Artificial Bone Research Articles

Efficiency and Heat Production of Ultrasonic Osteotome Strategy in Robot-Assisted Laminectomy.

A biomechanical study. We aimed to assess temperature fluctuations when applying the ultrasonic osteotome during laminectomy and identify the most appropriate cutting method for robot-assisted laminectomy to mitigate the risk of heat-related injuries. Utilizing a robotic system for laminectomy, the study implemented the ultrasonic bone scalpel to cut both artificial polyurethane bones and animal spinal bones. The research focused on comparing and analyzing the maximum temperature of the inner surface of four types of artificial bones through three different cutting techniques: vertical constant cutting at speeds of .5mm/s and 1mm/s, as well as robot-assisted vertical reciprocating cutting. After the initial results, two optimal vertical cutting approaches were selected for subsequent trials, evaluating the effectiveness and temperature impact of various ultrasonic osteotome modes on 10 isolated spinal bones from pigs. When cutting polyurethane bones, reciprocating cutting demonstrated the lowest maximum temperature in contrast to constant speed cutting at .5mm/s and 1mm/s. In the animal bone trial, direct cutting registered an average maximum temperature of 43.25°C with an average cutting duration of 688.3s, while reciprocating cutting recorded an average maximum temperature of 34.20°C with an average cutting time of 713.0s. The reciprocating cutting strategy utilized in robot-assisted ultrasonic osteotome is effective in reducing heat generation and maintaining high cutting efficiency.

Initial construct stability of long cephalomedullary nails with superior locking for a complex trochanteric fracture model AO31A2.2- a biomechanical study.

Complex fractures of the trochanteric region, as well as fractures located in the directly subtrochanteric region, are controversially discussed around the world regarding the nail type to be used. A long nail is recommended by manufacturers but requires longer surgical and fluoroscopy times. A possible solution could be a nail with an appropriate length which can be locked in a minimally invasive manner by the main aiming device. We aimed to determine if such a nail model (DCN SL nail, SWEMAC, Linköping, Sweden) offers similar structural stability on biomechanical testing on artificial bone as a standard long nail when used to treat complex trochanteric fractures and compared it to long nails usually used in this setting. An osteoporotic bone model was chosen. The Swemac Hansson DCN Nail System was used as osteosynthesis material. Two types of nails were chosen: a superior lock nail which can be implanted with a singular targeting device, and a long nail with distal locking using free-hand technique. AO31A2.2 fractures were simulated in a standardised manner. Axial height of the construct, varus collapse, and rotational deformity directly after nail insertion were simulated. A Universal Testing Machine was used. Measurements were made with a stereo-optic tracking system. There was a detectable difference in the axial fracture movement resulting in narrowing of the fracture gap. There was no difference in varus collapse or rotational deformity between the nail variants CONCLUSION: We conclude that there are small differences which are clinically insignificant and that a superior locking nail can safely be used to manage complex trochanteric fractures.

A critical comparative study of the performance of three AI-assisted programs for bone age determination.

To date, AI-supported programs for bone age (BA) determination for medical use in Europe have almost only been validated separately, according to Greulich and Pyle (G&P). Therefore, the current study aimed to compare the performance of three programs, namely BoneXpert, PANDA, and BoneView, on a single Central European population. For this retrospective study, hand radiographs of 306 children aged 1-18 years, stratified by gender and age, were included. A subgroup consisting of the age group accounting for 90% of examinations in clinical practice was formed. The G&P BA was estimated by three human experts-as ground truth-and three AI-supported programs. The mean absolute deviation, the root mean squared error (RMSE), and dropouts by the AI were calculated. The correlation between all programs and the ground truth was prominent (R2 ≥ 0.98). In the total group, BoneXpert had a lower RMSE than BoneView and PANDA (0.62 vs. 0.65 and 0.75 years) with a dropout rate of 2.3%, 20.3% and 0%, respectively. In the subgroup, there was less difference in RMSE (0.66 vs. 0.68 and 0.65 years, max. 4% dropouts). The standard deviation between the AI readers was lower than that between the human readers (0.54 vs. 0.62 years, p < 0.01). All three AI programs predict BA after G&P in the main age range with similar high reliability. Differences arise at the boundaries of childhood. Question There is a lack of comparative, independent validation for artificial intelligence-based bone age estimation in children. Findings Three commercially available programs estimate bone age after Greulich and Pyle with similarly high reliability in a central European cohort. Clinical relevance The comparative study will help the reader choose a software for bone age estimation approved for the European market depending on the targeted age group and economic considerations.

On propagation characteristics of ultrasonic guided waves in layered fluid-saturated porous media using spectral method.

Fluid-saturated porous media plays an increasingly important role in emerging fields such as lithium batteries and artificial bones. Accurately solving the governing equations of guided wave is the key to the successful application of ultrasonic guided wave nondestructive testing technology in fluid-saturated porous media. This paper derives the Lamb wave equation in layered fluid-saturated porous materials based on Biot theory and proposes the spectral method suitable for solving complex wave equations. The spectral method reconstructs the fundamental wave equations in the form of a matrix eigenvalue problem using spectral differentiation matrices. It introduces boundary conditions by replacing corresponding rows in the wave equation matrix with stress or displacement in matrix form. For complex differential equations, such as the governing equations of guided waves in porous media, the spectral method has the significant advantages of faster computation speed, less root loss, and easier encoding process. The spectral method is used to calculate the acoustic field characteristics under different boundary conditions and environments of the layer fluid-saturated porous media. Results show that the surface treatment details and environment of fluid-saturated porous materials play an important role in the propagation of guided waves.

Distribution of bone fragments in angled shots: an experimental study conducted on composite models containing artificial bone plates.

In conventional gunshot injuries to targets containing bone the resulting osseous fragments do not precede but follow the bullet on its further way through adjacent soft tissues. The term "secondary projectiles" for the particles does not appear to be appropriate since they are not believed to have enough energy necessary for creating their own wound channels away from the temporary cavity. Former studies have shown that in angled shots to glass panes the bulk of splinters does not follow the bullet's trajectory: The majority of the glass fragments, especially the larger ones, move at right angles to the pane shot through. The aim of the presented study was to examine whether osseous fragments behave like glass splinters in angled shots to flat synthetic bone. In this context, it should also be assessed, whether the bone fragments might act as secondary projectiles in rare cases. To answer these questions, test shots were fired to composite models consisting of flat synthetic bone and ballistic gelatin. Pistol cartridges 9mm Luger were used to fire the shots which were video-documented with a high-speed camera. Afterwards, the composite models underwent CT examination and macroscopic inspection. Video-documentation revealed that the larger bone particles from the perforation site move at a roughly right angle from the osseous sheet into the gelatin, causing an eccentric bulge of the temporary cavity. The smaller bone fragments were also lodged along the bullet's path, predominantly in the cracks radiating from the permanent wound channel.

Five states of reduction in OTA/AO A1.3 intertrochanteric fractures of the femur a biomechanical study

ObjectiveThis study aims to analyze the differences in mechanical stability of OTA/AO 31A1.3 intertrochanteric fractures under various reduction conditions.MethodsTwenty standard synbone artificial femur test bones were selected for the OTA/AO 31A1.3 intertrochanteric fracture model. The models were divided into five groups according to their reduction state: positive support, neutral support, negative support, varus fixation, and valgus fixation, with four specimens in each group. All models were fixed using PFNA intramedullary fixation and subjected to static axial compression tests. The subsidence displacement of the proximal femur under different loads and the axial stiffness of the model were measured to verify the mechanical stability of the OTA/AO 31A1.3 intertrochanteric fracture under different reduction conditions.ResultsAfter the static axial compression test, the proximal femoral subsidence displacement in the positive support and neutral support groups was lower than that in the negative support, valgus fixation, and varus fixation groups (p < 0.001). The axial stiffness of the model was highest in the positive support group. Significant differences in subsidence displacement and axial stiffness were found between the groups (p < 0.001). The positive support group demonstrated the best mechanical stability, while the varus fixation group showed the poorest performance.ConclusionPositive support of the medial cortex can be regarded as the best reduction state for OTA/AO 31A1.3 intertrochanteric fractures, suggesting that this approach should be preferred during surgery to enhance mechanical stability and improve clinical outcomes. Conversely, varus fixation should be avoided due to its inferior stability.

A study on the effect of platelet-rich plasma (PRP) to promote bone fusion in lateral interbody fusion of the lumbar spine using artificial bone

BackgroundLateral lumbar interbody fusion (LLIF) via a retroperitoneum approach has gained popularity due to minimal invasiveness, which avoids resection of the spinous process and laminae. However, as challenges in grafting autogenous bone persist, artificial bone has been tested in Japan to fill the spinal cage. Platelet-rich plasma (PRP) contains growth factors and anti-inflammatory cytokines to promote cellular proliferation and repair damaged tissues. While the effects of PRP on tendon and ligament repair are widely known, any effects on bone healing are scarcely reported. However, PRP-loaded artificial bone carries potential to improve intervertebral bone fusion.ObjectiveThis study assessed whether PRP enhances intervertebral bone fusion in LLIF surgery using β-tricalcium phosphate artificial bone.MethodsThe current study was a prospective, randomized, controlled trial. We evaluated 13 consecutive patients undergoing LLIF surgery in our hospital. Patients received artificial bone impregnated with PRP or without PRP within the same fusion cage. The primary outcome was the intervertebral bone fusion rate at 6 and 12 months postoperatively, evaluated using CT imaging. The intervertebral bone fusion rates with and without PRP loading and with and without contact part between the endplate and the artificial bone were compared. Secondary outcomes included clinical evaluations using visual analog scale scores for low back pain, buttock-leg pain, and leg numbness from the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOA-BPEQ) and the Oswestry Disability Index (ODI), plus adverse events information.ResultsOf the 13 patients (29 vertebral segments) included, bone fusion was observed in 43.4% of the PRP group and 26.1% of the non-PRP group at 6 months (p = 0.216). At 12 months, fusion rates were 60.9% with PRP and 34.8% without PRP (p = 0.074). The fusion rate was significantly higher in cases with good contact between the vertebral endplate and the artificial bone (p = 0.0004). Clinical scores improved postoperatively. Adverse events were in accordance with expectations from LLIF surgery and no PRP-specific events occurred.ConclusionPRP did not significantly improve intervertebral bone fusion rates in LLIF surgeries, particularly in cases with poor contact between the vertebral endplate and artificial bone. While PRP may have a limited role in enhancing bone fusion, maintaining good contact between the vertebral endplate and artificial bone is crucial for successful outcomes. Further research is needed to explore optimal uses of PRP in spinal fusion surgeries.

Face and Content Validation of Artificial Temporal Bone Dissection for Otolaryngology Training.

Face and Content Validation of Artificial Temporal Bone Dissection for Otolaryngology Training.

Hydroxyapatite/Silk Fibroin Composite Scaffold with a Porous Structure and Mechanical Strength Similar to Cancellous Bone by Electric Field-Induced Gel Technology.

Repair and regeneration of bone tissue defects is a multidimensional process that has been highly challenging to date. The artificial bone scaffold materials, which play a core role, still face the conflict that a biofriendly porous structure will reduce the mechanical performance and accelerate degradation. Herein, a multistage porous structured hydroxyapatite (HA)/silk fibroin (SF) composite scaffold (e-HA/SF) was successfully constructed by cleverly utilizing electric field-induced gel technology. The results indicated that the prepared e-HA/SF scaffolds possess biomimetic hierarchical porous structures with a suitable porosity similar to that of cancellous bone. The HA nanocrystals were uniformly encapsulated in the three-dimensional space of the composite scaffold, thus endowing the e-HA/SF composite scaffolds with an enhanced mechanical performance. Notably, the maximum compression stress and Young's modulus of e-HA/SF-2 scaffolds can reach 24.66 ± 0.88 and 28.91 ± 3.19 MPa, respectively, which are equivalent to those of cancellous bone. Such mechanical performance enhancement was previously unattainable through conventional freeze-drying strategies. Moreover, the introduction of bioactive nano-HA can trigger the optimal cell response in both static and dynamic cell culture experiments in vitro. The e-HA/SF composite scaffold developed in this study can better balance the conflict between the porous structure and mechanical and degradation properties of porous scaffolds.

Study of thermal stress deformation in hybrid 3D printing and milling process of PEEK material

Hybrid manufacturing can enable rapid production of personalized artificial bones that are made of Polyether-ether-ketone (PEEK) by integrating 3D printing and milling. A main challenge, however, is the thermal stress deformation that arises from the fused deposition process, leading to warping and shrinkage. As a result, the fabrication accuracy is significantly diminished. This work aims to address this challenge by investigating the thermal stress deformation behavior of PEEK in hybrid manufacturing. The main contributions of this work, therefore, include the development of a model for this thermal deformation behavior, and the identification of key parameters such as cross-section length ( Ls), printed layer thickness ( Lh), and current workpiece height ( He). Further, experiments are conducted based on response surface methodology (RSM) to explore the relationships between temperature variation rate (Δ T), end surface height difference (Δ S), and length shrinkage rate (Δ L) with critical hybrid processing parameters. Optimal parameter combinations are then identified. Our experiments demonstrate that the proposed methods effectively reduce the effects of warping and shrinkage.

Plane dilatational and shear waves in a chiral porous thermoelastic medium under strain gradient theory

Purpose This study aims to investigate time-harmonic wave propagation in a chiral porous thermoelastic solid under strain gradient theory (SGT), focusing on identifying and characterizing distinct wave modes within the medium. Design/methodology/approach Using Iesan's gradient theory, which incorporates chiral effects and accommodates second sound phenomena, the authors derive mathematical formulations for the velocities and attenuations of eight propagating waves: four dilatational waves and two pairs of coupled shear waves (one left circularly polarized, the other right). Numerical simulations are performed for a specific model, exploring the influence of various parameters on wave propagation. Findings The authors establish that the medium supports four dilatational waves, including a microstretch-associated wave, and four shear waves, distinguished by their chiral-induced characteristics. The results highlight the frequency-dependent dispersive nature of all propagating waves and establish connections with existing theoretical frameworks, demonstrating the broader applicability of our findings. Practical implications The characteristics of wave propagation in chiral media examined here can enhance our understanding of chiral medium behavior. This knowledge is crucial for developing materials with pronounced chiral effects, surpassing those found in natural chiral materials like bone, quartz, sugar and wood. Advances in artificial chiral materials are driven by their superior toughness, durability and other beneficial properties. Consequently, this study has potential applications across various fields, including the design of chiral broadband absorbers and filters, the production of artificial bones and medical devices, aeronautical engineering and beyond. Originality/value This research extends existing theories and deepens the understanding by exploring wave behaviors in chiral media, advancing this emerging field.

Hydrothermal synthesis of bioactive calcium silicate glass

This work presents the synthesis of bioactive glass 60SiO2-40CaO (wt.%) by the hydrothermal method without using acid catalysts in shortened synthesis time. The precursors Si(OC2H5)4 (TEOS), Ca(NO3)2.4H2O were introduced in a hydrothermal system, and heated at 150 oC for 24 hours. The resulting gel was dried at 150 oC for 24 hours, then calcined at 800 oC for 3 hours to achieve bioactive glass. Several physical-chemical methods such as TG-DSC, XRD, SEM, and ICP-OES were used to evaluate the synthetic material. The bioactivity and biocompatibility of synthetic glass were evaluated by in vitro experiments in SBF solution and in cell culture environment. The obtained results show that the synthetic glass is an amorphous material, presenting the bioactivity through the formation of a hydroxyapatite mineral layer after 10 days of soaking in SBF solution, and also showing good biocompatibility with cells L-929. Keywords: Bioactive glass, bioactivity, artificial bone, hydroxyapatite, cell viability

Modeling acoustic characteristics of artificial bone alloys for medical and surgical use under thermodynamic conditions

The study examines the impact of porosity on mechanical, acoustic, and behavioral properties of (Ti-6Al-4 V alloy) alloys, which are manufactured to mimic human bones. It investigates how porosity, controlled through factors like pressure, particle size, and temperature during sintering, affects properties such as modulus of elasticity, surface acoustic wave (SAW) velocities, hardness coefficients, and acoustic resistance.The findings suggest that different levels of porosity at varying sintering temperatures significantly alter the dynamic elastic modulus of the alloys. Specifically, increasing porosity values seem to correlate with a decrease in elastic constants, elastic modulus values, and surface acoustic wave types. This phenomenon may be attributed to the transitional crystalline structure phases of Ti6Al4V alloy and the manufacturing process.Remarkably, the study concludes that these (Ti-6Al-4 V alloy) alloys exhibit superior porosity, mechanical, and acoustic qualities compared to various types of human bone, including cortical, trabecular, and cancellous bone.

Analysis of the Complications of Mandibular Cortical Bone with/without Particulate Artificial Bone Graft for Alveolar Cleft Reconstruction: A Retrospective Study

Analysis of the Complications of Mandibular Cortical Bone with/without Particulate Artificial Bone Graft for Alveolar Cleft Reconstruction: A Retrospective Study

Thermal Evaluation of Bone Drilling: Assessing Drill Bits and Sequential Drilling.

Sequential drilling is a common practice in dental implant surgery aimed at minimizing thermal damage to bone. This study evaluates the thermal effects of sequential drilling and assesses modifications to drilling protocols to manage heat generation. We utilized a custom drill press and artificial bone models to test five drill bits under various protocols, including sequential drilling with different loads, spindle speeds, and peck drilling. Infrared thermography recorded temperature changes during the drilling process, with temperatures monitored at various depths around the osteotomy. The results reveal sequential drilling does not eliminate the thermal damage zone it creates (well over 70 °C). It creates harmful heat to surrounding bone that can spread up to 10 mm from the osteotomy. The first drill used in sequential drilling produces the highest temperatures (over 100 °C), and subsequent drill bits cannot remove the thermal trauma incurred; rather, they add to it. Modifying drill bit design and employing proper drilling techniques, such as reducing drilling RPM and load, can reduce thermal trauma by reducing friction. Inadequate management of heat can lead to prolonged recovery, increased patient discomfort, and potential long-term complications such as impaired bone-to-implant integration and chronic conditions like peri-implantitis. Ensuring healthy bone conditions is critical for successful implant outcomes.

Compressive behavior of SLA open-cell lattices: A comparison between triply periodic minimal surface gyroid and stochastic structures for artificial bone

This study evaluates the compressive properties of stereolithography (SLA) fabricated open-cell lattices, specifically triply periodic minimal surface (TPMS) gyroid and stochastic structures, for artificial bone applications. Two resins, Standard White and BioMed Amber, were tested across four relative densities (0.2, 0.3, 0.4, 0.5). Mechanical characterization of horse tuber coxae trabecular bone used as a biological comparator showed an average elastic modulus of 0.05 GPa and a yield strength of 3.369 MPa. Gyroid structures exhibited higher elastic modulus and yield strengths, with BioMed Amber gyroid at a density of 0.5, achieving an elastic modulus of 0.623 GPa and yield strength of 14.149 MPa. Stochastic structures showed lower and more variable mechanical properties. The highest yield strength for stochastic structures was observed in BioMed Amber at a density of 0.5 (14.199 MPa). Comparative analysis indicated that high-performing synthetic structures approach the lower bounds of natural bone properties. Using a field-driven design approach, variable relative density structures were developed to emulate the mechanical properties of natural bone. SEM analysis provided insights into failure mechanisms, highlighting the impact of relative density on structural integrity and material ductility. This research supports the development of 3D-printed bone-like structures as viable substitutes for cadaveric specimens in preclinical tests, with implications for material science and orthopedic applications.

Assessment of artificial bone materials with different structural pore sizes obtained from 3D printed polycaprolactone/β-tricalcium phosphate (3D PCL/β-TCP)

Artificial bone is the alternative candidate for the bone defect treatment under the circumstance that there exits enormous challenge to remedy the bone defect caused by attributes like trauma and tumors. However, the impact of pore size discrepancy for regulating new bone generation is still ambiguous. Using direct 3D printing technology, customized 3D polycaprolactone/β-tricalcium phosphate (PCL/β-TCP) artificial bones with different structural pore sizes (1.8, 2.0, 2.3, 2.5, and 2.8 mm) were successfully prepared, abbreviated as the 3D PCL/β-TCP. 3D PCL/β-TCP exhibited a 3D porous structure morphology similar to natural bone and possessed outstanding mechanical properties. Computational fluid dynamics analysis indicated that as the structural pore size increased from 1.8 to 2.8 mm, both velocity difference (from 4.64 × 10-5to 7.23 × 10-6m s-1) and depressurization (from 7.17 × 10-2to 2.25 × 10-2Pa) decreased as the medium passed through.In vitrobiomimetic mineralization experiments confirmed that 3D PCL/β-TCP artificial bones could induce calcium-phosphate complex generation within 4 weeks. Moreover, CCK-8 and Calcein AM live cell staining experiments demonstrated that 3D PCL/β-TCP artificial bones with different structural pore sizes exhibited advantageous cell compatibility, promoting MC3T3-E1 cell proliferation and adhesion.In vivoexperiments in rats further indicated that 3D PCL/β-TCP artificial bones with different structural pore sizes promoted new bone formation, with the 2.5 mm group showing the most significant effect. In conclusion, 3D PCL/β-TCP artificial bone with different structural pore sizes could promote new bone formation and 2.5 mm group was the recommended for the bone defect repair.

Heat Generation during Dental Implant Bed Preparation Using Surgical Guides with and without Internal Irrigation Channels Evaluated on Standardized Models of the Alveolar Bone

Dental implant bed preparation involves surgical drilling. Heat generated in this process can cause a temperature elevation beyond the bone damage limit (10 °C), affecting the osseointegration of the implant. Surgical templates ensure accurate implant placement, but they limit the access of the irrigation fluid. This study evaluated the hypothesis that surgical guides with internal cooling prevent bone heating more effectively than classical guides. To eliminate biological variability, this study was conducted on artificial bone pieces that mimic the bone density of the human mandible. We created a surgical template that incorporated four pairs of guides—one classical (CLA) and one with internal cooling (INT) in each pair. For each specimen, we randomly selected the type of surgical guide to start with and performed four osteotomies with a 2.7 mm-diameter drill; then, we widened each hole with a 3.3 mm drill and finalized it with a 3.7 mm drill. The temperature was recorded by thermocouples placed at 0.8 mm from the prospective edge of the final osteotomy. In 168 measurements (12 osteotomies on 14 specimens) conducted for each type of surgical guide, the mean temperature rise was 7.2 ± 4.9 °C (mean ± standard deviation) for CLA and 5.0 ± 3.8 °C for INT. The mean differences between temperature elevations were 1.5 °C, 2.1 °C, and 3.0 °C for the first, second, and third drill, and they were statistically significant: the p-values of Student’s t-test were 0.004, 0.01, and 0.001, respectively. Although the mean temperatures remained safe, temperature rises exceeded 10 °C in 23.8% (9.5%) of the osteotomies performed in the presence of CLA (INT). Taken together, our results suggest that surgical guides with internal cooling ensure a significant drop in the temperature rise caused by implant site drilling.

The Effect of Increasing Thread Depth on the Initial Stability of Dental Implants: An In Vitro Study

Background: The long-term success of dental implants largely depends on achieving primary stability, previously described as crucial to obtaining osseointegration and immediate loading protocol requirements. Implant thread depths seem to be one of the key factors influencing primary stability, particularly in low-density bone. Insertion torque (IT) and resonance frequency analysis (RFA) are considered the most reliable tests to assess primary stability. The aim of this work was to evaluate how different thread depths of commercially available dental implants affect primary stability in low-density D3 bone. Materials and Methods: An in vitro study was carried out between February 2024 and March 2024. Twenty-four dental implants were divided into four groups (six implants each) according to their thread depths (Group A: 4 mm, Group B: 4.5 mm, Group C: 5 mm, Group D: 5.5 mm) and were inserted in D3-type artificial bone blocks. The main outcome variables were the IT and the Implant Stability Quotient (ISQ) measured in four different areas of the implant (buccal, lingual, mesial, and distal) with an Osstel® ISQ reader. Descriptive and inferential analyses of the data were performed, and the significance value was set at 5%. Results: A total of 24 implants were analyzed. The highest IT values were obtained in Group D, with a mean of 54.03 Ncm (standard deviation (SD) = 8.99), while the lowest measurements were observed in Group A (mean = 25.12; SD: 2.96 N.cm). The mean ISQ values were consistently higher in Group D for each analyzed area, with a mean of 70.13 N.cm (SD = 1.12). Conclusions: Taking into consideration the limitations of this in vitro study, greater thread depths seem to increase the primary stability of dental implants placed in soft bone. Furthermore, a positive correlation was observed between all IT and ISQ values, regardless of the thread depth.

Controlling the pore size of carbonate apatite honeycomb scaffolds enhances orientation and strength of regenerated bone

To restore functions of long bones and avoid reconstruction failure, segmental defects should be quickly repaired using abundant amounts of regenerated bone with high mechanical strength and orientation along the bone axis. Although both bone volume and bone matrix orientation are important for faster restoration of long bones with segmental defects, researchers have primarily focused on the former. Artificial bone scaffolds with uniaxial channels, (e.g., honeycomb (HC) scaffolds), are considered adequate for regenerating bone oriented along the bone axis. The channel size may affect the orientation, amount, and strength of the regenerated bone. In this study, we investigated the effects of channel size in carbonate apatite HC scaffolds on the orientation of bones regenerated in segmental bone defects and determined the adequate channel size. Carbonate apatite HC scaffolds, with different channel sizes (350, 550, 730, and 890 μm in length on the side of the square aperture), were fabricated by extrusion molding of a mixture of calcium carbonate and organic binder, debinding, and subsequent phosphatization to convert the composition from calcium carbonate to carbonate apatite. No significant difference in the amounts of regenerated bones was observed for different channel sizes. However, bone along the bone axis was formed in the channels ≤550 μm in size but not in channels ≥730 μm. The HC scaffolds with a channel size of 350 μm regenerated bone with higher bending strength than those with a channel size of 890 μm. However, bone regenerated with the HC scaffolds having channel sizes of 350, 550, and 730 μm showed equal bending strength. Thus, the adequate channel size for fast regeneration of high-strength bone, oriented to the bone axis, is ≤730 μm. To the best of our knowledge, this is the first study to report the effect of channel size on bone orientation and strength. The findings of this study are relevant to the fast repair of segmental bone defects.