Percutaneous autogenous bone marrow grafting in 20 cases of ununited fracture

The Identification of Marker Genes for Predicting the Osteogenic Differentiation Potential of Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSCs) have the potential to differentiate into a variety of mature cell types and are a promising source of regenerative medicine. The success of regenerative medicine using MSCs strongly depends on their differentiation potential. In this study, we sought to identify marker genes for predicting the osteogenic differentiation potential by comparing ilium MSC and fibroblast samples. We measured the mRNA levels of 95 candidate genes in nine ilium MSC and four fibroblast samples before osteogenic induction, and compared them with alkaline phosphatase (ALP) activity as a marker of osteogenic differentiation after induction. We identified 17 genes whose mRNA expression levels positively correlated with ALP activity. The chondrogenic and adipogenic differentiation potentials of jaw MSCs are much lower than those of ilium MSCs, although the osteogenic differentiation potential of jaw MSCs is comparable with that of ilium MSCs. To select markers suitable for predicting the osteogenic differentiation potential, we compared the mRNA levels of the 17 genes in ilium MSCs with those in jaw MSCs. The levels of 7 out of the 17 genes were not substantially different between the jaw and ilium MSCs, while the remaining 10 genes were expressed at significantly lower levels in jaw MSCs than in ilium MSCs. The mRNA levels of the seven similarly expressed genes were also compared with those in fibroblasts, which have little or no osteogenic differentiation potential. Among the seven genes, the mRNA levels of IGF1 and SRGN in all MSCs examined were higher than those in any of the fibroblasts. These results suggest that measuring the mRNA levels of IGF1 and SRGN before osteogenic induction will provide useful information for selecting competent MSCs for regenerative medicine, although the effectiveness of the markers is needed to be confirmed using a large number of MSCs, which have various levels of osteogenic differentiation potential.

Minimally invasive treatment of long bone non-unions with bone marrow concentrate, demineralized bone matrix and platelet-rich fibrin in 38 patients

To determine the efficacy of percutaneous injection of autologous bone marrow concentrated (BMC), demineralized bone matrix (DBM), and platelet rich fibrin (PRF) in the treatment of long bone non-unions. From January 2011 to January 2018 patients with non-union of the lower limbs who were on the waiting list for open grafting with established tibial or femoral non-union and minimal deformity were eligible to participate in this study. Patients were treated with a single percutaneous injection of DBM, BMC and PRF. Our study group comprised 38 patients (26 males and 12 females; mean age 39, range 18 to 65). Non-unions were located in the femur (18 cases) and in the tibia (20 cases). Clinical and imaging follow-up ranged from 4 to 60 months (mean 20 months). Bone union occurred in 30 out of 38 patients (79%) in an average of 7 months (range 3 to 12) and all healed patients had full weight bearing after 9 months on average (range 6 to 12) from injection. In 19 cases the osteosynthesis was removed 12 months on average (range 3 to 36) from surgery. One patient developed infection at the non-union site after treatment. Percutaneous injection of DBM, BMC, and PRF is an effective treatment for long-bone non-unions. This technique allows the bone to heal with a minimally invasive approach and with a hospitalization of 2 days. Key elements of bone regeneration consist of a combination of biological and biomechanical therapeutic approach.

Effect of platelet-rich plasma on fracture healing

Bone has the ability to completely regenerate under normal healing conditions. Although fractures generally heal uneventfully, healing problems such as delayed union or nonunion still occur in approximately 10% of patients. Optimal healing potential involves an interplay of biomechanical and biological factors. Orthopedic implants are commonly used for providing the necessary biomechanical support. In situations where the biological factors that are needed for fracture healing are deemed inadequate, additional biological enhancement is needed. With platelets being packed with granules that contain growth factors and other proteins that have osteoinductive capacity, local application of platelet concentrates, also called platelet-rich plasma (PRP) seems an attractive biological to enhance fracture healing. This review shows an overview of the use PRP and its effect in enhancing fracture healing. PRP is extracted from the patient's own blood, supporting that its use is considered safe. Although PRP showed effective in some studies, other studies showed controversial results. Conflicts in the literature may be explained by the absence of consensus about the preparation of PRP, differences in platelet counts, low number of patients, and absence of a standard application technique. More studies addressing these issues are needed in order to determine the true effect of PRP on fracture healing.

Frontiers in non-union research

Multifactorial aetiology defines non-unions, with a biological and a mechanical distortion of the timeline of bone healing.

Research on new advances to increase osteogenesis and promote non-union healing is strongly directed towards new forms of cell products.

Basic science and research on non-union treatments is needed to compile preclinical data on new treatments.

Bone marrow concentration and expanded mesenchymal stromal cells still require extensive clinical research to confirm efficacy in non-union treatment.

Solid preclinical studies, precise cell product definition and preparation, and appropriate ethical and regulatory approvals are needed to assess new advanced therapy medicinal products.

Cite this article: EFORT Open Rev 2020;5:574-583. DOI: 10.1302/2058-5241.5.190062

[Effectiveness of percutaneous injection of autologous concentrated bone marrow aspirate combined with platelet-rich plasma in treatment of delayed fracture healing]

Objective

To analyze the effectiveness of percutaneous injection of autologous concentrated bone marrow aspirate (cBMA) combined with platelet-rich plasma (PRP) in the treatment of delayed fracture healing.

Methods

A prospective, randomized, controlled, single-blind case study was conducted. Between March 2016 and July 2018, 66 patients who met the inclusion and exclusion criteria for delayed fracture healing but had solid internal fixation of the fracture end were randomly divided into control group (31 cases, treated with percutaneous autogenous bone marrow blood injection) and study group (35 cases, treated with percutaneous autogenous cBMA+PRP injection). General data such as gender, age, body mass index, site of delayed fracture healing, length of bone defect at fracture end, and preoperative radiographic union score for tibia (RUST) showed no significant difference between the two groups ( P>0.05). Before injection, Kirschner wire was used in both groups to stimulate the fracture end and cause minor injury. The fracture healing time, treatment cost, and adverse reactions were recorded and compared between the two groups. Visual analogue scale (VAS) score was used to evaluate pain improvement. The tibial RUST score was extended to the tubular bone healing evaluation.

Results

No infection of bone marrow puncture needle eyes occurred in both groups. In the control group, local swelling was obvious in 5 cases and pain was aggravated at 1 day after operation in 11 cases. In the study group, postoperative swelling and pain were not obvious, but 2 cases presented local swelling and pain. All of them relieved after symptomatic treatment. Patients in both groups were followed up, the follow-up time of the control group was 16-36 months (mean, 21.8 months), and the study group lasted 14-33 months (mean, 23.2 months). The amount of bone marrow blood was significantly lower in the study group than in the control group ( t=4.610, P=0.000). The degree of postoperative pain in the study group was less than that in the control group, and the treatment cost was higher than that in the control group. But the differences between the two groups in VAS score at 1 day after operation and treatment cost were not significant ( P>0.05). Fracture healing was achieved in 19 cases (61.3%) in the control group and 30 cases (85.7%) in the study group. The difference in fracture healing rate between the two groups was significant ( χ ²=5.128, P=0.024). Fracture healing time and RUST score at last follow-up were significantly better in the study group than in the control group ( P<0.05). At last follow-up, RUST scores in both groups were significantly improved when compared with those before operation ( P<0.05).

Conclusion

Autogenous cBMA combined with PRP percutaneous injection can provide high concentration of BMSCs and growth factors, and can improve the fracture healing rate and shorten the fracture healing time better than autogenous bone marrow blood injection.

Implementation of Endogenous and Exogenous Mesenchymal Progenitor Cells for Skeletal Tissue Regeneration and Repair

Harnessing adult mesenchymal stem/progenitor cells to stimulate skeletal tissue repair is a strategy that is being actively investigated. While scientists continue to develop creative and thoughtful ways to utilize these cells for tissue repair, the vast majority of these methodologies can ultimately be categorized into two main approaches: (1) Facilitating the recruitment of endogenous host cells to the injury site; and (2) physically administering into the injury site cells themselves, exogenously, either by autologous or allogeneic implantation. The aim of this paper is to comprehensively review recent key literature on the use of these two approaches in stimulating healing and repair of different skeletal tissues. As expected, each of the two strategies have their own advantages and limitations (which we describe), especially when considering the diverse microenvironments of different skeletal tissues like bone, tendon/ligament, and cartilage/fibrocartilage. This paper also discusses stem/progenitor cells commonly used for repairing different skeletal tissues, and it lists ongoing clinical trials that have risen from the implementation of these cells and strategies. Lastly, we discuss our own thoughts on where the field is headed in the near future.

High-Dose TGF-β1 Impairs Mesenchymal Stem Cell-Mediated Bone Regeneration via Bmp2 Inhibition

Transforming growth factor-β1 (TGF-β1) is a key factor in bone reconstruction. However, its pathophysiological role in non-union and bone repair remains unclear. Here we demonstrated that TGF-β1 was highly expressed in both C57BL/6 mice where new bone formation was impaired after autologous bone marrow mesenchymal stem cell (BMMSC) implantation in non-union patients. High doses of TGF-β1 inhibited BMMSC osteogenesis and attenuated bone regeneration in vivo. Furthermore, different TGF-β1 levels exhibited opposite effects on osteogenic differentiation and bone healing. Mechanistically, low TGF-β1 doses activated smad3, promoted their binding to bone morphogenetic protein 2 (Bmp2) promoter, and upregulated Bmp2 expression in BMMSCs. By contrast, Bmp2 transcription was inhibited by changing smad3 binding sites on its promoter at high TGF-β1 levels. In addition, high TGF-β1 doses increased tomoregulin-1 (Tmeff1) levels, resulting in the repression of Bmp2 and bone formation in mice. Treatment with the TGF-β1 inhibitor SB431542 significantly rescued BMMSC osteogenesis and accelerated bone regeneration. Our study suggests that high-dose TGF-β1 dampens BMMSC-mediated bone regeneration by activating canonical TGF-β/smad3 signaling and inhibiting Bmp2 via direct and indirect mechanisms. These data collectively show a previously unrecognized mechanism of TGF-β1 in bone repair, and TGF-β1 is an effective therapeutic target for treating bone regeneration disability. © 2019 American Society for Bone and Mineral Research.

Bone Marrow-Derived Cell Therapies to Heal Long-Bone Nonunions: A Systematic Review and Meta-Analysis-Which Is the Best Available Treatment?

Nonunions represent one of the major indications for clinical settings with stem cell-based therapies. The objective of this research was to systematically assess the current evidence for the efficacy of bone marrow-derived cell-based approaches associated or not with bone scaffolds for the treatment of nonunions. We searched MEDLINE (PubMed) and CENTRAL up to July 2019 for clinical studies focused on the use of cell-based therapies and bone marrow derivatives to treat bone nonunions. Three investigators independently extracted the data and appraised the risk of bias. We analysed 27 studies including a total number of 347 participants exposed to four interventions: bone marrow concentrate (BMAC), BMAC combined with scaffold (BMAC/Scaffold), bone marrow-derived mesenchymal stromal cells (BMSCs), and BMSC combined with scaffold (BMSC/Scaffold). Two controlled studies showed a positive trend in bone healing in favour of BMAC/Scaffold or BMSC/Scaffold treatment against bone autograft, although the difference was not statistically significant (RR 0.11, 95% CI -0.05; 0.28). Among single cohort studies, the highest mean pooled proportion of healing rate was reported for BMAC (77%; 95% CI 63%-89%; 107 cases, n = 8) and BMAC/Scaffold treatments with (71%; 95% CI 50%-89%; 117 cases, n = 8) at 6 months of follow-up. At 12 months of follow-up, an increasing proportion of bone healing was observed in all the treatment groups, ranging from 81% to 100%. These results indicate that BMAC or BMAC/Scaffold might be considered as the primary choice to treat nonunions with a successful healing rate at a midterm follow-up. Moreover, this meta-analysis highlighted that the presence of a scaffold positively influences the healing rate at a long-term follow-up. More case-control studies are still needed to support the clinical improvement of cell-based therapies against autografts, up to now considered as the gold standard for the treatment of nonunions.

Multidirectional percutaneous drilling and autologous bone marrow injection for the treatment of femoral diaphyseal nonunions: a prospective interventional study

Background

To examine the outcomes of multidirectional percutaneous drilling and autologous concentrated bone marrow (BM) transplantation for atrophic femoral diaphyseal nonunion characterized by intact hardware and mechanical stability at the nonunion site.

Methods

Fourteen patients (22–63 years of age) were admitted to our hospital with atrophic femoral diaphyseal nonunion. All patients were treated with a combination of multidirectional percutaneous drilling and autologous concentrated BM transplantation. Radiographic evaluation was conducted every month after transplantation until bone healing was achieved.

Results

Bony union was achieved in 13 of the 14 patients (92.9%) after an average of 3.9 months (range: 2.5–6 months). The average radiographic union scale in tibial (RUST) scale score improved significantly from the preoperative period (6.15±1.21) to follow-up (11.23±0.73; P<0.05). The mean follow-up after transplantation was 31.4±9.5 months (range: 18–50 months). At the final follow-up, the quality of function had improved significantly, allowing a return to normal activities.

Conclusion

Combined multidirectional percutaneous drilling and autologous concentrated BM transplantation is an easy, safe, inexpensive, and efficacious method to treat atrophic femoral diaphyseal nonunion characterized by intact hardware and mechanical stability at the nonunion site.

Trial registration number: ISRCTN29808592

Immunomodulatory Effects of MSCs in Bone Healing

Mesenchymal stem cells (MSCs) are capable of differentiating into multilineage cells, thus making them a significant prospect as a cell source for regenerative therapy; however, the differentiation capacity of MSCs into osteoblasts seems to not be the main mechanism responsible for the benefits associated with human mesenchymal stem cells hMSCs when used in cell therapy approaches. The process of bone fracture restoration starts with an instant inflammatory reaction, as the innate immune system responds with cytokines that enhance and activate many cell types, including MSCs, at the site of the injury. In this review, we address the influence of MSCs on the immune system in fracture repair and osteogenesis. This paradigm offers a means of distinguishing target bone diseases to be treated with MSC therapy to enhance bone repair by targeting the crosstalk between MSCs and the immune system.

Ex vivo gene therapy using human bone marrow cells overexpressing BMP-2: "Next-day" gene therapy versus standard "two-step" approach

Traditionally, ex vivo gene therapy involves a two-step approach, with culture expansion of cells prior to transduction and implantation. We have tried to simplify this strategy and eliminate the time and cost associated with culture expansion, by introducing "next-day" regional gene therapy using human bone marrow cells. The purpose of this study was to determine whether a lentiviral vector (LV) carrying the cDNA for BMP-2 can transduce freshly isolated human BM cells, leading to abundant BMP production and bone formation in vivo, and evaluate the in vivo osteoinductive potential of "next-day" gene therapy and the standard "two-step" tissue culture expansion approach. To this end, human bone marrow cells (HBMC) from patients undergoing total hip arthroplasty were harvested, transduced with a BMP-2-expressing LV either overnight ("next day" gene therapy; ND) or after culture expansion (cultured "two-step" approach; C) and then implanted into a rat critical-sized femoral defect. The animals were randomly assigned to one of the following groups: I; ND-HBMC transduced with LV-TSTA BMP-2, II; ND-HBMC transduced with LV-TSTA GFP, III; non-transduced ND-HBMC; IV; C-HBMC transduced with LV-TSTA BMP-2, V; C-HBMC transduced with LV-TSTA-GFP, VI; non-transduced C-HBMC. Treatment with either "next-day" or cultured HBMC demonstrated a significant increase in new bone formation compared with all negative control groups as seen in plain radiographs, microCT and histologic/histomorphometric analysis. At 12 weeks post-op, complete defect union on plain X-rays occurred in 7/14 animals in the ND-HBMC/BMP-2 group and 12/14 in the C-HBMC/BMP-2 treated rats. The two-step approach was associated with more consistent results, a higher union rate, and superiority with regards to all of the studied bone healing parameters. In this study we demonstrate proof of concept that BMP-2-transduced human bone marrow cells can be used to enhance bone healing in segmental bone defects, and that regional gene therapy using lentiviral transduction has the osteoinductive potential to heal large bone defects in clinical settings.

Effect of Autogenous Bone Marrow Aspirate Treatment on Magnetic Resonance Imaging Integration of Osteochondral Allografts in the Knee: A Matched Comparative Imaging Analysis

PURPOSE

To accurately evaluate the effects of bone marrow aspirate (BMA) augmentation on osteochondral allograft (OCA) integration on early postoperative magnetic resonance imaging (MRI) using the comprehensive Osteochondral Allograft MRI Scoring System (OCAMRISS).

METHODS

This imaging study compared patients who underwent OCA transplantation with and without BMA augmentation for the treatment of focal osteochondral defects in the knee performed by a single surgeon between July 2013 and July 2017. Patients were excluded if they underwent implantation of premade plugs, had an overlapping OCA configuration ("snowman" technique), or did not undergo MRI at 6 months postoperatively. Patients were matched by lesion location, lesion size, age, and body mass index, as well as whether they underwent previous surgical procedures. Data were analyzed using descriptive statistics, Spearman correlation, the independent t test, the Mann-Whitney U test, and the χ² test.

RESULTS

A total of 58 patients (29 per group) were included in this study, with an average age of 36.4 ± 10.1 years and mean body mass index of 28.6 ± 5.1. The mean size of the analyzed OCA plugs was 3.3 ± 1 cm². At an average imaging follow-up of 5.6 ± 1 months, 86.2% of the grafts had achieved osseous integration at the graft-host junction and 75.9% did not show any cystic changes in the subchondral bone. No difference in any OCAMRISS subscale was seen comparing OCAs with and without BMA augmentation (P > .05). Specifically, osseous integration and subchondral cyst formation were comparable between groups (P = .128 and P = .539, respectively).

CONCLUSIONS

OCAs showed excellent osseous integration at the graft-host junction on 6-month postoperative MRI. The treatment of OCAs with autogenous BMA did not result in superior imaging outcomes when analyzed using the OCAMRISS.

LEVEL OF EVIDENCE

Level III, case-control study.

Cell-Based Therapies for the Treatment of Fractures

Ongoing studies investigating fracture healing have uncovered and allowed investigators to gain a better understanding of where the variety of cells, which participate in this process, originate, and how they communicate as well as how they can be enhanced to successfully heal a fracture when the process has slowed or failed completely. This brief review will highlight some of the recent findings regarding the role the immune system in fracture healing and how these cells communicate with each other during the healing process. In addition, two 2 methods that have recently been shown to be promising techniques in supporting fracture when it stalls or reversing the process, when the fracture has failed to heal, will also be described.

A parameterised mathematical model to elucidate osteoblast cell growth in a phosphate-glass microcarrier culture

Tissue engineering has the potential to augment bone grafting. Employing microcarriers as cell-expansion vehicles is a promising bottom-up bone tissue engineering strategy. Here we propose a collaborative approach between experimental work and mathematical modelling to develop protocols for growing microcarrier-based engineered constructs of clinically relevant size. Experiments in 96-well plates characterise cell growth with the model human cell line MG-63 using four phosphate glass microcarrier materials. Three of the materials are doped with 5 mol% TiO₂ and contain 0%, 2% or 5% CoO, and the fourth material is doped only with 7% TiO₂ (0% CoO). A mathematical model of cell growth is parameterised by finding material-specific growth coefficients through data-fitting against these experiments. The parameterised mathematical model offers more insight into the material performance by comparing culture outcome against clinically relevant criteria: maximising final cell number starting with the lowest cell number in the shortest time frame. Based on this analysis, material 7% TiO₂ is identified as the most promising.

Mesenchymal Stem Cell Therapy for Bone Regeneration

Mesenchymal stem cells (MSCs) have been used in clinic for approximately 20 years. During this period, various new populations of MSCs have been found or manipulated. However, their characters and relative strength for bone regeneration have not been well known. For a comprehensive understanding of MSCs, we reviewed the literature on the multipotent cells ranging from the definition to the current research progress for bone regeneration. Based on our literature review, bone marrow MSCs have been most widely studied and utilized in clinical settings. Among other populations of MSCs, adipose-derived MSCs and perivascular MSCs might be potential candidates for bone regeneration, whose efficacy and safety still require further investigation.

Gene Therapy for Bone Repair Using Human Cells: Superior Osteogenic Potential of Bone Morphogenetic Protein 2-Transduced Mesenchymal Stem Cells Derived from Adipose Tissue Compared to Bone Marrow

Ex vivo regional gene therapy strategies using animal mesenchymal stem cells genetically modified to overexpress osteoinductive growth factors have been successfully used in a variety of animal models to induce both heterotopic and orthotopic bone formation. However, in order to adapt regional gene therapy for clinical applications, it is essential to assess the osteogenic capacity of transduced human cells and choose the cell type that demonstrates the best clinical potential. Bone-marrow stem cells (BMSC) and adipose-derived stem cells (ASC) were selected in this study for in vitro evaluation, before and after transduction with a lentiviral two-step transcriptional amplification system (TSTA) overexpressing bone morphogenetic protein 2 (BMP-2; LV-TSTA-BMP-2) or green fluorescent protein (GFP; LV-TSTA-GFP). Cell growth, transduction efficiency, BMP-2 production, and osteogenic capacity were assessed. The study demonstrated that BMSC were characterized by a slower cell growth compared to ASC. Fluorescence-activated cell sorting analysis of GFP-transduced cells confirmed successful transduction with the vector and revealed an overall higher but not statistically significant transduction efficiency in ASC versus BMSC (90.2 ± 4.06% vs. 80.4 ± 8.51%, respectively; p = 0.146). Enzyme-linked immunosorbent assay confirmed abundant BMP-2 production by both cell types transduced with LV-TSTA-BMP-2, with BMP-2 production being significantly higher in ASC versus BMSC (239.5 ± 116.55 ng vs. 70.86 ± 24.7 ng; p = 0.001). Quantitative analysis of extracellular deposition of calcium (Alizarin red) and alkaline phosphatase activity showed that BMP-2-transduced cells had a higher osteogenic differentiation capacity compared to non-transduced cells. When comparing the two cell types, ASC/LV-TSTA-BMP-2 demonstrated a significantly higher mineralization potential compared to BMSC/LV-TSTA-BMP-2 7 days post transduction (p = 0.014). In conclusion, this study demonstrates that transduction with LV-TSTA-BMP-2 can significantly enhance the osteogenic potential of both human BMSC and ASC. BMP-2-treated ASC exhibited higher BMP-2 production and greater osteogenic differentiation capacity compared to BMP-2-treated BMSC. These results, along with the fact that liposuction is an easy procedure with lower donor-site morbidity compared to BM aspiration, indicate that adipose tissue might be a preferable source of MSCs to develop a regional gene therapy approach to treat difficult bone-repair scenarios.

A Resorbable Biomaterial Shaped as a Tubular Chamber and Containing Stem Cells: A Pilot Study on Artificial Bone Regeneration

In a previous study, we showed how healing of non-union defects in rabbit radii can be achieved by means of a tubular resorbable chamber, in comparison with untreated defects. In the present study, we placed bone marrow stem cells inside the chamber. Bone marrow was obtained by percutaneous aspiration from the iliac crest in 9 adult New Zealand rabbits. Stem cells were separated by the centrifugation technique. In the same animals, a defect of 10 mm was created in both radii. On the left side, the defect was treated with the poly-DL-Lactide chamber, in which a suspension of autologous cells was injected; on the right side, only autologous cells were used. Radiological and histomorphometric data were compared within this study as well as with the results of our previous study. At 3, 6 and 9 months, there was no healing on the right side. On the left side, progressive bone formation with reunion of the stumps was observed in the chamber. We conclude that stem cells can accelerate bone healing when contained in the tubular chamber.

Does Age Influence the Efficacy of Demineralized Bone Matrix Enriched with Concentrated Bone Marrow Aspirate in Lumbar Fusions?

STUDY DESIGN

Retrospective study.

OBJECTIVE

Evaluate the effect of age on the efficacy of allograft/demineralized bone matrix (DBM) enriched with concentrated bone marrow aspirate (BMA) in posterolateral lumbar fusions (PLFs).

SUMMARY OF BACKGROUND DATA

Cell-based therapies such as concentrated BMA have been developed as a potential alternative to iliac crest bone graft (ICBG). BMA contains mesenchymal stem cells (MSCs) and growth factors that can confer osteogenic and osteoinductive potential to osteoconductive scaffolds such as DBM/allograft. To date, no studies have examined the role of age on fusion outcomes when BMA is utilized despite the well-established deleterious effects of advanced age on bone marrow and MSC potential.

MATERIALS AND METHODS

Fifty-one patients that underwent PLF were divided into 3 groups. Group A (n=14) composed of patients age 65 years and older who received BMA with DBM. Group B (n=17) consisted of patients younger than 65 years of age who received BMA with DBM. Group C (n=20) composed of patients age 65 years and older who received ICBG. Fusion rates and clinical outcomes were assessed.

RESULTS

Fusion was significantly lower in group A (35.7%) compared with both groups B (76.4%) and C (80%) (A vs. B, P=0.03; A vs. C, P=0.01). There were no differences in clinical outcomes among all groups except for pseudarthrosis which occurred in 28.6% of patients in group A compared with none and 5% of patients in groups B and C, respectively (A vs. B, P=0.03; A vs. C, P=0.13).

CONCLUSIONS

Elderly patients undergoing PLF using DBM enriched with BMA achieved lower radiographic fusion success compared with their nonelderly counterparts and compared with elderly patients that had fusion with ICBG. This may be partly due to the effect of advanced age on MSC potential.

[Therapeutic utilization of stem cells in orthopedics]

Stem cells are becoming increasingly more important in the field of regenerative medicine. Adult mesenchymal stem cells (MSCs) are harvested predominantly from bone marrow or adipose tissue, are already being used in the clinical setting and have a low potential for side effects. In orthopedics, experience has been gained in the treatment of bone defects, non-unions, cartilage defects, osteoarthritis and tendon pathologies. The current data are derived from case studies and randomized controlled trials are missing; therefore, there are many open questions concerning the optimal cell source, number of cells, administration technique (e.g. injections and matrices) or combinations with growth factors; however, it is evident from the data that MSCs have a positive effect on tissue regeneration and are safe to use.

A systematic review of the clinical applications and complications of bone marrow aspirate concentrate in management of bone defects and nonunions

PURPOSE

Fracture healing encompasses a succession of dynamic multifactorial metabolic events, which ultimately re-establishes the integrity of the biomechanical properties of the bone. Up to 10% of the fractures occurring annually will need additional surgical procedures because of impaired healing. The aim of this article is to review the current literature regarding the use of bone marrow aspirate concentrate (BMAC) and its effectiveness in the management of bone defects.

METHODS

We have included all published clinical literature investigating the development, techniques and applications of BMAC. Language, design and risk of bias did not deter the initial inclusion of any study. Our search was exclusively limited to studies involving human subjects. A PRISMA compliant search was carried out as published in 2009. This included the online databases: PubMed, EMBASE, clinical trial.gov and the Cochrane library from 1960 to the end of May 2015. MeSH terms used included: "Bone" AND "Marrow" AND "Aspirate" AND "Concentrate" AND "Bone Defects" AND "NONUNION". Eligible studies were independently appraised by two authors using the Critical Appraisal Skills Program checklist. For the purpose of narrative review, relevant studies were included irrespective of methodology or level of evidence.

RESULTS

Thirty-four of the 103 (48 PubMed and 55 EMBASE) results yielded by the preliminary search were included. Exclusions included three duplicate records, six letters, 17 non-orthopaedics related studies and four records irrelevant to our search topic. The CASP appraisal confirmed a satisfactory standard of 31 studies. They all had clearly defined objectives, were well designed and conducted appropriately to meet them. The published studies reported the use of BMAC in non-union and fracture healing (15 studies), bone defects (nine studies), spine fusion (two studies), distraction osteogensis (two studies) and complications related to the use of BMAC (seven studies).

CONCLUSIONS

Stem cells found in BMAC have the potential to self-renew, undertake clonal expansion and differentiate into different musculoskeletal tissues. The commercial processing of BMAC needs to be optimized in order to achieve a consistent end product, which will provide predicable and translatable results. The future potential of cell characterization in order to determine the optimum cell for repair/regeneration of bone also needs to be explored.

LEVEL OF EVIDENCE

Systematic Review of minimum level IV studies.

Role of Bone Marrow Aspirate in Orthopedic Trauma

Bone marrow aspirate grafting entails mesenchymal stem cell-containing bone marrow harvesting and injection into a fracture site to promote bone formation. Although the use of bone marrow aspirate in orthopedic trauma is not widespread, an increasing number of studies are reporting clinical success. Advantages of using bone marrow aspirate are that it is readily obtainable, has low harvest morbidity, and can be easily and quickly injected. However, no universally accepted role for its use exists. Future studies directly comparing bone marrow aspirate with conventional techniques are needed to define its role in the treatment of orthopedic trauma patients.

Bone regeneration strategies with bone marrow stromal cells in orthopaedic surgery

Bone is the most transplanted tissue human with 1 million procedures every year in Europe. Surgical interventions for bone repair are required for varied reasons such as trauma resulting non-union fractures, or diseases including osteoporosis or osteonecrosis. Autologous bone grafting is the gold standard in bone regeneration but it requires a second surgery with associated pain and complications, and is also limited by harvested bone quantity. Synthetic bone substitutes lack the osteoinductive properties to heal large bone defects. Cell therapies based on bone marrow or ex vivo expanded mesenchymal stromal stem cells (MSCs) in association with synthetic calcium phosphate (CaP) bone substitutes may be alternatives to autologous bone grafting. This manuscript reviews the different conventional biological and synthetic bone grafting procedures as well as the more recently introduced cell therapy approaches used in orthopaedic surgery for bone regeneration. Some clinical studies have demonstrated safety and efficacy of these approaches but regeneration of large bone defects remain challenging due to the absence of rapid and adequate vascularisation. Future directions in the field of bone regeneration are presented, such as testing alternative cell sources or in situ fabrication of vascularized bone grafts in patients.

In Vitro Effects of Strontium on Proliferation and Osteoinduction of Human Preadipocytes

Development of tools to be used for in vivo bone tissue regeneration focuses on cellular models and differentiation processes. In searching for all the optimal sources, adipose tissue-derived mesenchymal stem cells (hADSCs or preadipocytes) are able to differentiate into osteoblasts with analogous characteristics to bone marrow mesenchymal stem cells, producing alkaline phosphatase (ALP), collagen, osteocalcin, and calcified nodules, mainly composed of hydroxyapatite (HA). The possibility to influence bone differentiation of stem cells encompasses local and systemic methods, including the use of drugs administered systemically. Among the latter, strontium ranelate (SR) represents an interesting compound, acting as an uncoupling factor that stimulates bone formation and inhibits bone resorption. The aim of our study was to evaluate the in vitro effects of a wide range of strontium (Sr(2+)) concentrations on proliferation, ALP activity, and mineralization of a novel finite clonal hADSCs cell line, named PA20-h5. Sr(2+) promoted PA20-h5 cell proliferation while inducing the increase of ALP activity and gene expression as well as HA production during in vitro osteoinduction. These findings indicate a role for Sr(2+) in supporting bone regeneration during the process of skeletal repair in general, and, more specifically, when cell therapies are applied.

Three-dimensional culture and characterization of mononuclear cells from human bone marrow

BACKGROUND AIMS

The diverse phenotypic changes and clinical and economic disadvantages associated with the monolayer expansion of bone marrow-derived mesenchymal stromal cells (MSCs) have focused attention on the development of one-step intraoperative cells therapies and homing strategies. The mononuclear cell fraction of bone marrow, inclusive of discrete stem cell populations, is not well characterized, and we currently lack suitable cell culture systems in which to culture and investigate the behavior of these cells.

METHODS

Human bone marrow-derived mononuclear cells were cultured within fibrin for 2 weeks with or without fibroblast growth factor-2 supplementation. DNA content and cell viability of enzymatically retrieved cells were determined at days 7 and 14. Cell surface marker profiling and cell cycle analysis were performed by means of multi-color flow cytometry and a 5-ethynyl-2'-deoxyuridine incorporation assay, respectively.

RESULTS

Total mononuclear cell fractions, isolated from whole human bone marrow, was successfully cultured in fibrin gels for up to 14 days under static conditions. Discrete niche cell populations including MSCs, pericytes and hematopoietic stem cells were maintained in relative quiescence for 7 days in proportions similar to that in freshly isolated cells. Colony-forming unit efficiency of enzymatically retrieved MSCs was significantly higher at day 14 compared to day 0; and in accordance with previously published works, it was fibroblast growth factor-2-dependant.

CONCLUSIONS

Fibrin gels provide a simple, novel system in which to culture and study the complete fraction of bone marrow-derived mononuclear cells and may support the development of improved bone marrow cell-based therapies.

The convergence of fracture repair and stem cells: interplay of genes, aging, environmental factors and disease

The complexity of fracture repair makes it an ideal process for studying the interplay between the molecular, cellular, tissue, and organ level events involved in tissue regeneration. Additionally, as fracture repair recapitulates many of the processes that occur during embryonic development, investigations of fracture repair provide insights regarding skeletal embryogenesis. Specifically, inflammation, signaling, gene expression, cellular proliferation and differentiation, osteogenesis, chondrogenesis, angiogenesis, and remodeling represent the complex array of interdependent biological events that occur during fracture repair. Here we review studies of bone regeneration in genetically modified mouse models, during aging, following environmental exposure, and in the setting of disease that provide insights regarding the role of multipotent cells and their regulation during fracture repair. Complementary animal models and ongoing scientific discoveries define an increasing number of molecular and cellular targets to reduce the morbidity and complications associated with fracture repair. Last, some new and exciting areas of stem cell research such as the contribution of mitochondria function, limb regeneration signaling, and microRNA (miRNA) posttranscriptional regulation are all likely to further contribute to our understanding of fracture repair as an active branch of regenerative medicine.

The effect of autologous concentrated bone-marrow grafting on the healing of femoral shaft non-unions after locked intramedullary nailing

The aim of this study was to assess the union rates in a series of patients with failed femoral shaft aseptic non-union who were treated with percutaneous concentrated autologous bone marrow grafting. Bone marrow harvesting and cell injection were performed under general anaesthesia in a single surgical procedure. Radiographic union was diagnosed in fractures with a score ≥ 10 according to the radiographic union scale in tibial fractures (RUST) and confirmed by clinical examination. Eight out of 16 patients progressed to consolidation (RUST score ≥ 10). Radiographic evidence of fracture union was observed at an average of 4.75 ± 1.75 months (range 3 to 8 months). All eight patients who did not progress to union within 12 months following the cell grafting procedure had a RUST score ≤ 10 (range 4 to 9). There were no differences in age, number of previous surgeries, duration of nonunion and preoperative RUST score between the patients that developed solid union and those with failed consolidation. However, a relationship between the number of osteoprogenitors injected and the rate of union was noted, 20.2 ± 8.6 × 10(8) versus 9.8 ± 4.3 × 10(8), p<0.005, between the patients with and without union, respectively. The efficacy of percutaneous autologous concentrated bone marrow grafting seems to be related to the number of osteoprogenitors available in the aspirates. Optimisation of the aspiration technique and concentration process is of paramount importance to increase the incidence of a successful outcome.

Percutaneous grafting with bone marrow autologous concentrate for open tibia fractures: analysis of forty three cases and literature review

PURPOSE

Tibial fractures are the most common lower limb fractures. Some criteria such as open fractures and increasing open stage are known to be associated with high delayed union and pseudarthrosis rate. In cases of delayed or nonunion, classical treatment is autologous cancelous bone graft which is associated with high morbidity rate. The ideal treatment would be a percutaneous harvesting and grafting technique. As bone marrow autologous concentrate (BMAC) presents both advantages, we evaluated this technique from 2002 to 2007.

METHODS

This was a retrospective study of 43 cases of open tibial fractures with initial surgical treatment. The criteria of inclusion were open fracture and nonunion, delayed union or suspicion of delayed union.

RESULTS

In 23 cases (53.5 %) BMAC was successful. The success group had received significantly more CFU-F than the failure group (469 vs 153.10(3), p = 0.013). A threshold of 360.10(3) CFU-F grafted could be established over which there was 100 % success. BMAC done before 110 days after fracture had 47 % success and BMAC done since 110 days after fracture had 73 % success. BMAC success rate decreased with increasing initial fracture skin open stage. There was no BMAC success in cases of a fracture with a remaining gap of more than 4 mm. We had no complications with the technique at the iliac harvesting zone and tibia injection point.

CONCLUSION

BMAC is a technique that should be considered as one of the different alternatives for management of long-bone delayed and nonunion because of its effectiveness, low complication rate, preservation of bone stock and low cost.

Cell therapy for bone repair

When natural bone repair mechanisms fail, autologous bone grafting is the current standard of care. The osteogenic cells and bone matrix in the graft provide the osteo-inductive and osteo-conductive properties required for successful bone repair. Bone marrow (BM) mesenchymal stem cells (MSCs) can differentiate into osteogenic cells. MSC-based cell therapy holds promise for promoting bone repair. The amount of MSCs available from iliac-crest aspirates is too small to be clinically useful, and either concentration or culture must therefore be used to expand the MSC population. MSCs can be administered alone via percutaneous injection or implanted during open surgery with a biomaterial, usually biphasic hydroxyapatite/β-calcium-triphosphate granules. Encouraging preliminary results have been obtained in patients with delayed healing of long bone fractures or avascular necrosis of the femoral head. Bone tissue engineering involves in vitro MSC culturing on biomaterials to obtain colonisation of the biomaterial and differentiation of the cells. The biomaterial-cell construct is then implanted into the zone to be treated. Few published data are available on bone tissue engineering. Much work remains to be done before determining whether this method is suitable for the routine filling of bone tissue defects. Increasing cell survival and promoting implant vascularisation are major challenges. Improved expertise with culturing techniques, together with the incorporation of regulatory requirements, will open the way to high-quality clinical trials investigating the usefulness of cell therapy as a method for achieving bone repair. Cell therapy avoids the drawbacks of autologous bone grafting, preserving the bone stock and diminishing treatment invasiveness.

Cell therapy of pseudarthrosis

Objective

To assess the safety and efficiency of cell therapy for pseudarthrosis. Implant of the bone marrow aspirate was compared to mononuclear cells purified extemporaneously using the Sepax^® equipment.

Methods

Six patients with nonunion of the tibia or femur were treated. Four received a percutaneous infusion of autologous bone marrow aspirated from the iliac crest, and two received autologous bone marrow mononuclear cells separated from the aspirate with the Sepax^®. The primary fixation method was unchanged, and the nonunion focus was not exposed. Physical examination and radiographies were performed 2, 4 and 6 months after the treatment by the same physician. After consolidation of the fracture the satisfaction of the patients was estimated using the adapted QALY scale.

Results

No complications occurred as a result of the referred procedures. Bone consolidation was obtained in all cases within 3 to 24 weeks. The degree of patient satisfaction before and after bone consolidation was assessed, with the average value increasing from two to nine (p=0.0156).

Conclusion

We conclude that the proposed method is effective and safe for the treatment of nonunion of long bones regardless of the stabilization method used. Level of Evidence II, Prospective Comparative Study

Cell therapy of pseudarthrosis

OBJECTIVE

To assess the safety and efficiency of cell therapy for pseudarthrosis. Implant of the bone marrow aspirate was compared to mononuclear cells purified extemporaneously using the Sepax(®) equipment.

METHODS

Six patients with nonunion of the tibia or femur were treated. Four received a percutaneous infusion of autologous bone marrow aspirated from the iliac crest, and two received autologous bone marrow mononuclear cells separated from the aspirate with the Sepax(®). The primary fixation method was unchanged, and the nonunion focus was not exposed. Physical examination and radiographies were performed 2, 4 and 6 months after the treatment by the same physician. After consolidation of the fracture the satisfaction of the patients was estimated using the adapted QALY scale.

RESULTS

No complications occurred as a result of the referred procedures. Bone consolidation was obtained in all cases within 3 to 24 weeks. The degree of patient satisfaction before and after bone consolidation was assessed, with the average value increasing from two to nine (p=0.0156).

CONCLUSION

We conclude that the proposed method is effective and safe for the treatment of nonunion of long bones regardless of the stabilization method used. Level of Evidence II, Prospective Comparative Study.

Local transplantation of granulocyte colony stimulating factor-mobilized CD34+ cells for patients with femoral and tibial nonunion: pilot clinical trial

Most bone fractures typically heal, although a significant proportion (5%-10%) of fractures fail to heal, resulting in delayed union or persistent nonunion. Some preclinical evidence shows the therapeutic potential of peripheral blood CD34(+) cells, a hematopoietic/endothelial progenitor cell-enriched population, for bone fracture healing; however, clinical outcome following transplantation of CD34(+) cells in patients with fracture has never been reported. We report a phase I/IIa clinical trial regarding transplantation of autologous, granulocyte colony stimulating factor-mobilized CD34(+) cells with atelocollagen scaffold for patients with femoral or tibial fracture nonunion (n = 7). The primary endpoint of this study is radiological fracture healing (union) by evaluating anteroposterior and lateral views at week 12 following cell therapy. For the safety evaluation, incidence, severity, and outcome of all adverse events were recorded. Radiological fracture healing at week 12 was achieved in five of seven cases (71.4%), which was greater than the threshold (18.1%) predefined by the historical outcome of the standard of care. The interval between cell transplantation and union, the secondary endpoint, was 12.6 ± 5.4 weeks (range, 8-24 weeks) for clinical healing and 16.1 ± 10.2 weeks (range, 8-36 weeks) for radiological healing. Neither deaths nor life-threatening adverse events were observed during the 1-year follow-up after the cell therapy. These results suggest feasibility, safety, and potential effectiveness of CD34(+) cell therapy in patients with nonunion.

Percutaneous autologous concentrated bone marrow grafting in the treatment for nonunion

The purpose of this study was to evaluate the clinical and radiographic treatment effects of percutaneous autologous concentrated bone marrow grafting in nonunion cases and to evaluate the effectiveness of this grafting procedure. We enrolled 17 cases those had atrophic changes due to continuous nonunion for over 9 months after injury and had undergone low-intensity pulsed ultrasound treatment for more than 3 months. The site of nonunion was the femur in 10 cases, the tibia in 5 cases, the humerus in 1 case, and the ulna in 1 case. They underwent percutaneous autologous concentrated bone marrow grafting and continued low-intensity pulsed ultrasound stimulation treatment after grafting. Patients were evaluated using the visual analogue scale for pain at immediately before the procedure, 3, 6, and 12 months after grafting. Plain radiographs of the affected site were taken and evaluated about the healing of the nonunion site at each clinical evaluation. As quantitative assessment, CT scans were undertaken before the procedure and 6 months after grafting. The visual analogue scale pain score was reduced consistently after grafting in all patients. About the healing at the nonunion site, 11 and 13 cases of bone union were observed at 6 and 12 months after grafting. The mean volume of callus formation based on CT images was 4,147 (262-27,392) mm3 total between grafting and 6 months. Percutaneous autologous concentrated bone marrow grafting is an effective procedure for the treatment of patients with nonunion.

Percutaneous autologous bone marrow injection in the treatment of distal meta-diaphyseal tibial nonunions and delayed unions

OBJECTIVE

To report the outcomes of percutaneous autologous bone marrow injection for nonunion or delayed union of the distal tibial metaphysis in patients with prior plating.

DESIGN

Consecutive case series.

SETTING

Tertiary center.

PATIENTS

Eleven consecutive patients (aged 24-51 years) were referred to us with a nonunion or delayed union of the distal tibial metaphysis after open reduction and internal fixation (plates and screws) at the time of fracture. The average time from initial injury to nonunion or delayed union and bone marrow treatment was 8 months (range, 3-20 months).

INTERVENTION

A total of 40-80 mL of bone marrow aspirated from the posterior iliac crest and injected in and around the nonunion or delayed union site under fluoroscopic guidance.

MEASUREMENTS

Healing at the injury site was evaluated using clinical and radiographic criteria, including computed tomography. Measures included American Academy of Orthopaedic Surgeons Lower Limb Core Scale (LLCS), Brief Pain Inventory, and Short Form 12 Physical Component Summary.

RESULTS

Nine of the 11 patients attained bony union within 6 months of bone marrow injection. Six of these 9 patients who were followed-up an average of 4.4 years (range, 1.3-8.2 years) after the injection reported significant (P < 0.05) improvements in Lower Limb Core Scale (59.9-89.7), pain intensity (2.9-1.7), pain interference (4.6-2.3), and Short Form 12 Physical Component Summary (29.5-46.6) and 5.6 years improvement in quality-adjusted life years.

CONCLUSIONS

Percutaneous autologous bone marrow injection is a minimally invasive, safe, and inexpensive treatment option for distal metaphyseal tibial nonunions or delayed unions after internal fixation and should be considered when the retained hardware seems to be intact and stable.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Percutaneous autologous bone marrow injections for delayed or non-union of bones

PURPOSE

To evaluate 12 patients with delayed or nonunion of bones treated with bone marrow injections.

METHODS

6 men and 6 women aged 15 to 70 (mean, 45) years underwent bone marrow injections for delayed union (n=2) or atrophic non-union (n=10) of the ulna (n=6), femur (n=3), humerus (n=2), or metacarpal (n=1). Bone marrow was aspirated from the anterior iliac crest and injected to the delayed and non-union sites. Two injections were given for children and adolescents, and 3 for adults. The interval between the injections was 6 to 8 weeks. The amount of bone marrow injected was 30 to 40 ml for long bones and 20 ml for metacarpals.

RESULTS

Ten of the 12 delayed or non-union of bones healed after bone marrow injections. The mean time for callus formation was 5.8 (range, 3-10) weeks, for clinical union was 7 (range, 4-12) weeks, and for radiological union was 16 (range, 10-24) weeks.

CONCLUSION

Multiple injections of low-volume bone marrow can be used for treatment of delayed or non-union of bones.

Cellular therapies for the treatment of non-union: the past, present and future

Non-union fracture is a pathological condition having some impairment of the cellular part of the repair: a reduction of MSC and of the osteoblastic activation. Non union is therefore a good indication for cell-based therapies using stem cells. We described the rational of this treatment and described the technique of autologous bone marrow concentrate implantation that was until now used. With the development of stem cell research and regenerative medicine, we believed that therapy based on cytotherapy has great potential. In this review, clinical applications of cytotherapy are summarized and analyzed. Current problems and future challenges are discussed.

Biologic adjuvants for fracture healing

Bone tissue has an exceptional quality to regenerate to native tissue in response to injury. However, the fracture repair process requires mechanical stability or a viable biological microenvironment or both to ensure successful healing to native tissue. An improved understanding of the molecular and cellular events that occur during bone repair and remodeling has led to the development of biologic agents that can augment the biological microenvironment and enhance bone repair. Orthobiologics, including stem cells, osteoinductive growth factors, osteoconductive matrices, and anabolic agents, are available clinically for accelerating fracture repair and treatment of compromised bone repair situations like delayed unions and nonunions. Preclinical and clinical studies using biologic agents like recombinant bone morphogenetic proteins have demonstrated an efficacy similar or better than that of autologous bone graft in acute fracture healing. A lack of standardized outcome measures for comparison of biologic agents in clinical fracture repair trials, frequent off-label use, and a limited understanding of the biological activity of these agents at the bone repair site have limited their efficacy in clinical applications.

Intraoperative stem cell therapy

Stem cells hold significant promise for regeneration of tissue defects and disease-modifying therapies. Although numerous promising stem cell approaches are advancing in clinical trials, intraoperative stem cell therapies offer more immediate hope by integrating an autologous cell source with a well-established surgical intervention in a single procedure. Herein, the major developments in intraoperative stem cell approaches, from in vivo models to clinical studies, are reviewed, and the potential regenerative mechanisms and the roles of different cell populations in the regeneration process are discussed. Although intraoperative stem cell therapies have been shown to be safe and effective for several indications, there are still critical challenges to be tackled prior to adoption into the standard surgical armamentarium.

Regenerate augmentation with bone marrow concentrate after traumatic bone loss

Distraction osteogenesis after post-traumatic segmental bone loss of the tibia is a complex and time-consuming procedure that is often complicated due to prolonged consolidation or complete insufficiency of the regenerate. The aim of this feasibility study was to investigate the potential of bone marrow aspiration concentrate (BMAC) for percutaneous regenerate augmentation to accelerate bony consolidation of the regenerate. Eight patients (age 22-64) with an average posttraumatic bone defect of 82.4 mm and concomitant risk factors (nicotine abuse, soft-tissue defects, obesity and/or circulatory disorders) were treated with a modified Ilizarov external frame using an intramedullary cable transportation system. At the end of the distraction phase, each patient was treated with a percutaneously injection of autologous BMAC into the centre of the regenerate. The concentration factor was analysed using flow cytometry. The mean follow up after frame removal was 10 (4-15) months. With a mean healing index (HI) of 36.9 d/cm, bony consolidation of the regenerate was achieved in all eight cases. The mean concentration factor of the bone marrow aspirate was 4.6 (SD 1.23). No further operations concerning the regenerate were needed and no adverse effects were observed with the BMAC procedure. This procedure can be used for augmentation of the regenerate in cases of segmental bone transport. Further studies with a larger number of patients and control groups are needed to evaluate a possible higher success rate and accelerating effects on regenerate healing.

Application of stem cells in orthopedics

Stem cell research plays an important role in orthopedic regenerative medicine today. Current literature provides us with promising results from animal research in the fields of bone, tendon, and cartilage repair. While early clinical results are already published for bone and cartilage repair, the data about tendon repair is limited to animal studies. The success of these techniques remains inconsistent in all three mentioned areas. This may be due to different application techniques varying from simple mesenchymal stem cell injection up to complex tissue engineering. However, the ideal carrier for the stem cells still remains controversial. This paper aims to provide a better understanding of current basic research and clinical data concerning stem cell research in bone, tendon, and cartilage repair. Furthermore, a focus is set on different stem cell application techniques in tendon reconstruction, cartilage repair, and filling of bone defects.

Bone regeneration: stem cell therapies and clinical studies in orthopaedics and traumatology

Regenerative medicine seeks to repair or replace damaged tissues or organs, with the goal to fully restore structure and function without the formation of scar tissue. Cell based therapies are promising new therapeutic approaches in regenerative medicine. By using mesenchymal stem cells, good results have been reported for bone engineering in a number of clinical studies, most of them investigator initiated trials with limited scope with respect to controls and outcome. With the implementation of a new regulatory framework for advanced therapeutic medicinal products, the stage is set to improve both the characterization of the cells and combination products, and pave the way for improved controlled and well-designed clinical trials. The incorporation of more personalized medicine approaches, including the use of biomarkers to identify the proper patients and the responders to treatment, will be contributing to progress in the field. Both translational and clinical research will move the boundaries in the field of regenerative medicine, and a coordinated effort will provide the clinical breakthroughs, particularly in the many applications of bone engineering.