Reconstruction of Segmental Bone Defect in Canine Tibia Model Utilizing Bi-Phasic Scaffold: Pilot Study

The reunion and restoration of large segmental bone defects pose significant clinical challenges. Conventional strategies primarily involve the combination of bone scaffolds with seeded cells and/or growth factors to regulate osteogenesis and angiogenesis. However, these therapies face inherent issues related to immunogenicity, tumorigenesis, bioactivity, and off-the-shelf transplantation. The biogenic micro-environment created by implanted bone grafts plays a crucial role in initiating the bone regeneration cascade. To address this, a highly porous bi-phasic ceramic synthetic bone graft, composed of hydroxyapatite (HA) and alumina (Al), was developed. This graft was employed to repair critical segmental defects, involving the creation of a 2 cm segmental defect in a canine tibia. The assessment of bone regeneration within the synthetic bone graft post-healing was conducted using scintigraphy, micro-CT, histology, and dynamic histomorphometry. The technique yielded pore sizes in the range of 230-430 μm as primary pores, 40-70 μm as secondary inner microchannels, and 200-400 nm as tertiary submicron surface holes. These three components are designed to mimic trabecular bone networks and to provide body fluid adsorption, diffusion, a nutritional supply, communication around the cells, and cell anchorage. The overall porosity was measured at 82.61 ± 1.28%. Both micro-CT imaging and histological analysis provided substantial evidence of robust bone formation and the successful reunion of the critical defect. Furthermore, an histology revealed the presence of vascularization within the newly formed bone area, clearly demonstrating trabecular and cortical bone formation at the 8-week mark post-implantation.

Strontium-loaded 3D intramedullary nail titanium implant for critical-sized femoral defect in rabbits

The treatment of critical-sized bone defects has long been a major problem for surgeons. In this study, an intramedullary nail shaped three-dimensional (3D)-printed porous titanium implant that is capable of releasing strontium ions was developed through a simple and cost-effective surface modification technique. The feasibility of this implant as a stand-alone solution was evaluated using a rabbit's segmental diaphyseal as a defect model. The strontium-loaded implant exhibited a favorable environment for cell adhesion, and mechanical properties that were commensurate with those of a rabbit's cortical bone. Radiographic, biomechanical, and histological analyses revealed a significantly higher amount of bone ingrowth and superior bone-bonding strength in the strontium-loaded implant when compared to an untreated porous titanium implant. Furthermore, one-year histological observations revealed that the strontium-loaded implant preserved the native-like diaphyseal bone structure without failure. These findings suggest that strontium-releasing 3D-printed titanium implants have the clinical potential to induce the early and efficient repair of critical-sized, load-bearing bone defects.

Use of Autologous Bone Graft with Bioactive Glass as a Bone Substitute in the Treatment of Large-Sized Bone Defects of the Femur and Tibia

BACKGROUND

Managing bone defects in non-union surgery remains challenging, especially in cases of large defects exceeding 5 cm in size. Historically, amputation and compound osteosynthesis with a remaining PMMA spacer have been viable and commonly used options. The risk of non-union after fractures varies between 2% and 30% and is dependent on various factors. Autologous bone grafts from the iliac crest are still considered the gold standard but are limited in availability, prompting consideration of artificial grafts.

OBJECTIVES

The aims and objectives of the study are as follows: 1. To evaluate the radiological outcome of e.g., the consolidation and thus the stability of the bone (three out of four consolidated cortices/Lane-Sandhu-score of at least 3) by using S53P4-type bioactive glass (BaG) as a substitute material for large-sized bone defects in combination with autologous bone using the RIA technique. 2. To determine noticeable data-points as a base for future studies.

METHODS

In our clinic, 13 patients received bioactive glass (BaG) as a substitute in non-union therapy to promote osteoconductive aspects. BaG is a synthetic material composed of sodium, silicate, calcium, and phosphate. The primary endpoint of our study was to evaluate the radiological consolidation of bone after one and two years. To assess bone stabilization, we used a modified Lane-Sandhu score, considering only radiological criteria. A bone was considered stabilized if it achieved a minimum score of 3. For full consolidation (all four cortices consolidated), a minimum score of 4 was required. Each bone defect exceeded 5 cm in length, with an average size of 6.69 ± 1.92 cm.

RESULTS

The mean follow-up period for patients without final bone consolidation was 34.25 months, with a standard deviation of 14.57 months, a median of 32.00 months and a range of 33 months. In contrast, patients with a fully consolidated non-union had an average follow-up of 20.11 ± 15.69 months and a range of 45 months. Overall, the mean time from non-union surgery to consolidation for patients who achieved final union was 14.91 ± 6.70 months. After one year, six patients (46.2%) achieved complete bone consolidation according to the Lane-Sandhu score. Three patients (23.1%) displayed evident callus formation with expected stability, while three patients (23.1%) did not develop any callus, and one patient only formed a minimal callus with no expected stability. After two years, 9 out of 13 patients (69.2%) had a score of 4. The remaining four patients (30.8%) without expected stability either did not heal within two years or required a revision during that time.

CONCLUSIONS

Bioactive glass (BaG) in combination with autologous bone (RIA) appears to be a suitable filler material for treating extensive non-unions of the femur and tibia. This approach seems to show non-inferiority to treatment with Tricalcium Phosphate (TCP). To ensure the success of this treatment, it is crucial to validate the procedure through a randomized controlled trial (RCT) with a control group using TCP, which would provide higher statistical power and more reliable results.

Matched-Pair Analysis: Large-Sized Defects in Surgery of Lower Limb Nonunions

BACKGROUND

The treatment of large-sized bone defects remains a major challenge in trauma and orthopaedic surgery. Although there are many treatment options, there is still no clear guidance on surgical management, and the influence of defect size on radiological and clinical outcome remains unclear due to the small number of affected patients. The aim of the present study was to determine the influence of defect size on the outcome of atrophic and infected nonunions of the tibia or the femur based on the diamond concept in order to provide recommendations for treatment guidance.

PATIENTS AND METHODS

All medical records, surgical reports, laboratory data and radiological images of patients treated surgically for atrophic or infected nonunions of the lower limbs (femur or tibia) between 1 January 2010 and 31 December 2020 were examined. Patients with proximal, diaphyseal or distal nonunions of the femur or tibia who were surgically treated at our institution according to the "diamond concept" and attended our standardised follow-up program were included in a database. Surgical treatment was performed as a one- or two-step procedure, depending on the type of nonunion. Patients with a segmental bone defect ≥5 cm were matched with patients suffering a bone defect <5 cm based on five established criteria. According to our inclusion and exclusion criteria, 70 patients with a bone defect ≥5 cm were suitable for analysis. Two groups were formed by matching: the study group (bone defect ≥5 cm; n = 39) and control group (bone defect <5 cm; n = 39). The study was approved by the local ethics committee (S-262/2017).

RESULTS

The mean defect size was 7.13 cm in the study and 2.09 cm in the control group. The chi-square test showed equal consolidation rates between the groups (SG: 53.8%; CG: 66.7%). However, the Kaplan-Meier curve and log-rank test showed a significant difference regarding the mean duration until consolidation was achieved, with an average of 15.95 months in the study and 9.24 months in the control group (α = 0.05, p = 0.001). Linear regression showed a significant increase in consolidation duration with increasing defect size (R² = 0.121, p = 0.021). Logistic regression modelling showed a significant negative correlation between consolidation rate and revision performance, as well as an increasing number of revisions, prior surgeries and total number of surgeries performed on the limb. Clinical outcomes showed equal full weight bearing of the lower extremity after 5.54 months in the study vs. 4.86 months in the control group (p = 0.267).

CONCLUSION

Surprisingly, defect size does not seem to have a significant effect on the consolidation rate and should not be seen as a risk factor. However, for the treatment of large-sized nonunions, the follow-up period should be prolonged up to 24 months, due to the extended time until consolidation will be achieved. This period should also pass before a premature revision with new bone augmentation is performed. In addition, it should be kept in mind that as the number of previous surgeries and revisions increases, the prospects for consolidation decrease and a change in therapeutic approach may be required.

Construction of Vascularized Tissue Engineered Bone with nHA-Coated BCP Bioceramics Loaded with Peripheral Blood-Derived MSC and EPC to Repair Large Segmental Femoral Bone Defect

The regenerative repair of segmental bone defect (SBD) is an urgent problem in the field of orthopedics. Rapid induction of angiogenesis and osteoinductivity after implantation of scaffold is critical. In this study, a unique tissue engineering strategy with mixture of peripheral blood-derived mesenchymal stem cells (PBMSC) and endothelial progenitor cells (PBEPC) was applied in a 3D-printed biphasic calcium phosphate (BCP) scaffold with highly bioactive nano hydroxyapatite (nHA) coating (nHA/BCP) to construct a novel vascularized tissue engineered bone (VTEB) for rabbit femoral SBD repair. The 2D coculture of PBMSC and PBEPC showed that they could promote the osteogenic or angiogenic differentiation of the cells from each other, especially in the group of PBEPC/PBMSC = 75:25. Besides, the 3D coculture results exhibited that the nHA coating could further promote PBEPC/PBMSC adhesion, proliferation, and osteogenic and angiogenic differentiation on the BCP scaffold. In vivo experiments showed that among the four groups (BCP, BCP-PBEPC/PBMSC, nHA/BCP, and nHA/BCP-PBEPC/PBMSC), the nHA/BCP-PBEPC/PBMSC group induced the best formation of blood vessels and new bone and, thus, the good repair of SBD. It revealed the synergistic effect of nHA and PBEPC/PBMSC on the angiogenesis and osteogenesis of the BCP scaffold. Therefore, the construction of VTEB in this study could provide a possibility for the regenerative repair of SBD.

3D-Printing for Critical Sized Bone Defects: Current Concepts and Future Directions

The management and definitive treatment of segmental bone defects in the setting of acute trauma, fracture non-union, revision joint arthroplasty, and tumor surgery are challenging clinical problems with no consistently satisfactory solution. Orthopaedic surgeons are developing novel strategies to treat these problems, including three-dimensional (3D) printing combined with growth factors and/or cells. This article reviews the current strategies for management of segmental bone loss in orthopaedic surgery, including graft selection, bone graft substitutes, and operative techniques. Furthermore, we highlight 3D printing as a technology that may serve a major role in the management of segmental defects. The optimization of a 3D-printed scaffold design through printing technique, material selection, and scaffold geometry, as well as biologic additives to enhance bone regeneration and incorporation could change the treatment paradigm for these difficult bone repair problems.

The clinical application of customized 3D-printed porous tantalum scaffolds combined with Masquelet’s induced membrane technique to reconstruct infective segmental femoral defect

Purpose

This study mainly exams a novel treatment for infective segmental femoral defect, and we combined the 3D printed porous tantalum prosthesis and Masquelet’s induce membrane technique to reconstruct bone defect and discussed the clinical effect.

Method

The clinical research included 9 observational cases series, as a permanently implantation, the customized 3D-printed scaffolds that connected with an anatomical plate was implanted into the bone defect segment after successful formation of induced membrane, the clinical effect was evaluated by radiological exams and Paley’s bone union criteria.

Result

The personalized 3D-printed porous tantalum was, respectively, manufactured and used in 9 consecutive patients to reconstruct the infective segmental bone defect of femur, the mean defect length was 16.1 ± 2.8 cm, the mean length of follow-up was 16.9 ± 4.0 months, after 2 stage operation, there was no deep infections, refractures, sensorimotor disorder, vascular injury, ankylosis and recurrence of infection occurred in all cases. postoperative radiological exams shown stable internal fixation and osseointegration, and all these results were invariable during the follow-up time in all cases. All patients significantly obtained deformity correction and length of limb.

Conclusion

The customized 3D-printed porous tantalum prosthesis was an acceptable alternative treatment to the autogenous or allograft bone graft, the combination of the two techniques could achieve satisfactory reconstruct to infective broad bone defect in femur when other biological techniques were not suitable.

Increased Arthrodesis Rates in Charcot Neuroarthropathy Utilizing Distal Tibial Distraction Osteogenesis Principles

Charcot neuroarthropathy of the hindfoot and ankle poses substantial challenges due to deformity, segmental bone loss, chronic infection, and difficulty with bracing. Hindfoot or ankle arthrodesis is often employed at high rates of complications and nonunion. This study reports 15 consecutive patients with Charcot neuroarthropathy who underwent tibiotalocalcaneal or tibiocalcaneal fusion with simultaneous distal tibial distraction osteogenesis with a mean follow-up period of 20.2 ± 5.66 months. Arthrodesis rate was 93.3% (14 patients) with mean time to fusion of 4.75 ± 3.4 months. One hypertrophic nonunion occurred at the arthrodesis site. Complete consolidation of 4 cortices was achieved at the distraction site in 93.3% of patients (14 patients) with a mean duration to consolidation of 9.8 ± 3.3 months. One patient experienced hypertrophic nonunion at the regeneration site. The authors report a technique to enhance arthrodesis rates in Charcot neuroarthropathy by combining distal tibial distraction osteogenesis with simultaneous tibiotalocalcaneal or tibiocalcaneal arthrodesis for hindfoot fusion and salvage. Distraction osteogenesis supports enhanced vascularity to the arthrodesis site.Level of Clinical Evidence: Level 4.

Honeycomb Scaffold-Guided Bone Reconstruction of Critical-Sized Defects in Rabbit Ulnar Shafts

Reconstruction of critical-sized defects (CSDs) in bone shafts remains a major challenge in orthopedics. Honeycomb (HC) scaffolds are considered promising as their uniaxial channels bridge the amputation stumps of bones and promote the ingrowth of bone and blood vessels (BV) into the scaffolds. In this study, the ability of the HC scaffolds, composed of the bone mineral or carbonate apatite (CAp), was evaluated by reconstructing 10, 15, and 20 mm segmental defects in the rabbit ulnar shaft. Radiographic and μ-computed tomography evaluations showed that bony calluses were formed around the scaffolds at 4 weeks post-surgery in all defects, whereas no callus bridged in the ulna without scaffolds. At 12 weeks post-surgery, the scaffolds were connected to the host bone in 10 and 15 mm defects, while a slight gap remained between the scaffold and host bone in the 20 mm defect. New bone formation and scaffold resorption progressed over 12 weeks. Histological evaluations showed that mature bones (MB) and BV were already formed at the edges of the scaffolds at 4 weeks post-surgery in 10, 15, and 20 mm defects. In the central region of the scaffold, in the 10 mm defect, MB and BV were formed at 4 weeks post-surgery. In the 15 mm defect, although BV were formed, a few MB were formed. It is concluded that CAp HC scaffolds have good potential value for the reconstruction of CSDs.

Temporal Changes in Reverse Torque of Locking-Head Screws Used in the Locking Plate in Segmental Tibial Defect in Goat Model

The objective of this study was to evaluate changes in peak reverse torque (PRT) of the locking head screws that occur over time. A locking plate construct, consisting of an 8-hole locking plate and 8 locking screws, was used to stabilize a tibia segmental bone defect in a goat model. PRT was measured after periods of 3, 6, 9, and 12 months of ambulation. PRT for each screw was determined during plate removal. Statistical analysis revealed that after 6 months of loading, locking screws placed in position no. 4 had significantly less PRT as compared with screws placed in position no. 5 (p < 0.05). There were no statistically significant differences in PRT between groups as a factor of time (p > 0.05). Intracortical fractures occurred during the placement of 151 out of 664 screws (22.7%) and were significantly more common in the screw positions closest to the osteotomy (positions 4 and 5, p < 0.05). Periosteal and endosteal bone reactions and locking screw backout occurred significantly more often in the proximal bone segments (p < 0.05). Screw backout significantly, negatively influenced the PRT of the screws placed in positions no. 3, 4, and 5 (p < 0.05). The locking plate-screw constructs provided stable fixation of 2.5-cm segmental tibia defects in a goat animal model for up to 12 months.

Comparison of the Translational Potential of Human Mesenchymal Progenitor Cells from Different Bone Entities for Autologous 3D Bioprinted Bone Grafts

Reconstruction of segmental bone defects by autologous bone grafting is still the standard of care but presents challenges including anatomical availability and potential donor site morbidity. The process of 3D bioprinting, the application of 3D printing for direct fabrication of living tissue, opens new possibilities for highly personalized tissue implants, making it an appealing alternative to autologous bone grafts. One of the most crucial hurdles for the clinical application of 3D bioprinting is the choice of a suitable cell source, which should be minimally invasive, with high osteogenic potential, with fast, easy expansion. In this study, mesenchymal progenitor cells were isolated from clinically relevant human bone biopsy sites (explant cultures from alveolar bone, iliac crest and fibula; bone marrow aspirates; and periosteal bone shaving from the mastoid) and 3D bioprinted using projection-based stereolithography. Printed constructs were cultivated for 28 days and analyzed regarding their osteogenic potential by assessing viability, mineralization, and gene expression. While viability levels of all cell sources were comparable over the course of the cultivation, cells obtained by periosteal bone shaving showed higher mineralization of the print matrix, with gene expression data suggesting advanced osteogenic differentiation. These results indicate that periosteum-derived cells represent a highly promising cell source for translational bioprinting of bone tissue given their superior osteogenic potential as well as their minimally invasive obtainability.

Use of a Reverse Metacarpal Bone Flap for the Treatment of Segmental Bone Defects of the Proximal Phalanges

PURPOSE

The purpose of this retrospective study was to report the results of reconstruction of segmental bone defects of the proximal phalanges using a reverse metacarpal vascularized bone flap harvested from the third metacarpal bone.

METHODS

From August 2012 to May 2017, 17 patients with segmental osteomyelitis or necrotic bone of the proximal phalanges were treated. There were 15 male and 3 female patients, with a mean age of 36 years (range, 19-65 years). The mean size of bone defects was 26 × 9 × 9 mm (range, 16 × 6 × 7 mm to 35 × 10 × 7 mm); and the mean size of bone flaps was 27 × 8 × 7 mm (range, 15 × 7 × 4 mm to 40 × 8 × 7 mm).

RESULTS

The mean follow-up period was 26 months. The mean motion arc of the metacarpophalangeal joints was 56° (range, 22°-90°). The mean pinch strength of the injured fingers was 3.1 kg (range, 2-3.6 kg), and the mean pinch strength of the normal contralateral side was 6.9 kg (range, 4.2- 8.5 kg).

CONCLUSIONS

The reverse metacarpal bone flap may promote osseous healing in reconstructing segmental defects of the proximal phalanges.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Part 3: achievement of bone union and treatment of segmental bone defects

After presentations of the principles of limb salvage and soft-tissue coverage for Gustilo III open tibia fractures, this third part is dedicated to management of tibial non-unions in low-resource settings. Inter-tibiofibular grafting and the induced membrane technique are preferred because they make it possible to deal with almost all situations. Key technical points of these methods are presented, followed by treatment guidelines based on Catagni's classification and bone defect size.

Porous Particle-Reinforced Bioactive Gelatin Scaffold for Large Segmental Bone Defect Repairing

Large segmental bone defect repairing remains a big challenge in clinics, and synthetic bone grafts suitable for this purpose are still highly demanded. In this article, hydrophilic composite scaffolds (bioactive hollow particle (BHP)-gel scaffold) composed of bioactive hollow nanoparticles and cross-linked gelatin have been developed. The bioactive nanoparticles have a porous structure as well as high specific surface area; thus, they interact strongly with gelatin to overcome the swelling problem that a hydrophilic polymer scaffold will usually face. With this combination, these BHP-gel scaffolds showed porous structure and mechanical properties similar to those of the cancellous bone. They also showed excellent bioactivity and cell growth promotion performance in vitro. The best of them, namely, 10BHP-gel scaffold, was evaluated in vivo on a rat femur model, where it was found that the 5 mm segmental bone defect almost healed with new bone tissue formed in 12 weeks and the scaffold itself degraded at the same time. Thus, 10BHP-gel scaffold may become a potential bone graft for large segmental bone defect healing in the future.

In vivo evaluation of a novel nanocomposite porous 3D scaffold in a rabbit model: histological analysis

The healing of load-bearing segmental defects in long bones is a challenge due to the complex nature of the weight that affects the bone part and due to bending, shearing, axial, and torsional forces. An innovative porous 3D scaffolds implant of CaCO₃ aragonite nanocomposite derived from cockle shell was advanced for substitute bone solely for load-bearing cases. The biomechanical characteristics of such materials were designed to withstand cortical bone strength. In promoting bone growth to the implant material, an ideal surface permeability was formed by means of freeze drying and by adding copolymers to the materials. The properties of coating and copolymers supplement were also assessed for bone-implant connection resolutions. To examine the properties of the material in advanced biological system, an experimental trial in an animal model was carried out. Critical sized defect of bone was created in rabbit's radial bone to assess the material for a load-bearing application with a short and extended period assessment with histological evaluation of the incorporated implanted material to the bone of the host. Trials in animal models proved that the material has the capability of enduring load-bearing conditions for long-term use devoid of breaking or generating stress that affects the host bone. Histological examination further confirmed the improved integration of the implanted materials to the host bone with profound bone development into and also above the implanted scaffold, which was attained with negligible reaction of the tissues to a foreign implanted material.

[Repair of segmental bone defects in rabbits' radius with domestic porous tantalum encapsulated with pedicled fascial flap]

Objective

To investigate the effect of domestic porous tantalum encapsulated with pedicled fascial flap on repairing of segmental bone defect in rabbits' radius.

Methods

A total of 60 New Zealand white rabbits (aged 6- 8 months and weighing 2.5-3.0 kg) were randomly divided into the experimental group and control group (30 rabbits each group). A 1.5 cm segmental bone defect in right radius was established as the animal model. The porous tantalums encapsulated with pedicled fascial flaps (30 mm×20 mm) were implanted in the created bone defect in the experimental group, and the porous tantalums were only implanted in the control group. X-ray films were observed at the day after operation and at 4, 8, and 16 weeks after operation. Specimens were taken out at 4, 8, and 16 weeks after operation for HE staining and toluidine blue staining observation. The maximum load force and bending strength were detected by three point bending biomechanical test, and the Micro-CT analysis and quantitative analysis of the new bone volume fraction (BV/TV) were performed at 16 weeks after operation to compare the bone defect repair ability in vivo in 2 groups.

Results

All incisions healed by first intention without wound infection. At 4, 8, and 16 weeks after operation, the X-ray films showed that the implants were well maintained without apparent displacement. As followed with time, the combination between the implants and host bone became more and more closely, and the fracture line gradually disappeared. HE staining and toluidine blue staining showed that new bone mass and maturity gradually increased at the interface and inside materials in 2 groups, and the new bone gradually growed from the interface to internal pore. At 16 weeks after operation, the three point bending biomechanical test showed that the maximum load force and bending strength in the experimental were (96.54±7.21) N and (91.26±1.76) MPa respectively, showing significant differences when compared with the control group [(82.65±5.65) N and (78.53±1.16) MPa respectively] ( t=3.715, P=0.004; t=14.801, P=0.000). And Micro-CT analysis exhibited that there were a large amount of new bone at the interface and the surface of implant materials and inside the materials. The new bone BV/TV in the experimental group (32.63%±3.56%) was significantly higher than that in control group (25.07%±4.34%) ( t=3.299, P=0.008).

Conclusion

Domestic porous tantalum encapsulated with pedicled fascial flap can increase local blood supply, strengthen material bone conduction ability, and promote the segmental bone defect repair.

Repair of a critical-size segmental rabbit femur defect using bioglass-β-TCP monoblock, a vascularized periosteal flap and BMP-2

Various synthetic bone substitutes are not suitable for reconstructing critical-size bone defects. This study tested whether a bioglass-β-tricalcium phosphate (β-TCP) monoblock is effective for repairing critical-size segmental bone defects if combined with a vascularized periosteal flap and bone morphogenetic protein (BMP)-2. A femoral osteotomy with a gap size of 20 mm was created and stabilized using a plate in 40 rabbits.The defect was left untreated (group A) or repaired using a monoblock (group B), a monoblock with a vascularized periosteal flap (group C), or a monoblock with a vascularized periosteal flap and BMP-2 (group D). Bone regeneration, vascularization and monoblock degradation were analyzed after four and eight weeks using x-ray, hematoxylin-eosin, CD34 immunohistochemical and Masson's trichrome staining observation and histometric evaluation. The radiographic grading score showed a time-dependent increase from weeks 4 to 8. At 8-week postoperative, the total new regenerated bone in groups C and D was 20.0 ± 0.3 and 55.5 ± 8.0 mm² , respectively, which was significantly greater than in group B. Conversely, group D showed less residual monoblock than did group C. An increase in microvessel density was also observed in groups C and D compared with group B at 4 and 8 weeks postoperative, respectively. This study suggests that bioglass-β-TCP monoblock alone exhibits poor potential to repair a 20-mm femoral defect. However, supplementation with a vascularized periosteal flap and BMP-2 led to effective vascularization and reliable bone regeneration throughout the monoblock, with concordant material degradation in a timely manner. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2148-2156, 2018.

Combination of Heel-strike like Mechanical Loading with Deproteinized Cancellous Bone Scaffold Implantation to Repair Segmental Bone Defects in Rabbits

Under physiological conditions bone defects often occur at mechanical load bearing sites and bone substitutes used for regeneration should be similarly subjected to mechanical loading stress. In this study, we investigated whether a novel heel-strike like mechanical loading method can be used as a complementary therapy to promote bone regeneration following bone substitute grafting. To test this, three groups of rabbits with segmental bone defects in the tibia were implanted with bovine deproteinized cancellous bone scaffold (DCBS), with one group also receiving heel-strike like mechanical loading generated by a rap stress stimulator. From weeks 4-12 post-operation X-ray and micro-CT scanning showed that rabbits receiving combination therapy had significantly more callus at the bone defect. Moreover, bone defects in the combination group were completely replaced with new bone at week 12, while the DCBS implantation alone group healed only partially and rabbits receiving neither DCBS nor mechanical loading developed only small calluses throughout the observation period. Analysis of micro-CT scanning results demonstrated that new bone density in the combination group was significantly higher than the DCBS only group at weeks 4 and 12 (p<0.05). H&E staining results also indicated a significantly higher percentage of new bone in the bone defect area and a lower percentage of residual scaffold in the combination group compared to the DCBS only group (p<0.05). Thus, this heel-strike like mechanical loading method appears to accelerate bone regeneration following substitute implantation by restoring a local mechanical loading environment in segmental bone defects.

The effect of SDF-1α on low dose BMP-2 mediated bone regeneration by release from heparinized mineralized collagen type I matrix scaffolds in a murine critical size bone defect model

The treatment of critical size bone defects represents a challenge. The growth factor bone morphogenetic protein 2 (BMP-2) is clinically established but has potentially adverse effects when used at high doses. The aim of this study was to evaluate if stromal derived factor-1 alpha (SDF-1α) and BMP-2 released from heparinized mineralized collagen type I matrix (MCM) scaffolds have a cumulative effect on bone regeneration. MCM scaffolds were functionalized with heparin, loaded with BMP-2 and/or SDF-1α and implanted into a murine critical size femoral bone defect (control group, low dose BMP-2 group, low dose BMP-2 + SDF-1α group, and high dose BMP-2 group). After 6 weeks, both the low dose BMP-2 + SDF-1α group (5.8 ± 0.6 mm³, p = 0.0479) and the high dose BMP-2 group (6.5 ± 0.7 mm³, p = 0.008) had a significantly increased regenerated bone volume compared to the control group (4.2 ± 0.5 mm³). There was a higher healing score in the low dose BMP-2 + SDF-1α group (median grade 8; Q1-Q3 7-9; p = 0.0357) than in the low dose BMP-2 group (7; Q1-Q3 5-9) histologically. This study showed that release of BMP-2 and SDF-1α from heparinized MCM scaffolds allows for the reduction of the applied BMP-2 concentration since SDF-1α seems to enhance the osteoinductive potential of BMP-2. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2126-2134, 2016.

Masquelet technique for treatment of segmental bone loss in the upper extremity

A relatively simple technique to address large segmental bone defects in the upper extremity is described, along with a case example.

Bony defect repair in rabbit using hybrid rapid prototyping polylactic-co-glycolic acid/β-tricalciumphosphate collagen I/apatite scaffold and bone marrow mesenchymal stem cells

BACKGROUND

In bone tissue engineering, extracellular matrix exerts critical influence on cellular interaction with porous biomaterial and the apatite playing an important role in the bonding process of biomaterial to bone tissue. The aim of this study was to observe the therapeutic effects of hybrid rapid prototyping (RP) scaffolds comprising polylactic-co-glycolic acid (PLGA), β-tricalciumphosphate (β-TCP), collagen I and apatite (PLGA/β-TCP-collagen I/apatite) on segmental bone defects in conjunction with combination with bone marrow mesenchymal stem cells (BMSCs).

MATERIALS AND METHODS

BMSCs were seeded into the hybrid RP scaffolds to repair 15 mm defect in the radius of rabbits. Radiograph, microcomputed tomography and histology were used to evaluate new bone formation.

RESULTS

Radiographic analysis done from 12 to 36 weeks postoperative period demonstrated that new bone formed at the radial defect site and continues to increase until the medullary cavity is recanalized and remodelling is complete. The bone defect remained unconnected in the original RP scaffolds (PLGA/β-TCP) during the whole study. Histological observations conformed to the radiographic images. In hybrid RP scaffold group, woven bone united the radial defect at 12 weeks and consecutively remodeled into lamellar bone 24 weeks postoperation and finally matured into cortical bone with normal marrow cavity after another 12 weeks. No bone formation but connective tissue has been detected in RP scaffold at the same time.

CONCLUSION

Collagen I/apatite sponge composite coating could improve new bone formation in vivo. The hybrid RP scaffold of PLGA/β-TCP skeleton with collagen I/apatite sponge composite coating is a promising candidate for bone tissue engineering.