Predicting fracture healing with blood biomarkers: the potential to assess patient risk of fracture nonunion.

Fracture non-union is a significant orthopaedic problem affecting a substantial number of patients yearly. Treatment of nonunions is devastating to patients and costly to the healthcare system. Unfortunately, the diagnosis of non-union is typically made in a reactionary fashion by an orthopaedic surgeon based on clinical assessment and radiographic features several months into treatment. For this reason, investigators have been trying to develop prediction algorithms; however, these have relied on population-based approaches and lack the predictive capability necessary to make individual treatment decisions. There is also a growing body of literature focussed on identifying blood biomarkers that are associated with non-union. This review describes the research that has been done in this area. Further studies of patient-centered, precision medicine approaches will likely improve fracture non-union diagnostic/prognostic capabilities.

Bioinformatic analysis and experimental identification of blood biomarkers for chronic nonunion.

BACKGROUND: Incomplete fracture healing may lead to chronic nonunion; thus, determining fracture healing is the primary issue in the clinical treatment. However, there are no validated early diagnostic biomarkers for assessing chronic nonunion. In this study, bioinformatics analysis combined with an experimental verification strategy was used to identify blood biomarkers for chronic nonunion. METHODS: First, differentially expressed genes in chronic nonunion were identified by microarray data analysis. Second, Dipsaci Radix (DR), a traditional Chinese medicine for fracture treatment, was used to screen the drug target genes. Third, the drug-disease network was determined, and biomarker genes were obtained. Finally, the potential blood biomarkers were verified by ELISA and qPCR methods. RESULTS: Fifty-five patients with open long bone fractures (39 healed and 16 nonunion) were enrolled in this study, and urgent surgical debridement and the severity of soft tissue injury had a significant effect on the prognosis of fracture. After the systems pharmacology analysis, six genes, including QPCT, CA1, LDHB, MMP9, UGCG, and HCAR2, were chosen for experimental validation. We found that all six genes in peripheral blood mononuclear cells (PBMCs) and serum were differentially expressed after injury, and five genes (QPCT, CA1, MMP9, UGCG, and HCAR2) were significantly lower in nonunion patients. Further, CA1, MMP9, and QPCT were markedly increased after DR treatment. CONCLUSION: CA1, MMP9, and QPCT are biomarkers of nonunion patients and DR treatment targets. However, HCAR2 and UGCG are biomarkers of nonunion patients but not DR treatment targets. Therefore, our findings may provide valuable information for nonunion diagnosis and DR treatment. TRIAL REGISTRATION: ISRCTN, ISRCTN13271153. Registered 05 April 2020-Retrospectively registered.

Inflammatory processes and elevated osteoclast activity chaperon atrophic non-union establishment in a murine model.

BACKGROUND: Delayed bone healing, especially in long bones poses one of the biggest problems in orthopeadic and reconstructive surgery and causes tremendous costs every year. There is a need for exploring the causes in order to find an adequate therapy. Earlier investigations of human scaphoid non-union revealed an elevated osteoclast activity, accompanied by upregulated levels of TGF-beta and RANKL. Interestingly, scaphoid non-union seemed to be well vascularized. METHODS: In the current study, we used a murine femur-defect model to study atrophic non unions over a time-course of 10 weeks. Different time points were chosen, to gather insights into the dynamic processes of non-union establishment. RESULTS: Histological analyses as well as western blots and qRT-PCR indicated enhanced osteoclast activity throughout the observation period, paralleled by elevated levels of TGF-beta, TNF-alpha, MMP9, MMP13 and RANKL, especially during the early phases of non-union establishment. Interestingly, elevated levels of these mediators decreased markedly over a period of 10 weeks, as inflammatory reaction during non-union establishment seemed to wear out. To our surprise, osteoblastogenesis seemed to be unaffected during early stages of non-union establishment. CONCLUSION: Taken together, we gained first insights into the establishment process of atrophic non unions, in which inflammatory processes accompanied by highly elevated osteoclast activity seem to play a leading role.

Defective Proliferation and Osteogenic Potential with Altered Immunoregulatory phenotype of Native Bone marrow-Multipotential Stromal Cells in Atrophic Fracture Non-Union.

Bone marrow-Multipotential stromal cells (BM-MSCs) are increasingly used to treat complicated fracture healing e.g., non-union. Though, the quality of these autologous cells is not well characterized. We aimed to evaluate bone healing-related capacities of non-union BM-MSCs. Iliac crest-BM was aspirated from long-bone fracture patients with normal healing (U) or non-united (NU). Uncultured (native) CD271highCD45low cells or passage-zero cultured BM-MSCs were analyzed for gene expression levels, and functional assays were conducted using culture-expanded BM-MSCs. Blood samples were analyzed for serum cytokine levels. Uncultured NU-CD271highCD45low cells significantly expressed fewer transcripts of growth factor receptors, EGFR, FGFR1, and FGRF2 than U cells. Significant fewer transcripts of alkaline phosphatase (ALPL), osteocalcin (BGLAP), osteonectin (SPARC) and osteopontin (SPP1) were detected in NU-CD271highCD45low cells. Additionally, immunoregulation-related markers were differentially expressed between NU- and U-CD271highCD45low cells. Interestingly, passage-zero NU BM-MSCs showed low expression of immunosuppressive mediators. However, culture-expanded NU and U BM-MSCs exhibited comparable proliferation, osteogenesis, and immunosuppression. Serum cytokine levels were found similar for NU and U groups. Collectively, native NU-BM-MSCs seemed to have low proliferative and osteogenic capacities; therefore, enhancing their quality should be considered for regenerative therapies. Further research on distorted immunoregulatory molecules expression in BM-MSCs could potentially benefit the prediction of complicated fracture healing.

Chemokine analysis as a novel diagnostic modality in the early prediction of the outcome of non-union therapy: a matched pair analysis.

BACKGROUND: Despite the regenerative capability of skeletal tissue fracture, non-union is common. Treatment of non-unions remains challenging, and early determination of the outcome is impossible. Chemokines play an important role in promoting the formation of new bone and remodeling existing bone. Despite their importance regarding the regulation of bone biology, the potential of chemokines as biological markers reflecting osseous regeneration is unknown. The purpose of this study was to determine (1) if serum chemokine expression levels correlate with the outcome of non-union surgery and (2) if chemokine expression analysis can be used to identify patients at risk for treatment failure. METHODS: Non-union patients receiving surgical therapy in our institution between March 2012 and March 2014 were prospectively enrolled in a clinical observer study. Regular clinical and radiological follow-up was conducted for 12 months including collection of blood during the first 12 weeks. Based on the outcome, patients were declared as responders or non-responders to the therapy. To minimize biases, patients were matched (age, sex, body mass index (BMI)) and two groups of patients could be formed: responders (R, n = 10) and non-responders (NR, n = 10). Serum chemokine expression (CCL-2, CCL-3, CCL-4, CXCL-10, CCL-11, and interferon gamma (IFN-γ)) was analyzed using Luminex assays. Data was compared and correlated to the outcome. RESULTS: CCL-3 expression in NR was significantly higher during the course of the study compared to R (p = 0.002), and the expression pattern of CCL-4 correlated with CCL-3 in both groups (NR: p < 0.001 and r = 0.63). IFN-γ expression in NR was continuously higher than in R (p < 0.001), and utilization of CCL-3 and IFN-γ serum expression levels 2 weeks after the treatment resulted in a predictive model that had an AUC of 0.92 (CI 0.74-1.00). CONCLUSION: Serum chemokine expression analysis over time is a valid and promising diagnostic tool. The chemokine expression pattern correlates with the outcome of the Masquelet therapy of lower limb non-unions. Utilization of the serum analysis of CCL-3 and IFN-γ 2 weeks after the treatment resulted in an early predictive value regarding the differentiation between patients that are likely to heal and those that are prone to high risk of treatment failure.

Local transplantation of bone marrow concentrated granulocytes precursors can cure without antibiotics infected nonunion of polytraumatic patients in absence of bone defect.

PURPOSE: Infected, long bone non-unions present a significant clinical challenge. New and alternative therapies are needed to address this problem. The purposes of this study were to compare the number of circulating granulocyte-macrophage colony-forming units (CFU-GM) in the peripheral blood of polytraumatic patients with infected tibial non-unions and in the peripheral blood of control patients with the hypothesis that their number was decreased in polytraumatic patients; and to treat their infection without antibiotics and with local transplantation of bone marrow concentrated granulocytes precursors. METHODS: Thirty (18 atrophic and 12 hyperthrophic ) infected tibial non-unions (without bone defect) that occurred after open fractures in polytraumatic patients were treated without antibiotics and with percutaneous injection of autologous bone marrow concentrate (BMC) containing granulocytes precursors (CFU-GM). CFU-GM progenitors were assessed in the bone marrow aspirate, peripheral blood, and fracture site of these patients. The number of these progenitors was compared with the CFU-GM progenitors of control patient samples (healthy donors matched for age and gender). Outcome measures were: timing of union, callus formation (radiographs and CT scan), and recurrence of clinical infection. RESULTS: As compared to control patients, the number of CFU GM derived colonies was lower at peripheral blood in patients with infected nonunions. The bone marrow graft injected in nonunions contained after concentration 42 621 ± 20 350 CFU-GM-derived colonies/cc. Healing and cure of infection was observed at six months for 25 patients and at one year follow up for 30 patients. At the median ten year follow-up (range: 5 to 15), only one patient had clinical recurrent infection after healing (between 6 months and last follow-up). CONCLUSION: The peripheral blood of these polytraumatic patients with infected nonunions had a remarkable decrease in CFU-GM-derived colonies as compared with normal controls. Local transplantation of concentrated CFU-GM-derived colonies aspirated from bone marrow allowed cure of infection and healing without antibiotics.

Quantification of TGF-ß1, PDGF and IGF-1 cytokine expression after fracture treatment vs. non-union therapy via masquelet.

INTRODUCTION: Biochemical processes during bone regeneration can be analysed via quantification of peripheral serum cytokine levels. To date, serum levels of cytokines in patients treated with masquelet technique and patients with normal bone healing have not been compared. This comparison is supposed to deliver novel insights into the process of bone regeneration. Our aim was to validate this established method in the monitoring of bone regeneration after non-union treatment in masquelet technique. MATERIALS AND METHODS: Between 04/2008 and 01/2014 three groups were recruited: G1 (10 patients) with long bone non-unions, treated successfully with masquelet therapy, G2 (6 patients) with unsuccessful masquelet therapy and G3 (10 patients) with long bone fractures and normal bone healing. Peripheral blood samples were collected over a period of six months following a standardised time pattern in combination with clinical and radiologic follow up. TGF-ß1, PDGF-AB and IGF-1 were measured using commercially available immunoassays. RESULTS: TGF-ß1 levels in G1 and G2 demonstrated a parallel and lower overall concentration over time compared to G3. G3 showed a significant TGF-ß1 peak 2 weeks after surgery compared to G1 (p=0.0054). PDGF-AB concentrations were always lower in G2 than in G1 and G3. G3 peaked at week 2 with a significant higher value than in G2 (p=0.0177). IGF-1 showed lower overall serum concentrations in G2 than in G1 and G3. G1 had a peak level during the fourth week of follow-up. Compared to G2 this peak was significant (p=0.0015). CONCLUSIONS: This study shows that successful bone regeneration via masquelet technique only partially imitates cytokine expression of physiological bone healing. High expressions of IGF-1 correspond to a successful masquelet therapy while TGF-ß seems to play a minor role. These results assume that objective analysis of an effective non-union therapy with cytokine expression analysis is possible even with a small number of patients.

Effect of the blood HbA1c level on surgical treatment outcomes of diabetics with ankle fractures.

OBJECTIVE: To investigate whether blood haemoglobin A 1c (HbA1c) levels was predicative of diabetic patients' responsiveness to surgical treatment of ankle fractures. METHODS: The relationship between blood HbA1c levels and surgical treatment outcomes of 21 diabetic patients undergoing open reduction internal fixation (ORIF) for ankle fractures was analyzed with Pearson correlation testing and t testing. All patients were treated with ORIF using standard surgical techniques. Treatment outcomes were defined using radiological outcome, the American Orthopaedic Foot and Ankle Score (AOFAS) ankle-hindfoot scale score, surgical revision rate, and complication rate. RESULTS: HbA1c levels were found to have a statistically significant correlation with poor radiological outcomes (r = 0.547) and AOFAS ankle-hindfoot scores (r = -0.592). Additionally, though rates of poor radiological outcome, revision, and complication were high in the diabetic population as a whole, these rates were considerably higher among individuals with elevated HbA1c (≥6.5%) and considerably lower among individuals with lower HbA1c (<6.5%) levels. CONCLUSION: Blood HbA1c levels appear to be predictive of risk and complication rates in the surgical treatment outcomes of diabetic patients with ankle fractures.

Decreased pool of mesenchymal stem cells is associated with altered chemokines serum levels in atrophic nonunion fractures.

Nonunion fractures can cause severe dysfunction and are often difficult to treat mainly due to a poor understanding of their physiopathology. Although many aspects of impaired fracture healing have been extensively studied, little is known about the cellular and molecular mechanisms leading to atrophic nonunion. Therefore, the aim of the present study was to assess the pools and biological functions of bone marrow-derived mesenchymal stem cells (hMSCs) and circulating endothelial progenitor cells (EPCs) in atrophic nonunion patients compared to healthy subjects, and the systemic levels of growth factors involved in the recruitment, proliferation and differentiation of these cells. In nonunions, the pool of hMSCs was decreased and their proliferation delayed. However, once committed, hMSCs from nonunions were able to proliferate, differentiate into osteoblastic cells and mineralize in vitro as efficiently as hMSCs from healthy subjects. In parallel, we found altered serum levels of chemokines and growth factors involved in the chemotaxis and proliferation of hMSCs such as leptin, interleukin-6 (IL-6) and its soluble receptor, platelet-derived growth factor-BB (PDGF-BB), stem cell factor (SCF) and insulin-like growth factor-1 (IGF-1). Moreover, we showed that the number of EPCs and their regulating growth factors were not affected in nonunion patients. If nonunion is generally attributed to a vascular defect, our results also support a role for a systemic mesenchymal and osteogenic cell pool defect that might be related to alterations in systemic levels of factors implicated in their chemotaxis and proliferation.

Is the expression of Transforming Growth Factor-Beta1 after fracture of long bones solely influenced by the healing process?

PURPOSE: Circulating TGF-ß1 levels were found to be a predictor of delayed bone healing and non-union. We therefore aimed to investigate some factors that can influence the expression of TGF-ß1. The correlation between the expression of TGF-ß1 and the different socio-demographic parameters was analysed. METHODS: Fifty-one patients with long bone fractures were included in the study and divided into different groups according to their age, gender, cigarette smoking status, diabetes mellitus and regular alcohol intake. TGF-ß1 levels were analysed in patient's serum and different groups were retrospectively compared. RESULTS: Significantly lower TFG-ß1 serum concentrations were observed in non-smokers compared to smokers at week 8 after surgery. Significantly higher concentrations were found in male patients compared to females at week 24. Younger patients had significantly higher concentrations at week 24 after surgery compared to older patients. Concentrations were significantly higher in patients without diabetes compared to those with diabetes at six weeks after surgery. Patients with chronic alcohol abuse had significantly higher concentrations compared to those patients without chronic alcohol abuse. CONCLUSION: TGF-ß1 serum concentrations vary depending upon smoking status, age, gender, diabetes mellitus and chronic alcohol abuse at different times and therefore do not seem to be a reliable predictive marker as a single-point-in-time measurement for fracture healing.

Strongly enhanced levels of sclerostin during human fracture healing.

Sclerostin (SOST), an antagonist of Wnt signaling, is an important negative regulator of bone formation. However, no data on the role of SOST in the human fracture healing have been published so far. This study addressed this issue. Seventy-five patients with long bone fractures were included into the study and divided in two groups. The first group contained 69 patients with normal fracture healing. Six patients with impaired fracture healing formed the second group. Thirty-four volunteers donated blood samples as control. Serum samples were collected over a period of 1 year following a standardized time schedule. In addition, SOST levels were measured in fracture hematoma and serum of 16 patients with bone fractures. Fracture hematoma contained significantly higher SOST concentrations compared to patient's serum. SOST levels in fracture hematoma and in patient's serum were both significantly higher than in the serum of controls. Highly elevated SOST serum concentrations were found in patients with physiological fracture healing. SOST levels were decreased in patients with impaired fracture healing. However, this difference was not statistically significant. This is the first study to provide evidence of strongly enhanced SOST levels in patients with bone fracture. The results indicate local and systemic involvement of SOST in humans during fracture healing.

VEGF serum concentrations in patients with long bone fractures: a comparison between impaired and normal fracture healing.

Vascular endothelial growth factor (VEGF) plays an important role in the bone repair process as a potent mediator of angiogenesis and it influences directly osteoblast differentiation. Inhibiting VEGF suppresses angiogenesis and callus mineralization in animals. However, no data exist so far on systemic expression of VEGF with regard to delayed or failed fracture healing in humans. One hundred fourteen patients with long bone fractures were included in the study. Serum samples were collected over a period of 6 months following a standardized time schedule. VEGF serum concentrations were measured. Patients were assigned to one of two groups according to their course of fracture healing. The first group contained 103 patients with physiological fracture healing. Eleven patients with delayed or nonunions formed the second group of the study. In addition, 33 healthy volunteers served as controls. An increase of VEGF serum concentration within the first 2 weeks after fracture in both groups with a following decrease within 6 months after trauma was observed. Serum VEGF concentrations in patients with impaired fracture healing were higher compared to the patients with physiological healing during the entire observation period. However, statistically significant differences were not observed at any time point between both groups. VEGF concentrations in both groups were significantly higher than those in controls. The present results show significantly elevated serum concentrations of VEGF in patients after fracture of long bones especially at the initial healing phase, indicating the importance of VEGF in the process of fracture healing in humans.

The systemic angiogenic response during bone healing.

INTRODUCTION: Angiogenesis is known to be a critical and closely regulated step during bone formation and fracture healing driven by a complex interaction of various cytokines. Delays in bone healing or even nonunion might therefore be associated with altered concentrations of specific angiogenic factors. These alterations might in turn be reflected by changes in serum concentrations. METHOD: To determine physiological time courses of angiogenic cytokines during fracture healing as well as possible changes associated with failed consolidation, we prospectively collected serum samples from patients who had sustained surgical treatment for a long bone fracture. Fifteen patients without fracture healing 4 months after surgery (nonunion group) were matched to a collective of 15 patients with successful healing (union group). Serum concentrations of angiogenin (ANG), angiopoietin 2 (Ang-2), basic fibroblast growth factor (bFGF), platelet derived growth factor AB (PDGF-AB), pleiotrophin (PTN) and vascular endothelial growth factor (VEGF) were measured using enzyme linked immunosorbent assays over a period of 24 weeks. RESULTS: Compared to reference values of healthy uninjured controls serum concentrations of VEGF, bFGF and PDGF were increased in both groups. Peak concentrations of these cytokines were reached during early fracture healing. Serum concentrations of bFGF and PDGF-AB were significantly higher in the union group at 2 and 4 weeks after the injury when compared to the nonunion group. Serum concentrations of ANG and Ang-2 declined steadily from the first measurement in normal healing fractures, while no significant changes over time could be detected for serum concentrations of these factures in nonunion patients. PTN serum levels increased asymptotically over the entire investigation in timely fracture healing while no such increase could be detected during delayed healing. CONCLUSION: We conclude that fracture healing in human subjects is accompanied by distinct changes in systemic levels of specific angiogenic factors. Significant alterations of these physiologic changes in patients developing a fracture nonunion over time could be detected as early as 2 (bFGF) and 4 weeks (PDGF-AB) after initial trauma surgery.

Evaluation of serum biochemical markers of bone metabolism for early diagnosis of nonunion and infected nonunion fractures in rabbits.

OBJECTIVE: To evaluate the use of serum concentrations of biochemical markers of bone metabolism (osteocalcin [OC], bone-specific alkaline phosphatase [BS-ALP], and deoxypyridinoline [DPYR]) to compare healing in infected versus noninfected fractures and in fractures with normal repair versus delayed (nonunion) repair in rabbits. ANIMALS: 32 female 9- to 10-month-old New Zealand White rabbits. PROCEDURE: A femoral fracture defect was made in each rabbit. Rabbits were assigned to the following groups: the bone morphogenetic-2 gene treatment group with either noninfected nonunion or infected (ie, inoculation of defects with Staphylococcus aureus) nonunion fractures or the luciferase (control) gene treatment group with either noninfected nonunion or infected nonunion fractures. Serum samples were obtained before surgery (time 0) and 4, 8, 12, and 16 weeks after surgery. Callus formation and lysis grades were evaluated radiographically at 16 weeks. RESULTS: Serum OC and BS-ALP concentrations decreased from time 0 at 4 weeks, peaked at 8 weeks, and then decreased. Serum DPYR concentration peaked at 4 weeks and then decreased, independent of gene treatment group or fracture infection status. Compared with rabbits with noninfected fractures, those with infected fractures had lower serum OC and BS-ALP concentrations at 4 weeks, higher serum OC concentrations at 16 weeks, and higher serum DPYR concentrations at 4, 8, and 16 weeks. Combined serum OC, BS-ALP, and DPYR concentrations provided an accuracy of 96% for prediction of fracture infection status at 4 weeks. CONCLUSIONS AND CLINICAL RELEVANCE: Measurement of multiple serum biochemical markers of bone metabolism could be useful for clinical evaluation of fracture healing and early diagnosis of osteomyelitis.

The vascularity of atrophic non-unions.

The objective of this study was to assess the vascularity of atrophic non-unions using an experimental animal model. Twenty skeletally mature female rabbits were randomly divided into control and experimental groups that were killed 1, 8, or 16 weeks after surgery. The experimental groups underwent surgery to induce an atrophic non-union whereas the control groups underwent a similar operation but which resulted in union. Using immunocytochemical techniques blood vessels were identified in histological sections obtained from the osteotomy site. The concentration of the vessels within the osteotomy gaps was measured, as was the serum concentration of an important angiogenic factor: endothelial cell-stimulating angiogenesis factor (ESAF). The results demonstrated a significant difference between the control and the experimental groups in the concentration of vessels within the gap at 1 week but there was no significant difference between those groups at 8 weeks. There were no significant differences in the ESAF concentration between the groups at any time points. We concluded that established atrophic non-unions can be well vascularised and that measurements of serum levels of ESAF could not distinguish between those osteotomies that would unite and those that would progress to non-union.

Blood levels of active metabolites of vitamin D3 in fracture repair in humans. A preliminary report.

Blood levels of the active metabolites of vitamin D3, 25-hydroxycholecalciferol [25(OH)D3], 1,25-dihydroxycholecalciferol [1,25(OH)2D3] and 24,25-dihydroxycholecalciferol [24,25(OH)2D3] were determined in seven patients. Two subjects suffered from delayed union of tibial fractures; one showed a delayed union after a proximal tibial osteotomy; one patient suffered from bilateral femoral neck fractures, of which one failed to unite and the other united late; two patients had multiple fractures that united normally; and one patient exhibited staged bilateral femoral neck fractures whose occurrence was separated by a short interval and which united without undue delay. The blood levels of 25(OH)D3 were within the normal range. A relative decrease in 24,25(OH)2D3 values was noted in all patients, whereas in three subjects the decrease was absolute, to non-detectable levels. A decrease in 1,25(OH)2D3 levels was noted in only two patients. We postulate that these changes reflect the consumption of these metabolites during healing at the fracture site.