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

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.

Bacterial Lipopolysaccharides Exacerbate Neurogenic Heterotopic Ossification Development

Neurogenic heterotopic ossifications (NHO) are heterotopic bones that develop in periarticular muscles after severe central nervous system (CNS) injuries. Several retrospective studies have shown that NHO prevalence is higher in patients who suffer concomitant infections. However, it is unclear whether these infections directly contribute to NHO development or reflect the immunodepression observed in patients with CNS injury. Using our mouse model of NHO induced by spinal cord injury (SCI) between vertebrae T11 to T13 , we demonstrate that lipopolysaccharides (LPS) from gram-negative bacteria exacerbate NHO development in a toll-like receptor-4 (TLR4)-dependent manner, signaling through the TIR-domain-containing adapter-inducing interferon-β (TRIF/TICAM1) adaptor rather than the myeloid differentiation primary response-88 (MYD88) adaptor. We find that T11 to T13 SCI did not significantly alter intestinal integrity nor cause intestinal bacteria translocation or endotoxemia, suggesting that NHO development is not driven by endotoxins from the gut in this model of SCI-induced NHO. Relevant to the human pathology, LPS increased expression of osteoblast markers in cultures of human fibro-adipogenic progenitors isolated from muscles surrounding NHO biopsies. In a case-control retrospective study in patients with traumatic brain injuries, infections with gram-negative Pseudomonas species were significantly associated with NHO development. Together these data suggest a functional association between gram-negative bacterial infections and NHO development and highlights infection management as a key consideration to avoid NHO development in patients. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

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.

Neurogenic Heterotopic Ossifications Recapitulate Hematopoietic Stem Cell Niche Development Within an Adult Osteogenic Muscle Environment

Hematopoiesis and bone interact in various developmental and pathological processes. Neurogenic heterotopic ossifications (NHO) are the formation of ectopic hematopoietic bones in peri-articular muscles that develop following severe lesions of the central nervous system such as traumatic cerebral or spinal injuries or strokes. This review will focus on the hematopoietic facet of NHO. The characterization of NHO demonstrates the presence of hematopoietic marrow in which quiescent hematopoietic stem cells (HSC) are maintained by a functional stromal microenvironment, thus documenting that NHOs are neo-formed ectopic HSC niches. Similarly to adult bone marrow, the NHO permissive environment supports HSC maintenance, proliferation and differentiation through bidirectional signaling with mesenchymal stromal cells and endothelial cells, involving cell adhesion molecules, membrane-bound growth factors, hormones, and secreted matrix proteins. The participation of the nervous system, macrophages and inflammatory cytokines including oncostatin M and transforming growth factor (TGF)-β in this process, reveals how neural circuitry fine-tunes the inflammatory response to generate hematopoietic bones in injured muscles. The localization of NHOs in the peri-articular muscle environment also suggests a role of muscle mesenchymal cells and bone metabolism in development of hematopoiesis in adults. Little is known about the establishment of bone marrow niches and the regulation of HSC cycling during fetal development. Similarities between NHO and development of fetal bones make NHOs an interesting model to study the establishment of bone marrow hematopoiesis during development. Conversely, identification of stage-specific factors that specify HSC developmental state during fetal bone development will give more mechanistic insights into NHO.

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.

Neurological heterotopic ossification: novel mechanisms, prognostic biomarkers and prophylactic therapies

Neurological heterotopic ossification (NHO) is a debilitating condition where bone forms in soft tissue, such as muscle surrounding the hip and knee, following an injury to the brain or spinal cord. This abnormal formation of bone can result in nerve impingement, pain, contractures and impaired movement. Patients are often diagnosed with NHO after the bone tissue has completely mineralised, leaving invasive surgical resection the only remaining treatment option. Surgical resection of NHO creates potential for added complications, particularly in patients with concomitant injury to the central nervous system (CNS). Although recent work has begun to shed light on the physiological mechanisms involved in NHO, there remains a significant knowledge gap related to the prognostic biomarkers and prophylactic treatments which are necessary to prevent NHO and optimise patient outcomes. This article reviews the current understanding pertaining to NHO epidemiology, pathobiology, biomarkers and treatment options. In particular, we focus on how concomitant CNS injury may drive ectopic bone formation and discuss considerations for treating polytrauma patients with NHO. We conclude that understanding of the pathogenesis of NHO is rapidly advancing, and as such, there is the strong potential for future research to unearth methods capable of identifying patients likely to develop NHO, and targeted treatments to prevent its manifestation.

When the Nervous System Turns Skeletal Muscles into Bones: How to Solve the Conundrum of Neurogenic Heterotopic Ossification

PURPOSE OF REVIEW

Neurogenic heterotopic ossification (NHO) is the abnormal formation of extra-skeletal bones in periarticular muscles after damage to the central nervous system (CNS) such as spinal cord injury (SCI), traumatic brain injury (TBI), stroke, or cerebral anoxia. The purpose of this review is to summarize recent developments in the understanding of NHO pathophysiology and pathogenesis. Recent animal models of NHO and recent findings investigating the communication between CNS injury, tissue inflammation, and upcoming NHO therapeutics are discussed.

RECENT FINDINGS

Animal models of NHO following TBI or SCI have shown that NHO requires the combined effects of a severe CNS injury and soft tissue damage, in particular muscular inflammation and the infiltration of macrophages into damaged muscles plays a key role. In the context of a CNS injury, the inflammatory response to soft tissue damage is exaggerated and persistent with excessive signaling via substance P-, oncostatin M-, and TGF-β1-mediated pathways. This review provides an overview of the known animal models and mechanisms of NHO and current therapeutic interventions for NHO patients. While some of the inflammatory mechanisms leading to NHO are common with other forms of traumatic and genetic heterotopic ossifications (HO), NHOs uniquely involve systemic changes in response to CNS injury. Future research into these CNS-mediated mechanisms is likely to reveal new targetable pathways to prevent NHO development in patients.

Pain with traumatic brain injury and psychological disorders

Traumatic brain injury (TBI) is the cause for long-term disability in more than 3 million patients in the US alone, with chronic pain being the most frequently reported complain. To date, predisposing mechanisms for chronic pain in TBI patients are largely unknown. Psychological disorders, including post-traumatic stress disorder, depression and anxiety following TBI are commonly reported comorbidities to post-traumatic pain. Long term consequences can be debilitating and affect quality of life even when the injury is mild. In this review, we present the most commonly reported chronic pain conditions across the spectrum of severity of TBI, mainly focusing on mild TBI. We discuss chronic post- traumatic headaches, widespread pain as well as post-traumatic central pain. We discuss pain in the context of injury severity and military versus civilian populations. We are only starting to understand the biological mechanisms behind post-traumatic pain and associated psychological distress following TBI, with genetic, biochemical and imaging studies pointing to the dopaminergic, neurotrophic factors and the role of Apolipoprotein. Physiological and neurological mechanisms are proposed to partially explain this interaction between post-traumatic pain and psychological distress. Nevertheless, the evidence for the role of structural brain damage remains incomplete and to a large extent debatable, as it is still difficult to establish clear causality between brain trauma and chronic pain. Finally, general aspects of management of chronic pain post-TBI are addressed.

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.

Occurrence and predictive factors of heterotopic ossification in severe acquired brain injured patients during rehabilitation stay: cross-sectional survey

OBJECTIVES

To report occurrence and identify patient's features and risk factors of heterotopic ossifications in patients with severe acquired brain injury in intensive rehabilitation centres.

DESIGN

Multicentre cross-sectional survey.

SETTING

A total of 48 severe acquired brain injury rehabilitation institutes.

PARTICIPANTS

Traumatic and non-traumatic severe brain-injured patients ( N = 689) in rehabilitation centres on 28 May 2016.

MAIN OUTCOME MEASURE

Occurrence of heterotopic ossifications diagnosed by standard radiological and/or sonographic evaluation on the basis of clinical suspicion.

RESULTS

Heterotopic ossification occurred around one or more joints in 94/689 patients (13.6%) with a significantly higher prevalence in young males. Occurrence did not significantly differ in relation to aetiology (16.3% traumatic, 19.2% anoxic, 11.7% vascular and 11.5% other). Prevalence was significantly higher in patients with diffuse (23.3%) rather than focal brain lesions (12.4%) or unspecified lesions (11.2%; chi-square = 7.81, df = 2, P = 0.020); longer duration of coma ( P = 0.0016) and ventilation support ( P = 0.0145); paroxysmal sympathetic hyperactivity (22.6% versus 11.6%; chi-square = 10.81, df = 1, P = 0.001); and spasticity (22.7% versus 10.1%; chi-square = 18.63, df = 1, P < 0.0001). A longer interval between acute brain injury and admission to rehabilitation centre was significantly associated with higher frequency of heterotopic ossifications.

CONCLUSION

Occurrence of heterotopic ossifications is frequent in patients with severe traumatic and non-traumatic brain-injury in rehabilitation centres. Our study confirms male gender, young age, paroxysmal sympathetic hyperactivity, spasticity, longer duration of coma and ventilation and longer interval between brain injury onset and admission to rehabilitation centre as possible risk factors. Further studies are necessary to investigate the role of early appropriate rehabilitation pathways to reduce occurrence of heterotopic ossifications.

A preliminary investigation on the effect of extracorporeal shock wave therapy as a treatment for neurogenic heterotopic ossification following traumatic brain injury. Part I: Effects on pain

INTRODUCTION

Neurogenic heterotopic ossification (NHO) is a complication of a neurological injury following traumatic brain injury (TBI) and may be present around major synovial joints. It is often accompanied by severe pain, which may lead to limitation in activities of daily living. Currently, a common intervention for NHO is surgery, which has been reported to carry many additional risks. This study was designed to assess the effect of extracorporeal shock wave therapy (ESWT) on pain in patients with TBI with chronic NHO.

METHODS

A series of single-case studies (n = 11) was undertaken with patients who had TBI and chronic NHO at the hip or knee. Each patient received four applications of high-energy EWST delivered to the affected joint over 8 weeks. Two-weekly follow-up assessments were carried out, and final assessments were made 3 and 6 months post-intervention. Pain was measured using the Faces Rating Scale, and X-rays were taken at baseline and 6-months post-intervention to physiologically measure the size of the NHO.

RESULTS

The application of high-energy ESWT was associated with significant overall reduction of pain in patients with TBI and NHO (Tau-0.412, 95% confidence interval -0.672 to -0.159, p = 0.002).

CONCLUSIONS

ESWT is a novel non-invasive intervention for reducing pain resulting from NHO in patients with TBI.

A preliminary investigation on the effect of extracorporeal shock wave therapy as a treatment for neurogenic heterotopic ossification following traumatic brain injury. Part II: Effects on function

INTRODUCTION

Neurogenic heterotopic ossification (NHO) occurs as a complication of traumatic brain injury (TBI). Management of clinically significant NHO remains variable. Complications of mature NHO include limitation of mobility. The effect of the extracorporeal shock wave therapy (ESWT) on range of motion at hip and knee, and function in patients with TBI with chronic NHO was investigated.

METHODS

A series of single-case studies applying ESWT to chronic NHO at the hip or knee of 11 patients with TBI were undertaken at a rehabilitation hospital. Participants received four applications of high-energy EWST delivered to the affected hip or knee over a period of 8 weeks. Two-weekly follow- up assessments were carried out; final assessments were made 3 and 6 months post-intervention. Range of motion (ROM) and Functional Reach (FR) or Modified Functional Reach (MFR) were measured.

RESULTS

Application of high-energy ESWT was associated with significant improvement in ROM (flexion) of the NHO-affected knee (Tau = 0.833, 95% CI 0.391-1.276, p = 0.002) and significant improvement of FR (Overall Tau 0.486, 95% CI 0.141-0.832, p = 0.006); no significant improvement in hip ROM or MFR.

CONCLUSIONS

ESWT may improve mobility and balance of patients with TBI who have chronic NHO.

Improvements in elbow motion after resection of heterotopic bone: a systematic review

Complex elbow trauma, severe burn, or a closed head injury render patients at risk for developing heterotopic ossification around the elbow. When heterotopic ossification restricts elbow motion, some patients request surgical resection. We performed a systematic review of the literature to analyze improvement in elbow motion after resection of heterotopic ossification around the elbow. We found that, on average, etiology had little impact on outcome after resection of heterotopic ossification. Resection of heterotopic bone generally leads to improvement of elbow function.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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