Goat Tibia Research Articles

3D-Printed-Cryogel-Impregnated Functionalized Scaffold Augments Bone Regeneration in Critical Tibia Fracture in Goat.

Critical-size bone trauma injuries present a significant clinical challenge because of the limited availability of autografts. In this study, a photocurable composite comprising of polycaprolactone, polypropylene fumarate, and nano-hydroxyapatite (nHAP) (P─P─H) is printed, which shows good osteoconduction in a rat model. A cryogel composed of gelatin-nHAP (GH) is developed to incorporate osteogenic components, specifically bone morphogenetic protein-2 (BMP-2) and zoledronic acid (ZA), termed as GH+B+Z, which is investigated for osteoinductive property in a rat model. Further, a 3D-printed P─P─H scaffold impregnated with GH+B+Z is designed and implanted in a critical-size defect (25×10×5mm) in goat tibia. After 4 months, the scaffold is well-integrated with adjacent native bone, with osteoinduction observed in the cryogel-filled region and osteoconduction over the printed scaffold. X-ray radiography and micro-CT analysis showed bone in-growth in the treatment group with 45 ± 1.4% bone volume/tissue volume (BV/TV), while the defect remained unhealed in the control group with BV/TV of 10.5 ± 0.5%. Histology showed significant cell infiltration and matrix deposition over the printed P─P─H scaffold and within the GH cryogel site in the treatment group. Immunohistochemical staining depicted significantly higher normalized collagen I intensity in the treatment group (34.45 ± 2.61%) compared to the control group (4.22 ± 0.78).

Modified Layer-based Ultrasound Imaging of Irregularly Cortical Bone

Abstract Cortical bone, known for its multilayered composition with a diverse sound velocity distribution and anisotropy dependent on anatomical position, poses a challenge in conventional medical ultrasound imaging. The limitations arise due to the inability of uniform velocity to appropriately capture the intricate properties of hard tissues, leading to inaccurate reconstruction of the inner cortical layers. To tackle this complexity, a modified layer-based method utilizing a 5-layer model and estimated sound velocity was introduced for irregularly cortical bone imaging. Validated through an ex-vivo study using goat tibia, this method showcased remarkable effectiveness. The experimental outcomes revealed an ultrasound-reconstructed cortical image that closely matched the μCT-measured ground truth model, demonstrating mean cortical thickness errors of 0.31 mm. This method stands as a validated and precise approach for accurately imaging cortical bone using a 5-layer model.

In silico assessment of the bone regeneration potential of complex porous scaffolds

Mechanical environment plays a crucial role in regulating bone regeneration in bone defects. Assessing the mechanobiological behavior of patient-specific orthopedic scaffolds in-silico could help guide optimal scaffold designs, as well as intra- and post-operative strategies to enhance bone regeneration and improve implant longevity. Additively manufactured porous scaffolds, and specifically triply periodic minimal surfaces (TPMS), have shown promising structural properties to act as bone substitutes, yet their ability to induce mechanobiologially-driven bone regeneration has not been elucidated. The aim of this study is to i) explore the bone regeneration potential of TPMS scaffolds made of different stiffness biocompatible materials, to ii) analyze the influence of pre-seeding the scaffolds and increasing the post-operative resting period, and to iii) assess the influence of patient-specific parameters, such as age and mechanosensitivity, on outcomes. To perform this study, an in silico model of a goat tibia is used. The bone ingrowth within the scaffold pores was simulated with a mechano-driven model of bone regeneration. Results showed that the scaffold's architectural properties affect cellular diffusion and strain distribution, resulting in variations in the regenerated bone volume and distribution. The softer material improved the bone ingrowth. An initial resting period improved the bone ingrowth but not enough to reach the scaffold's core. However, this was achieved with the implantation of a pre-seeded scaffold. Physiological parameters like age and health of the patient also influence the bone regeneration outcome, though to a lesser extent than the scaffold design. This analysis demonstrates the importance of the scaffold's geometry and its material, and highlights the potential of using mechanobiological patient-specific models in the design process for bone substitutes.

Toughening Mechanism of the Bone — Enlightenment from the Microstructure of Goat Tibia

Abstract With the continuous advancement of space exploration missions, the mechanical environment for planetary detectors is becoming increasingly severe. As a result, fatigue, fracture, large deformation and other forms of failures are more likely to occur at the load-bearing structures. As a critical part of the load-bearing structure of a goat, goat tibia has remarkable toughness because of its unique microstructures. In this investigation, firstly, the cortical bone of goat tibia was observed by SEM, and the characteristic microstructures in different regions were identified. Secondly, the cross section of cortical bone was loaded by long-term inplane stress, then the toughness of cortical bone in different regions are obtained and compared based on the orientation and distribution of cracks after the load. Thirdly, a simplified FEM model mimicking typical microstructure of the cortical bone is proposed using cohesive modeling, and then the toughening mechanism of the typical microstructure is validated with numerical simulation. Finally, the toughening mechanisms of cortical bone were discussed according to the SEM observation as well as the numerical simulation. This study of the toughening mechanism of cortical bone can be helpful for the biomimetic design of high-toughness structures.

An inspiration from the microstructure of the cortical bone in goat tibia

When vigorous goats are running and jumping, their leg bones play a crucial role in dynamic loading. The hierarchical structure of diverse tissues at different length scales is commonly used to account for the superior mechanical properties of bone. Yet, how the goat tibia achieves its remarkable function remains mostly unknown. Scanning electron microscopy was employed to image the multi-scale microstructure of the cortical bone in goat tibia. A new processing method was utilized during the preparation of one of the three kinds of samples. The transverse and longitudinal sections of the cortical bone were observed thoroughly, and high-quality images of the internal organizations are acquired. Some interesting findings, including the two-layered character of cortical bone and the microstructure near osteocyte lacunae, are discussed. A three-dimensional three-level hierarchical structure is found accordingly. Then, the cushioning mechanisms are discussed by analyzing the structure–function relationships of the bone tissues. Finally, a structural model of biomimetic composite is proposed based on the authors’ insights into the constitution of cortical bone, which is expected to inspire engineers to design load-bearing structures with excellent mechanical performance.

Biomechanical evaluation of peak reverse torque (PRT) in a dynamic compression plate-screw construct used in a goat tibia segmental defect model

BackgroundPeak reverse torque (PRT) is a valid method to evaluate implants’ secondary stability in the healing bone. The secondary stability is achieved by the implant over time and it has been positively correlated with the implants’ osseointegration level. In other words, peak reverse torque is the force required to break the bone-implant interface. The purpose of this study was to compare the peak reverse torque for the self-tapping and non-self-tapping screws used in a dynamic compression plate–screw–bone construct after 60 days of loading when used to stabilize 2.5-cm defects in the tibia of goats. The second objective was to compare the peak removal torque of the screws placed in the different positions to evaluate the impact of construct biomechanics on implants osseointegration.ResultsIn total, 176 non-self-tapping screws and 66 self-tapping screws were used to fix the 8-holes dynamic compression plates to the bones. The screws were placed in the tibiae from proximal (position sites 1,2, 3) to distal (position sites 4,5,6) and were removed 60 days post-implantation. The animals remained weight-bearing throughout the study period. The screws placed in the proximal diaphysis had significantly less peak reverse torque than screws placed in the distal diaphysis in both groups (p < 0.05). The peak reverse torque resistance was also significantly less for the non-self-tapping screws as compared with the self-tapping screws (p < 0.05). The intracortical fractures in the trans-cortex occurred significantly more frequently during the placement of non-self-tapping screws (p < 0.05) as compared with self-tapping screws (p < 0.05).ConclusionsBased on these results, we concluded that self-tapping screws may be expected to maintain a more stable bone-implant interface during the first 60 days of loading as compared with non-self-tapping screws. This should be a consideration for orthopedic surgeons and scientists using bone plates to stabilize non-load sharing fractures when a stable plate-screw-bone interface is needed to ensure prolonged stability.

Rapid Repair of Goat Large Segmental Loading Bone Defect and Functional Reconstruction by Interventional Micro-Circulation System

Objective: This study aimed to explore the efficacy of interventional micro-circulation system (IMCS), combining the stromal cell-derived factor 1 (SDF-1)/type I collagen/chitosan composite membrane into TEB in treating with the model of goat tibial LSBD. Methods: The model of goat tibial LSBD was constructed by introducing the IMCS and SDF-1 guiding membrane. Perfusion treatment of CXCR4 + -BMSCs and BMP-2 was performed on the animal model, general conditions of the goats were observed, and changes in the goat's tibia was observed at different time points through imaging techniques. Using RNA extraction and reverse transcription, cDNA was acquired. Alkaline phosphatase (ALP), core binding factor-α1 (Cbfα1) and osteocalcin (OC) content, as well as the mRNA of transformation growth factor-β1 (TGF-β1) in fixed bone tissue samples of the goat, were detected by real-time quantitative PCR (RT-qPCR). Results: The model of goat tibial LSBD repaired by IMCS was successfully constructed. The standing, walking and running functions of the goat recovered well after two months; and imaging revealed that the callus was closely connected and most of the scaffold materials of TEB were absorbed. The detection of the ALP gene in bone tissue samples failed, and the amplified product was non-specific. Furthermore, the levels of Cbfα1, OC and mRNA of TGF-β1 were significantly higher than in normal bones (P &lt; 0.05). Conclusion: The combination treatment of IMCS with slow controlled drug delivery systems and TEB functioned well in repairing goat tibial LSBD. This is a novel method for repairing bone defects.

Experimental Study of Cortical Bone Microstructure and Its Toughening Mechanism

With the increasingly severe mechanical environment of the planetary detectors, fracture and failure are more likely to occur at their load-bearing structures. Therefore, it is urgent to improve the toughness of load-bearing structures. Because of the unique microstructures, goat tibia has remarkable toughness. In this investigation, firstly, the cortical bone of goat tibia was observed by SEM, and the characteristic microstructures were identified. Secondly, the cross section of cortical bone was loaded by long-term inplane stress, then the toughness of cortical bone in different regions were obtained based on the orientation and distribution of cracks after the load. Finally, the toughening mechanisms of cortical bone were discussed. This study of the cortical bone toughening mechanism can be helpful for the biomimetic design of high-toughness materials.

Mesenchymal stem cells and porous \u03b2-tricalcium phosphate composites prepared through stem cell screen-enrich-combine(\u2212biomaterials) circulating system for the repair of critical size bone defects in goat tibia

BackgroundEfficacious bone substitute is essential for the treatment of a critical size bone defect. Currently, the bone substitutes commonly used in clinical practice lack osteogenic capacity and the therapeutic efficacy is not ideal. Herein, a novel stem cell screen-enrich-combine(−biomaterials) circulating system (SECCS) was introduced to provide the substitutes with osteogenic ability. The stem cell screening, enrichment, and recombination with substitutes could be integrated during the surgical operation. Using SECCS, the bioactive mesenchymal stem cells (MSCs) and porous β-tricalcium phosphate (β-TCP) composites (MSCs/β-TCP) were rapidly prepared for critical size bone defect repair and validated in goat models of critical size tibia defects.MethodsTwelve goats with right hind limb tibia defects of 30 mm were randomly divided into two groups: six (the experimental group) were treated with MSCs/β-TCP prepared by SECCS and the other six goats (the control group) were treated with pure porous β-TCP. The repair effect was assessed by x-ray, computed tomography (CT), micro-CT, histology and histomorphology 6 months after the operation. In addition, the enrichment efficacy of MSCs and the characteristics of the MSCs/β-TCP prepared by SECCS were evaluated.ResultsThe SECCS could compound about 81.3 ± 3.0% of the MSCs in bone marrow to the porous β-TCP without affecting the cell viability. The average number of MSCs for retransplantation was 27,655.0 ± 5011.6 for each goat from the experimental group. In vitro, satisfactory biocompatibility of the MSCs/β-TCP was performed, with the MSCs spreading adequately, proliferating actively, and retaining the osteogenic potential. In vivo, the defect repair by MSCs/β-TCP with good medullary cavity recanalization and cortical remodeling was significantly superior to that of pure porous β-TCP.ConclusionsThe MSCs/β-TCP prepared through SECCS demonstrated significant therapeutic efficacy in goat models of critical size bone defect. This provides a novel therapeutic strategy for critical size bone defects caused by severe injury, infection, and bone tumor resection with a high profile of safety, effectiveness, simplicity, and ease.

An Effective Negative Pressure Wound Therapy–Compatible Local Antibiotic Delivery Device

The current clinical standard for local antibiotic depot is polymethylmethacrylate (PMMA) beads. Unfortunately, these are not ideal and negative pressure wound therapy (NPWT) reduces their limited effectiveness. Recently, a chitosan sponge has been shown to be an effective carrier of antibiotics. Because it acts as a delivery vehicle with increased wound contact area instead of an antibiotic depot, it may be more effective. The objectives of this study were to determine if (1) a chitosan sponge would be more effective than PMMA beads as a local antibiotic delivery device and (2) the chitosan sponge remains an effective method of delivery when used in conjunction with NPWT. Contaminated musculoskeletal wounds were created on the proximal tibia of goats; the animals were assigned to 1 of 4 groups (bead pouch, beads with NPWT, sponge pouch, and sponge with NPWT). The animals were survived for 48 hours, and the bacteria in the wound were quantified. The antibiotic levels in the blood and within the NPWT canisters were measured throughout the study period. After treatment, there were significantly fewer bacteria in wounds treated with antibiotic chitosan sponge delivery than antibiotic PMMA bead depot (P < 0.05), and NPWT did not reduce the effectiveness of the chitosan sponge even though large amounts of vancomycin was found in the canisters. The peak serum levels of vancomycin were well below what is considered safe levels. Antibiotic delivery to the wound using a chitosan sponge is compatible with NPWT and is more effective than PMMA antibiotic depot. The chitosan sponge works in conjunction with NPWT and may improve the outcomes of open fracture wounds.

Assessing the repair of critical size bone defects performed in a goat tibia model using tissue-engineered constructs cultured in a bidirectional flow perfusion bioreactor

This work evaluated invivo performance of a tissue-engineered bone-like matrix obtained by culturing cell-scaffold constructs in a flow perfusion bioreactor, designed to enable culture of large constructs, envisioning the regeneration of critical-sized defects. A blend of starch with polycaprolactone scaffolds was seeded with goat bone marrow stromal cells (GBMSCs) cultured in the perfusion bioreactor for 14 days using osteogenic medium. Cell seeded scaffolds cultured in static conditions acted as controls. After 14 days, constructs (42 mm length and 16 mm in diameter) were implanted in critical size defects performed in the tibial bone of six adult goats from which the bone marrow had been collected previously. Explants were retrieved after six and 12 weeks of implantation and characterized using scanning electron microscopy, energy-dispersive spectroscopy, micro-computed tomography and radiographic analysis to assess tissue morphology and calcification. Explants were histologically analyzed, using Hematoxylin & Eosin and Masson Trichrome staining. Results provided relevant information about the performance and functionality of starch with polycaprolactone-goat bone marrow stromal cell constructs in a critical size orthotopic defect performed in a large animal model and demonstrated that culture of the starch with polycaprolactone scaffolds with the autologous cells in perfusion culture provide a good therapy for the healing and regenerative process of bone defects.

In vitro and in vivo study of a sodium chloride impregnated microarc oxidation-treated titanium implant surface.

Microarc oxidation (MAO) has been well-documented as an advantageous surface coating technique to improve implant osseointegration. Nevertheless, its strong susceptibility to bacteria critically impedes the development of MAO in clinical trials. Aimed at the efficient inhibition of bacterial invasion of MAO treated titanium (MAO-Ti) implants, a composite coating created by applying sodium chloride (NaCl) on a MAO-Ti implant surface layer was designed herein with the capacity to resist a broad spectrum of bacteria. In the present study, 10% NaCl was impregnated onto an optimized MAO-Ti implant to achieve a composite NaCl-MAO-Ti coating. First, Staphylococcus aureus (S. aureus), a frequently detected pathogen associated with peri-implantitis, was employed as an in vitro model. The visualization and quantification of S. aureus adhering to MAO-Ti and NaCl-MAO-Ti surfaces after incubation for 2, 4 and 24 h was described. Secondly, in an animal experiment, MAO-Ti and NaCl-MAO-Ti implants were placed into the tibia of male goats and these implants remained in situ for 9 weeks. The peri-implant soft tissue reactions, epithelial down growth and microorganisms separated from the inflammatory exudates were assessed during the whole process. The results of the in vitro study revealed that the NaCl-MAO-Ti implant surface significantly decreased the adhesion and multiplication of S. aureus compared to the untreated MAO-Ti. Moreover, the animal experiment established that the NaCl-MAO-Ti implants caused less peri-implant soft tissue infection and ultimately reduced the occurrence of peri-implantitis. Taken together, these data suggest that NaCl impregnated MAO-Ti implant products can effectively lower the risk of peri-implantitis and simultaneously preserve the osseointegration capacity of the MAO coating, which may help facilitate the application of NaCl-MAO-Ti implants in clinic trials.

Negative Pressure Wound Therapy Reduces the Effectiveness of Traditional Local Antibiotic Depot in a Large Complex Musculoskeletal Wound Animal Model

Negative pressure wound therapy (NPWT) has been used to help manage open wounds. Surgeons also often use local antibiotic depot as adjunctive therapy in an effort to reduce infection rates. These 2 techniques have been reported to be used in conjunction, but there are little data to support this practice. We sought to compare the contamination levels of wounds treated with the commonly used antibiotic bead pouch technique to wounds that received both antibiotic beads and NWPT. The effectiveness of a bead pouch was compared with antibiotic beads with NPWT. The anterior compartment and proximal tibia of goats were injured and inoculated with Staphylococcus aureus. Six hours later, the wounds were debrided and the animals were assigned to a group; the bacteria level was quantified immediately before and after initial debridement and 2 days after treatment. The wounds in the antibiotic bead pouch group had 6-fold less bacteria than the augmented NPWT group, 11 ± 2% versus 67 ± 11% of baseline values, respectively (P = 0.01). As expected, high levels of the antibiotic were consistently recovered from the augmented NPWT effluent samples at all time points. NPWT reduces the effectiveness of local antibiotic depot. These results can provide surgeons with the information to personalize the adjunctive therapies to individual patients, with the degree of difficulty in managing the wound and concern for infection being the 2 variables dictating treatment.

Suivi de la déminéralisation osseuse au moyen de réflecteurs de type réseau de Bragg

Estimation of decalcification is a vital tool to discern bone health. Different techniques are used for its quantitative measurement e.g. DEXA, QCT and QUS. All these techniques although non-invasive suffer from limitations such as radiation exposure and inaccurate values. Recently, fiber optic techniques are fast emerging for medical applications owing to their various attractive features like immunity to EMI/RFI, geometric versatility, chemical inertness etc. The effect of decalcification on strain response of a goat tibia was investigated in-vitro using fiber Bragg grating (FBG) sensing technique. The bone was strained by using three points bending technique and corresponding Bragg wavelength shifts were recorded. Two similar bone samples from the same animal were taken and one was partially decalcified. Strain response of decalcified and untreated bone was taken concurrently to monitor the effects of calcium loss and that of degradation with time. The strain generated for same stress increased with greater degree of decalcification and a steep increase occurred after 2 g calcium loss, indicating the onset of damage. The strain response, therefore gives a direct indication of the degree of calcium present in the bone. Level III.

Fiber Bragg grating sensor for monitoring bone decalcification

Estimation of decalcification is a vital tool to discern bone health. Different techniques are used for its quantitative measurement, e.g. DEXA, QCT & QUS. All these techniques, although noninvasive, suffer from limitations such as radiation exposure and inaccurate values. Recently, fiber optic techniques are fast emerging for medical applications owing to their various attractive features like immunity to EMI/RFI, geometric versatility, chemical inertness, etc. The effect of decalcification on strain response of a goat tibia was investigated in vitro using fiber Bragg grating (FBG) sensing technique. The bone was strained by using three-point bending technique and corresponding Bragg wavelength shifts were recorded. Two similar bone samples from the same animal were taken and one was partially decalcified. Strain response of decalcified and untreated bone was taken concurrently to monitor the effects of calcium loss and that of degradation with time. The strain generated for same stress increased with greater degree of decalcification and a steep increase occurred after 2g calcium loss, indicating the onset of damage. The strain response, therefore gives a direct indication of the degree of calcium present in the bone. Level III.

Interface contact profiles of a novel locking plate and its effect on fracture healing in goat

Objective To evaluate the interface characteristics of the new-designed locking plate (LP) and limited contact-dynamic compression plate (LC-DCP) and compare the fracture healing between LP and LC-DCP in a goat tibia fracture model. Methods Eight-hole LP and LC-DCP were applied to fix fresh goat tibiae in a reproducible manner. The average pressure, force and interface contact area were calculated using Fuji prescale pressure sensitive film interposed among the plate and the bone and image analysis system. Eight-hole LP and LC-DCP were applied to each tibia in a goat tibia fracture model. The fracture healing was evaluated by X-ray photography at postoperative 8 weeks. The goats were sacrificed at postoperative 12 weeks. Three-point bending test was conducted in the tibiae. Results The interface contact of LP system was smaller than that of LC-DCP ( P<0.05), while interface contact force of LP system was higher than that of LC-DCP ( P<0.05). Radiographs revealed that the fracture line disappeared in the LP group, while the fracture line was visible in DCP group at postoperative 8 weeks. At postoperative 12 weeks, the bending strength and bending load of fractured tibia were higher in LP group than in DCP group, respectively. Conclusion The new-designed locking plate can significantly decrease the contact area on the bone interface, which further provides better fracture healing than conventional plates.

Repairing goat tibia segmental bone defect using scaffold cultured with mesenchymal stem cells

In this study, we investigated cellular biocompatibility in vitro and segmental bone defect repairing efficacy in vivo of a previously reported fibre-reinforced scaffold, nano-hydroxyapatite/collagen/poly (L-lactic acid) (PLLA)/chitin fibres (nHACP/CF). First, attachment, proliferation, and differentiation of the goat bone mesenchymal stem cells (GBMSCs) cultured on the nHACP/CF scaffolds were evaluated in vitro. The results showed that cells attached to the scaffolds well, and there was no significant difference in cell proliferation between cells on the scaffolds and cells on the polystyrene culture plates that were used as a control. The results also showed that alkaline phosphatase (ALP)/DNA of the cells cultured on the scaffolds was significantly higher than that on the control. The in vivo study compared the bone defect repairing efficacy of nHACP/CF scaffolds with that of autograft bone. Thirty-two adult male goats with 25-mm defects in their tibias at the same anatomic site were divided into four groups. The first group was implanted with the nHACP/CF with GBMSCs. The second group was implanted with autograft bone. The third group was implanted with the nHACP/CF. Nothing was implanted in the fourth group. Bone growth was evaluated by radiography, histology, and biomechanics. The results showed that although the nHACP/CF had new bone formation, it could not repair the defect fully while nHACP/CF with GBMSCs cultured and autograft bone could repair the segmental bone defect by 8 weeks after surgery, suggesting that nHACP/CF is an appropriate scaffold for bone tissue engineering.

The influence of mechanical loading on osseointegration: an animal study

Osseointegration of implant provides a stable support for the prosthesis under functional loads. The timing of loading is a critical parameter that can govern the success of the osseointegration of implant. However, it is not clear whether the early loading can affect the success of osseointegration, or whether the no-loading healing period can be shortened. This paper presents an animal study conducted to investigate how external loads influence the osseointegration at the initial stage of healing. Titanium implants were inserted into the goat tibia laterally, and different axial loadings were applied to the implants in 4 weeks after surgery. After the 2 weeks period of early loading, animals were sacrificed and the tibia bones with the implants were cut off from the bodies. Then mechanical test was employed to find out the differences in the pull-out force, and shear strength at the bone-implant interface between the non-loaded and the loaded implants. The implant-bone interfaces were analyzed by histomorphometric method, SEM (scanning electron micrograph) and EDS (energy density spectrum). The results indicated that the bone-implant interface did not well integrate 4 weeks after surgery, and the fibrous tissue could be found at the interfaces of the specimens without loadings. While the results of loaded specimens with 10 N axial force showed that that parts of the interface were well integrated, indicating that the early mild loading may play a positive role in the process of the osseointegration. The results support that a certain range of external loading would influence the process of osseointegration, and appropriate mechanical loading can be applied to shorten the osseointegration period after surgery.

Repair of segmental bone‐defect of goat's tibia using a dynamic perfusion culture tissue engineering bone

Segmental bone defect resulted from trauma or excision of bone tumor or pathology represents a common and significant clinical problem. In an attempt to solve this dilemma, we use beta-TCP combined with autologous bone marrow mesenchymal stem cells (auto-BMSC) and cultured by dynamic perfusion to repair the segmental bone defects of goat's tibia. The beta-TCP scaffolds combined with auto-BMSC by dynamic perfusion bioreactor or in static state were respectively transplanted into the defect (30 mm) of the goat tibias. The X-ray films were gathered and analyzed at the different time points. At 24 weeks post-operation, tissue engineering bones implanted were analyzed by histology and Micro-CT. Results show that the capacity of osteogenesis in experimental group was higher than that of control group by X-ray, histological, and micro-CT analysis (p < 0.05). According to the study, we found that repair for segmental bone defects of tissue engineering bone cultured by dynamic perfusion culture bioreactor outweigh those cultured in static state. And we can conclude that this technology of tissue engineering bone will become a clinical method to the segmental bone-defects repair in the future.

The Role of Variable Muscle Adaptation to Limb Lengthening in the Development of Joint Contractures

Muscle stiffness and joint contractures are currently regarded as the most common complications of limb lengthening. To better understand the mechanisms of joint contractures, architectural changes of all involved muscles were analyzed in 9 goats after 20% tibial lengthening with standard distraction protocol.All 13 muscles of the goat's tibia were found to be organized into an anterior compartment with 2 longitudinal and 4 pennate muscles and a posterior compartment with 1 longitudinal and 6 pennate muscles. Longitudinal muscles showed better compliance to distraction than pinnate muscles. Although muscle-to-bone lengthening ratio ranged widely (0-1.2), most of the muscles and especially those located in the posterior compartment showed much less lengthening than the bone. Muscular portions of the muscles lengthened more substantially (average, 17%) than their associated tendons (average, 7%). Muscle fiber length changes varied greatly between muscles (range, 0%-88%). Normalization of muscle fiber length revealed considerable elongation of anterior muscles fibers (25%) that was associated with an addition of new sarcomeres in series. Fiber length increase of all posterior muscles but one occurred by stretching of existing sarcomeres, with little addition or even dissolution of sarcomeres in series. This correlated with muscle mass changes showing significant muscle atrophy in the posterior compartment and better mass preservation in the anterior compartment.The study revealed striking difference in response to limb lengthening between individual muscles and muscles from antagonistic compartments in particular. Poor sarcomerogenesis in the posterior muscles leading to their insufficient length increase seems to play major role in the development of joint contractures.