Fracture healing and bone regeneration: autologous bone grafting or BMPs?

Mangled extremity- Modern concepts in treatment

A mangled extremity is the most devastating limb injury and presents a challenge for the orthopedic surgeon. There are two main treatment options, reconstruction or amputation, but sometimes indications for either are not clear. There are many pro and contra arguments for both options. To make the decision easier numerous score systems have been introduced, but the final decision is based on the judgment and experience of the treating surgeon. Early extremity reconstruction appears to give better results than delayed or late reconstruction and should be the treatment of choice where possible. The goal in reconstruction of a lower extremity is to restore and maintain balance and ambulation, while restoration of an upper extremity's numerous functions is more demanding. In this paper the authors describe and suggest treatment approaches in patients with a severely mangled extremity, including assessment and treatment of all injured tissues, using defined protocols, with special attention to bone stabilization, revascularization, soft-tissue coverage and nerve reconstruction. These have a great impact on the outcome and function of the injured extremity. Rehabilitation and return to the preinjury level is slow and sometimes uncertain.

Safety study: is there a pathologic IGF-1, PDGF and TGF-β cytokine expression caused by adjunct BMP-7 in tibial and femoral non-union therapy?

Background

In this prospective safety study, we investigated if the characteristic cytokine expression during bone regeneration is manipulated by the local application of bone morphogenetic protein-7 (BMP-7) in non-union surgery. Therefore, the levels of insulin like growth factor 1 (IGF-1), platelet-derived growth factor AB (PDGF-AB) and transforming growth factor beta (TGF-β) were compared between patients with the gold standard use of autologous bone graft (ABG) and those with additional application of BMP-7 as part of the diamond concept.

Patients and methods

Between 2009 and 2014, of the 153 patients with tibial and femoral non-unions, a matched pair analysis was performed to compare the serological cytokine expressions. Blood samples were collected preoperatively, 1, 2 and 6 weeks as well as 3 and 6 months after non-union surgery. Matching criteria were smoking status, fracture location, gender, age and body mass index (BMI). Patients in G1 (n=10) were treated with ABG and local BMP-7 while their matching partners in G2 (n=10) received ABG only. The routine clinical and radiologic follow-up was 1 year.

Results

Although the IGF-1 quantification in G2 showed higher pre- and postoperative values compared to G1 (p<0.05), the courses of both groups were similar. Likewise, PDGF-AB and TGF-β expressions appeared similar in G1 and G2 with peaks in both groups at 2 weeks follow-up. Osseous consolidation was assessed in all operated non-unions. The adjunct application of BMP-7 did not cause any pathologic cytokine expression.

Conclusion

Similar expressions of the serum cytokines IGF-1, PDGF-AB and TGF-β were demonstrated in non-union patients treated with ABG and additional application of BMP-7 according to the diamond concept. Our findings indicate that the local application of BMP-7, which imitates the physiologic secretion of growth factors during bone regeneration, is safe and without the risk of abnormal systemic cytokine expression. Studies with higher patient numbers will have to validate these assumptions.

Biological methods to enhance bone healing and fracture repair

This article looks into normal physiological fracture healing with special emphasis on the diamond concept. A precise definition of nonunion of long bones is described. Most often inadequate fixation (too rigid or too loose) is the reason for nonunion in long bone fractures. Because a critical bone defect cannot be bridged, it may lead directly or indirectly (lack of fixation) to nonunion. Individual inadequate local biological characteristics are also often found to be the cause; poor soft tissue coverage as well as a lack of periosteum and muscle or fascia or skin defects can lead to compromised vascularity in situ. Systemic factors are now much more recognized, e.g., smoking, diabetes, and cachexia, as well as the limited impact of some medications, e.g., nonsteroidal anti-inflammatory drugs and steroids. Today's mode of treatment for nonunion is approached in this article, and suggestions for appropriate treatment of long bone nonunion is presented.

Cost analysis of fresh-frozen femoral head allografts: is it worthwhile to run a bone bank?

To assess the sustainability of our institutional bone bank, we calculated the final product cost of fresh-frozen femoral head allografts and compared these costs with the use of commercial alternatives. Between 2007 and 2010 all quantifiable costs associated with allograft donor screening, harvesting, storage, and administration of femoral head allografts retrieved from patients undergoing elective hip replacement were analysed. From 290 femoral head allografts harvested and stored as full (complete) head specimens or as two halves, 101 had to be withdrawn. In total, 104 full and 75 half heads were implanted in 152 recipients. The calculated final product costs were €1367 per full head. Compared with the use of commercially available processed allografts, a saving of at least €43 119 was realised over four-years (€10 780 per year) resulting in a cost-effective intervention at our institution. Assuming a price of between €1672 and €2149 per commercially purchased allograft, breakeven analysis revealed that implanting between 34 and 63 allografts per year equated to the total cost of bone banking.

Highly efficient release of simvastatin from simvastatin-loaded calcium sulphate scaffolds enhances segmental bone regeneration in rabbits

A number of clinical and experimental studies have investigated the effect of simvastatin on bone regeneration. In the present study, the release of simvastatin from simvastatin-loaded calcium sulphate (CS) scaffolds and the effect of these scaffolds on osteogenic differentiation of bone marrow-derived mesenchymal stem cells (MSCs) in vitro and the effect of simvastatin locally applied from CS scaffolds on bone regeneration were investigated. A total of 26 complete 1.2-cm bone defects were created in the ulna of rabbits, which were treated with CS, simvastatin-loaded CS or recombinant human bone morphogenetic protein 2 (rhBMP)-2-loaded CS. Simvastatin was highly efficiently released from simvastatin-loaded CS at the onset and stable release was maintained. Alkaline phosphatase was highly expressed in the MSCs co-cultured with simvastatin/CS scaffolds for 7 and 14 days. The defects treated with rhBMP-2-loaded CS and simvastatin-loaded CS showed significantly higher X-ray analysis scores and a larger amount of bone formation as determined by histology compared with the CS group (P<0.05). No significant differences in the X-ray score and bone formation were observed between groups with rhBMP-2-loaded CS and simvastatin-loaded CS (P>0.05). Simvastatin is capable of promoting osteogenic differentiation of MSCs in vitro and stimulating bone regeneration when locally released from CS scaffolds into bone defects. The beneficial effect of simvastatin was similar to that of rhBMP-2. In conclusion, the present study suggested that the simvastatin-loaded CS scaffolds may have great potential in bone tissue engineering.

Native multipotential stromal cell colonization and graft expander potential of a bovine natural bone scaffold

Graft expanders are bone scaffolds used, in combination with autografts, to fill large bone defects in trauma surgery. This study investigates the graft expander potential of a natural bone substitute Orthoss by studying its ability to support attachment, growth and osteogenic differentiation of neighboring multipotential stromal cells (MSCs). Material consisting of bone marrow (BM) aspirate and reamer-irrigator-aspirator (RIA)-harvested autograft bone was co-cultured with commercially available Orthoss granules. Native MSCs attached to Orthoss were expanded and phenotypically characterized. MSCs egress from neighboring cancelous bone was assessed in 3D Matrigel co-cultures. MSC differentiation was evaluated using scanning electron microscopy and measuring alkaline phosphatase (ALP) activity per cell. CD45(+) hematopoietic lineage cells and highly proliferative CD90(+) CD73(+) CD105(+) MSCs preferentially colonized Orthoss granules, over RIA bone chips. MSC colonization was followed by their intrinsic osteogenic differentiation, assessed as mineral deposition and gradual rise in ALP activity, even in the absence of osteogenic stimuli. When in contact with mixed cell populations and RIA chips, Orthoss granules support the attachment, growth and osteogenic differentiation of neighboring MSCs. Therefore, natural bone substitutes similar to Orthoss can be used as void fillers and graft expanders for repairing large bone defects in conjunction with autologous BM aspirates and autografts.

Enhancement of fracture healing with the diamond concept: the role of the biological chamber

Bone regeneration presents a unique challenge to both clinicians and scientists. Recently, a vast amount of knowledge has been attained with regard to the molecular mediators, cell populations and the overall cascade of events participating in the bone repair processes. For the treatment of bone non-unions or bone defects, the 'diamond concept' for biological enhancement supports the implantation of mesenchymal stem cells, a scaffold and a growth factor. Prior to the implantation of any or all of these materials however, the surgeon must develop the ideal biological environment (non-union bed) where molecular and physiological processes will evolve facilitating an early and successful osteogenesis leading to bone continuity and functional restoration of the affected limb. At the end of the surgical procedure the non-union bed should have been transformed to a 'biological chamber' active enough to support efficiently all the necessary physiological processes for a successful outcome. The notion of creating the optimum 'biological chamber' represents the centre of the highest biological activity and in a sense the heart of the diamond concept.

Evaluation of the osteoconductivity of α-tricalcium phosphate, β-tricalcium phosphate, and hydroxyapatite combined with or without simvastatin in rat calvarial defect

The purpose of this study is to evaluate the osteoconductivity of three different bone substitute materials: α-tricalcium phosphate (α-TCP), (β-TCP), and hydroxyapatite (HA), combined with or without simvastatin, which is a cholesterol synthesis inhibitor stimulating BMP-2 expression in osteoblasts. We used 72 Wistar rats and prepared two calvarial bone defects of 5 mm diameter in each rat. Defects were filled with the particles of 500-750 μm diameter combined with or without simvastatin at 0.1 mg dose for each defect. In the control group, defects were left empty. Animals were divided into seven groups: α-TCP, β-TCP, HA, α-TCP with simvastatin, β-TCP with simvastatin, HA with simvastatin, and control. The animals were sacrificed at 6 and 8 weeks. The calvariae were dissected out and analyzed with micro CT. The specimens were evaluated histologically and histomorphometrically. In α-TCP group, the amount of newly formed bone was significantly more than both HA and control groups but not significantly yet more than β-TCP group. Degradation of α-TCP was prominent and β-TCP showed slower rate while HA showed the least degradation. Combining the materials with Simvastatin led to increasing in the amount of newly formed bone. These results confirmed that α-TCP, β-TCP, and HA are osteoconductive materials acting as space maintainer for bone formation and that combining these materials with simvastatin stimulates bone regeneration and it also affects degradability of α-TCP and β-TCP. Conclusively, α-TCP has the advantage of higher rate of degradation allowing the more bone formation and combining α-TCP with simvastatin enhances this property.

The biology of intramedullary reaming

In this review we focus on the local biologic and physiologic effects of intramedullary reaming of long bones. Among the topics discussed are the consequences for vascularity, as well as the pathophysiology of intramedullary pressure generation and temperature increase. Reaming techniques and their suggested effects on bone formation are outlined. Moreover, techniques for avoiding local and systemic complications are summarized.

Cartilage repair evolution in post-traumatic osteochondral lesions of the talus: from open field autologous chondrocyte to bone-marrow-derived cells transplantation

The aims of this study are to describe evolution in cartilage repair from open field autologous chondrocyte implantation to regeneration by arthroscopic bone-marrow-derived cells (BMDCs) "one step" technique; to present the results of a series of patients consecutively treated and to compare in detail the different techniques used in order to establish the advantages obtained with the evolution in cartilage regenerative methods. 81 patients (mean age 30±8 years) were evaluated in this study. Patient assessment included clinical AOFAS score, X-rays and MRI preoperatively and at different established follow-ups. All the lesions were >1.5 cm(2) and received open autologous chondrocyte implantation (10 cases), arthroscopic autologous chondrocyte implantation (46 cases), and "one step" arthroscopic repair by BMDC transplantation (25 cases). For arthroscopic repair techniques a hyaluronic acid membrane was used to support cells and specifically designed instrumentation was developed. Patients of all the three groups underwent a second arthroscopy with a bioptic cartilage harvest at 1 year follow-up. Mean AOFAS score before surgery was 57.1±17.2 and 92.6±10.5 (P<0.0005) at mean 59.5±26.5 months. A similar pattern of AOFAS improvement in results was found in the three different techniques. Histological evaluations highlighted collagen type II and proteoglycan expression. The cartilage repair techniques described were able to provide a repair tissue which closely approximates the characteristics of the naive hyaline cartilage. Evolution in surgical technique, new biomaterials and more recently the use of BMDCs permitted a marked reduction in procedure morbidity and costs up to a "one step" technique able to overcome all the drawbacks of previous repair techniques.

Percutaneous techniques in the treatment of osteoporotic, traumatic and neoplastic fractures of thoraco-lumbar spine: our institutional experience

Fifty-eight (30 females) patients with a mean age of 55 were treated in our institution with minimal invasive surgery techniques for osteoporotic, traumatic and neoplastic fractures of the thoraco-lumbar spine. All patients completed pre-operatively and post-operatively the VAS score (0-10, 10 being the worst state for pain) as well as the Oswestry low back pain disability questionnaire at 3, 12, 24 and 36 months intervals. Overall the VAS score was reduced from 7.8 points pre-operatively, to 2.1 points at the 36 month follow up. Oswestry disability score improved from a pre-operative severe disability to moderate disability at 3 months up to a minimum disability at 36 months. The minimally invasive surgical techniques can significantly improve clinical outcomes by preventing many of the drawbacks associated with open approaches whilst also allowing to associate other methods such as coblation, vertebroplasty, interbody fusion that can be complementary to vertebral fixation.