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

Risk factors for the development of heterotopic ossification of the elbow in children with untreated chronic Monteggia fractures: a radiographic review of 274 cases

BACKGROUND

The factors predicting the development of heterotopic ossification (HO) of the elbow in children with untreated chronic Monteggia fractures (UCMFs) remained unclear. This multicentre study was designed to evaluate the radiographic data from paediatric patients with UCMFs and to identify the risk factors for HO formation and their radiographic characteristics.

MATERIALS AND METHODS

We retrospectively reviewed 274 patients (mean age at injury: 5.82 ± 2.62 years) with UCMFs with all types of anterior (group A) and non-anterior (group B) radial head (RH) dislocations. Radiographs were used to assess the presence, size and bone density of HO. The risk factors evaluated included age at injury, sex, laterality, interval from injury to diagnosis, presence of radial or median nerve injury, immobilization of the fractured ulna after injury, direction of RH dislocation and distance of RH dislocation (DD-RH). The results were compared with 76 patient demographics-matched paediatric acute Monteggia fractures (PAMFs) undergoing surgery within 48 h after injury.

RESULTS

The HO rate (13.1%) in children with UCMFs was significantly higher than that (0%) in children with PAMFs (P = 0.001). The incidence of HO (14.5%) in group A was significantly higher than that (0%) in group B (P = 0.032). Age at injury and DD-RH were confirmed as risk factors for HO in patients with UCMFs by both univariate and logistic regression analyses (P < 0.05). Receiver operating characteristic curve analysis and chi-squared analysis indicated that age at injury > 6.78 years and DD-RH < 1.59-fold of the narrowest radial neck width were the cut-off values for an increased HO rate in patients with UCMFs (P < 0.05). Increased age at injury (P = 0.041) and interval from injury to diagnosis (P = 0.006) were associated with high-bone density HO.

CONCLUSIONS

Patients with UCMFs with anterior RH dislocations, age at injury > 6.78 years, and DD-RH < 1.59-fold of the narrowest radial neck width were more likely to develop HO. The bone density of HO increases with age at injury and interval from injury to diagnosis. Timely RH reduction after acute injury may prevent HO.

LEVEL OF EVIDENCE

III.

Heterotopic ossification (HO) prophylaxis in total hip arthroplasty (THA): A systematic review of level I and level II evidence since 2000

Introduction

Heterotopic ossification (HO) is a somewhat common occurrence after total hip arthroplasty (THA), particularly with certain approaches. This complication can be detrimental to the success of the surgical outcome. Indomethacin and radiotherapy remain common treatment modalities; however, no true gold-standard treatment is universally agreed upon. This study aims to evaluate Level I and Level II evidence for treatment practices of HO prophylaxis since 2000.

Methods

To evaluate HO prophylaxis in total hip arthroplasty, a search was conducted across MEDLINE/Pubmed, Cochrane, and Embase databases using keywords and Medical Subject Heading (MeSH) terms. Titles and abstracts were screened for eligibility for inclusion criteria. Full texts were screened and included if they met eligibility criteria.

Results

HO chemical prophylaxis was more effective than no HO prophylaxis, except for aspirin. Multiple NSAIDs showed equivalence and better side effect profiles than indomethacin. No one superior NSAID was found, and numerous modalities showed efficacy. The most effective dosages of radiation therapy and combination therapy remain unclear. Additionally, both etidronate and salmon calcitonin showed benefit in preventing HO in one study each.

Conclusion

Radiation, NSAIDs, and combination therapy all showed efficacy as HO prophylaxis modalities. HO prophylaxis treatment and modalities should be guided upon patient and surgical factors such as surgical approach, side effects and tolerability of modalities, comorbidities, and available facility resources to optimize the prevention of HO.Level of evidence: Level IV Therapeutic.

Heterotopic ossification Post-Guillain-Barre syndrome in Saudi Arabia: a case report

Background

Heterotopic ossification (HO) is the formation of bone within the soft tissues. It can be a complication of Guillain-Barre syndrome (GBS). There are many risk factors for HO, including male sex, mechanical ventilation, and neurogenic trauma. Myelin and axons are the main targets and areas of injury in GBS, an autoimmune-inflammatory neuropathy. Literature shows that this may possibly be associated with the initial administration of the COVID-19 vaccine and GBS.

Presentation of the case

A 27-year-old male was diagnosed with bile reflux gastritis. Days later, he presented to the emergency room (ER) with progressive weakness and a critical condition that required ICU. The patient undergoes intubation and remains in the ICU for 4 months. The patient, after extensive rehabilitation, started to complain of left hip pain and limitations of motion. Radiographs confirmed the HO diagnosis. Past drug history showed patients received a single dose of the COVID-19 vaccine 15 days before presentation to the ER.

Discussion

There is no clear association between the COVID-19 vaccination and GBS. HO is the formation of abnormal bone within soft tissue. HO post-GBS usually affects large joints like the hips, knees, and shoulders. Researchers poorly understand the pathogenesis of GBS.

Conclusion

Despite the absence of a definitive correlation between GSB and the COVID-19 vaccine. Physicians should maintain a state of suspicion while treating patients with a progressive weakness. Additional research is required.

Management of Medical Complications during the Rehabilitation of Moderate-Severe Traumatic Brain Injury

According to the Centers for Disease Control, in 2019, there were approximately 223,135 hospitalizations in the United States related to traumatic brain injury (TBI). If not managed properly, these patients can suffer complications with significant negative implications with respect to morbidity, mortality, and long-term functional prognosis. It is imperative that medical providers who care for patients with TBI across the entire spectrum of care readily diagnose and treat the sequela associated with moderate-severe brain trauma. This article will focus on some of the key medical issues that providers may encounter during acute inpatient rehabilitation.

Intersections of Fibrodysplasia Ossificans Progressiva and Traumatic Heterotopic Ossification

Heterotopic ossification (HO) is a debilitating pathology where ectopic bone develops in areas of soft tissue. HO can develop as a consequence of traumatic insult or as a result of dysregulated osteogenic signaling, as in the case of the orphan disease fibrodysplasia ossificans progressiva (FOP). Traumatic HO (tHO) formation is mediated by the complex interplay of signaling between progenitor, inflammatory, and nerve cells, among others, making it a challenging process to understand. Research into the pathogenesis of genetically mediated HO (gHO) in FOP has established a pathway involving uninhibited activin-like kinase 2 receptor (ALK2) signaling that leads to downstream osteogenesis. Current methods of diagnosis and treatment lag behind pre-mature HO detection and progressive HO accumulation, resulting in irreversible decreases in range of motion and chronic pain for patients. As such, it is necessary to draw on advancements made in the study of tHO and gHO to better diagnose, comprehend, prevent, and treat both.

Aetiology, risk factors and treatment of typical and atypical pressure ulcers in patients with traumatic brain injury: A narrative review

Pressure ulcers are one of the leading complications in bedridden patients that result in multiple burdens on healthcare systems and patients (11 billion dollars/year). The prevalence of pressure ulcers in traumatic brain injury patients is 1.5-fold compared with the other bedridden patients. Moreover, critical traumatic brain injury patients who are admitted to the intensive care unit experience severe pressure ulcers and further complications. The motor/sensory disabilities and low supplementation and oxygenation to the pressured side were the main mechanisms of the typical pressure ulcers. Intellectual evaluation is the first essential step to prevent the development of pressure ulcers in high-risk patients. Till now, different scales, including Injury Scale Score and Braden Scale Score, have been provided to assess the pressure ulcer. Since low stages of pressure ulcers heal rapidly, traumatic brain injury patients require a periodical assessment to prevent further developments timely. Alongside different procedures provided to prevent and treat any pressure ulcer, traumatic brain injury patients required additional specific protections. For the first line, fast and efficient rehabilitation repairs motor/sensory disabilities and decreases the chance of pressure ulcer. Our review indicated that pressure ulcer in traumatic brain injury had several complex mechanisms that demand special care. Therefore, further studies are required to address these mechanisms and prevent their progression to typical and atypical pressure ulcers.

Interorgan communication in neurogenic heterotopic ossification: the role of brain-derived extracellular vesicles

Brain-derived extracellular vesicles participate in interorgan communication after traumatic brain injury by transporting pathogens to initiate secondary injury. Inflammasome-related proteins encapsulated in brain-derived extracellular vesicles can cross the blood‒brain barrier to reach distal tissues. These proteins initiate inflammatory dysfunction, such as neurogenic heterotopic ossification. This recurrent condition is highly debilitating to patients because of its relatively unknown pathogenesis and the lack of effective prophylactic intervention strategies. Accordingly, a rat model of neurogenic heterotopic ossification induced by combined traumatic brain injury and achillotenotomy was developed to address these two issues. Histological examination of the injured tendon revealed the coexistence of ectopic calcification and fibroblast pyroptosis. The relationships among brain-derived extracellular vesicles, fibroblast pyroptosis and ectopic calcification were further investigated in vitro and in vivo. Intravenous injection of the pyroptosis inhibitor Ac-YVAD-cmk reversed the development of neurogenic heterotopic ossification in vivo. The present work highlights the role of brain-derived extracellular vesicles in the pathogenesis of neurogenic heterotopic ossification and offers a potential strategy for preventing neurogenic heterotopic ossification after traumatic brain injury. Brain-derived extracellular vesicles (BEVs) are released after traumatic brain injury. These BEVs contain pathogens and participate in interorgan communication to initiate secondary injury in distal tissues. After achillotenotomy, the phagocytosis of BEVs by fibroblasts induces pyroptosis, which is a highly inflammatory form of lytic programmed cell death, in the injured tendon. Fibroblast pyroptosis leads to an increase in calcium and phosphorus concentrations and creates a microenvironment that promotes osteogenesis. Intravenous injection of the pyroptosis inhibitor Ac-YVAD-cmk suppressed fibroblast pyroptosis and effectively prevented the onset of heterotopic ossification after neuronal injury. The use of a pyroptosis inhibitor represents a potential strategy for the treatment of neurogenic heterotopic ossification.

[Research progress on mechanism of traumatic brain injury promoting fracture healing]

Objective

To summarize the research progress on the mechanism related to traumatic brain injury (TBI) to promote fracture healing, and to provide theoretical basis for clinical treatment of fracture non-union.

Methods

The research literature on TBI to promote fracture healing at home and abroad was reviewed, the role of TBI in fracture healing was summarized from three aspects of nerves, body fluids, and immunity, to explore new ideas for the treatment of fracture non-union.

Results

Numerous studies have shown that fracture healing is faster in patients with fracture combined with TBI than in patients with simple fracture. It is found that the expression of various cytokines and hormones in the body fluids of patients with fracture and TBI is significantly higher than that of patients with simple fracture, and the neurofactors released by the nervous system reaches the fracture site through the damaged blood-brain barrier, and the chemotaxis and aggregation of inflammatory cells and inflammatory factors at the fracture end of patients with combined TBI also differs significantly from those of patients with simple fracture. A complex network of humoral, neural, and immunomodulatory networks together promote regeneration of blood vessels at the fracture site, osteoblasts differentiation, and inhibition of osteoclasts activity.

Conclusion

TBI promotes fracture healing through a complex network of neural, humoral, and immunomodulatory, and can treat fracture non-union by intervening in the perifracture microenvironment.

HMGB1 Promotes Accelerated Fracture Healing in Traumatic Brain Injury through PINK1/Parkin-Mediated Mitochondrial Autophagy

We aimed to investigate the mechanism of high mobility group box 1 (HMGB1) in the accelerated fracture healing process during Traumatic brain injury (TBI). The lateral ventricles of mice in the TBI model group were injected with adenovirus-packaged short hairpin RNA (shRNA)-HMGB1 or overexpressing (ov)-HMGB1 vector. We found HMGB1 levels were higher in bone tissue at the fracture end of TBI combined with fracture model mice. Compared with the TBI combined with fracture model mice, the mice in the ov-HMGB1 group healed faster and the expression levels of mitochondrial autophagy-related proteins were higher. Compared to the ov-HMGB1 group, mice in the ov-HMGB1 + autophagy inhibitor cyclosporin A (CsA) and ov-HMGB1 + shRNA-phosphatase and tensin homolog-induced kinase 1 (PINK1) groups showed slower healing and lower expression of mitochondrial autophagy-associated proteins. The expression of osteocalcin (OCN), SOX9, and bone morphogenetic protein (BMP)-2 in bone tissue at the fracture end of the ov-HMGB1 + shRNA-PINK1 group was lower than that in the ov-HMGB1 group. The mRNA expression levels of chondrogenic differentiation markers in bone tissue at the fracture end of the ov-HMGB1 + shRNA-PINK1 group were lower than those in the ov-HMGB1 group. Fracture healing was accelerated during TBI, especially when HMGB1 was highly expressed, and HMGB1 promote accelerated fracture healing during TBI through PINK1/Parkin-mediated mitochondrial autophagy.

Regulation of Bone by Mechanical Loading, Sex Hormones, and Nerves: Integration of Such Regulatory Complexity and Implications for Bone Loss during Space Flight and Post-Menopausal Osteoporosis

During evolution, the development of bone was critical for many species to thrive and function in the boundary conditions of Earth. Furthermore, bone also became a storehouse for calcium that could be mobilized for reproductive purposes in mammals and other species. The critical nature of bone for both function and reproductive needs during evolution in the context of the boundary conditions of Earth has led to complex regulatory mechanisms that require integration for optimization of this tissue across the lifespan. Three important regulatory variables include mechanical loading, sex hormones, and innervation/neuroregulation. The importance of mechanical loading has been the target of much research as bone appears to subscribe to the "use it or lose it" paradigm. Furthermore, because of the importance of post-menopausal osteoporosis in the risk for fractures and loss of function, this aspect of bone regulation has also focused research on sex differences in bone regulation. The advent of space flight and exposure to microgravity has also led to renewed interest in this unique environment, which could not have been anticipated by evolution, to expose new insights into bone regulation. Finally, a body of evidence has also emerged indicating that the neuroregulation of bone is also central to maintaining function. However, there is still more that is needed to understand regarding how such variables are integrated across the lifespan to maintain function, particularly in a species that walks upright. This review will attempt to discuss these regulatory elements for bone integrity and propose how further study is needed to delineate the details to better understand how to improve treatments for those at risk for loss of bone integrity, such as in the post-menopausal state or during prolonged space flight.

Pathogenesis of acquired heterotopic ossification: Risk factors, cellular mechanisms, and therapeutic implications

Heterotopic ossification (HO), including hereditary and acquired HO, is the formation of extraskeletal bone in skeletal muscle and surrounding soft tissues. Acquired HO is often caused by range of motion, explosion injury, nerve injury or burns. Severe HO can lead to pain and limited joint activity, affecting functional rehabilitation and quality of life. Increasing evidence shows that inflammatory processes and mesenchymal stem cells (MSCs) can drive HO. However, explicit knowledge about the specific mechanisms that result in HO and related cell precursors is still limited. Moreover, there are no effective methods to prevent or reduce HO formation. In this review, we provide an update of known risk factors and relevant cellular origins for HO. In particular, we focus on the underlying mechanisms of MSCs in acquired HO, which follow the osteogenic program. We also discuss the latest therapeutic value and implications for acquired HO. Our review highlights the current gaps in knowledge regarding the pathogenesis of acquired HO and identifies potential targets for the prevention and treatment of HO.

Accelerated tibia fracture healing in traumatic brain injury in accordance with increased hematoma formation

BACKGROUND

Traumatic brain injury (TBI) has been known to accelerate bone healing. Many cells and molecules have been investigated but the exact mechanism is still unknown. The neuroinflammatory state of TBI has been reported recently. We aimed to investigate the effect of TBI on fracture healing in patients with tibia fractures and assess whether the factors associated with hematoma formation changed more significantly in the laboratory tests in the fractures accompanied with TBI.

METHODS

We retrospectively investigated patients who were surgically treated for tibia fractures and who showed secondary bone healing. Patients with and without TBI were divided for comparative analyses. Radiological parameters were time to callus formation and the largest callus ratio during follow-up. Preoperative levels of complete blood count and chemical battery on admission were measured in all patients. Subgroup division regarding age, gender, open fracture, concomitant fracture and severity of TBI were compared.

RESULTS

We included 48 patients with a mean age of 44.9 (range, 17-78), of whom 35 patients (72.9%) were male. There were 12 patients with TBI (Group 1) and 36 patients without TBI (Group 2). Group 1 showed shorter time to callus formation (P <  0.001), thicker callus ratio (P = 0.015), leukocytosis and lymphocytosis (P ≤ 0.028), and lower red blood cell counts (RBCs), hemoglobin, and hematocrit (P <  0.001). Aging and severity of TBI were correlated with time to callus formation and callus ratio (P ≤ 0.003) while gender, open fracture, and concomitant fracture were unremarkable.

CONCLUSION

Tibia fractures with TBI showed accelerated bone healing and superior measurements associated with hematoma formation (lymphocytes, RBCs, hemoglobin, hematocrit). Promoted fracture healing in TBI was correlated with the enhanced proinflammatory state.

LEVEL OF EVIDENCE

III, case control study.

Risk Factors for the Development of Heterotopic Ossification Following Acetabular Fractures: A Systematic Review

BACKGROUND

Heterotopic ossification (HO) following acetabular fractures is a common complication that may affect clinical outcomes. However, the effects of prophylactic treatment with nonsteroidal anti-inflammatory drugs or radiation therapy remain controversial. While several factors have been related to the development of HO, there is considerable uncertainty regarding their importance or effect size in the setting of acetabular surgery. Therefore, this systematic review aims to summarize the risk factors for HO following the operative fixation of acetabular fractures and clarify their interrelationships.

METHODS

In accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, PubMed, MEDLINE, Embase, and CINAHL databases were searched from inception to February 2021. Studies that assessed factors related to HO development among patients with operatively repaired acetabular fractures were included. Outcomes were risk factors and their effect size (p values, odds ratios, and 95% confidence intervals).

RESULTS

Twenty-five studies and 1 conference abstract with a total of 3,940 patients were included. The following risk factors for HO were identified. Patient factors were increased body mass index, male sex, and increased age. Injury factors were intensive care unit (ICU) admission and length of stay, non-ICU hospitalization for &gt;10 days, the need for mechanical ventilation for ≥2 days, abdominal and/or chest injuries, the number and type of associated fractures, traumatic brain injuries, T-type acetabular fractures, pelvic ring injuries, and hip dislocation. Care factors were a delay to surgery, extensile and posterior surgical approaches to the hip, trochanteric osteotomy, postoperative step-off of &gt;3 mm, and a delay to prophylaxis following injury or surgery. Ethnicity, Injury Severity Score, cause of the fracture, femoral head injuries, degloving injuries, comminution, intra-articular debris, the type of bone void filler, gluteus minimus muscle preservation, prolonged operative time, and intraoperative patient position were not risk factors for developing HO.

CONCLUSIONS

HO following operative fixation of acetabular fractures is not uncommon, with severe-grade HO associated with substantial disability. Careful consideration of the risk factor effect sizes and interdependencies could aid physicians in identifying patients at risk for developing HO and guide their prophylactic management. The results of this study could establish a framework for future studies.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Are there really specific risk factors for heterotopic ossifications? A case report of 'non-risk factor' after total hip replacement

Femoral neck fractures are one of the most common fractures in the elderly population. Due to frequent complications of the fixation of these fractures, patients are more and more often eligible for hip replacement surgery. One of the most frequently mentioned postoperative complication is the formation of heterotopic ossification. This case report describes as a 70-year-old male patient that presented with an old hip fracture accompanied by a mild craniocerebral trauma. The patient underwent total cementless hip arthroplasty followed by rehabilitation. At 8 months after surgery, the patient was diagnosed with Brooker IV° heterotopic ossification in the area of the operated hip joint. Due to the persistent pain and complete loss of mobility in the operated joint, computed tomography imaging was performed and the patient was recommended for a revision surgery. The procedure was performed 14 months after the original surgical treatment, resulting in a significant improvement in the range of motion and reduction of pain.

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.

The effect of traumatic brain injury on bone healing from a novel exosome centered perspective in a mice model

BACKGROUND

In patients with traumatic brain injury (TBI) combined with long bone fracture, the fracture healing is always faster than that of patients with single fracture, which is characterized by more callus growth at the fracture site and even ectopic ossification. Exosomes are nanoscale membrane vesicles secreted by cells, which contain cell-specific proteins, miRNAs, and mRNAs.

METHODS

In this study, we used exosomes as the entry point to explore the mechanism of brain trauma promoting fracture healing. We established a model of tibia fracture with TBI in mice to observe the callus growth and expression of osteogenic factors at the fracture site. Blood samples of model mice were further collected, exosomes in plasma were extracted by ultra-centrifugation method, and then identified and acted on osteoblasts cultured in vitro. The effects of exosomes on osteoblast differentiation at the cell, protein and gene levels were investigated by Western Blot and q-PCR, respectively. Furthermore, miRNA sequencing of exosomes was performed to identify a pattern of miRNAs that were present at increased or decreased levels.

RESULTS

The results suggested that plasma exosomes after TBI had the ability to promote the proliferation and differentiation of osteoblasts, which might be due to the increased expression of osteoblast-related miRNA in exosomes. They were transmitted to the osteoblasts at the fracture site, so as to achieve the role of promoting osteogenic differentiation.

CONCLUSION

The TBI-derived exosomes may have potential applications for promoting fracture healing in future.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Plasma exosomes early after TBI have the ability to promote osteoblast proliferation and differentiation. The mechanism may be achieved by miRNA in exosomes. Plasma exosomes may be used as breakthrough clinical treatment for delayed or non-union fractures.

Local and Systemic Factors Drive Ectopic Osteogenesis in Regenerating Muscles of Spinal-Cord-Injured Mice in a Lesion-Level-Dependent Manner

Neuroimmune dysfunction is thought to promote the development of several acute and chronic complications in spinal cord injury (SCI) patients. Putative roles for adrenal stress hormones and catecholamines are increasingly being recognized, yet how these adversely affect peripheral tissue homeostasis and repair under SCI conditions remains elusive. Here, we investigated their influence in a mouse model of SCI with acquired neurogenic heterotopic ossification. We show that spinal cord lesions differentially influence muscular regeneration in a level-dependent manner and through a complex multi-step process that creates an osteopermissive environment within the first hours of injury. This cascade of events is shown to critically involve adrenergic signals and drive the acute release of the neuropeptide, substance P. Our findings generate new insights into the kinetics and processes that govern SCI-induced deregulations in skeletal muscle homeostasis and regeneration, thereby aiding the development of sequential therapeutic strategies that can prevent or attenuate neuromusculoskeletal complications in SCI patients.

Desloratadine inhibits heterotopic ossification by suppression of BMP2-Smad1/5/8 signaling

Heterotopic ossification (HO) is a pathological condition in which ectopic bone forms within soft tissues such as skeletal muscle. Human platelet-derived growth factor receptor α positive (PDGFRα+) cells, which were proved to be the original cells of HO were incubated in osteogenic differentiation medium with Food and Drug Administration-approved compounds. Alkaline phosphatase activity was measured as a screening to inhibit osteogenic differentiation. For the compounds which inhibited osteogenic differentiation of PDGFRα+ cells, we examined dose dependency of its effect using alizarin red S staining and its cell toxicity using WST-8. In addition, regulation of bone morphogenetic proteins (BMP)-Smad signaling which is the major signal of osteogenic differentiation was investigated by Western blotting to elucidate the mechanism of osteogenesis inhibitory effect by the compound. In vivo experiment, complete transverse incision of Achilles tendons in mice was made and mice were fed the compound by mixing with drinking water after operation. Ten weeks after operation, we assessed and quantified HO by micro-computed tomography scan. Intriguingly, we discovered desloratadine inhibited osteogenic differentiation of PDGFRα+ cells using the drug repositioning method. Desloratadine inhibited osteogenic differentiation of the cells dose dependently without cell toxicity. Desloratadine suppressed phosphorylation of Smad1/5/8 induced by BMP2 in PDGFRα+ cells. In Achilles tenotomy mice model, desloratadine treatment significantly inhibited ectopic bone formation compared with control. In conclusion, we discovered desloratadine inhibited osteogenic differentiation using human PDGFRα+ cells and proved its efficacy using Achilles tenotomy ectopic bone formation model in vivo. Our study paved the way to inhibit HO in early clinical use because of its guaranteed safety.

Bone defects are repaired by enhanced osteogenic activity of the induced membrane: a case report and literature review

Background

The induced membrane technique (IMT) is an effective strategy to repair bone defects and involves a two-stage set of surgical procedures. Although the IM has osteogenic activity, bone grafting is necessary in standard IMT. Bone defects repaired completely by osteogenic activity of the IM alone without bone grafts are rare.

Case presentation

We present a case of infected fractures and bone defects of the ulna and radius treated with IMT. After the first stage using polymethylmethacrylate (PMMA) beads, X-rays showed that new callus developed after 2 to 4 months, and the defects were repaired completely by 5 months. We also present a literature review on spontaneous osteogenesis of the IM in patients.

Conclusions

We present a case of infected ulnar and radial bone defects that healed by 5 months after the first stage of the IMT using a PMMA spacer. This finding suggests that local associated inflammatory reactions and bone tissue might enhance the osteogenic activity of the IM, causing spontaneous healing of bone defects. This appears to be the first such case reported in the literature.

Multi-center observational study on occurrence and related clinical factors of neurogenic heterotopic ossification in patients with disorders of consciousness

Aims: to assess occurrence and clinical correlates of neurogenic heterotopic ossifications (NHO) in patients with prolonged disorder of consciousness (DoC).Design: multi-center cross-sectional observational study.Setting: 23 intensive neurorehabilitation units.Subjects: 287 patients with prolonged disorder of consciousness (DoC; 150 in vegetative state, VS, and 128 in minimally conscious state, MCS) of different etiology (vascular = 125, traumatic = 83, anoxic = 56, others = 14).Main Measures: clinical evidence of NHO confirmed by standard radiological and/or sonographic evaluation; Coma Recovery Scale-Revised; Disability Rating Scale (DRS); Early Rehabilitation Barthel Index; presence of ventilator support, spasticity, bone fractures and paroxysmal sympathetic hyperactivity.Results: 31 patients (11.2%) presented NHO. Univariate analyses showed that NHO was associated with VS diagnosis, traumatic etiology, high DRS category and total score, and high occurrence of limb spasticity and bone fractures. A cluster-corrected binary logistic regression model (excluding spasticity available in a subset of patients) showed that only lower DRS total score and presence of bone fractures were independently associated with NHO.Conclusions: NHO are relatively frequent in patients with DoC, and are independently associated with functional disability, bone fractures and spasticity. These findings contribute to identifying patients with DoC prone to develop NHO and requiring special interventions to improve functional recovery.

The Surgical Management of the Rare Neurogenic Myositis Ossificans of the Hip: A Report of 3 Cases

Introduction:

Myositis ossificans (MO) is a benign non-neoplastic condition in which heterotopic bone formation occurs in soft tissues. Neurogenic MO is one variant of MO where the lesion is a result of neurological disorders, including brain and spinal cord injuries, especially when followed by immobility and spasticity. MO can also be a result of direct trauma or even genetic mutations.

Case Report:

We present three cases of young men (16, 37, and 22-year-old) who developed MO of the hip joint following brain or spinal cord injuries. One of them had also sustained a direct trauma to the affected hip joint at the time of the accident. All three patients presented with inability to walk independently due to diminished range of motion at the affected joint. X-rays and computerized tomography (CT) scans with 3-dimentional (3D) reconstruction suggested the diagnosis of MO, but the serum alkaline phosphatase was within normal limits at the time of presentation. The first case had bilateral involvement with unmistakable separation between the heterotopic bone formation and the frank hip joints on CT. This patient underwent successful staged excision of the ossifications. The second patient had unilateral hip joint involvement with the absence of clear separation between the heterotopic bone formation and the hip joint, thus, underwent total hip replacement for the affected side as excision was not possible. The third patienthad unilateral hip joint involvement and underwent excision of the ossification with dynamic hip screw insertion after sustaining a stable intertrochanteric fracture intraoperatively. Postoperatively, all three patients received physiotherapy and oral indomethacin. Upon recovery, they were able to walk independently with a near-normal range of motion at the hip joint. There was no evidence of recurrence upon follow-up visits, and CT scans in patients I and II. Follow-ups for patient III were not possible as the patient died 1 month after surgery due to pulmonary embolism.

Conclusion:

The surgical management of MO is indicated when non-operative methods fail to provide an adequate range of motion around the hip joint. Pre-operative assessment utilizing 3D-CT scans proved to be essential in dictating the appropriate surgical approach. During post-operative follow-ups, the physiotherapy and oral indomethacin provided additional improvement in outcome and patients’ satisfaction.

Melatonin Promotes Heterotopic Ossification Through Regulation of Endothelial-Mesenchymal Transition in Injured Achilles Tendons in Rats

Although heterotopic ossification (HO) has been reported to be a common complication of the posttraumatic healing process, the underlying mechanism remains unknown. Endothelial-mesenchymal transition (EndMT) is known to play a role in HO, and our recent study observed that neuroendocrine signals can promote HO by modulating EndMT. Melatonin, a neuroendocrine hormone secreted mainly by the pineal gland, has been documented to perform its function in the skeletal system. This study aimed at describing the expression of melatonin during the formation of HO in rat models of Achilles tendon injury and to further investigate its role in regulating EndMT in HO. Histological staining revealed the expression of melatonin throughout the formation of heterotopic bone in injured Achilles tendons, and the serum melatonin levels were increased after the initial injury. Double immunofluorescence showed that the MT2 melatonin receptor was notably expressed at the sites of injury. Micro-CT showed the enhancement of heterotopic bone volume and calcified areas in rats treated with melatonin. Additionally, our data showed that melatonin induced EndMT in primary rat aortic endothelial cells (RAOECs), which acquired traits including migratory function, invasive function and EndMT and MSC marker gene and protein expression. Furthermore, our data exhibited that melatonin promoted the osteogenic differentiation of RAOECs undergoing EndMT in vitro. Importantly, inhibition of the melatonin-MT2 pathway by using the MT2 selective inhibitor 4-P-PDOT inhibited melatonin-induced EndMT and osteogenesis both in vivo and in vitro. In conclusion, these findings demonstrated that melatonin promoted HO through the regulation of EndMT in injured Achilles tendons in rats, and these findings might provide additional directions for the management of HO.

Early diagnosis of heterotopic ossification among patients admitted to a neurological Post-Intensive Care Rehabilitation Unit

BACKGROUND

Heterotopic ossification (HO) is defined as the formation of endochondral bone within soft tissue. Non-genetic forms, mainly corresponding to a consequence of bone, brain or spinal cord injury, are the most common. HO leads to important functional limitations and alteration of quality of life. To our knowledge, the time between brain, bone, or spinal cord injury and clinical suspicion of HO has never been studied. By admitting patients with severe neurological disorders, we hypothesized that the prevalence of HO in neurological post-intensive care rehabilitation units (PICRU) might be significant as these patients have recognized risk factors for HO.

AIM

This study aimed to investigate HO among patients admitted to a neurological PICRU with two objectives: 1) to describe the prevalence of HO in PICRU; 2) to assess the time between neurological disorder, clinical suspicion of HO and radiological diagnosis.

DESIGN

A monocentric retrospective cohort study.

SETTING

PICRU in our public university teaching hospital. This inpatient referral department is specifically dedicated to the early discharge from Intensive Care Units (ICU) of patients with severe neurological impairment who need rehabilitation.

POPULATION

We study all patients admitted between April 2016 and January 2019. One hundred twenty-five subjects were admitted for a rehabilitation program after neuro-trauma or stroke. We included all first-time stays in PICRU lasting 7 days or longer.

METHODS

Retrospective data extraction using administrative data from an electronic patient management program was done to select eligible subjects. Included subjects were then identified by a retrospective review of electronic inpatient medical records after patient discharge. Data of interest were collected from these same medical records.

RESULTS

Forty-four HO were diagnosed in 24 subjects (24/125; 19%), with a median number of 2 [1; 2] HO per subject. Neurological trauma was the main reason for admission to ICU (89/125; 71%) and half of patients had a traumatic brain injury (TBI) (67/125; 54%). The diagnosis of HO was made in PICRU in 75% of cases. Clinical suspicion of HO (autonomic dysfunction, local inflammatory signs, pain, or reduced joint range of motion) was made 6 [5; 7] weeks after admission to ICU. Radiological confirmation of clinical suspicion or fortuitous diagnosis by imaging (50% of the cases) occurred 8 [7; 12] weeks after admission to ICU. The median time of clinical suspicion or radiological diagnosis was 1 week after admission to PICRU.

CONCLUSIONS

HO is a sub-acute complication which develops in patients admitted to ICU for severe central nervous system disorders as clinical suspicion or radiological confirmation of diagnosis was made within the first week after admission in neurological PICRU (i.e. 6 to 8 weeks after ICU admission).

CLINICAL REHABILITATION IMPACT

As treatment for HO may at least partially improves rehabilitation and quality of life, we recommend a systematic screening in PICRU patients for HO by clinical examination supplemented by imaging in case of suspicion.

Genetic and Acquired Heterotopic Ossification: A Translational Tale of Mice and Men

Heterotopic ossification is defined as an aberrant formation of bone in extraskeletal soft tissue, for which both genetic and acquired conditions are known. This pathologic process may occur in many different sites such as the skin, subcutaneous tissue, skeletal muscle and fibrous tissue adjacent to joints, ligaments, walls of blood vessels, mesentery and other. The clinical spectrum of this disorder is wide: lesions may range from small foci of ossification to massive deposits of bone throughout the body, typical of the progressive genetically determined conditions such as fibrodysplasia ossificans progressiva, to mention one of the most severe and disabling forms. The ectopic bone formation may be regarded as a failed tissue repair process in response to a variety of triggers and evolving towards bone formation through a multistage differentiation program, with several steps common to different clinical presentations and distinctive features. In this review, we aim at providing a comprehensive view of the genetic and acquired heterotopic ossification disorders by detailing the clinical and molecular features underlying the different human conditions in comparison with the corresponding, currently available mouse models.

Heterotopic ossification in a patient with paroxysmal sympathetic hyperactivity following multiple trauma complicated with vitamin D deficiency: a case report

Background

Paroxysmal sympathetic hyperactivity (PSH) may occur in patients with traumatic brain injury. Heterotopic ossification (HO) has frequently been observed in patients with PSH and has been found to impair patients’ recoveries. However, the pathophysiology of HO in patients with PSH remains unelucidated. Vitamin D deficiency is a common abnormality among critically ill patients and may be associated not only with musculoskeletal complications, but also with high morbidity and mortality. The association between vitamin D deficiency and HO in patients with PSH has not yet been evaluated.

Case presentation

A 21-year-old man was in a motorcycle accident. The initial diagnosis was diffused axonal injury, thoracic aortic injury, bilateral lung contusion with hemopneumothorax, liver injury, vertebral injury of T5, along with fractures of the right humerus, left patella, bilateral scapula, and a stable pelvic fracture, with an Injury Severity Score of 50. Two weeks after admission, he was diagnosed with PSH. One month after the injury, decreased joint mobility and progressive pain were evident. Computed tomography (CT) showed HO in his humerus, ulna, radius, scapula, ilium, pubis, ischium, knee joint, patella, and tibia, as well as renal calculus. To evaluate metabolic bone abnormalities, we measured levels of 25-OH vitamin D, parathyroid hormone, calcitonin, procollagen type I N-terminal propeptide (a marker of bone formation), and tartrate-resistant acid phosphatase 5b (a marker of bone resorption). This revealed a vitamin D deficiency. Bisphosphonate agents and vitamin D were administered for 1 month. Thereafter, his symptoms, radiographic findings, and laboratory abnormalities improved, and he was transferred to another facility.

Conclusions

HO in patients with PSH, following severe head injury, may be associated with vitamin D deficiency. Medication for vitamin-D-related metabolism abnormalities may represent a novel intervention for HO with PSH.

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.

Role of the HIF‑1α/SDF‑1/CXCR4 signaling axis in accelerated fracture healing after craniocerebral injury

The hypoxic state of the brain tissue surrounding craniocerebral injury induces an increase in the secretion of HIF-1α during the healing process. HIF-1α can promote mesenchymal stem cell (MSC) migration to ischemic and hypoxic sites by regulating the expression levels of molecules such as stromal cell-derived factor-1 (SDF-1) in the microenvironment. Stem cells express the SDF-1 receptor C-X-C chemokine receptor type 4 (CXCR4) and serve a key role in tissue repair, as well as a number of physiological and pathological processes. The present study aimed to determine the role of HIF-1α/SDF-1/CXCR4 signaling in the process of accelerated fracture healing during craniocerebral injury. Cultured MSCs underwent HIF-1α knockdown to elucidate its effect on the proliferative ability of MSCs, and the effect of SDF-1 in MSCs was investigated. It was also determined whether HIF-1α could promote osteogenesis via SDF-1/CXCR4 signaling and recruit MSCs. The results indicated that HIF-1α knockdown suppressed MSC proliferation in vitro, and SDF-1 promoted cell migration via binding to CXCR4. Furthermore, HIF-1α knockdown inhibited MSC migration via SDF-1/CXCR4 signaling. Considering the wide distribution and diversity of roles of SDF-1 and CXCR4, the present results may form a basis for the development of novel strategies for the treatment of craniocerebral injury.

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.

Cambridge experience in spontaneous bone regeneration after traumatic segmental bone defect: a case series and review of literature

High-energy traumatic long bone defects are some of the most challenging to reconstruct. Although cases of spontaneous bone regeneration in these defects have been reported, we are aware of no management guidelines or recommendations for when spontaneous bone regeneration should be considered a viable management option. We aim to identify how certain patient characteristics and surgical factors may help predict spontaneous bone regeneration. A total of 26 cases with traumatic segmental defects were treated at our institution, with eight cases (30.8%) undergoing spontaneous regeneration. We discuss four in detail. Six (75%) reported a degree of periosteal preservation, four (50%) were associated with traumatic brain injury and none were complicated by infection. The average time to spontaneous bone regeneration was 2.06 months. According to our cases, patients with favourable characteristics may benefit from delaying surgical treatment by 6 weeks to monitor for any signs of spontaneous bone formation.

Neurogenic heterotopic ossification in Guillain-Barre syndrome: a rare case report

Neurogenic heterotopic ossification (NHO) is an abnormal development of bone in extra-skeletal tissues, related to neurological disease. NHO is frequently seen after traumatic brain injury or spinal cord injury. NHO may also occur as a rare complication of Guillain Barre Syndrome (GBS). Here, we present a 39 year old man with an acute onset of GBS who developed NHO around both hips two months after the disease onset. Our patient had a history of mechanical ventilation, incomplete tetraplegia and prolonged immobilisation. The pathogenesis of NHO is unclear. Various risk factors have been associated with the development of NHO; prolonged coma, long-term sedation, spasticity, degree of paralysis. NHO is a rare complication of GBS and physicians should be aware that it can develop especially in patients with severe paralysis and in need of mechanical ventilation. Pain and restriction of movements, especially in the hips, should bring NHO to the mind.

Outcomes of Total Hip Arthroplasty in Patients with Osteonecrosis of the Femoral Head Following Surgical Treatment of Brain Tumors

Corticosteroids have been widely used in patients with brain tumors to reduce tumor-associated edema and neurological deficits. This study examined the outcomes of total hip arthroplasty (THA) in patients with osteonecrosis of the femoral head (ONFH) following brain tumor surgery. We identified 34 THAs performed in 26 patients with steroid-induced ONFH among 9254 patients undergoing surgical treatment for primary brain tumors. After propensity score matching with demographics, 68 THAs (52 patients) in ONFH unrelated to brain tumors were selected as the control group. At the time of THA, 54% of brain tumor patients had neurological sequelae and 46% had adrenal insufficiency. After THA, patients with brain tumor required longer hospital stay, reported a lower functional score, and showed a higher rate of heterotopic ossification compared to the control group. However, hip pain score improved significantly after THA in the brain tumor group, and did not differ from that of the control group (P-value = 0.168). Major complication rates were similar (2.9% and 1.5% for the brain tumor and control groups, respectively; P-value = 1.000), and implant survivorships were not different at 7 years (100% and 98.1% for the brain tumor and control groups, respectively; P-value = 0.455). Our findings suggest that THA can be safely performed to reduce hip pain in patients with steroid-induced ONFH after surgical treatment of primary brain tumors.

Investigating the incidence and magnitude of heterotopic ossification with and without joints involvement in patients with a limb fracture and mild traumatic brain injury

Objectives

This study seeks to evaluate the incidence rate of heterotopic ossification (HO) formation in patients afflicted by an isolated limb fracture (ILF) and a concomitant mild traumatic brain injury (mTBI).

Methods

The current study is an observational study including ILF patients with or without a concomitant mTBI recruited from an orthopedic clinic of a Level 1 Trauma Hospital. Patients were diagnosed with a mTBI according to the American Congress of Rehabilitation Medicine (ACRM) criteria. Radiographs taken on average 3 months post-trauma were analyzed separately by two distinct specialists for the presence of HO proximally to the fracture site (joints or extra joints). Both raters referred to Brooker's and Della's Valle's classification to establish signs of HO. First, analyses were conducted for the full sample. Secondly, a matched cohort was used in order to control for specific factors, namely age, sex, type of injury, and time elapsed between the accident and the analyzed radiograph.

Results

The full sample included a total of 183 patients with an ILF (94 females; 47.5 years old), of which 50 had a concomitant mTBI and 133 without. Radiographic evidence of HO was significantly higher in patients with an ILF and a mTBI compared to ILF patients (X² = 6.50; p = 0.01). The matched cohort consisted of 94 participants (i.e.; 47 patients from the ILF + mTBI group and 47 patients from the ILF group). Again, ILF + mTBI patients presented significantly higher rates of HO signs in comparison to ILF patients (X² = 3.69; p = 0.04). Presence of HO was associated with prolonged delays to return to work (RTW) only in ILF + mTBI patients (F = 4.055; p = 0.05) but not in ILF patients (F = 0.823; p = 0.37).

Conclusions

Study findings suggest that rates of HO are significantly higher proximally to fracture sites when ILF patients sustain a concomitant mTBI, even after controlling for factors known to influence HO. Moreover, results show that HO is associated with a prolonged RTW only in ILF patients with a concomitant mTBI but not in ILF-only patients. The impact of mTBI on HO formation warrants further attention to detect early signs of HO, to identify shared physiopathological mechanisms and, ultimately, to design targeted therapies.

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Rates of HO are significantly higher in patients with a fracture and a mTBI compared to patients with a fracture only.

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Factors such as sex, age, joint involvement, and surgical procedures were unrelated to the detection of signs of HO

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Presence of HO negatively impacted RTW delays in patients with a concomitant mTBI

Muscle injury promotes heterotopic ossification by stimulating local bone morphogenetic protein-7 production

Background

Heterotopic ossification (HO) is a pathological condition of abnormal bone formation in soft tissue, which causes pain and restricted range of motion in patients. There are two broad categories of HO, hereditary and acquired. Although different types of HO do not use identical mechanistic pathways of pathogenesis, muscle injury appears to be a unifying feature for all types of HO. However, little is known about the mechanisms by which muscle injury facilitates HO formation.

Objective and method

This study aimed to explore the cellular and molecular mechanisms linking muscle injury to HO by using cardiotoxin to induce muscle injury in a bone morphogenetic protein-2 (BMP-2)-induced HO mouse model.

Results

We found that muscle injury augmented HO formation and that this effect was correlated with BMP signalling activation and upregulation of BMP-7 expression at the early phase of HO progression. We further demonstrated that inhibition of BMP-7 activity in vitro suppressed the osteogenesis-promoting effect of conditioned medium derived from injured muscle tissue and in vivo reduced the volume of HO formation. We also showed that antiinflammatory drug treatment reduced the volume of HO with concomitant reduction in BMP-7 production.

Conclusion

In summary, our study has identified BMP-7 as a key osteoinductive factor in injured muscle that facilitates HO formation.

The translational potential of this article

Our results provide a candidate mechanistic rationale for the use of antiinflammatory drugs in the prevention of HO.

Muscle injury-induced hypoxia alters the proliferation and differentiation potentials of muscle resident stromal cells

Background

Trauma-induced heterotopic ossification (HO) is a complication that develops under three conditions: the presence of an osteogenic progenitor cell, an inducing factor, and a permissive environment. We previously showed that a mouse multipotent Sca1⁺ CD31⁻ Lin⁻ muscle resident stromal cell (mrSC) population is involved in the development of HO in the presence of inducing factors, members of the bone morphogenetic protein family. Interestingly, BMP9 unlike BMP2 causes HO only if the muscle is damaged by injection of cardiotoxin. Because acute trauma often results in blood vessel breakdown, we hypothesized that a hypoxic state in damaged muscles may foster mrSCs activation and proliferation and trigger differentiation toward an osteogenic lineage, thus promoting the development of HO.

Methods

Three- to - six-month-old male C57Bl/6 mice were used to induce muscle damage by injection of cardiotoxin intramuscularly into the tibialis anterior and gastrocnemius muscles. mrSCs were isolated from damaged (hypoxic state) and contralateral healthy muscles and counted, and their osteoblastic differentiation with or without BMP2 and BMP9 was determined by alkaline phosphatase activity measurement. The proliferation and differentiation of mrSCs isolated from healthy muscles was also studied in normoxic incubator and hypoxic conditions. The effect of hypoxia on BMP synthesis and Smad pathway activation was determined by qPCR and/or Western blot analyses. Differences between normally distributed groups were compared using a Student’s paired t test or an unpaired t test.

Results

The hypoxic state of a severely damaged muscle increased the proliferation and osteogenic differentiation of mrSCs. mrSCs isolated from damaged muscles also displayed greater sensitivity to osteogenic signals, especially BMP9, than did mrSCs from a healthy muscle. In hypoxic conditions, mrSCs isolated from a control muscle were more proliferative and were more prone to osteogenic differentiation. Interestingly, Smad1/5/8 activation was detected in hypoxic conditions and was still present after 5 days, while Smad1/5/8 phosphorylation could not be detected after 3 h of normoxic incubator condition. BMP9 mRNA transcripts and protein levels were higher in mrSCs cultured in hypoxic conditions. Our results suggest that low-oxygen levels in damaged muscle influence mrSC behavior by facilitating their differentiation into osteoblasts. This effect may be mediated partly through the activation of the Smad pathway and the expression of osteoinductive growth factors such as BMP9 by mrSCs.

Conclusion

Hypoxia should be considered a key factor in the microenvironment of damaged muscle that triggers HO.

Electronic supplementary material

The online version of this article (10.1186/s13395-019-0202-5) contains supplementary material, which is available to authorized users.

Heterotopic ossification following suboccipital craniectomy decompression surgery for Chiari malformation type I: case report

Suboccipital craniectomy with duraplasty is a commonly performed procedure for children with symptomatic Chiari malformation type I (CM-I). Several dural substitutes are used for duraplasty, ranging from pericranium to synthetic materials. When available, autologous pericranium is often preferred due to its low cost, performance in obtaining a watertight closure, ease of suturing, and absence of immune reaction. Long-term follow-up data on the durability of various dural substitutes are lacking. The authors report a rare, long-term complication of duraplasty performed using an autologous pericranial graft, and they conduct a literature review of similar complications. Heterotopic ossification of an autologous pericranial graft is a rare complication of duraplasty. This dystrophic bone growth can be symptomatic due to compression of neural structures, and it requires reoperation for removal. Surgeons should consider this rare long-term complication in patients presenting with unusual symptoms after duraplasty with pericranium.

Protein biomarkers of epileptogenicity after traumatic brain injury

Traumatic brain injury (TBI) is a major risk factor for acquired epilepsy. Post-traumatic epilepsy (PTE) develops over time in up to 50% of patients with severe TBI. PTE is mostly unresponsive to traditional anti-seizure treatments suggesting distinct, injury-induced pathomechanisms in the development of this condition. Moderate and severe TBIs cause significant tissue damage, bleeding, neuron and glia death, as well as axonal, vascular, and metabolic abnormalities. These changes trigger a complex biological response aimed at curtailing the physical damage and restoring homeostasis and functionality. Although a positive correlation exists between the type and severity of TBI and PTE, there is only an incomplete understanding of the time-dependent sequelae of TBI pathobiologies and their role in epileptogenesis. Determining the temporal profile of protein biomarkers in the blood (serum or plasma) and cerebrospinal fluid (CSF) can help to identify pathobiologies underlying the development of PTE, high-risk individuals, and disease modifying therapies. Here we review the pathobiological sequelae of TBI in the context of blood- and CSF-based protein biomarkers, their potential role in epileptogenesis, and discuss future directions aimed at improving the diagnosis and treatment of PTE.