An in vivo study of a bone grafting material consisting of hydroxyapatite and reconstituted collagen

Vascularized Bone Grafting Versus the 2-Stage Masquelet Technique for Upper-Extremity Bone Reconstruction: A Meta-Analysis

PURPOSE

Vascularized bone grafting (VBG) has been described as the technique of choice for larger bone defects in bone reconstruction, yielding excellent results at the traditional threshold of 6 cm as described in the literature. However, we hypothesize that the 2-stage Masquelet technique provides equivalent union rates for upper-extremity bone defects regardless of size, while having no increase in the rate of patient complications.

METHODS

A systematic literature review was conducted using PubMed and Scopus for outcomes after VBG and the Masquelet technique for upper-extremity bone defects of the humerus, radius, ulna, metacarpal, or phalanx (carpal defects were excluded). A meta-analysis was performed to compare outcomes following VBG and the Masquelet technique at varying defect sizes.

RESULTS

There were 77 VBG (295 patients) and 25 Masquelet (119 patients) studies that met inclusion criteria. Patients undergoing the Masquelet technique had defect sizes ranging from 0-15 cm (average 4.5 cm), while patients undergoing VBG had defect sizes ranging from 0-24 cm (average 5.9 cm). The union rate for Masquelet patients was 94.1% with an average time to union of 5.8 months, compared to 94.9% and 4.4 months, respectively, for VBG patients. We did not identify a defect size threshold at which VBG demonstrated a significantly higher union rate. No statistically significant difference was found in union rates between techniques when using multivariable logistic regression analysis.

CONCLUSION

There was no statistically significant difference in union rates between VBG and the Masquelet technique in upper-extremity bone defects regardless of defect size. Surgeons may consider the Masquelet technique as an alternative to VBG in large bone defects of the upper extremity.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Fabrication and characterization of osteogenic function of progenitor cell-laden gelatin microcarriers

Biomaterial-based bone regeneration strategies often include a cellular component to accelerate healing. Modular approaches have the potential for minimally-invasive delivery and the ability to conformally fill complex defects. In this study, spherical gelatin microparticles were fabricated via water-in-oil emulsification and were subsequently crosslinked with genipin. Microparticle diameter depended on impeller geometry, and increased stirring rates consistently produced smaller particles with narrower size distributions. Increasing the concentration of gelatin resulted in larger particles with a broader size distribution. Viscoelastic characterization showed that increased gelatin concentration produced stiffer matrices, though the mechanical properties at lower gelatin concentration were more stable across strain rate. Microparticles of 6.0% wt/vol gelatin were then applied as microcarriers for packed-bed culture of human mesenchymal stromal cells (MSC) at seeding densities of 5.0 × 10³ , 2.5 × 10⁴ , or 5.0 × 10⁴ cells/cm² of surface area, in either control or osteogenic medium. Cell viability was uniformly high (>90%) across seeding densities over 22 days in culture. MSC number stayed approximately constant in the 5.0 × 10³ and 2.5 × 10⁴  cells/cm² samples, while it dropped over time at 5.0 × 10⁴ cells/cm² . Alkaline phosphatase activity was significantly upregulated in osteogenic conditions relative to controls at day 15, and absolute calcium deposition was strongly induced by days 15 and 22. However, calcium deposition per cell was highest in the lowest cell density, suggesting an inhibitory effect of high cell numbers. These results show that genipin-crosslinked gelatin microcarriers can be reproducibly fabricated and used as microcarriers for progenitor cells, which may have utility in treating large and complex bone defects.

Modular microcarrier technologies for cell-based bone regeneration

A variety of materials-based approaches to accelerate the regeneration of damaged bone have been developed to meet the important clinical need for improved bone fillers. This comprehensive review covers the materials and technologies used in modular microcarrier-based methods for delivery of progenitor cells in orthopaedic repair applications. It provides an overview of the field and the rationale for using microcarriers combined with osteoprogenitor cells for bone regeneration in particular. The general concepts and methods used in microcarrier-based cell culture and delivery are described, and methods for fabricating and characterizing microcarriers designed for specific indications are presented. A comprehensive review of the current literature on the use of microcarriers in bone regeneration is provided, with emphasis on key developments in the field and their impact. The studies reviewed are organized according to the broad classes of materials that are used for fabricating microcarriers, including polysaccharides, proteins and peptides, ceramics, and synthetic polymers. In addition, composite microcarriers that incorporate multiple material types or that are mineralized biomimetically are included. In each case, the fabrication, processing, characterization, and resulting function of the microcarriers is described, with an emphasis on their ability to support osteogenic differentiation of progenitor cells in vitro, and their effectiveness in healing bone defects in vivo. In addition, a summary of the current state of the field is provided, as are future perspectives on how microcarrier technologies may be enhanced to create improved cell-based therapies for bone regeneration.

Free vascularized fibula grafting in the operative treatment of malignant bone tumors of the upper extremity: A systematic review of outcomes and complications

BACKGROUND AND OBJECTIVES

Vascularized bone grafting after tumor resection can be an important component in the treatment of bony neoplasms of the upper extremity. The purpose of this study was to determine the outcomes of free vascularized fibula grafting (FVFG) in the treatment of upper extremity sarcomas.

METHODS

A systematic review of the literature of FVFG used in the treatment of upper extremity sarcomas was performed.

RESULTS

A total of 56 studies were included in final analysis. The most common diagnosis was osteosarcoma (35.1%) and the most common recipient site was the humerus (57.3%). FVFG had a median union rate of 93.3%, with the median time to union being 5.0 months. The most common complications were fracture (11.7%), nerve injury (7.5%), infection (5.7%), and hammer toe deformity (3.3%). The reoperation rate was 34.5%. The most commonly reported standardized assessment of clinical outcomes following treatment was the Musculoskeletal Tumor Society Score, which had a median of 80% postoperatively.

CONCLUSIONS

FVFG in the treatment of malignant bony neoplasms of the upper extremity has a high rate of union and good overall outcomes; however, postoperative complication rates are high. A greater degree of standardization is needed in the reporting of patient-centered outcomes to facilitate future comparative studies.

Scaffolds for bone regeneration made of hydroxyapatite microspheres in a collagen matrix

Biomimetic scaffolds with a structural and chemical composition similar to native bone tissue may be promising for bone tissue regeneration. In the present work hydroxyapatite mesoporous microspheres (mHA) were incorporated into collagen scaffolds containing an ordered interconnected macroporosity. The mHA were obtained by spray drying of a nano hydroxyapatite slurry prepared by the precipitation technique. X-ray diffraction (XRD) analysis revealed that the microspheres were composed only of hydroxyapatite (HA) phase, and energy-dispersive x-ray spectroscopy (EDS) analysis revealed the Ca/P ratio to be 1.69 which is near the value for pure HA. The obtained microspheres had an average diameter of 6 μm, a specific surface area of 40 m(2)/g as measured by Brunauer-Emmett-Teller (BET) analysis, and Barrett-Joyner-Halenda (BJH) analysis showed a mesoporous structure with an average pore diameter of 16 nm. Collagen/HA-microsphere (Col/mHA) composite scaffolds were prepared by freeze-drying followed by dehydrothermal crosslinking. SEM observations of Col/mHA scaffolds revealed HA microspheres embedded within a porous collagen matrix with a pore size ranging from a few microns up to 200 μm, which was also confirmed by histological staining of sections of paraffin embedded scaffolds. The compressive modulus of the composite scaffold at low and high strain values was 1.7 and 2.8 times, respectively, that of pure collagen scaffolds. Cell proliferation measured by the MTT assay showed more than a 3-fold increase in cell number within the scaffolds after 15 days of culture for both pure collagen scaffolds and Col/mHA composite scaffolds. Attractive properties of this composite scaffold include the potential to load the microspheres for drug delivery and the controllability of the pore structure at various length scales.

Hierarchically biomimetic scaffold of a collagen-mesoporous bioactive glass nanofiber composite for bone tissue engineering

Mesoporous bioactive glass nanofibers (MBGNFs) were prepared by a sol-gel/electrospinning technique. Subsequently, a collagen-MBGNF (CM) composite scaffold that simultaneously possessed a macroporous structure and collagen nanofibers was fabricated by a gelation and freeze-drying process. Additionally, immersing the CM scaffold in a simulated body fluid resulted in the formation of bone-like apatite minerals on the surface. The CM scaffold provided a suitable environment for attachment to the cytoskeleton. Based on the measured alkaline phosphatase activity and protein expression levels of osteocalcin and bone sialoprotein, the CM scaffold promoted the differentiation and mineralization of MG63 osteoblast-like cells. In addition, the bone regeneration ability of the CM scaffold was examined using a rat calvarial defect model in vivo. The results revealed that CM is biodegradable and could promote bone regeneration. Therefore, a CM composite scaffold is a potential bone graft for bone tissue engineering applications.

The vascularized fibular graft in the pediatric upper extremity: a durable, biological solution to large oncologic defects

Skeletal reconstruction after large tumor resection is challenging. The free vascularized fibular graft (FVFG) offers the potential for rapid autograft incorporation as well as growing physeal transfer in pediatric patients. We retrospectively reviewed eleven pediatric patients treated with FVFG reconstructions of the upper extremity after tumor resection. Eight male and three female patients were identified, including four who underwent epiphyseal transfer. All eleven patients retained a functional salvaged limb. Nonunion and graft fracture were the most common complications relating to graft site (27%). Peroneal nerve palsy occurred in 4/11 patients, all of whom received epiphyseal transfer. Patients receiving epiphyseal transplant had a mean annual growth of 1.7 cm/year. Mean graft hypertrophy index increased by more than 10% in all cases. Although a high complication rate may be anticipated, the free vascularized fibula may be used to reconstruct large skeletal defects in the pediatric upper extremity after oncologic resection. Transferring the vascularized physis is a viable option when longitudinal growth is desired.

Biological response to porcine xenograft implants: an experimental study in rabbits

PURPOSE

The aim of this study was to evaluate the effect of a new porcine biomaterial and collagen paste in 20 New Zealand rabbits.

MATERIALS AND METHODS

Forty implants using a porcine xenograft made up of 80% corticocancellous collagenated bone particles of ≤300 μm in size were placed in the proximal metaphyseal area of both tibiae. Four periods of time were formed: 1h, 5, 8, and 15 months. After implantation, an anteroposterior and lateral radiological study was carried out. Samples were sectioned at 5 μm and stained using hematoxylin-eosin, Masson's trichromic, and Gordon-Switt reticulin stains.

RESULTS

These results confirmed the biocompatibility of this porcine biomaterial-collagen paste; only a few, occasional macrophages and scattered lymphocytes were observed. No fibrosis was observed between the implants and the bone. Moreover, the material was osteoconductive acting as a "scaffold" for bone cells, and there was a progressive increase in bone growth in and around the implants.

CONCLUSION

This new porcine biomaterial-collagen paste seemed to be biocompatible, bioresorbable, and osteoconductive.

Experimental model of bone response to collagenized xenografts of porcine origin (OsteoBiol® mp3): a radiological and histomorphometric study

BACKGROUND

Adequate alveolar ridges are fundamental to successful rehabilitation with implants. There are diverse techniques for reconstructing atrophied ridges, of which bone substitute grafts is one possibility.

PURPOSE

The aim of this study was to carry out radiological and histomorphometric evaluations of bone response to collagenized porcine bone xenografts over a 4-month period following their insertion in rabbits' tibiae.

MATERIAL AND METHODS

Twenty New Zealand rabbits were used. Twenty collagenized porcine bone xenografts (Osteobiol® mp3, Tecnoss Dental s.r.l., Torino, Italy), in granulated form of 600 to 1,000 µm, were inserted in the proximal metaphyseal area of the animals' tibiae and 20 control areas were created. Following implantation, the animals were sacrificed in four groups of five, after 1, 2, 3, and 4 months, respectively. Radiological and histomorphometric studies were made.

RESULTS

After 4 months, radiological images revealed bone defects with a decrease in graft volume and the complete repair of the osseous defect. No healed or residual bone alterations attributable to the presence of the implants were observed. Histomorphometric analysis at 4 months found mean values for newly formed bone, residual graft material, and non-mineralized connective tissue of 25.4 ± 1.8%, 36.37 ± 3.0%, and 38.22 ± 2.5%, respectively. There were no statistical differences in the length of cortical formation with collagenized porcine xenograft (98.9 ± 1.1%) compared with the control samples (99.1 ± 0.7%) at the end of the study period.

CONCLUSIONS

The biomaterial used proved to be biocompatible, bioabsorbable, and osteoconductive and as such, a possible bone substitute that did not interfere with the bone's normal reparative processes.

Apatite content of collagen materials dose-dependently increases pre-osteoblastic cell deposition of a cement line-like matrix

Bone matrix, mainly composed of type I collagen and apatite, is constantly modified during the bone remodeling process, which exposes bone cells to various proportions of mineralized collagen within bone structural units. Collagen-mineralized substrates have been shown to increase osteoblast activities. We hypothesized that such effects may be explained by a rapid secretion of specific growth factors and/or deposition of specific matrix proteins. Using MC3T3-E1 seeded for 32h on collagen substrates complexed with various apatite contents, we found that pre-osteoblasts in contact with mineralized collagen gave rise to a dose-dependent deposit of Vascular Endothelial Growth Factor-A (VEGF-A) and RGD-containing proteins such as osteopontin (OPN) and fibronectin (FN). This RGD-matrix deposition reinforced the cell adhesion to collagen-mineralized substrates. It was also observed that, on these substrates, this matrix was elaborated concomitantly to an increased cell migration, allowing a homogeneous coverage of the sample. This particular surface activation was probably done firstly to reinforce cell survival (VEGF-A) and adhesion (OPN, FN) and secondly to recruit and prepare surfaces for subsequent bone cell activity.

Preparation and characterization of microspheres comprised of collagen, chondroitin sulfate, and apatite as carriers for the osteoblast-like cell MG63

Numerous studies about bone matrix fabrication focus on how the species and concentrations of components affect the cellular response. However, there are few studies that investigate how the related spatial arrangement of the components influences cellular activity. The aim of this work was to develop a novel method to biomimetically manufacture a three-dimensional mineral bone matrix and study the effect of apatite-collagen-chondroitin sulfate (CS) microspheres on the adhesion rate and activity of osteoblast-like cells. Although previous studies used a crosslinking agent or lyophilized methods to fabricated three-dimensional collagen microspheres, we produced beads composed of collagen and CS under mild reaction conditions. This process not only maintains collagen self-assembly into fibrils with a D-periodic pattern ability but also simultaneously introduces two major native bone matrix elements, collagen and CS, into the beads. Furthermore, we mimic the native in vivo bone matrix formation process by the direct nucleation and growth of apatite crystals on collagen fibrils. The apatite crystals are similar in composition to human bone mineral via X-ray diffraction and energy-dispersive X-ray spectrometric analysis. The cellular attachment rate of MG63 osteoblast-like cells is significantly higher for collagen-CS-apatite gel beads than for collagen-CS gel beads. In addition, with regard to the osteoblast bioactivity, we observed that alkaline phosphatase activity of MG63 cells on the collagen-CS-apatite gel beads higher than on the collagen-CS gel beads on day 14.

Free vascularized fibular graft reconstruction of large skeletal defects after tumor resection

Skeletal reconstruction of large tumor resection defects is challenging. Free vascularized fibular transfer offers the potential for rapid autograft incorporation in limbs compromised by adjuvant chemotherapy or radiation. We retrospectively reviewed 30 patients treated with free vascularized fibular graft reconstruction of large skeletal defects after tumor resections (mean defect length, 14.8 cm). The minimum followup was 2 years (mean, 4.9 years; range, 2-15 years). One patient died with liver and lung metastases at 3 years postoperatively. Loss of limb occurred in one patient. Five patients either had metastatic disease (one patient) or had metastatic disease (four patients) develop after treatment, with a mean time to metastasis of 18 months. The overall complication rate was 16 of 30 (53%), with a reoperation rate of 12 of 30 (40%). Union was attained in all 30 grafts. Primary union was attained in 23 (77%) at a mean of 6 months. Secondary union was achieved in seven (23%) after revision fixation and bone grafting; the mean subsequent time to union was 9.2 months, with an index of 1.33 additional operations per patient. Graft fracture (20%) and infection (10%) were other common complications. Despite a high complication rate, free vascularized fibular graft reconstruction offers a reliable treatment of large skeletal defects after tumor resection without increased risk of limb loss, local recurrence, or tumor metastasis.

LEVEL OF EVIDENCE

Level IV, case series. See Guidelines for Authors for a complete description of levels of evidence.

Bone graft materials

This article examines each class of bone grafting material based on some of the studies in each of the following categories: safety, animal research, periodontal and maxillofacial applications, skeletal grafting, and attempts to qualify the efficacy of each class of material. The article also examines some of the research being done in "tissue engineering" to get a sense of the future of bone grafting.

Aqueous microgels for the growth of hydroxyapatite nanocrystals

In present article, we demonstrate that aqueous microgels can be used as containers for the in-situ synthesis of hydroxyapatite. The hydroxyapatite nanocrystals (HAp NCs) become integrated into microgels forming hybrid colloids. The HAp NCs loaded in the microgel can be varied over a broad range. The HAp NCs are localized within the microgel corona. The deposition of the inorganic nanocrystals decreases the colloidal stability of the microgels and leads to particle aggregation at high HAp NCs loading. Because of the strong interactions between HAp NCs and polymer chains, the swelling degree of microgels decreases, and temperature-sensitive properties disappear at high loading of the inorganic component. We demonstrate that hybrid colloids can be used as building blocks for the preparation of nanostructured films on solid substrates.

Microcarriers in the engineering of cartilage and bone

A major problem in tissue engineering is the availability of a sufficient number of cells with the appropriate phenotype for delivery to damaged or diseased cartilage and bone; the challenge is to amplify cell numbers and maintain the appropriate phenotype for tissue repair and restoration of function. The microcarrier bioreactor culture system offers an attractive method for cell amplification and enhancement of phenotype expression. Besides serving as substrates for the propagation of anchorage-dependent cells, microcarriers can also be used to deliver the expanded undifferentiated or differentiated cells to the site of the defect. The present article provides an overview of the microcarrier culture system, its utility as an in vitro research tool and its potential applications in tissue engineering, particularly in the repair of cartilage and bone.