Autologous bone graft versus demineralized bone matrix in internal fixation of ununited long bones

The effects of allogeneic and xenogeneic lyophilized leukocyte-and platelet-rich fibrin on bone healing in rat

BACKGROUND

Critical size defects are one of the challenges in the treatment of fractures in humans and animals. Blood products such as leukocyte-SAand platelet-rich fibrin (L-PRF) are one of the alternatives to bone autograft to solve this challenge. This study aims to evaluate the effects of allogeneic and xenogeneic lyophilized L-PRF on bone healing in a critical defect of radius bone in rat.

METHODS

A defect with a diameter of 5 mm was created in the radius bone of 60 rats in four groups. The defect was left empty in the untreated group, and it was filled with autogenous bone graft, allogeneic, and xenogeneic lyophilized L-PRF, respectively, in the other three groups. Radiographic evaluation was done every two weeks, and histopathological evaluation in the 14th, 28th, and 56th days after surgery.

RESULTS

The radiographic scores of allogeneic and xenogeneic lyophilized l-PRF groups were significantly higher than the untreated group in all times (P<0.05). In connection with histopathological Emery's scoring system, the score of allogeneic lyophilized L-PRF was significantly higher than the untreated group (P<0.05) in the 14th and 28th days after surgery. The score of the xenogeneic lyophilized L-PRF group was also higher than the untreated group, but the difference was not significant (P>0.05). The allogeneic and xenogeneic lyophilized L-PRF scores were significantly higher than the untreated group (P < 0.05) on the 56th day.

CONCLUSION

The results of the present study showed that the allogeneic and xenogeneic lyophilized L-PRF can improve bone healing in the critical radius bone defect in rat model of study.

Bone Regeneration in a Large Animal Model Featuring a Modular Off-the-Shelf Soft Callus Mimetic

Implantation of engineered cartilage with soft callus features triggers remodeling to bone tissue via endochondral bone regeneration (EBR). Thus far, EBR has not progressed to the level of large animals on the axis of clinical translation. Herein, the feasibility of EBR is aimed for a critical-sized defect in a large animal model. Chondrogenesis is first induced in goat-derived multipotent mesenchymal stromal cells (MSCs) by fine-tuning the cellular differentiation process. Through a unique devitalization process, two off-the-shelf constructs aimed to recapitulate the different stages of the transient cartilaginous soft callus template in EBR are generated. To evaluate bone regeneration, the materials are implanted in an adapted bilateral iliac crest defect model in goats, featuring a novel titanium star-shaped spacer. After 3 months, the group at the more advanced differentiation stage shows remarkable regenerative capacity, with comparable amounts of bone regeneration as the autograft group. In contrast, while the biomaterial mimicking the earlier stages of chondrogenesis shows improved regeneration compared to the negative controls, this is subpar compared to the more advanced material. Concluding, EBR is attainable in large animals with a soft callus mimetic material that leads to fast conversion into centimeter-scale bone, which prospects successful implementation in the human clinics.

Clinical parameters and radiographic resorption of a novel magnesium based bone void filler

BACKGROUND

Bone voids can present challenging problems for the Orthopaedic surgeon, and are often treated with backfilling followed by structural stabilization. Recently, a magnesium based, and presumably resorbable, bone void filler (BVF) has been developed, but has limited longitudinal clinical data. Therefore, the purpose of this study was to investigate clinically relevant parameters and radiographic resorption characteristics of this novel magnesium based BVF (MgBVF) with long-term clinical data.

METHODS

All patients who underwent surgery by a single surgeon in which MgBVF was utilized from 2019 to 2020 were retrospectively reviewed. Clinical parameters including evidence of infection, wound breakdown, and wound drainage were reviewed. Radiographic resorption, evidence of joint extrusion of BVF, heterotopic ossification, and subsidence was assessed at each post-operative visit. Those with less than 6 month follow up were excluded from radiographic analysis of resorption. Postoperative images at two weeks were compared to each subsequent radiograph during follow up, and reviewed by each of the three authors in blinded fashion. Interval radiographs were assigned a grade of radiographic resorption which corresponded to estimated percent resorption: grade 1 (0-25%), grade 2 (25-50%), grade 3 (50-75%), or grade 4 (75-100%). After 2 weeks, this process was repeated, and both inter and intraobserver reliability scores were calculated.

RESULTS

Forty-two patients were identified for clinical review, and 18 for radiographic review. Average length of follow up was 209±113 days. Five patients experienced a postoperative complication: two wound infections, one delayed wound healing, one sterile serous drainage, and one catastrophic failure of the fixation construct. Four patients were noted to have postoperative joint subsidence of 2 mm or less. Average grade of resorption was found to be 1.5 ± 0.8, 1.7 ± 0.9, 2.9 ± 0.9, and 3.6 ± 0.6 at 6 weeks, 3 months, 6 months, and 1 year, respectively (p<0.001). Average kappa (intrarater reliability) was found to be 0.61, 0.41, 0.55, and 0.63 for each time interval, respectively. Interrater reliability increased form 0.19 at 6 weeks to 0.42 at 1 year.

CONCLUSION

This novel MgBVF demonstrates clinically relevant resorption, provides structural support in challenging bone voids, and does not appear to significantly increase risk of complications, setting it apart from previously described BVF's.

Exchange nailing and medial wall reconstruction following implant failure in a subtrochanteric femoral fracture

Failure of fixation of subtrochanteric fractures has been reported in as high as 20% of cases. Several associations have been suggested to contribute to failed fixation. Discontinuity of the medial wall/column is considered to be one of the most significant risk factors for non-union and subsequent implant failure, especially if this defect is not addressed during the revision surgery. We present a case of failed fixation of a subtrochanteric fracture in an 86-year-old female where revision surgery paid special attention to restoring the medial wall continuity via bone grafting resulting in satisfactory union of the fracture. We advocate the necessity of reconstructing the medial column in similar cases in order to enhance healing and restore the biomechanical support of the subtrochanteric region.

Does Needle Design Affect the Regenerative Potential of Bone Marrow Aspirate? An In Vitro Study

While autologous bone is still the gold standard for treatment of bone defects, its availability is limited. Sufficient numbers of mesenchymal stroma cells (MSC) may be an alternative. Small volumes of bone marrow aspirate (BMA) were harvested with two different needle systems comparing the yield and regenerative potency of the MSCs. BMA (10 mL) was aspirated from the posterior iliac crest of 12 patients with degenerative spinal disc disease using both needle systems in each patient: the Jamshidi needle (JAM) and on the contralateral side the Marrow Cellution^® Needle (AMC). Number of mononuclear cells (MNCs) and regeneration capacity (colony-forming unit/CFU) were determined. MSCs were characterized for surface markers and their differentiation into trilineages. There was no significant difference between the two harvesting needles regarding the quantity of MNCs in BMA: 5.2 ± 1.8 × 10⁹ MNC/mL for AMC vs. 4.8 ± 2.5 × 10⁹ MNC/mL for JAM, p = 0.182. The quantity of CFUs per ml BMA was similar for both groups: 3717 ± 5556 for AMC and 4305 ± 5507 for JAM (p = 0.695). The potency of MSCs expressed as colony-forming potential per 10⁶ MNC resulted in 0.98 ± 1.51 for AMC and 1.00 ± 0.96 for JAM (p = 0.666). Regardless of the needle design, 10 mL bone marrow aspirate contains a sufficient number of about 40,000 MSCs that can be used to enhance bone healing.

Innovative Molecular and Cellular Therapeutics in Cleft Palate Tissue Engineering

Clefts of the lip and/or palate are the most prevalent orofacial birth defects occurring in about 1:700 live human births worldwide. Early postnatal surgical interventions are extensive and staged to bring about optimal growth and fusion of palatal shelves. Severe cleft defects pose a challenge to correct with surgery alone, resulting in complications and sequelae requiring life-long, multidisciplinary care. Advances made in materials science innovation, including scaffold-based delivery systems for precision tissue engineering, now offer new avenues for stimulating bone formation at the site of surgical correction for palatal clefts. In this study, we review the present scientific literature on key developmental events that can go awry in palate development and the common surgical practices and challenges faced in correcting cleft defects. How key osteoinductive pathways implicated in palatogenesis inform the design and optimization of constructs for cleft palate correction is discussed within the context of translation to humans. Finally, we highlight new osteogenic agents and innovative delivery systems with the potential to be adopted in engineering-based therapeutic approaches for the correction of palatal defects. Impact statement Tissue-engineered scaffolds supplemented with osteogenic growth factors have attractive, largely unexplored possibilities to modulate molecular signaling networks relevant to driving palatogenesis in the context of congenital anomalies (e.g., cleft palate). Constructs that address this need may obviate current use of autologous bone grafts, thereby avoiding donor-site morbidity and other regenerative challenges in patients afflicted with palatal clefts. Combinations of biomaterials and drug delivery of diverse regenerative cues and biologics are currently transforming strategies exploited by engineers, scientists, and clinicians for palatal cleft repair.

Heparinized chitosan stabilizes the bioactivity of BMP-2 and potentiates the osteogenic efficacy of demineralized bone matrix

Background

Demineralized bone matrix (DBM), an allograft bone processed to better expose osteoinductive factors such as bone morphogenetic proteins (BMPs), is increasingly used for clinical bone repair. However, more extensive use of DBM is limited by its unpredictable osteoinductivity and low bone formation capacity. Commercial DBM products often employ polymeric carriers to enhance handling properties but such carriers generally do not possess bioactive functions. Heparin is a highly sulfated polysaccharide and is shown to form a stable complex with growth factors to enhance their bioactivities. In this study, a new heparinized synthetic carrier for DBM is developed based on photocrosslinking of methacrylated glycol chitosan and heparin conjugation.

Results

Heparinized chitosan exerts protective effects on BMP bioactivity against physiological stressors related to bone fracture healing. It also enhances the potency of BMPs by inhibiting the activity of BMP antagonist, noggin. Moreover, heparinized chitosan is effective to deliver bone marrow stromal cells and DBM for enhanced osteogenesis by sequestering and localizing the cell-produced or DBM-released BMPs.

Conclusions

This research suggests an essential approach of developing a new hydrogel carrier to stabilize the bioactivity of BMPs and improve the clinical efficacy of current bone graft therapeutics for accelerated bone repair.

Clinical outcome and explant histology after using a cellular bone allograft in two-stage total hip arthroplasty

Background

Although use of cellular bone allografts (CBA) in orthopedic surgery has become increasingly common, little information is available regarding their short-term clinical performance. In these two case reports of two-stage hip arthroplasties, ViviGen Formable CBA (V-CBA) was used in stage one to fill voids left by previous metal implants.

Methods

The two patients had distinctly different health profiles, but each of them had previous metal implants due to a hip fracture. In the otherwise healthy 49-year-old male patient, the total hip arthroplasty (THA) was performed 7 weeks after nail removal and V-CBA backfill. In the 64-year-old female patient with Type 1 diabetes and severe osteoporosis, stage 2 was performed after 12 weeks. At the time of THA for each patient, bone containing some V-CBA was removed to accommodate the hip implant. The explants were histologically analyzed for bone matrix, mineralization, and neovascularization.

Results

Histological staining showed substantial new bone formation and neovascularization in both explants albeit at different levels of maturity.

Conclusions

Although limited, these results suggest that V-CBA may facilitate new bone formation in healthy as well as in metabolically challenged patients.

Level of evidence

V, case report

Collagen and bone morphogenetic protein-2 functionalized hydroxyapatite scaffolds induce osteogenic differentiation in human adipose-derived stem cells

Surface modification is one important way to fabricate successful biocompatible materials in bone tissue engineering. Hydroxyapatite (HAp) materials have received considerable attention as suitable bioceramics for manufacturing osseous implants because of their similarity to bone mineral in terms of chemical composition. In this study, the surface of porous HAp scaffold was modified by collagen treatment and bone morphogenetic protein-2 (BMP-2) conjugation. The surface modification did not affect the HAp scaffold's bulk properties. No significant difference in compressive strength was found among different scaffolds, with HAp, collagen modified HAp, and collagen-BMP-2-functionalized HAp having compressive strengths of 45.8 ± 3.12, 51.2 ± 4.09, and 50.7 ± 3.98 MPa, respectively. In vitro studies were performed to compare adhesion and osteogenic differentiation between human adipose-derived stem cells (hADSCs) with modified surfaces and those unmodified HAp surfaces. Collagen or BMP-2 alone was insufficient and that both collagen and BMP-2 are necessary to get the desired results. The findings suggest the possibility of using three-dimensional HAp scaffold treated with gold-standard collagen coating and highly researched BMP-2 growth factor as a platform to deliver hADSCs. Results of this study could be used to develop treatment strategy for regenerating completely transected models using more synergistic approaches.

Allograft Tissue Safety and Technology

Allograft tissues are commonly used by orthopedic surgeons and are processed using a variety of technologies to increase safety and clinical use. For safety, although disease transmission is a tangible risk, this possibility has been dramatically minimized through modern tissue-processing methods. These include steps to prevent processing tissues with unacceptable bioburden through rigorous screening using donor medical and social histories along with microbial testing of recovered tissue and viral testing of donor serum. Potential bioburden is also controlled through aseptic recovery and processing methods and then reduced through disinfection steps that can include antibiotics, detergents, mechanical process, chemical solutions, and terminal sterilization. Processing steps may also include decellularization methods to lower immunogenic potential of some tissues. To enhance fusion potential of bone void fillers, demineralization steps may be used, and the resultant demineralized bone matrices may be combined with a carrier to improve handling. Bone void fillers and osteochondral allografts may also be specially processed to retain a living cellular component. To preserve relevant biological, biochemical, and physical properties of allografts for clinical use and ease of handling, a number of methods may be used which include: (1) refrigeration in media, (2) freeze-drying, (3) cryopreservation, (4) freezing, and (5) media storage at room temperature. As academic and industry research continue to drive advances, the future direction of allograft tissue likely includes injectables, coatings, cellular therapies, and combinations with other materials. The technology approaches outlined here will be further described along with future directions.

Principles of Nonunion Management: State of the Art

A substantial proportion of fractures can present with nonunion, and the management of nonunion continues to present a challenge for orthopaedic surgeons. A variety of biological, mechanical, patient, and injury factors can contribute to the occurrence of nonunion, and often the cause of nonunion may be multifactorial. Successful management often requires assessment and treatment of more than one of these factors. This article reviews common factors that may contribute to nonunion including infection, impaired biology, and metabolic disorders. In addition, new and evolving strategies for diagnosing the cause and effectively treating nonunion including the diagnosis of infection, metabolic workup, bone grafting, cell-based therapies, and biological adjuvants are reviewed and discussed.

Scaffolds for the repair of bone defects in clinical studies: a systematic review

Background

This systematic review aims to summarize the clinical studies on the use of scaffolds in the repair of bony defects.

Methods

The relevant articles were searched through PubMed database. The following keywords and search terms were used: “scaffolds,” “patient,” “clinic,” “bone repair,” “bone regeneration,” “repairing bone defect,” “repair of bone,” “osteanagenesis,” “osteanaphysis,” and “osteoanagenesis.” The articles were screened according to inclusion and exclusion criteria, performed by two reviewers.

Results

A total of 373 articles were obtained using PubMed database. After screening, 20 articles were identified as relevant for the purpose of this systematic review. We collected the data of biological scaffolds and synthetic scaffolds. There are eight clinical studies of biological scaffolds included collagen, gelatin, and cellular scaffolds for bone healing. In addition, 12 clinical studies of synthetic scaffolds on HAp, TCP, bonelike, and their complex scaffolds for repairing bone defects were involved in this systematic review.

Conclusions

There are a lot of clinical evidences showed that application of scaffolds had a good ability to facilitate bone repair and osteogenesis. However, the ideal and reliable guidelines are insufficiently applied and the number and quality of studies in this field remain to be improved.

Osteoconduction of Unrestricted Somatic Stem Cells on an Electrospun Polylactic-Co-Glycolic Acid Scaffold Coated with Nanohydroxyapatite

The limitation of traditional bone grafts could be overcome by applying engineered bone constructs, which are mainly produced by seeding suitable stem cells on appropriate scaffolds. So far, bone marrow-derived stromal cells have been the most applied cells in bone tissue engineering, but current data show that unrestricted somatic stem cells (USSCs) from human cord blood might actually be a better stem cell source due to the accessibility and noninvasive procedure of collection. In this study, we cultured USSCs on a plasma-treated electrospun polylactic-co-glycolic acid (PLGA) scaffold coated with nanohydroxyapatite (nHA). Adhesion and proliferation of USSCs on PLGA/nHA were assessed by scanning electron microscopy and MTT assay. Osteogenic differentiation of USSCs into osteoblast lineage cells was evaluated via alkaline phosphatase (ALP) activity and real-time polymerase chain reaction. Our observation showed that USSCs attached and proliferated on PLGA/nHA. Osteogenic differentiation was confirmed by increased ALP activity and OSTEONECTIN expression in USSCs on PLGA/nHA after the 1st week of the osteogenic period. Therefore, using USSCs on electrospun PLGA/nHA is a promising approach in bone tissue engineering.

The Poor Osteoinductive Capability of Human Acellular Bone Matrix

Demineralized bone matrix (DBM) has extensive clinical use for bone regeneration because of its osteoinductive and osteoconductive aptitude. It is suggested that the demineralization process in bone matrix preparation is influential in maintaining osteoinductivity; however, relevant investigations, especially into the osteoinductivity of acellular bone matrix, are not often performed. This study addressed the osteoinductive capability of human acellular cancellous bone matrix (ACBM) after subcutaneous implantation in a rat model. The growth and osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBM-MSCs) seeded in this material were also studied. Without the demineralization process, the ACBM we obtained had an interconnected porous network and the micropores in the surface were clearly exposed. After the ACBM was subcutaneously implanted for 4 months, new osteoid formation was noted but not typical mature bone formation. rBM-MSCs grew well in the ACBM and kept a steady morphology after continuous culture for 28 days. However, no mineralized nodule formation was detected and the expression levels of genes encoding osteogenic markers were significantly decreased. These results demonstrated that human ACBM possess the structural features of native bone and poor osteoinductivity; nonetheless this material helped to preserve the undifferentiated phenotype of rBM-MSCs. Such insights may further broaden our understanding of the application of ACBM for bone regeneration and the creation of stem cell niches.

Bone substitutes: a review of their characteristics, clinical use, and perspectives for large bone defects management

Bone replacement might have been practiced for centuries with various materials of natural origin, but had rarely met success until the late 19th century. Nowadays, many different bone substitutes can be used. They can be either derived from biological products such as demineralized bone matrix, platelet-rich plasma, hydroxyapatite, adjunction of growth factors (like bone morphogenetic protein) or synthetic such as calcium sulfate, tri-calcium phosphate ceramics, bioactive glasses, or polymer-based substitutes. All these substitutes are not suitable for every clinical use, and they have to be chosen selectively depending on their purpose. Thus, this review aims to highlight the principal characteristics of the most commonly used bone substitutes and to give some directions concerning their clinical use, as spine fusion, open-wedge tibial osteotomy, long bone fracture, oral and maxillofacial surgery, or periodontal treatments. However, the main limitations to bone substitutes use remain the management of large defects and the lack of vascularization in their central part, which is likely to appear following their utilization. In the field of bone tissue engineering, developing porous synthetic substitutes able to support a faster and a wider vascularization within their structure seems to be a promising way of research.

Strategies to develop endogenous stem cell-recruiting bioactive materials for tissue repair and regeneration

A leading strategy in tissue engineering is the design of biomimetic scaffolds that stimulate the body's repair mechanisms through the recruitment of endogenous stem cells to sites of injury. Approaches that employ the use of chemoattractant gradients to guide tissue regeneration without external cell sources are favored over traditional cell-based therapies that have limited potential for clinical translation. Following this concept, bioactive scaffolds can be engineered to provide a temporally and spatially controlled release of biological cues, with the possibility to mimic the complex signaling patterns of endogenous tissue regeneration. Another effective way to regulate stem cell activity is to leverage the inherent chemotactic properties of extracellular matrix (ECM)-based materials to build versatile cell-instructive platforms. This review introduces the concept of endogenous stem cell recruitment, and provides a comprehensive overview of the strategies available to achieve effective cardiovascular and bone tissue regeneration.

Incorporation of Collagen in Calcium Phosphate Cements for Controlling Osseointegration

In this study, we investigated the effect of supplementing a non-dispersive dicalcium phosphate-rich calcium phosphate bone cement (DCP-rich CPC) with type I collagen on in vitro cellular activities and its performance as a bone graft material. Varying amounts of type I collagen were added during the preparation of the DCP-rich CPC. In vitro cell adhesion, morphology, viability, and alkaline phosphatase (ALP) activity were evaluated using progenitor bone cells. Bone graft performance was evaluated via a rat posterolateral lumbar fusion model and osteointegration of the implant. New bone formations in the restorative sites were assessed by micro-computed tomography (micro-CT) and histological analysis. We found that the incorporation of collagen into the DCP-rich CPC was associated with increased cell adhesion, cell viability, and ALP activity in vitro. The spinal fusion model revealed a significant increase in bone regeneration. Additionally, better osseointegration was observed between the host bone and graft with the DCP-rich CPC supplemented with collagen than with the collagen-free DCP-rich CPC control graft. Furthermore, compared to the control graft, the results of micro-CT showed that a smaller amount of residual material was observed with the collagen-containing DCP-rich CPC graft compared with the control graft, which suggests the collagen supplement enhanced new bone formation. Of the different mixtures evaluated in this study (0.8 g DCP-rich CPC supplemented with 0.1, 0.2, and 0.4 mL type I collagen, respectively), DCP-rich CPC supplemented with 0.4 mL collagen led to the highest level of osteogenesis. Our results suggest that the DCP-rich CPC supplemented with collagen has potential to be used as an effective bone graft material in spinal surgery.

Demineralized Bone Matrix Add-On for Acceleration of Bone Healing in Atypical Subtrochanteric Femoral Fracture: A Consecutive Case-Control Study

Background. Delayed union and nonunion are common complications in atypical femoral fractures (AFFs) despite having good fracture fixation. Demineralized bone matrix (DBM) is a successfully proven method for enhancing fracture healing of the long bone fracture and nonunion and should be used in AFFs. This study aimed to compare the outcome after subtrochanteric AFFs (ST-AFFs) fixation with and without DBM. Materials and Methods. A prospective study was conducted on 9 ST-AFFs patients using DBM (DBM group) during 2013-2014 and compared with a retrospective consecutive case series of ST-AFFs patients treated without DBM (2010–2012) (NDBM group, 9 patients). All patients were treated with the same standard guideline and followed up until fractures completely united. Postoperative outcomes were then compared. Results. DBM group showed a significant shorter healing time than NDBM group (28.1 ± 14.4 versus 57.9 ± 36.8 weeks, p = 0.04). Delayed union was found in 4 patients (44%) in DBM group compared with 7 patients (78%) in NDBM group (p > 0.05). No statistical difference of nonunion was demonstrated between both groups (DBM = 1 and NDBM = 2, p > 0.05). Neither postoperative infection nor severe local tissue reaction was found. Conclusions. DBM is safe and effective for accelerating the fracture healing in ST-AFFx and possibly reduces nonunion after fracture fixation. Trial registration number is TCTR20151021001.

Cationized gelatin hydrogels mixed with plasmid DNA induce stronger and more sustained gene expression than atelocollagen at calvarial bone defects in vivo

Gene transduction of exogenous factors at local sites in vivo is a promising approach to promote regeneration of tissue defects owing to its simplicity and capacity for expression of a variety of genes. Gene transduction by viral vectors is highly efficient; however, there are safety concerns associated with viruses. As a method for nonviral gene transduction, plasmid DNA delivery is safer and simpler, but requires an efficient carrier substance. Here, we aimed to develop a simple, efficient method for bone regeneration by gene transduction and to identify optimal conditions for plasmid DNA delivery at bone defect sites. We focused on carrier substances and compared the efficiencies of two collagen derivatives, atelocollagen, and gelatin hydrogel, as substrates for plasmid DNA delivery in vivo. To assess the efficiencies of these substrates, we examined exogenous expression of green fluorescence protein (GFP) by fluorescence microscopy, polymerase chain reaction, and immunohistochemistry. GFP expression at the bone defect site was higher when gelatin hydrogel was used as a substrate to deliver plasmids than when atelocollagen was used. Moreover, the gelatin hydrogel was almost completely absorbed at the defect site, whereas some atelocollagen remained. When a plasmid harboring bone morphogenic protein 2 was delivered with the substrate to bony defect sites, more new bone formation was observed in the gelatin group than in the atelocollagen group. These results suggested that the gelatin hydrogel was more efficient than atelocollagen as a substrate for local gene delivery and may be a superior material for induction of bone regeneration.

Failed treatment of long bone nonunions with low intensity pulsed ultrasound

INTRODUCTION

The use of low intensity pulsed ultrasound (LIPUS) in the treatment of nonunions is still controversial. The present study is concerned with whether this procedure has a clinical use and which cofactors influence its therapeutic results.

METHODS

In this prospective, single institution, observational study, data from October 2010 to October 2013 from 61 nonunions in 60 patients treated with EXOGEN(®) LIPUS therapy were analysed. The average age was 45.4 ± 9.81 (18-63) years. Treatment was primarily done on long bones of the lower extremity (75.4 %). All 61 nonunions were examined after treatment, and the rate of healing as well as functional and subjective results were evaluated. Based on clinical and radiological findings, patients were divided into two groups: G1-successful treatment; and G2-unsuccessful treatment. Groups were compared to one another to identify possible factors influencing treatment.

RESULTS

Twenty (32.8 %) patients showed bone consolidation with an average time of healing of 5.3 (2-7) months. In patients without successful treatment, who underwent revision surgery instead, full weight bearing took on average 3.7 months longer, and they were able to return to work 6.8 months later. Most of the treated patients (70.5 %) reported no improvement in pain. In G2, 12 (29.3 %) patients suffered in their previous history from osteitis; in G1 there were only two patients (10 %) (p = 0.012). There were further significant differences in the age of the fracture, the type of osteosynthesis, the gap size, as well as the NUSS score.

CONCLUSION

Despite patients being chosen strictly according to EXOGEN(®) indications, only a small number of patients with nonunions who underwent LIPUS therapy experienced successful treatment (32.8 %). Overall, its use resulted in a clear delay in the time of treatment, so that according to our results, the use of LIPUS should be seen critically in long bone nonunions and use should be made on a case-by-case basis.

Combined use of the Ilizarov method, concentrated bone marrow aspirate (cBMA), and platelet-rich plasma (PRP) to expedite healing of bimalleolar fractures

Distal tibial and fibular fractures, particularly in patients with comorbidities, heal slowly and have a high incidence of postoperative nonunion and infection. Autologous concentrated bone marrow aspirate (cBMA) and platelet-rich plasma (PRP) increase osteogenic potential of demineralized bone matrix (DBM). The purpose of this case series was to evaluate the efficacy of cBMA, PRP, DBM in conjunction with the Ilizarov fixator as compared to DBM and the Ilizarov fixator alone in expediting fracture healing. Ten patients (mean age 52.9 years) were in the cBMA Group, and 10 patients (mean age 54 years) were in the Control Group. Comorbidities included diabetes, obesity, smoking, and renal disease. Radiographs showed a significant difference in the rate of complete healing in the cBMA Group at 16 ± 1.6 weeks post-surgery as compared to 24 ± 1.3 weeks in the Control Group (P < 0.001). No differences were observed between groups in infection rate or nonunions. We conclude that the Ilizarov fixator combined with DBM, cBMA, and PRP expedites fracture healing of the distal tibia and fibula in patients with significant comorbidities.

Histologic Evaluation of Critical Size Defect Healing With Natural and Synthetic Bone Grafts in the Pigeon ( Columba livia ) Ulna

Fracture and bone segment loss are major clinical problems in birds. Achieving bone formation and clinical union in a fracture case is important for the survival of the bird. To evaluate the efficacy of bone grafts for defect healing in birds, 2 different bone grafts were investigated in the healing of a bone defect in 24 healthy pigeons ( Columba livia ). In each bird, a 1-cm critical size defect (CSD) was created in the left ulna, and the fracture was stabilized with external skeletal fixation (ESF). A graft of hydroxyapatite (HA) alone (n = 12 birds) or demineralized bone matrix (DBM) combined with HA (n = 12 birds) was implanted in the CSD. The CSD healing was evaluated at 3 endpoints: 3, 6, and 12 weeks after surgery. Four birds were euthanatized at each endpoint from each treatment group, and bone graft healing in the ulna CSD was evaluated by histologic examination. The CSD and graft implants were evaluated for quality of union, cortex development, and bone graft incorporation. Results showed no graft rejection in any bird, and all birds had connective tissue formation in the defect because of the bone graft application. These results suggest that bone defect healing can be achieved by a combination of osteoinductive and osteoconductive bone graft materials for clinical union and new bone regeneration in birds. The combination of DBM and HA resulted in a better quality bone graft (P < .05) than did HA alone, but there was no significant differences in cortex development or bone graft incorporation at 3, 6, or 12 weeks. From the results of this study, we conclude that HA bone grafts, alone or in combination with DBM, with external skeletal fixation is suitable and safe for bone defect and fracture treatment in pigeons.

Comparing immunocompetent and immunodeficient mice as animal models for bone tissue engineering

OBJECTIVES

To understand the differences and similarities between immunocompetent and immunodeficient mice as ectopic transplantation animal models for bone tissue engineering.

MATERIALS AND METHODS

Osteogenic cells from mouse leg bones were cultured, seeded on β-TCP granules, and transplanted onto the backs of either immunocompetent or immunodeficient nude mice. At 1, 2, 4, and 8 weeks postoperatively, samples were harvested and evaluated by hematoxylin-eosin staining, tartrate-resistant acid phosphatase (TRAP) staining, and immunohistochemical staining and quantitative PCR.

RESULTS

In immunocompetent mice, inflammatory cell infiltration was evident at 1 week postoperatively and relatively higher expression of TNF-α and IL-4 was observed. In immunodeficient mice, new bone area and the number of TRAP-positive cells were larger at 4 weeks than in immunocompetent mice. The volume of new bone area in immunodeficient mice was reduced by 8 weeks.

CONCLUSIONS

Bone regeneration was feasible in immunocompetent mice. However, some differences were observed between immunocompetent and immunodeficient mice in the bone regeneration process possibly due to different cytokine expression, which should be considered when utilizing in vivo animal models.

Comparative Evalution of G bone (Hydroxyapatite) and G-Graft (Hydroxyapatite with Collagen) as Bone Graft Material in Mandibular III Molar Extraction Socket

BACKGROUND

Bone grafting is a dynamic phenomenon. It is a surgical procedure that replaces missing bone with material either from patient's own body, or, an artificial, synthetic or natural substitute. A successful bone graft when applied, heals, becomes incorporated, re-vascularises and eventually assumes the form desired.

AIMS AND OBJECTIVE

The main purpose of this present study was to radiologically assess and compare the regenerative potential of hydroxyapatite with Collagen (G-Graft) and hydroxyapatite (G-Bone) and to evaluate the clinical usefulness of these materials to enhance bone healing in third molar extraction sites through bone formation.

MATERIALS AND METHODS

The study was carried out in the Department of Oral & Maxillofacilal Surgery, patients were divided into three groups. The rationale for assigning the patients to the groups was strictly random: Group I - G-Graft (Hydroxyapatite with Collagen) was used as Bone graft material, Group II - Bone graft material used was G-Bone (Hydroxyapatite), Group III-control group (no grafts was used). Orthopentomogram(OPG) images were taken intra-operatively, just after extraction in the Group III (control), after extraction but before graft placement in Group I & II (study groups) and post-operatively at the end of first month and third month. Bone density of the post-extraction sockets was measured at four random areas through 'densitometric analysis' software in the OPG program (Kodak 8000C Digital Panoramic System, Eastman Kodak Company) and an average value was recorded at each review.

RESULTS

The percentage increase in bone density between 1(st) month & 3(rd) month was 7.55± 12.43 in Group I (G Graft), 4.41± 5.4859 in Group II (G Bone), while that Group III (control) was found to be -0.82 ± 3.96. The bone density increase was found to be statistically highly significant (p<0.01)) between all groups.

CONCLUSION

The present study concluded that G-Graft has a definite regenerative potential and is better than G-bone and can be used in bony defects to enhance the bone healing without provoking any significant inflammatory process. The study also indicates that defects treated with G-Graft attain more density initially and that G-Graft enhances bone healing in early stage.

Is DBM beneficial for the enhancement of bony consolidation in distraction osteogenesis? A randomized controlled trial

The aim of the present study was to compare the radiographic and clinical outcomes of DBM injection and conventional treatment during tibial lengthening over an intramedullary nail in adult patients with short stature. Twenty-nine patients were randomized to receive DBM injection (n = 14) or conventional treatment without any injection (n = 15) and evaluated. The outcome was measured on the basis of the pixel value ratio (PVR) in the digital radiographs during the consolidation period; healing index; clinical assessment; and the rate of complications. In the DBM group, the mean PVR of 1 (mineral density of the callus is comparable to the adjacent bone) was reached by 40 weeks in anterior and medial cortices which was significantly different than that in the control group (P = 0.03 for anterior cortex; P = 0.04 for medial cortex). The average healing index in the DBM group was 39.8 ± 5.3 days/cm compared to 44.3 ± 5.8 days/cm in the control group (P = 0.05). There were no significant differences in clinical outcomes (P = 0.23) and functional status (P = 0.47) including complications (P = 0.72) between two groups. In this randomized clinical trial, injection of DBM at the time of initial operation enhanced consolidation of regenerate callus without interfering with clinical outcomes compared to that with conventional treatment.

Mesenchymal stem cells with increased stromal cell-derived factor 1 expression enhanced fracture healing

Treatment of critical size bone defects pose a challenge in orthopedics. Stem cell therapy together with cytokines has the potential to improve bone repair as they cause the migration and homing of stem cells to the defect site. However, the engraftment, participation, and recruitment of other cells within the regenerating tissue are important. To enhance stem cell involvement, this study investigated overexpression of stem cells with stromal cell-derived factor 1 (SDF-1) using an adenovirus. We hypothesized that these engineered cells would effectively increase the migration of native cells to the site of fracture, enhancing bone repair. Before implantation, we showed that SDF-1 secreted by transfected cells increased the migration of nontransfected cells. In a rat defect bone model, bone marrow mesenchymal stem cells overexpressing SDF-1 showed significantly (p=0.003) more new bone formation within the gap and less bone mineral loss at the area adjacent to the defect site during the early bone healing stage. In conclusion, SDF-1 was shown to play an important role in accelerating fracture repair and contributing to bone repair in rat models, by recruiting more host stem cells to the defect site and encouraging osteogenic differentiation and production of bone.

Growth factors in orthopaedic surgery: demineralized bone matrix versus recombinant bone morphogenetic proteins

During recent decades the utilisation of growth factors, especially BMPs, has received an increasing interest in orthopaedic surgery. For clinical implantation the two main options are demineralised bone matrix (DBM) and recombinant bone morphogenetic proteins (rhBMP). Many clinical studies agree on an equivalent osteoinductive effect between DBM, BMPs and autologous bone graft; however, the different origins and processing of DBM and rhBMP may introduce some fluctuations. Their respective characteristics are reviewed and possible interactions with their effectiveness are analysed. The main difference concerns the concentration of BMPs, which varies to an order of magnitude of 10(6) between DBM and rhBMPs. This may explain the variability in efficiency of some products and the adverse effects. Currently, considering osteoinductive properties, safety and availability, the DBM seems to offer several advantages. However, if DBM and rhBMPs are useful in some indications, their effectiveness and safety can be improved and more evidence-based studies are needed to better define the indications.

Demineralized bone matrix for alveolar cleft management

The aim of this article is to describe the results of the use of demineralized bone matrix putty in alveolar cleft of patients with cleft lip and palate. We performed a prospective, descriptive case series study, in which we evaluated the results of the management of alveolar clefts with demineralized bone matrix. Surgery was performed in 10 patients aged between 7 and 26 years (mean 13 years), involving a total of 13 clefts in the 10 patients. A preoperative cone beam computed tomography (CBCT) was taken to the patients in whom the width of the cleft was measured from each edge of the cleft reporting values between 5.76 and 16.93 mm (average, 11.18 mm). The densities of the clefts were measured with a CBCT, 6 months postoperative to assess bone formation. The results showed a register of gray values of 1,148 to 1,396 (mean, 1,270). The follow-up was conducted for 15 to 33 months (mean, 28.2 months). The results did not show satisfactory bone formation in the cleft of patients with the use of demineralized bone matrix.

Analysis of parameters influencing the release of antibiotics mixed with bone grafting material using a reliable mixing procedure

Local infections arising from fracture fixation, defect reconstruction or joint replacement can cause extreme pain and impaired healing, lead to revision operations, prolong hospital stay and increase costs. Treatment options including prophylaxis are afforded by the use of grafts and biomaterials loaded with antibiotics. These can produce local therapeutic concentrations with a reduced systemic concentration and reduced systemic side-effects. Patient-specific loading of osteogenic graft materials with antibiotic could be an important option for orthopaedic surgeons. A local therapeutic concentration must be available for the desired duration and cytotoxic effects must be kept within an acceptable range. The present study investigates a simple and reliable mixing procedure that could be used for the perioperative combination of antibiotic powders and solutions with bone grafting materials. The potential influence of concentration and sampling regime on the release kinetics of gentamicin, tobramycin and vancomycin was studied over a period of 56days and potency and cytotoxicity were evaluated. In all treatment groups, gentamicin and tobramycin were completely released within 3days whilst vancomycin was released over a period of 14days. The results clearly show that the main parameter influencing release is the molecular weight of the drug. Growth of Staphylococcus aureus was inhibited in all 3 treatment groups for at least 3days. Cell viability and alkaline phosphatase activity of primary osteoblast-like cells were not significantly affected by the antibiotic concentrations obtained from the elution experiments. Bone grafting is an established component of surgery for bone defect filling and for biological stimulation of healing. Patient-specific enhancement of such procedures by incorporation of antibiotics for infection prevention or by addition of cytokines for promotion of impaired healing or for treatment of critical size defects will be a relevant issue in the future.

Hybrid grafting of post-traumatic bone defects using β-tricalcium phosphate and demineralized bone matrix

OBJECTIVES

Management of post-traumatic bone defects continues to be a substantial clinical challenge in orthopaedic trauma. This retrospective study evaluates the results of primary hybrid grafting of residual bone defects or voids, in displaced and comminuted long-bone fractures treated by plate fixation, using β-tricalcium phosphate and demineralized bone matrix.

MATERIALS AND METHODS

Fifty-four patients having 62 fractures were included. Their mean age was 40.7±10.7 years; femoral and tibial fractures were the commonest (70.9%) in this study. Eight fractures (12.9%) were open injuries; 13 fractures had critical-sized defects that averaged 3.4±0.9 cm. Cortical bone defects occurred in 51 cases, and cancellous bone voids in eleven. Eleven patients (20%) were polytraumatized. Tobramycin powder was added to the graft in all open fractures. The functional outcome was evaluated according to a modified Karlström and Olerud criteria.

RESULTS

All fractures (100%) had solid union without any implant failure. There was a significant delayed union (P<0.001) in all critical-sized defects. The mean healing time showed a highly significant difference (P<0.001) between closed and open fractures. The functional outcome was excellent in 28 fractures, good in 21 fractures, fair in nine fractures and poor in four fractures.

CONCLUSIONS

We believe that the ideal bone graft substitute for all situations does not exist; however, this hybrid grafting is a very good alternative to autogenous grafts especially in polytraumatized patients and when massive bone grafting is needed to reconstruct more than one bone in absence of segmental defects.

Remineralization of demineralized bone matrix (DBM) via alternating solution immersion (ASI)

In order to achieve successful clinical outcomes, biomaterials used for bone grafts must possess a number of traits including biocompatibility and osteoconductivity. These materials must also demonstrate appropriate mechanical stability to withstand handling as well as support potentially significant stresses at the implant site. Synthetic and natural polymer scaffolds used for bone tissue engineering (BTE) often lack necessary mechanical properties. Our goal was to internally mineralize natural collagenous matrix, thereby increasing mechanical properties of the material to useful levels. Published methods for intrafibrillar collagen mineralization were applied to clinically relevant-sized constructs but did not successfully deposit mineral in the interior of the constructs. To address this limitation, we developed a new technique for the remineralization of demineralized bone matrix (DBM) based on alternating solution immersion, or ASI. Mineral was removed from equine bone specimens, leaving behind a demineralized bone matrix (DBM). This matrix provides a framework for the nucleation and growth of a replacement mineral phase. Plain film radiography and microcomputed tomography (microCT) indicated accumulation of mineral within the DBM, and mechanical testing (3 point bending and compression) revealed a significant increase in stiffness between the DBM and the remineralized bone matrix (RBM). We believe this remineralization process will be useful in the preparation of stiff and strong allografts for clinical application.

Research progress in the mechanism of effect of PRP in bone deficiency healing

Platelet-rich plasma (PRP) therapy is a recently developed technique that uses a concentrated portion of autologous blood to try to improve and accelerate the healing of various tissues. There is a considerable interest in using these PRP products for the treatment used in bone deficiency healing. Because PRP products are safe and easy to prepare and administer, there has been increased attention toward using PRP in numerous clinical settings. The benefits of PRP therapy appear to be promising, and many investigators are exploring the ways in which this therapy can be used in the clinical setting. At present, the molecular mechanisms of bone defect repair studies have focused on three aspects of the inflammatory cytokines, growth factors and angiogenic factors. The role of PRP works mainly through these three aspects of bone repair. The purpose of this paper is to review the current evidence on the mechanism of the effect of PRP in bone deficiency healing.

Three years after transplants in human mandibles, histological and in-line holotomography revealed that stem cells regenerated a compact rather than a spongy bone: biological and clinical implications

Mesenchymal stem cells deriving from dental pulp differentiate into osteoblasts capable of producing bone. In previous studies, we extensively demonstrated that, when seeded on collagen I scaffolds, these cells can be conveniently used for the repair of human mandible defects. Here, we assess the stability and quality of the regenerated bone and vessel network 3 years after the grafting intervention, with conventional procedures and in-line holotomography, an advanced phase-imaging method using synchrotron radiation that offers improved sensitivity toward low-absorbing structures. We found that the regenerated tissue from the graft sites was composed of a fully compact bone with a higher matrix density than control human alveolar spongy bone from the same patient. Thus, the regenerated bone, being entirely compact, is completely different from normal alveolar bone. Although the bone regenerated at the graft sites is not of the proper type found in the mandible, it does seem to have a positive clinical impact. In fact, it creates steadier mandibles, may well increase implant stability, and, additionally, may improve resistance to mechanical, physical, chemical, and pharmacological agents.

Treatment of delayed and nonunited fractures and osteotomies with pulsed electromagnetic field in children and adolescents

Nonunion of fractures or osteotomies in the pediatric population is rare. The gold standard for the treatment of nonunions involves harvesting autologous iliac crest bone graft and sometimes internal fixation, which are invasive procedures. The purpose of this study was to evaluate the effectiveness of pulsed electromagnetic field on a non-united fracture or osteotomy in the pediatric population. A retrospective study was performed on all patients at the authors' institution who used pulsed electromagnetic field as part of their treatment for nonunion or delayed union. Success of the initial nonunion treatment was defined as complete union of the fracture or osteotomy site. Two types of treatment were administered once delayed bone healing was identified: pulsed electromagnetic field alone or pulsed electromagnetic field plus an adjunct treatment. Twenty-one patients were included; 8 osteotomies and 14 fractures developed a nonunion. Average patient age was 11.7 years. Average age for patients who healed with the initial treatment was 10.7 years, whereas nonhealers had an average age of 14 years. Eighty-nine percent of osteotomy nonunions healed with their first management. Fifty-seven percent of fracture nonunions healed at the first attempt. The use of pulsed electromagnetic field is a good option for the initial treatment of pediatric nonunions, especially for patients who develop nonunions secondary to osteotomies. Adding bone marrow aspiration improves the outcomes and is minimally invasive compared with autologous iliac crest bone graft, with no complications.

The comparative effectiveness of demineralized bone matrix, beta-tricalcium phosphate, and bovine-derived anorganic bone matrix on inflammation and bone formation using a paired calvarial defect model in rats

BACKGROUND

In this study, the effectiveness of Iranian Tissue Bank-produced demineralized bone matrix (ITB-DBM), beta-tricalcium phosphate (βTCP), and Bio-Oss(®) (Geistlich Pharma AG, Wolhusen, Switzerland) were evaluated and compared with double controls. The main goal was to measure the amount of new bone formation in the center of defects created in rat calvaria. Another goal was to compare the controls and evaluate the effects of each treatment material on their adjacent untreated (control) defects.

METHODS

In this study, 40 male Wistar rats were selected and divided into four groups, In each group, there were ten rats with two defects in their calvarias; one of them is considered as control and the other one was treated with ITB-DBM (group 1), BIO-OSS (group2), and βTCP (group 3), respectively. But in group 4, both defects were considered as control. The amount of inflammation and new bone formation were evaluated at 4 and 10 weeks. In the first group, one defect was filled with ITB-DBM; in the second group, one defect was filled with Bio-Oss; in the third group, one defect was filled with βTCP; and in the fourth group, both defects were left unfilled. Zeiss microscope (Carl Zeiss AG, Oberkochen, Germany) and Image Tool(®) (version 3.0; University of Texas Health Science Center at San Antonio, San Antonio, TX) software were used for evaluation. SPSS Statistics (IBM Corp, Somers, NY) was used for statistical analysis.

RESULTS

Maximum bone formation at 4 and 10 weeks were observed in the ITB-DBM group (46.960% ± 4.366%, 94.970% ± 0.323%), which had significant difference compared with the other groups (P < 0.001). Ranking second was the Bio-Oss group and third, the βTCP group. Bone formation in the group with two unfilled defects was much more significant than in the other controls beside the Bio-Oss and βTCP after 10 weeks (29.1 ± 2.065, 29.05 ± 1.649), while this group had the least bone formation compared with the other controls at week 4 (2.100% ± 0.758%, 1.630% ± 0.668%, P < 0.001).

CONCLUSION

Overall, the ITB-DBM group showed the best results, although the results for other experimental groups were unfavorable. The authors conclude that human DBM (ITB-DBM) should be offered as an alternative for bone regeneration in animals, such as horses, as well as in humans, especially for jaw reconstruction. In relation to bone regeneration in control defects, the effect of experimental material on controls was apparent during the initial weeks.

Complications following autologous bone graft harvesting from the iliac crest and using the RIA: a systematic review

Bone grafting is a commonly performed surgical procedure to augment bone regeneration in a variety of cases in orthopaedic and maxillofacial surgery. Autologous bone graft remains to be the 'gold standard' and the iliac crest to be the most common harvesting site. The intramedullary canal of long bones represents another potential site for large volume of autologous bone graft harvesting and is recently being used as an alternative donor site. However, harvesting of autologous bone graft is associated with morbidity and a number of complications. The aim of this systematic review was to collect and summarise the existing data on reported complications after harvesting autologous bone from the iliac crest (anterior and posterior) and the long bone intramedullary canal using the RIA device. We searched the PubMed Medline and Ovid Medline databases, from January 1990 to October 2010, to retrieve all relevant articles. A total of 92 articles (6682 patients) were included in the analysis. Overall, the complication rate following RIA was 6% (14 complications in 233 patients) and 19.37% after iliac crest bone graft harvesting (1249 complications in 6449 patients). The rate of each of the reported complications was assessed and, when the donor site was properly documented, comparison within the anterior and posterior iliac crest donor sites was performed. Although the difference of the overall morbidity rates between the two harvesting sites was not statistically significant (p=0.71); the rates of certain complications were found to significantly differ when anterior or posterior iliac crest was used. The rates of infection (p=0.016), haematoma formation (p=0.002), fracture (p=0.017), and hyperthrophic scar (p=0.017) were significantly higher when the donor site was the anterior iliac crest compared to the posterior iliac crest; whereas the rates of chronic donor site pain (p=0.004) and sensory disturbances (p=0.003) were significantly lower. The incidence of bone graft harvesting related complications can be reduced further if certain principles are followed depending on the performed harvesting methods; but overall the use of RIA device as harvesting method seems a promising alternative with a low complication rate.

The use of platelet rich plasma, bone morphogenetic protein-2 and different scaffolds in oral and maxillofacial surgery - literature review in comparison with own clinical experience

Objectives

The purpose of this article was to review and critically assess the use of platelet rich plasma, recombinant human bone morphogenetic protein-2 and different scaffolds (i.e. tricalciumphosphate, polycaprolactone, demineralized bone matrix and anorganic bovine bone mineral) in oral and maxillofacial surgery comparing the relevant literature and own clinical experience.

Material and Methods

A literature review was conducted using MEDLINE, MEDPILOT and COCHRANE DATABASE OF SYSTEMATIC REVIEWS. It concentrated on manuscripts and overviews published in the last five years (2006-2010). The key terms employed were platelet rich plasma, bone morphogenetic proteins and their combinations with the above mentioned scaffolds. The results of clinical studies and animal trials were especially emphasized. The statements from the literature were compared with authors’ own clinical data.

Results

New publications and overviews demonstrate the advantages of platelet rich plasma in bone regeneration. The results from the literature review were discussed and compared with the publications detailing authors' own experiences.

Conclusions

A favourable outcome concerning newly grown bone was achieved combining platelet rich plasma in addition to optimal matrices with or without recombinant human bone morphogenetic protein-2, depending on the clinical case. As a consequence, the paradigm shift from transplantation of autogenous bone to bone tissue engineering appears promising.