Area Of Bone Ingrowth Research Articles

Optimize the pore size-pore distribution-pore geometry-porosity of 3D-printed porous tantalum to obtain optimal critical bone defect repair capability

The treatment and reconstruction of large or critical size bone defects is a challenging clinical problem. Additive manufacturing breaks the technical difficulties of preparing complex conformation and anatomically matched personalized porous tantalum implants, but the ideal pore structure for 3D-printed porous tantalum in critical bone defect repair applications remains unclear. Guiding appropriate bone tissue regeneration by regulating proper pore size-pore distribution-pore geometry-porosity is a challenge for its fabrication and application. We fabricated porous tantalum (PTa) scaffolds with six different combinations of pore structures using powder bed laser melting (L-PBF) technology. In vitro biological experiments were conducted to systematically investigate the effects of pore structure characteristics on osteoblast behaviors, showing that the bionic trabecular structure with both large and small poress facilitated cell permeation, proliferation and differentiation compared to the cubic structure with uniform pore sizes. The osteogenesis of PTa with different porosity of trabecular structures was further investigated by a rabbit condyle critical bone defect model. Synthetically, T70% up-regulated the expression of osteogenesis-related genes (ALP, COLI, OCN, RUNX-2) and showed the highest bone ingrowth area and bone contact rate in vivo after 16 weeks, with the best potential for critical bone defect repair. Our results suggested that the bionic trabecular structure with a pore size distribution of 200–1200 μm, an average pore size of 700 μm, and a porosity of 70 % is the best choice for repairing critical bone defects, which is expected to guide the clinical application of clinical 3D-printed PTa scaffolds.

Corroboration of coupled musculoskeletal model and finite element predictions with in vivo RSA migration of an uncemented acetabular component.

While finite element (FE) models have been used extensively in orthopedic studies, validation of their outcome metrics has been limited to comparison against ex vivo testing. The aim of this study was to validate FE model predictions of the initial cup mechanical environment against patient-matched in vivo measurements of acetabular cup migration using radiostereometric analysis (RSA). Tailored musculoskeletal and FE models were developed using a combination of three-dimensional(3D) motion capture data and clinical computerized tomography(CT) scans for a cohort of eight individuals who underwent primary total hip replacement and were prospectively enrolled in an RSA study. FE models were developed to calculate the mean modulus of cancellous bone, composite peak micromotion (CPM), composite peak strain (CPS) and percentage area of bone ingrowth. The RSA cup migration at 3 months was used to corroborate the FE output metrics. Qualitatively, all FE-predictedmetrics followed a similar rank order as the in vivo RSA3Dmigration data. The two cases with the lowest predicted CPM (<20 µm), lowest CPS (<0.0041), and high bone modulus (>917 MPa) were confirmed to have the lowest in vivo RSA 3D migration (<0.14 mm). The two cases with the largest predicted CPM (>80 µm), larger CPS (>0.0119) and lowest bone modulus (<472 MPa) were confirmed to have the largest in vivo RSA 3D migration (>0.78 mm). This study enabled the first corroboration between tailored musculoskeletal and FE model predictions with in vivo RSAcup migration. Investigation of additional patient-matched CT, gait, and RSA examinations may allow further development and validation of FE models.

Ability of a novel biomimetic titanium alloy cage in avoiding subsidence and promoting fusion: a goat spine model study

Clinically used intervertebral cages have several bottleneck problems, such as lack of osteogenic properties and high subsidence rate. This research aims to design a novelbiomimetic titaniumalloy cage through three improvements: cross-sectional shape mimics, Young's modulus matches and osteogenic property enhances. Two inner porous structures (1450–200 μm and 800–200 μm) were selected, and the Young's modulus were 540.7 MPa (similar to cancellous bone) and 1139.2 MPa, respectively. Shape of the cages was designed by radiographic images and assistant softwares to make the dense border contact the peripheral cortical bone of the vertebrae. Hydroxyapatite (HA) biocoating was performed through the slurry foaming and impregnation method, and the average thickness was approximately 40 μm. The biocoated and nonbiocoated cages were then implanted in goats’ intervertebral space. During the 6-month follow-up, the lordosis angle and disc space height maintained well in all groups. Histological results showed a significant increase in bone ingrowth area between the nonbiocoating and biocoating groups, meaning a great enhancement of osteogenic properties by HA biocoating. The osseointegration also improved greatly. Additionally, the fusion condition of Young's modulus matching cages, before or after biocoating, was superior to that of unmatched cages. The results demonstrated that biomimetic designs could help avoid subsidence and promote fusion.

Vertical bone augmentation with titanium granule blocks in rabbit calvaria.

To determine whether it is possible to vertically augment bone utilizing a block graft from compressed titanium granules mainly used previously for contained bone defects and to determine whether there exists a difference in osteoconductive properties between the white and the grey granules. In 11 rabbits, 4 titanium blocks were inserted on each rabbit's skull bone according to a randomized scheme. These blocks were made from standardized compressed titanium granules. Type A: PTG grey, small granules (Pourus Titanium Granules, Tigran, Malmö, Sweden); Type B: PTG grey, large granules; Type C: PTG white, small granules; Type D: PTG white large granules. After 12 weeks, the animals were sacrificed and specimens were collected for histology and μCT scanning. From both the μCT and histology, it can be said that bone formation was successfully achieved for all groups, and the granules maintained their volume. The histomorphometric BA (bone area) evaluation in the entire grafted area presented that there were no statistical differences between all groups tested. The lowest 1/4 BA in contact with the rabbit skull presented that groups A and C presented the highest mean BA, and group A presented significantly higher BA than that of group D (p = 0,049). No significant differences were noted between groups A, B and C. Within the limitation of this study, no differences were noted between small white or grey PTG blocks. The large granules presented less bone ingrowth area compared to the small granules and this trend was regardless of the different PTG types. The entire grafted area was not filled with new bone suggesting that bone migration occurred mostly from the existing cortical bone side suggesting contact osteogenesis.

A novel unidirectional porous hydroxyapatite in canines

A novel, unidirectional porous hydroxyapatite with a unidirectional and interconnected pore structure and an average pore size and porosity of 100–300 µm and 75%, respectively, was fabricated using a freeze-casting technique. The authors estimated the osteoconductive capacity and bioresorbable property of unidirectional porous hydroxyapatite following its long-term implantation in four dogs. A cortical bone defect at the proximal tibia and an osteochondral defect through the femur condyle were created. Unidirectional, porous hydroxyapatite was implanted into the each cavity. In the bone-defect model, bone ingrowth in one of the two samples at 1 year postimplantation was observed. In each sample at 2 and 3 years postimplantation, bone ingrowth as well as gradual resorption of unidirectional porous hydroxyapatite and the replacement by the trabecular bone was observed. The bone ingrowth area ratio (per cent of total newly formed bone area/unidirectional porous hydroxyapatite area of each region) was 0 and 36% after 1 year, 28% after 2 years and 49% after 3 years in each dog. In the osteochondral defect model, the resorption of unidirectional porous hydroxyapatite and bone remodeling were noted in all samples. Thus, unidirectional porous hydroxyapatite is bioresorbable and facilitates bone regeneration for several years after intraosseous implantation.

Quantitative Comparison of Osteoconduction between Porous Apatite and Wollastonite-Containing Glass-Ceramics with 5 Different Pore Sizes

Control of the porous morphology and physic- ochemical characteristics of ceramics is important for osteoconduction. In this study, we determined the influence of the porous structure of glass-ceramics that contain apatite and wollastonite (GC-AW) on osteoconduction. For this purpose, we prepared GC-AW cylinders (6 × 15mm) with 5 different pore structures (macropore size, interconnecting pore size, and presence of micropores (pore size, approximately 1µm) for each material were as follows. Material 1000G: 800µm, 150-200µm, ±; material 1000S: 800µm, 175µm, �; material 300G: 250µm, 20µm, and ++; Material 300S: 250µm, 20µm, +; and 200S: 200µm, 50-80µm, �). To evaluate osteoconduction in vivo, these materials were implanted into holes (6mm diameter) made in rabbit femoral condyles. The percentage of bone ingrowth area significantly increased in the case of 300G, 300S, and 200S at 6 and 12 weeks. At 3 weeks after implantation, the rate of bone ingrowth was faster when 1000G, 1000S, and 200S were used than when 300G and 300S were used. These results suggest that GC-AW with a pore size of 800µm is unsuitable for bone growth, and rapid osteoconduction can be achieved at interconnecting pore sizes exceeding 50µm. Further, micropores may not be important for osteoconduction in the case of highly bioactive materials such as GC-AW.

The effect of sol–gel-formed calcium phosphate coatings on bone ingrowth and osteoconductivity of porous-surfaced Ti alloy implants

Ti–6Al–4V implants formed with a sintered porous surface for implant fixation by bone ingrowth were prepared with or without the addition of a thin surface layer of calcium phosphate (Ca–P) formed using a sol–gel coating technique over the porous surface. The implants were placed transversely across the tibiae of 17 rabbits. Implanted sites were allowed to heal for 2 weeks, after which specimens were retrieved for morphometric assessment using backscattered scanning electron microscopy and quantitative image analysis. Bone formation along the porous-structured implant surface, was measured in relation to the medial and lateral cortices as an indication of implant surface osteoconductivity. The Absolute Contact Length measurements of endosteal bone growth along the porous-surfaced zone were greater with the Ca–P-coated implants compared to the non-Ca–P-coated implants. The Ca–P-coated implants also displayed a trend towards a significant increase in the area of bone ingrowth (Bone Ingrowth Fraction). Finally, there was significantly greater bone-to-implant contact within the sinter neck regions of the Ca–P-coated implants.

Bone Formation in the Presence of Phagocytosable Hydroxyapatite Particles

Small particles of biomaterials used in orthopaedic surgery have been shown to induce the resorption of bone. The purpose of this study was to determine whether phagocytosable particles of hydroxyapatite had an adverse effect on bone ingrowth. Bone harvest chambers were implanted bilaterally in the proximal tibial metaphyses of 13 mature rabbits. The bone harvest chamber has a transverse 1-mm wide pore, providing a continuous canal through the chamber for tissue ingrowth. After an initial 6-week period for osseointegration of the bone harvest chambers, the contents of the canal were harvested at 3-or 6-week intervals. Hydroxyapatite particles (diameter, 5 mu) were mixed with a carrier solution, 1% sodium hyaluronate, and implanted in the canal of one chamber in each animal. The contralateral chamber was implanted with the carrier only and served as a control. Histological sections from the tissue harvested from the chambers were evaluated by light microscopy and histomorphometry, and the area of bone ingrowth was measured as a percentage of total area in each section. At 3 weeks there was more bone in the hydroxyapatite sections than in controls; at 6 weeks there was no difference. Hydroxyapatite particles were incorporated within the matrix of new ingrown bone at both time periods. There was no evidence of granuloma formation or inflammation. Previous studies have shown that particles of high density polyethylene and bone cement adversely affect bone ingrowth in this model. The present results suggest that hydroxyapatite particles, small enough to be phagocytosed by macrophages, did not have such effects.