Serum after traumatic brain injury increases proliferation and supports expression of osteoblast markers in muscle cells

Alterations of Alpl and bFGF levels in peripheral tissues after mild traumatic brain injury: implications on sexual differences

BACKGROUND

Mild traumatic brain injury (mTBI) is a significant health issue affecting people of all ages and socioeconomic groups. Its clinical spectrum alters from transient mild symptoms to disabling problems. The molecular mechanisms that affect the vital functions and treatment after mTBI have yet to be fully understood. This study aims to investigate the expression levels of Alkaline Phosphatase (Alpl) and Fibroblast Growth Factor (bFGF) in peripheral organs after mTBI in traumatic mice models and observe the differences between acute and chronic phases.

METHODS AND RESULTS

A total of 30 animals were randomly divided into three groups, with equal numbers of males and females in each group. mTBI was induced in mice utilizing the Marmarau trauma model. Alpl and bFGF expression levels in the acute and chronic phases were determined via Real-Time PCR in liver, kidney, bone, and muscle tissues. Alpl and bFGF gene expressions in the acute phase after mTBI increased significantly. In the kidney, Alpl and bFGF levels increased in the acute phase in females, but bFGF significantly decreased in males. In muscle tissue bFGF levels significantly increased in males in the chronic phase. Our study showed significant differences between sexes in response to mTBI.

CONCLUSIONS

Our study investigated the role of Alpl and bFGF genes in peripheral tissues in acute and chronic phases after mTBI for the first time in the literature. The data obtained will guide understanding the secondary events and the consequences of the disease in mTBI and taking the necessary treatment and measures.

Association of alkaline-phosphatase/albumin ratio with all-cause mortality in critically ill patients with ischemic stroke: a retrospective study

Background

Recent studies have shown that alkaline phosphatase to albumin ratio (APAR) is a prognostic biomarker for coronary heart disease and cancer. However, the effect of APAR on the prognosis of ischemic stroke (IS) remains unclear. We aimed to assess the association of APAR with all-cause mortality in critically ill patients with IS.

Methods

Critically ill patients with IS were identified from the Medical Information Mart for Intensive Care-IV (MIMIC-IV) Version 3.0 database, and classified into quartiles based on APAR index levels. Clinical outcomes included all-cause mortality at 28-days, 90-days and 365-days after admission. Cox proportional hazards regression analysis and restricted cubic spline method were used to clarify the relationship between APAR index and clinical outcomes in critically ill patients with IS.

Results

A total of 1,690 critically ill patients with IS were selected from the MIMIC-IV database. Multivariate Cox proportional hazard analysis showed that increased APAR index was significantly associated with all-cause mortality. After adjusting for potential confounding factors, patients with higher APAR (Q4: 1.524-2.794) had significantly increased all-cause mortality at 28-days, 90-days, and 365-days after admission (HR 2.05, 95%CI 1.47-2.86, p = 0; HR 2.09, 95%CI 1.53-2.85, p = 0; HR 2.11, 95%CI 1.55-2.87, p = 0). APAR had a linear relationship with 28-days and 365-days mortality (P for non-linearity: 0.098 and 0.051), but a nonlinear relationship with 90-days mortality (P for non-linearity: 0.042). Subgroup analyses further revealed that higher APAR was also associated with increased long-term mortality in IS patients without hypertension, DM, cardiovascular disease, liver disease or CKD. In addition, we did not observe any interaction between subgroup variables and APAR.

Conclusion

A higher APAR index was significantly associated with increased all-cause mortality at 28-days, 90-days and 365-days after admission for critically ill patients with IS. The APAR index may help identify patients with IS at high risk of all-cause death.

Accelerated fracture healing accompanied with traumatic brain injury: A review of clinical studies, animal models and potential mechanisms

The orthopaedic community frequently encounters polytrauma individuals with concomitant traumatic brain injury (TBI) and their fractures demonstrate accelerated fracture union, but the mechanisms remain far from clear. Animal and clinical studies demonstrate robust callus formation at the early healing process and expedited radiographical union. In humans, robust callus formation in TBI occurs independently of fracture fixation methods across multiple fracture sites. Animal studies of TBI replicate clinically relevant enlarged fracture callus as characterized by increased tissue volume and bone volume at the early stages. However, refinement and standardization of the TBI models requires further research. The quest for its underlying mechanisms began with the finding of increased osteogenesis in vitro using the serum and cerebral spinal fluid (CSF) from TBI individuals. This has led to the investigation of myriads of brain-derived factors including humoral factors, cytokines, exosomes, and mi-RNAs. Further, the emerging information of interplay between the skeletal system and central nervous system, the roles of peripheral nerves and their neuropeptides in regulating bone regeneration, offers valuable insights for future research. This review consolidates the findings from both experimental and clinical studies, elucidating the potential mechanisms underlying enhanced fracture healing in concurrent TBI scenarios that may lay down a foundation to develop innovative therapies for fracture healing enhancement and conquer fracture non-union. The translational potential of this article. This review comprehensively summarizes the observations of accelerated fracture healing in the presence of traumatic brain injury from both preclinical and clinical studies. In addition, it also delineates potential cellular and molecular mechanisms. Further detailed investigation into its underlying mechanisms may reveal innovative orthopaedic intervention strategies to improve fracture healing and thus offering promising avenues for future translational applications.

Heterotopic Ossifications Following Intramedullary Stabilization of Femoral Fractures in Polytraumatized Patients

INTRODUCTION

Heterotopic ossifications (HOs) are a well-known complication following total hip arthroplasty. Yet only little is known about the development of HOs following a femoral fracture and intramedullary stabilization in polytraumatized patients. Thus, the present study aimed to investigate whether the development of HOs is being observed more frequently in patients suffering polytrauma compared to those with single-extremity trauma.

MATERIALS AND METHODS

The retrospective outcome study was conducted at our level I trauma center. All patients admitted from 2010 to 2020 were included if they (1) presented with multiple injuries (≥2 body regions), (2) had an Injury Severity Score ≥16, (3) suffered a femoral fracture, and (4) were treated with intramedullary stabilization. Furthermore, a control group was established to match the polytrauma group (sex, age), who were suffering from single-extremity trauma (femoral fracture) which was treated with intramedullary stabilization. Subsequently, X-rays of the hip were performed and evaluated for up to one-year post-trauma.

RESULTS

Our study group consisted of 36 patients in total (91.7% male; mean age 39.4 ± 17.4 years, range: 18-82 years). The polytrauma (PT) group included 12 patients (mean age 39.5 years, median ISS 28), whereas the control group (single-extremity-trauma) included 24 patients (mean age 39.3 years). We documented HOs in nine (75%) patients in the PT group vs. five (20.8%) patients in the single-extremity group (p = 0.03).

CONCLUSION

In this study, we were able to demonstrate that heterotopic ossifications are being observed significantly more frequently in patients suffering from polytrauma in comparison to patients with single-extremity trauma following intramedullary stabilization after a femoral fracture.

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.

Postoperative Exostosis: Ectopic Ossification After Pericardial Window Procedure

A 58-year-old Hispanic man had persistent epigastric pain after pericardial window procedure for viral pericarditis several years earlier. After review of a computed tomography scan, a calcified epigastric subcutaneous mass was detected. The patient elected to undergo surgical excision of the mass, which revealed a heterotopic ossified lesion arising from the inferior margin of the xiphoid process. The patient reported marked clinical improvement after the operation that has been sustained postoperatively. This case highlights the importance of considering heterotopic ossification as a potential cause of persistent pain after pericardial window procedure.

Ankylosis of the Shoulder After Traumatic Head Injury: A Late Presentation

Heterotopic ossification (HO) is the formation of bone in surrounding soft tissue. In the literature, several causes for this phenomenon were mentioned, trauma - including surgery, burns, and traumatic brain injury. HO in a shoulder is not frequently seen after traumatic brain injury (TBI). This relationship between TBI and HO can be explained in many ways. Surgical treatment entails many complications and important anatomical structures are at risk (e.g., axillary nerve). Surgeon must weigh both, risks and benefits and counsel the patient before taking a decision of surgical excision. We present a rare case of ankylosis of the shoulder following a traumatic brain injury.

A review of the biomarkers and in vivo models for the diagnosis and treatment of heterotopic ossification following blast and trauma-induced injuries

Heterotopic ossification (HO) is the process of de novo bone formation in non-osseous tissues. HO can occur following trauma and burns and over 60% of military personnel with blast-associated amputations develop HO. This rate is far higher than in other trauma-induced HO development. This suggests that the blast effect itself is a major contributing factor, but the pathway triggering HO following blast injury specifically is not yet fully identified. Also, because of the difficulty of studying the disease using clinical data, the only sources remain the relevant in vivo models. The aim of this paper is first to review the key biomarkers and signalling pathways identified in trauma and blast induced HO in order to summarize the molecular mechanisms underlying HO development, and second to review the blast injury in vivo models developed. The literature derived from trauma-induced HO suggests that inflammatory cytokines play a key role directing different progenitor cells to transform into an osteogenic class contributing to the development of the disease. This highlights the importance of identifying the downstream biomarkers under specific signalling pathways which might trigger similar stimuli in blast to those of trauma induced formation of ectopic bone in the tissues surrounding the site of the injury. The lack of information in the literature regarding the exact biomarkers leading to blast associated HO is hampering the design of specific therapeutics. The majority of existing blast injury in vivo models do not fully replicate the combat scenario in terms of blast, fracture and amputation; these three usually happen in one insult. Hence, this paper highlights the need to replicate the full effect of the blast in preclinical models to better understand the mechanism of blast induced HO development and to enable the design of a specific therapeutic to supress the formation of ectopic bone.

Mechanism of traumatic heterotopic ossification: In search of injury-induced osteogenic factors

Heterotopic ossification (HO) is a pathological condition of abnormal bone formation in soft tissue. Three factors have been proposed as required to induce HO: (a) osteogenic precursor cells, (b) osteoinductive agents and (c) an osteoconductive environment. Since Urist's landmark discovery of bone induction in skeletal muscle tissue by demineralized bone matrix, it is generally believed that skeletal muscle itself is a conductive environment for osteogenesis and that resident progenitor cells in skeletal muscle are capable of differentiating into osteoblast to form bone. However, little is known about the naturally occurring osteoinductive agents that triggered this osteogenic response in the first place. This article provides a review of the emerging findings regarding distinct types of HO to summarize the current understanding of HO mechanisms, with special attention to the osteogenic factors that are induced following injury. Specifically, we hypothesize that muscle injury‐induced up‐regulation of local bone morphogenetic protein‐7 (BMP‐7) level, combined with glucocorticoid excess‐induced down‐regulation of circulating transforming growth factor‐β1 (TGF‐β1) level, could be an important causative mechanism of traumatic HO formation.

Subarachnoid Osteoma of the Right Frontal Lobe

BACKGROUND

Intracranial osteoma arising from nonosseous tissue and surrounded by brain parenchyma is extremely rare. We report an intracranial osteoma surgical case with no heterotopic ossification.

CASE DESCRIPTION

A 32-year-old woman presented with headache, vertigo, and weakness. Preoperative neuroimaging revealed a spherelike, calcified intracranial lesion in the right frontal region. The bone-hard mass was completely removed by right frontal craniotomy; adhesion and invasion of the skull inner plate and dura were not found. The subarachnoid lesion was surrounded by right middle frontal gyrus, and the blood supply was from branches of pia mater. Postoperative histologic examination suggested an extensive intracranial ossification. At 6-month follow-up, the patient demonstrated a good recovery without any neurological deficits and no recurrence.

CONCLUSIONS

In this rare surgical case of subarachnoid osteoma, comprehensive preoperative neuroradiologic examinations, accurate surgical management of adjacent brain tissue, and vessel protection were the cornerstones of successful resection.

Traumatic brain injury enhances the formation of heterotopic ossification around the hip: an animal model study

INTRODUCTION

The incidence of heterotopic ossification (HO) is at its highest when trauma of the hip or pelvis concurs with traumatic brain injury (TBI). The pathogenic mechanisms underlying the neurogenic enhancement of the formation of HO remain, however, poorly understood. Hence, the goal of the present study was to develop a novel small animal model that combines hip and brain trauma that can prove the enhancement of HO around the hip after TBI.

MATERIALS AND METHODS

Forty male Wistar rats were divided into four groups, to undergo hip surgery alone (group 1), hip surgery + moderate TBI (group 2), hip surgery + severe TBI (group 3) and only severe TBI (group 4). The femoral canal was reamed up to 2 mm and a muscle lesion was made to simulate hip surgery. An established controlled cortical impact model was used to create a TBI. Twelve weeks after surgery, the hip with the proximal half of the femur and the pelvic bone was removed and subjected to micro-computed tomography (µCT) analysis. A quantitative analysis using a modified Brooker score as well as a quantitative analysis using a bone-to-tissue ratio was used.

RESULTS

No HO could be found in all the ten animals that did not undergo hip surgery (group 4). In the animals that did undergo surgery to the hip, no HO was found in only one animal (group 1). All the other animals developed HO. In this study, significantly more HO was found in animals that underwent an additional severe TBI.

CONCLUSION

The newly developed rat model, with a combined hip and brain trauma, showed an enhancement of the HO formation around the hip after severe TBI.

Humoral Factors From Musculoskeletal Polytrauma Patients Impair Antibacterial Responses Of Neutrophils In vitro

Polytrauma is associated with increased risk of sepsis, but the risk for implant infection is less clear. Neutrophil antibacterial responses are significantly reduced in polytrauma patients (n= 9, ISS≥15) for at least 5 days compared to healthy controls. Reduced neutrophil activity could influence implant infection in addition to sepsis.

Effect of neurokinin-1-receptor blockage on fracture healing in rats

Neurologic injury and selective blockage of sensory nerve endings is associated with impaired fracture healing, however, the role of specific neurotransmitters has not been sufficiently investigated. Our aim was to investigate the impact of specific Substance P-receptor blockage on fracture healing, since the neuropeptide Substance P has both neurogenic and osteogenic activity. After intramedullary stabilization, an isolated femur fracture was induced in 72 Sprague-Dawley rats. In the NK1-R group, the neurokinin-1-tachykinin receptor for substance P was blocked by a specific antagonist (SR140333) for the first two weeks after fracture induction. The control group only received vehicle. Gene-expression, histology, micro-computed tomography, and biomechanical tests were performed. NK1-receptor blocking suppressed osteocalcin expression at one week, collagen 1A2 expression at one and two weeks and collagen 2A1 expression at 2 weeks after fracture induction. Biomechanical testing revealed a significant reduction in maximal load to failure in the NK1-R group at 6 weeks (69.78 vs. 155.45 N, p = 0.029) and at 3 months (72.50 vs.176.33 N, p = 0.01) of fracture healing. Blocking the NK1-receptor suppresses gene expression in and reduces biomechanical strength of healing bone. Therefore, we assume a potential therapeutic relevance of Substance P in cases of disturbed fracture healing.

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.

Relationship between heterotopic ossification and traumatic brain injury: Why severe traumatic brain injury increases the risk of heterotopic ossification

Heterotopic ossification (HO) is a pathological phenomenon in which ectopic lamellar bone forms in soft tissues. HO involves many predisposing factors, including congenital and postnatal factors. Postnatal HO is usually induced by fracture, burn, neurological damage (brain injury and spinal cord injury) and joint replacement. Recent studies have found that patients who suffered from bone fracture combined with severe traumatic brain injury (S-TBI) are at a significantly increased risk for HO occurrence. Thus, considerable research focused on the influence of S-TBI on fracture healing and bone formation, as well as on the changes in various osteogenic factors with S-TBI occurrence. Brain damage promotes bone formation, but the exact mechanisms underlying bone formation and HO after S-TBI remain to be clarified. Hence, this article summarises the findings of previous studies on the relationship between S-TBI and HO and discusses the probable causes and mechanisms of HO caused by S-TBI. The translational potential of this article: A better understanding of the probable causes of traumatic brain injury-induced HO can provide new perspectives and ideas in preventing HO and may support to design more targeted therapies to reduce HO or enhance the bone formation.

A survey of proteomic biomarkers for heterotopic ossification in blood serum

Background

Heterotopic ossification (HO) is a significant problem for wounded warriors surviving high-energy blast injuries; however, currently, there is no biomarker panel capable of globally characterizing, diagnosing, and monitoring HO progression. The aim of this study was to identify biomarkers for HO using proteomic techniques and blood serum.

Methods

Isobaric tags for relative and absolute quantitation (iTRAQ) was used to generate a semi-quantitative global proteomics survey of serum from patients with and without heterotopic ossification. Leveraging the iTRAQ data, a targeted selection reaction monitoring mass spectrometry (SRM-MS) assay was developed for 10 protein candidates: alkaline phosphatase, osteocalcin, alpha-2 type I collagen, collagen alpha-1(V) chain isoform 2 preprotein, bone sialoprotein 2, phosphatidate phosphatase LPIN2, osteomodulin, protein phosphatase 1J, and RRP12-like protein.

Results

The proteomic survey of serum from both healthy and disease patients includes 1220 proteins and was enriched for proteins involved in the response to elevated platelet Ca⁺², wound healing, and extracellular matrix organization. Proteolytic peptides from three of the ten SRM-MS proteins, osteocalcin preprotein, osteomodulin precursor, and collagen alpha-1(v) chain isoform 2 preprotein from serum, are potential clinical biomarkers for HO.

Conclusions

This study is the first reported SRM-MS analysis of serum from individuals with and without heterotopic ossification, and differences in the serum proteomic profile between healthy and diseased subjects were identified. Furthermore, our results indicate that normal wound healing signals can impact the ability to identify biomarkers, and a multi-protein panel assay, including osteocalcin preproprotein, osteomodulin precursor, and collagen alpha-1(v) chain isoform 2 preprotein, may provide a solution for HO detection and monitoring.

Electronic supplementary material

The online version of this article (doi:10.1186/s13018-017-0567-2) contains supplementary material, which is available to authorized users.

Defining the Balance between Regeneration and Pathological Ossification in Skeletal Muscle Following Traumatic Injury

Heterotopic ossification (HO) is characterized by the formation of bone at atypical sites. This type of ectopic bone formation is most prominent in skeletal muscle, most frequently resulting as a consequence of physical trauma and associated with aberrant tissue regeneration. The condition is debilitating, reducing a patient's range of motion and potentially causing severe pathologies resulting from nerve and vascular compression. Despite efforts to understand the pathological processes governing HO, there remains a lack of consensus regarding the micro-environmental conditions conducive to its formation, and attempting to define the balance between muscle regeneration and pathological ossification remains complex. The development of HO is thought to be related to a complex interplay between factors released both locally and systemically in response to trauma. It develops as skeletal muscle undergoes significant repair and regeneration, and is likely to result from the misdirected differentiation of endogenous or systemically derived progenitors in response to biochemical and/or environmental cues. The process can be sequentially delineated by the presence of inflammation, tissue breakdown, adipogenesis, hypoxia, neo-vasculogenesis, chondrogenesis and ossification. However, exactly how each of these stages contributes to the formation of HO is at present not well understood. Our previous review examined the cellular contribution to HO. Therefore, the principal aim of this review will be to comprehensively outline changes in the local tissue micro-environment following trauma, and identify how these changes can alter the balance between skeletal muscle regeneration and ectopic ossification. An understanding of the mechanisms governing this condition is required for the development and advancement of HO prophylaxis and treatment, and may even hold the key to unlocking novel methods for engineering hard tissues.

PDGF is a potent initiator of bone formation in a tissue engineered model of pathological ossification

Heterotopic ossification (HO) is a debilitating condition defined by the rapid formation of bone in soft tissues. What makes HO fascinating is first the rate at which bone is deposited, and second the fact that this bone is structurally and compositionally similar to that of a healthy adult. If the mechanisms governing HO are understood, they have the potential to be exploited for the development of potent osteoinductive therapies. With this aim, a tissue‐engineered skeletal muscle was used model to better understand the role of inflammation on this debilitating phenomenon. It was shown that myoblasts could be divided into two distinct populations: myogenic cells and undifferentiated ‘reserve’ cells. Gene expression analysis of myogenic and osteoregulatory markers confirmed that ‘reserve’ cells were primed for osteogenic differentiation but had a reduced capacity for myogenesis. Osteogenic differentiation was significantly enhanced in the presence of platelet‐derived growth factor (PDGF)‐BB and bone morphogenetic protein 2 (BMP2), and correlated with conversion to a Sca‐1⁺/CD73⁺ phenotype. Alizarin red staining showed that PDGF‐BB promoted significantly more mineral deposition than BMP2. Finally, it was shown that PDGF‐induced mineralization was blocked in the presence of the pro‐inflammatory cytokines tumour necrosis factor‐α and interleukin 1. In conclusion, the present study identified that PDGF‐BB is a potent osteoinductive factor in a model of tissue‐engineered skeletal muscle, and that the osteogenic capacity of this protein was modulated in the presence of pro‐inflammatory cytokines. These findings reveal a possible mechanism by which HO develops following trauma. Importantly, these findings have implications for the induction and control of bone formation for regenerative medicine. © 2016 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd.

Heterotopic ossification following anti-NMDA receptor encephalitis: a case report

Background

Heterotopic ossification (HO) is defined as the formation of true bone tissue in non-osseous tissues. HO may occur under several conditions such as soft tissue injury, central nervous system injury and many other diseases like arthopathies, and vasculopathies. The underlying mechanisms of HO are not well elucidated. Anti-NMDA receptor encephalitis is a newly recognized autoimmune mediated disease which is predominant in young female patients with ovarian teratomas. Encephalitis complicated with HO has rarely been reported.

Case presentation

Here we report a case of anti-NMDA receptor encephalitis with severe muscle ossifications. A 15 years old female patient presented with fever, changed mental status of confusion, rigidity of the arms and legs, and oral-facial dyskinesias. Diagnosis of anti-NMDA receptor encephalitis was confirmed by detection of anti-NMDA receptor antibodies both in serum and CSF. Due to the severity of the disease, 3-weeks’ intensive care and mechanical ventilation were administrated for the patient. Image of pelvic CT and MRI of the patient showed dynamic changing process of HO. The muscles showed edema and scattered inflammation at the very beginning, and then gradually formed mature bone tissue.

Conclusions

Anti-NMDA receptor encephalitis often presents with severe neurologic symptoms and requires long time intensive care and mechanical ventilation, which makes the patient easily complicate with HO. More studies are required to elucidate the mechanisms of HO and more attention should be paid to patients with encephalitis who might develop severe muscle ossifications requiring early interventions.

Fibrocytes participate in the development of heterotopic ossification

Heterotopic ossification (HO) is a complication of musculoskeletal injury characterized by the formation of mature bone in soft tissues. The etiology of HO is unknown. We investigated the role of bone marrow derived progenitor cells in HO pathophysiology. We isolated the cells from HO specimens by cell explantation. Using flow cytometry and immunofluorescence microscopy, we found that 35 to 65% of the HO cells exhibit a bone marrow derived fibrocyte profile consisting in spindle-shaped morphology associated with type 1 pro-collagen and LSP1 expression. When cultured in osteogenic differentiation medium, active machinery for bone mineralization (high gene expression of Anx2, TNAP, and Pit-1), and calcium/phosphate deposits were found. Interestingly, interferon-alpha 2b significantly reduced the proliferation rate and COL1 gene expression in HO cells. We have characterized a novel subset of bone marrow derived progenitor cells in the HO specimens. The findings from this research study will provide new insights into the development of HO in burn patients.

Dealing With Catastrophic Outcomes and Amputations in the Mangled Limb

Successful management of the mangled extremity is difficult; however, recent advancements are changing the outcomes of these difficult cases. Multiple centers are working on new bionic limbs with real-time feedback and better performance parameters. Research progress, particularly in the military sector, has aided in our understanding of heterotopic ossification after devastating limb injuries. This progress has also allowed a better treatment program for the residual limb in surgery and postsurgery. It is an exciting time in the management and rehabilitation of amputated limbs, as both biologic and technological advancements are enabling better patient satisfaction. This article looks at some of these discoveries and how they are changing the treatment of the residual limb.

A new classification of peri-articular heterotopic ossification of the hip associated with neurological injury: 3D CT scan assessment and intra-operative findings

In this paper we propose a new classification of neurogenic peri-articular heterotopic ossification (HO) of the hip based on three-dimensional (3D) CT, with the aim of improving pre-operative planning for its excision. A total of 55 patients (73 hips) with clinically significant HO after either traumatic brain or spinal cord injury were assessed by 3D-CT scanning, and the results compared with the intra-operative findings. At operation, the gross pathological anatomy of the HO as identified by 3D-CT imaging was confirmed as affecting the peri-articular hip muscles to a greater or lesser extent. We identified seven patterns of involvement: four basic (anterior, medial, posterior and lateral) and three mixed (anteromedial, posterolateral and circumferential). Excellent intra- and inter-observer agreement, with kappa values > 0.8, confirmed the reproducibility of the classification system. We describe the different surgical approaches used to excise the HO which were guided by the 3D-CT findings. Resection was always successful. 3D-CT imaging, complemented in some cases by angiography, allows the surgeon to define the 3D anatomy of the HO accurately and to plan its surgical excision with precision.

Bioburden Increases Heterotopic Ossification Formation in an Established Rat Model

BACKGROUND

Heterotopic ossification (HO) develops in a majority of combat-related amputations wherein early bacterial colonization has been considered a potential early risk factor. Our group has recently developed a small animal model of trauma-induced HO that incorporates many of the multifaceted injury patterns of combat trauma in the absence of bacterial contamination and subsequent wound colonization.

QUESTIONS/PURPOSES

We sought to determine if (1) the presence of bioburden (Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus [MRSA]) increases the magnitude of ectopic bone formation in traumatized muscle after amputation; and (2) what persistent effects bacterial contamination has on late microbial flora within the amputation site.

METHODS

Using a blast-related HO model, we exposed 48 rats to blast overpressure, femur fracture, crush injury, and subsequent immediate transfemoral amputation through the zone of injury. Control injured rats (n = 8) were inoculated beneath the myodesis with phosphate-buffered saline not containing bacteria (vehicle) and treatment rats were inoculated with 1 × 10(6) colony-forming units of A baumannii (n = 20) or MRSA (n = 20). All animals formed HO. Heterotopic ossification was determined by quantitative volumetric measurements of ectopic bone at 12-weeks postinjury using micro-CT and qualitative histomorphometry for assessment of new bone formation in the residual limb. Bone marrow and muscle tissue biopsies were collected from the residual limb at 12 weeks to quantitatively measure the bioburden load and to qualitatively determine the species-level identification of the bacterial flora.

RESULTS

At 12 weeks, we observed a greater volume of HO in rats infected with MRSA (68.9 ± 8.6 mm(3); 95% confidence interval [CI], 50.52-85.55) when compared with A baumannii (20.9 ± 3.7 mm(3); 95% CI, 13.61-28.14; p < 0.001) or vehicle (16.3 ± 3.2 mm(3); 95% CI, 10.06-22.47; p < 0.001). Soft tissue and marrow from the residual limb of rats inoculated with A baumannii tested negative for A baumannii infection but were positive for other strains of bacteria (1.33 × 10(2) ± 0.89 × 10(2); 95% CI, -0.42 × 10(2)-3.08 × 10(2) and 1.25 × 10(6) ± 0.69 × 10(6); 95% CI, -0.13 × 10(6)-2.60 × 10(6) colony-forming units in bone marrow and muscle tissue, respectively), whereas tissue from MRSA-infected rats contained MRSA only (4.84 × 10(1) ± 3.22 × 10(1); 95% CI, -1.47 × 10(1)-11.1 × 10(1) and 2.80 × 10(7) ± 1.73 × 10(7); 95% CI, -0.60 × 10(7)-6.20 × 10(7) in bone marrow and muscle tissue, respectively).

CONCLUSIONS

Our findings demonstrate that persistent infection with MRSA results in a greater volume of ectopic bone formation, which may be the result of chronic soft tissue inflammation, and that early wound colonization may be a key risk factor.

CLINICAL RELEVANCE

Interventions that mitigate wound contamination and inflammation (such as early débridement, systemic and local antibiotics) may also have a beneficial effect with regard to the mitigation of HO formation and should be evaluated with that potential in mind in future preclinical studies.

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.

Neurological heterotopic ossification following spinal cord injury is triggered by macrophage-mediated inflammation in muscle

Neurological heterotopic ossification (NHO) is the abnormal formation of bone in soft tissues as a consequence of spinal cord or traumatic brain injury. NHO causes pain, ankyloses, vascular and nerve compression and delays rehabilitation in this high-morbidity patient group. The pathological mechanisms leading to NHO remain unknown and consequently there are no therapeutic options to prevent or reduce NHO. Genetically modified mouse models of rare genetic forms of heterotopic ossification (HO) exist, but their relevance to NHO is questionable. Consequently, we developed the first model of spinal cord injury (SCI)-induced NHO in genetically unmodified mice. Formation of NHO, measured by micro-computed tomography, required the combination of both SCI and localized muscular inflammation. Our NHO model faithfully reproduced many clinical features of NHO in SCI patients and both human and mouse NHO tissues contained macrophages. Muscle-derived mesenchymal progenitors underwent osteoblast differentiation in vitro in response to serum from NHO mice without additional exogenous osteogenic stimuli. Substance P was identified as a candidate NHO systemic neuropeptide, as it was significantly elevated in the serum of NHO patients. However, antagonism of substance P receptor in our NHO model only modestly reduced the volume of NHO. In contrast, ablation of phagocytic macrophages with clodronate-loaded liposomes reduced the size of NHO by 90%, supporting the conclusion that NHO is highly dependent on inflammation and phagocytic macrophages in soft tissues. Overall, we have developed the first clinically relevant model of NHO and demonstrated that a combined insult of neurological injury and soft tissue inflammation drives NHO pathophysiology.

Improved fracture healing in patients with concomitant traumatic brain injury: proven or not?

Over the last 3 decades, scientific evidence advocates an association between traumatic brain injury (TBI) and accelerated fracture healing. Multiple clinical and preclinical studies have shown an enhanced callus formation and an increased callus volume in patients, respectively, rats with concomitant TBI. Over time, different substances (cytokines, hormones, etc.) were in focus to elucidate the relationship between TBI and fracture healing. Until now, the mechanism behind this relationship is not fully clarified and a consensus on which substance plays the key role could not be attained in the literature. In this review, we will give an overview of current concepts and opinions on this topic published in the last decade and both clinical and pathophysiological theories will be discussed.

Serum EGF and NGF levels of patients with brain injury and limb fracture

OBJECTIVE

To explore the expression and significance of human epidermal growth factor (EGF) and nerve growth factor (NGF) in patients with knee osteoarthritis.

METHODS

RT-PCR and enzyme-linked immunosorbent assay were used to measure the serum EGF and NGF expression levels of patients with limb fracture and brain trauma injurry after 1 d, 3 d, 7 d, 14 d and the relationship between them was analyzed. The level was compared among the simple fracture group, traumatic brain injury group and the normal control group, with 40 cases in each group.

RESULTS

The serum NGF levels were significantly different among three groups. Serum NGF, EGF mRNA and protein levels gradually decreased with the increasing injury time in the limb fracture combined with brain injury group, traumatic brain injury group, the simple fracture group and the health control group (P<0.05).

CONCLUSIONS

The serum of NGF, EGF levels significantly increased when limb fracture combined with brain injury, so EGF and NGF may be involved in the process of fracture healing.

Heterotopic ossification after central nervous system trauma: A current review

Neurogenic heterotopic ossification (NHO) is a disorder of aberrant bone formation affecting one in five patients sustaining a spinal cord injury or traumatic brain injury. Ectopic bone forms around joints in characteristic patterns, causing pain and limiting movement especially around the hip and elbow. Clinical sequelae of neurogenic heterotopic ossification include urinary tract infection, pressure injuries, pneumonia and poor hygiene, making early diagnosis and treatment clinically compelling. However, diagnosis remains difficult with more investigation needed. Our pathophysiological understanding stems from mechanisms of basic bone formation enhanced by evidence of systemic influences from circulating humor factors and perhaps neurological ones. This increasing understanding guides our implementation of current prophylaxis and treatment including the use of non-steroidal anti-inflammatory drugs, bisphosphonates, radiation therapy and surgery and, importantly, should direct future, more effective ones.

Does traumatic brain injury result in accelerated mandibular fracture healing?

PURPOSE

To investigate the occurrence of accelerated bone healing evidenced by early callus formation in patients with mandibular fractures and traumatic brain injury (TBI).

MATERIALS AND METHODS

A retrospective cohort study was performed in patients who presented for mandibular fracture evaluation and management over a 6-year period. Subjects eligible for the study included those who underwent a computed tomographic examination of the mandible more than 2 weeks after the injury and had not undergone surgery with rigid internal fixation. TBI was used as the predictor variable. Time to callus formation as detected on computed tomographic scans was recorded as the primary outcome variable. Other variables considered included age, gender, coma duration, and fracture distribution. Appropriate statistical analyses were performed to determine the influencing factors.

RESULTS

Forty-five patients with mandibular fractures (24 with severe TBI and 21 without TBI) were retrospectively analyzed. Twelve patients with TBI and 6 without TBI exhibited a visible callus on their computed tomographic scans. Statistical analysis showed no significant differences in age, gender, examination time, and fracture distribution between the groups. Cox proportional hazards regression analysis indicated a positive correlation of time to callus formation with TBI and coma duration but not with age, gender, and fracture distribution.

CONCLUSIONS

These findings suggest that patients with severe TBI and mandibular fractures exhibit increased fracture healing as evidenced by early callus formation. A more exhaustive study is required to advance the understanding of this phenomenon and provide additional clinical significance.

The effects of an injury to the brain on bone healing and callus formation in young adults with fractures of the femoral shaft

In patients with traumatic brain injury and fractures of long bones, it is often clinically observed that the rate of bone healing and extent of callus formation are increased. However, the evidence has been unconvincing and an association between such an injury and enhanced fracture healing remains unclear. We performed a retrospective cohort study of 74 young adult patients with a mean age of 24.2 years (16 to 40) who sustained a femoral shaft fracture (AO/OTA type 32A or 32B) with or without a brain injury. All the fractures were treated with closed intramedullary nailing. The main outcome measures included the time required for bridging callus formation (BCF) and the mean callus thickness (MCT) at the final follow-up. Comparative analyses were made between the 20 patients with a brain injury and the 54 without brain injury. Subgroup comparisons were performed among the patients with a brain injury in terms of the severity of head injury, the types of intracranial haemorrhage and gender. Patients with a brain injury had an earlier appearance of BCF (p < 0.001) and a greater final MCT value (p < 0.001) than those without. There were no significant differences with respect to the time required for BCF and final MCT values in terms of the severity of head injury (p = 0.521 and p = 0.153, respectively), the types of intracranial haemorrhage (p = 0.308 and p = 0.189, respectively) and gender (p = 0.383 and p = 0.662, respectively).

These results confirm that an injury to the brain may be associated with accelerated fracture healing and enhanced callus formation. However, the severity of the injury to the brain, the type of intracranial haemorrhage and gender were not statistically significant factors in predicting the rate of bone healing and extent of final callus formation.

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.

Troublesome heterotopic ossification after central nervous system damage: a survey of 570 surgeries

Background

Heterotopic ossification (HO) is a frequent complication after central nervous system (CNS) damage but has seldom been studied. We aimed to investigate features of HO for the first time in a large sample and the rate of early recurrence of HO in terms of the time of surgery.

Methodology/Principal Findings

We retrospectively analyzed data from an anonymous prospective survey of patients undergoing surgery between May 1993 and November 2009 in our institution for troublesome HO related to acquired neurological disease. Demographic and HO characteristics and neurological etiologies were recorded. For 357 consecutive patients, we collected data on 539 first surgeries for HO (129 surgeries for multiple sites). During the follow-up, recurrences requiring another surgery appeared in 31 cases (5.8% [31/539]; 95% confidence interval [CI]: 3.8%–7.8%; 27 patients). Most HO requiring surgery occurred after traumatic brain injury (199 patients [55.7%]), then spinal cord injury (86 [24.0%]), stroke (42 [11.8%]) and cerebral anoxia (30 [8.6%]). The hip was the primary site of HO (328 [60.9%]), then the elbow (115 [21.3%]), knee (77 [14.3%]) and shoulder (19 [3.5%]). For all patients, 181 of the surgeries were performed within the first year after the CNS damage, without recurrence of HO. Recurrence was not associated with etiology (p = 0.46), sex (p = 1.00), age at CNS damage (p = 0.2), multisite localization (p = 0.34), or delay to surgery (p = 0.7).

Conclusions/Significance

In patients with CNS damage, troublesome HO and recurrence occurs most frequently after traumatic brain injury and appears frequently in the hip and elbow. Early surgery for HO is not a factor of recurrence.