[Therapeutic outcome in tibial pseudarthrosis: bone morphogenetic protein 7 (BMP-7) versus autologous bone grafting for tibial fractures]

Cell-free and cytokine-free self-assembling peptide hydrogel-polycaprolactone composite scaffolds for segmental bone defects

Segmental bone defects over the self-healing threshold are a major challenge for orthopedics. Despite the advancements in clinical practice, traditional tissue engineering methods are limited by the addition of heterogeneous cells and cytokines, leading to carcinoma or other adverse effects. Here, we present a cell-free and cytokine-free strategy using an ECM-mimetic self-assembling peptide hydrogel (SAPH)- polycaprolactone (PCL) composite scaffold. The hydrophilic SAPH endows the rigid PCL scaffold with excellent biocompatibility and preference for osteogenesis induction. The autologous cells around the bone defect site immediately grew, proliferated, and secreted ECM and cytokines after contacting the implanted SAPH-PCL composite scaffold, and the bone repair of rabbit ulnar segmental bone defect was achieved in just six months. Quantitative proteomic analysis reveals that the SAPH-PCL composite scaffold accelerates osteoblastogenesis, osteoclastogenesis, and angiogenesis with moderate immune responses and negligible effects on pathological fibrosis. These findings have important implications for the potential clinical applications of the SAPH-PCL composite scaffold in patients with segmental bone defects and identify the mechanisms of action for accelerated segmental bone defect repair.

The role of Platelet Rich Plasma and other orthobiologics in bone healing and fracture management: A systematic review

BACKGROUND

Treatment of large bone defects and fracture healing complications (delayed and non-union) presents a substantial challenge for orthopaedic surgeons. Given that bone healing requires mechanical stability as well as a favourable biological microenvironment, orthobiologics such as Platelet-Rich Plasma (PRP) may have a significant clinical role to play.

AIMS

To perform a systematic review of the available literature to assess the clinical effect of PRP, with or without other orthobiologics, on bone healing.

METHOD

Two independent reviewers performed the literature search based on the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Clinical studies of any evidence, assessing effect of PRP with or without other orthobiologics on bone healing, were included. A qualitative analysis was carried out on the clinical and radiological outcomes reported.

RESULT

27 articles with 1631 patients (mean age = 43.56, 57.1% male, mean follow-up = 17.27 months) were included in the qualitative. Of the 27 studies, 13 dealt with fracture complications (delayed or non-unions), 7 with acute fracture healing, 4 with tibial osteotomies and lengthening procedures and 3 with lumbar spine pathology. 18/27 studies showed a clinical benefit of PRP, 8/27 showed no significant effect, and 1/27 showed a worse outcome with PRP.

CONCLUSION

Our review suggests PRP may play a clinical role in bone healing but further randomised controlled trials (RCTs) using standardised outcomes should be performed to establish its efficacy.

Insulin-Like Growth Factor-1 as a Possible Alternative to Bone Morphogenetic Protein-7 to Induce Osteogenic Differentiation of Human Mesenchymal Stem Cells in Vitro

Growth factors and mesenchymal stem cells (MSC) support consolidation of bone defects. Bone Morphogenetic Protein-7 (BMP-7) has been used clinically and experimentally, but the outcomes remain controversial. Increased systemic expression of Insulin-like Growth Factor-1 (IGF-1) significantly correlates with successful regeneration of bone healing disorders, making IGF-1 a promising alternative to BMP-7. There is no experimental data comparing the osteoinductive potential of IGF-1 and BMP-7. Therefore, in this study, the influence of IGF-1 and BMP-7 in different concentrations on the osteogenic differentiation of two human MSC-subtypes, isolated from reaming debris (RMSC) and iliac crest bone marrow (BMSC) has been assessed. A more sensitive reaction of BMSC towards stimulation with IGF-1 in concentrations of 400–800 ng/mL was found, leading to a significantly higher degree of osteogenic differentiation compared to stimulation with BMP-7. RMSC react more sensitively to stimulation with BMP-7 compared to BMSC. Lower concentrations of IGF-1 were necessary to significantly increase osteogenic differentiation of RMSC and BMSC compared to BMP-7. Therefore, IGF-1 should be considered as a valuable option to improve osteogenic differentiation of MSC and merits further experimental consideration. The MSC subtype and method of differentiation factor application also have to be considered, as they affect the outcome of osteogenic differentiation.

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.

Mesenchymal stem cells from reaming material possess high osteogenic potential and react sensitively to bone morphogenetic protein 7

BACKGROUND

Femoral material harvested using the Reamer-Irrigator-Aspirator (RIA) system is an alternative source for autogenous bone material in the treatment of non-unions, especially in combination with bone morphogenetic proteins (BMP). So far, there is no in vivo evidence of BMP-7 interacting with mesenchymal stem cells (MSCs) from RIA material (RIA-MSCs) and iliac crest autogenous bone (BMSCs). The aim of this study was to compare their osteogenic potential when stimulated with BMP-7 in vivo.

METHODS

RIA-MSC and BMSC from 11 donors were isolated and the character of MSCs was investigated in vitro. Constructs consisting of MSC, β-tricalcium phosphate and 2 concentrations of BMP-7 (0.1 µg/mL and 1 µg/mL) were implanted in mice for 8 weeks. Bone formation in the constructs was analyzed quantitatively and qualitatively.

RESULTS

All cell populations used were determined to be MSCs. The qualitative in vivo analysis showed formation of bone tissue. With regard to quantity, bone formation was significantly higher in RIA constructs without or with stimulation with 0.1 µg/mL BMP-7, compared with BMSC constructs. We found no significant differences between constructs stimulated with 1 µg/mL BMP-7. In the RIA group, we observed a significant increase in bone formation after stimulation with 0.1 µg/mL BMP-7. No significant change could be found using a higher concentration. In the BMSC group, we detected a significant increase when using 0.1 µg/mL and 1 µg/mL BMP-7.

CONCLUSIONS

RIA material is a source of MSCs with high osteogenic potential. Our results showed that stimulation by BMP-7 leads to an increased osteogenic potential of MSCs. In this respect, RIA-MSCs reacted more sensitively than BMSCs.

The treatment of atrophic, recalcitrant long-bone nonunion in the upper extremity with human recombinant bone morphogenetic protein-7 (rhBMP-7) and plate fixation: A retrospective review

INTRODUCTION

Recombinant Human Bone Morphogenetic Protein-7 (rhBMP-7) has been shown to promote fracture healing in both clinical studies and basic science models, however, there is little information from large-scale studies of its use for human nonunion. The purpose of this study was to determine the safety and efficacy of rhBMP-7 in the treatment of atrophic human long-bone nonunions in the upper extremity.

PATIENTS AND METHODS

This was a single center, retrospective, longitudinal cohort study of patients treated with compression plating and the application of rhBMP-7 in isolation to a long-bone nonunion. Patients over sixteen years of age with an atrophic, aseptic nonunion of a humerus, radius, ulna or clavicle were eligible for inclusion.

RESULTS

We identified seventy eligible patients who were treated with rhBMP-7 for a long-bone nonunion between July 1997 and April 2012. The mean age of the patients at the time of treatment with rhBMP-7 was 50.7 years (range, 20-92 years). Five patients were lost to follow-up prior to definitive clinical or radiographic union. During the one-year post-operative period fifty-six patients had achieved union and two patients developed a stable fibrous union after the index procedure. Two patients had early implant failure and five patients had persistent nonunion. Thus, the union rate following initial surgery was 89% (58/65) and four of the five nonunion patients went on to heal following revision open reduction and internal fixation.

CONCLUSION

We found that the application of rhBMP-7 for upper extremity nonunion was an effective method (89% union rate) of treating this challenging pathology. Additionally, if not initially successful, further reconstruction was not compromised by rhBMP-7 use.

Treatment of nonunions in fractures of the humeral shaft according to the Diamond Concept

Methods

Between 2005 and 2012, 50 patients (23 female, 27 male) with nonunion of the humeral shaft were included in this retrospective study. The mean age was 51.3 years (14 to 88). The patients had a mean of 1.5 prior operations (sd 1.2;1 to 8). All patients were assessed according to a specific risk score in order to devise an optimal and individual therapy plan consistent with the Diamond Concept. In 32 cases (64%), a change in the osteosynthesis to an angular stable locking compression plate was performed. According to the individual risk an additional bone graft and/or bone morphogenetic protein-7 (BMP-7) were applied.

Results

A successful consolidation of the nonunion was observed in 37 cases (80.4%) with a median healing time of six months (IQR 6). Younger patients showed significantly better consolidation. Four patients were lost to follow-up. Revision was necessary in a total of eight (16%) cases. In the initial treatment, intramedullary nailing was most common.

Discussion

The use of locking compression plates in combination with autologous cancellous bone graft has been shown to be a safe and effective treatment. In more complex cases, the use of the Masquelet technique and BMP-7 may be indicated at the first revision operation. Take home message: Our results suggest the Diamond Concept is a successful treatment strategy for nonunions of the humeral shaft. Cite this article: Bone Joint J 2016;98-B:81–7.

Failed treatment of long bone nonunions with low intensity pulsed ultrasound

INTRODUCTION

The use of low intensity pulsed ultrasound (LIPUS) in the treatment of nonunions is still controversial. The present study is concerned with whether this procedure has a clinical use and which cofactors influence its therapeutic results.

METHODS

In this prospective, single institution, observational study, data from October 2010 to October 2013 from 61 nonunions in 60 patients treated with EXOGEN(®) LIPUS therapy were analysed. The average age was 45.4 ± 9.81 (18-63) years. Treatment was primarily done on long bones of the lower extremity (75.4 %). All 61 nonunions were examined after treatment, and the rate of healing as well as functional and subjective results were evaluated. Based on clinical and radiological findings, patients were divided into two groups: G1-successful treatment; and G2-unsuccessful treatment. Groups were compared to one another to identify possible factors influencing treatment.

RESULTS

Twenty (32.8 %) patients showed bone consolidation with an average time of healing of 5.3 (2-7) months. In patients without successful treatment, who underwent revision surgery instead, full weight bearing took on average 3.7 months longer, and they were able to return to work 6.8 months later. Most of the treated patients (70.5 %) reported no improvement in pain. In G2, 12 (29.3 %) patients suffered in their previous history from osteitis; in G1 there were only two patients (10 %) (p = 0.012). There were further significant differences in the age of the fracture, the type of osteosynthesis, the gap size, as well as the NUSS score.

CONCLUSION

Despite patients being chosen strictly according to EXOGEN(®) indications, only a small number of patients with nonunions who underwent LIPUS therapy experienced successful treatment (32.8 %). Overall, its use resulted in a clear delay in the time of treatment, so that according to our results, the use of LIPUS should be seen critically in long bone nonunions and use should be made on a case-by-case basis.

RIA fractions contain mesenchymal stroma cells with high osteogenic potency

INTRODUCTION

The gold standard for treatment of non-union is the transplantation of autologous bone from iliac crest. As an alternative, material can be harvested by femoral reaming with the Reamer-Irrigator-Aspirator(®) (RIA)-System. This material might be a source for human mesenchymal stroma cells (MSCs) with osteogenic potency. The aim of this study was the characterisation of cells harvested with the RIA system and the comparison of their properties with cells isolated from bone marrow ("BM") and fat tissue ("adipose"). The RIA material was separated into the liquid aspiration fraction ("liquid") and the solid RIA fraction. From the solid RIA fraction the cells were cultured either directly ("native") or after collagenase digestion and filtration ("filtrate"). Stem cell characteristics were analysed and the osteogenic potential was investigated in vitro and in vivo.

MATERIALS & METHODS

Fat tissue and bone marrow were harvested from nine patients (three women, six males, with a mean of 48.1 years) with atrophic non-union RIA material. The cells were isolated and characterised by flow cytometry, three lineage differentiation capacities and colony-forming unit fibroblast assay. Gene expression profiles were performed and osteogenic differentiation in vivo was analysed.

RESULTS

All three RIA fractions contained mesenchymal stromal cells (MSCs) as demonstrated by CFU-F assay, three linage differentiation and surface marker analysis. The RIA-MSCs exhibited a significantly higher osteogenic potential in vitro compared to adipose-MSCs, whereas no difference was seen compared to BM-MSCs. Quantitative RT-PCR analysis revealed an expression of osteogenic markers in all isolated cells. The implantation of MSCs with β-TCP scaffolds into the mice muscle showed significantly higher bone formation for the filtrate RIA-MSC, native RIA-MSC and BM-MSC groups compared to the adipose-MSC group. The filtrate RIA-MSCs formed twice as much new bone in vivo compared to BM-MSCs.

CONCLUSION

The present study showed high potency of cells isolated by reaming. Even in the irrigation fluid, which is normally discarded, cells with the characteristics of stromal stem cells were isolated. In comparison to adipose-MSCs and BM-MSCs, the RIA-MSCs showed a similar or even better osteogenic potential in vitro and in vivo and this supports their usability in orthopaedic surgery.

Clinical effectiveness of Osigraft in long-bones non-unions

Current evidence, based primarily on case series, suggest that the eptotermin alfa (recombinant bone morphogenetic protein-7 (rhBM-7)), which is commercialized as Osigraft with an indication for tibial non-union, used in monotherapy or polytherapy, is a safe and effective therapy for long bones non-unions of lower and upper limbs. No previous study has compared the safety and the efficacy of Osigraft and the "gold standard" treatment for recalcitrant long-bones non-union, autologous bone graft (ABG). This study aims to compare the effectiveness of Osigraft and ABG in the treatment of post-traumatic, persistent long bone non-unions. In particular, the present study will focus exclusively on complex persistent non-unions, excluding simpler cases, in which it is likely that a simple revision of the osteosynthesis will be sufficient to promote union, and extremely severe cases in which there is an indication for amputation and prosthesis. The study addresses the following research question: 1. Is the effectiveness of eptotermin alfa comparable to that of ABG in the treatment of complex long bone non-unions? 2. Are there significant differences in the prevalence of adverse events between patients treated with eptotermin alfa and those treated with ABG? The study is an observational, retrospective study, located in one Experimental Recruiting Center (Ospedale Universitario G. PINI - Milano). The study was conducted with ethics approval and according with the existing Italian law. Demographic and clinical data were collected from patients Clinical Medical Records and other existing documentation, through a web based eCRF. The treatment (surgery with Osigraft or ABG) effectiveness was evaluated comparing the number of success cases (primary endpoint) and the length for clinical and radiological healing (secondary end-points). The treatment safety was evaluating comparing the prevalence of Adverse Events. Osigraft was demonstrated to be statistically equivalent to ABG with respect to the primary and secondary end point of surgical success. The treatment success was statistically comparable across all the anatomical regions considered, both in patients treated with Osigraft and in patients treated with ABG. The use of Osigraft when compared to autograft was associated with statistically lower intraoperative blood loss and shorter operative times. In addition patients treated with Osigraft developed statistically less peri-operative and late onset adverse events, compared to ABG. The difference was substantially due to the occurrence of pain at donor site in patients treated with ABG.

Treatment of atrophic tibia non-unions according to 'diamond concept': Results of one- and two-step treatment

BACKGROUND

The successful treatment of atrophic tibia non-unions and tibia non-unions with large bone defects or infections is a major challenge in orthopedic and trauma surgery. This article evaluates the use of the 'diamond concept' using a one-step or two-step procedure according to 'Masquelet technique' in the treatment of atrophic tibia non-unions.

METHODS

Between February 2010 and March 2014, 102 patients with atrophic non-unions were treated according to the 'diamond concept' in our center. Ninety-nine were available for follow-up. Forty-nine received a one-step treatment (Group 1, G1) and 50 patients received a two-step treatment according to the 'Masquelet technique' (Group 2, G2). Clinical and radiological parameters were measured preoperatively as well as 4, 6, and 12 weeks and 6 and 12 months postoperatively. In order to evaluate the subjective health of patients, we used the SF-12 questionnaire. Data analysis was performed one year after treatment.

RESULTS

The rate of consolidation in G1 was 84% and 80% in G2. The time to heal in G2 was 8.6 ± 2.9 months, which is significantly longer than in G1 being 6.9 ± 3.1 months. In comparison patients in G1/G2 had an average of 3.2/6.7 previous major surgeries. In G1, 4 of 8 patients who did not heal successfully showed positive intraoperative cultures. In G2, 26 patients (52%) initially presented with positive cultures. The results of the SF-12 questionnaire improved in both groups during the postoperative follow-up, but showed no significant differences between groups. In 29 patients a gentamycin-coated nail was used for reosteosynthesis. These patients showed by trend a lower rate of complications at a higher rate of consolidation.

CONCLUSIONS

Our study showed that the 'diamond concept' is a suitable method for safely and effectively treating non-unions with large defects or infections. The use of an antibiotic-coated nail provides a therapeutic benefit. For large bone defects of infected non-unions the two-step procedure after Masquelet is an efficient way to eradicate the infection and treat the bone defect successfully.

Recent biological trends in management of fracture non-union

Bone regeneration is a complex, well-orchestrated physiological process of bone formation, which can be seen during normal fracture healing, and is involved in continuous remodelling throughout adult life. Currently, there is a plethora of different strategies to augment the impaired or "insufficient" bone-regeneration process, including the "gold standard" autologous bone graft, free fibula vascularised graft, allograft implantation, and use of growth factors, osteoconductive scaffolds, osteoprogenitor cells and distraction osteogenesis. Improved "local" strategies in terms of tissue engineering and gene therapy, or even "systemic" enhancement of bone repair, are under intense investigation, in an effort to overcome the limitations of the current methods, to produce bone-graft substitutes with biomechanical properties that are as identical to normal bone as possible, to accelerate the overall regeneration process, or even to address systemic conditions, such as skeletal disorders and osteoporosis. An improved understanding of the molecular and cellular events that occur during bone repair and remodeling has led to the development of biologic agents that can augment the biological microenvironment and enhance bone repair. Orthobiologics, including stem cells, osteoinductive growth factors, osteoconductive matrices, and anabolic agents, are available clinically for accelerating fracture repair and treatment of compromised bone repair situations like delayed unions and nonunions. A lack of standardized outcome measures for comparison of biologic agents in clinical fracture repair trials, frequent off-label use, and a limited understanding of the biological activity of these agents at the bone repair site have limited their efficacy in clinical applications.

Can we achieve bone healing using the diamond concept without bone grafting for recalcitrant tibial nonunions?

The purpose of this study was to evaluate the efficacy and safety of a combination of recombinant human bone morphogenetic protein 7 (rhBMP-7) and resorbable calcium phosphate bone substitute (rCPBS) as a salvage solution for recalcitrant tibial fracture nonunions. Twenty consecutive patients, 16 male and four female, with a mean age of 46.8±15.7 years (21-78) and a mean body mass index (BMI) of 24.2±5.3kgm(-2) (21.5-28.5), suffering from 20 recalcitrant tibial fracture nonunions were included. The mean number of operations performed prior to the procedure was 3.3, with homolateral iliac crest bone grafts being used for all of the patients. All patients were treated with a procedure including debridement and decortications of the bone ends, nonunion fixation with a locking plate, and filling of the bony defect with a combined graft of rhBMP-7 (as osteoinductor) with an rCPBS (as scaffold). The mean follow-up was 14±2.7 months. Both clinical and radiological union occurred in 18 cases, within a mean time of 4.7±3.2 months. A recurrence of deep infection was diagnosed for one of the non-consolidated patients. No specific complication of rCPBS or rhBMP-7 was encountered. This study supports the view that the application of rCPBS combined with rhBMP-7, without any bone grafting, is safe and efficient in the treatment of recalcitrant bone union.

Dkk1 haploinsufficiency requires expression of Bmp2 for bone anabolic activity

Bone fractures remain a serious health burden and prevention and enhanced healing of fractures have been obtained by augmenting either BMP or Wnt signaling. However, whether BMP and Wnt signaling are both required or are self-sufficient for anabolic and fracture healing activities has never been fully elucidated. Mice haploinsufficient for Dkk1 (Dkk1(+/-)) exhibit a high bone mass phenotype due to an up-regulation of canonical Wnt signaling while mice lacking Bmp2 expression in the limbs (Bmp2(c/c);Prx1::cre) succumb to spontaneous fracture and are unable to initiate fracture healing; combined, these mice offer an opportunity to examine the requirement for activated BMP signaling on the anabolic and fracture healing activity of Wnts. When Dkk1(+/-) mice were crossed with Bmp2(c/c);Prx1::cre mice, the offspring bearing both genetic alterations were unable to increase bone mass and heal fractures, indicating that increased canonical Wnt signaling is unable to exploit its activity in absence of Bmp2. Thus, our data suggest that BMP signaling is required for Wnt-mediated anabolic activity and that therapies aimed at preventing fractures and fostering fracture repair may need to target both pathways for maximal efficacy.

Autograft versus BMPs for the treatment of non-unions: what is the evidence?

Autograft is considered the gold standard in non-union treatment. However, it is associated with significant morbidity and limited biological activity. The introduction of bone morphogenetic proteins (BMPs) has added a valuable tool to the surgeon's possibilities. The initial expectations of the effectiveness of BMPs were high, but over the years the union rate of BMPs was shown to be comparable with autograft. In this overview, both treatment modalities are compared. The off-label use of BMPs, the combination of BMPs and autograft, and the economic perspective of BMP use are summarized. In their current formulation, BMPs are an effective alternative for autograft in selected cases. The beneficial effect outweighs the economic costs. Widening of the indication to other long bone non-unions and new formulations are expected in the nearby future.

Perspective on the evolution of cell-based bone tissue engineering strategies

Despite the compelling clinical needs in enhancing bone regeneration and the potential offered by the field of tissue engineering, the adoption of cell-based bone graft substitutes in clinical practice is limited to date. In fact, no study has yet convincingly demonstrated reproducible clinical performance of tissue-engineered implants and at least equivalent cost-effectiveness compared to the current treatment standards. Here, we propose and discuss how tissue engineering strategies could be evolved towards more efficient solutions, depicting three different experimental paradigms: (i) bioreactor-based production; (ii) intraoperative manufacturing, and (iii) developmental engineering. The described approaches reflect the need to streamline graft manufacturing processes while maintaining the potency of osteoprogenitors and recapitulating the sequence of biological steps occurring during bone development, including vascularization. The need to combine the assessment of efficacy of the different strategies with the understanding of their mechanisms of action in the target regenerative processes is highlighted. This will be crucial to identify the necessary and sufficient set of signals that need to be delivered at the injury or defect site and should thus form the basis to define release criteria for reproducibly effective engineered bone graft substitutes.

Allograft bone matrix versus synthetic bone graft substitutes

Autologous bone is used very often in the treatment of fresh fractures, delayed unions and non-unions. Alternatives have included allografts and in recent years also demineralized bone matrix. The growing availability of good synthetic bone grafts and their advantages in safety and avoiding donor-site morbidity are the reasons that these products are being used more and more. There are on the market a wide variety of substitutes with different capabilities. Nevertheless autologous bone graft is still considered as the gold standard and will be discussed here in that context. Osteoconductive, osteogenic and osteoinductive products will also be classified and their advantages and disadvantages described.

TRACP 5b and CTX as osteological markers of delayed fracture healing

Radiological studies are the standard method to monitor fracture healing but they do not allow a timely assessment of bone healing. Biochemical markers react rapidly to changes in bone metabolism during fracture healing and could be an additional tool to monitor this process. The goal of this study was to observe changes in serum biomarkers and evaluate the possible differences in the serum levels of tartrate-resistant acid phosphatase 5b (TRACP 5b), total N-terminal propeptide of type I collagen (PINP), bone-specific alkaline phosphatase (BAP), and C-terminal cross-linking telopeptide of type I collagen (CTX) in patients with normal and delayed fracture healing. Several serum samples were collected for one year after the surgical treatment of long bone fractures in 248 patients. From this large pool, 15 patients with atrophic nonunion were matched to 15 patients with normal bone healing. Post-operative changes in osteological markers were monitored during the 1st, 2nd, 4th, 8th, 12th and 52nd weeks. The patients were followed both clinically and radiologically for the entire one-year duration of the study. In the first week, the absolute values of CTX decreased significantly (p=0.0164) in cases of delayed fracture healing. The relative values of TRACP 5b were significantly decreased at weeks 4 (p=0.0066) and 8 (p=0.0043). BAP and PINP levels decreased in the first week followed by an increase, but there were no significant differences in the absolute or relative values during the healing process in both patient groups. For the first time, we have demonstrated changes in serum concentrations of TRACP 5b, PINP, BAP, and CTX during normal and delayed fracture healing. Characteristic changes in systemic TRACP 5b and CTX levels could reflect the initial process of successful fracture healing and may be used in clinical practice to monitor the healing process. Furthermore, it could be very important for determining the beneficial effects of additional treatments such as ultrasound or BMPs in clinical trials.

Clinical application of BMP 7 in long bone non-unions

BACKGROUND

Non-unions of long bone fractures are a therapeutic and economic problem of increasing frequency. Aside from conservative treatment options such as ultrasound, impulse waves, and casts, the basic surgical options are autogenous cancellous bone grafting, rod dynamization, reamed nailing, plate fixation, and bone transport techniques. If these methods fail to work, there is a need for alternative treatment options.

METHODS

Since May 2001, treatment with recombinant human bone morphogenic protein 7 (BMP 7 or osteogenic protein 1) in combination with a type-one collagen carrier has been the subject of increasing interest. BMP 7 induces the formation of new bone by stem cell differentiation, thereby initiating the reaction cascade of osteogenesis. Non-unions over 9 months and unsuccessful bone grafting constitute the indication for this treatment.

RESULTS

We report our experience with 54 patients who had atrophic non-union of long bone fractures. Between May 2002 and May 2006, 57 units of BMP 7 were used. The localization of the non-unions included 21 in the femur, 26 in the tibia, 3 in the humerus and 7 in the forearm. In 36 cases, BMP 7 was used in combination with osteosynthesis revision and bone grafting; in 9 additional patients, BMP 7 was used with bone grafting alone. In 12 patients, BMP 7 was applied as a single procedure without any bone grafting or any change in osteosynthesis.

CONCLUSIONS

There were no perioperative or postoperative complications. Follow-up was obtained for a minimum of 6 months. 47 of the 57 (82%) implantations were successful, with bony healing confirmed by clinical and radiological evaluation. In summary, our results support BMP 7 as an additional innovative therapy for long bone non-unions.

The synergistic effect of autograft and BMP-7 in the treatment of atrophic nonunions

Combining autologous bone graft and recombinant human bone morphogenetic protein-7 (BMP-7) to treat long-bone fracture aseptic atrophic nonunions theoretically could promote bone healing at higher rates than each of these grafting agents separately. We retrospectively reviewed prospectively collected data on patient general characteristics, clinical outcomes, and complications over 3 years to determine the healing rates and the incidence of complications and adverse events of this "graft expansion rationale." There were 45 patients (32 male) with a median age of 43 years (range, 19-76 years). Minimum followup was 12 months (mean, 24.5 months; range, 12-65 months). There were seven humeral, 19 femoral, and 19 tibial nonunions. The median number of prior operations was two (range, 1-7). All fractures united. Clinical and radiographic union occurred within a median of 5 months (range, 3-14 months) and 6 months (range, 4-16 months), respectively. Thirty-nine (87%) patients returned to their preinjury occupation at a mean of 4.2 months (range, 3-6 months). The median visual analog scale pain score was 0.9 (range, 0-2.8; maximum 10), and the median functional score was 86 (range, 67-95; maximum 100) at the final followup. BMP-7 as a bone-stimulating agent combined with conventional autograft resulted in a nonunion healing rate of 100% in these 45 patients.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Application of BMP-7 to tibial non-unions: a 3-year multicenter experience

The effective treatment of the often debilitating, longlasting and large-asset-consuming complication of fracture non-unions has been in the centre of scientific interest the last decades. The use of alternative bone substitutes to the gold standard of autologous graft includes the osteoinductive molecules named bone morphogenetic proteins (BMPs). A multicenter registry and database (bmpusergroup.co.uk) focused on the application of BMP-7/OP-1 was created in December 2005. We present the preliminary results, using the prospective case-series of aseptic tibial non-unions as an example. Sixty-eight patients fulfilled the inclusion criteria for this observational study, with a minimum follow-up of 12 months. The median duration of tibial non-union prior to BMP-7 application was 23 months (range 9-317 mo). Patients had undergone a median of 2 (range 0-11) revision procedures prior to the administration of BMP-7. In 41% the application of BMP-7 was combined with revision of the fixation at the non-union site. Non-union healing was verified in 61 (89.7%) in a median period of 6.5 months (range 3-15 mo). No adverse events or complications were associated with BMP-7 application. The safety and efficacy of BMP-7 was verified in our case series, and was comparable to the existing evidence. The establishment of multicenter networks and the systematic and long-term follow- up of these patients are expected to provide further information and significantly improve our understanding of this promising osteoinductive bone substitute.

Carrier systems and application of growth factors in orthopaedics

With optimal surgical treatment within an appropriate time frame, bony tissue has the potential to regenerate defects without the formation of scar tissue. However, even under optimal mechanical circumstances and appropriate operative treatment, healing can fail and delayed or non-union occur. In Europe delayed bone healing leads to socio-economic costs of up to 14.7 billion euros per year. In addition to the optimal clinical treatment, the success of bone regeneration depends on the following main aspects: (1) adequate mechanical stabilization and biological competence of the organism, (2) osteogenic cells, (3) osteoconductive structures or scaffolds, and (4) growth factors (Diamond Concept)(1). Further, (5) a sufficient vascularisation is essential for the nutritive supply. Within the last years two growth factors, BMP-2 and BMP-7, were approved for clinical use in orthopaedic and trauma surgery for different indications.(2,3) The establishment of carrier systems and application techniques for growths factors is the focus of current research. The combination of a well established stabilization system and local drug delivery system for bioactive factors could be a therapeutical strategy to optimize bone healing and reduce the complication rate, in the future.