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Context: Icariin has attracted increasing attention because of its wide variety of pharmacological effects., Objective: This study investigates whether icariin could promote fracture healing in young and old rats and its mechanisms., Materials and Methods: A Wistar rat model for the tibia fracture in relatively young and old rats, respectively, was established. The rats were divided into four groups: model group, L-icariin (50 mg/kg icariin), M-icariin (100 mg/kg icariin) and H-icariin (200 mg/kg icariin), and intragastric administration of icariin was performed for 10 days or 20 days. In addition, isolated and cultured rat bone mesenchymal stem cells (rBMSCs) from young and old rats were cultured with 5% and 20% of icariin-containing serum, respectively, then cell viability and alkaline phosphatase (ALP) activity were measured., Results: Icariin administration induced the expression of Runx2, Osterix, BMP-2, p-Smad5 and osteocalcin secretion (young rats: model: 2.50 ± 0.71; L-icariin: 10.10 ± 1.55; M-icariin: 24.95 ± 2.19; H-icariin: 36.80 ± 2.26; old rats: model: 1.55 ± 0.49; L-icariin:6.55 ± 0.50; M-icariin: 15.00 ± 0.85; H-icariin:20.50 ± 2.27) at the fracture site, and increased the levels of bone formation markers (OC, BAP, NTX-1 and CTX-1) in a dose-dependent manner. In vitro , icariin treatment promoted rBMSC viability, increased ALP activity and the expression of BMP-2/Smad5/Runx2 pathway proteins., Discussion and Conclusions: Icariin may accelerate fracture healing by activating the BMP-2/Smad5/Runx2 pathway in relatively young and old rats. The research on the mechanism of icariin to promote fracture healing can provide a theoretical basis for the clinical application and promotion of icariin.

Background: Patients with chronic obstructive pulmonary disease have a high prevalence of osteoporosis, and different osteoporosis drugs are used to prevent fractures in these patients. Although the overall incidence of complete or incomplete, atypical femoral fracture (AFF) is low, long-term use of antiresorptive agents is associated with an increased risk of developing AFF. Methods: We present a patient with chronic obstructive pulmonary disease with recurrent symptoms of an incomplete AFF who had been treated with glucocorticoids, and sequentially with alendronate, zoledronic acid, strontium ranelate, raloxifene, denosumab and finally with teriparatide. The first episode occurred before osteoporosis therapies, the second after bisphosphonate treatments, and the third under denosumab. Results: Although her symptoms resolved along with gradually healing of fracture lines after conservative treatment without surgical intervention, progressive varus deformity of the proximal femur may have contributed to recurrence of AFF. Conclusion: Early treatment with anabolic agents and prophylactic fixation of incomplete AFF may alleviate symptoms and prevent recurrences.

Introduction: The need for fracture healing enhancement for the management of fracture complications such as non-union and for the achievement of early function in fracture patients is constantly increasing. Therefore, the development and evaluation of novel pharmaceutical agents is mandatory in order to accelerate the process and increase bone union rates., Areas Covered: This review summarizes the most recent knowledge on the pharmacological enhancement of fracture repair. It provides a synopsis of the most important preclinical and clinical studies published over the past five years on long bone fracture healing., Expert Opinion: To date, limited drugs seem to have the potential for clinical use in fracture healing enhancement and the field is progressing very slowly. Among anti-osteoporotic drugs, only PTH and anti-sclerostin antibodies have such a potential but further research is needed before clinical use. The same applies also to BMPs, the use of which still carries major drawbacks that should be overcome before their widespread clinical utilization. Other drugs and growth factors, such as statins, VEGF, FGF, EPO, could be future key players in fracture healing but evidence is still lacking. Further in depth understanding of the healing process is essential in order to identify novel effective pharmacological agents.

Introduction: Daily subcutaneous injections of parathyroid hormone (PTH), and its synthetic peptide fragment, teriparatide (PTH 1-34, TPTD), have a net anabolic effect on bone and prevent osteoporotic fractures. TPTD is currently approved for this indication worldwide. Because of the anabolic effect, there is an interest in a role for TPTD (and, where available, human PTH 1-84) in improving bone healing after a fracture. PTH has been studied in animal fracture healing models and in a limited number of human trials. We have reviewed current literature regarding possible mechanisms and efficacy for PTH and TPTD to improve the healing process in the setting of various types of fractures., Areas Covered: Our review focuses first on the role of PTH in normal bone. We then discuss mechanisms of normal bone healing as well as delayed and impaired fracture healing. We summarize pertinent animal data and then review human studies utilizing PTH or TPTD for fracture healing. In particular, we examine unique situations including osteoporotic fractures, diabetes, stress fractures, delayed or poor healing and combination with bisphosphonate therapy., Expert Opinion: Available data indicate there is likely an important role for TPTD and PTH in promoting fracture healing in selected patients, but more clinical trial data are needed.

Introduction: Bone morphogenetic proteins are multi-functional growth factors, which play an important role in embryonic development and cellular functions. Among several molecules in this family, BMP-2 and BMP-7 are currently being used in the clinical setting. Main clinical targets include the treatment of non-union, open fractures and spinal fusion. Their use has not been without complications, one of which might be a carcinogenic effect., Areas Covered: The authors offer a comprehensive review of the existing literature on the clinical studies analysing the role of bone morphogenetic proteins (BMPs) on carcinogenesis. The authors analyse the available literature and describe potential signalling pathways that can be affected as per available experimental in vitro and in vivo models., Expert Opinion: The available experimental data and clinical evidence are rather inadequate to allow any safe scientific conclusions. Clinical studies provide incomplete evidence to support the hypothesis that BMPs are carcinogenic. The available literature has several limitations including incomplete documentation, unreported data and inhered bias as a large number of trials have been funded by the industry. The need of well-structured studies is essential to address these safety concerns.

We evaluated the effects of Ankaferd Blood Stopper (ABS) and routine antibiotic prophylaxis (AP) on early healing of bone defects in diabetic rats. We used 48 rats in the study. Diabetes was induced in 24 rats using streptozotocin; the remaining 24 healthy untreated rats served as controls. Twelve of the diabetic rats and 12 of the healthy rats were treated with AP for 3 days before surgery. Bilateral bone defects were created in the mandible of all animals. ABS was applied to the defects on the left sides of the mandibles, while nothing was applied to the right sides. Animals were sacrificed on days 7 and 14 after operation and examined for histopathology and by stereology. The volume of newly formed bone was significantly less in the diabetic rats on both days 7 and 14. Local administration of ABS significantly increased the mean volume of newly formed bone in both diabetic and nondiabetic rats at days 7 and 14. No significant difference in new bone formation was found between AP and ABS treatment in diabetic rats. Both AP and local administration of ABS have beneficial effects on bone healing in diabetic animals.

Objective: To investigate mechanisms behind the faster rehabilitation of limb fractures when associated with traumatic brain injury (TBI)., Methods: New Zealand rabbits were divided into TBI group and sham-operation group for four studies as follows: (1) blood and cerebrospinal fluid (CSF) were drawn on days 1, 3, and 7 to demonstrate changes in serum leptin, growth hormone (GH), insulin-like growth factor 1 (IGF-1), and CSF leptin; (2) bone defection was created by drilling in the tibial bone and either leptin or normal saline was injected into rabbit's cerebellomedullary cistern. X-ray was taken at 1 days, 2 weeks, and 5 weeks and evaluated by criteria to determine rate of bone healing; (3) FITC-labeled rabbit leptin was injected into TBI and sham-operation groups, and frozen sections of rabbit brain were observed to identify differences in central nervous system (CNS) leptin by fluorescence; (4) polymerase chain reaction (PCR) was used to evaluate the expression of leptin production by brain tissue., Results: Serum and CSF leptin, GH, and IGF-1 concentrations were found to be higher in the TBI group than the sham-operation group at days 1, 3, and 7 (P<0·05). CSF leptin of the TBI group was positively correlated with serum leptin on day 1 (P<0·05), and positively correlated with GH and IGF-1 on days 3 and 7 (P<0·05). X-ray criteria demonstrated that leptin administration caused significantly faster healing calluses at 3 and 5 weeks as compared to control animals (P<0·05). FITC-labeled leptin study demonstrated that TBI animals had stronger expression of leptin in the brain than sham-operated animals. However, PCR of brain tissue leptin showed no significant differences between TBI and sham-operated animals in the expression of leptin., Conclusions: Our study suggests that increased CSF leptin, likely from blood-brain barrier breakdown, combined with elevated serum GH and IGF-1 after TBI, leads to accelerated fracture healing.

This article is concerned with the assessment of the causal effect of a treatment on a variable that is defined only in the subset of patients who experience a specific event. In this case, the treatment can affect the variable directly, as well as indirectly through its effect on the occurrence and severity of the event. In this article we describe the pure (direct) and hybrid (direct and indirect) causal effects and methods typically used to assess them. When the treatment has a strong effect on the occurrence of the event, we found no method with adequate properties to address the pure causal effect; this remains an intractable statistical problem with no clear solution. Among the valid methods for assessment of the hybrid causal effect, power depends greatly on whether the treatment effect is primarily on the occurrence of the event or on the variable of interest.

The biology of fracture healing is better understood than ever before, with advancements such as the locking screw leading to more predictable and less eventful osseous healing. However, at times one's intrinsic biological response, and even concurrent surgical stabilization, is inadequate. In hopes of facilitating osseous union, bone grafts, bone substitutes and orthobiologics are being relied on more than ever before. The osteoinductive, osteoconductive and osteogenic properties of these substrates have been elucidated in the basic science literature and validated in clinical orthopaedic practice. Furthermore, an industry built around these items is more successful and in demand than ever before. This review provides a comprehensive overview of the basic science, clinical utility and economics of bone grafts, bone substitutes and orthobiologics.

Introduction: The biological enhancement of fracture healing may prevent complications such as non-union and revision surgery. Sclerostin is produced by osteocytes and binds to the LRP5/6 receptor. This inhibits the Wnt signalling pathway and thereby reduces bone formation., Areas Covered: Targeted deletion of the sclerostin gene has been found to enhance bone formation and fracture healing in rodent models. A number of in vivo studies have investigated the effect of sclerostin antibody on bone density with promising results. It also has an ability to promote fracture healing, screw fixation and metaphyseal bone healing in vivo. Early clinical studies have also demonstrated that it can increase bone mineral density, whilst being safe and well tolerated by patients., Expert Opinion: The data support the further investigation of this agent for the promotion of fracture healing. We aim to review the current literature and present an update on the use of this agent to promote bone formation and healing.

Introduction: The biological process of fracture healing is complex with influences that are both patient-dependent and related to the trauma experienced and stability of the fracture. Fracture healing complications negatively affect the patient's quality of life, even more when fractures occur in the elderly osteoporotic patients., Areas Covered: In the polytherapy for bone regeneration, a high success rate was obtained with the use of growth factors, osteogenic cells, and osteoconductive factors. There have been high expectations that treatment with drugs active on bone remodeling would be efficient for acceleration of fracture healing. A literature search was undertaken using wording like "drug or pharmacology of fracture healing." This report will review the systemic pharmacological agents for which clinical trials documenting their efficacy on bone healing have been carried out or are underway., Expert Opinion: At present the use of systemic pharmacological agents to enhance fracture healing in the clinical setting is still controversial. However, future clinical trials will offer the possibility to obtain data that will make possible the registration of a drug as a "healer."

Introduction: Over 39,000 diabetic patients are surgically treated for trauma and orthopaedic injuries annually in the UK, yet the effects of diabetic medications on the skeletal system is an under researched and under acknowledged field., Areas Covered: This review covers all English language novel experimental data reports investigating the effects of the main classes of diabetic drugs on the skeletal system, specifically their effects on fracture healing, located through the literature search engines Medline and Web of Science., Expert Opinion: Post-surgical gylcaemic control is paramount in insulin-controlled type 1 diabetic patients. Data on pharmacological control compounds used in type 2 diabetes are limited. Reports to date indicate thiazolidinediones to exert anti-osteogenic effects, in contrast to the observed osteogenic effects of biguanides. Ongoing research is desirable to guide future clinical recommendations.

Introduction: Recent evidence suggests that antibiotics exert direct effects on bone at a cellular level, disrupting mitochondrial function and cell activity. This comprehensive literature review aims to evaluate evidence for the effects of antibiotics and antimicrobials on bone and discuss the clinical implications., Areas Covered: A literature search was conducted on electronic databases covering a period from 1969 to 2010. Studies were included if they reported in vivo and in vitro experimental findings regarding the use of antibiotics and synthetic antibacterials in both animals and humans, focusing on bone cell function and especially fracture repair., Expert Opinion: Current research suggests that these negative results could be due to direct effects of antibiotics on mitochondrial physiology within mammalian cells. Treatment doses of antibiotics, especially those released from topical delivery systems such as bone cements, result in antibiotic concentrations thousands of times higher than those required to inhibit bacterial growth. Our findings suggest a need to develop current antibiotic delivery systems to elute sufficient doses to inhibit bacterial growth without negative effects on bone physiology and fracture repair processes.

Introduction: Bone healing is a complex cascade of events that involves the proliferation and differentiation of osteoblastic cells under the influence of signals from growth factors, cytokines and mechanical loading. Several medications have been found to interact negatively with this process including cytostatics, NSAIDs and corticosteroids; however, the effect of antibiotics on bone repair processes remains obscure., Areas Covered: The authors offer a comprehensive review of the existing literature on the in vivo and in vitro effect of antibiotics on bone, bone cells and fracture healing. The authors describe the pharmacokinetic characteristics of antibiotics after parenteral administration as well as their levels when applied locally together with a delivery vehicle., Expert Opinion: The available experimental data and clinical evidence are rather limited to allow safe conclusions. In vitro studies indicate that high doses administered after systemic administration have little or no direct effect on bone cells. Further studies are desirable to define the effect of higher or prolonged concentrations on bone biology and especially that of high concentrations released by locally implanted antibiotic-delivery systems, that is, bone cement, spacers and beads.

Background: The effects of cyclooxygenase (COX) inhibition on fracture healing are insufficiently documented, and the aim of this study was to evaluate the effects of nonspecific and specific COX-2 inhibition in the early phase of fracture healing., Methods: Thirty rats were randomized in three groups. A diaphyseal fracture was performed and stabilized by intramedullary nailing. In group A parecoxib in a dose of 1 mg/kg body weight/day was given prior to surgery and daily for seven days; in group B diclofenac 2 mg/kg body weight/day was given; and in group C the same amount of saline was given. Blood samples were harvested at 7 and 30 days postoperatively and analyzed for active medications. At 30 days the rats were sacrificed, and the fractures were examined for bone mineralization and tested mechanically., Results: The fractures healed by the production of callus. Plasma concentrations at seven days of medication revealed therapeutic levels of parecoxib, valdecoxib, and diclofenac. There were no significant differences in bone mineralization or mechanical characteristics between the three groups at 30 days postfracture., Conclusion: This study indicates that nonspecific or specific COX-2 inhibitors in therapeutic doses during seven days after fracture do not significantly influence bone healing.

Background: Platelet-derived growth factor (PDGF) has been shown in vivo to increase bone formation and supplement fracture healing, and may have a role as a therapeutic agent in the treatment of bone loss and fracture healing in humans., Objective: A comprehensive review of the recent literature on the effect of PDGF on bone mineral density and fracture healing., Methods: In vitro and in vivo evidence was systematically collected using medical search engines MEDLINE/OVID (1950 to March 2008) and EMBASE (1980 to March 2008) databases., Results/conclusion: Evidence to date suggests that PDGF-BB, and to a lesser extent PDGF-AA, may have potential therapeutic use in the treatment of osteoporosis and bone healing in humans. Additionally, by targeting alpha-receptors on osteoblasts, a potential anabolic effect on bone metabolism in humans can be anticipated; however, more research needs to be done to assess the role of beta-receptors in human bone.

Background: The role of growth hormone (GH) in augmenting fracture healing has been postulated for over half a century. GH has been shown to play a role in bone metabolism and this can be mediated directly or indirectly through IGF-I., Objectives: The use of GH was evaluated as a possible therapeutic agent in augmenting fracture healing., Method: A literature search was undertaken on GH and its effect on bone fracture healing primarily using MEDLINE/OVID (1950 to January 2009). Key words and phrases including 'growth hormone', 'insulin like growth factor', 'insulin like growth factor binding protein', 'insulin like growth factor receptor', 'fracture repair', 'bone healing', 'bone fracture', 'bone metabolism', 'osteoblast' and 'osteoclast' were used in different combinations. Manual searches of the bibliography of key papers were also undertaken., Results: Current evidence suggests a positive role of GH on fracture healing as demonstrated by in vitro studies on osteoblasts, osteoclasts and the crosstalk between the two. Animal studies have demonstrated a number of factors influencing the effect of GH in vivo such as dose, timing and method of administration. Application of this knowledge in humans is limited but clearly demonstrates a positive effect on fracture healing. Concern has been raised in the past regarding the safety profile of the pharmacological use of GH when used in critically ill patients., Conclusion: The optimal dose and method of administration is still to be determined, and the safety profile of this novel use of GH needs to be investigated prior to establishing its widespread use as a fracture-healing agent.

Background: Using agonists that selectively stimulate PGE2 receptors, the adverse effects that have limited the clinical utility of PGE2 can be avoided and there may be potential for their use as therapeutic agents in the treatment of bone loss in humans., Objective: A comprehensive review of the recent literature on the effect of prostaglandins and their agonists on bone mineral density and fracture healing., Methods: In vitro and in vivo evidence was collected using medical search engines MEDLINE (1950 to March 2008) and EMBASE (1980 to March 2008) databases., Results/conclusion: EP4 receptors have been identified in human osteoblast cell lines and have also been shown to activate osteoblast directly and osteoclast indirectly via osteoblastic activation. Although there are strong in vitro and in vivo collective data indicating that EP2 receptors may have a role in mediating the anabolic effects of PGE2 on bone, to date no functional EP2 receptors have been identified on human osteoblasts or osteoclasts. This suggests that PGE2 effect on bone formation and resorption in humans may be governed by activation of the EP4 receptor on osteoblasts. Selective EP4 receptor agonists may therefore provide therapeutic potential for systemic use in the treatment of osteoporosis and fracture healing. Further studies need to be carried out in order fully elicit the role of EP2 receptor agonists in fracture healing and bone formation in humans.

Background: Statins are 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitors and have been shown to possess anti-lipidaemic properties effective in lowering cholesterol. Recent evidence has suggested beneficial pleiotropic effects, including that of fracture healing, alongside its widely accepted ability to reduce the incidence of cardiovascular disease., Objectives: A comprehensive review of the recent literature on the effect of statins on bone mineral density and fracture healing., Methods: Medline/Ovid and EMBASE search and manual search of bibliography of key papers, on the effects of statins on bone metabolism including in vitro and in vivo studies, as well as clinical trials on the effects of statins on bone mineral density and fracture risk., Results/conclusions: There is robust in vitro and in vivo evidence to suggest the anabolic effects of statins on bone metabolism. Although evidence in patients with osteoporosis is conflicting, several studies have shown that the use of statins is associated with increases in bone mass density and reduction in fracture risk. Conflicting studies identified may be due to different routes of administration, types of statins employed and low doses used. Taken together, there is strong evidence to suggest that statins have beneficial effects on fracture healing that would support further clinical trials investigating such properties.

Background: beta-Adrenergic receptor antagonists (beta-blockers) have a well-recognised antihypertensive action that is mediated through a reduction in cardiac output and in the release of renin from the kidneys and inhibition of the action of endogenous catecholamines on beta-adrenergic receptors. This class of drugs has been shown to reduce the incidence of cardiovascular disease. Recent evidence suggests that beta-blockers may also have an effect on bone structure, metabolism and fracture healing., Objective: This paper reviews in vitro and in vivo data that suggest beta-blockers have primarily an anabolic effect on bone metabolism., Results: The sympathetic nervous system has a catabolic effect on bone, and in vitro studies have shown that adrenergic agonists stimulate bone resorption. The beta-blocker propranolol has been shown to increase bone formation in ovariectomised female rats. Also, recent observational clinical studies provide evidence to show that beta-blockers are associated with reduction in fracture risk in both men and women., Conclusion: Although there are some controversial studies, most research concludes that beta-blockers show promise in the treatment of osteoporosis and fracture healing.

Distal tibial fractures are rare and difficult to treat because the bones are subcutaneous. External fixation is commonly used, but the method often results in delayed union. The aim of the present study was to find out the factors that affect fracture union in tibial pilon fractures. For this purpose, prospective data collection of tibial pilon fractures was carried out in 1998-2004, resulting in 159 fractures, of which 83 were treated with external fixation. Additionally, 23 open tibial fractures with significant > 3 cm bone defect that were treated with a staged method in 2000-2004 were retrospectively evaluated. The specific questions to be answered were: What are the risk factors for delayed union associated with two-ring hybrid external fixation? Does human recombinant BMP-7 accelerate healing? What is the role of temporary ankle-spanning external fixation? What is the healing potential of distal tibial bone loss treated with a staged method using antibiotic beads and subsequent autogenous cancellous grafting compared to other locations of the tibia? The following risk factors for delayed healing after external fixation were identified: post-reduction fracture gap of >3 mm and fixation of the associated fibula fracture. Fracture displacement could be better controlled with initial temporary external fixation than with early definitive fixation, but it had no significant effect on healing time, functional outcome or complication rate. Osteoinduction with rhBMP-7 was found to accelerate fracture healing and to shorten the sick leave. A staged method using antibiotic beads and subsequent autogenous cancellous grafting proved to be effective in the treatment of tibial bone loss. Healing potential of the bone loss in distal tibia was at least equally good as in other locations of the tibia.

Parathyroid hormone (PTH) has become the most widely studied hormone with regard to its administration to various species and their respective skeletal responses. Beyond its affirmative effect in osteoporosis treatment, systemic PTH administration seems to stimulate bone formation in the fracture healing process. According to preclinical experimental studies, once-daily administration of PTH enhances the morphometric and mechanical properties of fracture calluses and accelerates the normal fracture healing. Its anabolic effect is obvious even in low doses, as well as in cases of implant fixation and distraction osteogenesis. There is little evidence of toxic effects and there are only a few reports of adverse events related to its use. The incidence of bone neoplasms in animal studies depends on the dose and duration of treatment. However, it is not prognostic of an equivalent risk potential of carcinogenesis in humans. In summary, the clinical promise of parathyroid hormone is very high and a positive effect in fracture healing should be anticipated.

Whereas continuous exposure to PTH results in bone resorption, administration at intermittent doses results in bone formation by increasing osteoblast number and activity. The anabolic action of PTH has also been demonstrated in clinical trials, in which PTH increased the bone mass and reduced fracture rate in patients with osteoporosis. In animal models of fracture healing and fixation of orthopedic implants, PTH increases the bone density in a dose-dependent manner, leading to faster repair and better fixation. The effect appears to be stronger on the new forming bone than on pre-existing bone. Based on these preclinical studies, we suggest that intermittent PTH treatment may also benefit fracture healing and implant fixation in patients.

Prostaglandins (PGs) are released as part of the inflammatory response. They are synthesised from arachidonic acid by the cyclooxygenase enzymes, COX-1 and -2. NSAIDS inhibit COX activity and have become the primary means of alleviating chronic pain associated with rheumatoid and osteoarthritis. They are also widely used as analgesics in the treatment of acute postsurgical and traumatic pain. PGs are known to play important functions in bone repair and normal bone homeostasis. Animal studies suggest that, whilst both nonspecific and specific inhibitors of COXs impair fracture healing, some studies have suggested that this impairment is due to COX-2. Although these data raise concerns about the use of COX-2-specific inhibitors as anti-inflammatory or analgesic drugs in patients undergoing orthopaedic procedures, clinical reports have been largely inconclusive concerning the effects of NSAIDs on bone healing. Since animal data suggest that the effects of COX-2 inhibitors are both dose-dependent and reversible, in the absence of scientifically sound clinical evidence it is suggested that physicians consider short-term administration or use of other drugs in the management of these patients.

During the last few decades, knowledge about growth factors and their function has increased. However, little is known about the interaction of these factors during bone growth and fracture healing. In vitro studies have shown a higher rate of cell proliferation and cell metabolism after the use of IGF-I and TGF-beta1 in combination, as compared to the single use of these factors. The purpose of this study was to investigate a possible synergistic effect of these growth factors in vivo, using a fracture model. A midshaft fracture of rat tibia (n = 84) was intramedullary stabilized with poly(D,L-lactide)-coated or uncoated titanium K-wires. The growth factors IGF-I and TGF-beta1, singly or in combination, were incorporated in the coating and continuously released during fracture healing. 28 days after fracture, we performed mechanical tests and histomorphological analyses. We found a greater stimulating effect of IGF-I on fracture healing than of TGF-beta1. The combined application of both growth factors resulted in a significantly higher maximum load and torsional stiffness than the use of only one of them. The histomorphometric analyses showed an increase in remodeling of the fracture callus in this group with less cartilaginous and more mineralized tissue than in the other groups. Both growth factors seem to have a synergistic effect on fracture healing in this model.

We studied the effects of intermittent administration of parathyroid hormone (PTH(1-34)) on callus formation and mechanical strength of tibial fractures in 27-month-old rats after 3 and 8 weeks of healing. 200 microg PTH(1-34)/kg was administered daily during both periods of healing, and control animals with fractures were given vehicle. At 3 weeks, PTH treatment increased maximum load and external callus volume by 160% and 208%; at 8 weeks, by 270% and 135%. It also enhanced callus bone mineral content (BMC) by 190% and 388% (3 and 8 weeks). From week 3 to week 8, callus BMC increased by 60% in the vehicle-injected animals, and by 169% in the PTH-treated animals. In the contralateral intact tibia, PTH treatment increased BMC by 18% and 21% (3 and 8 weeks). No differences in body weight were found between the vehicle-injected and the PTH-treated animals during the experiment. In conclusion, PTH treatment enhances fracture strength, callus volume and callus BMC after 3 and 8 weeks of healing.

The fractures that occur as a result of trauma frequently require multiple stage surgical procedures to achieve adequate union. Bone grafting with autogenous cancellous or cortico cancellous bone grafts is the traditional method used to repair bone defects. Most fractures will heal using this traditional procedure, however a number of fractures, up to 10% of the cases in United States alone, will result in delayed or impaired healing. Novel approaches are currently being investigated for the augmentation and acceleration of fracture healing. Some of these approaches include the use of biodegradable matrices; cell based approaches supplemented with osteogenic factors and genetic therapy. Cell based approaches for fracture healing have roused intense interest because of the great advance in the isolation and expansion of cells from the marrow that have the ability to differentiate into various types of cells including osteoblasts. In addition, the discovery and cloning of several proteins (bone morphogenetic proteins) that have the ability to induce bone formation, have contributed to the investigation of novel approaches to augment fracture healing. Use of genetic therapy for the augmentation of fracture healing has also recently gained strong interest. The attractive feature of gene therapy is that therapeutic proteins can be delivered locally to the fracture site in relatively high concentrations and in a sustained fashion. This review discusses these novel approaches and presents an assessment of their future clinical applicability.

Prolonged systemic administration of corticosteroids causes osteoporosis and increased risk of fracture. Despite this well documented side effect of systemic corticosteroids, the effect of these compounds on fracture healing is not well defined. The goal of this study was to test the hypothesis that systemic corticosteroid therapy adversely affects fracture healing in a rabbit ulnar osteotomy model. Non-critical sized (1 mm) defects were created bilaterally in 18 adult female New Zealand White rabbits. Starting 2 months before operative intervention and continuing for 6 weeks during healing of the osteotomies, a subcutaneous dose of either sterile saline or prednisone (0.15 mg/kg) was administered daily. Serial radiographs of the forelimb were taken immediately postoperatively and weekly beginning the second week postoperatively. After killing at 6 weeks, only 3 of 20 limbs from animals treated with prednisone achieved radiographic union while 13 of 16 control limbs achieved union. The radiographic density of bone in the defect as well as callus size were greater in the control limbs than in the limbs from prednisone-treated animals. DEXA confirmed that the bone mineral content was lower in the ulnae of prednisone-treated rabbits both within the defect and in adjacent ulnar bone. Mechanical data indicated that osteotomies from rabbits chronically treated with prednisone were weaker than in controls. In this rabbit ulnar osteotomy model, chronic prednisone treatment clearly inhibited bone healing.

In a randomized study of 32 postmenopausal women with a Colles' fracture, we studied whether 8 weeks of treatment with clodronate, a bisphosphonate, could prevent posttraumatic osteopenia. The patients were treated with a plaster splint for 4 weeks. The bone mineral density (BMD) of the forearm bones was measured at 2 levels with dual-energy x-ray absorptiometry (DEXA) 2, 6 and 12 months after the fracture. At 2 months, in the clodronate group, there was a median 53% higher BMD in the fracture region of the radius than in the uninjured radius. In the placebo group, we found a 33% higher BMD in the fractured radius at that level than in the uninjured radius. This increase in BMD of the fractured radius, caused by clodronate, was statistically significant. At 12 months, the BMD of the fracture side had been reduced by 17% and 12%, respectively, at that time it was still significantly increased in the clodronate group alone. In the ulna at the same level, we found no significant changes in BMD in either group on either side at any time. At 2 months, at the level between the distal and middle thirds, in the fractured radius, the median BMD was 7% lower in the clodronate group and 6% lower in the placebo group than in the uninjured radius. Although the reduction in BMD at that level was significant, there was no difference between the two treatment groups. At this level, the ulna on the fractured side showed a similar pattern, with a 5% lower BMD in the clodronate group and a 4% lower BMD in the placebo group. This osteopenia showed a small but significant progression on the fractured side after 6 and 12 months.

Operatively induced, standardized tibia fractures in 42 10-week-old male rats were fixed with intramedullary nails. 21 of the rats were fed liquid containing 15% ethanol. 5 weeks after inducing the fracture, the rats were killed and the total body bone mineral density (BMD) was analyzed with the DEXA technique, and the mechanical properties of the fractured and the unfractured tibiae as well as the ipsi- and contralateral femoral shaft and femoral neck were tested. The rats given a liquid containing 15% ethanol were found to have significantly lower total BMD and total calcium than the controls. We also found a significantly lower bending moment and bending stiffness both in the fractured and unfractured tibiae among rats fed on ethanol. The energy absorption until refracture was less in rats fed on ethanol. Posttraumatic osteopenia was present, as judged by the mechanical tests of the ipsilateral femoral shaft and the femoral neck in all animals. There was no difference in this respect between the animals fed on ethanol and the controls. We found that ethanol disturbs bone metabolism which reduces the mechanical properties of the tibiae and femora of rats, but the healing process of an induced tibial shaft fracture was not affected.

Clodronate was administered daily 28 days before and after an experimental tibial fracture in 35 male rats, and the effect on fracture healing and posttraumatic bone loss was studied. 5 groups were tested. The clodronate/clodronate group received clodronate in daily doses of 10 mg/kg body weight for 28 days before being subjected to a standardized fracture of the right tibia, and during the fracture healing period of 28 days. The clodronate/saline group received clodronate before fracture and saline during the healing period. The saline/clodronate group received saline before and clodronate after fracture. The saline/saline group received saline only, while the control group served as unfractured, untreated controls. After 28 days of fracture healing, the tibias were evaluated with dual energy x-ray absorptiometry, and tested mechanically in a 3-point ventral bending test. Bone mineral content and bone mineral density were approximately 30% higher in the groups receiving clodronate during the experiment, compared to the untreated groups. The weight and cross-sectional area of the fracture callus were equal in all groups. Whether clodronate was administered before the fracture, after the fracture or both, did not affect the bone mineral. Ultimate bending moment, energy absorption, stiffness and deflection were not significantly different between the groups. Our findings suggest that clodronate increases bone mineral both when given before and after a tibial shaft fracture, without affecting fracture healing at 28 days.

With the aim of preventing postfracture osteopenia, we randomized 24 patients with internally fixed ankle fractures to 3 months of treatment with placebo or 200 IU nasal salmon calcitonin (sCT) in a prospective, double-blind design. 3 patients were excluded, leaving 11 patients in the placebo group and 10 in the sCT group for study. Bilateral measurements of bone mineral content (BMC) in the coronal plane of the proximal tibia were performed by dual photon absorptiometry (DPA) postoperatively within 7 days of the fracture and after 1.5, 3 and 6 months. 3 months after the fracture, BMC in the injured legs had decreased by 14% in the placebo group and 2.1% in the sCT group. This difference was not statistically significant. In the healthy legs, a statistically significant intergroup difference was seen 6 weeks after the fracture, caused by a tendency towards a decrease in BMC of 4.6% in the placebo group, while BMC in the sCT group had increased by 7.4%. Nasal sCT may to some extent, but in this study not significantly, reduce postfracture osteopenia, and cause a significant effect on BMC in the healthy leg.

A statistical method for designing screening studies involving several experimental treatments compared to a standard treatment is developed. The screening study identifies the most promising experimental treatments, which then undergo more rigorous evaluation in a future, larger study. The technique is especially relevant for biopharmaceutical research and development in which phase II clinical trials are conducted to identify the most promising drug regimens, which then move on to phase III of clinical development. It is assumed that the underlying distribution of the primary efficacy random variable is a qualitative/quantitative mixture. The proposed methodology involves calculating the probability of accepting each experimental treatment compared to the standard treatment, where the criterion for acceptance is based on the proportion of qualitative observations and a measure of their location. The probability of acceptance is displayed in two dimensions using operating characteristic contour plots. The techniques are illustrated with some practical examples and some extensions are indicated.

Bone tissue contains numerous cell-to-cell signaling peptides called growth factors with potent effects on bone cell metabolism. In vivo studies over the last 5 years have demonstrated that growth factors can stimulate bone formation and bone healing and these results have made them candidates for use in orthopedic surgery. In numerous clinical conditions enhanced bone formation and bone healing could improve the results of surgery; clinical trials using growth factors to stimulate bone formation in spinal surgery, and to stimulate healing of bone defects, have been initiated. Growth factors for clinical use will become commercially available in the near future. This review describes the main growth factors and their actions in vitro and in vivo in relation to bone tissue and bone healing. Possible areas for clinical use are also discussed.

Basic Fibroblast Growth Factor (bFGF) is one of the endogenous factors found in bone matrix. bFGF is a mitogen for many cell types, including osteoblasts and chondrocytes. It can stimulate angiogenesis and osteoblast gene expression. The purpose of this study was to investigate whether exogenous bFGF can stimulate the formation of bone in bone grafts and in a bone graft substitute. In a model using demineralized bone matrix implants for bone induction, a dose of 15 ng bFGF per implant increased the number of chondrocytes and the amount of bone, whereas 1900 ng greatly inhibited cartilage and bone formation. These results are consistent with previous studies with this model, showing that a lower dose of bFGF increased bone calcium content and a higher dose reduced it. Thus, exogenous bFGF can stimulate proliferation during early phases of bone induction. A new device, the bone conduction chamber, was developed for the application of bFGF to bone conductive materials. This model made it possible to demonstrate a difference between the conductive properties of bone grafts and porous hydroxyapatite. bFGF increased bone ingrowth into bone graft inside the chamber and showed a biphasic dose-response curve, so that 8-200 ng per implant (0.4-10 ng/mm3) increased bone ingrowth, but higher or lower doses had no effect. The same doses had the same effects in porous hydroxyapatite. In both bone grafts and porous hydroxyapatite, the highest dose still caused an increase in ingrowth of fibrous tissue. The effect on bone ingrowth was first detected after 6 weeks, regardless if administration of bFGF started at implantation or 2 weeks later, using an implanted minipump. Hyaluronate gel was effective as a slow-release carrier for bFGF. In conclusion, bFGF stimulates bone formation in bone implants, depending on dose and method for administration.

Both fibroblast growth factors-1 (acidic FGF) and -2 (basic FGF) increase the proliferation of osteoblasts and chondrocytes in vitro and FGF-2 stimulates angiogenesis and bone formation in vivo. To test their effects on rabbit tibial fracture-healing under stable and unstable mechanical conditions, 3 micrograms of either FGF-1 or FGF-2 was injected around rabbit tibial fractures on day 4 after fracture. Neither growth factor had a significant effect on either the size of, or the amounts of bone and cartilage in, the 10-day callus irrespective of the mechanical conditions under which the fracture was healing. The 10-day FGF-2-treated calluses were, however, more mature than FGF-1-treated calluses because the cartilage was separated from the periosteum by bone and endochondral ossification had progressed further. In conclusion, 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.

We studied the effect of oxygen-free radicals on fracture healing. 30 male rats were divided into 2 groups: 15 rats were given saline 5 mL/kg i.p. (control group) and 15 were given zymosan 100 mg/kg i.p. to induce oxygen-free radicals through stimulation of NADPH oxidase in polymorphonuclear leucocytes. 1 hour later, the right forelimbs of the rats were broken by light manual compression. These treatments were given once a day until the fifth post-fracture day. All rats were killed on day 22, and histological sections of the radius and ulna were examined without knowledge of the treatment given. The administration of zymosan impaired the fracture healing and therefore oxygen-free radicals appear to play an important role in fracture healing.

The effect of Transforming Growth Factor beta (TGF-beta) administered locally around the fracture line of healing rat tibial fractures was investigated after 40 days of healing. TGF-beta in a dose of 4 ng or 40 ng was injected every second day during the healing period. The strength, stiffness, energy absorption and deflection of the fractures were measured in a materials-testing machine. Compared with placebo-treated animals, the ultimate load of the fractures increased in the group injected with 40 ng of TGF-beta, but not in those injected with 4 ng. TGF-beta induced a dose-dependent increase in the cross-sectional area of the callus and bone at the fracture line. Consequently, local treatment of fractures with TGF-beta increases the callus formation and strength. The energy absorption and deflection capacities of the healing fractures are preserved.

The ability of exogenous Transforming Growth Factor-beta (TGF-beta) to stimulate bone formation in fracture healing was investigated. TGF-beta was continuously applied in doses of 1 and 10 micrograms/day for 6 weeks to 2 groups of adult rabbits with unilateral plated mid-tibial osteotomies. A group receiving solvent without TGF-beta served as control. Fracture healing was evaluated by mechanical tests, bone morphometry and bone densitometry. Increased maximal bending strength and callus formation were demonstrated in the groups receiving TGF-beta. TGF-beta had no effect on bending-stiffness, bone mineral content, cortical thickness or haversian canal diameter. We conclude that local application of exogenous TGF-beta may enhance fracture healing in rabbits.

We investigated the effect of local infusion with prostaglandin E2 (PGE2) in doses of 0.0003 to 4.0 mg/hour per kg body weight for 6 weeks on a plated unilateral osteotomy in rabbits. PGE2 caused a dose-dependent stimulation of callus formation. Total bone mineral content increased, although the mineral content per volume of the callus was reduced. In another experiment, PGE2 was infused either in the first half or in the second half of the healing period. No effect of PGE2 infusion could be observed in the first half of the 6-week healing period, whereas PGE2 infusion during the second half caused callus stimulation.

We studied the effects of short-term therapy with methylprednisolone and indomethacin on healing of intramedullary pinned osteotomies of the femur in rats. When the osteotomy was complete and healing occurred under unstable conditions with callus formation, indomethacin inhibited healing when estimated by mechanical tests of bending moment, energy expenditure before refracture, and bending rigidity 6 weeks after surgery. No inhibitory effects were seen following corticosteroid treatment. When the osteotomy was incomplete and healing occurred under stable conditions, similar tendencies were observed. Thus, short-term medication with indomethacin inhibits fracture healing. This was not the case with short-term methylprednisolone.