Influence of brain injury on early posttraumatic bone metabolism

The Role of Neuromodulation and Potential Mechanism in Regulating Heterotopic Ossification

Heterotopic ossification (HO) is a pathological process characterized by the aberrant formation of bone in muscles and soft tissues. It is commonly triggered by traumatic brain injury, spinal cord injury, and burns. Despite a wide range of evidence underscoring the significance of neurogenic signals in proper bone remodeling, a clear understanding of HO induced by nerve injury remains rudimentary. Recent studies suggest that injury to the nervous system can activate various signaling pathways, such as TGF-β, leading to neurogenic HO through the release of neurotrophins. These pathophysiological changes lay a robust groundwork for the prevention and treatment of HO. In this review, we collected evidence to elucidate the mechanisms underlying the pathogenesis of HO related to nerve injury, aiming to enhance our understanding of how neurological repair processes can culminate in HO.

Parathyroid hormone changes in infants investigated for inflicted injury; an observational retrospective single centre cohort study

BACKGROUND

Biochemical and haematological testing is recommended in the United Kingdom when inflicted injury is suspected. We examined the associations of test results with radiologically-confirmed fracture(s), and between test results, in a large retrospective observational cohort.

METHODS

Infants up to age two years presenting with suspected inflicted injury, without clinically or radiologically apparent bone disease, and where a skeletal survey was undertaken during the period 1st August 2013 to 31st December 2020, were included. Biochemical parameters: corrected calcium (cCa); phosphate (P); alkaline phosphatase (ALP); parathyroid hormone (PTH); 25-hydroxyvitamin D (25D); and haematological parameters: haemoglobin (Hb); mean corpuscular haemoglobin (MCH); mean corpuscular haemoglobin content (MCHC); mean corpuscular volume (MCV); platelet count were collated together with the results of the radiological assessments.

FINDINGS

Of 332 eligible infants (190 male), 142 (84 male) had fracture(s) and/or intracranial injury. Mean PTH in the non-fracture group (n measured 50/190) was 27.3 ng/l; in those with intracranial injury alone (n measured 9/23) was 39.4 ng/l; in those with fracture alone (n measured 62/84) was 45.0 ng/l; and in those with fracture and intracranial injury (n measured 20/35) 51.8 ng/l. F-test of multiple means = 0.0369. There was no difference in 25D between the groups.

INTERPRETATION

PTH was raised in infants who had fracture(s), intracranial injury or both. A single raised PTH may not necessarily be an indicator of prior disturbed skeletal health in these circumstances. The relevance of vitamin D status and interpretation of data from biochemical testing should be informed by the overall presentation in suspected inflicted injury cases. A single raised PTH may be a consequence of the child's injuries rather than prior disturbed bone health.

The Effects of Adipose Derived Stromal Vascular Fraction and Platelet-Rich Plasma on Bone Healing of a Rat Model With Chronic Kidney Disease

BACKGROUND

Chronic kidney disease (CKD) impairs osteoblast/osteoclast balance and damages bone structure with diminished mineralization and results in bone restoration disorders. In this study, we investigate the effects of adipose-derived stromal vascular fraction and platelet-rich plasma (PRP) on bone healing model in rats with CKD.

METHODS

Sprague-Dawley rats were separated into 4 groups. All groups except group I (healthy control) had CKD surgery using 5/6 nephrectomy model. All groups had intramedullary pin fixation after receiving bone fracture using drilling tools. Group II rats were used as control group for CKD. Group III rats received PRP treatment on fracture site. Group IV rats received PRP and stromal vascular fraction treatment on fracture site.Weight loss and blood samples were followed at the time of kidney surgery, third, sixth, and 12th weeks. Bone healing and callus formations were compared, biomechanically, radiologically, histopathologically, and immunohistochemically. Osteoblastic transformation of stem cells was assessed with DiI staining.

RESULTS

Negative effects of CKD on bone healing were reduced by increasing mechanical, histological, radiological, and biochemical properties of the bone with stromal vascular fraction and PRP treatments. Although thickness of callus tissue delayed bone healing process, it also enhanced biomechanical features and bone tissue organization.

CONCLUSIONS

Platelet-rich plasma and adipose-derived stromal vascular fraction treatments were effective for bone healing in animal model, which can be promising for clinical trials.

Effects of Neurological Disorders on Bone Health

Neurological diseases, particularly in the context of aging, have serious impacts on quality of life and can negatively affect bone health. The brain-bone axis is critically important for skeletal metabolism, sensory innervation, and endocrine cross-talk between these organs. This review discusses current evidence for the cellular and molecular mechanisms by which various neurological disease categories, including autoimmune, developmental, dementia-related, movement, neuromuscular, stroke, trauma, and psychological, impart changes in bone homeostasis and mass, as well as fracture risk. Likewise, how bone may affect neurological function is discussed. Gaining a better understanding of brain-bone interactions, particularly in patients with underlying neurological disorders, may lead to development of novel therapies and discovery of shared risk factors, as well as highlight the need for broad, whole-health clinical approaches toward treatment.

Association of serum osteocalcin levels with glucose metabolism in trauma patients

Osteocalcin (OC) is an endocrine hormone that regulates glucose metabolism.The aim of this study was to investigate the relationship between serum OC levels and glucose metabolism after trauma.This was a retrospective study of trauma patients admitted to the Department of Emergency Medicine between October 2017 and April 2019. Age, height, weight, injury severity score, and previous medical history were recorded. Serum N-terminal mid-fragment of OC (N-MID OC), hemoglobin Alc (HbA1c), fasting plasma glucose (FPG), fasting insulin (FINS), C-peptide, and other biochemical indicators were measured. Differences between the HbA1c-L (HbA1c <6.5%) and HbA1c-H (HbA1c ≥6.5%) groups were compared. The association of N-MID OC with indicators of glucose metabolism was analyzed.Out of 394 trauma patients, leukocyte and FPG levels in the HbA1c-H group (n = 93) were higher (P < .05), while N-MID OC levels were lower (P = .011) than the HbA1c-L group (n = 301). N-MID OC was negatively correlated with HbA1c in the total population (r = -0.273, P < .001) as well as in the HbA1c-L (r = -0.289, P < .001) and HbA1c-H (r = -0.390, P < 0.001) groups, and was positively correlated with C-peptide in the HbA1c-H group (r = 0.395, P < .001). The different quartiles in the HbA1c-L showed that N-MID OC declined with increasing HbA1c, which was higher than N-MID OC levels in the HbA1c-H group. Multiple linear regression analysis revealed that serum HbA1c was independently associated with serum OC levels after trauma (β=-1.608, P < .001).This study strongly suggests the importance of serum OC on glucose metabolism in trauma patients. HbA1c is independently associated with serum OC levels.

Crosstalk of Brain and Bone-Clinical Observations and Their Molecular Bases

As brain and bone disorders represent major health issues worldwide, substantial clinical investigations demonstrated a bidirectional crosstalk on several levels, mechanistically linking both apparently unrelated organs. While multiple stress, mood and neurodegenerative brain disorders are associated with osteoporosis, rare genetic skeletal diseases display impaired brain development and function. Along with brain and bone pathologies, particularly trauma events highlight the strong interaction of both organs. This review summarizes clinical and experimental observations reported for the crosstalk of brain and bone, followed by a detailed overview of their molecular bases. While brain-derived molecules affecting bone include central regulators, transmitters of the sympathetic, parasympathetic and sensory nervous system, bone-derived mediators altering brain function are released from bone cells and the bone marrow. Although the main pathways of the brain-bone crosstalk remain ‘efferent’, signaling from brain to bone, this review emphasizes the emergence of bone as a crucial ‘afferent’ regulator of cerebral development, function and pathophysiology. Therefore, unraveling the physiological and pathological bases of brain-bone interactions revealed promising pharmacologic targets and novel treatment strategies promoting concurrent brain and bone recovery.

Long-term Consequences of Traumatic Brain Injury in Bone Metabolism

Traumatic brain injury (TBI) leads to long-term cognitive, behavioral, affective deficits, and increase neurodegenerative diseases. It is only in recent years that there is growing awareness that TBI even in its milder form poses long-term health consequences to not only the brain but to other organ systems. Also, the concept that hormonal signals and neural circuits that originate in the hypothalamus play key roles in regulating skeletal system is gaining recognition based on recent mouse genetic studies. Accordingly, many TBI patients have also presented with hormonal dysfunction, increased skeletal fragility, and increased risk of skeletal diseases. Research from animal models suggests that TBI may exacerbate the activation and inactivation of molecular pathways leading to changes in both osteogenesis and bone destruction. TBI has also been found to induce the formation of heterotopic ossification and increased callus formation at sites of muscle or fracture injury through increased vascularization and activation of systemic factors. Recent studies also suggest that the disruption of endocrine factors and neuropeptides caused by TBI may induce adverse skeletal effects. This review will discuss the long-term consequences of TBI on the skeletal system and TBI-induced signaling pathways that contribute to the formation of ectopic bone, altered fracture healing, and reduced bone mass.

Histopathological examination of bone debris from reaming of interlocking intra-medullary nail fixation of long bone fractures with concomitant head injury

BACKGROUD/AIM

The aim of study was to test, for the presence of osteoblasts in the reaming debris of intramedullary nailing of femoral and tibial fracture in patients with and without severe head injury.

METHODS

Two groups of patients were studied. Group A (n = 32) had long bone fractures in addition to having head injuries. Group B (n = 35) had only long bone fractures. The fractures in the 2 groups of patients was treated by inter medullary nailing. Osteoblasts in the debris of the inter medullary nailing was compared between the 2 groups of patients.

RESULTS

The results demonstrated that histopathological specimens from reaming debris of fractured femur and tibia in patients with head injury showed osteoblasts in (82.9%) and in (27.5%) of patients with isolated long bone fractures (p < 0.001).

CONCLUSION

Healing indicators in diaphyseal fractures and concomitant head injury confirm fast and adequate healing in these patients and the presence of plenty of osteoblasts in their reaming debris may reflect a proof of accelerated fracture healing environment.

The effect of traumatic brain injury on bone healing: an experimental study in a novel in vivo animal model

INTRODUCTION

Among many factors determining the outcome of complex fractures in polytrauma patients, the role of traumatic brain injury (TBI) remains only partly understood. The aim of the present study was to examine the effect of traumatic brain injury on bone healing through the establishment of a novel standardised animal model that sequentially combines traumatic brain injury (TBI) with a long bone injury.

MATERIALS AND METHODS

Thirty-six female twelve-week old C57/BL6 mice were randomised in two groups (fracture (Fx)-group and combined-trauma (Fx/TBI) group). The methods of the Control Cortical Impact Injury for induction of TBI and of the femoral osteotomy, fixed with an external fixator for the simulation of the long bone fracture, were combined. No TBI was induced in the Fx-group. Bone healing was examined using in vivo micro-CT measurements over a period of three weeks.

RESULTS

The severity of the TBI was sufficient to stimulate a significantly increased callus formation in the Fx/TBI-group with an acceptable mortality rate. The micro-CT analysis of fracture healing displayed a significantly increased callus volume in the Fx/TBI-group already from the second postoperative week. This difference remained significant throughout the entire study period.

DISCUSSION

The successful and standardised combination of TBI and fracture in a mouse model allows systematic and quantitative in vivo analysis of underlying pathways that trigger the mutual interaction between musculoskeletal trauma and brain injury, as well as, corresponding differences in fracture healing using micro-CT methods.

CONCLUSION

The present study offers three new aspects: a standardised model for combined injury of TBI and femoral osteotomy; direct and serial in vivo imaging and quantification of fracture healing response using micro-CT; testing of potentially beneficial therapeutic regimens for fracture treatment in presence of TBI. Thus this model provides a valuable basic approach for the study of the amplifying effect of TBI on callus formation seen in patients with craniocerebral injury and concomitant skeletal trauma.

The negative impact of traumatic brain injury (TBI) on bone in a mouse model

INTRODUCTION

While it is well established that the brain produces hypothalamic hormones and neuropeptides that influence skeletal metabolism, the impact of traumatic brain injury (TBI) on bone is unknown. Based on the recognition from clinical studies that there is an association between TBI and long-term hypothalamic pituitary dysfunction, it was hypothesized that TBI exerts a negative impact on skeletal growth and maintenance.

METHODS

To test the hypothesis, this study employed a repetitive weight drop model for TBI. Four impacts were applied for four consecutive days on 5-week old female C57BL/6 J mice. Bone measurements were taken 2 weeks after the first impact.

RESULTS

Bone mineral content (BMC), bone area (B area) and bone mineral density (BMD) in the total body were reduced by 14.5%, 9.8% and 5.2%, respectively, in the impacted vs. control mice. There was a 17.1% reduction in total volumetric BMD (vBMD) and a 4.0% reduction in material vBMD in cortical bone. In trabecular bone, there was a 44.0% reduction in BV/TV. Although there was no change in the cross-sectional bone size, the tibial growth plate and the tibia itself were shortened.

CONCLUSION

The repetitive animal TBI model produced an immediate, strong negative impact on bone mass acquisition in young mice.

Arachidonic acid: a bridge between traumatic brain injury and fracture healing

Traumatic brain injury (TBI) is associated with enhanced osteogenesis. The aim of this study was to investigate the effect of serum from TBI rats on fracture healing. Results from this study showed that the serum from TBI rats enhanced the expression of bone gamma carboxyglutamate protein (BGLAP), and promoted in vitro proliferation of MC3T3-E1 cells, a mouse osteoblastic cell line. Furthermore, gas chromatography/mass spectrometry (GC/MS) coupled with multivariate statistical analysis was used to identify the changes in global serum metabolites after TBI. We found that arachidonic acid (AA) was significantly enhanced in serum metabolites in TBI subjects, while hydroxybutyric acid, leucine, malic acid, 5-oxyproline, isocitric acid, mannose, and uric acid were reduced. Finally, we examined the effects of AA on BGLAP expression and cell proliferation in MC3T3-E1 cells. We found that BGLAP expression and proliferation of osteoblasts were positively regulated in the presence of AA. These findings suggest that the increased AA in serum after TBI may play a key role in enhancing the speed of fracture healing.

Low turnover osteoporosis in sheep induced by hypothalamic-pituitary disconnection

The hypothalamus is of critical importance in regulating bone remodeling. This is underscored by the fact that intracerebroventricular-application of leptin in ewe leads to osteopenia. As a large animal model of osteoporosis, this approach has some limitations, such as high technical expenditure and running costs. Therefore we asked if a surgical ablation of the leptin signaling axis would have the same effects and would thereby be a more useful model. We analyzed the bone phenotype of ewe after surgical hypothalamo-pituitary disconnection (HPD + OVX) as compared to control ewe (OVX) after 3 and 12 months. Analyses included histomorphometric characterization, micro-CT and measurement of bone turnover parameters. Already 3 months after HPD we found osteopenic ewe with a significantly decreased bone formation (69%) and osteoclast activity (49%). After a period of 12 months the HPD group additionally developed an (preclinical) osteoporosis with significant reduction (33%) of femoral cortical thickness, as compared to controls (OVX). Taken together, HPD leads after 12 month to osteoporosis with a reduction in both trabecular and cortical bone caused by a low bone turnover situation, with reduced osteoblast and osteoclast activity, as compared to controls (OVX). The HPD-sheep is a suitable large animal model of osteoporosis. Furthermore our results indicate that an intact hypothalamo-pituitary axis is required for activation of bone turnover.

Potential risk factors for developing heterotopic ossification in patients with severe traumatic brain injury

BACKGROUND

Heterotopic ossification (HO) is a frequent complication after traumatic brain injury (TBI). The current preliminary study is intended to provide additional data on the potential roles that brain injury severity, concomitant orthopaedic trauma, and specific intensive care complicating events may play in the prediction of HO in patients who have sustained severe TBI.

METHODS

A prospective cohort study in patients with severe TBI.

RESULTS

Ninety-seven of the 176 patients were eligible for follow-up; 13 patients (13%) developed 19 clinically relevant HOs at 1 or more sites. Univariate analysis indicated that patients with HO remained in coma longer (P < .001) and were ventilated during a longer period (P = .002). Autonomic dysregulation (relative risk = 6.11, 95% confidence interval: 2.53-14.76) and surgically treated extremity fractures (relative risk = 5.02, 95% confidence interval: 1.68-15.04) also showed significant associations with the development of HO.

CONCLUSION

Prolonged coma duration and mechanical ventilation, coexistent surgically treated bone fractures and clinical signs of autonomic dysregulation should be given further consideration as potential risk factors for developing clinically relevant HO. Larger-scale studies are needed to develop a valid risk profile that takes into account the interrelationships between variables.

Effect of rat brain tissue extracts on osteoblast proliferation and differentiation

PURPOSE

The reason for enhanced fracture healing in traumatic brain injury patients is not clearly understood. It is possible that factors inherent in the brain passing through the blood-brain barrier to the peripheral circulation, or a disruption of central nervous system (CNS) control of the sympathetic nervous system (SNS), stimulates the process of fracture healing.

METHODS

In this study, we assessed proliferation [using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay] and differentiation [using alkaline phosphatase (ALP)] in rat osteoblasts incubated with gray matter or other tissue extracts with and without the addition of an α- or β-adrenergic receptor blocker (phentolamine or propranolol).

RESULTS

Gray matter extract from normal brain caused a dose-dependent increase in osteoblast proliferation and differentiation. Serum from normal rats enhanced differentiation but not proliferation. Alpha-receptor blockade had no effect on proliferation or differentiation. Beta-receptor blockade caused a partial, but statistically significant, decrease in gray matter stimulation of osteoblast differentiation.

CONCLUSION

The results of this study indicate that gray matter extract from normal brain increases osteoblast proliferation and differentiation and that β receptors may be involved in differentiation under these conditions.

[Heterotopic ossifications in major burn injuries : An interdisciplinary challenge]

Heterotopic ossifications in peri-articular tissue can appear after severe head injury, spinal trauma or local joint trauma. Following extensive burns, heterotopic ossifications are a rare, but severe complication with an unknown pathogenesis. In a retrospective analysis of 672 patients who were treated in our burn center over the last 10 years we identified 5 cases (0.74%) of heterotopic ossification.

Heterotopic ossification following cardiac arrest and hypoxic brain damage

Aims

Heterotopic bone can cause restriction of movement when deposited in the soft tissues around joints. Neurogenic heterotopic ossification may follow brain injury. This article describes research into the incidence of heterotopic ossification after brain injury, and its impact on rehabilitation.

Methods

Thirty-nine patients who were admitted to the rehabilitation unit of University Hospital Bydgoszcz, Poland, after hypoxic brain injury due to cardiac arrest, were examined.

Findings

Six patients were identified as having developed heterotopic bone around one or more joints causing limitation of movement and delay in the rehabilitation process.

Conclusions

Heterotopic ossification occurs in up to 15% of patients following hypoxic brain injury. The development of the condition may often be missed clinically, and can hinder rehabilitation.

Elevated leptin expression in a rat model of fracture and traumatic brain injury

A few studies have reported a relationship between leptin induced by brain injury and healing of bone tissue. Our objective was to measure serum and callus leptin expression within the setting of fracture and traumatic brain injury (TBI). Sixty-four male Sprague-Dawley rats were randomised equally into four groups: control, TBI group, fracture group and fracture/TBI group. Rats were sacrificed at 2, 4, 8 and 12 weeks after fracture/TBI. Serum leptin was detected using radio-immunoassay, and callus formation was measured radiologically. Callus leptin was analysed with immunohistochemistry. Serum leptin was significantly increased in the fracture, TBI and combined fracture/TBI groups compared with the control group at 2 weeks (P &lt; 0.05). Serum leptin was significantly higher in the combined fracture/TBI group than in the fracture and TBI groups at 4 and 8 weeks (P &lt; 0.05). The percentage of leptin-positive cells in the callus and callus volume were significantly higher in the fracture/TBI group than in the fracture-only group (P &lt; 0.001). Thus, we demonstrated elevated leptin expression within healing bone, particularly in the first 8 weeks of a rat model combining fracture and TBI. A close association exists between leptin levels and the degree of callus formation in fractures.

Humoral factors enhance fracture-healing and callus formation in patients with traumatic brain injury

BACKGROUND

Scientific evidence is mounting for an association between traumatic brain injury and enhanced osteogenesis. The aim of this study was to correlate the in vitro osteoinductive potential of serum with the features of fracture-healing and the extent of brain damage in patients with severe traumatic brain injury and bone fracture.

METHODS

Patients with a long-bone fracture and a traumatic brain injury (seventeen patients) or without a brain injury (twenty-four patients) were recruited. The Glasgow Coma Scale score was determined on admission. Radiographs of the fracture were made before surgery, at six weeks, and at three, six, and twelve months after surgery. The time to union was estimated clinically and radiographically, and the callus ratio to shaft diameter was calculated. Serum samples were collected at six, twenty-four, seventy-two, and 168 hours after injury, and their osteogenic potential was determined by measurement of the in vitro proliferation rate of the human fetal osteoblastic cell line hFOB1.19.

RESULTS

Patients with a traumatic brain injury had a twofold shorter time to union (p = 0.01), a 37% to 50% increased callus ratio (p < 0.01), and their sera induced a higher proliferation rate in hFOB cells (p < 0.05). A linear relationship was revealed between hFOB cell proliferation rates and the amount of callus formed (p < 0.05). The Glasgow Coma Scale score was correlated with the callus ratio on both radiographic projections (p < 0.05), time to union (p = 0.04), and the proliferation rate of hFOB cells at six hours after injury (p = 0.03).

CONCLUSIONS

Patients with a severe brain injury release unknown humoral factors into the blood circulation that enhance and accelerate fracture-healing.

From brain to bone: evidence for the release of osteogenic humoral factors after traumatic brain injury

PRIMARY OBJECTIVE

The aetiology of the increased osteogenesis associated with severe traumatic brain injury (TBI) remains incompletely understood. The purpose of this article is to review the available evidence regarding the release of osteogenic humoral factors after TBI.

RESEARCH DESIGN

This study is presented in the form of a literature review.

METHODS AND PROCEDURES

To obtain suitable references, Pubmed was searched using keywords 'heterotopic ossification', 'brain', 'trauma', 'injury', 'aetiology'.

MAIN OUTCOMES AND RESULTS

Evidence from both clinical and laboratory investigations points to centrally released osteogenic factor(s) that enter the systemic circulation following TBI.

CONCLUSIONS

Further investigation into the identification of these putative osteogenic factor(s), using human tissues and new techniques, is indicated to better understand this phenomenon.

[Heterotopic ossification - from the aetiology to the current management]

Heterotopic ossifications (HO) are defined as the abnormal formation of bone in soft tissues. It can be classified into acquired and congenital forms. The acquired form, of which the pathogenesis is not fully understood, is often diagnosed in patients with traumatic brain injury, spinal cord injury, musculo-skeletal trauma or injuries associated with burns. HO presents itself mostly asymptomatically, the symptoms of the initial stadium are often unspecific; however, severe forms can lead to severe disability. Imaging techniques, foremost bone szintigraphy, are mostly used for verification of the diagnosis. Local radiotherapy and nonsteroidal anti-inflammatory drugs are the classical therapeutic and prophylactic options. In advanced stages, surgical resection may be required.

Leptin Increases Extracellular Matrix Mineralization of Human Osteoblasts From Heterotopic Ossification and Normal Bone

Heterotopic ossification (HO) is the pathologic formation of bone in soft tissue. The exact pathomechanism is unknown but probably involves a disturbed osteoblast differentiation. Leptin, known as the obesity gene, may regulate normal osteoblast function in vitro. The aim of the present in vitro study was to further analyze the pathomechanisms of HO, including a possible role of leptin in ectopic bone formation. Human osteoblasts were cultivated either from normal bone or from resected HO. Both groups were incubated with increasing doses of leptin. Phenotype expression and mineralization of extracellular matrix were measured after 7, 14, and 21 days. In both groups, leptin increased both the formation of bone nodules and Ca-45 incorporation. This is the first study to analyze the effect of leptin on bone cells from ectopic ossification. Similar to the in vitro behavior of normal osteoblasts, cells from HO respond to leptin exposure with an increased mineralization of the extracellular matrix. This mechanism may be involved in the pathogenesis of ectopic bone formation in vivo.

Femoral head injuries: Which treatment strategy can be recommended?

Despite different operative and non-operative treatment regimens, the outcome after femoral head fractures has changed little over the past decades. The initial trauma itself as well as secondary changes such as posttraumatic osteoarthritis, avascular necrosis or heterotopic ossification is often responsible for severe loss of function of the afflicted hip joint. Anatomic reduction of all fracture fragments seems to be a major influencing factor in determining the outcome quality. Eight years ago we inaugurated a new surgical approach for better access and visualisation for the treatment of femoral head fractures, using the "trochanteric flip" (digastric) osteotomy. Thus inspection of the entire hip joint and accurate fragment reduction under direct visual control are possible. After good initial experiences with this operative procedure we changed our standard treatment regimen to this approach in an attempt to achieve the most accurate anatomic reduction of the femoral head in every affected patient. Between 1998 and 2006 we operated on 12 patients with femoral head fractures associated with posterior hip dislocation, using the new surgical approach. Patients were followed for 2-96 months and outcome was documented with the Merle d'Aubigne and Postel score as well as the Thompson and Epstein score. The posttraumatic formation of heterotopic bone was documented with the Brooker score. Retrospective analysis of these 12 patients showed good or excellent results in 10 patients (83.3%). The two patients with poor outcome developed an avascular necrosis of the femoral head and underwent total hip arthroplasty. Periarticular heterotopic ossification was seen in five patients. In four patients this caused a significantly reduced range of motion and was therefore considered as a posttraumatic complication. The two patients with the most severe heterotopic bone formation (Brooker III and IV) had initially sustained multiple injuries including brain injury. Comparing our results with earlier published series including our own before changing the treatment protocol, the data suggest a favorable outcome in patients with trochanteric flip (digastric) osteotomy for the treatment of femoral head fractures.

Cbfa-1 (Runx-2) and osteocalcin expression by human osteoblasts in heparin osteoporosis in vitro

Heparin may cause adverse effects on bone formation following long-term application. The exact pathomechanism is unclear, but in vitro data suggest an impaired osteoblast function. The transcription axis of Cbfa-1 (Runx-2) and osteocalcin is crucial in maintaining an equilibrium of bone formation and resorption in vivo. We used a human osteoblast cell culture model to further investigate the effect of heparin (low-molecular-weight heparin, dalteparin) on the expression of these two regulators of osteoblast differentiation. At high doses, dalteparin caused a significant inhibition of both osteocalcin and Cbfa-1 expression in vitro. Our data support the hypothesis of a direct inhibition of osteoblast function underlying heparin osteoporosis.

Leptin inhibits bone formation not only in rodents, but also in sheep

This study examines the effect of long-term ICV administration of leptin in ewes. We found that central application significantly decreased osteoblast activity as measured by serum analysis as well as by histomorphometry, resulting in decreased trabecular bone volume. These data provide additional evidence that bone formation and therefore bone remodeling is at least in part centrally controlled.

INTRODUCTION

Genetic studies in mice have identified leptin as a potent inhibitor of bone formation acting through the central nervous system and unraveled the central nature of bone mass control and its disorders. Although these studies have radically enhanced our understanding of skeletal physiology because they have established a hypothalamic regulation of bone remodeling through the sympathetic nervous system, controversy remains about the physiological relevance of these observations because leptin's effect on bone after intracerebroventricular (ICV) application has only been shown in mice. To address whether leptin has a role in regulating bone mass beyond rodents, we treated ewes with long-term ICV application of leptin and analyzed the bone phenotype after a treatment period of 3 months.

MATERIALS AND METHODS

Three groups of corriedale sheep were compared: (1) control entire (control), (2) ovariectomy (OVX) and ICV application of cerebrospinal fluid (CSF); and (iii) OVX and ICV application of leptin (leptin). Analysis included histomorphometric characterization of iliac crest, spine and femur by histology and biomechanical testing and measurement of bone turnover parameters in serum and urine.

RESULTS

Central application of leptin decreased bone formation by 70% and mineralizing surface (MS/BS, 39.4 +/- 3.3% versus 16.1 +/- 2.1%) significantly (p < 0.01). Whereas OVX increased osteoclast indices and urinary cross-lap excretion by two and three times, respectively, serum parameters of osteoblast activity were significantly reduced by ICV application of leptin (p < 0.01). Consequently, ewes treated with leptin were osteopenic (iliac crest BV/TV entire, 22.7 +/- 1.3%; CSF, 18.9 +/- 2.4%; leptin, 12.4 +/- 2.6%), whereas bone torsional failure load reflecting the cortex of the tibia was not yet changed after 3 months of treatment (p < 0.01).

CONCLUSIONS

Taken together, these data suggest that leptin controls bone formation after ICV application, leading to reduction of trabecular bone mass in sheep. Most importantly, however, they show that the central regulation of bone formation is not limited to rodents, but is also found in large animals, providing further evidence that bone remodeling in vertebrates is centrally controlled.

[Pathophysiology and pathomorphology of osteoporosis]

Osteoporosis is a disease that leads to fragility fractures due to loss of bone mass and bone microstructure. This review presents an update on the fundamental pathophysiologic and pathomorphologic mechanisms of bone loss situations. Pathomorphologic characteristics such as perforations and microcallus formations are explained. The physiologic relevance of the remodeling process as well as its control by local-paracrine, systemic-endocrine and central-neural signaling pathways is discussed. Furthermore the role of hormones such as estrogen, FSH and leptin, of transcription-factors such as Runx2 and osterix and as well as that of the wnt signaling pathway for bone cell differentiation and function is presented. On the basis of current knowledge osteoporosis can be diagnosed, treated and fractures can be prevented. However, it is likely that new and even more effective diagnostic and therapeutic strategies will emerge as our understanding of the remodeling process that controls osteoblast and osteoclast function increases.

A comparative analysis of phenotype expression in human osteoblasts from heterotopic ossification and normal bone

BACKGROUND AND AIMS

Heterotopic ossification (HO) is a pathological bone formation process in which ectopic bone is formed in soft tissue. The formation of bone depends on the expression of the osteoblast phenotype. Earlier studies have shown conflicting results on the expression of phenotype markers of cells originating from HO and normal bone. The hypothesis of the present study is that cells from HO show an altered expression of osteoblast-specific phenotype markers compared to normal osteoblasts. The aims of the study were to further characterize the expression of osteoblast phenotypemarkers and to provide a comparison with other study results.

PATIENTS AND METHODS

Using an in vitro technique, reverse transcription polymerase chain reaction (RT-PCR), real-time PCR and immunohistochemistry, we compared the phenotype gene expression (type I collagen, alkaline phosphatase, Cbfa-1, osteocalcin) of osteoblasts from resected HO and normal bone (iliac crest).

RESULTS

Cells from HO expressed the osteoblast phenotype (type I collagen, alkaline phosphatase) but were characterized by a depleted osteocalcin expression. The expression of Cbfa-1 (osteocalcin transcription gene) showed a large variety in our study. Preoperative radiotherapy had no effect on phenotype expression in cells from HO.

CONCLUSION

Our results provide a characterization of cells originating from HO and support the thesis of an impaired osteoblast differentiation underlying the formation of HO. The transcription axis from Cbfa-1 to osteocalcin could be involved in the pathogenesis of HO.