone formation in large segmental radial defects by combining adipose-derived stem cells expressing bone morphogenetic protein 2 with nHA/RHLC/PLA scaffold

In this study, rabbit adipose-derived stem cells (rASCs) were isolated, cultured in vitro, and transfected with recombinant adenovirus vector containing human bone morphogenetic protein 2 (Ad-hBMP2). These cells were combined with a nano-hydroxyapatite/recombinant human-like collagen/poly(lactic acid) scaffold (nHA/RHLC/PLA) to fabricate a new biocomposite (hBMP2/rASCs-nHA/RHLC/PLA, group 1) and cultured in osteogenic medium. Non-transfected rASCs mixed with nHA/RHLC/PLA (rASCs-nHA/RHLC/PLA, group 2) and nHA/RHLC/PLA scaffold alone (group 3) served as controls. Scanning electron microscope (SEM) demonstrated integration of rASCs with the nHA/RHLC/PLA scaffold. Quantitative real-time RT-PCR analyses of collagen I, osteonectin, and osteopontin cDNA expression indicated that the osteogenic potency of rASCs was enhanced by transfection with Ad-hBMP2. After in vitro culture for seven days, three groups were implanted into 15-mm length critical-sized segmental radial defects in rabbits. After 12 weeks, radiographic and histological analyses were performed. In group 1, the medullary cavity was recanalised, bone was rebuilt and moulding was finished, the bone contour had begun to remodel and scaffold was degraded completely. In contrast, bone defects were not repaired in groups 2 or 3. Furthermore, the scaffold degradation rate in group 1 was significantly higher than in groups 2 or 3. In summary, after transduction with Ad-hBMP2, the osteogenesis of rASCs was enhanced; a new biocomposite created with these cells induced repair of a critical bone defect in vivo in a relatively short time.

Application of silk fibroin bio-material combined with bone marrow mesechymal stem cells in the construction of tissue engineered bone for repairing of segmental bone defect

Objective To investigate the possibility of adopting the silk fibroin biomaterial as the scaf-fold for bone marrow mesechymal stem cells(BMSCs) in the repair of rabbit radial defects. Methods BMSCs were isolated and co-cultured with the silk fibroin biomaterial in vitro. The growth condition of these cells on the scaffold was observed under electronic microscope. Bone defect models were made by removing 15 mm length of midshaft radial bone in 24 New Zealand rabbits. Animals were randomly devided into the experimental group in which the BMSCs seeded silk fibroin scaffold were transplanted, control group in which simple silk fibroin bioma-terial scaffold was adopted and blank group in which rabbits were left untreated. The repair of the defects was observed at 2, 4, 8, 12 weeks after operation, respectively. Results The rabbits BMSCs grew well on the material and the animals treated with grafts exhibited new bone formation. Result from experimental group was apparently superior to that of the control group at 2, 4, 8, 12 weeks after operation. No formation of new bone was found after operation in the blank group. Conclusion The proposed method of combining the BMSCs with silk fibroin bio-material to repair the rabbit radial defects is feasible, and the silk fibroin biomaterial can be applied in the bone tissue engineering as the material of frame. Key words: Silk fibroin biomaterial ; Mesenchymal stem cells ; Bone tissue engineering ;

Radiographic Evaluations of the Tetra-Calcium Phosphate and Diacalcium Phosphate with Bone Plate in Osseo-Integration of Bone Repair in Rabbit

Problem statement: To determine the effect of the Tetra calcium phosphate and Diacalcium phosphate cement in comparison with bone plate in fracture repair in rabbit. Experimental in vivo study. A total of 18 adult male White New Zealand rabbits, weighing 3.0±0.250 Kg and about 6 months old were used. They were fasted 4 h before start of experiment and were off-water even 2 h too. They were divided into 2 groups of bone plate (I) and cement (II) of 9 rabbits each which subsequently divided into 3 subgroups of 1(I a and II a) month and 2 (Ib and IIb)and 3 (Ic and IIc) months duration in each group. Approach: Under general anesthesia and aseptic condition the craniolateral surface of right radial was exposed and a piece of full thickness from mid-section of radial bone in length of 1cm was removed using electrical bone vibrator in the all rabbit. The both ends of this bone was stabilized using mini bone plate of 4 holes in the group I , whereas prehardened cylinders of cement were implanted into rabbit radial defects in the group II rabbits. Radiographs were taken on zero days after creation of gap and on 1, 2 and 3 months from each rabbit using parameters such as local changes, stabilization of implant and bone, bone formation and implant biodegradation. Results: Comparison of clinical signs in the I and II indicated that they had similar physical activity and same degree of lameness during observation period of 90 days Radiographyically keeping in view the parameters were used to evaluate the major changes revealed no sign of infection on the edges of each defect and both groups permitted stabilization of the defected bones and maintenance of correct position. The new bone formation and the implant biodegradation in the bone defects could be clearly reflected by the gradually weakened umbral on the radiographs during the whole process one repair in group I was not as perfect as those in cement or group II samples. Conclusion/Recommendations: Application of paste of tetra calcium phosphate and diacalcium phosphate indicated to have positive effect in integral formation of qualitative callus at the site of fracture and early re-organization of callus too.

Orthotopic bone formation in titanium fiber mesh loaded with platelet-rich plasma and placed in segmental defects

The effect of platelet-rich plasma (PRP) on bone formation was investigated in a rabbit segmental radial defect model. The purpose of the study was to evaluate the bone inductive properties of PRP with titanium fiber mesh and autologous bone chips in a 15-mm rabbit radial defect model. Eighteen New Zealand white rabbits were divided into three groups: I, PRP with autologous bone (PRP-Ti-Bone); II, autologous bone (Ti-Bone); III, control group (Ti). The implants were placed in the radial defect for 12 weeks. After sacrifice, all specimens were harvested for histological, histomorphometrical and radiographic analysis. Histomorphometrical analysis showed that bone formation was higher in the implants with PRP (PRP-Ti-Bone: 37 ± 8%) than in those without PRP (Ti-bone: 25 ± 6% and Ti: 25 ± 5%) after 12 weeks of implantation. It was concluded that PRP has a stimulatory effect on bone formation in titanium fiber mesh filled with autologous bone graft in segmental bone defects. Titanium fiber mesh was also shown to be an excellent scaffold material for the application of autologous bone grafts with or without PRP.

Closing capacity of segmental radius defects in rabbits

In the research of synthetic bone graft substitutes, the relevance for bone regeneration can be confirmed in a critical-sized model. In this study the rabbit radial defect was investigated as an ingenious model of critical size, due to its defect immobilizing intact ulna. In addition, the influence of poly(DL-lactic-co-glycolic acid) (PLGA) on bone regeneration was determined. Sixteen, 4-month-old rabbits received bilateral segmental radial defects of 15 or 20 mm. The osteotomy ends were marked with small titanium pins. Half of the group received injected PLGA microparticle/carboxymethylcellulose implants. Implantation time was 12 weeks. Evaluation consisted of radiographs after surgery and sacrifice, microcomputed tomography and histology. The radiographs revealed that the created defects were significantly smaller after sacrifice. Further a number of radii showed fibrocartilaginous interposition. Both findings indicated instability of the created defect. All evaluation techniques revealed that 15 and 20 mm were not of critical size, as most defects were more or less regenerated. PLGA microparticles did not influence bone regeneration significantly. In conclusion, 15- and 20-mm radius defects in 4-month-old rabbits were not a suitable model for bone regeneration as these defects were neither critical size nor stable. PLGA-microparticle degradation did not influence bone regeneration.

Repair of Segmental Defects with Nano-hydroxyapatite/Collagen/PLA Composite Combined with Mesenchymal Stem Cells

The aim of the present study was to investigate and compare the capacity of fresh-frozen allogeneic bone, nano-hydroxyapatite/collagen/PLA (nHAC/PLA) scaffold, and nHAC/PLA scaffold loaded with bone marrow mesenchymal stem cells (BMSCs) in inducing bone formation. A 10mm segmental rabbit radial defect was surgically created. The animals were divided into four groups in which the defect was either left untreated, or filled with the abovementioned three grafts. The animals were euthanized at 2, 4, 6, 8, 12, and 18 weeks. Radiographic and histologic analyses were performed on the harvested tissue. We show that nHAC/PLA composite combined with mesenchymal stem cells could enhance and accelerate bone formation in segmental defects of rabbits. nHAC/PLA composite is an ideal bone graft; implanting nHAC/PLA composite combined with mesenchymal stem cells is a potential method for surgical treatment of bone defects.

Construction of an injectable tissue-engineered bone graft using autologous PRP and radiographic evaluation of its effect on repairing segmental radial defects in rabbits

目的 用自体富血小板血浆(PRP)、骨髓基质干细胞(BMSCs)和纤维蛋白胶(FG)构建可注射型组织工程骨并从放射学方面评价其修复自体兔桡骨缺损的效果. 方法 36只新西兰兔随机分为 A、B、C三组,每组 12只.所有动物术前 1周抽取耳背中央动脉血提取 PRP. A组于术前 1～ 2个月抽取双髂骨处骨髓并培养出 BMSCs,在体外与 FG及自体 PRP构建成可注型组织工程骨,植入自体桡骨 1.5cm节段性骨缺损,为实验组. B、C两组分别植入 PRP+ FG、FG于同样骨缺损处为对照组.另取 4只桡骨同样部位和大小骨缺损旷置作为空白组.术后 4、8、12周时摄前臂正位 X线片.用放射影像学评分和图像分析 X线阻射影比较骨缺损的修复情况. 结果 A、B两组骨缺损放射影像学评分以及新生骨痂的密度在 4、8、12周均优于 C组 (P 0.05),但在新生骨痂密度上, A >B >C(P< 0.05).空白组术后 16周骨缺损无愈合. 结论 PRP对骨缺损愈合有明显促进作用,复合 PRP的可注射型材料与 BMSCs构建组织工程骨可修复兔桡骨节段性骨缺损。

In Vivo Evaluation of S-Chitosan Enhanced Calcium Phosphate Cements

Calcium phosphate cements (CPC), made from dicalcium phosphate dihydrate and calcium hydroxide and reinforced with water soluble S-chitosan, were investigated in vivo. Cylinders of these cements were prepared and prehardened before implantation into preformed radial defects in rabbits. Histological observations after 1, 4, 14 and 22 weeks, respectively, were performed on thin decalcified sections. No inflammation or other negative response was found in the S-chitosan containing cements (S-CPCs). After 4 weeks, newly formed trabeculae contacted with the implant directly in the lower S-chitosan sample, while a thin layer of fibers had formed between the newly formed bone and the implant in the higher S-chitosan samples. The degradation rates of the S-CPCs were significantly lower than the original CPC cement alone. Most of the S-chitosan cements were still present at the end of the 22 weeks. The implant material and the surrounding infiltrated fluid layer were examined by back scattered scanning electron microscopy and X-ray energy-dispersive spectrometry.

Bone repair in radii and tibias of rabbits with phosphorylated chitosan reinforced calcium phosphate cements

Biocompatibility of two calcium phosphate cements (CPCs), reinforced with phosphorylated chitosan (P-chitosan), was investigated in rabbits in present study. The two CPCs are monocalcium phosphate monohydrate (MPCM) with calcium oxide (CaO) in 1 m phosphate buffer (i.e. MCPM/CaO/1 m phosphate buffer cement, CPC-I) and dicalcium phosphate dihydrate (DCPD) with calcium hydroxide [Ca(OH) 2] in 1 m Na 2HPO 4 solution (i.e. DCPD/Ca(OH) 2/1 m Na 2HPO 4 cement, CPC-II). Different amount of P-chitosan was added to the liquid phase before the power phase was mixed with the liquid phase. The MCPM/CaO/1 m phosphate buffer/P-chitosan cements (P-CPC-I) with neutral pH were filled into the holey defects of rabbit tibias. While the DCPD/Ca(OH) 2/1 m Na 2HPO 4/P-chitosan cements (P-CPC-II) shaped as prehardened cylinders were implanted into rabbit radial defects. After operation, the two serial groups and CPC-II controls were observed for 1, 4, 12 and 22 weeks, respectively. Histological and histomorphological studies proved that P-chitosan containing cements are biocompatible, bioabsorbable and osteoinductive. The biodegradation rate has a negative relationship with the P-chitosan content. Progressive substitution took place at the interface of implants and host bones. No adverse effects were found in tissues around the bone defects. Thus, they could be used as bone substitutes in clinic.