Bone lengthening (distraction osteogenesis): a literature review

Techniques on vertical ridge augmentation: Indications and effectiveness

Vertical ridge augmentation techniques have been advocated to enable restoring function and esthetics by means of implant-supported rehabilitation. There are three major modalities. The first is guided bone regeneration, based on the principle of compartmentalization by means of using a barrier membrane, which has been demonstrated to be technically demanding with regard to soft tissue management. This requisite is also applicable in the case of the second modality of bone block grafts. Nonetheless, space creation and maintenance are provided by the solid nature of the graft. The third modality of distraction osteogenesis is also a valid and faster approach. Nonetheless, owing to this technique's inherent shortcomings, this method is currently deprecated. The purpose of this review is to shed light on the state-of-the-art of the different modalities described for vertical ridge augmentation, including the indications, the step-by-step approach, and the effectiveness.

Open fractures: Current treatment perspective

Severe open fractures present challenges to orthopaedic surgeons worldwide, with increased risks of significant complications. Although different global regions have different resources and systems, there continue to be many consistent approaches to open fracture care. Management of these complex injures continues to evolve in areas ranging from timing of initial operative debridement to the management of critical-sized bone defects. This review, compiled by representative members of the International Orthopaedic Trauma Association, focuses on several critical areas of open fracture management, including antibiotic administration, timing of debridement, bone loss, soft tissue management, and areas of need for future investigation.

A Combination of Ilizarov Frame, Externalized Locking Plate and Tibia Bridging for an Adult with Large Tibial Defect and Severe Varus Deformity Due to Chronic Osteomyelitis in Childhood: A Case Report

Background: Various techniques have been reported to treat large, segmental tibial defects, such as autogenous bone graft, vascularized free fibula transfer and bone transport. We present a case of a 24-year-old male with a 17-year history of chronic osteomyelitis with obvious lower limb length discrepancy and severe varus deformity of the tibia secondary to osteomyelitis in childhood. Aim: The aim of this work is to provide an alternative choice for treating patients in developing countries with severe lower limb deformity caused by chronic osteomyelitis. Case Presentations: Without surgical intervention for a prolonged period of time, the patient was admitted in our institute for corrective surgery. Corrective surgery consisted of three stages: lengthening with Ilizarov frame, removal of Ilizarov frame and fixation with externalized locking plate, and removal of externalized locking plate. Tibia bridging was achieved at the distal and proximal junction. The range of motion (ROM) of the knee joint was nearly normal, but the stiffness of the ankle joint was noticeable. The remaining leg discrepancy of 0.1 cm required no application of a shoe lift. Moreover, the patient could engage in daily activities without noted limping. Conclusions: Distraction-compression osteogenesis using the Ilizarov apparatus is a powerful tool to lengthen the shortened long bone and adjust the deformity of the lower limbs. Externalized locking plates provide an alternative to the traditional bulky external fixator, as its low profile makes it more acceptable to patients without compromising axial and torsional stiffness. In all, a combination of Ilizarov frame, externalized locking plate and tibia bridging is an alternative for patients in similar conditions.

Mechanical Characterization at the Microscale of Mineralized Bone Callus after Bone Lengthening

Distraction osteogenesis (DO) involves several processes to form an organized distracted callus. While bone regeneration during DO has been widely described, no study has yet focused on the evolution profile of mechanical properties of mineralized tissues in the distracted callus. The aim of this study was therefore to measure the elastic modulus and hardness of calcified cartilage and trabecular and cortical bone within the distracted callus during the consolidation phase. We used a microindentation assay to measure the mechanical properties of periosteal and endosteal calluses; each was subdivided into two regions. Histological sections were used to localize the tissues. The results revealed that the mechanical properties of calcified cartilage did not evolve over time. However, trabecular bone showed temporal variation. For elastic modulus, in three out of four regions, a similar evolution profile was observed with an increase and decrease over time. Concerning hardness, this evolves differently depending on the location in the distracted callus. We also observed spatial changes in between regions. A first duality was apparent between regions close to the native cortices and the central area, while latter differences were seen between periosteal and endosteal calluses. Data showed a heterogeneity of mechanical properties in the distracted callus with a specific mineralization profile.

Effect of Puerarin on Osteogenic Differentiation in vitro and on New Bone Formation in vivo

Purpose

Puerarin (C₂₁H₂₀O₁₀) is a phytoestrogen that possesses various pharmacological effect, and several researches have revealed the relationship between puerarin and bone metabolism. This study was aimed to evaluate the potential influence of puerarin on the proliferation and osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (BMSCs) as well as on new bone formation following rapid maxillary expansion (RME) model in rats.

Methods

Rat BMSCs were adopted, and the cell proliferation was detected by cell-counting kit-8 (CCK-8) assay in vitro experiments. Alkaline phosphatase (ALP) activity and alizarin red staining were analyzed quantitatively to show extracellular matrix mineralization. The mRNA and protein expression levels were used to detect osteogenic differentiation of BMSCs. In vivo bone regeneration was analyzed in a rat RME model. Eighteen 6-week-old male Wistar rats were divided into 3 groups: group 1 without any treatment, group 2 received RME and saline solution (15mg/kg), group 3 received RME and puerarin solution (15mg/kg). After 2 weeks, micro-computed tomography (Micro-CT), hematoxylin and eosin (HE) staining, and Masson staining were used to detect the new bone formation and morphological changes. Besides, ALP and bone morphogenetic protein 2 (BMP2) expression levels in mid-palatal suture were evaluated by immunohistochemical staining.

Results

The results showed that puerarin upregulates cell proliferation dose-dependently. ALP activity and mineralized matrix generation were clearly enhanced at certain specific concentrations (10⁻⁵ and 10⁻⁶ mol/L); the expression levels of the osteoblast-related genes and proteins were increased. The measurement of micro-CT imaging revealed that puerarin significantly promoted new bone formation. Concomitantly, the histological examinations showed that puerarin solution enhanced osteogenesis in mid-palatal suture.

Conclusion

Those works indicated that puerarin regulates osteogenesis in vitro and exerts a beneficial impact on bone regeneration in vivo, revealing that puerarin treatment may become one of the potential keys for improving the stability and preventing relapse of RME.

Exploring the Mechanism of Total Flavonoids of Drynariae Rhizoma to Improve Large Bone Defects by Network Pharmacology and Experimental Assessment

Drynariae Rhizoma (DR) has been demonstrated to be effective in promoting fracture healing in clinical use. In the study, we tried to predicate potential signaling pathways and active ingredients of DR via network pharmacology, uncover its regulation mechanism to improve large bone defects by in vivo and in vitro experiment. We total discovered 18 potential active ingredients such as flavonoids and 81 corresponding targets, in which mitogen-activated protein kinase (MAPK) signaling pathway has the highest correlation with bone defects in pathway and functional enrichment analysis. Therefore, we hypothesized that flavonoids in DR improve large bone defects by activating MAPK signaling pathway. Animal experiments were carried out and all rats randomly divided into TFDR low, medium, and high dosage group, model group and control group. 12 weeks after treatment, according to X-ray and Micro-CT, TFDR medium dosage group significantly promote new bone mineralization compared with other groups. The results of HE and Masson staining and in vitro ALP level of BMSC also demonstrated the formation of bone matrix and mineralization in the TFDR groups. Also, angiographic imaging suggested that flavonoids in DR promoting angiogenesis in the defect area. Consistently, TFDR significantly enhanced the expression of BMP-2, RUNX-2, VEGF, HIF-1 in large bone defect rats based on ELISA and Real-Time PCR. Overall, we not only discover the active ingredients of DR in this study, but also explained how flavonoids in DR regulating MAPK signaling pathway to improve large bone defects.

Concentration Changes of Peripheral Blood Mesenchymal Stem Cells of Sprague Dawley Rats during Distraction Osteogenesis

Objectives

To observe the changes in the concentrations of circulating peripheral blood mesenchymal stem cells (PBMSCs) in Sprague Dawley (SD) rats and explore the pattern of changes in PBMSCs during the process of distraction osteogenesis.

Methods

SD rats were randomly divided into the osteotomy with lengthening group (lengthening group), the osteotomy without lengthening group (osteotomy group), and the blank control group (control group). Each group included 24 rats. Percutaneous pinning with external fixation of the left femur was carried out in lengthening group and osteotomy group, but control group received no surgical treatment. On day 5 after operation, continuous traction was carried out at a rate of 0.25 mm/d in lengthening group, while no traction was carried out in osteotomy group. Peripheral blood was collected from all rats on days 1, 3, 7, and 16 after the start of traction. PBMSCs were isolated by density gradient centrifugation. CD105, CD34, and CD45 were selected as cell surface markers. The concentration of PBMSCs was detected by flow cytometry and compared between groups at different time points. X‐ray films were taken during and after the operation to observe whether the osteotomy end was pulled and the growth and mineralization of the new bone in the osteogenic area of the femur. Color ultrasound was used to monitor the width of the distraction space, the formation of new bone, and the blood supply of soft tissue around the distraction.

Results

All rats were able to tolerate the operation well, and the external fixation was firm and reliable. X‐ray showed that, in lengthening group, the distraction space of femur gradually widened and new bone gradually formed in the distraction space; after 8 weeks, the samples were taken out, which showed that the new bone tissue in the lengthened area healed well. In osteotomy group, the average healing time of osteotomy was (7.12 ± 0.78) weeks. Ultrasonic examination showed that after the end of traction, the high echo callus shadow was seen in the traction space, and the blood flow signal was obviously rich at an earlier stage. In lengthening group and osteotomy group, the average concentrations of PBMSCs (3.02% ± 0.87% vs 2.95% ± 0.74%, respectively) were significantly increased in the early stage after osteotomy, and the average concentrations of PBMSCs on days 3, 7, and 16 after the start of traction were 5.34% ± 1.13% vs 3.28% ± 1.22%; 6.41% ± 1.05% vs 3.16% ± 0.92%; and 5.94% ± 1.23% vs 1.48% ± 0.52%, respectively. The concentration of PBMSCs in peripheral blood of lengthening group and osteotomy group was the same at osteotomy stage, and the difference between the two groups was not statistically significant (P > 0.05). After that, compared with lengthening group, the concentration of PBMSCs in osteotomy group gradually decreased and maintained at a certain level; the difference between the two groups was statistically significant (P < 0.05).

Conclusions

Distraction osteogenesis of femur can significantly increase PBMSCs in SD rats and participate in the process of bone formation.

Mechanobiology of Bone Consolidation During Distraction Osteogenesis: Bone Lengthening Vs. Bone Transport

Bone lengthening and bone transport are regeneration processes that commonly rely on distraction osteogenesis, a widely accepted surgical procedure to deal with numerous bony pathologies. Despite the extensive study in the literature of the influence of biomechanical factors, a lack of knowledge about their mechanobiological differences prevents a clinical particularization. Bone lengthening treatments were performed on sheep metatarsus by reproducing the surgical and biomechanical protocol of previous bone transport experiments. Several in vivo monitoring techniques were employed to build an exhaustive comparison: gait analysis, radiographic and CT assessment, force measures through the fixation, or mechanical characterization of the new tissue. A significant initial loss of the bearing capacity, quantified by the ground reaction forces and the limb contact time with the ground, is suffered by the bone lengthening specimens. The potential effects of this anomaly on the musculoskeletal force distribution and the evolution of the bone callus elastic modulus over time are also analyzed. Imaging techniques also seem to reveal lower bone volume in the bone lengthening callus than in the bone transport one, but an equivalent mineralization rate. The simultaneous quantification of biological and mechanical parameters provides valuable information for the daily clinical routine and numerical tools development.

Retraction of transporting bone segment during Ilizarov bone transport

BACKGROUND

Retraction of transporting bone segment (TBS) may occur when the fixator of the TBS is removed prior to full consolidation of the distracted callus, which has adverse effect on the healing of the docking site. However, there are few reports on the retraction of TBS. The purpose of this study is to analyze the causes and risk factors of the retraction of TBS.

METHODS

The clinical data of 37 cases with tibial bone defect treated by Ilizarov bone transport were analyzed retrospectively, in whom the TBS fixator was removed prior to full consolidation of the distracted callus and union of the docking site. Bivariate correlation was used to analyze relationship between the retraction distance of TBS and potential risk factors including age, gender, course, length of bone defect, number of operations, size of TBS, transport distance, timing and time interval of removal of TBS fixator. Risk factors with significant level were further identified using multivariate linear regression.

RESULTS

Bivariate correlation showed that the timing of removal was negatively correlated with the retraction distance, and the time interval and transport distance were positively correlated with the retraction distance(p < 0.05), the age, gender, course, length of bone defect, size of TBS and number of operations were not correlated with the retraction distance(p > 0.05). Multivariate linear regression of the 3 risk factors showed that the timing of removal and time interval were the main risk factors affecting the retraction distance (p < 0.05), but the transport distance was not (p > 0.05).

CONCLUSION

The traction forces of TBS endured from the soft tissues and the unconsolidated distracted callus have elastic properties, which can make retraction of TBS. The timing of removal and time interval are the main risk factors of the retraction of TBS. In the case of early removal, another external fixation or quickly converted to internal fixation should be performed to avoid the adverse effect of more retraction.

Flexible and Expandable Robot for Tissue Therapies - Modeling and Design

OBJECTIVE

Implantable technologies should be mechanically compliant with the tissue in order to maximize tissue quality and reduce inflammation during tissue reconstruction. We introduce the development of a flexible and expandable implantable robotic (FEIR) device for the regenerative elongation of tubular tissue by applying controlled and precise tension to the target tissue while minimizing the forces produced on the surrounding tissue.

METHODS

We introduce a theoretical framework based on iterative beam theory static analysis for the design of an expandable robot with a flexible rack. The model takes into account the geometry and mechanics of the rack to determine a trade-off between its stiffness and capability to deliver the required tissue tension force. We empirically validate this theory on the benchtop and with biological tissue.

RESULTS

We show that FEIR can apply the required therapeutical forces on the tissue while reducing the amount of force it applies to the surrounding tissues as well as reducing self-damage.

CONCLUSION

The study demonstrates a method to develop robots that can change size and shape to fit their dynamic environment while maintaining the precision and delicacy necessary to manipulate tissue by traction.

SIGNIFICANCE

The method is relevant to designers of implantable technologies. The robot is a precursor medical device for the treatment of Long-Gap Esophageal Atresia and Short Bowel Syndrome.

Percutaneous CO2 Treatment Accelerates Bone Generation During Distraction Osteogenesis in Rabbits

BACKGROUND

Distraction osteogenesis has been broadly used to treat various structural bone deformities and defects. However, prolonged healing time remains a major problem. Various approaches including the use of low-intensity pulsed ultrasound, parathyroid hormone, and bone morphogenetic proteins (BMPs) have been studied to shorten the treatment period with limited success. Our previous studies of rats have reported that the transcutaneous application of CO2 accelerates fracture repair and bone-defect healing in rats by promoting angiogenesis, blood flow, and endochondral ossification. This therapy may also accelerate bone generation during distraction osteogenesis, but, to our knowledge, no study investigating CO2 therapy on distraction osteogenesis has been reported.

QUESTIONS/PURPOSES

We aimed to investigate the effect of transcutaneous CO2 during distraction osteogenesis in rabbits, which are the most suitable animal as a distraction osteogenesis model for a lengthener in terms of limb size. We asked: Does transcutaneous CO2 during distraction osteogenesis alter (1) radiographic bone density in the distraction gap during healing; (2) callus parameters, including callus bone mineral content, volumetric bone mineral density, and bone volume fraction; (3) the newly formed bone area, cartilage area, and angiogenesis, as well as the expression of interleukin-6 (IL-6), BMP-2, BMP-7, hypoxia-inducible factor (HIF) -1α, and vascular endothelial growth factor (VEGF); and (4) three-point bend biomechanical strength, stiffness, and energy?

METHODS

Forty 24-week-old female New Zealand white rabbits were used according to a research protocol approved by our institutional ethical committee. A distraction osteogenesis rabbit tibia model was created as previously described. Briefly, an external lengthener was applied to the right tibia, and a transverse osteotomy was performed at the mid-shaft. The osteotomy stumps were connected by adjusting the fixator to make no gap. After a 7-day latency phase, distraction was continued at 1 mm per day for 10 days. Beginning the day after the osteotomy, a 20-minute transcutaneous application of CO2 on the operated leg using a CO2 absorption-enhancing hydrogel was performed five times per week in the CO2 group (n = 20). Sham treatment with air was administered in the control group (n = 20). Animals were euthanized immediately after the distraction period (n = 10), 2 weeks (n = 10), and 4 weeks (n = 20) after completion of distraction. We performed bone density quantification on the plain radiographs to evaluate consolidation in the distraction gap with image analyzing software. Callus parameters were measured with micro-CT to assess callus microstructure. The newly formed bone area and cartilage area were measured histologically with safranin O/fast green staining to assess the progress of ossification. We also performed immunohistochemical staining of endothelial cells with fluorescein-labeled isolectin B4 and examined capillary density to evaluate angiogenesis. Gene expressions in newly generated callus were analyzed by real-time polymerase chain reaction. Biomechanical strength, stiffness, and energy were determined from a three-point bend test to assess the mechanical strength of the callus.

RESULTS

Radiographs showed higher pixel values in the distracted area in the CO2 group than the control group at Week 4 of the consolidation phase (0.98 ± 0.11 [95% confidence interval 0.89 to 1.06] versus 1.19 ± 0.23 [95% CI 1.05 to 1.34]; p = 0.013). Micro-CT demonstrated that bone volume fraction in the CO2 group was higher than that in the control group at Week 4 (5.56 ± 3.21 % [95% CI 4.32 to 6.12 %] versus 11.90 ± 3.33 % [95% CI 9.63 to 14.25 %]; p = 0.035). There were no differences in any other parameters (that is, callus bone mineral content at Weeks 2 and 4; volumetric bone mineral density at Weeks 2 and 4; bone volume fraction at Week 2). At Week 2, rabbits in the CO2 group had a larger cartilage area compared with those in the control group (2.09 ± 1.34 mm [95% CI 1.26 to 2.92 mm] versus 5.10 ± 3.91 mm [95% CI 2.68 to 7.52 mm]; p = 0.011). More newly formed bone was observed in the CO2 group than the control group at Week 4 (68.31 ± 16.32 mm [95% CI 58.19 to 78.44 mm] versus 96.26 ± 19.37 mm [95% CI 84.25 to 108.26 mm]; p < 0.001). There were no differences in any other parameters (cartilage area at Weeks 0 and 4; newly formed bone area at Weeks 0 and 2). Immunohistochemical isolectin B4 staining showed greater capillary densities in rabbits in the CO2 group than the control group in the distraction area at Week 0 and surrounding tissue at Weeks 0 and 2 (distraction area at Week 0, 286.54 ± 61.55 /mm [95% CI 232.58 to 340.49] versus 410.24 ± 55.29 /mm [95% CI 361.78 to 458.71]; p < 0.001; surrounding tissue at Week 0 395.09 ± 68.16/mm [95% CI 335.34 to 454.83] versus 589.75 ± 174.42/mm [95% CI 436.86 to 742.64]; p = 0.003; at Week 2 271.22 ± 169.42 /mm [95% CI 122.71 to 419.73] versus 508.46 ± 49.06/mm [95% CI 465.45 to 551.47]; p < 0.001 respectively). There was no difference in the distraction area at Week 2. The expressions of BMP -2 at Week 2, HIF1-α at Week 2 and VEGF at Week 0 and 2 were greater in the CO2 group than in the control group (BMP -2 at Week 2 3.84 ± 0.83 fold [95% CI 3.11 to 4.58] versus 7.32 ± 1.63 fold [95% CI 5.88 to 8.75]; p < 0.001; HIF1-α at Week 2, 10.49 ± 2.93 fold [95% CI 7.91 to 13.06] versus 20.74 ± 11.01 fold [95% CI 11.09 to 30.40]; p < 0.001; VEGF at Week 0 4.80 ± 1.56 fold [95% CI 3.43 to 6.18] versus 11.36 ± 4.82 fold [95% CI 7.13 to 15.59]; p < 0.001; at Week 2 31.52 ± 8.26 fold [95% CI 24.27 to 38.76] versus 51.05 ± 15.52 fold [95% CI 37.44 to 64.66]; p = 0.034, respectively). There were no differences in any other parameters (BMP-2 at Week 0 and 4; BMP -7 at Weeks 0, 2 and 4; HIF-1α at Weeks 0 and 4; IL-6 at Weeks 0, 2 and 4; VEGF at Week 4). In the biomechanical assessment, ultimate stress and failure energy were greater in the CO2 group than in the control group at Week 4 (ultimate stress 259.96 ± 74.33 N [95% CI 167.66 to 352.25] versus 422.45 ± 99.32 N [95% CI 299.13 to 545.77]; p < 0.001, failure energy 311.32 ± 99.01 Nmm [95% CI 188.37 to 434.25] versus 954.97 ± 484.39 Nmm [95% CI 353.51 to 1556.42]; p = 0.003, respectively). There was no difference in stiffness (216.77 ± 143.39 N/mm [95% CI 38.73 to 394.81] versus 223.68 ± 122.17 N/mm [95% CI 71.99 to 375.37]; p = 0.92).

CONCLUSION

Transcutaneous application of CO2 accelerated bone generation in a distraction osteogenesis model of rabbit tibias. As demonstrated in previous studies, CO2 treatment might affect bone regeneration in distraction osteogenesis by promoting angiogenesis, blood flow, and endochondral ossification.

CLINICAL RELEVANCE

The use of the transcutaneous application of CO2 may open new possibilities for shortening healing time in patients with distraction osteogenesis. However, a deeper insight into the mechanism of CO2 in the local tissue is required before it can be used in future clinical practice.

Biodegradable Magnesium-Based Implants in Orthopedics-A General Review and Perspectives

Biodegradable Mg-based metals may be promising orthopedic implants for treating challenging bone diseases, attributed to their desirable mechanical and osteopromotive properties. This Review summarizes the current status and future research trends for Mg-based orthopedic implants. First, the properties between Mg-based implants and traditional orthopedic implants are compared on the following aspects: in vitro and in vivo degradation mechanisms of Mg-based implants, peri-implant bone responses, the fate of the degradation products, and the cellular and molecular mechanisms underlying the beneficial effects of Mg ions on osteogenesis. Then, the preclinical studies conducted at the low weight bearing sites of animals are introduced. The innovative strategies (for example, via designing Mg-containing hybrid systems) are discussed to address the limitations of Mg-based metals prior to their clinical applications at weight-bearing sites. Finally, the available clinical studies are summarized and the challenges and perspectives of Mg-based orthopedic implants are discussed. Taken together, the progress made on the development of Mg-based implants in basic, translational, and clinical research has laid down a foundation for developing a new era in the treatment of challenging and prevalent bone diseases.

A novel adjustable locking plate (ALP) for segmental bone fracture treatment

A novel Ti6Al4V adjustable locking plate (ALP) is designed to provide enhanced bone stability for segmental bone fractures and to allow precise positioning of disconnected segments. The design incorporates an adjustable rack and pinion mechanism to perform compression, distraction and segment transfer during plate fixation surgery. The aim of this study is to introduce the advantages of the added feature and computationally characterize the biomechanical performance of the proposed design. Structural strength of the novel plate is analyzed using numerical methods for 4-point bending and fatigue properties, following ASTM standards. An additional mechanical failure finite element test is also conducted on the rack and pinion to reveal how much torque can be safely applied to the mechanism by the surgeon. Simulation results predict that the new design is sufficiently strong to not fail under regular anatomical loading scenarios with close bending strength and fatigue life properties to clinically used locking compression plates. The novel ALP design is expected to be a good candidate for addressing problems regarding fixation of multi-fragmentary bone fractures.

Regenerative medicine in lower limb reconstruction

Bone is a highly specialized connective tissue and has a rare quality as one of the few tissues that can repair without a scar to regain pre-injury structure and function. Despite the excellent healing capacity of bone, tumor, infection, trauma and surgery can lead to significant bone loss requiring skeletal augmentation. Bone loss in the lower limb poses a complex clinical problem, requiring reconstructive techniques to restore form and function. In the past, amputation may have been the only option; however, there is now an array of reconstructive possibilities and cellular therapies available to salvage a limb. In this review, we will evaluate current applications of bone tissue engineering techniques in limb reconstruction and identify potential strategies for future work.

Effect of bone marrow stromal cells in combination with biomaterials in early phases of distraction osteogenesis: An experimental study in a rabbit femur model

Acceleration of the consolidation of the distracted bone is a relevant medical need. As a platform to improve in vivo bone engineering, we developed a novel distraction osteogenesis (DO) model in a rabbit large bone (femur) and tested if the application of cultured bone marrow stromal cells (BMSCs) immediately after the osteotomy promotes the formation of bone. This report consists of two components, an animal study to evaluate the quality of the regenerate following different treatments and an in vitro study to evaluate osteogenic potential of BMSC cultures. To illuminate the mechanism of action of injected cells, we tested stem cell cultures enriched in osteogenic-BMSCs (O-BMSCs) as compared with cultures enriched in non-osteogenic BMSCs (NO-BMSCs). Finally, we included a group of animals treated with biomaterials (fibrin and ground cortical bone) in addition to cells. Injection of O-BMSCs promoted the maturity of distracted callus and decreased fibrosis. When combined with biomaterials, O-BMSCs modified the ossification pattern from endochondral to intramembranous type. The use of NO-BMSCs not only did not increase the maturity but also increased porosity of the bone. These preclinical results indicate that the BMSC cultures must be tested in vitro prior to clinical use, since a number of factors may influence their outcome in bone formation. We hypothesize that the use of osteogenic BMSCs and biomaterials could be clinically beneficial to shorten the consolidation period of the distraction and the total period of bone lengthening.

Biomaterials Enabled Cell-Free Strategies for Endogenous Bone Regeneration

Repairing bone defects poses a major orthopedic challenge because current treatments are constrained by the limited regenerative capacity of human bone tissue. Novel therapeutic strategies, such as stem cell therapy and tissue engineering, have the potential to enhance bone healing and regeneration, and hence may improve quality of life for millions of people. However, the ex vivo expansion of stem cells and their in vivo delivery pose technical difficulties that hamper clinical translation and commercial development. A promising alternative to cell delivery-based strategies is to stimulate or augment the inherent self-repair mechanisms of the patient to promote endogenous restoration of the lost/damaged bone. There is growing evidence indicating that increasing the endogenous regenerative potency of bone tissues for therapeutics will require the design and development of new generations of biomedical devices that provide key signaling molecules to instruct cell recruitment and manipulate cell fate for in situ tissue regeneration. Currently, a broad range of biomaterial-based deployment technologies are becoming available, which allow for controlled spatial presentation of biological cues required for endogenous bone regeneration. This article aims to explore the proposed concepts and biomaterial-enabled strategies involved in the design of cell-free endogenous techniques in bone regenerative medicine.

Combined application of latissimus dorsi myocutaneous flap and iliac bone flap in the treatment of chronic osteomyelitis of the lower extremity

Background

To evaluate the clinical efficacy and safety of latissimus dorsi myocutaneous flap (stage I) combined with iliac bone flap (stage II) in the treatment of chronic osteomyelitis of the lower extremity.

Methods

Clinical data of 18 patients undergoing latissimus dorsi myocutaneous flap in combination with iliac bone flap grafting were retrospectively analyzed. Among them, 2 patients developed chronic osteomyelitis of the lower segment of the femur, 4 were diagnosed with chronic osteomyelitis of the tibial plateau, and 12 with chronic osteomyelitis of the lower segment of the tibia.

Results

All the latissimus dorsi myocutaneous flaps survived in 18 patients. After the corresponding surgery, primary wound healing was achieved in 11 patients, and delayed wound healing was obtained in 7 cases. All wounds were completely healed with postoperative 2 months. Following the iliac bone flap grafting, primary would healing was accomplished in all cases. All dorsal window chambers survived. The bone defects were properly restored within 4–12 postoperative months. Functional training was performed after removal of the internal and external fixators. Postoperative follow-up was endured from 6 months to 10 years. All patients were satisfied with the bone healing and flap texture without the incidence of osteomyelitis and sinus tract. No contraction was observed in the grafting area of 2 patients receiving latissimus dorsi myocutaneous flap grafting. Residual linear scars were noted in the dorsal and iliac donor sites.

Conclusion

Combined usage of stage I latissimus dorsi myocutaneous flap and stage II iliac bone flap grafting is an efficacious and safe surgical technique in clinical practice.

Sclerostin antibody enhances bone formation in a rat model of distraction osteogenesis

Neutralizing monoclonal sclerostin antibodies are effective in promoting bone formation at a systemic level and in orthopedic scenarios including closed fracture repair. In this study we examined the effects of sclerostin antibody (Scl-Ab) treatment on regenerate volume, density, and strength in a rat model of distraction osteogenesis. Surgical osteotomy was performed on 179 Sprague Dawley rats. After 1 week, rats underwent distraction for 2 weeks, followed by 6 weeks for consolidation. Two treatment groups received biweekly subcutaneous Scl-AbIII (a rodent form of Scl-Ab; 25 mg/kg), either from the start of distraction onward or restricted to the consolidation phase. These groups were compared to controls receiving saline. Measurement modalities included longitudinal DXA, ex vivo QCT, and microCT, tissue histology, and biomechanical four-point bending tests. Bone volume was increased in both Scl-Ab treatments regimens by the end of consolidation (+26-38%, p < 0.05), as assessed by microCT. This was associated with increased mineral apposition. Importantly, Scl-Ab led to increased strength in united bones, and this reached statistical significance in animals receiving Scl-Ab during consolidation only (+177%, p < 0.01, maximum load to failure). These data demonstrate that Scl-Ab treatment increases bone formation, leading to regenerates with higher bone volume and improved strength. Our data also suggest that the optimal effects of Scl-Ab treatment are achieved in the latter stages of distraction osteogenesis. These findings support further investigation into the potential clinical application of sclerostin antibody to augment bone distraction, such as limb lengthening, particularly in the prevention of refracture. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1106-1113, 2018.

Femoral nonunion with segmental bone defect treated by distraction osteogenesis with monolateral external fixation

BACKGROUND

Currently, the common treatment for femoral nonunion with large segmental bone defect is difficult and complex. The effective surgical methods are rare, include vascularized bone grafting, Masquelet technique and Ilizarov distraction osteogenesis. The objective of this study is to investigate the outcomes of segmental femoral defects treated with monolateral external fixation using the distraction osteogenesis.

METHODS

We retrospectively analyzed patients with femoral nonunion with segmental bone defects (> 6 cm) between January 2010 and January 2014 in our single trauma center. All patients were treated by distraction osteogenesis with monolateral external fixation. All surgeries were performed by the same surgeon. Bone union, duration of distraction osteogenesis in days, time to consolidation in months, external fixation index (EFI), complications, and additional surgical interventions were recorded postoperatively. The modified Application of Methods of Illizarov (ASAMI) criteria were used to evaluate the operative effectiveness.

RESULTS

Forty-one patients were enrolled in this study for analysis. The length of the bone defect ranged from 6 to 17 cm. All patients eventually achieved healing, and no patient experienced recurrence of infection or newly developed infection. The average time needed for healing was 13 months. In terms of the incidence of complications, 3 cases axial deviations, 5 cases docking site nonunion, 23 cases pin-tract infection, 14 cases knee joint stiffness or their joint mobility declined, 2 cases osteogenesis insufficient in the distraction area,1 case refracture, and 2 cases loose external fixation pins. In terms of the evaluations of fracture healing and function, 30 patients excellent, 6 patients good, 5 patients fair, and 0 patient poor. In terms of postoperative function evaluations, 21 patients excellent, 9 patients good, 7 patients fair, and 4 patients poor.

CONCLUSION

For patients with femoral nonunion with large segmental bone defects, the monolateral external fixation can provide effective stability, improve compliance, and reduce complications.

Limb lengthening and deformity correction of congenital and acquired deformities in children using the Taylor Spatial Frame

Background and purpose - Hexapod ring fixators such as the Taylor Spatial Frame (TSF) have shown good outcomes. However, there have only been a few studies comparing the use of TSF with various etiologies of the deformity. We compared the use of TSF in congenital and acquired deformities in children. Patients and methods - We reviewed 213 lower extremity reconstructive procedures with the TSF in 192 patients who were operated between October 2000 and October 2015. 128 procedures (67 proximal tibiae, 51 distal femora, and 10 distal tibiae) in 117 children (median age 14 (4-18) years; 59 girls) fulfilled the inclusion criteria. 89 procedures were done in children with congenital deformities (group C) and 39 were done in children with acquired deformities (group A). Outcome parameters were lengthening and alignment achieved, lengthening index, complications, and analysis of residual deformity in a subgroup of patients. Results - Mean lengthening achieved was 3.9 (1.0-7.0) cm in group C and 3.7 (1.0-8.0) cm in group A (p = 0.5). Deformity parameters were corrected to satisfaction in all but 3 patients, who needed further surgery for complete deformity correction. However, minor residual deformity was common in one-third of the patients. The mean lengthening index was 2.2 (0.8-10) months/cm in group C and 2.0 (0.8-6) months/cm in group A (p = 0.7). Isolated analysis of all tibial and femoral lengthenings showed similar lengthening indices between groups. Complication rates and the need for secondary surgery were much greater in the group with congenital deformities. Interpretation - The TSF is an excellent tool for the correction of complex deformities in children. There were similar lengthening indices in the 2 groups. However, congenital deformities showed a high rate of complications, and should therefore be addressed with care.

Clinical evaluation of patients submitted to osteogenic distraction in the lower limb at a university hospital

Objective

To evaluate the clinical characteristics from patients submitted to osteogenic distraction to correct bone gap at a university hospital.

Methods

Retrospective transversal study, with a convenience sample, from 2000 to 2012, evaluating clinical aspects of patients treated, submitted to osteogenic distraction (bone transport) with Ilizarov's external fixation device. The chi-squared, Fisher's, and Mann–Whitney's U tests were used with a 5% level of significance (p < 0.05).

Results

33 patients were studied, of whom 28 men (84.8%). The more frequent age was from 21 to 40 years. Most patients were from the metropolitan region of the capital (57.6%). The leg was the most affected limb (75.8%), and the left side was the most affected (66.7%). The most common cause was infected pseudoarthrosis (75.8%). The most common bone transportation type was bifocal (75.8%). Mean previous surgery at others institutions were 2.62 (1.93 standard deviation), and mean surgeries after treatment were 1.89 (1.29 standard deviation). Ilizarov's external fixation device was used for 1.94 years (1.34 mean deviation), from one to six years. The most common complications were pin infection (57.6%), equinus (30.3%), deep infection (24.2%), and shortening (21.2%).

Conclusion

Osteogenic distraction for bone gaps were more frequent in young adults, men, in the leg, with bifocal transportation, after several previous surgeries, treated for a mean of two years, with many complications (infections were the most common).

Review of the cellular and biological principles of distraction osteogenesis: An in vivo bioreactor tissue engineering model

Distraction osteogenesis (DO) is a widely used technique in plastic and orthopaedic surgery. During the process, mechanical force is applied to fractured bone to enhance the regenerative processes and induce new bone formation. Although there is an abundance of literature on the clinical process of DO, there is a distinct lack of focus on the underlying biological principles governing this process. DO follows the basic premises of tissue engineering. The mechanical stress stimulates mesenchymal stem cell differentiation down an osteoblastic lineage on a matrix background. The aim of this review is to give an overview of the current knowledge of the molecular mechanism governing this process.

Prediction of Clinically Significant Leg-Length Discrepancy in Congenital Disorders

Leg-length discrepancy greater than 2 to 2.5 cm can potentially have an adverse effect on our walking and standing mechanisms and requires proper correction involving surgical treatment. However, for minor leg-length discrepancy in childhood, decision making for the indications for and timing of epiphysiodesis is difficult because of unpredictable final discrepancy. The purpose of this study was to analyze longitudinal changes of minor leg-length discrepancy in congenital disorders and to determine earlier predictive values for the clinically significant discrepancy. Twenty-one patients with congenital disorders who had minor leg-length discrepancy less than 2 cm at the first presentation were retrospectively evaluated. The patients were divided into 2 groups according to leg-length discrepancy at latest follow-up: the significant group (n=11) had 25 mm or more of leg-length discrepancy and the minor group (n=10) had less than 25 mm of leg-length discrepancy. The authors evaluated longitudinal changes of leg-length discrepancy within the first 10 years by mixed-effects regression model. All patients showed monotonically increasing leg-length discrepancy with age, except for 2 (neurofibromatosis type 1 and macrodactyly of the foot) who demonstrated fluctuating leg-length discrepancy. Mean annual rate of leg-length discrepancy change in the significant group was 2.1 mm across the first decade of life and was significantly larger than that in the minor group (difference in slope, 1.3 mm; P<.0001). In minor leg-length discrepancy associated with congenital disorders, the incidence of clinically significant leg-length discrepancy can be predictable by the annual rate of leg-length discrepancy change in the first decade of life.

Demineralized Bone Matrix Injection in Consolidation Phase Enhances Bone Regeneration in Distraction Osteogenesis via Endochondral Bone Formation

Background

Distraction osteogenesis (DO) is a promising tool for bone and tissue regeneration. However, prolonged healing time remains a major problem. Various materials including cells, cytokines, and growth factors have been used in an attempt to enhance bone formation. We examined the effect of percutaneous injection of demineralized bone matrix (DBM) during the consolidation phase on bone regeneration after distraction.

Methods

The immature rabbit tibial DO model (20 mm length-gain) was used. Twenty-eight animals received DBM 100 mg percutaneously at the end of distraction. Another 22 animals were left without further procedure (control). Plain radiographs were taken every week. Postmortem bone dual-energy X-ray absorptiometry and micro-computed tomography (micro-CT) studies were performed at the third and sixth weeks of the consolidation period and histological analysis was performed.

Results

The regenerate bone mineral density was higher in the DBM group when compared with that in the saline injection control group at the third week postdistraction. Quantitative analysis using micro-CT revealed larger trabecular bone volume, higher trabecular number, and less trabecular separation in the DBM group than in the saline injection control group. Cross-sectional area and cortical thickness at the sixth week postdistraction, assessed using micro-CT, were greater in the regenerates of the DBM group compared with the control group. Histological evaluation revealed higher trabecular bone volume and trabecular number in the regenerate of the DBM group. New bone formation was apparently enhanced, via endochondral ossification, at the site and in the vicinity of the injected DBM. DBM was absorbed slowly, but it remained until the sixth postoperative week after injection.

Conclusions

DBM administration into the distraction gap at the end of the distraction period resulted in a significantly greater regenerate bone area, trabecular number, and cortical thickness in the rabbit tibial DO model. These data suggest that percutaneous DBM administration at the end of the distraction period or in the early consolidation period may stimulate regenerate bone formation and consolidation in a clinical situation with delayed bone healing during DO.

Proximal migration of fibular malleolus during tibial lengthening despite syndesmotic screw fixation: a series of 22 cases

INTRODUCTION

During tibial lengthening procedures, it is recommended to prevent fibular malleolus proximal migration using a distal tibiofibular syndesmotic screw, which is removed at 6 months. We have observed proximal migrations of the fibular malleolus despite placement of this syndesmotic screw.

OBJECTIVE

The objective of this study was to demonstrate this migration and to study the influence of two factors that may favor its occurrence: positioning of the syndesmotic screw and union of the fibula at the time of removal.

HYPOTHESIS

An unhealed fibula at the time the distal tibiofibular syndesmotic screw is removed and its tricortical position promote the proximal migration of the fibular malleolus.

MATERIAL AND METHODS

This was a retrospective, single-center, analytical study that included 22 lengthening procedures in 18 patients from 5 to 17 years of age who had undergone tibial lengthening and presented a preoperative continuous fibula. The position of the fibular malleolus, union of the fibula, and the tri- or quadricortical position of the screw were assessed based on four successive x-rays.

RESULTS

Tricortical positioning of the syndesmotic screw was significantly associated with proximal migration of the fibular malleolus during lengthening (P=0.0248<0.05). However, there was no significant relation between an unhealed fibula and proximal migration of the fibular malleolus when the screw was removed (P=0.164>0.05).

DISCUSSION

Proximal migration of the fibular malleolus during lengthening is promoted by placing a non-quadricortical syndesmotic screw. Quadricortical positioning of the screw should be recommended. Migration of the fibular malleolus after ablation of the syndesmotic screw seems to be related to absence of fibular union but this series was too small to demonstrate this clearly.

LEVEL OF EVIDENCE

Level IV: Retrospective study.

Durations of bone consolidation and external fixation after distraction osteogenesis in dogs

OBJECTIVE

To evaluate the influence of epidemiologic, surgical, and mechanical factors on the durations of bone consolidation and external fixation after distraction osteogenesis in dogs.

STUDY DESIGN

Retrospective cohort study.

SAMPLE POPULATION

Dogs (n = 115) that had corrective osteotomy with circular external fixation (CEF; n = 152) METHODS: Medical and radiographic records (1992-2012) of dogs that had corrective osteotomies were reviewed. Putative variables included age, weight, gender, and breed. Surgery date, delay before distraction, rate and duration of distraction, mechanical complications, and frame removal date were recorded. Radiographic data included bone operated, bone length, osteotomy site, bone and limb size at osteotomy site, distraction distance, and CEF frame size and stiffness.

RESULTS

Mean ± SD bone consolidation period was 56 ± 33 days. Mean duration of external fixation was 77 ± 35 days. Twelve fixation failures occurred. Radii healed faster than tibiae (P < .001). Failure of fixation (P = .002) and stiff frames (P = .033) increased duration of bone consolidation. For the tibia, durations of bone consolidation and external fixation decreased with larger bone size relative to limb size (P = .004). For the radius, bone consolidation duration decreased as distraction amount increased (P = .03).

CONCLUSION

Radii healed faster than tibiae. Wearing frames with low or moderate stiffness, the absence of mechanical complications, a larger distraction distance, and a larger bone size accelerated bone consolidation. Optimizing these factors should accelerate bone consolidation and reduce the duration of external fixation.

Growth factors in human serum during operative tibial lengthening with the Ilizarov method

Despite the widespread clinical use of distraction osteogenesis for limb lengthening, the cellular and molecular mechanisms by which this surgical treatment promotes new bone formation in humans are not well understood. The aim of the research was to study the levels of growth factors (GFs) in the serum of patients that were undergoing tibial lengthening with the Ilizarov method of distraction osteogenesis. Those were patients with unilateral congenital discrepancy of the tibia (n = 12), unilateral posttraumatic tibial shortening (n = 7), and healthy patients that underwent cosmetic bilateral tibial lengthening (n = 10). The study established that unlike the congenital group, the posttraumatic group and healthy subjects showed a significantly evident increase in the levels of angiogenic GFs in their serum on day 10 of distraction. In the congenital group, the changes were not significant at this time point. The levels of TGF-α, TGF-β1, and TGF-β2 tended to decrease on day 10 of distraction and on day 30 of the post-distraction period in the cosmetic and posttraumatic groups while they grew in the congenital group. Most dynamic changes in the GFs levels during tibial lengthening were noted in the subjects undergoing cosmetic lengthening, and the least ones were in the congenital group.

Bone Regeneration Based on Tissue Engineering Conceptions - A 21st Century Perspective

The role of Bone Tissue Engineering in the field of Regenerative Medicine has been the topic of substantial research over the past two decades. Technological advances have improved orthopaedic implants and surgical techniques for bone reconstruction. However, improvements in surgical techniques to reconstruct bone have been limited by the paucity of autologous materials available and donor site morbidity. Recent advances in the development of biomaterials have provided attractive alternatives to bone grafting expanding the surgical options for restoring the form and function of injured bone. Specifically, novel bioactive (second generation) biomaterials have been developed that are characterised by controlled action and reaction to the host tissue environment, whilst exhibiting controlled chemical breakdown and resorption with an ultimate replacement by regenerating tissue. Future generations of biomaterials (third generation) are designed to be not only osteoconductive but also osteoinductive, i.e. to stimulate regeneration of host tissues by combining tissue engineering and in situ tissue regeneration methods with a focus on novel applications. These techniques will lead to novel possibilities for tissue regeneration and repair. At present, tissue engineered constructs that may find future use as bone grafts for complex skeletal defects, whether from post-traumatic, degenerative, neoplastic or congenital/developmental "origin" require osseous reconstruction to ensure structural and functional integrity. Engineering functional bone using combinations of cells, scaffolds and bioactive factors is a promising strategy and a particular feature for future development in the area of hybrid materials which are able to exhibit suitable biomimetic and mechanical properties. This review will discuss the state of the art in this field and what we can expect from future generations of bone regeneration concepts.

Single bout short duration fluid shear stress induces osteogenic differentiation of MC3T3-E1 cells via integrin β1 and BMP2 signaling cross-talk

Fluid shear stress plays an important role in bone osteogenic differentiation. It is traditionally believed that pulsed and continuous stress load is more favorable for fracture recovery and bone homeostasis. However, according to our clinical practice, we notice that one single stress load is also sufficient to trigger osteogenic differentiation. In the present study, we subject osteoblast MC3T3-E1 cells to single bout short duration fluid shear stress by using a parallel plate flow system. The results show that 1 hour of fluid shear stress at 12 dyn/cm² promotes terminal osteogenic differentiation, including rearrangement of F-actin stress fiber, up-regulation of osteogenic genes expression, elevation of alkaline phosphatase activity, secretion of type I collagen and osteoid nodule formation. Moreover, collaboration of BMP2 and integrin β1 pathways plays a significant role in such differentiation processes. Our findings provide further experimental evidence to support the notion that single bout short duration fluid shear stress can promote osteogenic differentiation.

The effect of heparan sulfate application on bone formation during distraction osteogenesis

Bone morphogenetic proteins (BMPs) are recognized for their ability to induce bone formation in vivo and in vitro. Their osteogenic and osteoinductive properties are tightly regulated by the secretion of specific BMP antagonists, which have been shown to physically bind and sometimes be blocked by the extracellular proteoglycan heparan sulphate side chains (from hereon referred to as HS). The purpose of this study was to investigate if local application of 5 µg of HS proteoglycan to a bone regenerate site in a mouse model of distraction osteogenesis (DO) can accelerate bone healing and affect the expression of key members of the BMP signaling pathway. DO was performed on the right tibia of 115 adult male wild-type mice. At mid-distraction (day 11), half the group was injected locally with 5 µg of HS, while the other half was injected with saline. The mice were sacrificed at 2 time-points: mid-consolidation (34 days) and full consolidation (51 days). The distracted tibial zone was then collected for analysis by μCT, radiology, biomechanical testing, immunohistochemistry, and histology. While μCT data showed no statistically significant difference in bone formation, the results of biomechanical testing in stiffness and ultimate force were significantly lower in the HS-injected bones at 51 days, compared to controls. Immunohistochemistry results also suggested a decrease in expression of several key members of the BMP signaling pathway at 34 days. Furthermore, wound dehiscence and infection rates were significantly elevated in the HS group compared to the controls, which resulted in a higher rate of euthanasia in the treatment group. Our findings demonstrate that exogenous application of 5 µg of HS in the distracted gap of a murine model had a negative impact on bone and wound healing.