Heterotopic Ossification: A Review of Current Understanding, Treatment, and Future

A case report of heterotopic ossifications in abdominal incision scar

INTRODUCTION

Heterotopic ossification (HO) develops when bone formation appears in soft tissues, usually after an injury or major surgery. Timely and accurately diagnosing of this rare event is essential due to the possibility of misdiagnosis as a maintained foreign body, infection, incisional neoplastic recurrence, and metastatic or primary neoplasms.

CASE PRESENTATION

In this study, we present a 57-year-old man who was operated for peritonitis due to perforated appendicitis, and an asymptomatic HO was accidentally found on an incisional line of previous open prostatectomy about 5 years earlier due to benign prostatic hyperplasia. A bone density lesion was seen in the fascia and on the incisional scar of previous surgery.

DISCUSSION

HO rarely occurs within an abdominal incision due to surgery. It is reported only within vertical midline incisions and mainly within the first year after the operation. Imaging confirms the diagnosis of HO in previous abdominal surgery scars, which reveals dense vertical calcification along the previous incisional scar. In the case of HO, the exclusive effective management is the entire surgical excision with primary closure, and NSAIDs are the preventive choices.

CONCLUSION

HO should be considered in patients presenting with discomfort or palpable mass or even asymptomatic patients with previous abdominal surgeries besides considering relative history such as surgical complications or neoplasms.

Post-laparotomy heterotopic ossification of the xiphoid process: A case report

BACKGROUND

Heterotopic ossification (HO) represents all types of extraskeletal ossification in the body. It occurs in various areas, including the skin, subcutaneous tissue, muscle, and joints. Surgical excision is recommended for symptomatic HO. Postoperative radiotherapy, oral nonsteroidal anti-inflammatory drugs, and topical sealants, such as bone wax, have been recommended as preventive measures. As HO is rare in occurrence, these recommendations are based on personal experiences, and there is a lack of information on individualized treatments depending on its location.

CASE SUMMARY

A 62-year-old male was admitted for symptomatic HO along a laparotomy scar. Surgical excision was performed for an 11 cm-sized ossification originating from the xiphoid process, and bone wax was applied to the excisional margin. However, the surgical wound failed to heal. After several weeks of saline-soaked gauze dressing, delayed wound closure was performed. The patient was finally discharged eight weeks after the excision. Because HO can occur in various areas of the body, a treatment strategy that may be effective for some may not be for others. Bone wax has been used as a topical sealant over excisional margins in the shoulder, elbow, and temporomandibular joints. However, in our case, its application on an abdominal surgical wound delayed its primary healing intention. The valuable lesson was that, when choosing a treatment method for HO based on available research data, its location must be considered.

CONCLUSION

Complete excision should be the priority treatment option for symptomatic HO along the laparotomy scar. Bone wax application is not recommended.

The genetic background determines material-induced bone formation through the macrophage-osteoclast axis

Osteoinductive materials are characterized by their ability to induce bone formation in ectopic sites. Thus, osteoinductive materials hold promising potential for repairing bone defects. However, the mechanism of material-induced bone formation remains unknown, which limits the design of highly potent osteoinductive materials. Here, we demonstrated a genetic background link among macrophage polarization, osteoclastogenesis and material-induced bone formation. The intramuscular implantation of an osteoinductive material in FVB/NCrl (FVB) mice resulted in more M2 macrophages at week 1, more osteoclasts at week 2 and increased bone formation after week 4 compared with the results obtained in C57BL/6JOlaHsd (C57) mice. Similarly, in vitro, with a greater potential to form M2 macrophages, monocytes derived from FVB mice formed more osteoclasts than those derived from C57 mice. A transcriptomic analysis identified Csf1, Cxcr4 and Tgfbr2 as the main genes controlling macrophage-osteoclast coupling, which were further confirmed by related inhibitors. With such coupling, macrophage polarization and osteoclast formation of monocytes in vitro successfully predicted in vivo bone formation in four other mouse strains. Considering material-induced bone formation as an example of acquired heterotopic bone formation, the current findings shed a light on precision medicine for both bone regeneration and the treatment of pathological heterotopic bone formation.

Post-traumatic heterotopic ossification in front of the ankle joint for 23 years: A case report and review of literature

BACKGROUND

Heterotopic ossification (HO) refers to the formation of new bone in non-skeletal tissues such as muscles, tendons or other soft tissues. Severe muscle and soft tissue injury often lead to the formation of HO. However, anterior HO of the ankle is rarely reported.

CASE SUMMARY

We report a patient with massive HO in front of the ankle joint for 23 years. In 1998, the patient was injured by a falling object on the right lower extremity, which gradually formed a massive heterotopic bone change in the right calf and dorsum of the foot. The patient did not develop gradual ankle function limitations until nearly 36 mo ago, and underwent resection of HO. Even after 23 years and resection of HO, the ankle joint was still able to move.

CONCLUSION

It is recommended that the orthopedist should be aware of HO and distinguish it from bone tumor.

Management of conflict injuries to the upper limb. Part 2: reconstruction and managing complications

This is the second of a two-part review article on the management of conflict injuries, focused on the reconstructive strategies for bone, nerve and soft tissue and to provide guidance on assessing and managing common complications associated with complex upper limb injuries. Following assessment and early surgical management, the conflict casualty will require further wound evaluation and planning prior to definitive reconstruction of limb injuries. Surgical management of the upper limb injury should aim, where possible, to preserve the limb and allow functional reconstruction. The principles of the second look procedure are to assess wound progression, further reduce the risk of infection and plan definitive reconstruction with adequate soft tissue cover. The prerequisites for successful surgical reconstruction are a stable patient, combined orthoplastic surgery expertise supported by physiotherapists and hand therapists.

Treatment of Temporomandibular Joint Heterotopic Ossificans: A Novel Protocol With Multimodal Therapy Based on Literature Review and Presentation of a Unique Case Reportc

PURPOSE

The purpose of this study was to create a treatment protocol for cases of heterotopic ossification (HO) of the temporomandibular joint (TMJ), particularly those refractory to current TMJ HO protocols. In addition, we demonstrate the success of this protocol on a unique case of recurrent HO that failed multiple TMJ HO protocols in the setting of an improvised explosive device (IED) blast in a wounded warrior.

METHODS

An electronic literature review was conducted via PubMed and Web of Science. Twenty-five studies were identified to provide supporting evidence for a proposed, up-to-date protocol for the treatment of refractory TMJ HO. The authors present a case report of a wounded warrior with HO ankylosis of bilateral TMJs in the setting of IED blast and demonstrate successful use of our surgical and pharmacotherapeutic protocol.

RESULTS

Based on the literature review, our proposed protocol consists of pharmacotherapy with celecoxib and etidronate, with weekly forced dilation (brisement) and home physical therapy with the TheraBite Jaw Motion Rehab System. Surgically, the TMJ should be treated with two-stage reconstruction using initial polymethyl methacrylate spacers and subsequent total joint reconstruction with custom prostheses, fat grafting, and 3-dimensional-navigated total resection of HO. This protocol was successfully utilized in our patient's refractory HO ankylosed TMJ secondary to IED blast, and the patient's maximal incisal opening was regained and has remained stable 2 years after surgery without recurrent HO.

CONCLUSIONS

Our method for treatment in this case deviated from the standard TMJ Concepts HO protocol in that it included multimodal pharmacotherapy with celecoxib and etidronate. Based on our literature review and experience, we advise that clinicians utilize our protocol for the management of all craniofacial HO cases, particularly in cases of recurrent HO that fail conventional therapies and/or involving high-order blast trauma.

Engineered osteoclasts as living treatment materials for heterotopic ossification therapy

Osteoclasts (OCs), the only cells capable of remodeling bone, can demineralize calcium minerals biologically. Naive OCs have limitations for the removal of ectopic calcification, such as in heterotopic ossification (HO), due to their restricted activity, migration and poor adhesion to sites of ectopic calcification. HO is the formation of pathological mature bone within extraskeletal soft tissues, and there are currently no reliable methods for removing these unexpected calcified plaques. In the present study, we develop a chemical approach to modify OCs with tetracycline (TC) to produce engineered OCs (TC-OCs) with an enhanced capacity for targeting and adhering to ectopic calcified tissue due to a broad affinity for calcium minerals. Unlike naive OCs, TC-OCs are able to effectively remove HO both in vitro and in vivo. This achievement indicates that HO can be reversed using modified OCs and holds promise for engineering cells as "living treatment agents" for cell therapy.

Heterotopic ossification in mice overexpressing Bmp2 in Tie2+ lineages

Bone morphogenetic protein (Bmp) signaling is critical for organismal development and homeostasis. To elucidate Bmp2 function in the vascular/hematopoietic lineages we generated a new transgenic mouse line in which ectopic Bmp2 expression is controlled by the Tie2 promoter. Tie2CRE/+;Bmp2tg/tg mice develop aortic valve dysfunction postnatally, accompanied by pre-calcific lesion formation in valve leaflets. Remarkably, Tie2CRE/+;Bmp2tg/tg mice develop extensive soft tissue bone formation typical of acquired forms of heterotopic ossification (HO) and genetic bone disorders, such as Fibrodysplasia Ossificans Progressiva (FOP). Ectopic ossification in Tie2CRE/+;Bmp2tg/tg transgenic animals is accompanied by increased bone marrow hematopoietic, fibroblast and osteoblast precursors and circulating pro-inflammatory cells. Transplanting wild-type bone marrow hematopoietic stem cells into lethally irradiated Tie2CRE/+;Bmp2tg/tg mice significantly delays HO onset but does not prevent it. Moreover, transplanting Bmp2-transgenic bone marrow into wild-type recipients does not result in HO, but hematopoietic progenitors contribute to inflammation and ectopic bone marrow colonization rather than to endochondral ossification. Conversely, aberrant Bmp2 signaling activity is associated with fibroblast accumulation, skeletal muscle fiber damage, and expansion of a Tie2+ fibro-adipogenic precursor cell population, suggesting that ectopic bone derives from a skeletal muscle resident osteoprogenitor cell origin. Thus, Tie2CRE/+;Bmp2tg/tg mice recapitulate HO pathophysiology, and might represent a useful model to investigate therapies seeking to mitigate disorders associated with aberrant extra-skeletal bone formation.

Inhibition of IL-17 prevents the progression of traumatic heterotopic ossification

Traumatic heterotopic ossification (HO) is the abnormal formation of bone in soft tissues as a consequence of injury. However, the pathological mechanisms leading to traumatic HO remain unknown. Here, we report that aberrant expression of IL-17 promotes traumatic HO formation by activating β-catenin signalling in mouse model. We found that elevated IL-17 and β-catenin levels are correlated with a high degree of HO formation in specimens from patients and HO animals. We also show that IL-17 initiates and promotes HO progression in mice. Local injection of an IL-17 neutralizing antibody attenuates ectopic bone formation in a traumatic mouse model. IL-17 enhances the osteoblastic differentiation of mesenchymal stem cells (MSCs) by activating β-catenin signalling. Moreover, inhibition of IL-17R or β-catenin signalling by neutralizing antibodies or drugs prevents the osteogenic differentiation of isolated MSCs and decreases HO formation in mouse models. Together, our study identifies a novel role for active IL-17 as the inducer and promoter of ectopic bone formation and suggests that IL-17 inhibition might be a potential therapeutic target in traumatic HO.

Telerehabilitation for Amputee Care

Patients with amputation have unique characteristics and needs that must be considered when services are being provided through a virtual platform. The types of amputation rehabilitation services that can be provided virtually are numerous and vary from a full clinical team evaluation to individual therapy services. Whether services are being provided in person or through a virtual platform, rehabilitation of the person with amputation ideally involves a collaborative interdisciplinary team. The potential benefits of providing amputation rehabilitation care through a virtual platform include enhanced access to specialized services, reduced travel burden, and improved continuity of care.

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.

Murine Tissue-Resident PDGFRα+ Fibro-Adipogenic Progenitors Spontaneously Acquire Osteogenic Phenotype in an Altered Inflammatory Environment

Acquired heterotopic ossifications (HO) arising as a result of various traumas, including injury or surgical interventions, often result in pain and loss of motion. Though triggers for HO have been identified, the cellular source of these heterotopic lesions as well as the underlying mechanisms that drive the formation of acquired HO remain poorly understood, and treatment options, including preventative treatments, remain limited. Here, we explore the cellular source of HO and a possible underlying mechanism for their spontaneous osteogenic differentiation. We demonstrate that HO lesions arise from tissue-resident PDGFRα+ fibro/adipogenic progenitors (FAPs) in skeletal muscle and not from circulating bone marrow-derived progenitors. Further, we show that accumulation of these cells in the tissue after damage due to alterations in the inflammatory environment can result in activation of their inherent osteogenic potential. This work suggests a mechanism by which an altered inflammatory cell and FAP interactions can lead to the formation of HO after injury and presents potential targets for therapeutics in acquired HO. © 2020 American Society for Bone and Mineral Research.

Local injection of a hexametaphosphate formulation reduces heterotopic ossification in vivo

Heterotopic ossification (HO), the pathological formation of ectopic bone, is a debilitating condition which can cause chronic pain, limit joint movement, and prevent prosthetic limb fitting. The prevalence of this condition has risen in the military population, due to increased survivorship following blast injuries. Current prophylaxes, which aim to target the complex upstream biological pathways, are inconsistently effective ​and have a range of side-effects that make them unsuitable for combat-injured personnel. As such, many patients must undergo further surgery to remove the formed ectopic bone. In this study, a non-toxic, U.S. Food and Drug Administration (FDA) -approved calcium chelator, hexametaphosphate (HMP), is explored as a novel treatment paradigm for this condition, which targets the chemical, rather that biological, ​bone formation pathways. This approach allows not only prevention of pathological bone formation ​but also uniquely facilitates reversal, which current drugs cannot achieve. Targeted, minimally invasive delivery is achieved by loading HMP into an injectable colloidal alginate. These formulations significantly reduce ​the length of the ectopic bone formed in a rodent model of HO, with no effect on the adjacent skeletal bone. This study demonstrates the potential of localized dissolution as a new treatment ​and an alternative to surgery ​for pathological ossification and calcification conditions.

Three-year follow-up of changes of cortical bone thickness after implantation of Endo-Exo-Prosthesis (EEP) for transfemoral amputees

Introduction

Transcutaneous Osseointegrated Prosthetic Systems (TOPS) offer a good alternative for patients who cannot be satisfactorily rehabilitated by conventional suspension sockets. The Endo-Exo-Prothesis (EEP, ESKA Orthopaedic Handels GmbH®, Deutschland) is the most implanted TOPS in Germany. Previous studies have shown that cortical thickness increases after implantation of TOPS. The aim of this study is to determine changes of cortical thickness in relation to the time after implantation of the Endo-Fix-Stem.

Patients and methods

All transfemoral amputees treated by EEP from 2007 to 2013 were operated by the last author of this study. X-ray images of 4 follow-up intervals (postoperative, 3 months, 12 months, 3 years) were analyzed retrospectively. The femoral residuum was divided into 3 sections (proximal, middle, distal) with 2 measuring points in each section: medial and lateral. Cortical thickness was measured at these 6 points and compared at regular intervals using the Friedman test for non-parametric dependent variables.

Results

Thirty-seven patients with 40 implants were included. The average age was 52.2 years (30–79 years). 83.7% of the patients were male. No statistical significance could be shown for any of the measuring points of the femoral residual (proximal medial, proximal lateral, middle medial, middle lateral, distal medial, distal lateral) among the mean values of the cortical thickness at the different follow-up times (p > 0.05 for all measuring points). Cortical remodeling processes (> 1 millimeter (mm)) occurred in all implants despite a missing statistical significance. Hypertrophy could be confirmed for 42.5% and atrophy for 37.5%. Twenty percent of the cases showed a parallel occurrence of both entities. Cortical changes greater than 5 mm were only observed at the distal end of the femur.

Conclusion

Even if our results did not show any significant difference, it can be deduced that the osseointegration process leads to a remodeling of the bone structure, both in terms of increased bone formation and bone resorption. However, it has not yet been conclusively clarified which processes lead to hyper- or atrophy. The force transmission between prosthesis and bone and the facultative bacterial colonization of the stoma are still the main factors which may be responsible for the bone remodeling processes.

Surgical Management of Shoulder Heterotopic Ossification

The formation of heterotopic ossification around the shoulder is a rare but potentially debilitating condition. It is found most commonly around the hip and is usually associated with an inciting event such as trauma, burn, previous surgery, or traumatic brain/spinal cord injury. The formation of shoulder heterotopic ossification following arthroscopic surgery is very uncommon, with few data pertaining to it in the current literature. Formation of heterotopic ossification in the shoulder after arthroscopic surgery typically occurs around the acromioclavicular joint and in the subacromial space. This location may lead to chronic pain and decreased mobility. The purpose of this article is to describe an arthroscopic technique for excision of heterotopic ossification.

Targeting heterotopic ossification by inhibiting activin receptor‑like kinase 2 function (Review)

Heterotopic ossification (HO) refers to the appearance of osteoblasts in soft tissues under pathological conditions, such as trauma or infection. HO arises in an unpredictable way without any recognizable initiation. Activin receptor-like kinase-2 (ALK2) is a type I cell surface receptor for bone morphogenetic proteins (BMPs). The dysregulation of ALK2 signaling is associated with a variety of diseases, including cancer and HO. At present, the prevention and treatment of HO in the clinic predominantly includes nonsteroidal anti-inflammatory drugs (NSAIDs), bisphosphonates and other drug treatments, low-dose local radiation therapy and surgical resection, rehabilitation treatment and physical therapy. However, most of these therapies have adverse effects. These methods do not prevent the occurrence of HO. The pathogenesis of HO is not being specifically targeted; the current treatment strategies target the symptoms, not the disease. These treatments also cannot solve the fundamental problem of the occurrence of HO. Therefore, scholars have been working to develop targeted therapies based on the pathogenesis of HO. The present review focuses on advances in the understanding of the underlying mechanisms of HO, and possible options for the prevention and treatment of HO. In addition, the role of ALK2 in the process of HO is introduced and the progress made towards the targeted inhibition of ALK2 is discussed. The present study aims to offer a platform for further research on possible targets for the prevention and treatment of HO.

Failure of Indomethacin and Radiation to Prevent Blast-induced Heterotopic Ossification in a Sprague-Dawley Rat Model

BACKGROUND

Although use of nonsteroidal antiinflammatory drugs and low-dose irradiation has demonstrated efficacy in preventing heterotopic ossification (HO) after THA and surgical treatment of acetabular fractures, these modalities have not been assessed after traumatic blast amputations where HO is a common complication that can arise in the residual limb.

QUESTIONS/PURPOSES

The purpose of this study was to investigate the effectiveness of indomethacin and irradiation in preventing HO induced by high-energy blast trauma in a rat model.

METHODS

Thirty-six Sprague-Dawley rats underwent hind limb blast amputation with a submerged explosive under water followed by irrigation and primary wound closure. One group (n = 12) received oral indomethacin for 10 days starting on postoperative Day 1. Another group (n = 12) received a single dose of 8 Gy irradiation to the residual limb on postoperative Day 3. A control group (n = 12) did not receive either. Wound healing and clinical course were monitored in all animals until euthanasia at 24 weeks. Serial radiographs were taken immediately postoperatively, at 10 days, and every 4 weeks thereafter to monitor the time course of ectopic bone formation until euthanasia. Five independent graders evaluated the 24-week radiographs to quantitatively assess severity and qualitatively assess the pattern of HO using a modified Potter scale from 0 to 3. Assessment of grading reproducibility yielded a Fleiss statistic of 0.41 and 0.37 for severity and type, respectively. By extrapolation from human clinical trials, a minimum clinically important difference in HO severity was empirically determined to be two full grades or progression of absolute grade to the most severe.

RESULTS

We found no differences in mean HO severity scores among the three study groups (indomethacin 0.90 ± 0.46 [95% confidence interval {CI}, 0.60-1.19]; radiation 1.34 ± 0.59 [95% CI, 0.95-1.74]; control 0.95 ± 0.55 [95% CI, 0.60-1.30]; p = 0.100). For qualitative HO type scores, the radiation group had a higher HO type than both indomethacin and controls, but indomethacin was no different than controls (indomethacin 1.08 ± 0.66 [95% CI, 0.67-1.50]; radiation 1.89 ± 0.76 [95% CI, 1.38-2.40]; control 1.10 ± 0.62 [95% CI, 0.70-1.50]; p = 0.013). The lower bound of the 95% CI on mean severity in the indomethacin group and the upper bound of the radiation group barely spanned a full grade and involved only numeric grades < 2, suggesting that even if a small difference in severity could be detected, it would be less than our a priori-defined minimum clinically important difference and any differences that might be present are unlikely to be clinically meaningful.

CONCLUSIONS

This work unexpectedly demonstrated that, compared with controls, indomethacin and irradiation provide no effective prophylaxis against HO in the residual limb after high-energy blast amputation in a rat model. Such an observation is contrary to the civilian experience and may be potentially explained by either a different pathogenesis for blast-induced HO or a stimulus that overwhelms conventional regimens used to prevent HO in the civilian population.

CLINICAL RELEVANCE

HO in the residual limb after high-energy traumatic blast amputation will likely require novel approaches for prevention and management.

Heterotopic Ossification in Mouse Models of Fibrodysplasia Ossificans Progressiva

Fibrodysplasia ossificans progressiva (FOP), a rare genetic disorder of progressive extra-skeletal ossification, is the most disabling form of heterotopic ossification (HO) in humans. Most people with FOP carry an activating mutation in a BMP type I receptor gene, ACVR1 ^R206H, that promotes ectopic chondrogenesis and osteogenesis and in turn HO. Advances in elucidating the cellular and molecular events and mechanisms that lead to the ectopic bone formation are being made through the use of genetically engineered mouse models that recapitulate the human disease. We describe methods for inducing heterotopic ossification in a mouse model that conditionally expresses the Acvr1 ^R206H allele.

Health needs of ex-military personnel in the UK: a systematic review and qualitative synthesis

Background

Despite all local authorities in England signing up to the Armed Forces Covenant, only a small proportion of Joint Strategic Needs Assessments (JSNAs) include detailed consideration of the health of the local ex-military population. This article supports improvements to JSNAs by systematically reviewing published research for evidence of differences in health between the ex-military population and the general public.

Methods

Systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses methodology for qualitative synthesis of mixed study designs. SCOPUS, PubMed and Google Scholar were searched for published research on health outcomes among UK ex-military populations. All study designs were included.

Results

43 studies met the inclusion criteria. Rates of mental illness and hearing loss are higher among ex-military populations compared with the general public, while rates of cancer among ex-military personnel born after 1960 are lower. Despite high rates of hazardous drinking among serving personnel, rates of alcohol-related harm among ex-military populations are no higher than the general public. There is a subpopulation at increased risk of a range of adverse outcomes. This group is variously identified as younger, male, less educated, more likely to have served in a combat role and/or left service early.

Conclusions

This review found evidence of areas of increased and reduced disease burden among ex-military populations. More detailed information on the make-up of the local ex-service population would support more meaningful needs assessments. The Ministry of Defence and local authorities and service providers should work together to support early identification and targeted support for those at the highest risk of adverse outcomes.

Massive heterotopic ossification after distal femur fracture

Introduction Heterotopic ossification is the formation of lamellar bone in periarticular soft tissue that can be seen in paralysed patients or following trauma. It can cause significant burden to already debilitated patients. Case presentation A 12-year-old boy with paraplegia due to neuromyelitis optica presented with progressive right knee pain and swelling. There was no history of trauma to the knee. Anteroposterior radiograph of femur at the initial presentation showed a supracondylar femur fracture for which casting was performed. Six weeks later, when casting was removed, swelling along with increased rubor in distal thigh region was noted. Radiography of the right femur revealed an unhealed distal femur fracture along with massive ossification extending from lesser trochanter to fracture line along the soft tissue around the femoral shaft. Conclusion This case presented the clinical and imaging findings of a giant heterotopic ossification in the thigh region following an extra-articular fracture.

Breath of relief: apparent pulmonary nodule due to heterotopic ossification

Extrapulmonary heterotopic ossification appears similarly to pulmonary nodules on CXR, and is in the differential for pulmonary nodules. It occurs following the bone trauma, and in early stages appears similarly to tumors. Heterotopic ossification is diagnosed by its calcification pattern via MRI or ultrasound and managed conservatively unless symptoms develop.

Heterotopic ossification and lessons learned from fifteen years at war: A review of therapy, novel research, and future directions for military and civilian orthopaedic trauma

Heterotopic ossification, the formation of bone in soft tissues, is a common complication of the high-energy extremity trauma sustained in modern armed conflict. In the past 15years, military treatment facilities and aligned laboratories have been in a unique position to study and treat this process due to the high volume of patients with these injuries secondary to blast trauma. The devastating nature of these wounds has limited traditional therapeutic options, necessitating alternative solutions to prophylaxis and initial treatment producing substantial advances in modeling, prophylaxis, detection, and therapy. Specific developments include establishment of an animal model that reproduces the systemic and local tissue injury of blast injuries, the use of molecular assays and predictive modeling in clinical decision making, advances in early detection including Raman spectroscopy, and investigation of prophylactic and therapeutic pharmacotherapy targeting the molecular pathways of aberrant bone formation. In this review article, we will present the literature to date, ongoing studies, and future directions for investigation of heterotopic ossification, with a focus on military-specific research.

Is heterotopic ossification getting nervous?: The role of the peripheral nervous system in heterotopic ossification

Heterotopic ossification (HO), or de novo bone formation in soft tissue, is often observed following traumatic injury. Recent studies suggest that peripheral nerves may play a key functional role in this process. The results supporting a neurological basis for HO are examined in this article. Evidence supports the fact that BMPs released from bone matrix possess the capacity to induce HO. However, the process cannot be recapitulated using recombinant proteins without extremely high doses suggesting other components are required for this process. Study of injuries that increase risk for HO, i.e. amputation, hip replacement, elbow fracture, burn, and CNS injury suggests that a likely candidate is traumatic injury of adjacent peripheral nerves. Recent studies suggest neuroinflammation may play a key functional role, by its ability to open the blood-nerve barrier (BNB). Barrier opening is characterized by a change in permeability and is experimentally assessed by the ability of Evans blue dye to enter the endoneurium of peripheral nerves. A combination of BMP and barrier opening is required to activate bone progenitors in the endoneurial compartment. This process is referred to as "neurogenic HO".

Inhibition of overactive TGF-β attenuates progression of heterotopic ossification in mice

Acquired heterotopic ossification (HO) is a painful and debilitating disease characterized by extraskeletal bone formation after injury. The exact pathogenesis of HO remains unknown. Here we show that TGF-β initiates and promotes HO in mice. We find that calcified cartilage and newly formed bone resorb osteoclasts after onset of HO, which leads to high levels of active TGF-β that recruit mesenchymal stromal/progenitor cells (MSPCs) in the HO microenvironment. Transgenic expression of active TGF-β in tendon induces spontaneous HO, whereas systemic injection of a TGF-β neutralizing antibody attenuates ectopic bone formation in traumatic and BMP-induced mouse HO models, and in a fibrodysplasia ossificans progressive mouse model. Moreover, inducible knockout of the TGF-β type II receptor in MSPCs inhibits HO progression in HO mouse models. Our study points toward elevated levels of active TGF-β as inducers and promoters of ectopic bone formation, and suggest that TGF-β might be a therapeutic target in HO.

Incidence and factors associated with development of heterotopic ossification after damage control laparotomy

INTRODUCTION

The incidence of heterotopic ossification (HO) following damage control laparotomy (DCL) is unknown. Abdominal wall reconstruction may prove more challenging in patients with HO. This study examines the incidence and factors associated with HO in patients with an open abdomen following DCL.

METHODS

A retrospective review of all patients with an open abdomen after DCL at a level 1 trauma centre from 2009 to 2015 was conducted. Demographics and peri-operative outcomes of patients with and without HO were compared. Univariate and multivariable binary logistic regression models were used to determine the association of peri-operative factors with the development of HO.

RESULTS

68 patients were included, of which 36 (53%) developed HO. On univariate analysis, development of HO was significantly associated with hollow viscus injury (OR, 3.89; CI 1.42-10.7), greater number of abdominal surgeries prior to definitive closure (OR, 1.84; CI, 1.10-3.05), non-fascial closure (OR, 4.33; CI, 1.44-13.1) and higher peak ALP (OR 1.01; CI, 1.00-1.02). The presence of a hollow viscus injury remained an independent predictor of HO on multivariable analysis after adjusting for covariates (OR, 3.77; CI, 1.22-11.6).

CONCLUSION

Heterotopic ossification develops in a high proportion of trauma patients following damage control laparotomy, particularly in the presence of hollow viscus injury. Its impact on delayed abdominal wall reconstruction and the efficacy of prophylaxis strategies merit further investigation.

The traumatic bone: trauma-induced heterotopic ossification

Heterotopic ossification (HO) is a common occurrence after multiple forms of extensive trauma. These include arthroplasties, traumatic brain and spinal cord injuries, extensive burns in the civilian setting, and combat-related extremity injuries in the battlefield. Irrespective of the form of trauma, heterotopic bone is typically endochondral in structure and is laid down via a cartilaginous matrix. Once formed, the heterotopic bone typically needs to be excised surgically, which may result in wound healing complications, in addition to a risk of recurrence. Refinements of existing diagnostic modalities, like micro- and nano-CT are being adapted toward early intervention. Trauma-induced HO is a consequence of aberrant wound healing, systemic and local immune system activation, infections, extensive vascularization, and innervation. This intricate molecular crosstalk culminates in activation of stem cells that initiate heterotopic endochondral ossification. Development of animal models recapitulating the unique traumatic injuries has greatly facilitated the mechanistic understanding of trauma-induced HO. These same models also serve as powerful tools to test the efficacy of small molecules which specifically target the molecular pathways underlying ectopic ossification. This review summarizes the recent advances in the molecular understanding, diagnostic and treatment modalities in the field of trauma-induced HO.