Growth factor release following femoral nailing

An in vivo study to investigate an original intramedullary bone graft harvesting technology

BACKGROUND

Harvesting bone graft (BG) from the intramedullary canal to treat bone defects is largely conducted using the Reamer-Irrigator-Aspirator (RIA) system. The RIA system uses irrigation fluid during harvesting, which may result in washout of osteoinductive factors. Here, we propose a new harvesting technology dedicated to improving BG collection without the potential washout effect of osteoinductive factors associated with irrigation fluid. This novel technology involves the conceptual approach of first aspirating the bone marrow (BM) with a novel aspirator prototype, followed by reaming with standard reamers and collecting the bone chips with the aspirator (reaming-aspiration method, R-A method). The aim of this study was to assess the harvesting efficacy and osteoinductive profile of the BG harvested with RIA 2 system (RIA 2 group) compared to the novel harvesting concept (aspirator + R-A method, ARA group).

METHODS

Pre-planning computed tomography (CT) imaging was conducted on 16 sheep to determine the femoral isthmus canal diameter. In this non-recovery study, sheep were divided into two groups: RIA 2 group (n = 8) and ARA group (n = 8). We measured BG weight collected from left femur and determined femoral cortical bone volume reduction in postoperative CT imaging. Growth factor and inflammatory cytokine amounts of the BGs were quantified using enzyme-linked immunosorbent assay (ELISA) methods.

RESULTS

The use of the stand-alone novel aspirator in BM collection, and in harvesting BG when the aspirator is used in conjunction with sequential reaming (R-A method) was proven feasible. ELISA results showed that the collected BG contained relevant amounts of growth factors and inflammatory cytokines in both the RIA 2 and the ARA group.

CONCLUSIONS

Here, we present the first results of an innovative concept for harvesting intramedullary BG. It is a prototype of a novel aspirator technology that enables the stepwise harvesting of first BM and subsequent bone chips from the intramedullary canal of long bones. Both the BG collected with the RIA 2 system and the aspirator prototype had the capacity to preserve the BG's osteoinductive microenvironment. Future in vivo studies are required to confirm the bone regenerative capacity of BG harvested with the innovative harvesting technology.

Reaming the intramedullary canal during tibial nailing does not affect in vivo intramuscular pH of the anterior tibialis

Many investigations have evaluated local and systemic consequences of intramedullary (IM) reaming and suggest that reaming may cause, or exacerbate, injury to the soft tissues adjacent to fractures. To date, no study has examined the effect on local muscular physiology as measured by intramuscular pH (IpH). Here, we observe in vivo IpH during IM reaming for tibia fractures.

Methods

Adults with acute tibia shaft fractures (level 1, academic, 2019-2021) were offered enrollment in an observational cohort. During IM nailing, a sterile, validated IpH probe was placed into the anterior tibialis (<5 cm from fracture, continuous sampling, independent research team). IpH before, during, and after reaming was averaged and compared through repeated measures ANOVA. As the appropriate period to analyze IpH during reaming is unknown, the analysis was repeated over periods of 0.5, 1, 2, 5, 10, and 15 minutes prereaming and postreaming time intervals.

Results

Sixteen subjects with tibia shaft fractures were observed during nailing. Average time from injury to surgery was 35.0 hours (SD, 31.8). Starting and ending perioperative IpH was acidic, averaging 6.64 (SD, 0.21) and 6.74 (SD, 0.17), respectively. Average reaming time lasted 15 minutes. Average IpH during reaming was 6.73 (SD, 0.15). There was no difference in IpH between prereaming, intrareaming, and postreaming periods. IpH did not differ regardless of analysis over short or long time domains compared with the duration of reaming.

Conclusions

Reaming does not affect IpH. Both granular and broad time domains were tested, revealing no observable local impact.

Resolution of Psoriatic Plaques of the Leg After Nailing of an Ipsilateral Tibial Shaft Fracture: A Case Report

CASE

This case describes a 45-year-old man with documented history of untreated bilateral lower extremity psoriasis of equal severity who sustained a closed left tibial-fibular shaft fracture. After operative fixation with an intramedullary nail under a regional nerve block, the left lower extremity circumferential psoriatic plaque resolved throughout 1 year of follow-up with persistence of the contralateral limb disease.

CONCLUSION

This case describes a rare outcome for a patient with bilateral leg psoriasis who experienced resolution of psoriatic plaques on the operated leg only after surgery. It is unknown which process: injury, anesthetic, surgery, or fracture healing mediated this unique finding.

Clinical Data for Parametrization of In Silico Bone Models Incorporating Cell-Cytokine Dynamics: A Systematic Review of Literature

In silico simulations aim to provide fast, inexpensive, and ethical alternatives to years of costly experimentation on animals and humans for studying bone remodeling, its deregulation during osteoporosis and the effect of therapeutics. Within the varied spectrum of in silico modeling techniques, bone cell population dynamics and agent-based multiphysics simulations have recently emerged as useful tools to simulate the effect of specific signaling pathways. In these models, parameters for cell and cytokine behavior are set based on experimental values found in literature; however, their use is currently limited by the lack of clinical in vivo data on cell numbers and their behavior as well as cytokine concentrations, diffusion, decay and reaction rates. Further, the settings used for these parameters vary across research groups, prohibiting effective cross-comparisons. This review summarizes and evaluates the clinical trial literature that can serve as input or validation for in silico models of bone remodeling incorporating cells and cytokine dynamics in post-menopausal women in treatment, and control scenarios. The GRADE system was used to determine the level of confidence in the reported data, and areas lacking in reported measures such as binding site occupancy, reaction rates and cell proliferation, differentiation and apoptosis rates were highlighted as targets for further research. We propose a consensus for the range of values that can be used for the cell and cytokine settings related to the RANKL-RANK-OPG, TGF-β and sclerostin pathways and a Levels of Evidence-based method to estimate parameters missing from clinical trial literature.

Effect of Time Lag from Injury to Surgery on the Temporal Expression of Growth Factors After Intramedullary Nailing of Isolated Fracture of Femur Shaft

BACKGROUND

Growth factors are considered to play an important role in the process of bone healing. This study assessed serum levels of transforming growth factor-β1 (TGF-β1) and vascular endothelial growth factor (VEGF) in patients undergoing intramedullary nailing for isolated fracture of femur shaft operated at various time lag from injury.

PATIENTS AND METHODS

All patients between 18 and 60 years of age group operated for isolated femoral shaft fractures (AO/OTA32 A, B, C) were included. The serum levels of VEGF and TGF-β1 were compared at various intervals amongst the study group divided into two groups based on the time lag between injury and surgery along with a health control cohort.

RESULTS

31 patients were operated within the first 48 h while 28 patients were operated within 2-12 days after injury. Highest VEGF levels were observed on postop day 3, followed by a subsequent decline thereafter. TGF-β1 level also showed increasing trend after surgery, but the levels reached dual peaks after 2 weeks and 12 weeks after surgery. Both groups revealed similar trends of temporal expression of serum VEGF and TGF-β1. There was no statistical difference between the two groups at any point of time during the observation period. There was also no statistical difference in clinico-radiological healing of fractures among the groups.

CONCLUSION

There is a definite and specific trend of serum levels of growth factors in the fracture healing process. There is no effect of time lag from injury to surgery on the healing outcome of isolated femoral shaft fractures both at the molecular level and also at the clinical level.

Femoral non-union above a fused knee: Successful treatment with exchange nailing and intramedullary delivery of bone morphogenetic protein

Bone healing is a complex and well-orchestrated physiological process, in which bone repairs and regenerates regaining its original biomechanical and biochemical properties. It is estimated that 5 to 10% of all fractures are complicated by delayed union or non-union. Progression to non-union is thought to be multifactorial, even though the exact biological sequence remains obscure. Treatment should aim to addressing deficiencies in both the mechanical and biological components, along with eliminating co-factors that could negatively affect the locally induced fracture healing response. We report a case of a 78-year-old patient who presented with a distal femoral non-union above a previously fused knee, which was successfully managed with exchange nailing and intramedullary delivery of recombinant human bone morphogenetic protein-7 (rhBMP-7).

[Femoral shaft fractures]

Femoral shaft fractures after completion of growth predominantly affect young people with healthy bones. The causes are mostly high-velocity traffic accidents, crushing or running over mechanisms and falls from a great height. Gunshot wounds are relatively rare in Germany but have a certain importance internationally and in military medicine. Accompanying injuries in local or other regions are frequent. The predominant fracture types are transverse, wedge, segment and comminuted fractures. Spiral fractures are a sign of indirect force and are therefore frequently found in older patients with osteoporosis. Atypical fractures under or following bisphosphonate treatment are a new entity, which are typically subtrochanteric and begin on the lateral side of the bone. The characteristics of pathological fractures, femoral shaft fractures in childhood and adolescence as well as periprosthetic fractures are not dealt with in this article.

Elevated concentrations of hypoxia-inducible factor-1α in patients with fracture and concomitant traumatic brain injury

Background Compelling evidence indicate that traumatic brain injury is highly related to accelerated bone fracture repair, but the underlying mechanism still remains elusive. Fracture repair process relies greatly on the formation of new blood vessels in fracture site, and angiogenic factors have been confirmed to be essential for the initiation and maintenance of the fracture healing. Hypoxia-inducible factor-1α was demonstrated to be a critical regulator of angiogenic-osteogenic coupling during bone development and regeneration. The aim of the present study was to investigate the local and circulating concentrations of hypoxia-inducible factor-1α in patients with long-bone fractures and concomitant traumatic brain injury and to determine the potential role of hypoxia-inducible factor-1α in fracture healing. Methods Twenty-five patients with a long-bone fracture and concomitant traumatic brain injury (FT group) and 33 without a brain injury (Fr group) were enrolled in this study. Healthy subjects donated serum samples as control. Serum samples were collected over a period of six months, following a standardized time schedule. Hypoxia-inducible factor-1α concentrations were measured in fracture haematoma and serum of patients in both groups using enzyme-linked immunosorbent assay. Results Patients in FT group had a short time to union. Serum hypoxia-inducible factor-1α concentrations elevated in the early healing period and reached the maximum level during intramembranous bone formation phase in both groups. Thereafter, it decreased continuously and approached to the minimum levels until the end of the observation period. Serum hypoxia-inducible factor-1α concentrations in both groups were significantly higher compared with controls and hypoxia-inducible factor-1α concentrations in both serum and fracture haematoma were higher in FT group than that in Fr group. Fracture haematoma contained significantly higher hypoxia-inducible factor-1α concentrations compared with hypoxia-inducible factor-1α concentrations in serum. Serum hypoxia-inducible factor-1α concentrations had a positive correlation with hypoxia-inducible factor-1α concentrations in fracture haematoma in patients with fractures. Conclusions These findings suggest the local and systemic involvement of hypoxia-inducible factor-1α in fracture healing and the accelerated fracture repair in patients with traumatic brain injury might be associated with elevated hypoxia-inducible factor-1α concentrations in fracture haematoma and serum.

Early intramedullary nailing of femoral shaft fracture on outcomes in patients with severe chest injury: A meta-analysis

Early intramedullary nailing (IMN) within the first 24 hours for multiply injured patients with femoral fracture and concomitant severe chest injury is still controversial. This review aimed to investigate the association between early IMN and pulmonary complications in such patients. We searched the literature up to Jan 2016 in the main electronic databases (PubMed, Web of Science, Cochrane library databases) to identify eligible studies. Data were extracted and analyzed using a Mantel-Haenszel method with random-effects model to estimate pooled odds ratio (OR) and 95% confidence intervals (CIs). Seven retrospective cohort studies were identified eventually. The pooled estimates demonstrated that the application of early IMN did not significantly increase the risk of adult respiratory distress syndrome (ARDS) (OR, 0.65; 95% CI: 0.38-1.13), mortality (OR, 0.79; 95% CI: 0.43-1.47), pneumonia (OR, 0.92; 95% CI: 0.55-1.54), multiple organ failure (MOF) (OR, 0.87; 95% CI: 0.45-1.71) and pulmonary embolism (OR, 1.81; 95% CI: 0.28-11.83). In subgroup analysis according to the type of IMN (reamed or undreamed), we did not find any significant difference either. Our results indicated that early IMN of femoral shaft fracture was not associated with increased rates of pulmonary complications in severe chest-injured patients.

Platelet-Derived Growth Factor BB Enhances Osteogenesis of Adipose-Derived But Not Bone Marrow-Derived Mesenchymal Stromal/Stem Cells

Tissue engineering using mesenchymal stem cells (MSCs) holds great promise for regenerating critically sized bone defects. While the bone marrow-derived MSC is the most widely studied stromal/stem cell type for this application, its rarity within bone marrow and painful isolation procedure have motivated investigation of alternative cell sources. Adipose-derived stromal/stem cells (ASCs) are more abundant and more easily procured; furthermore, they also possess robust osteogenic potency. While these two cell types are widely considered very similar, there is a growing appreciation of possible innate differences in their biology and response to growth factors. In particular, reports indicate that their osteogenic response to platelet-derived growth factor BB (PDGF-BB) is markedly different: MSCs responded negatively or not at all to PDGF-BB while ASCs exhibited enhanced mineralization in response to physiological concentrations of PDGF-BB. In this study, we directly tested whether a fundamental difference existed between the osteogenic responses of MSCs and ASCs to PDGF-BB. MSCs and ASCs cultured under identical osteogenic conditions responded disparately to 20 ng/ml of PDGF-BB: MSCs exhibited no difference in mineralization while ASCs produced more calcium per cell. siRNA-mediated knockdown of PDGFRβ within ASCs abolished their ability to respond to PDGF-BB. Gene expression was also different; MSCs generally downregulated and ASCs generally upregulated osteogenic genes in response to PDGF-BB. ASCs transduced to produce PDGF-BB resulted in more regenerated bone within a critically sized murine calvarial defect compared to control ASCs, indicating PDGF-BB used specifically in conjunction with ASCs might enhance tissue engineering approaches for bone regeneration.

Transforming growth factor Beta family: insight into the role of growth factors in regulation of fracture healing biology and potential clinical applications

The transforming growth factor beta (TGF-β) family forms a group of three isoforms, TGF-β1, TGF-β2, and TGF-β3, with their structure formed by interrelated dimeric polypeptide chains. Pleiotropic and redundant functions of the TGF-β family concern control of numerous aspects and effects of cell functions, including proliferation, differentiation, and migration, in all tissues of the human body. Amongst many cytokines and growth factors, the TGF-β family is considered a group playing one of numerous key roles in control of physiological phenomena concerning maintenance of metabolic homeostasis in the bone tissue. By breaking the continuity of bone tissue, a spread-over-time and complex bone healing process is initiated, considered a recapitulation of embryonic intracartilaginous ossification. This process is a cascade of local and systemic phenomena spread over time, involving whole cell lineages and various cytokines and growth factors. Numerous in vivo and in vitro studies in various models analysing cytokines and growth factors' involvement have shown that TGF-β has a leading role in the fracture healing process. This paper sums up current knowledge on the basis of available literature concerning the role of the TGF-β family in the fracture healing process.

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

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

Decreased serum platelet derived growth factor BB levels in acute and increased in chronic pancreatitis

AIM: To examine circulating growth factor concentrations in patients with acute pancreatitis (AP) and chronic pancreatitis (CP), and walled-off pancreatic necrosis (WOPN).

METHODS: Forty patients with mild AP, 40 patients with alcoholic CP, 33 patients with WOPN and 40 healthy subjects were examined. Serum concentrations of platelet derived growth factor BB (PDGF-BB), transforming growth factor β-1 (TGFβ-1), chemerin and high-mobility group box chromosomal protein 1 (HMBG1) were assayed by enzyme linked immunosorbent assay.

RESULTS: Patients with mild AP and those with WOPN had significantly lower serum levels of PDGF-BB compared to healthy subjects (4.0 ± 0.61 ng/mL vs 6.2 ± 0.76 ng/mL, P = 0.027, and 1.60 ± 0.31 ng/mL vs 6.2 ± 0.76 ng/mL, P < 0.001, respectively), while CP was associated with higher serum levels of PDGF-BB (12 ± 1.3 ng/mL vs 6.2 ± 0.76 ng/mL, P < 0.001). Circulating TGFβ-1 and chemerin levels were elevated in CP patients (57 ± 3.6 ng/mL vs 39 ± 3.6 ng/mL, P < 0.001 and 73 ± 7.2 ng/mL vs 48 ± 2.3 ng/mL, P < 0.001, respectively), but not in patients with AP and WOPN. No significant changes in serum HMBG1 levels were found either in patients with AP, WOPN or CP.

CONCLUSION: The serum levels of some growth factors and cytokines differ significantly in AP, WOPN and CP. These data suggest that selected growth factors and cytokines may be considered as potential diagnostic biomarkers in patients with pancreatic diseases.

Sequential harvesting of bone graft from the intramedullary canal of the femur

The effectiveness of using the Reamer/Irrigator/Aspirator (RIA) System (Synthes, Inc, West Chester, Pennsylvania) to obtain bone graft from the intramedullary canal of long bones for the treatment of bone defects and nonunions has been previously documented. However, there is nothing in the literature discussing the potential for reaming the same canal at subsequent surgeries. The authors detail their experience of 8 instances of sequential reaming in 7 patients. Six patients were harvested twice, and 1 patient was harvested 3 times. In each patient, the bone graft was obtained from the same canal. The main outcome measurements were time interval between reamings, reamer head size, indication for reaming, volume of harvested bone graft, and complications. Average volume of graft obtained in the first reaming procedure was 34 mL (range, 25-50 mL). After an average of 9 months (range, 3-16 months), the subsequent reaming was performed. Average volume of graft obtained in the second procedure was 45 mL (range, 28-65 mL). In the authors' series, no reaming-related complications were observed. The graft volume was the same or increased during the subsequent intramedullary reaming in all but 1 case, suggesting that the intramedullary canal is a potentially renewable source for bone graft. There were no complications related to the sequential reaming procedure. Overall, the authors' data suggest that sequential reaming with the RIA has the potential to safely and effectively provide a large quantity of bone graft on multiple occasions.

Fracture non-union: Can biomarkers predict outcome?

Delayed bone healing and non-union occurs in approximately 10-15% of long bone fractures. Both pathologies may result in prolonged period of pain, disability and repetitive operative interventions. Despite intense investigations and progress done in understanding the pathophysiologic processes governing bone healing, the diagnostic tools have not been altered. The clinical findings and radiographic features remain the two important landmarks of diagnosing non-union and even when the diagnosis is established there is debate on the ideal timing and mode of intervention. Emerging evidence suggest that there are certain molecules and genes that can serve as predictors of potentially unsuccessful fracture union. This article summarises the current evidence on the available 'bio-markers'to predict fracture non-union.

The viability of cells obtained using the Reamer–Irrigator–Aspirator system and in bone graft from the iliac crest

We hypothesised that cells obtained via a Reamer–Irrigator–Aspirator (RIA) system retain substantial osteogenic potential and are at least equivalent to graft harvested from the iliac crest. Graft was harvested using the RIA in 25 patients (mean age 37.6 years (18 to 68)) and from the iliac crest in 21 patients (mean age 44.6 years (24 to 78)), after which ≥ 1 g of bony particulate graft material was processed from each. Initial cell viability was assessed using Trypan blue exclusion, and initial fluorescence-activated cell sorting (FACS) analysis for cell lineage was performed. After culturing the cells, repeat FACS analysis for cell lineage was performed and enzyme-linked immunosorbent assay (ELISA) for osteocalcin, and Alizarin red staining to determine osteogenic potential. Cells obtained via RIA or from the iliac crest were viable and matured into mesenchymal stem cells, as shown by staining for the specific mesenchymal antigens CD90 and CD105. For samples from both RIA and the iliac crest there was a statistically significant increase in bone production (both p < 0.001), as demonstrated by osteocalcin production after induction.

Medullary autograft cells harvested using RIA are viable and osteogenic. Cell viability and osteogenic potential were similar between bone grafts obtained from both the RIA system and the iliac crest.

Cite this article: Bone Joint J 2013;95-B:1269–74.

Platelet-derived growth factor and spatiotemporal cues induce development of vascularized bone tissue by adipose-derived stem cells

Vasculature is essential to the functional integration of a tissue-engineered bone graft to enable sufficient nutrient delivery and viability after implantation. Native bone and vasculature develop through intimately coupled, tightly regulated spatiotemporal cell-cell signaling. The complexity of these developmental processes has been a challenge for tissue engineers to recapitulate, resulting in poor codevelopment of both bone and vasculature within a unified graft. To address this, we cultured adipose-derived stromal/stem cells (ASCs), a clinically relevant, single cell source that has been previously investigated for its ability to give rise to vascularized bone grafts, and studied the effects of initial spatial organization of cells, the temporal addition of growth factors, and the presence of exogenous platelet-derived growth factor-BB (PDGF-BB) on the codevelopment of bone and vascular tissue structures. Human ASCs were aggregated into multicellular spheroids via the hanging drop method before encapsulation and subsequent outgrowth in fibrin gels. Cellular aggregation substantially increased vascular network density, interconnectivity, and pericyte coverage compared to monodispersed cultures. To form robust vessel networks, it was essential to culture ASCs in a purely vasculogenic medium for at least 8 days before the addition of osteogenic cues. Physiologically relevant concentrations of exogenous PDGF-BB (20 ng/mL) substantially enhanced both vascular network stability and osteogenic differentiation. Comparisons with the bone morphogenetic protein-2, another pro-osteogenic and proangiogenic growth factor, indicated that this potential to couple the formation of both lineages might be unique to PDGF-BB. Furthermore, the resulting tissue structure demonstrated the close association of mineral deposits with pre-existing vascular structures that have been described for developing tissues. This combination of a single cell source with a potent induction factor used at physiological concentrations can provide a clinically relevant approach to engineering highly vascularized bone grafts.

Bone morphogenetic proteins and the polycystic ovary syndrome

Background

Polycystic Ovary Syndrome (PCOS) is defined by two out of the following three criteria being met: oligo- or anovulation, hyperandrogenism, and polycystic ovaries. Affected women are often obese and insulin resistant. Although the etiology is still unknown, members of the Transforming Growth Factor β (TGFβ) family, including Bone Morphogenetic Proteins (BMPs) and anti-Müllerian hormone (AMH), have been implicated to play a role. In this pilot study we aimed to measure serum BMP levels in PCOS patients.

Methods

Twenty patients, fulfilling the definition of PCOS according to the Rotterdam Criteria, were randomly selected. Serum BMP2, -4, -6 and −7 levels were measured using commercially available BMP2, BMP4, BMP6 and BMP7 immunoassays.

Results

Serum BMP2, serum BMP4 and serum BMP6 levels were undetectable. Three patients had detectable serum BMP7 levels, albeit at the lower limit of the standard curve.

Conclusions

BMP levels were undetectable in almost all patients. This suggests that with the current sensitivity of the BMP assays, measurement of serum BMP levels is not suitable as a diagnostic tool for PCOS.

Release of growth factors and the effect of age, sex, and severity of injury after long bone fracture. A preliminary report

BACKGROUND AND PURPOSE

The systemic response after fracture is regulated by a complex mechanism involving numerous growth factors. In this study, we analyzed the kinetics of key growth factors following lower-limb long bone fracture.

MATERIALS AND METHODS

Human serum was isolated from 15 patients suffering from lower-limb long bone fracture (tibia/femur) requiring surgical fixation. The levels of platelet-derived growth factor (PDGF-BB), vascular edothelial growth factor (VEGF), insulin growth factor-I (IGF-I), and transforming growth factor β1 (TGF-β1) were assayed by colorimetric ELISA at different time points during the first week after fracture. 10 healthy volunteers made up the control group of the study. Serum levels of the growth factors measured were compared to age, sex, and injury severity score.

RESULTS

We found that there was a decline in the levels of PDGF-BB, IGF-I and TGF-β1 during the first 3 days after fracture. However, VEGF levels remained unchanged. The levels of all the growth factors studied then increased, with the highest concentrations noted at day 7 after surgery. No correlation was found between circulating levels of growth factors and age, injury severity score (ISS), blood loss, or fluid administration.

INTERPRETATION

There are systemic mitogenic and osteogenic signals after fracture. Important growth factors are released into the peripheral circulation, but early after surgery it appears that serum levels of key growth factors fall. By 7 days postoperatively, the levels had increased considerably. Our findings should be considered in cases where autologous serum is used for ex vivo expansion of mesenchymal stem cells. There should be further evaluation of the use of these molecules as biomarkers of bone union.

Osteochondral tissue engineering: current strategies and challenges

Osteochondral defect management and repair remain a significant challenge in orthopedic surgery. Osteochondral defects contain damage to both the articular cartilage as well as the underlying subchondral bone. In order to repair an osteochondral defect the needs of the bone, cartilage and the bone-cartilage interface must be taken into account. Current clinical treatments for the repair of osteochondral defects have only been palliative, not curative. Tissue engineering has emerged as a potential alternative as it can be effectively used to regenerate bone, cartilage and the bone-cartilage interface. Several scaffold strategies, such as single phase, layered, and recently graded structures have been developed and evaluated for osteochondral defect repair. Also, as a potential cell source, tissue specific cells and progenitor cells are widely studied in cell culture models, as well with the osteochondral scaffolds in vitro and in vivo. Novel factor strategies being developed, including single factor, multi-factor, or controlled factor release in a graded fashion, not only assist bone and cartilage regeneration, but also establish osteochondral interface formation. The field of tissue engineering has made great strides, however further research needs to be carried out to make this strategy a clinical reality. In this review, we summarize current tissue engineering strategies, including scaffold design, bioreactor use, as well as cell and factor based approaches and recent developments for osteochondral defect repair. In addition, we discuss various challenges that need to be addressed in years to come.

A preliminary study of platelet activation after embolization of marrow contents

OBJECTIVES

Intravasation of bone marrow contents into venous circulation and pulmonary embolization after intramedullary nailing may be coupled with the activation of coagulation and fibrinolytic cascades. The objective of this study was to assess hemostatic response to pulmonary extravasated marrow contents. We hypothesize that activation of platelet activity and the coagulation cascade may occur after embolization of marrow contents in an experimental animal model of intramedullary nailing.

METHODS

Fifteen New Zealand white male rabbits were randomly assigned to control or fat embolism (FE) groups. In the FE group (n = 8), femurs were surgically instrumented with retrograde intramedullary nails and pressurized with bone cement. In the control group (n = 7), a sham knee incision was made that was immediately closed without drilling, reaming, or pressurization. Fibrinogen, D-dimer latex screen assay, 1 stage prothrombin time, and activated partial thromboplastin time were analyzed.

RESULTS

As the main platelet activation indicators, the marker Annexin-V percent binding increased in the FE group at 2 hours (P = 0.04) and 4 hours (P = 0.04), and the marker CD62P percent expression increased in the FE group at 2 hours (P = 0.04).

CONCLUSIONS

This preliminary study showed that pressurization of marrow and intravasation of fat and marrow products cause activation of platelets and the coagulation cascade, with or without tissue trauma. This may be relevant to the treatment of multiply injured patients with prior respiratory and coagulation abnormalities. A future larger study may be needed.

Are polymorphisms of molecules involved in bone healing correlated to aseptic femoral and tibial shaft non-unions?

Fracture healing is a well-organized process between several molecules and mediators. As known from other diseases, genetic polymorphisms may exhibit different expression patterns in these mediators. Concerning fracture healing, this may lead to an extended healing process or non-union. We investigated the incidence of polymorphisms in patients with aseptic non-unions after femoral and tibial shaft fractures as compared to patients with uneventful healing. Exclusion criteria were smoking, diabetes, bilateral fractures, systemic corticoid therapy, and septic non-unions. Analysis of allele frequencies and genotype distribution of various mediators were carried out following PCR. Clinical parameters such as injury severity and in-hospital were analyzed. Fifty patients following non-union (group NU) were enrolled, the control group consisted of 44 patients (group H). A significant association of a PDGF haplotype and non-unions following fracture could be observed. There was a significantly increased in-hospital time and amount of surgical procedures in group NU. Polymorphisms within the PDGF gene seem to be a genetic risk factor for the development of non-unions of the lower extremity following fracture. The early identification of high risk patients could result in an adapted therapeutical strategy and might contribute to a significant decrease of posttraumatic non-unions.

Elevated transforming growth factor-beta 1 (TGF-β1) levels in human fracture healing

INTRODUCTION

Transforming growth factor-beta 1(TGF-β1) is a regulatory protein, involved in bone fracture healing. Circulating TGF-β1 levels have been reported to be a predictor of delayed bone healing and non-union, suggesting active relationship between tissue and circulating TGF-β1 in fracture healing. The purpose of this study was to analyse TGF-β1 local and serum concentrations in fracture healing to further contribute to the understanding of molecular regulation of fracture healing.

PATIENTS AND METHODS

Serum samples of 113 patients with long bone fractures were collected over a period of 6 months following a standardised time schedule. TGF-β1 serum concentrations were measured using ELISA. Patients were assigned to 2 groups: Group 1 contained 103 patients with physiological healing. Group 2 contained 10 patients with impaired healing. Patients in both groups were matched. One patient of the group 2 had to be excluded because of missing match partner. In addition, fracture haematoma from 11 patients of group 1 was obtained to analyse local TGF-β1 concentrations. 33 volunteers donated serum which served as control.

RESULTS

TGF-β1 serum concentrations increased during the early healing period and were significantly higher in patients with physiological healing compared to controls (P=0.04). Thereafter, it decreased continuously between weeks 2 and 8 and fell again after week 8. TGF-β1 serum concentrations in patients with physiological healing were significantly higher at week 24 compared to controls (P=0.05). In non-unions, serum concentrations differed significantly from those of controls at week 6 (P=0.01). No significant difference in between patients with physiological and impaired fracture healing was observed. Fracture haematoma contained significantly higher TGF-β1 concentrations than peripheral serum of the patients (P=0.017).

CONCLUSION

Elevated levels of TGF-β1 in haematoma and in serum after bone fracture especially during the entire healing process indicate its importance for fracture healing.

Growth factor release in extra- and intramedullary osteosynthesis following tibial fracture

INTRODUCTION

Recent studies indicate alterations of local and systemic growth factor level during fracture healing. As a result, osteogenic and angiogenic growth factors allow us to monitor fracture healing on a molecular level. We hypothesised that closed intramedullary (IM) reaming and nail fixation, in contrast to open reduction and internal plate fixation (ORIF), could exert an effect on the cellular elements present in the intramedullary canal, leading to increased release of mediators. The purpose of the study was to investigate whether different osteosynthesis techniques influence the released quantity of cytokines.

PATIENTS AND METHODS

A total of 34 patients with tibia fractures treated with IM fixation and 19 patients treated with ORIF were included in the study. In addition to clinical and radiological examination, serum concentrations of transforming growth factor beta 1(TGF-β1), macrophage-colony stimulating factor (M-CSF) and vascular endothelial growth factor (VEGF), were analysed at 1, 2, 4, 6, 8, 12, and 24 weeks after surgery.

RESULTS

Expression of TGF-β1 and M-CSF was increased during the first 2 weeks of fracture healing in patients treated with the IM fixation technique compared with those treated by ORIF. After 24 weeks, M-CSF levels in patients with IM fixation were clearly higher. Conversely, VEGF levels were higher during the first 2 weeks of fracture healing in patients treated by ORIF compared with IM fixation. However, these results were not significant.

CONCLUSION

Our results show that 1 week after surgery neither reamed IM fixation nor ORIF of the tibia could increase the expression of VEGF, M-CSF and TGF-β1 in its favour.

Fracture healing after reamed and unreamed intramedullary nailing in sheep tibia

Intramedullary nailing is a well-established method for stabilisation of long-bone shaft fractures. It is still a controversy as to whether the procedure should be done by an unreamed or reamed technique. In the present animal study, 24 sheep were treated with intramedullary nailing. Midshaft fractures (Arbeitsgemeinschaft für Osteosynthese (AO) type 42-A2/3) were created. Eight sheep were treated with an unreamed nailing technique (UN), a further eight sheep underwent tibia nailing by the reamed technique using the conventional AO reaming system (RC) and in a further eight sheep, reamed nailing was performed using an experimental reaming system (RE). Intra-operatively, the intramedullary pressure was measured and, during a healing time of 10 weeks, the growth of callus formation was labelled with fluorescence markers after 4 and 6 weeks. After 10 weeks, the animals were euthanised and the quality of fracture healing was determined by recording stiffness in torsion, antero-posterior and mediolateral bending and the load at yield. In addition, the callus formation at the fracture zone was evaluated by fluorescence microscopy and macroradiographs. The results showed a decrease of intramedullary pressure when reamed nailing was performed with the RE (72.5 mmHg) system compared with the conventional AO reaming system (227 mmHg). Mechanical testing did not reveal any significant differences either for torsional or bending stiffness or for load at yield for any of the three procedures. Histological evaluation showed a similar callus formation for the UN group and the RE group. Callus formation in the UN (65 mm(2)) and RE (63 mm(2)) groups showed a higher increase during the first 6 weeks than those treated with the conventional AO reaming system (27 mm(2)). This means that, especially during the first weeks of fracture healing, damage to the bone by the reaming process can be reduced by reaming with a reaming device with lowered cutting flutes and smaller drive-shaft diameter. Intramedullary pressure can be significantly reduced by using reaming systems with reduced drive-shaft diameters and deepened cutting flutes. In the early phase of fracture healing, callus formation can be influenced positively when using the RE system.

Bone graft harvesting using the RIA (reaming irrigation aspirator) system - a quantitative assessment

INTRODUCTION

Autologous bone graft is still considered to be the gold standard for treating non-unions in trauma and orthopedic surgery. Intramedullary bone graft harvest appears to be an alternative to other bone graft options such as iliac crest bone graft and synthetic bone substitutes. A one-step reamer-irrigator-aspirator (RIA) system has been developed to reduce the intramedullary pressure and, as a consequence, minimize the risk of fat embolization. The purpose of this study was to determine whether the quantity of harvested intramedullary bone graft is comparable to the quantity of graft that was harvested from the iliac crest in other studies. The aim of the present study was to quantify harvested bone marrow and to compare our results to already published data.

METHODS

Eight human cadavers (7 males, 1 female, and 16 limbs) with an average age of 68 years (range, 49-79 years) were obtained for this study. Intramedullary reaming was performed in the tibiae and femora of each cadaver. Two different sizes (12- and 14-mm diameter) of the RIA system were used. After a medial parapatellar incision was made at the knee, antegrade and retrograde reaming were performed in the tibiae and femur to harvest bone graft.

RESULTS

A significantly greater quantity of bone graft was harvested from the femora (27 ± 12 g) than the tibiae (17 ± 9 g) (p = 0.007).

CONCLUSIONS

On the basis of our present results, harvesting intramedullary bone graft with the RIA system appears to be an innovative technique for bone grafting in limb reconstruction. A significantly greater quantity of bone graft was harvested from the femora than the tibiae (p = 0.007). No significant differences among age, sex, body weight, bone length, or BMI were observed. Our results showed that a sufficient quantity in weight of autogenous bone graft could be obtained using the RIA system.

Serum transforming growth factor beta-1 post hip fracture repair in elderly patients

BACKGROUND

To determine the kinetics of serum transforming growth factor beta-1 (TGF-β1) in aged hip fracture patients during a month post-op. and determine its relationship to complications and cognitive status.

METHODS

Forty-one elderly patients were prospectively followed. Serum TGF-β1 was obtained during the first 10h post-fracture (baseline) and pre-surgery, 48-60 h post-op., 7 and 30 days post-op.

RESULTS

Mean age was 81.8±7.7, range 68-97 years. A significant increase in serum TGF-β1 (from baseline) was observed on the seventh day post-op., lasting for at least 1 month (p = 0.004). Sixteen patients experienced post-op. complications. Serum TGF-β1 of patients with complications was significantly higher compared to patients without complications (p = 0.039). More complications were found in impaired mental status (IMS) patients (9/12) compared to cognitively normal patients (10/29), (p = 0.037). However, no differences were found in serum TGF-β1 between IMS and normal patients, nor was a correlation found between age and TGF-β1 production. No differences were found between genders.

CONCLUSIONS

There is a distinct increase in serum TGF-β1, a week post hip fracture repair, lasting for at least a month, which is significantly higher in patients with post-op. complications. TGF-β1 seems to be essential to the healing process post hip fracture repair; still its clinical applications have as yet to be determined.

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.

Extruded osteoarticular distal tibia: success at 18-month follow-up with reimplantation

Extruded bone is a rare complication of open fractures associated with high energy. We describe a case of bony extrusion involving an osteoarticular segment of distal tibial treated with reimplantation and internal fixation with 18-month follow-up.

Elevated levels of macrophage colony-stimulating factor in human fracture healing

Macrophage colony-stimulating factor (M-CSF) plays a unique role in bone remodeling. However, to our knowledge, no data on the role of M-CSF in fracture healing in humans have been published so far. This study addressed this issue. One hundred and thirteen patients with long-bone fractures were included in the study and divided into two groups, according to their course of fracture healing. The first group contained 103 patients with normal fracture healing. Ten patients with impaired fracture healing formed the second group of the study. Volunteers donated blood samples as control. Serum samples were collected over a period of 6 months, following a standardized time schedule. In addition, M-CSF levels were measured in fracture hematoma and serum of 11 patients with bone fractures. M-CSF concentrations were measured by enzyme-linked immunosorbent assay (ELISA). Fracture hematoma contained significantly higher M-CSF concentrations compared to M-CSF concentrations in patient's serum. M-CSF levels in fracture hematoma and in patient's serum were both significantly higher than M-CSF concentrations measured in serum of healthy controls. Highly elevated M-CSF serum concentrations were found in patients with physiological fracture healing over the entire observation period. Significant differences in the M-CSF serum concentration between patients with normal fracture healing and patients with impaired fracture healing were not observed. This study indicates, for the first time, to our knowledge, a possible local and systemic involvement of M-CSF in humans during fracture healing.

Soft tissue and biomechanical challenges encountered with the management of distal tibia nonunions

A thoughtful treatment algorithm is required to optimally treat distal tibia nonunion. A healthy respect for the tenuous soft tissue envelope, compromised vascularity, and challenging mechanical environment is advisable. Achieving osseous union and improved functionality requires an individualized plan of care based on the personality of the nonunion and host. Attention must be focused on providing mechanical stability at the site of nonunion and providing biologic supplementation.

Reaming does not add significant time to intramedullary nailing of diaphyseal fractures of the tibia and femur

BACKGROUND

Reamed intramedullary nailing is the current gold standard for the treatment of diaphyseal fractures of the femur and tibia. Current concepts of orthopedic damage control surgery for patients with multiple injuries have placed an emphasis on appropriate surgical timing, limiting blood loss, and the duration of the initial operative procedure(s). Proponents of unreamed nailing have stated that reaming places polytraumatized patients "at risk," in part because it adds to the length of the surgical procedure and may exacerbate the severity of a patient's pulmonary injury. The purpose of this study was to determine how many minutes reaming actually takes and what percentage of operative time reaming comprises during intramedullary nailing of femoral and tibial shaft fractures.

METHODS

Intraoperative timing data were collected prospectively on a total of 52 patients with 54 fractures (21 femoral and 33 tibial) who underwent reamed intramedullary nailing of acute closed or open femoral or tibial shaft fractures over a 10-month period. Total operating room, surgical, and reaming times were collected.

RESULTS

The average reaming time for femur and tibia fractures was 6.9 minutes and 7 minutes, respectively. On average, reaming accounted for 4.9% of the surgical time and 3.2% of the total operating room time for femur fractures and 4.9% of the surgical time and 3.4% of the total operating room for tibia fractures.

CONCLUSION

Our results show that reaming comprises a small percentage of the operative time and the total time a patient spends in the operating room.

Bone morphogenetic proteins and tissue engineering: future directions

As long as bone repair and regeneration is considered as a complex clinical condition, the administration of more than one factor involved in fracture healing might be necessary. The effectiveness or not of bone morphogenetic proteins (BMPs) in association with other growth factors and with mesenchymal stem cells in bone regeneration for fracture healing and bone allograft integration is of great interest to the scientific community. In this study we point out possible future developments in BMPs, concerning research and clinical applications.

Paracrine effect of transplanted rib chondrocyte spheroids supports formation of secondary cartilage repair tissue

The study's objective was to investigate if transplanted chondrocyte or periosteal cell spheroids have influence on ingrowing bone marrow-derived cells in a novel cartilage repair approach in miniature pigs. Autologous rib chondrocytes or periosteal cells were cultured as spheroids and press-fitted into cavities that were milled into large, superficial chondral lesions of the patellar joint surface. Within the milled cavities, the subchondral bone plate was either penetrated or left intact (full-thickness or partial-thickness cavities). The transplantation of chondrocyte spheroids into full-thickness cavities induced the formation of additional secondary repair cartilage that exceeded the original volume of the transplanted spheroids. The resulting continuous tissue was rich in proteoglycans and stained positive for type II collagen. Cell labeling revealed that secondarily invading repair cells did not originate from transplanted spheroids, but rather from arroded bone marrow. However, secondary invasion of repair cells was less pronounced following transplantation of periosteal cells and absent in partial-thickness cavities. According to in vitro analyses, these observations could be ascribed to the ability of chondrocyte spheroids to secrete relevant amounts of bone morphogenetic protein-2, which was not detected for periosteal cells. Transplanted chondrocyte spheroids exert a dual function: they provide cells for the repair tissue and have a stimulatory paracrine activity, which promotes ingrowth and chondrogenesis of bone marrow-derived cells.

Intramedullary nailing for the treatment of aseptic femoral shaft non-unions after plating failure: effectiveness and timing

This retrospective, multicentre study aimed to evaluate reamed intramedullary nailing (IMN) for the treatment of 30 cases of aseptic femoral shaft non-union after plating failure. Following nailing, 29 non-unions had healed by a mean 7.93 months. In one case a hypertrophic non-union required renailing after 8 months, using a nail of greater diameter, and united within five further months. Healing times were not related to whether the fracture was open or closed, the type non-union or the type of fracture. The delay from the initial plating to intramedullary nailing had a statistically significant effect on healing time and final outcome. This treatment is cost effective and should be implemented as soon as the non-union is diagnosed.

Intraoperative reduction techniques for difficult femoral fractures

Successful intramedullary nailing of difficult femoral fractures is predicated on achieving and maintaining reduction before reaming and implant insertion. Closed and percutaneous strategies are emphasized which preserve fracture biology and encourage primary union. However, open techniques are sometimes necessary to avoid postoperative deformity.

Intramedullary nailing of the femur: current concepts concerning reaming

Intramedullary fixation has advanced to the standard of care for fractures of the femoral shaft. Current controversies center on whether to prepare the intramedullary canal by reaming, particularly in certain subsets of patients. As understanding of the local and systemic effects of reaming deepens, there is a role for maximizing the benefits of intramedullary preparation before nail fixation, while attempting to minimize the major disadvantages of this technique. Several treatment strategies have emerged to address the downsides of intramedullary reaming. The purpose of this review is to discuss the history and current knowledge of intramedullary reaming with respect to problems associated with its use and the evolution of treatment modalities and their clinical applicability for orthopaedic trauma care.

Growth factors in bone repair

The role of growth factors (GF) in bone repair is widely recognised, particularly for bone morphogenetic proteins (BMPs), fibroblast growth factor (FGF), insulin-like growth factors (IGFs), platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-beta) and vascular endothelial growth factor (VEGF). GF are usually stored in the extracellular matrix (ECM), but after injury are actively released by ECM, cells and platelets. In this paper, the use of different recombinant GF for bone repair stimulation is summarised in experimental research and clinical applications. Drug delivery systems, including carriers, cell or gene therapy, are needed to ensure a sustained local release of the factors, but efficacy and potential side effects of such systems require additional research prior to clinical applications. Current sources for delivery of a GF mixture into the site of bone repair are platelet gel and demineralised bone matrix. Nevertheless, the levels of GF in such preparations are affected by variability among donors and differences in preparation. Autogenous GF, produced by the patient himself during the bone repair process, potentially interfere with prosthetic devices or even have a role in implant loosening due to the periprosthetic tissue reaction. In conclusion, GF are key components of functional bone regeneration: screening of basic research results and controlled clinical trials are accelerating the development of GF in orthopaedic surgery.