Artificial bone replacement has made an important contribution to safeguard human health and improve the quality of life. The application requirements of rapid prototyping technology based on reverse engineering in individualized artificial bone with individual differences are particularly urgent. This paper reviewed the current research and applications of rapid prototyping and reverse engineering in artificial bone. The research developments and the outlook of bone kinematics and dynamics simulation are also introduced.
ObjectiveTo investigate the mechanism of early vascularization of the tissue engineered bone in the treatment of rabbit radial bone defect by local injection of angiopoietin 2 (Ang-2).MethodsForty-eight New Zealand white rabbits were established unilateral 1.5 cm long radius defect models. After implantation of hydroxyapatite/collagen scaffolds in bone defects, the rabbits were randomly divided into 2 groups: control group (group A) and Ang-2 group (group B) were daily injected with 1 mL normal saline and 1 mL saline-soluble 400 ng/mL Ang-2 at the bone defect within 2 weeks after operation, respectively. Western blot was used to detect the expressions of autophagy related protein [microtubule associated protein 1 light chain 3 (LC3), Beclin-1], angiogenesis related protein [vascular endothelial growth factor (VEGF)], and autophagy degradable substrate protein (SQSTMl/p62) in callus. X-ray films examination and Lane-Sandhu X-ray scoring were performed to evaluate the bone defect repair at 4, 8, and 12 weeks after operation. The rabbits were sacrificed at 12 weeks after operation for gross observation, and the angiogenesis of bone defect area was observed by HE staining.ResultsWestern blot assay showed that the relative expressions of LC3-Ⅱ/LC3-Ⅰ, Beclin-1, and VEGF in group B were significantly higher than those in group A, and the relative expression of SQSTMl/p62 was significantly lower than that in group A (P<0.05). Radiographic and gross observation of specimens showed that only a few callus were formed in group A, the bone defect was not repaired; more callus were formed and complete repair of bone defect was observed in group B. The Lane-Sandhu scores in group B were significantly higher than those in group A at 4, 8, and 12 weeks after operation (P<0.05). HE staining showed that the Harvard tubes in group B were well arranged and the number of new vessels was significantly higher than that in group A (t=–11.879, P=0.000).ConclusionLocal injection of appropriate concentration of Ang-2 may promote early vascularization and bone defect repair of tissue engineered bone in rabbits by enhancing autophagy.
Objective To investigate the optimal mixing ratio of recombinant human bone morphogenetic protein 2 (rhBMP-2) with porous calcium phosphate cement (PCPC) and autologous bone as bone grafting material for the repair of large bone defects using Masquelet technique. The effect of platelet-rich plasma (PRP) on the healing of bone defects was evaluated under the optimal ratio of mixed bone. Methods Fifty-four New Zealand White rabbits were taken to establish a 2 cm long bone defect model of the ulna and treated using the Masquelet technique. Two parts of the experiment were performed in the second phase of the Masquelet technique. First, 36 modeled experimental animals were randomly divided into 4 groups (n=9) according to the mass ratio of autologous bone and rhBMP-2/PCPC. Group A: autologous bone (100%); group B: 25% autologous bone+75% rhBMP-2/PCPC; group C: 50% autologous bone+50% rhBMP-2/PCPC; group D: 75% autologous bone+25% rhBMP-2/PCPC. The animals were executed at 4, 8, and 12 weeks postoperatively for general observation, imaging observation, histological observation (HE staining), alkaline phosphatase (ALP) activity assay, and biomechanical assay (three-point bending test) were performed to assess the osteogenic ability and to determine the optimal mixing ratio. Then, 18 modeled experimental animals were randomly divided into 2 groups (n=9). The control group was implanted with the optimal mixture ratio of autologous bone+rhBMP-2/PCPC, and the experimental group was implanted with the optimal mixture ratio of autologous bone+rhBMP-2/PCPC+autologous PRP. The same method was used to observe the above indexes at 4, 8, and 12 weeks postoperatively. Results The bone healing process from callus formation to the cortical connection at the defected gap could be observed in each group after operation; new bone formation, bridging with the host bone, and bone remodeling to normal bone density were observed on imaging observation; new woven bone, new capillaries, bone marrow cavity, and other structures were observed on histological observation. The ALP activity of each group gradually increased with time (P<0.05); the ALP activity of group A was significantly higher than that of the other 3 groups at each time point after operation, and of groups C and D than group B (P<0.05); there was no significant difference between groups C and D (P>0.05). Biomechanical assay showed that the maximum load in three-point bending test of each group increased gradually with time (P<0.05), and the maximum loads of groups A and D were significantly higher than that of groups B and C at each time point after operation (P<0.05), but there was no significant difference between groups A and D (P>0.05). According to the above tests, the optimal mixing ratio was 75% autogenous bone+25% rhBMP-2/PCPC. The process of new bone formation in the experimental group and the control group was observed by gross observation, imaging examination, and histological observation, and the ability of bone formation in the experimental group was better than that in the control group. The ALP activity and maximum load increased gradually with time in both groups (P<0.05); the ALP activity and maximum load in the experimental group were significantly higher than those in the control group at each time point after operation (P<0.05), and the maximum load in the experimental group was also significantly higher than that in group A at 12 weeks after operation (P<0.05). ConclusionIn the second phase of Masquelet technique, rhBMP-2/PCPC mixed with autologous bone to fill the bone defect can treat large bone defect of rabbit ulna, and it has the best osteogenic ability when the mixing ratio is 75% autologous bone+25% rhBMP-2/PCPC. The combination of PRP can improve the osteogenic ability of rhBMP-2/PCPC and autologous bone mixture.
ObjectiveTo observe the ability of osteogenesis in vivo using the injected absorbable polyamine acid/calcium sulfate (PAA/CS) composites and assess their ability to repair bone defects. MethodWe selected 48 New Zealand white rabbits, and half of them were male with a weight between 2.0 and 2.5 kg. Bone defect models were made at the rabbit femoral condyle using electric drill, and the rabbits were divided into two groups. One group accepted implantation of the material at the defect, while nothing was done for the control group. After four, eight, twelve and sixteen weeks, the animals were killed. The line X-ray and hard tissue slices histological examination (HE, MASSON staining) were observed to assess the situation of degradation, absorption and bone formation of the material. ResultsFour weeks after operation, bone defect of the experimental group had no obvious callus growth on X-ray imaging. Histology showed that the material began to degrade and new immature trabecular bone grew. The bone defect of the experimental group had a small amount of callus growth on X-ray imaging after eight weeks. And histology showed that the material continued to degrade and new immature trabecular bone grew continually. There was an obvious callus growth after twelve weeks, and the bone defect area had smaller residual low-density shadow on X-ray imaging. Histology showed that most of the materials degraded and parts of woven bone grew into lamellar bone. After sixteen weeks, the composites were absorbed completely, replaced by new bone tissues, and the new bone was gradually changed from woven bone into mature plate of bone. There was no significant change in bone defect in the control group within twelve weeks, and part of bone defect hole became smaller, and partial edge repair could be detected. ConclusionsThe PAA/CS composites can be completely degraded and absorbed, with a certain activity of bone formation, expected to be used as bone repair materials.
To investigate the cl inical results and the mechanism of bone heal ing for the repair of bone defects following tumor resection with novel interporous TCP bone graft, and to test the hypothesis of “structural transplantation”. Methods From January 2003 to December 2005, 61 cases of various bone defects following the curettage of the benign bone tumors were treated with interporous TCP, with 33 males and 28 females, including bone fibrous dysplasiain 8 cases, bone cyst in 23 cases, eosinophil ic granuloma in 12 cases, enchondroma in 13 cases, non-ossifying fibroma in 2 cases, and osteoblastoma in 3 cases. Tumor sizes varied from 1.5 cm × 1.0 cm to 7.0 cm × 5.0 cm. The plain X-ray, single photon emission computed tomography (SPECT) and histology examination were obtained at various time points after operation. The in vivo biodegradation rate of the implanted TCP was evaluated based on a semi-quantitive radiographic analyzing method. Histopathology examination was performed in 1 revision case. Results All the patients were followed up for 5 to 24 months after operation. They all had good wound heal ing and bone regeneration. There was neither significant reverse reaction to the transplanted material nor locally inflammatory reaction in all of the cases. The bone defects were repaired gradually from 1 to 6 months after operation (bone heal ing at average 2.6 months after surgery) with a bone heal ing rate up to 96.7%. There was only 1 recurrence case (eosinophil ic granuloma in ischium) 3 months after operation. Given revision operation, this case gained bone heal ing. Radiographically, the interface between the implanted bone and host bone became fuzzy 1 month after implantation, indicating the beginning of new bone formation. Three months later, the absorption of the interporous TCP was noticed from peripheral to the center of the implanted bone evidenced by the vague or fuzzy realm. New bone formation could be seen both in peri pheral and central areas. Six months later, implanted bone and host bone merged together and the bone defect was totally repaired, with 78.9% degradation rate of the implanted TCP. Twelve months later, the majority of the implanted bone was absorbed and bone remodel ing was establ ished. In the cases that were followed up for 24 months, the function of affectedextremity was excellent with good bone remodel ing without recurrence. In 2 cases, SPECT showed that nucl ide uptake could be observed in implanted site and the metabol ic activity was high both in the central as well as the peripheral areas of the graft 1 month after implantation, which was an evidence of osteogenesis. Pathologically, the interporous TCP closely contacted the host bone inside the humerus 1 month after grafting. The interface between the implanted bone and host bone became fuzzy, and vascularized tissue began growing inside the implanted graft as a “l ining” structure. Conclusion The interporous TCP proves to be effective for cl inical reparation of bone defects following tumor resection. The inside three-dimensional porous structure simulates the natural bionic bone structure which is suitable for recruitment related cells in-growth into the scaffold, colonizing and prol iferation companied with the process of vascularize, finally with the new bone formation. The novel interporous TCP may boast both bone conductive and bone inductive activities, as an appeal ing “structural transplantation” bone graft.
Objective To evluate the clinical outcome of autograftsof ilium and interbody fusion cage or bone morphogenetic protein(BMP)／artificial bone material／ cage in treating lumbar spondylolisthesis. Methods From January 1997 to January 2004，114 patients with lumbar spondylolisthesis were treated with posterior lumbar interbody fusion and pedicle screw fixation． There were 45 males and 69 females with an average age of 43 years ranging from 32 to 61 years. Of 114patients, 85 cases were classified as degree Ⅰ, 24 cases as degree Ⅱ and 5 cases as degree Ⅲ. The patients were divided into three groups accordingto the material used for interbody fusion: autografts of ilium (group A, n=42), interbody fusion cages(group B, n=36), and BMP／artificial bone material／ cage (group C, n=36)．The clinical and radiographic results of the patients were compared among three groups． Results All patients were followed from 13 to 30 months with an average of 15 months． There were no statistically significant differences in surgical time, blood loss, and disc space height of preoperation(P＞0.05) among three groups. No severe complication occurred in the three groups(P＞0.05). The excellent and good rates in groups A，B and C were 81.0％, 80.6％, and 83.3％ respectively, showing no statisticallysignificant difference(P＞0.05)．The fusion rate of group C(97.0%) was significantly higher than those of group A(81.0%) and group B(83.3%) (P＜0.05) after 1 year of operation．And the average loss of disc space height in groups B and C was significantly lower than that in group A(P＜0.05). Conclusion Higher fusion rate and lower loss of disc space height can beobtained in treating lumbar spondylolisthesis with BMP／artificial bone materiel.It is an effective method in the treatment of spondylolisthesis.
The hydroxyapatite particles were used to repair 23 cases of depressed deformities of face. The patients were follwed up for 3 to 8 months and the short termresults were satisfactory. The operative procedure was briefly introduced. The advantages and attentions relevant to the operation were discussed.