- Email: [email protected]
Can we accelerate fracture healing?
Injury, Int. J. Care Injured (2007) 38S1, S81—S89
www.elsevier.com/locate/injury
Can we accelerate fracture healing? A critical analysis of the literature Peter Giannoudis1, Spyridon Psarakis1, George Kontakis2 1 2
Department of Trauma & Orthopaedics, School of Medicine, University of Leeds, UK Department of Trauma & Orthopaedics, School of Medicine, University of Crete, Greece
KEyWORDS: Fracture healing, acceleration, growth factors, BMPs
Summary1 The characterization of the molecular mediators regulating the fracture healing response over the past decade has vastly expanded our knowledge in this area at the molecular level. It is clear today that the physiological mechanisms governing the biology of bone repair and turnover are complex and far from being well understood. Several of the molecules implicated in the healing process have become available for use in the clinical setting thanks to advances made in recombinant technology. Current evidence of their effect in accelerating fracture healing in both experimental and clinical studies is promising. However, despite these findings, several factors require further investigation, including the ideal timing to administer these molecules, which is the most effective dose, and the factors affecting the lack of consistency in the experimental designs and animal models that have been used. In addition, the available evidence lacks phase III, level I studies. Until such studies become available, the results should be interpreted with caution.
Introduction Fracture healing involves the interaction of molecular mediators and cells [8]. A local inflammatory reaction is initiated in the immediate aftermath of a fracture leading to chemotaxis of cells and activation of several intracellular signal molecules, cytokines, adhesion molecules, and other autocoids [21, 23, 25]. Fracture healing is a well-orchestrated physiological process that leads to proliferation and differentiation of osteoprogenitor cells to osteoblasts, osteoclasts, chondroblasts, fibroblasts, and endothelial cells [26]. Depending on its personality, every fracture requires special consideration by the treating phy-
1
Abstracts in German, French, Spanish, Japanese, and Russian are printed at the end of this supplement.
0020–1383/$ — see front matter # 2007 Published by Elsevier Ltd. doi:10.1016/j.injury.2007.02.013
sician prior to deciding whether it can be treated surgically or nonsurgically. Either way, the fracture is usually expected to progress to healing within an defined period of time. Different modalities have been used to stabilize fractures, with excellent results in most cases. However, complications such as nonunion or delayed union can still occur, albeit rarely [31]. It is estimated that of the six million fractures that occur annually in the United States, between 5% and 10% end up in nonunion or delayed union [10]. Autogenous cancellous bone grafting remains the gold standard method used to promote union by stimulating the local biology at the nonunion site [2]. However, due to the limited quantity of such bone grafting, other biologically based strategies have been developed over the years, including electrical, ultrasound, and shockwave stimulation, a variety of bone graft substitutes with either osteoconductive or both osteoconductive and osteoinductive properties, and growth factors that are
S82 administered either locally or systemically, including bone morphogenetic proteins (BMPs), platelet-derived growth factors, and parathyroid hormone [15, 51, 55, 58]. All these biological response modifiers appear to have been used successfully in managing nonunions [24, 27, 32]. Another possible application of these agents in the clinical setting is the acceleration of fresh fracture healing, which would lead to potential advantages in patient care and health economics. The purpose of this article therefore is to evaluate whether acceleration of fresh fracture healing could be achieved using any of the available naturally occurring molecules or those developed by recombinant technology.
A. The effect of BMPs i) Experimental studies Several authors have investigated whether bone healing can be accelerated in fracture/osteotomy animal models as well as in clinical cases with fresh fractures by using BMPs. Welch et al studied the effects of recombinant human BMP-2 (rhBMP-2) in an absorbable collagen sponge on bone healing in a skeletally mature goat tibial fracture model [66]. The bilateral closed tibial fractures were reduced and stabilized with external fixation. Either rhBMP-2 or buffer-ingrained collagen sponges with the contralateral fracture served as a control. At six weeks, the rhBMP-2 fractures had superior radiographic healing scores compared with buffer groups and controls. When the absorbable collagen sponge was wrapped around the fracture, a significantly tougher callus was produced compared with laying it on the fracture. The increased callus volume associated with rhBMP-2 treatment produced moderate increases in strength and stiffness. In a different goat model, den Boer et al investigated the ability of rhBMP-7 (osteogenic protein, OP-1) to accelerate normal physiological fracture healing with experimentally produced closed tibial fractures [18]. All fractures were stabilized with an external fixator and the efficacy of the OP-1 (injected with different carriers) to accelerate fracture healing was tested. The authors concluded that the healing of a closed fracture in a goat model can be accelerated by a single local administration of rhOP1. The use of a carrier material did not seem to be crucial in this application of rhOP-1. Bouxsein et al demonstrated that rhBMP-2 applied with an absorbable collagen sponge as a carrier resulted in an approximately 33% acceleration
P Giannoudis et al of healing in a rabbit ulnar osteotomy model [9]. rhBMP-2 was retained at the osteotomy site even two weeks after its application (8% +/- 7%). By four weeks, the biomechanical properties of the ulnae treated with an rhBMP-2 were equivalent to those of the intact ulnae, whereas the biomechanical properties of those treated either with a sponge ingrained only by a buffer or left untreated had reached only approximately 45% of those of the intact ulnae. Potential limitations of this study include the use of an osteotomy instead of a real fracture and the rapid healing of rabbit bones in general, which is due to a possibly greater number of cells and their more intense reaction to rhBMP-2. Similarly, fracture healing acceleration and biomechanically stronger callus were shown in another study using the same osteotomy model and rhBMP-2 in an injectable calcium phosphate carrier (alpha-BSM) [37]. In another rabbit model, recombinant human BMP-2 delivered via collagen gel or buffer injection was shown to have minimal impact on healing under stable mechanical conditions while accelerated bone healing in nonstabilized fractures compared with controls was observed [3]. Einhorn et al investigated whether a single, local, percutaneous injection of rhBMP-2 would accelerate fracture healing in a standard rat femoral fracture model [22]. They compared three groups of animals: one group received an injection of 80 μg of rhBMP-2 in 25 μL of buffer vehicle, the second one received an injection of 25 μL of buffer vehicle alone, and the third group did not receive an injection. They showed that bone healing in the group with rhBMP2 was faster than in the other two groups. At four weeks, the stiffness and strength of the healed femora with the use of rhBMP-2 were equal to those of the contralateral sound femora, whereas in the other two groups, the stiffness and strength were significantly lower than the sound femora. This study is one of the first ones that showed the utility of a closed application of BMP in accelerating fracture healing in an animal model. Because the time course of this study was four weeks, and the untreated fractures in the control group did not heal during this period, an accurate quantification of the magnitude of the acceleration of fracture healing by rhBMP-2 was not possible. The reduction in the time to healing was estimated to be between 20% and 50%. Seeherman et al used a nonhuman fibular osteotomy model (in adult male Cynomogus monkeys) to evaluate eight rhBMP-2/carrier formulations that can be administered in closed fractures [57]. Initially, they administered each formulation in three monkeys. Because the combination of rhBMP-2/αbone substitute material (α-BSM) resulted in more consistent acceleration of fracture healing at ten
Can we accelerate fracture healing? A critical analysis of the literature weeks after the injection than the other rhBMP-2 formulations did, they performed a confirmatory experiment using rhBMP-2/α-BSM in eleven additional animals. They concluded that a single percutaneous injection of rhBMP-2/α-BSM accelerates the healing of fibular osteotomy sites by approximately 40% compared with the healing of an untreated osteotomy site and that this may be a promising injectable treatment for accelerating closed fracture healing in humans. The inconsistency of the other formulations in this study can be attributed to: the possibly different requirements for rhBMP-2 retention in the more slowly healing nonhuman primate model, the small group sizes (three animals for each formulation), and to the variability in the healing rates of the control osteotomy sites. Table 1 summarizes the published studies on the use of BMPs in several animal fracture or osteotomy models.
ii) Clinical studies in humans with fractures In a prospective, randomized, controlled, singleblind study, published by the BESTT study group, the safety and the efficacy of rhBMP-2 to accelerate healing of open tibial shaft fractures was evaluated. 450 patients were randomly allocated into three almost equal groups: (1) the control group of standard care, where intramedullary nail fixation and routine soft-tissue management was performed; (2) the group of standard care and an implant containing 0.75 mg/ml of rhBMP-2; and (3) the group of standard care and an implant containing 1.50 mg/ml of rhBMP-2. The authors concluded that the rhBMP-2 administered in a dose of 1.50 mg/ml was significantly superior to group 1 (intramedullary nail fixation and routine soft tissue management) in reducing the frequency of secondary interventions from
Authors
Subject
Fracture/ osteotomy model
Stabilization
Growth factor
Welch et al 199862
goat
tibial
yes
rhBMP-2 collagen spong- yes es or buffer ingrained collagen sponges
Bax et al 19993
rabbit
yes either not
yes
Bouxsein et al. 20018
rabbit
ulnar (osteot- no omy model)
rhBMP-2 (1) on bioerodible particles, (2) in a collagen gel, and (3) by injection. rhBMP-2 applied with an absorbable collagen sponge
Li et al. 200335
rabbit
ulnar (osteot- no omy model)
rhBMP-2/alpha-BSM
yes
femoral
yes
yes
fibular osteotomy model
yes
rhBMP-2 in a buffer vehicle eight rhBMP-2/carrier formulations
tibial
yes
Einhorn et rat al. 200321 Seehermonkey man et al. 200455
den Boer et al. 200217
goat
tibial
S83
Controls Comment
yes
yes
injection of OP-1 either yes isolated or on a collagenous carrier
The rhBMP-2 fractures had superior radiographic healing scores compared with buffer groups and controls. rhBMP-2 delivered by means of collagen gel or buffer injection has accelerated bone healing in non stabilized fractures compared with controls. By four weeks, the biomechanical properties of the ulnae treated with a rhBMP-2 were equivalent to those of the intact ulnae, whereas the biomechanical properties of the ulnae treated either with a sponge ingrained only by a buffer or left untreated had reached only approximately 45% of those of the intact ulnae. rhBMP-2 / alpha-BSM accelerated healing compared to BSM alone and controls rhBMP-2 shortened the time to healing between 20%−50% rhBMP-2/α-BSM resulted in more consistent acceleration of fracture healing at ten weeks than did the other rhBMP-2 formulations (40% acceleration of the compared with the healing of untreated osteotomy site) higher stiffness and strength at 2 weeks after injection of OP-1 − normal fracture healing patterns in all animals − no adverse effects
Table 1: Summary of the published studies regarding the use of bone morphogenetic proteins in several animal fracture or osteotomy models.
S84 46% to 26%, accelerating healing, and reducing the infection rate. In addition, those treated with 1.5 mg/mL of rhBMP-2 required procedures that were less invasive, such as nail dynamization, instead of those that were more invasive, such as bone-grafting or exchange nailing. Limitations of this study are the single blinding (risk for verification bias) and the larger number of reamed nails (beneficial effect of reaming products in fracture union) that were used in the highly dose rhBMP-2 treated group compared to the control group [28]. Recently, Swiontkowski et al reported a subgroup analysis of patients with open tibial fractures treated with 1.50 mg/mL of rhBMP-2 versus intramedullary nail fixation and routine soft-tissue management [60]. The authors concluded that the addition of rhBMP-2 to the treatment of type-III open tibial fractures can significantly reduce the frequency of bone-grafting procedures and other secondary interventions. Similarly, a prospective randomized study examined the effect of rhBMP-7 on the healing of open tibial shaft fractures amenable to intramedullary nailing [42]. According to the preliminary report by the authors, the application of rhBMP-7 to open tibial shaft fractures was safe, technically straightforward to use, not associated with any increase in adverse events, decreased the number of procedures required for delayed union or nonunion, and appeared to correlate with some improvement in function. The same investigation group reported the final results of the above study, concluding that the application of OP-1 in a collagen carrier at the fracture site resulted in fewer secondary interventions than with controls [43]. B. The effect of other growth factors and signaling molecules In addition to BMPs, the efficacy of other biological molecules that have been identified as regulating the fracture healing response has been tested by several investigators. Lind et al administrated exogenous transforming growth factor-β (TGF-β) in a rabbit tibia fracture/osteotomy model in continuous doses of 1−10 µg/day for six weeks and observed an increased maximal bending strength and callus formation [40]. However, Critchlow et al found that exogenous TGF-β 2 does not stimulate fracture healing under either stable or unstable mechanical conditions during the initial healing phase response in rabbit tibiae [16]. Park et al investigated the interaction between axial motion and exogenous TGF-β during tibial fracture repair in a white rabbit model following two injections of TGF-β 1. They noted that TGF-β 1 inhibited the normal development of
P Giannoudis et al peripheral callus when axial interfragmentary motion was present [50]. The effect of TGF-β in a rat tibia model was investigated by Nielsen et al who found increased callus formation and strength. The biomechanical properties were preserved in the group injected with 40 ng of TGF-β [48]. Kawaguchi et al examined the effect of locally applying recombinant human basic fibroblast growth factor (rhbFGF) and found that it facilitated bone union in rats with impaired as well as normal repairing to promote fracture healing by stimulating bone remodeling [47]. Nakajima et al reported that exogenous rhbFGF in a closed fracture of a longbone rat model had a capacity to enlarge the cartilaginous calluses, but not to induce faster healing [46]. In another study of fibroblast growth factor-2, Radomsky et al concluded that there were better biomechanical properties and more pronounced callus size, periosteal reaction, vascularity, and cellularity in the treated osteotomies than in the untreated controls [53]. Other investigators have reported that exogenous rhFGF-2 had an accelerating effect on the repair of metaphyseal fractures in rabbits [11] and was able to prevent nonunion in primates [35]. On the other hand, Bland et al found that the application of exogenous fibroblast growth factors -1 or -2 (FGF-1, FGF-2) to normally healing fractures of rabbit tibia did not significantly affect the rate of healing [4]. Schmidmaier et al investigated the effect of insulin-like growth factor-I (IGF-I) in a rat tibia model. He noted that insulin IGF-I had a greater stimulating effect on fracture healing than TGF-β 1. Applying both growth factors resulted in a significantly higher maximum load and torsional stiffness than only one of them. This group also showed an increase in remodeling of the fracture callus [56]. Similarly, another study reported that local application of IGFI and TGF-β 1 accelerated early cellular processes during fracture healing in a rat model [67]. Street et al assessed the importance of the presence of vascular endothelial growth factor (VEGF) in the local fracture environment. He reported that VEGF inhibition disrupted fracture repair. Exogenous VEGF enhanced blood vessel formation, ossification, and callus maturation in murine femur fractures, and promoted bony bridging of a rabbit radius segmental gap defect [59]. In a rat femora model, thrombin peptide (TP508) accelerated fracture repair and induced expression of early growth factors, inflammatory response modifiers, and angiogenesis-related genes [65]. Table 2 lists published studies on the use of growth factors and signaling molecules, other than BMPs, in animal fracture/osteotomy models.
Can we accelerate fracture healing? A critical analysis of the literature
Authors
Animal model
Fracture / Growth Factor osteotomy site
Lind et al. 199338
rabbit
tibia
Nielsen et al. 199446
rat
Critchlow et al. 199515
rabbit
S85
Controls
Comment
TGF-β (1 and 10 μg/day for yes 6 weeks in two groups)
yes
tibia
TGF-β (4 and 40 ng/ 2nd day until 40 days of healing in two groups)
yes
tibia
TGF-β 2 (60 or 600 ng on day 4 after fracture)
Increased maximal bending strength and callus formation in the groups receiving TGF-beta TGF-beta increased the callus formation and strength. Increased callus biomechanical properties in the group injected with 40 ng of TGF-beta. TGF-beta 2 does not stimulate fracture healing under either stable, or unstable, mechanical conditions during the initial healing phase. The local application of bFGF facilitated bone union in rats with impaired as well as normal repairing ability.
Kawaguchi et al. 199433
rat (normal fibula and streptozotocindiabetic) Bland et al. rabbit tibia 19954
Fracture stabilization
either yes or not
no
either yes or not
no
The application of FGF-1 or FGF-2 to normally healing fractures of the rabbit tibia does not have a significant effect on the rate of healing. bFGF promotes the fracture healing in dogs.
yes
Better biomechanical properties and more pronounced callus size, periosteal reaction, vascularity, and cellularity in the treated osteotomies than in the untreated controls. FGF-2 had an accelerating effect on the repair of metaphyseal fractures. FGF-2 accelerated fracture healing and prevented nonunion in primates.
rhbFGF (single dose)
3 μg of either FGF-1 or FGF-2 on day 4 after fracture
Nakamura et al. 199845 Radomsky et al. 199951
dog
tibia
rhbFGF (single dose of 200 μg)
baboon
fibula
FGF-2 or bFGF (4 mg/ml) in a single local injection
Chen et al. 200410 Kawaguchi et al. 200134 Nakajima et al. 2001
rabbit
tibia
yes
yes
nonhuman primate
ulna
FGF-2 (400 μg in a single local injection) FGF-2 (200 μg in a single local injection) hr bFGF 100 μg in a single local injection
yes
yes
Schmidmaier et al. 200354
rat
poly(D,L-lactide)-coated titanium K-wires with incorporated IGF-I and TGF-beta1, singly or in combination IGF-I and TGF-beta1 (Days 5, 10, and 15 after fracture) TGF-beta 1 (at the time of reduction, and a second dose was given 48 hours later).
yes
yes
yes
One group with locked and another with unlocked external fixators permitting axial motion yes VEGF inhibition disrupted fracture repair. Exogenous VEGF enhanced blood vessel formation, ossification, and callus maturation. yes TP508 accelerated fracture repair and induced expression of early growth factors, inflammatory response modifiers, and angiogenesis-related genes.
rat
44
Wildemann rat et al. 200363 Park et al. rabbit 200348
Street et al. 200257
mice
Wang et al. rat 200561
tibia
tibia
femur
VEGF
femur
TP508
yes
yes
Exogenous bFGF had a capacity to enlarge the cartilaginous calluses, but not to induce more rapid healing. IGF-I had a greater stimulating effect of on fracture healing than of TGF-beta1. Better biomechanical callus properties in the group with combination of both growth factors. Local application of IGF-I and TGF-beta1 accelerates early cellular processes during fracture healing. TGF-beta1 inhibited the normal development of peripheral callus when axial interfragmentary motion existed.
Table 2: Published studies regarding the use of growth factors and signalling molecules, other than BMPs, in animal fracture/osteotomy models.
S86
Discussion With the advances made in molecular medicine and molecular biology, our knowledge of the cellular and molecular events governing the fracture healing response has vastly expanded [52]. Several molecules have been identified that regulate the cascade of events in a time-dependent fashion leading to repair of bone tissue without scar formation [20]. This knowledge has led to a great deal of interest in the application of these molecules in the clinical setting, especially in the treatment of fracture nonunions. Nonunion following fractures continues to be a serious local complication, despite the advances made in our philosophy of fractures stabilization, implant developments, and biological fixation techniques [49]. In addition to nonunion, the administration of these molecules has been considered for a variety of other orthopedic circumstances, including stabilization of implant devices [13, 69], restoration of large segmental bone defects [15, 45], treatment of osteonecrosis of the femoral head [38], fusion of joints, cartilage regeneration [7, 14], augmentation of periprosthetic fractures, and acceleration of fracture healing, especially in patients at high risk of nonunion [28]. In this study, we have attempted to examine the current evidence on the efficacy of these molecules in accelerating the fracture healing response. To start with, we wished to examine the effect of BMPs. In vivo, BMPs regulate many aspects of embryonic development, including cartilage and bone formation, mesoderm patterning, and craniofacial and limb development, as well as postnatal bone formation and repair. They achieve these effects by regulating growth, differentiation, and apoptosis of various cell types, including mesenchymal cells, osteoblasts, chondroblasts, and neural and epithelial cells [54, 61, 64]. They act in an autocrine or paracrine manner [39]. The efficacy of BMPs in managing nonunions and substituting autogenous cancellous bone grafting to facilitate fusion of joints or the spine in general is well established [19, 36]. With regard to their potential to accelerate fracture healing in fresh fractures, several experimental and clinical studies have been performed. Both recombinant BMP-2 and BMP-7 have been tested with positive results in animal models. In goat tibia, rabbit ulna, and rat femur, acceleration of the healing response has been estimated to be as much as 30−40% [3, 9, 18, 22, 37, 66]. In monkeys, a combination of rhBMP-2 and alpha-BSM (bone substitute material) accelerated the healing process by 40% in a single percutaneous dose [57]. However, despite these favorable results, other factors that could exert a beneficial effect have to be taken into
P Giannoudis et al account such as the mechanical stimuli developed at the fracture site and the existence of biological variation amongst species. Contrary to the number of animal reports, very few studies have been performed in humans following fresh fractures. Those that exist have focused on open tibial fractures, a model that is known to be associated with a high risk of complications, particularly nonunion. Administration of rhBMP-2 has been associated with accelerated healing, a reduction in infection rates, fewer invasive procedures, less bone grafting, and a reduced frequency of secondary interventions from 46−26% [28, 60]. Similarly, application of rhBMP-7 was found to decrease the number of secondary interventions, with no adverse effects [42, 43]. While the evidence is more robust in animal studies, the currently available experience in humans is limited and therefore further studies are necessary to reach a definitive conclusion. Furthermore, the results obtained from the experimental studies should be interpreted with caution as they do not always correlate to humans. Besides BMPs other molecules have been considered for use as biological response modifiers to enhance or accelerate the fracture-healing process. TGF and FGF promote blood vessel formation and osteoblast proliferation [41, 44]. VEGF is of particular importance because of its ability to induce angiogenesis and to couple angiogenesis with bone formation and remodeling. Inhibition of VEGF blocks the angiogenic activity of bFGF and BMP-2 [12, 17]. Several studies have evaluated the effect of TGF β, IGF-1 and VEGF in a tibia rat model. Increased callus formation, enlarged cartilaginous calluses, increased remodeling, and acceleration of cellular processes, which all enhance the fracture healing response have been described [48, 59, 67]. The cost of these molecules has been a topic of vivid discussion. An economic model has been used to analyse the cost of treatment of nonunions using BMP-7 [33, 63]. Vinken A et al estimated a total cost per patient receiving BMP-7 of £8,797 compared to £9,084 for autograft, and £13,722 for the Ilizarov fixation technique. The authors concluded that costeffectiveness ratios of all three treatments were comparable [63]. Jones et al developed an economic model based on data from a clinical trial that had demonstrated improved clinical parameters (the rate of fracture healing, secondary interventions, infection rates) when 12 mg of recombinant human bone morphogenetic protein-2 (rhBMP-2) was used as an adjunct to intramedullary nailing in the treatment of open tibial fractures [33]. Their study estimated the cost of treatment with BMP-2 to the hospital at $13,733 and to the patient at $16,734, assuming no BMP-2 reimbursement. They concluded
Can we accelerate fracture healing? A critical analysis of the literature that the clinical benefits of rhBMP-2 used in first line treatment of open tibial fractures translate into reductions in medical costs over a two year period for hospitals and patients. Their estimates showed favourable total cost offsets (the proportion of the upfront rhBMP-2 price offset by other medical resource reductions) when 50% of the BMP-2 cost was reimbursed [33]. Considering the potential for adverse effects of BMP administration preclinical and clinical safety assessments have revealed little evidence of toxic effects and there have been few reports of adverse events related to their use. A small rate of immunological reaction following administration, resulting in antibody formation, has been observed in some patients, without clinical consequence, though the long-term consequences of this are unknown [30]. Perhaps the most obvious potential problem with these products is the induction of excessive bone at the site of application or induction of bone in ectopic sites [7, 62]. Although the majority of the experimental studies have shown promising results, two important factors, the ideal timing of administration and the most effective dose to be administered, have not been investigated in depth. Both of these factors could influence the effect exerted by any of the above molecules in accelerating fracture healing. Several studies have indicated that below a certain dose threshold, the healing response is not as efficient as with higher doses [16, 28, 34, 40, 48, 50]. This issue has been well proven by the administration of demineralized bone matrix (DBM). A significant positive linear relationship between the in vivo production of new bone and BMP-2, BMP-4, and TGF-β 1 levels in human DBM has been found, which suggests that the levels of BMPs and growth factors present in human DBM are clinically relevant [5]. The currently available results prove that the higher the DBM concentration, the higher the osteoinductive potential we get. Based on the studies by Han et al [29], Jung Yoo et al [68], and that by Atti [1], Kay and Vaughan [36] termed this phenomenon the “proportional osteoinduction of DBM graft materials”. In general terms, all the currently available studies support the view that manipulating the local fracture environment could lead to an enhanced and accelerated healing response. It is important to bear in mind, however, that the responses of the various biological models that have been tested differ enormously from the human response. Further clinical studies are now warranted to provide sufficient evidence that we can accelerate fracture healing to the extent that would outweigh the costs and the potential risks of utilizing biologically active molecules.
S87
The expanding clinical applications of BMPs, the anticipated discovery of new growth factors, the better understanding of the biological behavior of important cellular elements and of pathways of the healing process of tissues will offer novel treatment strategies in the enhancement of tissue regeneration in general.
Bibliography 1. Atti E, Abjornson C, Diegmann M, et al. High resolution X-ray computed tomography as a technique to study osteoinductivity of demineralised bone matrix. Proceedings of the NASS 18th Annual Meeting. Spine. 2003 3:120S. 2. Bauer TW, Muschler GF. Bone graft materials. An overview of the basic science. Clin Orthop. 2000 371:10−27. 3. Bax BE, Wozney JM, Ashhurst DE. Bone morphogenetic protein-2 increases the rate of callus formation after fracture of the rabbit tibia. Calcif Tissue Int. 1999 65(1):83−89. 4. Bland YS, Critchlow MA, Ashhurst DE. Exogenous fibroblast growth factors-1 and -2 do not accelerate fracture healing in the rabbit. Acta Orthop Scand. 1995 66(6):543−548. 5. Blum B, Moseley J, Miller L, et al. Measurement of bone morphogenetic proteins and other growth factors in demineralised bone matrix. Orthopedics. 2004 2791 Suppl: s161−165. 6. Boden SD, Kang J, Sandhu H, et al. Use of recombinant human bone morphogenetic protein-2 to achieve posterolateral lumbar spine fusion in humans: a prospective, randomized clinical pilot trial: 2002 Volvo Award in clinical studies. Spine. 2002 27(23):2662−2673. 7. Boden SD, Martin GI Jr, Morone MA, et al. Posterolateral lumbar intertransverse process spine arthrodesis with recombinant human bone morphogenetic protein 2/hydroxyapatitetricalcium phosphate after laminectomy in the nonhuman primate. Spine. 1999 24(12):1179-1185. 8. Bostrom MP. Expression of Bone Morphogenetic Proteins in Fracture Healing. Clin Orthop. 1998 355S:116−123. 9. Bouxsein ML, Turek TJ, Blake CA, et al. Recombinant human bone morphogenetic protein-2 accelerates healing in a rabbit ulnar osteotomy model. J Bone Joint Surg Am. 2001 83-A(8):1219−1230. 10. Brighton CT, Shaman P, Heppenstall RB, Esterhai et al. Tibial non-union treated with direct current, capacitive coupling, or bone graft. Clin Orthop. 1995 321:223−234. 11. Chen WJ, Jingushi S, Aoyama I, et al. Effects of FGF-2 on metaphyseal fracture repair in rabbit tibiae. J Bone Miner Metab. 2004 22(4):303−309. 12. Claffey KP, Abrams K, Shih SC, et al. Fibroblast growth factor 2 activation of stromal cell vascular endothelial growth factor expression and angiogenesis. Lab Invest. 2001 81(1):61−75. 13. Cook SD, Barrack RL, Patron LP, et al. Osteogenic protein1 in knee arthritis and arthroplasty. Clin Orthop. 2004 428:140−145. 14. Cook SD, Dalton JE, Tan EH, et al. In vivo evaluation of recombinant human steogenic protein (rhOP-1) implants as a bone graft substitute for spinal fusions. Spine. 1994 19(15):1655−1663.
S88 15. Cook SD, Wolfe MW, Salkeld SL et al. Effect of recombinant human osteogenic protein-1 on healing of segmental defects in non-human primates. J Bone Joint Surg [Am]. 1995 77(5):734−750. 16. Critchlow MA, Bland YS, Ashhurst DE. he effect of exogenous transforming growth factor-beta 2 on healing fractures in the rabbit. Bone. 1995 16(5):521−527. 17. Deckers MM, van Bezooijen RL, van der Horst G, et al. Bone morphogenetic proteins stimulate angiogenesis through osteoblast-derived vascular endothelial growth factor A. Endocrinology. 2002 143(4):1545−1553. 18. den Boer FC, Bramer JA, Blokhuis TJ, et al. Effect of recombinant human osteogenic protein-1 on the healing of a freshly closed diaphyseal fracture. Bone. 2002 31(1):158−164. 19. Dimitriou R, Dahabreh Z, Katsoulis E, et al. Application of recombinant BMP-7 on persistent upper and lower limb nonunions. Injury. 2005 36 Suppl 4:S51−9. 20. Dimitriou R, Tsiridis E, Giannoudis PV. Current concepts of molecular aspects of bone healing. Injury. 2005 36(12):1392−1404. 21. Dong Y, Canalis E. Insulin-like growth factor (IGF) I and retinoic acid induce the synthesis of IGF-binding protein 5 in rat osteoblastic cells. Endocrinology. 1995 136(5):2000−2006. 22. Einhorn TA, Majeska RJ, Mohaideen A, et al. A single percutaneous injection of recombinant human bone morphogenetic protein-2 accelerates fracture repair. J Bone Joint Surg Am. 2003 85−A(8):1425−1435. 23. Fakhry A, Ratisoontorn C, Vedhachalam C, et al. Effects of FGF-2/-9 in calvarial bone cell cultures: differentiation stagedependent mitogenic effect, inverse regulation of BMP-2 and noggin, and enhancement of osteogenic potential. Bone. 2005 36(2):254−266. 24. Friedlaender GE, Perry CR, Cole JD, et al. Osteogenic protein1 (bone morphogenetic protein-7) in the treatment of tibial nonunions: A prospective, randomized clinical trial comparing rhOP-1 with fresh bone autograft. J Bone Joint Surg [Am]. 2001 83:151−158. 25. Gazzerro E, Pereira RC, Jorgetti V, et al. Skeletal overexpression of gremlin impairs bone formation and causes osteopenia. Endocrinology. 2005 146(2):655−665. 26. Giannoudis PV, Pountos I. Tissue regeneration. The past, the present and the future. Injury. 2005 36 Suppl 4:S2−5. 27. Giannoudis PV, Tzioupis C. Clinical applications of BMP-7: the UK perspective. Injury. 2005 36 Suppl 3:S47−50. 28. Govender S, Csimma C, Genant HK, et al. BMP-2 Evaluation in Surgery for Tibial Trauma (BESTT) Study Group. Recombinant human bone morphogenetic protein-2 for treatment of open tibial fractures: a prospective, controlled, randomized study of four hundred and fifty patients. J Bone Joint Surg Am. 2002 84−A(12):2123−34. 29. Han B, Tang B, Nimni M. A quantitative and sensitive in vitro assay of osteoinductive activity of demineralized bone matrix. J Orthop Res. 2003 21(4):648−654. 30. Harwood PJ, Giannoudis PV. Application of bone morphogenetic proteins in orthopaedic practice: their efficacy and side effects. Expert Opin Drug Saf. 2005 4(1):75−89. 31. Healy WL, Jupiter JB, Kristiansen TK, et al. Nonunion of the proximal humerus. J Orthop Trauma. 1990 4:424−431.
P Giannoudis et al 32. Johnson EE, Urist MR, Finerman GA. Resistant nonunions and partial or complete segmental defects of long bones. Treatment with implants of a composite of human bone morphogenetic protein (BMP) and autolyzed, antigen-extracted, allogeneic (AAA) bone. Clin Orthop. 1992 277:229−237. 33. Jones AL, Swiontkowski MF, Polly DW, et al. Use of rhBMP-2 in the treatment of open tibial shaft fractures: Do improved outcomes outweigh the additional expense of rhBMP-2? [abstract]. OTA 20th Annual Meeting. 2004. 34. Kawaguchi H, Kurokawa T, Hanada K et al. Stimulation of fracture repair by recombinant human basic fibroblast growth factor in normal and streptozotocin-diabetic rats. Endocrinology. 1994 135(2):774−781. 35. Kawaguchi H, Nakamura K, Tabata Y, et al. Acceleration of fracture healing in nonhuman primates by fibroblast growth factor-2. J Clin Endocrinol Metab. 2001 86(2):875−880. 36. Kay JF, Vaughan LM. Proportional osteoinduction of DBM graft materials. IsoTis OrthoBiologics, Inc. Data on file. 37. Li RH, Bouxsein ML, Blake CA, et al. rhBMP-2 injected in a calcium phosphate paste (alpha-BSM) accelerates healing in the rabbit ulnar osteotomy model. J Orthop Res. 2003 21(6):997−1004. 38. Lieberman JR, Conduah A, Urist MR. Treatment of osteonecrosis of the femoral head with core decompression and human bone morphogenetic protein. Clin Orthop. 2004 429:139−145. 39. Lieberman JR, Daluiski A, Einhorn TA. The role of growth factors in the repair of bone. Biology and clinical applications. J Bone Joint Surg [Am]. 2002 84-A(6):1032−1044. 40. Lind M, Schumacker B, Soballe K, et al. Transforming growth factor-beta enhances fracture healing in rabbit tibiae. Acta Orthop Scand. 1993 64(5):553−556. 41. Mandracchia VJ, Nelson SC, Barp EA. Current concepts of bone healing. Clin Podiatr Med Surg. 2001 8(1):55−77. 42. McKee MD and the Canadian Orthopaedic Trauma Society. The effect of human recombinant bone morphogenic protein (RHBMP-7) on the healing of open Tibial shaft fractures: results of a multi-center, prospective, randomized clinical trial. Orthopaedic Trauma Association. 2002 Annual Meeting, Toronto, Ontario, Canada, October 12; Paper 45. 43. McKee MD, Schemitsch EH, Waddell JP, et al. The effect of human recombinant bone morphogenic protein (rhBMP-7) on the healing of open tibial shaft fractures: results of a multicenter, prospective, randomized clinical trial. Read at the Annual Meeting of the American Academy of Orthopaedic Surgeons; Feb 5−9 2003; New Orleans, LA. 44. Midy V, Plouet J. Vasculotropin/vascular endothelial growth factor induces differentiation in cultured osteoblasts. Biochem Biophys Res Commun. 1994 199(1):380−386. 45. Mont MA, Jones LC, Elias JJ, et al. Strut-autografting with and without osteogenic protein-1: a preliminary study of a canine femoral head defect model. J Bone Joint Surg [Am]. 2001 83−A(7):1013−1022. 46. Nakajima F, Ogasawara A, Goto K, et al. Spatial and temporal gene expression in chondrogenesis during fracture healing and the effects of basic fibroblast growth factor. J Orthop Res. 2001 19(5):935−944.
Can we accelerate fracture healing? A critical analysis of the literature 47. Nakamura T, Hara Y, Tagawa M, et al. Tamura M, Yuge T, Fukuda H, Nigi H. Recombinant human basic fibroblast growth factor accelerates fracture healing by enhancing callus remodeling in experimental dog tibial fracture. J Bone Miner Res. 1998 13(6):942−949. 48. Nielsen HM, Andreassen TT, Ledet T, et al. Local injection of TGF-beta increases the strength of tibial fractures in the rat. Acta Orthop Scand. 1994 65(1):37−41. 49. Papakostidis C, Grotz MR, Papadokostakis G, et al. Femoral Biologic Plate Fixation. Clin Orthop Relat Res. 2006 May 11; [Epub ahead of print]. 50. Park SH, O›Connor KM, McKellop H. Interaction between active motion and exogenous transforming growth factor Beta during tibial fracture repair. J Orthop Trauma. 2003 17(1):2−10. 51. Paterson DC, Lewis GN, Cass CA. Treatment of delayed union and nonunion with an implanted direct current stimulator. Clin Orthop. 1980 148:117−128. 52. Pountos I, Giannoudis PV. Biology of mesenchymal stem cells. Injury. 2005 36 Suppl 3:S8−S12. 53. Radomsky ML, Aufdemorte TB, Swain LD, et al. Novel formulation of fibroblast growth factor-2 in a hyaluronan gel accelerates fracture healing in nonhuman primates. J Orthop Res. 1999 17(4):607−614. 54. Sakou T. Bone morphogenetic proteins: from basic studies to clinical approaches. Bone. 1998 22:591−603. 55. Schaden W, Fischer A, Sailler A. Extracorporeal shock wave therapy of nonunion or delayed osseous union. Clin Orthop. 2001 387:90−94. 56. Schmidmaier G, Wildemann B, Gabelein T, et al. Synergistic effect of IGF-I and TGF-beta1 on fracture healing in rats: single versus combined application of IGF-I and TGF-beta1. Acta Orthop Scand. 2003 74(5):604−610. 57. Seeherman HJ, Bouxsein M, Kim H, et al. Recombinant human bone morphogenetic protein-2 delivered in an injectable calcium phosphate paste accelerates osteotomy-site healing in a nonhuman primate model. J Bone Joint Surg Am. 2004 86−A(9):1961−72. 58. Shen HC, Peng H, Usas A et al. Structural and functional healing of critical-size segmental bone defects by transduced muscle-derived cells expressing BMP4. J Gene Med. 2004 6(9):984−991. 59. Street J, Bao M, deGuzman L, et al. Bunting S, Peale FV Jr, Ferrara N, Steinmetz H, Hoeffel J, Cleland JL, Daugherty A, van Bruggen N, Redmond HP, Carano RA, Filvaroff EH. Vascular endothelial growth factor stimulates bone repair by promoting angiogenesis and bone turnover. Proc Natl Acad Sci U S A. 2002 99(15):9656−9661. 60. Swiontkowski MF, Aro HT, Donell S, et al. Recombinant human bone morphogenetic protein-2 in open tibial fractures. A subgroup analysis of data combined from two prospective randomized studies. J Bone Joint Surg Am. 2006 88(6):1258−65. 61. Termaat MF, Den Boer FC, Bakker FC, et al. Bone morphogenetic proteins. Development and clinical efficacy in the treatment of fractures and bone defects. J Bone Joint Surg [Am]. 2005 87(6): 1367−1378.
S89
62. Vaccaro AR, Patel T, Fischgrund J et al. A pilot safety and efficacy study of OP-1 putty (rhBMP-7) as an adjunct to iliac crest autograft in posterolateral lumbar fusions. Eur Spine J. 2003 12(5):495-500. 63. Vinken A, van Engen A, Albert J, et al. The cost-effectiveness of Osigraft® (Osteogenic Protein 1) in the treatment of tibial nonunions in the UK and Germany [poster presentation]. 6th EFFORT Congress, 2003. 64. Wan M, Cao X. BMP signalling in skeletal development. Biochem Biophys Res Commun. 2005 328(3):651−7. 65. Wang H, Li X, Tomin E, et al. Thrombin peptide (TP508) promotes fracture repair by up-regulating inflammatory mediators, early growth factors, and increasing angiogenesis. J Orthop Res. 2005 23(3):671−679. 66. Welch RD, Jones AL, Bucholz RW. Effect of recombinant human bone morphogenetic protein-2 on fracture healing in a goat tibial fracture model. J Bone Miner Res. 1998 13(9):1483−1490. 67. Wildemann B, Schmidmaier G, Ordel S, et al. Cell proliferation and differentiation during fracture healing are influenced by locally applied IGF-I and TGF-beta1: comparison of two proliferation markers, PCNA and BrdU. J Biomed Mater Res B Appl Biomater. 2003 65(1):150−156. 68. Yoo J, Birkedal J, Changs S, et al. Spinal arthrodesis using a demineralized bone/hyaluronan matrix and bone marrow. Proceedings of the NASS 18th Annual Meeting. Spine J. 2003 3: 143S. 69. Zhang R, An Y, Toth CA, et al. Osteogenic protein-1 enhances osteointegration of titanium implants coated with periapatite in rabbit femoral defect. J Biomed Mater Res. 2004 71B(2):408−413.
Correspondence address Prof P Giannoudis Department of Trauma & Orthopaedics, St James’s University Hospital, Beckett Street, Leeds, LS9 7TF, United Kingdom e-mail: [email protected]
This paper has been written entirely by the authors, and has received no external funding. The authors have no significant financial interest or other relationship.
www.elsevier.com/locate/injury
Can we accelerate fracture healing? A critical analysis of the literature Peter Giannoudis1, Spyridon Psarakis1, George Kontakis2 1 2
Department of Trauma & Orthopaedics, School of Medicine, University of Leeds, UK Department of Trauma & Orthopaedics, School of Medicine, University of Crete, Greece
KEyWORDS: Fracture healing, acceleration, growth factors, BMPs
Summary1 The characterization of the molecular mediators regulating the fracture healing response over the past decade has vastly expanded our knowledge in this area at the molecular level. It is clear today that the physiological mechanisms governing the biology of bone repair and turnover are complex and far from being well understood. Several of the molecules implicated in the healing process have become available for use in the clinical setting thanks to advances made in recombinant technology. Current evidence of their effect in accelerating fracture healing in both experimental and clinical studies is promising. However, despite these findings, several factors require further investigation, including the ideal timing to administer these molecules, which is the most effective dose, and the factors affecting the lack of consistency in the experimental designs and animal models that have been used. In addition, the available evidence lacks phase III, level I studies. Until such studies become available, the results should be interpreted with caution.
Introduction Fracture healing involves the interaction of molecular mediators and cells [8]. A local inflammatory reaction is initiated in the immediate aftermath of a fracture leading to chemotaxis of cells and activation of several intracellular signal molecules, cytokines, adhesion molecules, and other autocoids [21, 23, 25]. Fracture healing is a well-orchestrated physiological process that leads to proliferation and differentiation of osteoprogenitor cells to osteoblasts, osteoclasts, chondroblasts, fibroblasts, and endothelial cells [26]. Depending on its personality, every fracture requires special consideration by the treating phy-
1
Abstracts in German, French, Spanish, Japanese, and Russian are printed at the end of this supplement.
0020–1383/$ — see front matter # 2007 Published by Elsevier Ltd. doi:10.1016/j.injury.2007.02.013
sician prior to deciding whether it can be treated surgically or nonsurgically. Either way, the fracture is usually expected to progress to healing within an defined period of time. Different modalities have been used to stabilize fractures, with excellent results in most cases. However, complications such as nonunion or delayed union can still occur, albeit rarely [31]. It is estimated that of the six million fractures that occur annually in the United States, between 5% and 10% end up in nonunion or delayed union [10]. Autogenous cancellous bone grafting remains the gold standard method used to promote union by stimulating the local biology at the nonunion site [2]. However, due to the limited quantity of such bone grafting, other biologically based strategies have been developed over the years, including electrical, ultrasound, and shockwave stimulation, a variety of bone graft substitutes with either osteoconductive or both osteoconductive and osteoinductive properties, and growth factors that are
S82 administered either locally or systemically, including bone morphogenetic proteins (BMPs), platelet-derived growth factors, and parathyroid hormone [15, 51, 55, 58]. All these biological response modifiers appear to have been used successfully in managing nonunions [24, 27, 32]. Another possible application of these agents in the clinical setting is the acceleration of fresh fracture healing, which would lead to potential advantages in patient care and health economics. The purpose of this article therefore is to evaluate whether acceleration of fresh fracture healing could be achieved using any of the available naturally occurring molecules or those developed by recombinant technology.
A. The effect of BMPs i) Experimental studies Several authors have investigated whether bone healing can be accelerated in fracture/osteotomy animal models as well as in clinical cases with fresh fractures by using BMPs. Welch et al studied the effects of recombinant human BMP-2 (rhBMP-2) in an absorbable collagen sponge on bone healing in a skeletally mature goat tibial fracture model [66]. The bilateral closed tibial fractures were reduced and stabilized with external fixation. Either rhBMP-2 or buffer-ingrained collagen sponges with the contralateral fracture served as a control. At six weeks, the rhBMP-2 fractures had superior radiographic healing scores compared with buffer groups and controls. When the absorbable collagen sponge was wrapped around the fracture, a significantly tougher callus was produced compared with laying it on the fracture. The increased callus volume associated with rhBMP-2 treatment produced moderate increases in strength and stiffness. In a different goat model, den Boer et al investigated the ability of rhBMP-7 (osteogenic protein, OP-1) to accelerate normal physiological fracture healing with experimentally produced closed tibial fractures [18]. All fractures were stabilized with an external fixator and the efficacy of the OP-1 (injected with different carriers) to accelerate fracture healing was tested. The authors concluded that the healing of a closed fracture in a goat model can be accelerated by a single local administration of rhOP1. The use of a carrier material did not seem to be crucial in this application of rhOP-1. Bouxsein et al demonstrated that rhBMP-2 applied with an absorbable collagen sponge as a carrier resulted in an approximately 33% acceleration
P Giannoudis et al of healing in a rabbit ulnar osteotomy model [9]. rhBMP-2 was retained at the osteotomy site even two weeks after its application (8% +/- 7%). By four weeks, the biomechanical properties of the ulnae treated with an rhBMP-2 were equivalent to those of the intact ulnae, whereas the biomechanical properties of those treated either with a sponge ingrained only by a buffer or left untreated had reached only approximately 45% of those of the intact ulnae. Potential limitations of this study include the use of an osteotomy instead of a real fracture and the rapid healing of rabbit bones in general, which is due to a possibly greater number of cells and their more intense reaction to rhBMP-2. Similarly, fracture healing acceleration and biomechanically stronger callus were shown in another study using the same osteotomy model and rhBMP-2 in an injectable calcium phosphate carrier (alpha-BSM) [37]. In another rabbit model, recombinant human BMP-2 delivered via collagen gel or buffer injection was shown to have minimal impact on healing under stable mechanical conditions while accelerated bone healing in nonstabilized fractures compared with controls was observed [3]. Einhorn et al investigated whether a single, local, percutaneous injection of rhBMP-2 would accelerate fracture healing in a standard rat femoral fracture model [22]. They compared three groups of animals: one group received an injection of 80 μg of rhBMP-2 in 25 μL of buffer vehicle, the second one received an injection of 25 μL of buffer vehicle alone, and the third group did not receive an injection. They showed that bone healing in the group with rhBMP2 was faster than in the other two groups. At four weeks, the stiffness and strength of the healed femora with the use of rhBMP-2 were equal to those of the contralateral sound femora, whereas in the other two groups, the stiffness and strength were significantly lower than the sound femora. This study is one of the first ones that showed the utility of a closed application of BMP in accelerating fracture healing in an animal model. Because the time course of this study was four weeks, and the untreated fractures in the control group did not heal during this period, an accurate quantification of the magnitude of the acceleration of fracture healing by rhBMP-2 was not possible. The reduction in the time to healing was estimated to be between 20% and 50%. Seeherman et al used a nonhuman fibular osteotomy model (in adult male Cynomogus monkeys) to evaluate eight rhBMP-2/carrier formulations that can be administered in closed fractures [57]. Initially, they administered each formulation in three monkeys. Because the combination of rhBMP-2/αbone substitute material (α-BSM) resulted in more consistent acceleration of fracture healing at ten
Can we accelerate fracture healing? A critical analysis of the literature weeks after the injection than the other rhBMP-2 formulations did, they performed a confirmatory experiment using rhBMP-2/α-BSM in eleven additional animals. They concluded that a single percutaneous injection of rhBMP-2/α-BSM accelerates the healing of fibular osteotomy sites by approximately 40% compared with the healing of an untreated osteotomy site and that this may be a promising injectable treatment for accelerating closed fracture healing in humans. The inconsistency of the other formulations in this study can be attributed to: the possibly different requirements for rhBMP-2 retention in the more slowly healing nonhuman primate model, the small group sizes (three animals for each formulation), and to the variability in the healing rates of the control osteotomy sites. Table 1 summarizes the published studies on the use of BMPs in several animal fracture or osteotomy models.
ii) Clinical studies in humans with fractures In a prospective, randomized, controlled, singleblind study, published by the BESTT study group, the safety and the efficacy of rhBMP-2 to accelerate healing of open tibial shaft fractures was evaluated. 450 patients were randomly allocated into three almost equal groups: (1) the control group of standard care, where intramedullary nail fixation and routine soft-tissue management was performed; (2) the group of standard care and an implant containing 0.75 mg/ml of rhBMP-2; and (3) the group of standard care and an implant containing 1.50 mg/ml of rhBMP-2. The authors concluded that the rhBMP-2 administered in a dose of 1.50 mg/ml was significantly superior to group 1 (intramedullary nail fixation and routine soft tissue management) in reducing the frequency of secondary interventions from
Authors
Subject
Fracture/ osteotomy model
Stabilization
Growth factor
Welch et al 199862
goat
tibial
yes
rhBMP-2 collagen spong- yes es or buffer ingrained collagen sponges
Bax et al 19993
rabbit
yes either not
yes
Bouxsein et al. 20018
rabbit
ulnar (osteot- no omy model)
rhBMP-2 (1) on bioerodible particles, (2) in a collagen gel, and (3) by injection. rhBMP-2 applied with an absorbable collagen sponge
Li et al. 200335
rabbit
ulnar (osteot- no omy model)
rhBMP-2/alpha-BSM
yes
femoral
yes
yes
fibular osteotomy model
yes
rhBMP-2 in a buffer vehicle eight rhBMP-2/carrier formulations
tibial
yes
Einhorn et rat al. 200321 Seehermonkey man et al. 200455
den Boer et al. 200217
goat
tibial
S83
Controls Comment
yes
yes
injection of OP-1 either yes isolated or on a collagenous carrier
The rhBMP-2 fractures had superior radiographic healing scores compared with buffer groups and controls. rhBMP-2 delivered by means of collagen gel or buffer injection has accelerated bone healing in non stabilized fractures compared with controls. By four weeks, the biomechanical properties of the ulnae treated with a rhBMP-2 were equivalent to those of the intact ulnae, whereas the biomechanical properties of the ulnae treated either with a sponge ingrained only by a buffer or left untreated had reached only approximately 45% of those of the intact ulnae. rhBMP-2 / alpha-BSM accelerated healing compared to BSM alone and controls rhBMP-2 shortened the time to healing between 20%−50% rhBMP-2/α-BSM resulted in more consistent acceleration of fracture healing at ten weeks than did the other rhBMP-2 formulations (40% acceleration of the compared with the healing of untreated osteotomy site) higher stiffness and strength at 2 weeks after injection of OP-1 − normal fracture healing patterns in all animals − no adverse effects
Table 1: Summary of the published studies regarding the use of bone morphogenetic proteins in several animal fracture or osteotomy models.
S84 46% to 26%, accelerating healing, and reducing the infection rate. In addition, those treated with 1.5 mg/mL of rhBMP-2 required procedures that were less invasive, such as nail dynamization, instead of those that were more invasive, such as bone-grafting or exchange nailing. Limitations of this study are the single blinding (risk for verification bias) and the larger number of reamed nails (beneficial effect of reaming products in fracture union) that were used in the highly dose rhBMP-2 treated group compared to the control group [28]. Recently, Swiontkowski et al reported a subgroup analysis of patients with open tibial fractures treated with 1.50 mg/mL of rhBMP-2 versus intramedullary nail fixation and routine soft-tissue management [60]. The authors concluded that the addition of rhBMP-2 to the treatment of type-III open tibial fractures can significantly reduce the frequency of bone-grafting procedures and other secondary interventions. Similarly, a prospective randomized study examined the effect of rhBMP-7 on the healing of open tibial shaft fractures amenable to intramedullary nailing [42]. According to the preliminary report by the authors, the application of rhBMP-7 to open tibial shaft fractures was safe, technically straightforward to use, not associated with any increase in adverse events, decreased the number of procedures required for delayed union or nonunion, and appeared to correlate with some improvement in function. The same investigation group reported the final results of the above study, concluding that the application of OP-1 in a collagen carrier at the fracture site resulted in fewer secondary interventions than with controls [43]. B. The effect of other growth factors and signaling molecules In addition to BMPs, the efficacy of other biological molecules that have been identified as regulating the fracture healing response has been tested by several investigators. Lind et al administrated exogenous transforming growth factor-β (TGF-β) in a rabbit tibia fracture/osteotomy model in continuous doses of 1−10 µg/day for six weeks and observed an increased maximal bending strength and callus formation [40]. However, Critchlow et al found that exogenous TGF-β 2 does not stimulate fracture healing under either stable or unstable mechanical conditions during the initial healing phase response in rabbit tibiae [16]. Park et al investigated the interaction between axial motion and exogenous TGF-β during tibial fracture repair in a white rabbit model following two injections of TGF-β 1. They noted that TGF-β 1 inhibited the normal development of
P Giannoudis et al peripheral callus when axial interfragmentary motion was present [50]. The effect of TGF-β in a rat tibia model was investigated by Nielsen et al who found increased callus formation and strength. The biomechanical properties were preserved in the group injected with 40 ng of TGF-β [48]. Kawaguchi et al examined the effect of locally applying recombinant human basic fibroblast growth factor (rhbFGF) and found that it facilitated bone union in rats with impaired as well as normal repairing to promote fracture healing by stimulating bone remodeling [47]. Nakajima et al reported that exogenous rhbFGF in a closed fracture of a longbone rat model had a capacity to enlarge the cartilaginous calluses, but not to induce faster healing [46]. In another study of fibroblast growth factor-2, Radomsky et al concluded that there were better biomechanical properties and more pronounced callus size, periosteal reaction, vascularity, and cellularity in the treated osteotomies than in the untreated controls [53]. Other investigators have reported that exogenous rhFGF-2 had an accelerating effect on the repair of metaphyseal fractures in rabbits [11] and was able to prevent nonunion in primates [35]. On the other hand, Bland et al found that the application of exogenous fibroblast growth factors -1 or -2 (FGF-1, FGF-2) to normally healing fractures of rabbit tibia did not significantly affect the rate of healing [4]. Schmidmaier et al investigated the effect of insulin-like growth factor-I (IGF-I) in a rat tibia model. He noted that insulin IGF-I had a greater stimulating effect on fracture healing than TGF-β 1. Applying both growth factors resulted in a significantly higher maximum load and torsional stiffness than only one of them. This group also showed an increase in remodeling of the fracture callus [56]. Similarly, another study reported that local application of IGFI and TGF-β 1 accelerated early cellular processes during fracture healing in a rat model [67]. Street et al assessed the importance of the presence of vascular endothelial growth factor (VEGF) in the local fracture environment. He reported that VEGF inhibition disrupted fracture repair. Exogenous VEGF enhanced blood vessel formation, ossification, and callus maturation in murine femur fractures, and promoted bony bridging of a rabbit radius segmental gap defect [59]. In a rat femora model, thrombin peptide (TP508) accelerated fracture repair and induced expression of early growth factors, inflammatory response modifiers, and angiogenesis-related genes [65]. Table 2 lists published studies on the use of growth factors and signaling molecules, other than BMPs, in animal fracture/osteotomy models.
Can we accelerate fracture healing? A critical analysis of the literature
Authors
Animal model
Fracture / Growth Factor osteotomy site
Lind et al. 199338
rabbit
tibia
Nielsen et al. 199446
rat
Critchlow et al. 199515
rabbit
S85
Controls
Comment
TGF-β (1 and 10 μg/day for yes 6 weeks in two groups)
yes
tibia
TGF-β (4 and 40 ng/ 2nd day until 40 days of healing in two groups)
yes
tibia
TGF-β 2 (60 or 600 ng on day 4 after fracture)
Increased maximal bending strength and callus formation in the groups receiving TGF-beta TGF-beta increased the callus formation and strength. Increased callus biomechanical properties in the group injected with 40 ng of TGF-beta. TGF-beta 2 does not stimulate fracture healing under either stable, or unstable, mechanical conditions during the initial healing phase. The local application of bFGF facilitated bone union in rats with impaired as well as normal repairing ability.
Kawaguchi et al. 199433
rat (normal fibula and streptozotocindiabetic) Bland et al. rabbit tibia 19954
Fracture stabilization
either yes or not
no
either yes or not
no
The application of FGF-1 or FGF-2 to normally healing fractures of the rabbit tibia does not have a significant effect on the rate of healing. bFGF promotes the fracture healing in dogs.
yes
Better biomechanical properties and more pronounced callus size, periosteal reaction, vascularity, and cellularity in the treated osteotomies than in the untreated controls. FGF-2 had an accelerating effect on the repair of metaphyseal fractures. FGF-2 accelerated fracture healing and prevented nonunion in primates.
rhbFGF (single dose)
3 μg of either FGF-1 or FGF-2 on day 4 after fracture
Nakamura et al. 199845 Radomsky et al. 199951
dog
tibia
rhbFGF (single dose of 200 μg)
baboon
fibula
FGF-2 or bFGF (4 mg/ml) in a single local injection
Chen et al. 200410 Kawaguchi et al. 200134 Nakajima et al. 2001
rabbit
tibia
yes
yes
nonhuman primate
ulna
FGF-2 (400 μg in a single local injection) FGF-2 (200 μg in a single local injection) hr bFGF 100 μg in a single local injection
yes
yes
Schmidmaier et al. 200354
rat
poly(D,L-lactide)-coated titanium K-wires with incorporated IGF-I and TGF-beta1, singly or in combination IGF-I and TGF-beta1 (Days 5, 10, and 15 after fracture) TGF-beta 1 (at the time of reduction, and a second dose was given 48 hours later).
yes
yes
yes
One group with locked and another with unlocked external fixators permitting axial motion yes VEGF inhibition disrupted fracture repair. Exogenous VEGF enhanced blood vessel formation, ossification, and callus maturation. yes TP508 accelerated fracture repair and induced expression of early growth factors, inflammatory response modifiers, and angiogenesis-related genes.
rat
44
Wildemann rat et al. 200363 Park et al. rabbit 200348
Street et al. 200257
mice
Wang et al. rat 200561
tibia
tibia
femur
VEGF
femur
TP508
yes
yes
Exogenous bFGF had a capacity to enlarge the cartilaginous calluses, but not to induce more rapid healing. IGF-I had a greater stimulating effect of on fracture healing than of TGF-beta1. Better biomechanical callus properties in the group with combination of both growth factors. Local application of IGF-I and TGF-beta1 accelerates early cellular processes during fracture healing. TGF-beta1 inhibited the normal development of peripheral callus when axial interfragmentary motion existed.
Table 2: Published studies regarding the use of growth factors and signalling molecules, other than BMPs, in animal fracture/osteotomy models.
S86
Discussion With the advances made in molecular medicine and molecular biology, our knowledge of the cellular and molecular events governing the fracture healing response has vastly expanded [52]. Several molecules have been identified that regulate the cascade of events in a time-dependent fashion leading to repair of bone tissue without scar formation [20]. This knowledge has led to a great deal of interest in the application of these molecules in the clinical setting, especially in the treatment of fracture nonunions. Nonunion following fractures continues to be a serious local complication, despite the advances made in our philosophy of fractures stabilization, implant developments, and biological fixation techniques [49]. In addition to nonunion, the administration of these molecules has been considered for a variety of other orthopedic circumstances, including stabilization of implant devices [13, 69], restoration of large segmental bone defects [15, 45], treatment of osteonecrosis of the femoral head [38], fusion of joints, cartilage regeneration [7, 14], augmentation of periprosthetic fractures, and acceleration of fracture healing, especially in patients at high risk of nonunion [28]. In this study, we have attempted to examine the current evidence on the efficacy of these molecules in accelerating the fracture healing response. To start with, we wished to examine the effect of BMPs. In vivo, BMPs regulate many aspects of embryonic development, including cartilage and bone formation, mesoderm patterning, and craniofacial and limb development, as well as postnatal bone formation and repair. They achieve these effects by regulating growth, differentiation, and apoptosis of various cell types, including mesenchymal cells, osteoblasts, chondroblasts, and neural and epithelial cells [54, 61, 64]. They act in an autocrine or paracrine manner [39]. The efficacy of BMPs in managing nonunions and substituting autogenous cancellous bone grafting to facilitate fusion of joints or the spine in general is well established [19, 36]. With regard to their potential to accelerate fracture healing in fresh fractures, several experimental and clinical studies have been performed. Both recombinant BMP-2 and BMP-7 have been tested with positive results in animal models. In goat tibia, rabbit ulna, and rat femur, acceleration of the healing response has been estimated to be as much as 30−40% [3, 9, 18, 22, 37, 66]. In monkeys, a combination of rhBMP-2 and alpha-BSM (bone substitute material) accelerated the healing process by 40% in a single percutaneous dose [57]. However, despite these favorable results, other factors that could exert a beneficial effect have to be taken into
P Giannoudis et al account such as the mechanical stimuli developed at the fracture site and the existence of biological variation amongst species. Contrary to the number of animal reports, very few studies have been performed in humans following fresh fractures. Those that exist have focused on open tibial fractures, a model that is known to be associated with a high risk of complications, particularly nonunion. Administration of rhBMP-2 has been associated with accelerated healing, a reduction in infection rates, fewer invasive procedures, less bone grafting, and a reduced frequency of secondary interventions from 46−26% [28, 60]. Similarly, application of rhBMP-7 was found to decrease the number of secondary interventions, with no adverse effects [42, 43]. While the evidence is more robust in animal studies, the currently available experience in humans is limited and therefore further studies are necessary to reach a definitive conclusion. Furthermore, the results obtained from the experimental studies should be interpreted with caution as they do not always correlate to humans. Besides BMPs other molecules have been considered for use as biological response modifiers to enhance or accelerate the fracture-healing process. TGF and FGF promote blood vessel formation and osteoblast proliferation [41, 44]. VEGF is of particular importance because of its ability to induce angiogenesis and to couple angiogenesis with bone formation and remodeling. Inhibition of VEGF blocks the angiogenic activity of bFGF and BMP-2 [12, 17]. Several studies have evaluated the effect of TGF β, IGF-1 and VEGF in a tibia rat model. Increased callus formation, enlarged cartilaginous calluses, increased remodeling, and acceleration of cellular processes, which all enhance the fracture healing response have been described [48, 59, 67]. The cost of these molecules has been a topic of vivid discussion. An economic model has been used to analyse the cost of treatment of nonunions using BMP-7 [33, 63]. Vinken A et al estimated a total cost per patient receiving BMP-7 of £8,797 compared to £9,084 for autograft, and £13,722 for the Ilizarov fixation technique. The authors concluded that costeffectiveness ratios of all three treatments were comparable [63]. Jones et al developed an economic model based on data from a clinical trial that had demonstrated improved clinical parameters (the rate of fracture healing, secondary interventions, infection rates) when 12 mg of recombinant human bone morphogenetic protein-2 (rhBMP-2) was used as an adjunct to intramedullary nailing in the treatment of open tibial fractures [33]. Their study estimated the cost of treatment with BMP-2 to the hospital at $13,733 and to the patient at $16,734, assuming no BMP-2 reimbursement. They concluded
Can we accelerate fracture healing? A critical analysis of the literature that the clinical benefits of rhBMP-2 used in first line treatment of open tibial fractures translate into reductions in medical costs over a two year period for hospitals and patients. Their estimates showed favourable total cost offsets (the proportion of the upfront rhBMP-2 price offset by other medical resource reductions) when 50% of the BMP-2 cost was reimbursed [33]. Considering the potential for adverse effects of BMP administration preclinical and clinical safety assessments have revealed little evidence of toxic effects and there have been few reports of adverse events related to their use. A small rate of immunological reaction following administration, resulting in antibody formation, has been observed in some patients, without clinical consequence, though the long-term consequences of this are unknown [30]. Perhaps the most obvious potential problem with these products is the induction of excessive bone at the site of application or induction of bone in ectopic sites [7, 62]. Although the majority of the experimental studies have shown promising results, two important factors, the ideal timing of administration and the most effective dose to be administered, have not been investigated in depth. Both of these factors could influence the effect exerted by any of the above molecules in accelerating fracture healing. Several studies have indicated that below a certain dose threshold, the healing response is not as efficient as with higher doses [16, 28, 34, 40, 48, 50]. This issue has been well proven by the administration of demineralized bone matrix (DBM). A significant positive linear relationship between the in vivo production of new bone and BMP-2, BMP-4, and TGF-β 1 levels in human DBM has been found, which suggests that the levels of BMPs and growth factors present in human DBM are clinically relevant [5]. The currently available results prove that the higher the DBM concentration, the higher the osteoinductive potential we get. Based on the studies by Han et al [29], Jung Yoo et al [68], and that by Atti [1], Kay and Vaughan [36] termed this phenomenon the “proportional osteoinduction of DBM graft materials”. In general terms, all the currently available studies support the view that manipulating the local fracture environment could lead to an enhanced and accelerated healing response. It is important to bear in mind, however, that the responses of the various biological models that have been tested differ enormously from the human response. Further clinical studies are now warranted to provide sufficient evidence that we can accelerate fracture healing to the extent that would outweigh the costs and the potential risks of utilizing biologically active molecules.
S87
The expanding clinical applications of BMPs, the anticipated discovery of new growth factors, the better understanding of the biological behavior of important cellular elements and of pathways of the healing process of tissues will offer novel treatment strategies in the enhancement of tissue regeneration in general.
Bibliography 1. Atti E, Abjornson C, Diegmann M, et al. High resolution X-ray computed tomography as a technique to study osteoinductivity of demineralised bone matrix. Proceedings of the NASS 18th Annual Meeting. Spine. 2003 3:120S. 2. Bauer TW, Muschler GF. Bone graft materials. An overview of the basic science. Clin Orthop. 2000 371:10−27. 3. Bax BE, Wozney JM, Ashhurst DE. Bone morphogenetic protein-2 increases the rate of callus formation after fracture of the rabbit tibia. Calcif Tissue Int. 1999 65(1):83−89. 4. Bland YS, Critchlow MA, Ashhurst DE. Exogenous fibroblast growth factors-1 and -2 do not accelerate fracture healing in the rabbit. Acta Orthop Scand. 1995 66(6):543−548. 5. Blum B, Moseley J, Miller L, et al. Measurement of bone morphogenetic proteins and other growth factors in demineralised bone matrix. Orthopedics. 2004 2791 Suppl: s161−165. 6. Boden SD, Kang J, Sandhu H, et al. Use of recombinant human bone morphogenetic protein-2 to achieve posterolateral lumbar spine fusion in humans: a prospective, randomized clinical pilot trial: 2002 Volvo Award in clinical studies. Spine. 2002 27(23):2662−2673. 7. Boden SD, Martin GI Jr, Morone MA, et al. Posterolateral lumbar intertransverse process spine arthrodesis with recombinant human bone morphogenetic protein 2/hydroxyapatitetricalcium phosphate after laminectomy in the nonhuman primate. Spine. 1999 24(12):1179-1185. 8. Bostrom MP. Expression of Bone Morphogenetic Proteins in Fracture Healing. Clin Orthop. 1998 355S:116−123. 9. Bouxsein ML, Turek TJ, Blake CA, et al. Recombinant human bone morphogenetic protein-2 accelerates healing in a rabbit ulnar osteotomy model. J Bone Joint Surg Am. 2001 83-A(8):1219−1230. 10. Brighton CT, Shaman P, Heppenstall RB, Esterhai et al. Tibial non-union treated with direct current, capacitive coupling, or bone graft. Clin Orthop. 1995 321:223−234. 11. Chen WJ, Jingushi S, Aoyama I, et al. Effects of FGF-2 on metaphyseal fracture repair in rabbit tibiae. J Bone Miner Metab. 2004 22(4):303−309. 12. Claffey KP, Abrams K, Shih SC, et al. Fibroblast growth factor 2 activation of stromal cell vascular endothelial growth factor expression and angiogenesis. Lab Invest. 2001 81(1):61−75. 13. Cook SD, Barrack RL, Patron LP, et al. Osteogenic protein1 in knee arthritis and arthroplasty. Clin Orthop. 2004 428:140−145. 14. Cook SD, Dalton JE, Tan EH, et al. In vivo evaluation of recombinant human steogenic protein (rhOP-1) implants as a bone graft substitute for spinal fusions. Spine. 1994 19(15):1655−1663.
S88 15. Cook SD, Wolfe MW, Salkeld SL et al. Effect of recombinant human osteogenic protein-1 on healing of segmental defects in non-human primates. J Bone Joint Surg [Am]. 1995 77(5):734−750. 16. Critchlow MA, Bland YS, Ashhurst DE. he effect of exogenous transforming growth factor-beta 2 on healing fractures in the rabbit. Bone. 1995 16(5):521−527. 17. Deckers MM, van Bezooijen RL, van der Horst G, et al. Bone morphogenetic proteins stimulate angiogenesis through osteoblast-derived vascular endothelial growth factor A. Endocrinology. 2002 143(4):1545−1553. 18. den Boer FC, Bramer JA, Blokhuis TJ, et al. Effect of recombinant human osteogenic protein-1 on the healing of a freshly closed diaphyseal fracture. Bone. 2002 31(1):158−164. 19. Dimitriou R, Dahabreh Z, Katsoulis E, et al. Application of recombinant BMP-7 on persistent upper and lower limb nonunions. Injury. 2005 36 Suppl 4:S51−9. 20. Dimitriou R, Tsiridis E, Giannoudis PV. Current concepts of molecular aspects of bone healing. Injury. 2005 36(12):1392−1404. 21. Dong Y, Canalis E. Insulin-like growth factor (IGF) I and retinoic acid induce the synthesis of IGF-binding protein 5 in rat osteoblastic cells. Endocrinology. 1995 136(5):2000−2006. 22. Einhorn TA, Majeska RJ, Mohaideen A, et al. A single percutaneous injection of recombinant human bone morphogenetic protein-2 accelerates fracture repair. J Bone Joint Surg Am. 2003 85−A(8):1425−1435. 23. Fakhry A, Ratisoontorn C, Vedhachalam C, et al. Effects of FGF-2/-9 in calvarial bone cell cultures: differentiation stagedependent mitogenic effect, inverse regulation of BMP-2 and noggin, and enhancement of osteogenic potential. Bone. 2005 36(2):254−266. 24. Friedlaender GE, Perry CR, Cole JD, et al. Osteogenic protein1 (bone morphogenetic protein-7) in the treatment of tibial nonunions: A prospective, randomized clinical trial comparing rhOP-1 with fresh bone autograft. J Bone Joint Surg [Am]. 2001 83:151−158. 25. Gazzerro E, Pereira RC, Jorgetti V, et al. Skeletal overexpression of gremlin impairs bone formation and causes osteopenia. Endocrinology. 2005 146(2):655−665. 26. Giannoudis PV, Pountos I. Tissue regeneration. The past, the present and the future. Injury. 2005 36 Suppl 4:S2−5. 27. Giannoudis PV, Tzioupis C. Clinical applications of BMP-7: the UK perspective. Injury. 2005 36 Suppl 3:S47−50. 28. Govender S, Csimma C, Genant HK, et al. BMP-2 Evaluation in Surgery for Tibial Trauma (BESTT) Study Group. Recombinant human bone morphogenetic protein-2 for treatment of open tibial fractures: a prospective, controlled, randomized study of four hundred and fifty patients. J Bone Joint Surg Am. 2002 84−A(12):2123−34. 29. Han B, Tang B, Nimni M. A quantitative and sensitive in vitro assay of osteoinductive activity of demineralized bone matrix. J Orthop Res. 2003 21(4):648−654. 30. Harwood PJ, Giannoudis PV. Application of bone morphogenetic proteins in orthopaedic practice: their efficacy and side effects. Expert Opin Drug Saf. 2005 4(1):75−89. 31. Healy WL, Jupiter JB, Kristiansen TK, et al. Nonunion of the proximal humerus. J Orthop Trauma. 1990 4:424−431.
P Giannoudis et al 32. Johnson EE, Urist MR, Finerman GA. Resistant nonunions and partial or complete segmental defects of long bones. Treatment with implants of a composite of human bone morphogenetic protein (BMP) and autolyzed, antigen-extracted, allogeneic (AAA) bone. Clin Orthop. 1992 277:229−237. 33. Jones AL, Swiontkowski MF, Polly DW, et al. Use of rhBMP-2 in the treatment of open tibial shaft fractures: Do improved outcomes outweigh the additional expense of rhBMP-2? [abstract]. OTA 20th Annual Meeting. 2004. 34. Kawaguchi H, Kurokawa T, Hanada K et al. Stimulation of fracture repair by recombinant human basic fibroblast growth factor in normal and streptozotocin-diabetic rats. Endocrinology. 1994 135(2):774−781. 35. Kawaguchi H, Nakamura K, Tabata Y, et al. Acceleration of fracture healing in nonhuman primates by fibroblast growth factor-2. J Clin Endocrinol Metab. 2001 86(2):875−880. 36. Kay JF, Vaughan LM. Proportional osteoinduction of DBM graft materials. IsoTis OrthoBiologics, Inc. Data on file. 37. Li RH, Bouxsein ML, Blake CA, et al. rhBMP-2 injected in a calcium phosphate paste (alpha-BSM) accelerates healing in the rabbit ulnar osteotomy model. J Orthop Res. 2003 21(6):997−1004. 38. Lieberman JR, Conduah A, Urist MR. Treatment of osteonecrosis of the femoral head with core decompression and human bone morphogenetic protein. Clin Orthop. 2004 429:139−145. 39. Lieberman JR, Daluiski A, Einhorn TA. The role of growth factors in the repair of bone. Biology and clinical applications. J Bone Joint Surg [Am]. 2002 84-A(6):1032−1044. 40. Lind M, Schumacker B, Soballe K, et al. Transforming growth factor-beta enhances fracture healing in rabbit tibiae. Acta Orthop Scand. 1993 64(5):553−556. 41. Mandracchia VJ, Nelson SC, Barp EA. Current concepts of bone healing. Clin Podiatr Med Surg. 2001 8(1):55−77. 42. McKee MD and the Canadian Orthopaedic Trauma Society. The effect of human recombinant bone morphogenic protein (RHBMP-7) on the healing of open Tibial shaft fractures: results of a multi-center, prospective, randomized clinical trial. Orthopaedic Trauma Association. 2002 Annual Meeting, Toronto, Ontario, Canada, October 12; Paper 45. 43. McKee MD, Schemitsch EH, Waddell JP, et al. The effect of human recombinant bone morphogenic protein (rhBMP-7) on the healing of open tibial shaft fractures: results of a multicenter, prospective, randomized clinical trial. Read at the Annual Meeting of the American Academy of Orthopaedic Surgeons; Feb 5−9 2003; New Orleans, LA. 44. Midy V, Plouet J. Vasculotropin/vascular endothelial growth factor induces differentiation in cultured osteoblasts. Biochem Biophys Res Commun. 1994 199(1):380−386. 45. Mont MA, Jones LC, Elias JJ, et al. Strut-autografting with and without osteogenic protein-1: a preliminary study of a canine femoral head defect model. J Bone Joint Surg [Am]. 2001 83−A(7):1013−1022. 46. Nakajima F, Ogasawara A, Goto K, et al. Spatial and temporal gene expression in chondrogenesis during fracture healing and the effects of basic fibroblast growth factor. J Orthop Res. 2001 19(5):935−944.
Can we accelerate fracture healing? A critical analysis of the literature 47. Nakamura T, Hara Y, Tagawa M, et al. Tamura M, Yuge T, Fukuda H, Nigi H. Recombinant human basic fibroblast growth factor accelerates fracture healing by enhancing callus remodeling in experimental dog tibial fracture. J Bone Miner Res. 1998 13(6):942−949. 48. Nielsen HM, Andreassen TT, Ledet T, et al. Local injection of TGF-beta increases the strength of tibial fractures in the rat. Acta Orthop Scand. 1994 65(1):37−41. 49. Papakostidis C, Grotz MR, Papadokostakis G, et al. Femoral Biologic Plate Fixation. Clin Orthop Relat Res. 2006 May 11; [Epub ahead of print]. 50. Park SH, O›Connor KM, McKellop H. Interaction between active motion and exogenous transforming growth factor Beta during tibial fracture repair. J Orthop Trauma. 2003 17(1):2−10. 51. Paterson DC, Lewis GN, Cass CA. Treatment of delayed union and nonunion with an implanted direct current stimulator. Clin Orthop. 1980 148:117−128. 52. Pountos I, Giannoudis PV. Biology of mesenchymal stem cells. Injury. 2005 36 Suppl 3:S8−S12. 53. Radomsky ML, Aufdemorte TB, Swain LD, et al. Novel formulation of fibroblast growth factor-2 in a hyaluronan gel accelerates fracture healing in nonhuman primates. J Orthop Res. 1999 17(4):607−614. 54. Sakou T. Bone morphogenetic proteins: from basic studies to clinical approaches. Bone. 1998 22:591−603. 55. Schaden W, Fischer A, Sailler A. Extracorporeal shock wave therapy of nonunion or delayed osseous union. Clin Orthop. 2001 387:90−94. 56. Schmidmaier G, Wildemann B, Gabelein T, et al. Synergistic effect of IGF-I and TGF-beta1 on fracture healing in rats: single versus combined application of IGF-I and TGF-beta1. Acta Orthop Scand. 2003 74(5):604−610. 57. Seeherman HJ, Bouxsein M, Kim H, et al. Recombinant human bone morphogenetic protein-2 delivered in an injectable calcium phosphate paste accelerates osteotomy-site healing in a nonhuman primate model. J Bone Joint Surg Am. 2004 86−A(9):1961−72. 58. Shen HC, Peng H, Usas A et al. Structural and functional healing of critical-size segmental bone defects by transduced muscle-derived cells expressing BMP4. J Gene Med. 2004 6(9):984−991. 59. Street J, Bao M, deGuzman L, et al. Bunting S, Peale FV Jr, Ferrara N, Steinmetz H, Hoeffel J, Cleland JL, Daugherty A, van Bruggen N, Redmond HP, Carano RA, Filvaroff EH. Vascular endothelial growth factor stimulates bone repair by promoting angiogenesis and bone turnover. Proc Natl Acad Sci U S A. 2002 99(15):9656−9661. 60. Swiontkowski MF, Aro HT, Donell S, et al. Recombinant human bone morphogenetic protein-2 in open tibial fractures. A subgroup analysis of data combined from two prospective randomized studies. J Bone Joint Surg Am. 2006 88(6):1258−65. 61. Termaat MF, Den Boer FC, Bakker FC, et al. Bone morphogenetic proteins. Development and clinical efficacy in the treatment of fractures and bone defects. J Bone Joint Surg [Am]. 2005 87(6): 1367−1378.
S89
62. Vaccaro AR, Patel T, Fischgrund J et al. A pilot safety and efficacy study of OP-1 putty (rhBMP-7) as an adjunct to iliac crest autograft in posterolateral lumbar fusions. Eur Spine J. 2003 12(5):495-500. 63. Vinken A, van Engen A, Albert J, et al. The cost-effectiveness of Osigraft® (Osteogenic Protein 1) in the treatment of tibial nonunions in the UK and Germany [poster presentation]. 6th EFFORT Congress, 2003. 64. Wan M, Cao X. BMP signalling in skeletal development. Biochem Biophys Res Commun. 2005 328(3):651−7. 65. Wang H, Li X, Tomin E, et al. Thrombin peptide (TP508) promotes fracture repair by up-regulating inflammatory mediators, early growth factors, and increasing angiogenesis. J Orthop Res. 2005 23(3):671−679. 66. Welch RD, Jones AL, Bucholz RW. Effect of recombinant human bone morphogenetic protein-2 on fracture healing in a goat tibial fracture model. J Bone Miner Res. 1998 13(9):1483−1490. 67. Wildemann B, Schmidmaier G, Ordel S, et al. Cell proliferation and differentiation during fracture healing are influenced by locally applied IGF-I and TGF-beta1: comparison of two proliferation markers, PCNA and BrdU. J Biomed Mater Res B Appl Biomater. 2003 65(1):150−156. 68. Yoo J, Birkedal J, Changs S, et al. Spinal arthrodesis using a demineralized bone/hyaluronan matrix and bone marrow. Proceedings of the NASS 18th Annual Meeting. Spine J. 2003 3: 143S. 69. Zhang R, An Y, Toth CA, et al. Osteogenic protein-1 enhances osteointegration of titanium implants coated with periapatite in rabbit femoral defect. J Biomed Mater Res. 2004 71B(2):408−413.
Correspondence address Prof P Giannoudis Department of Trauma & Orthopaedics, St James’s University Hospital, Beckett Street, Leeds, LS9 7TF, United Kingdom e-mail: [email protected]
This paper has been written entirely by the authors, and has received no external funding. The authors have no significant financial interest or other relationship.