Characterization of heterotopic ossification in burn patients

A scoping review on active vs. passive range of motion approaches to treat heterotopic ossification at the elbow

Objective

The objective of this scoping review is to synthesize and clarify literature on the effectiveness of active and passive range of motion therapy techniques to address range of motion in people with heterotopic ossification (HO), and to provide guidance to therapists in clinical decision-making based on current evidence.

Method

To find articles that included therapeutic interventions to maintain or improve range of motion in people with heterotopic ossification, the authors searched the following databases: Cochrane Database of Systematic Reviews, PubMed, CINAHL, PsychINFO, Web of Science, and OTSeeker. To ensure that the search was comprehensive, the authors also searched Burns and Trauma, Burns Journal, Burns Open, and the Journal of Hand Therapy. Searches were limited to peer-reviewed articles published in the English language. No publication date limits were set. The Physiotherapy Evidence Database PEDro scale was utilized to measure the validity of the methodological quality of each article.

Results

Five studies met the inclusion criteria.. Two studies emphasized that passive range of motion was effective in less than 50% of their subjects, while the other three studies utilized active range of motion only, reporting 50% of patients did not require surgery.

Discussion/conclusion

There is insufficient evidence to determine effective therapeutic management of HO and the literature that does exist is contradictory and inconclusive. Future research is necessary to determine if any effectiveness of manual therapeutic approaches exists for patients with HO.

Routinely collected burn clinical data in Canada: Determining the knowledge gap

Unlike other developed countries that hold national burn registries to monitor burn injury and care, Canada relies on single-centre secondary datasets and administrative databases as surveillance mechanisms. The objective of this study was to determine the knowledge gap faced in Canada for not having a dedicated burn registry. A comprehensive scoping review was conducted to identify the burn literature that has arisen from secondary datasets in Canada. Literature of all study designs was included with the exception of case reports and cases series. Once data extraction was concluded, a thematic framework was constructed based on the information that arose from nations that hold national burn registries. Eighty-eight studies were included. Twelve studies arose from national datasets, and 18 from provincial databases, most of which were from Ontario and British Columbia. Only seven studies were conducted using a combination of Canadian units' single-centre datasets. The majority of included studies (58%) resulted from non-collaborative use of single-centre secondary datasets. Research efforts were predominantly conducted by burn units in Ontario, British Columbia, Manitoba and Alberta. A significant number of the included studies were outdated and several provinces/territories had no published burn data whatsoever. Efforts should be made towards the development of systems to surveil burn injury and care in Canada. This study supports the development of a nation-wide burn registry to bridge this knowledge gap.

Roles of Plasminogen Activator Inhibitor-1 in Heterotopic Ossification Induced by Achilles Tenotomy in Thermal Injured Mice

Heterotopic ossification (HO) is the process by which ectopic bone forms at an extraskeletal site. Inflammatory conditions induce plasminogen activator inhibitor 1 (PAI-1), an inhibitor of fibrinolysis, which regulates osteogenesis. In the present study, we investigated the roles of PAI-1 in the pathophysiology of HO induced by trauma/burn treatment using PAI-1-deficient mice. PAI-1 deficiency significantly promoted HO and increased the number of alkaline phosphatase (ALP)-positive cells in Achilles tendons after trauma/burn treatment. The mRNA levels of inflammation markers were elevated in Achilles tendons of both wild-type and PAI-1-deficient mice after trauma/burn treatment and PAI-1 mRNA levels were elevated in Achilles tendons of wild-type mice. PAI-1 deficiency significantly up-regulated the expression of Runx2, Osterix, and type 1 collagen in Achilles tendons 9 weeks after trauma/burn treatment in mice. In in vitro experiments, PAI-1 deficiency significantly increased ALP activity and mineralization in mouse osteoblasts. Moreover, PAI-1 deficiency significantly increased ALP activity and up-regulated osteocalcin expression during osteoblastic differentiation from mouse adipose-tissue-derived stem cells, but suppressed the chondrogenic differentiation of these cells. In conclusion, the present study showed that PAI-1 deficiency promoted HO in Achilles tendons after trauma/burn treatment partly by enhancing osteoblast differentiation and ALP activity in mice. Endogenous PAI-1 may play protective roles against HO after injury and inflammation.

Vegfc-expressing cells form heterotopic bone after musculoskeletal injury

Heterotopic ossification (HO) is a challenging condition that occurs after musculoskeletal injury and is characterized by the formation of bone in non-skeletal tissues. While the effect of HO on blood vessels is well established, little is known about its impact on lymphatic vessels. Here, we use a mouse model of traumatic HO to investigate the relationship between HO and lymphatic vessels. We show that injury triggers lymphangiogenesis at the injury site, which is associated with elevated vascular endothelial growth factor C (VEGF-C) levels. Through single-cell transcriptomic analyses, we identify mesenchymal progenitor cells and tenocytes as sources of Vegfc. We demonstrate by lineage tracing that Vegfc-expressing cells undergo osteochondral differentiation and contribute to the formation of HO. Last, we show that Vegfc haploinsufficiency results in a nearly 50% reduction in lymphangiogenesis and HO formation. These findings shed light on the complex mechanisms underlying HO formation and its impact on lymphatic vessels.

Heterotopic Ossification around the Elbow Revisited

Heterotopic ossification (HO) is the process of ectopic bone formation in the periarticular soft tissues and is usually formed in the elbow, hip and knee joint as a complication of trauma, burns, brain injury or surgical procedures. The development of HO around the elbow joint can cause a severe limitation of range of motion (ROM) and may affect daily activities of the patient. Treatment of ectopic bone formation around the elbow is a challenge for many surgeons. Non-operative treatment usually fails to restore the ROM of the elbow joint; thus, surgery is necessary to restore the function of the joint. In the past, many surgeons suggested that a delayed excision of HO, until maturation of the ectopic bone, is the best option in order to avoid any possible recurrence. However, many authors now suggest that this delay may lead to complications such as muscular atrophy and formation of soft tissue contractures that can cause a greater impairment of elbow function; thus, early excision is a better option and can better restore the elbow ROM. We performed a literature research of articles that investigated which is the best time of HO excision and we also evaluated if the tethering effect of HO can lead to a greater impairment of the elbow function. We found numerous studies suggesting that a limitation in ROM of the elbow can appear from the tethering of the ectopic bone formation and not only from primary HO. Concerning the HO excision, there were no significant differences between patients who underwent delayed and early excision, concerning the recurrence rate of HO around the elbow. Patients who underwent early excision had better restoration of elbow ROM; thus, early excision, combined with a rehabilitation program, is reported to be the best option for these patients.

Bony Cubital Tunnel Syndrome: A Case Report of Heterotopic Ossification Causing Circumferential Ulnar Nerve Encasement at the Elbow and Review of Current Management

BACKGROUND

Heterotopic ossification (HO) is a rare but known complication of brain and nerve trauma, orthopedic trauma, and burns. Nerve compression due to HO is extremely rare; "bony cubital tunnel syndrome," or compression of the ulnar nerve at the elbow due to HO, is an unusual presentation that requires special considerations for treatment.

CASE PRESENTATION

We present a 50-year-old man who presented to our hospital after vehicular polytrauma with associated car fire and prolonged extrication. He experienced extensive trauma, with all classically described risks for HO. He developed bony cubital tunnel syndrome, with ulnar neuropathy confirmed on electrodiagnostic studies, and underwent surgical decompression. Surgical decompression revealed circumferential encasement of the ulnar nerve in heterotopic bone, all of which was removed. He demonstrates appropriate recovery of nerve function.

LITERATURE REVIEW

All perineural HO should be excised early to prevent nerve injury, because excision within 4 months of development is linked to improved functional outcomes. Measures to prevent nerve compression by HO are all associated with delayed wound or bone healing and should be considered on an individual basis.

The effect of extracorporeal shock wave therapy on large neurogenic heterotopic ossification in a patient with pontine hemorrhage: A case report and literature review

RATIONALE

Heterotopic ossification (HO), an ectopic bone formation in soft tissue around the joint, is a complication observed in stroke patients. HO around the hip joint causes a reduction in the functional ability of patients by generating pain and limiting range of motion (ROM). In addition, it results in impaired mobility, ultimately affecting quality of life and increasing the mortality of patients. Extracorporeal shock wave therapy (ESWT) has demonstrated efficacy in treating soft tissue inflammation and has been used to reduce patients' pain in HO. However, almost none of the studies reported degradation in the size of HO on images obtained before and after ESWT application.

PATIENT CONCERNS AND DIAGNOSIS

We report a case of a 36-year-old man who developed HO around both hip joints 3 months after bilateral pontine hemorrhage.

INTERVENTIONS

Seven months after HO development, ESWT was administered to the area of HO every other day for a total of 10 sessions.

OUTCOMES

Immediately following treatment, the ROM of both hip joints increased. Thus the patient was able to maintain a sitting posture without having to be bound to the wheelchair. In addition, the tolerable sitting time before groaning increased from less than ten minutes to almost 60 minutes by the end of all ESWT sessions. Unlike other previous reports, a diminished HO size was confirmed by comparing plain X-rays and bone scans obtained before and after treatment sessions.

LESSONS

In this case, we report an objective size reduction in HO in radiologic findings after applying ESWT to both hips. ESWT is a safe, easy-to-apply, and noninvasive modality. We would like to emphasize the use of ESWT as a treatment option for HO to decrease the extent of HO, as well as to improve pain, spasticity and function in patients with stroke.

Identification of Risk Factors in the Development of Heterotopic Ossification After Primary Total Hip Arthroplasty

PURPOSE

Heterotopic ossification (HO) is a process by which bone forms abnormally in soft tissues. Known risk factors for developing HO include male sex, spinal cord injury, trauma, and surgery. We investigated additional risk factors in the development of HO after hip arthroplasty.

METHODS

We performed a retrospective review of electronic medical records of 4070 individuals who underwent hip arthroplasty from September 2010 to October 2019 at the University of California, San Francisco Hospital. Demographics, anthropometrics, medications, and comorbid conditions were used in logistic regression analysis to identify factors associated with the development of HO.

RESULTS

A total of 2541 patients underwent primary hip arthroplasty in the analyzed timeframe (46.04% men, mean age at procedure: 62.13 ± 13.29 years). The incidence of postsurgical HO was 3% (n = 80). A larger proportion of individuals who developed HO had underlying osteoporosis (P < 0.001), vitamin D deficiency (P < 0.001), spine disease (P < 0.001), type 1 or 2 diabetes (P < 0.001), amenorrhea (P = 0.037), postmenopausal status (P < 0.001), parathyroid disorders (P = 0.011), and history of pathologic fracture (P = 0.005). Significant predictors for HO development were Black/African American race [odds ratio (OR) 2.97, P = 0.005], preexisting osteoporosis (OR 2.72, P = 0.001), spine disease (OR 2.04, P = 0.036), and low estrogen states (OR 1.99, P = 0.025). In the overall group, 75.64% received perioperative nonsteroidal anti-inflammatory drugs (NSAIDs), which negatively correlated with HO formation (OR 0.39, P = 0.001).

CONCLUSIONS

We identified new factors potentially associated with an increased risk of developing HO after primary hip arthroplasty, including African American race, osteoporosis, and low estrogen states. These patients may benefit from HO prophylaxis, such as perioperative NSAIDs.

Heterotopic Ossification in Burn Patients

ABSTRACT

Heterotopic ossification (HO) is a known complication of burns. The incidence of this complication is low. The etiology is unclear, but experiment conducted about HO can be significant. Currently, there are still no targeted, effective preventive and therapeutic measures against it. In this study, the relevant literature is summarized to demonstrate the potential pathogenic mechanisms, diagnosis, prophylaxis, and treatment measures of HO in burn patients. Early diagnosis and treatment can be effective in improving the prognosis of patients.

[Research progress of traumatic heterotopic ossification]

OBJECTIVE

To review and evaluate the research progress of traumatic heterotopic ossification (HO).

METHODS

The domestic and foreign related research literature on traumatic HO was widely consulted, and its etiology, pathogenesis, pathological progress, diagnosis, prevention, and treatment were summarized.

RESULTS

Traumatic HO is often caused by severe trauma such as joint operation, explosion injury, nerve injury, and burn. At present, it is widely believed that the occurrence of traumatic HO is closely related to inflammation and hypoxia. Oral non-steroidal anti-inflammatory drugs and surgery are the main methods to prevent and treat traumatic HO.

CONCLUSION

Nowadays, the pathogenesis of traumatic HO is still unclear, the efficiency of relevant prevention and treatment measures is low, and there is a lack of specific treatment method. In the future, it is necessary to further study the pathogenesis of traumatic HO and find specific prevention and treatment targets.

Heterotopic Ossification: Clinical Features, Basic Researches, and Mechanical Stimulations

Heterotopic ossification (HO) is defined as the occurrence of extraskeletal bone in soft tissue. Although this pathological osteogenesis process involves the participation of osteoblasts and osteoclasts during the formation of bone structures, it differs from normal physiological osteogenesis in many features. In this article, the primary characteristics of heterotopic ossification are reviewed from both clinical and basic research perspectives, with a special highlight on the influence of mechanics on heterotopic ossification, which serves an important role in the prophylaxis and treatment of HO.

Surgical excision of heterotopic ossification associated with anti-N-methyl-d-aspartate receptor encephalitis: A case report

INTRODUCTION AND IMPORTANCE

Heterotopic ossification (HO) associated with Anti-N-methyl-d-aspartate (anti-NMDA) receptor encephalitis is rare and the treatment strategy is unclear.

CASE PRESENTATION

We report the case of a 31-year-old female diagnosed with anti-NMDA receptor encephalitis from Osaka General Medical Center, Osaka, JAPAN that developed heterotopic ossification of the knees during prolonged coma. She was unable to walk because of pain and limited range of motion in both knees. Thirty months after the onset of the coma, surgical excision of the heterotopic bone in both knees was performed. The range of motion of both the knees improved markedly and she had no recurrence of heterotopic ossification on a three-year follow-up. Thus, this case can be used as a guide for surgeons with such patients.

CONCLUSIONS

We reported a case of heterotopic bone formation in the periarticular region of both bilateral knees in a patient who suffered a 2-month coma following anti-NMDA receptor encephalitis. Surgical excision of the heterotopic bones significantly improved the passive range of motion in both knees. Three years after the operation, the patient had no complaints about her knees, and there was no recurrence of HO.

Heterotopic Ossification After Elbow Fractures

Heterotopic ossification (HO), a complication after surgical repair of elbow fractures, can result in pain, decreased range of motion, or complete ankylosis of the joint. This updated systematic review focused on compiling incidence and prevalence rates of HO after surgical repair of various types of elbow fractures. The overall incidence of HO after surgical repair was calculated to be 28.7%, a result comparable with rates in the literature. Further analysis suggested that the odds of having HO may be less after distal humerus fractures than after proximal radius fractures, terrible triad injuries, and elbow fractures/dislocations. [Orthopedics. 2021;44(1):10-16.].

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.

Early physiotherapy experience with a biodegradable polyurethane dermal substitute: Therapy guidelines for use

OBJECTIVE

The purpose of this study was to investigate and develop range of motion (ROM) and mobilisation guidelines in adult patients where a newly developed synthetic dermal substitute was applied in our adult burn centre.

METHOD

A retrospective case note audit was conducted on the first 20 acute burn injured patients who had a synthetic dermal substitute applied. Data collected included days to commencement of ROM, days to clearance for mobilisation, and joint ROM achieved after dermal substitute application (prior to delamination) and after split skin grafting (SSG) for the elbow, knee and shoulder joints. Scar assessments were completed at 12 months after injury using two scar assessment scales.

RESULTS

Clearance to mobilise occurred at mean 10.4 and 4.9 days after dermal substitute and after skin graft application to lower limbs respectively. ROM commenced at a mean of 9.9 (upper limbs) and 12.7 (lower limbs) days after dermal substitute application. Following skin grafting, ROM commenced at a mean of 6.6 and 6.5 days for upper limbs and lower limbs respectively. Prior to dermal substitute delamination mean flexion at the knee (86.3°), elbow (114.0°) and shoulder (143.4°) was achieved. Mean ROM continued to improve after grafting with knee (133.2°), elbow (126.1°) and shoulder (151.0°) flexion approaching normal ROM in most cases. Mean extension of the elbow (-4.6°) was maintained close to normal levels after skin grafting. There were no recorded instances of knee extension contracture. Patient and Observer Scar Assessment Scale and Matching Assessment of Photographs of Scars scores indicated good cosmetic outcomes with relatively low levels of itch and minimal pain reported at 12 months after injury.

CONCLUSION

A steep learning curve was encountered in providing therapy treatment for patients managed with this relatively new synthetic dermal substitute. Trends indicated that as experience with this new dermal substitute grew, patients progressed toward active therapy earlier. A guideline for therapy treatment has been developed but will continue to be evaluated and adjusted when required.

A Case Report of Heterotopic Ossification Caused by High-Voltage Electric Injury

This case report described the diagnosis and treatment of a patient with ectopic bone injury due to high-pressure electric shock. A 24-year-old male patient suffered from burns that covered 50% of TBSA, including on limbs and torso, after coming into contact with 10-kV high-voltage electricity. A repeated Meek micrografting technique (MEEK) was applied for wound healing; skin grafts were cut into micrografts and expanded at a ratio of 1:4 to cover large areas after burn trauma. After the injury, right elbow redness, fever, pains, and joint movement disorder were reported by the patient, which might be attributed to excessive exercises and acute scarring. However, these symptoms were not treated immediately. Six months after the injury, his right elbow joint showed 90° locking and a restricted 5° movement capacity. X-ray examination revealed a new bone formation at the inner tibia shin. In addition, 3D CT showed the formation of right tibia, the ruler bone, and the skull of the humming bridge. Under general anesthesia, the right elbow joint was released, the medial collateral ligament was repaired, and the hinge external fixator was fixed. A large number of hyperplastic bone masses were found at the right elbow joint during surgery, specifically in the foot bone hawk's beak nest. No complications after surgery were observed. X-ray examination in February showed disappearance of the bone bridge and normal relationship of the right elbow joint. This case study revealed that electric shock injury could lead to ectopic bone formation, and much attention should be paid on any changes that indicate aseptic inflammation, such as redness, swelling, fever, and pain during the treatment process. Finally, identification of the scar constriction phase could indicate surgical treatment in order to promote the limb rehabilitation process.

A Comparison of Contracture Severity at Acute Discharge in Patients With and Without Heterotopic Ossification: A Burn Model System National Database Study

This study assesses the association between heterotopic ossification and upper extremity contracture by comparing goniometric measured active range of motion outcomes of patients with and without heterotopic ossification. Data were obtained from the Burn Model System National Database between 1994 and 2003 for patients more than 18 years with elbow contracture at acute discharge. Absolute losses in elbow range of motion were compared for those with and without radiologic evidence of heterotopic ossification (location undefined) and were further examined by burn size subgroups using Wilcoxon rank-sum test. Differences in elbow range of motion were estimated using regression models, adjusted for demographic and clinical variables. Loss of range of motion of shoulder, wrist, forearm, and hand were also compared. From 407 instances of elbow contracture, the subjects with heterotopic ossification were found to have greater median absolute loss of elbow flexion among all survivors (median 50° [IQR 45°] vs 20° [30°], P < .0001), for the 20 to 40% total body surface area burn subgroup (70° [20°] vs 20° [30°], P = .0008) and for the >40% subgroup (50° [45°] vs 30° [32°], P = .03). The adjusted estimate of the mean difference in the absolute loss of elbow flexion between groups was 23.5° (SE ±7.2°, P = .0013). This study adds to our understanding of the potential effect of heterotopic ossification on upper extremity joint range of motion, demonstrating a significant association between the presence of heterotopic ossification and elbow flexion contracture severity. Further study is needed to determine the functional implications of heterotopic ossification and develop treatment protocols.

Cellular Plasticity in Musculoskeletal Development, Regeneration, and Disease

In this review, we highlight themes from a recent workshop focused on "Plasticity of Cell Fate in Musculoskeletal Tissues" held at the Orthopaedic Research Society's 2019 annual meeting. Experts in the field provided examples of mesenchymal cell plasticity during normal musculoskeletal development, regeneration, and disease. A thorough understanding of the biology underpinning mesenchymal cell plasticity may offer a roadmap for promoting regeneration while attenuating pathologic differentiation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:708-718, 2020.

Impact of oral resuscitation on circulating and splenic leukocytes after burns

BACKGROUND

Hemodynamic aberrations after severe burns are treated with aggressive intravenous (IV) fluid resuscitation however, oral resuscitation has been proposed in resource poor scenarios. Previously we have shown that animals receiving oral fluid following burns were able to recover kidney function. However, immune function such as circulating and splenic immune cell populations after oral or intravenous fluid administration was not examined. Herein, we perform a follow up analysis of splenic tissue and plasma from the previous animal study to examine the splenic response following these resuscitation strategies after burn injury.

METHODS

Eighteen anesthetized Yorkshire swine receiving 40%TBSA contact burns were randomized to receive either: (1) no fluids (Fluid Restricted; negative control), (2) 70 mL/kg/d Oral Rehydration Salt solution (Oral), or (3) 2 mL/kg/%TBSA/d of lactated Ringer's solution IV. Blood was drawn for blood cell analysis, and CT scans were performed before and 48 h post-burn, at which point spleens were harvested for histological, Western blot, and RT-PCR analyses.

RESULTS

Splenic artery diameter decreased by -0.97 ± 0.14 mm in fluid-restricted animals, while IV led to an increase of 0.68 ± 0.30 mm. No significant differences were detected in white and red pulp. IV fluids reduced the population of splenic monocytes (CD163; P = 0.001) and neutrophils (MPO protein; P = 0.13), as well as cytokines IL-8 (P = 0.003), IFN-γ (P = 0.11) and TNFα (P = 0.05). Additionally, withholding IV fluids consistently decreased the expression of FoxP3, CCR6, and IL17β in spleen, suggesting a shift in T-cell phenotype with IV resuscitation.

CONCLUSIONS

The route of fluid administration has a minor influence on the changes in circulating and splenic leukocytes post-burn in the acute phase. Further research is needed to help guide resuscitation approaches using immunologic markers of splenic function following burns.

Heterotopic ossification: radiological and pathological review

Background Heterotopic Ossification (HO) is a common condition referring to ectopic bone formation in soft tissues. It has two major etiologies, acquired (more common) and genetic. The acquired form is closely related to tissue trauma. The exact pathogenesis of this disease remains unclear; however, there is ongoing research in prophylactic and therapeutic treatments that is promising. Conclusions Due to HO potential to cause disability, it is so important to differentiate it from other causes in order to establish the best possible management.

Heterotopic Ossification: A Comprehensive Review

Heterotopic ossification (HO) is a diverse pathologic process, defined as the formation of extraskeletal bone in muscle and soft tissues. HO can be conceptualized as a tissue repair process gone awry and is a common complication of trauma and surgery. This comprehensive review seeks to synthesize the clinical, pathoetiologic, and basic biologic features of HO, including nongenetic and genetic forms. First, the clinical features, radiographic appearance, histopathologic diagnosis, and current methods of treatment are discussed. Next, current concepts regarding the mechanistic bases for HO are discussed, including the putative cell types responsible for HO formation, the inflammatory milieu and other prerequisite “niche” factors for HO initiation and propagation, and currently available animal models for the study of HO of this common and potentially devastating condition. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Demethylation of ITGAV accelerates osteogenic differentiation in a blast-induced heterotopic ossification in vitro cell culture model

Trauma-induced heterotopic ossification is an intriguing phenomenon involving the inappropriate ossification of soft tissues within the body such as the muscle and ligaments. This inappropriate formation of bone is highly prevalent in those affected by blast injuries. Here, we developed a simplified cell culture model to evaluate the molecular events involved in heterotopic ossification onset that arise from the shock wave component of the disease. We exposed three subtypes of human mesenchymal cells in vitro to a single, high-energy shock wave and observed increased transcription in the osteogenic master regulators, Runx2 and Dlx5, and significantly accelerated cell mineralisation. Reduced representation bisulfite sequencing revealed that the shock wave altered methylation of gene promoters, leading to opposing changes in gene expression. Using a drug to target ITGAV, whose expression was perturbed by the shock wave, we found that we could abrogate the deposition of mineral in our model. These findings show how new therapeutics for the treatment of heterotopic ossification can be identified using cell culture models.

Application of a mechanobiological algorithm to investigate mechanical mediation of heterotopic bone in trans-femoral amputees

Heterotopic ossification (HO) is the process of bone formation in tissues that are not usually osseous. It occurs in 60% of those with blast-related amputations. HO can result in reduced range of motion, pain, nerve impingement and can affect prosthesis fitting and is caused by a combination of mechanical, biological, local and systemic factors. As with normal bone formation and remodelling, it is expected that heterotopic bone responds to mechanical stimuli and understanding this relationship can give insight into the pathology. The objective of this research was to investigate whether a physiological 2D computational model that considers both mechanical and biological factors can be used to simulate HO in the residual limb of a trans-femoral amputee. The study found that characteristic morphologies of HO were reproduced by adjusting the loading environment. Significant effects were produced by changing the loading direction on the femur; this is potentially associated with different initial surgical interventions such as muscle myodesis. Also, initial treatment such as negative pressure through a dressing was found to change the shape of heterotopic bone.

Therapeutic strategies for elbow ankylosis due to heterotopic ossification in patients with severe burns

Background

Heterotopic ossification (HO) occurs frequently in the elbow in burn patients, and extends beyond the anatomical structure. HO of the elbow can cause joint contracture and adversely affect activities of daily living.Currently, there is no effective prophylaxis for HO as the precise underlying mechanism remains unknown. Therefore, there is no choice but to treat HO after it has developed. To date, however, no effective standard treatment has been reported, and therefore treatment methods vary between different facilities. Surgical resection is widely accepted as the only therapeutic option once HO limits functional mobility of the elbow.

Purposes

Based on past reports, we examined our cases and recommend effective therapeutic strategies. We posed the following three questions: (1) Is the surgical intervention effective or detrimental for elbow ankylosis due to HO? (2) What is the best timing for the intervention? (3) What is the most effective postoperative rehabilitation plan?

Methods

We treated three patients with complete ankylosis of the elbow due to HO after severe burn injury using different protocols.

Results

Surgery was performed in two cases and rehabilitation therapy was commenced immediately from the first postoperative day. Both patients showed improvement in the active range of motion in their elbow joints. The other patient did not undergo surgery, and his elbows became fixed in the completely extension position.

Conclusion

Surgical resection is beneficial for elbow ankylosis due to HO after burn injury. Although the exact surgical timing is still controversial, we recommend that surgery should be performed as soon as possible after improving the skin condition around the elbow and confirming the maturation of HO on radiographs. Early rehabilitation and pain control are also important after surgery.

Heterotopic ossification and the elucidation of pathologic differentiation

Tissue regeneration following acute or persistent inflammation can manifest a spectrum of phenotypes ranging from the adaptive to the pathologic. Heterotopic Ossification (HO), the endochondral formation of bone within soft-tissue structures following severe injury serves as a prominent example of pathologic differentiation; and remains a persistent clinical issue incurring significant patient morbidity and expense to adequately diagnose and treat. The pathogenesis of HO provides an intriguing opportunity to better characterize the cellular and cell-signaling contributors to aberrant differentiation. Indeed, recent work has continued to resolve the unique cellular lineages, and causative pathways responsible for ectopic bone development yielding promising avenues for the development of novel therapeutic strategies shown to be successful in analogous animal models of HO development. This review details advances in the understanding of HO in the context of inciting inflammation, and explains how these advances inform the current standards of diagnosis and treatment.

Stem cells and heterotopic ossification: Lessons from animal models

Put most simply, heterotopic ossification (HO) is the abnormal formation of bone at extraskeletal sites. HO can be classified into two main subtypes, genetic and acquired. Acquired HO is a common complication of major connective tissue injury, traumatic central nervous system injury, and surgical interventions, where it can cause significant pain and postoperative disability. A particularly devastating form of HO is manifested in the rare genetic disorder, fibrodysplasia ossificans progressiva (FOP), in which progressive heterotopic bone formation occurs throughout life, resulting in painful and disabling cumulative immobility. While the central role of stem/progenitor cell populations in HO is firmly established, the identity of the offending cell type(s) remains to be conclusively determined, and little is known of the mechanisms that direct these progenitor cells to initiate cartilage and bone formation. In this review, we summarize current knowledge of the cells responsible for acquired HO and FOP, highlighting the strengths and weaknesses of animal models used to interrogate the cellular origins of HO.

Long-Term Outcomes in Patients Surviving Large Burns: The Musculoskeletal System

The authors have previously described long-term outcomes related to the skin in patients surviving large burns. The objective of this study was to describe the long-term musculoskeletal complications following major burn injury. This is a cross-sectional descriptive study that includes a one-time evaluation of 98 burn survivors (mean age = 47 years; mean TBSA = 57%; and mean time from injury = 17 years), who consented to participate in the study. A comprehensive history and physical examination was conducted by a senior and experienced Physical Medicine and Rehabilitation physician. In addition to completing a Medical Problem Checklist, subjects also completed the Burn-Specific Health Scale (Abbreviated 80 item), a self-report measure used to review the level of functional adaptation. Joint pain, joint stiffness, problems walking or running, fatigue, and weak arms and hands are conditions that continue to be reported at an average of 17 years from the time of burn injury. Seventy-three percent (68 of 93) of the study sample were found to have a limitation of motion and areas most affected were the neck (47%), hands (45%), and axilla (38%). The global (Burn-Specific Health Scale-total) score for the overall sample was 0.78. Subjects with limitation of motion had significant difficulty in areas of mobility, self-care, hand function, and role activities. This study underscores the importance of long-term follow-up care and therapeutic interventions for survivors of major burn injury, as they continue to have significant and persistent burn-related impairments even several years following injury.

Our 35 years' experience on postburn heterotopic ossification: A three-step treatment

Our retrospective study of burn patients presents a three-step treatment of heterotopic ossification: excision surgery, early rehabilitation, and analgesia. We included patients admitted to the department for treatment of postburn heterotopic ossification between January 1, 1979, and September 30, 2015. The mean age at the time of the burn was 43.3 years. Men accounted for the majority of burn patients who developed an osteoma (70.8%). The mean total skin area burned was 38.4%. No osteoma justifying surgery was found for any patient with a total burned skin area less than 19%. The burned zones were related to the osteoma development in 94.3% of cases. On average, the surgery took place 10.8 months after the burn. The osteotomy was accompanied by surgical treatment of a contracture in 37.1% of patients. Most of the osteomata were found at the elbows (30), followed by the shoulders (3), and finally the knees (2). Rehabilitation began on D0 after the surgery, except if a flap or a thin-skin graft was used. Regarding analgesia, opiates were prescribed systematically during the immediate postoperative period. Elbow range of motion on flexion improved by a mean of 84.1°. During the postoperative period, we found 2 recurrences of osteoma and 1 elbow hematoma in two separate patients. There were no postoperative infections or neurological sequelae. Our retrospective French study confirmed results found in the international literature. The three-step treatment - excision surgery, early rehabilitation, and antalgia - seems to be the best means of treating osteoma with satisfactory results. Surgery is indicated only in the case of functional impairment and not simply based on imaging.

Predicting Heterotopic Ossification Early After Burn Injuries: A Risk Scoring System

OBJECTIVE

The purpose of this study is to develop a scoring system that stratifies burn patients at the time of hospital admission according to risk of developing heterotopic ossification (HO).

SUMMARY OF BACKGROUND DATA

HO in burns is an uncommon but severely debilitating problem with a poorly understood mechanism and no fully effective prophylactic measures.

METHODS

Data were obtained from the Burn Model System National Database from 1994 to 2010 (n = 3693). The primary outcome is diagnosis of HO at hospital discharge. Logistic regression analysis was used to determine significant demographic and medical predictors of HO. A risk scoring system was created in which point values were assigned to predictive factors and final risk score is correlated with the percent risk of developing HO. The model was internally and externally validated.

RESULTS

The mean age of the subjects is 42.5 ± 16.0 years, the mean total body surface area (TBSA) burned is 18.5 ± 16.4%, and the population is 74.9% male. TBSA and the need for grafting of the arm, head/neck, and trunk were significant predictors of HO development (P < 0.01). A 13-point risk scoring system was developed using these significant predictors. The model c-statistic is 0.92. The risk scoring system demonstrated evidence of internal and external validity. An online calculator was developed to facilitate translation of knowledge to practice and research.

CONCLUSIONS

This HO risk scoring system identifies high-risk burn patients suitable for diagnostic testing and interventional HO prophylaxis trials.

Two new risk factors for heterotopic ossification development after severe burns

Objectives

Life after severe burns is conditioned by the remaining sequelae. The pathophysiology and risk factors of Heterotopic Ossification (HO) after burns are still poorly understood. The aim of this study was to determine: 1) the incidence of HO after burns and 2) the risk factors associated with HO development, in a large retrospective study.

Methods

A case-control study of patients admitted to the burns intensive care unit of Percy Hospital, Paris, from the 1^st January 2009 to the 31^st December 2013 and then admitted to one of three centres specialised in the rehabilitation of patients with burns. Multivariate analysis was carried out to analyse the relationship between HO development and demographic and clinical data.

Results

805 patients were included. 32 patients (4.0%) developed a total of 74 heterotopic ossifications, that is a little higher incidence than the incidence found in the literature. The epidemiological characteristics of the population studied was similar to the literature. HOs were mainly localized around the elbows, followed by the hips, shoulders and knees. Each case-patient was paired with 3 control-patients. There were significant associations between HO development and the length of stay in the burns intensive care unit, the extent and depth of the burns, the occurrence of pulmonary or cutaneous infections, use of curare and use of an air-fluidized bed.

Conclusion

In addition to recognized risk factors (duration of stay in the intensive care burns unit, extent and depth of burns, pulmonary and cutaneous infections), the use of curare and the use of a fluidized bed (with the duration of use) were significantly associated with HO formation.

Acquired heterotopic ossification of the temporomandibular joint

Although the risk factors and diagnosis of heterotopic ossification (HO) are discussed in the orthopedics literature, the etiology of HO, as well as its prevention and management, remain theoretical. Furthermore, there is a lack of information in the literature regarding HO in temporomandibular joint replacement (TMJR). This article provides a qualitative review of information relative to the etiology, diagnosis, and management of HO to inform and encourage further investigation in TMJR. The orthopedic HO literature considered for this qualitative review was drawn from a comprehensive examination of the subject published previously by one of the authors. Using the key words "heterotopic ossification" or "heterotopic bone", citations in the PubMed database from both the dental and oral and maxillofacial surgery literature were reviewed. Based on this, it appears that the etiology, diagnosis, imaging, laboratory testing, risk factors, prophylaxis, and non-surgical and surgical options available for the management of TMJR-related HO are similar to those for orthopedic HO, but further elucidation is required for TMJR. There is a lack of published information in the literature on TMJR. Therefore, using the literature from this review as a foundation, studies should be developed and reported so that alloplastic TMJ surgeons have evidence-based protocols that will lead to the early detection and potential prevention of HO.

Heterotopic Ossification and Hypertrophic Scars

Burns and trauma cause superficial and deep soft tissue wounds that cannot heal to the preinjury state. Healing requires cell proliferation and differentiation into the injured tissue type, laying down extracellular matrix, often as collagens. Heterotopic ossification causes severe pain, nonhealing wounds, and restricted range of motion. Treatment includes radiation therapy, nonsteroidal anti-inflammatory drugs, bisphosphonates, and possibly surgical excision and prophylactic measures. Hypertrophic scars, nonosseous lesions caused by excessive collagen deposition, are often painful, functionally limiting, and aesthetically displeasing. Treatment includes CO2 laser application, steroid injections, and excision with skin grafting. This article reviews the management of these pathologic wounds.

Important Developments in Burn Care

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Explain the epidemiology of severe burn injury in the context of socioeconomic status, gender, age, and burn cause. 2. Describe challenges with burn depth evaluation and novel methods of adjunctive assessment. 3. Summarize the survival and functional outcomes of severe burn injury. 4. State strategies of fluid resuscitation, endpoints to guide fluid titration, and sequelae of overresuscitation. 5. Recognize preventative measures of sepsis. 6. Explain intraoperative strategies to improve patient outcomes, including hemostasis, restrictive transfusion, temperature regulation, skin substitutes, and Meek skin grafting. 7. Translate updates in the pathophysiology of hypertrophic scarring into novel methods of clinical management. 8. Discuss the potential role of free tissue transfer in primary and secondary burn reconstruction.

SUMMARY

Management of burn-injured patients is a challenging and unique field for plastic surgeons. Significant advances over the past decade have occurred in resuscitation, burn wound management, sepsis, and reconstruction that have improved outcomes and quality of life after thermal injury. However, as patients with larger burns are resuscitated, an increased risk of nosocomial infections, sepsis, compartment syndromes, and venous thromboembolic phenomena have required adjustments in care to maintain quality of life after injury. This article outlines a number of recent developments in burn care that illustrate the evolution of the field to assist plastic surgeons involved in burn care.

Postburn Contractures of the Elbow and Heterotopic Ossification

Postburn contractures of the elbow are uncommon debilitating sequelae of severe burn injuries, which result from thermal injury to both deep and superficial tissues. When periarticular heterotopic bone forms in association with burn injuries, severe and rigid contractures may develop that prohibit basic functions of daily living and are often refractory to nonoperative intervention. Surgical intervention is aimed at releasing or excising all pathologic anatomy limiting elbow motion. In patients with proper indications, surgical intervention can result in substantial improvement in elbow motion, allowing patients to return to activities of daily living, employment, and recreational activities.

Vascular patterning in human heterotopic ossification

Heterotopic ossification (HO, also termed myositis ossificans) is the formation of extra-skeletal bone in muscle and soft tissues. HO is a tissue repair process gone awry, and is a common complication of surgery and traumatic injury. Medical strategies to prevent and treat HO fall well short of addressing the clinical need. Better characterization of the tissues supporting HO is critical to identifying therapies directed against this common and sometimes devastating condition. The physiologic processes of osteogenesis and angiogenesis are highly coupled and interdependent. However, few efforts have been made to document the vascular patterning within heterotopic ossification. Here, surgical pathology case files of 29 human HO specimens were examined by vascular histomorphometric analysis. Results demonstrate a temporospatial patterning of HO vascularity that depends on the "maturity" of the bony lesion. In sum, human HO demonstrates a time- and space-dependent pattern of vascularization suggesting a coupled pathophysiologic process involving the coordinate processes of osteogenesis and angiogenesis. Further imaging studies may be used to further characterize vasculogenesis within HO and whether anti-angiogenic therapies are a conceivable future therapy for this common condition.

Heterotopic Ossification Following Upper Extremity Injury

Heterotopic ossification (HO) presents a substantial barrier to rehabilitation for patients with severe burns or trauma. Although surgical excision is a mainstay of management for this condition, this is unable to address the chronic sequelae of HO, including chronic pain, joint contractures, nerve dysfunction, and open wounds. Current therapeutic modalities are aimed at excision and the prevention of recurrence using nonsteroidal antiinflammatory drugs (NSAIDs) or radiation therapy. Research is now focused on identifying alternative strategies to prevent the initial occurrence of HO through NSAIDs and novel inhibitors of the bone morphogenetic protein signaling pathway.

Heterotopic Ossification in adults following a burn: A phenomenological analysis

Heterotopic Ossification (HO) is a rare but severely debilitating complication after a burn. Despite there being literature of varying quality explaining the postulated pathological process, risk factors and treatment for HO, the individual experiences of adults diagnosed with HO following a burn, remains unreported. This study sought to explore and describe burn survivors' experiences of HO to gain a greater understanding of the clinical needs for this unique patient population. A phenomenological inquiry of five men and one woman selected through purposeful sampling collected in-depth interviews analysed using Colaizzi's method of data analysis. Five emergent themes: (1) Early signs and symptoms, (2) Impact on the rehabilitation journey, (3) The role of the health care professionals (4) Loss of independence and an increased reliance on others and, (5) Learning to live with it: uncertainty, hope and adaptation. Eleven cluster themes were identified, highlighting the meaning of each emergent theme. These findings describe the significant impact the unique symptomology of HO had on the physical and psychosocial functioning of participants throughout the rehabilitation journey. Central to engagement in rehabilitation, is the participants' desire for autonomy particularly in the domains of living independently and community re-integration.

The development and impact of heterotopic ossification in burns: a review of four decades of research

Background to this subject:

Heterotopic ossification (HO) is the formation of bone within the tissue where bone should not form and is a rare complication after burn injury. However, it leads to severe pain and distress, marked reduction in joint range of motion (ROM), impaired function and increased hospital length of stay. The pathophysiology, incidence and risk factors of HO remain poorly understood in burns and other traumas and the management, controversial.

Question being asked or issue explored:

The aim of this comprehensive review was to synthesise the available evidence on the development and treatment of HO after acute burn injury.

Details of how the work was conducted:

The review was based on a systematic search of medical electronic databases to identify relevant published literature.

What we did and did not learn from this study:

Synthesis and analysis of the data highlighted that, despite the passage of time, little translatable evidence is available to guide any prevention, screening, diagnostic or pharmacological or physical management protocols. Causes of HO remain confounded, therefore prevention is difficult. Although spontaneous resolution is possible, surgical resection remains the recommended treatment when ROM and activities of daily living are severely affected. The findings from this review indicate that multicentre data pooling is needed to understand the optimum pathway to prevention, identification and treatment of HO in acute burn patients.

Pressure ulcer reconstruction in patients with heterotopic ossification after spinal cord injury: A case series and review of literature

Heterotopic ossification (HO) is widely recognized as a common occurrence among patients suffering from traumatic spinal cord injuries (SCI). The exact etiology of HO formation remains unknown. Published medical and surgical management strategies are often plagued with questionable effectiveness and frequent complications. There are minimal publications regarding the management strategies of HO in SCI patients as it pertains to plastic surgery. We present a case series of patients treated at our institution who underwent treatment for pressure ulcers with underlying HO to highlight the vast spectrum of clinical phenotypes present in this population. The pathophysiology, diagnostic tools, methods of prevention, and surgical management of HO are discussed here. We believe that there are two clinically relevant patterns of HO in SCI patients. A neurogenic process that occurs early after injury is usually bilateral and involves uninjured hip joints. Pressure sores that occur are related to poor joint mobility and subsequent development of pressure points. An infection-driven process in which HO development is associated with either pressure sores or septic hip joints is generally unilateral and not always associated with hip contractures. They present different challenges and reconstructive options to plastic surgeons. Although complications such as infection and HO recurrence are common, the functional and psychological benefits of restoring hip flexion are usually worthwhile.

Targeted stimulation of retinoic acid receptor-γ mitigates the formation of heterotopic ossification in an established blast-related traumatic injury model

Heterotopic ossification (HO) involves formation of endochondral bone at non-skeletal sites, is prevalent in severely wounded service members, and causes significant complications and delayed rehabilitation. As common prophylactic treatments such as anti-inflammatory drugs and irradiation cannot be used after multi-system combat trauma, there is an urgent need for new remedies. Previously, we showed that the retinoic acid receptor γ agonist Palovarotene inhibited subcutaneous and intramuscular HO in mice, but those models do not mimic complex combat injury. Thus, we tested Palovarotene in our validated rat trauma-induced HO model that involves blast-related limb injury, femoral fracture, quadriceps crush injury, amputation and infection with methicillin-resistant Staphylococcus aureus from combat wound infections. Palovarotene was given orally for 14days at 1mg/kg/day starting on post-operative day (POD) 1 or POD-5, and HO amount, wound dehiscence and related processes were monitored for up to 84days post injury. Compared to vehicle-control animals, Palovarotene significantly decreased HO by 50 to 60% regardless of when the treatment started and if infection was present. Histological analyses showed that Palovarotene reduced ectopic chondrogenesis, osteogenesis and angiogenesis forming at the injury site over time, while fibrotic tissue was often present in place of ectopic bone. Custom gene array data verified that while expression of key chondrogenic and osteogenic genes was decreased within soft tissues of residual limb in Palovarotene-treated rats, expression of cartilage catabolic genes was increased, including matrix metalloproteinase-9. Importantly, Palovarotene seemed to exert moderate inhibitory effects on wound healing, raising potential safety concerns related to dosing and timing. Our data show for the first time that Palovarotene significantly inhibits HO triggered by blast injury and associated complications, strongly indicating that it may prevent HO in patients at high risk such as those sustaining combat injuries and other forms of blast trauma.

Risk factors for the development of heterotopic ossification in seriously burned adults: A National Institute on Disability, Independent Living and Rehabilitation Research burn model system database analysis

BACKGROUND

Heterotopic ossification (HO) is a debilitating complication of burn injury; however, incidence and risk factors are poorly understood. In this study, we use a multicenter database of adults with burn injuries to identify and analyze clinical factors that predict HO formation.

METHODS

Data from six high-volume burn centers, in the Burn Injury Model System Database, were analyzed. Univariate logistic regression models were used for model selection. Cluster-adjusted multivariate logistic regression was then used to evaluate the relationship between clinical and demographic data and the development of HO.

RESULTS

Of 2,979 patients in the database with information on HO that addressed risk factors for development of HO, 98 (3.5%) developed HO. Of these 98 patients, 97 had arm burns, and 96 had arm grafts. When controlling for age and sex in a multivariate model, patients with greater than 30% total body surface area burn had 11.5 times higher odds of developing HO (p < 0.001), and those with arm burns that required skin grafting had 96.4 times higher odds of developing HO (p = 0.04). For each additional time a patient went to the operating room, odds of HO increased by 30% (odds ratio, 1.32; p < 0.001), and each additional ventilator day increased odds by 3.5% (odds ratio, 1.035; p < 0.001). Joint contracture, inhalation injury, and bone exposure did not significantly increase odds of HO.

CONCLUSION

Risk factors for HO development include greater than 30% total body surface area burn, arm burns, arm grafts, ventilator days, and number of trips to the operating room. Future studies can use these results to identify highest-risk patients to guide deployment of prophylactic and experimental treatments.

LEVEL OF EVIDENCE

Prognostic study, level III.

Fibrocytes participate in the development of heterotopic ossification

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

Role of gender in burn-induced heterotopic ossification and mesenchymal cell osteogenic differentiation

BACKGROUND

Heterotopic ossification most commonly occurs after burn injury, joint arthroplasty, and trauma. Male gender has been identified as a risk factor for the development of heterotopic ossification. It remains unclear why adult male patients are more predisposed to this pathologic condition than adult female patients. In this study, the authors use their validated tenotomy/burn model to explore differences in heterotopic ossification between male and female mice.

METHODS

The authors used their Achilles tenotomy and burn model to evaluate the osteogenic potential of mesenchymal stem cells of male and female injured and noninjured mice. Groups consisted of injured male (n = 3), injured female (n = 3), noninjured male (n = 3), and noninjured female (n = 3) mice. The osteogenic potential of cells harvested from each group was assessed through RNA and protein levels and quantified using micro-computed tomographic scan. Histomorphometry was used to verify micro-computed tomographic findings, and immunohistochemistry was used to assess osteogenic signaling at the site of heterotopic ossification.

RESULTS

Mesenchymal stem cells of male mice demonstrated greater osteogenic gene and protein expression than those of female mice (p < 0.05). Male mice in the burn group formed 35 percent more bone than female mice in the burn group. This bone formation correlated with increased pSmad and insulin-like growth factor 1 signaling at the heterotopic ossification site in male mice.

CONCLUSIONS

The authors demonstrate that male mice form quantitatively more bone compared with female mice using their burn/tenotomy model. These findings can be explained at least in part by differences in bone morphogenetic protein and insulin-like growth factor 1 signaling.

Heterotopic Ossification: Basic-Science Principles and Clinical Correlates

➤ Heterotopic ossification occurs most commonly after joint arthroplasty, spinal cord injury, traumatic brain injury, blast trauma, elbow and acetabular fractures, and thermal injury.➤ The conversion of progenitor cells to osteogenic precursor cells as a result of cell-mediated interactions with the local tissue environment is affected by oxygen tension, pH, availability of micronutrients, and mechanical stimuli, and leads to heterotopic ossification.➤ Radiation and certain nonsteroidal anti-inflammatory medications are important methods of prophylaxis against heterotopic ossification.➤ Well-planned surgical excision can improve patient outcomes regardless of the joint involved or the initial cause of injury.➤ Future therapeutic strategies are focused on targeted inhibition of local factors and signaling pathways that catalyze ectopic bone formation.

Cationic Nanogel-mediated Runx2 and Osterix siRNA Delivery Decreases Mineralization in MC3T3 Cells

BACKGROUND

Heterotopic ossification (HO) may occur after musculoskeletal trauma, traumatic brain injury, and total joint arthroplasty. As such, HO is a compelling clinical concern in both military and civilian medicine. A possible etiology of HO involves dysregulated signals in the bone morphogenetic protein osteogenic cascade. Contemporary treatment options for HO (ie, nonsteroidal antiinflammatory drugs and radiation therapy) have adverse effects associated with their use and are not biologically engineered to abrogate the molecular mechanisms that govern osteogenic differentiation.

QUESTIONS/PURPOSES

We hypothesized that (1) nanogel-mediated short interfering RNA (siRNA) delivery against Runt-related transcription factor 2 (Runx2) and osterix (Osx) genes will decrease messenger RNA expression; (2) inhibit activity of the osteogenic marker alkaline phosphatase (ALP); and (3) inhibit hydroxyapatite (HA) deposition in osteoblast cell cultures.

METHODS

Nanogel nanostructured polymers delivered siRNA in 48-hour treatment cycles against master osteogenic regulators, Runx2 and Osx, in murine calvarial preosteoblasts (MC3T3-E1.4) stimulated for osteogenic differentiation by recombinant human bone morphogenetic protein (rhBMP-2). The efficacy of RNA interference (RNAi) therapeutics was determined by quantitation of messenger RNA knockdown (by quantitative reverse transcription-polymerase chain reaction), downstream protein knockdown (determined ALP enzymatic activity assay), and HA deposition (determined by OsteoImage™ assay).

RESULTS

Gene expression assays demonstrated that nanogel-based RNAi treatments at 1:1 and 5:1 nanogel:short interfering RNA weight ratios reduced Runx2 expression by 48.59% ± 19.53% (p < 0.001) and 43.22% ± 18.01% (both p < 0.001). The same 1:1 and 5:1 treatments against both Runx2 and Osx reduced expression of Osx by 51.65% ± 10.85% and 47.65% ± 9.80% (both p < 0.001). Moreover, repeated 48-hour RNAi treatment cycles against Runx2 and Osx rhBMP-2 administration reduced ALP activity after 4 and 7 days. ALP reductions after 4 days in culture by nanogel 5:1 and 10:1 RNAi treatments were 32.4% ± 12.0% and 33.6% ± 13.8% (both p < 0.001). After 7 days in culture, nanogel 1:1 and 5:1 RNAi treatments produced 35.9% ± 14.0% and 47.7% ± 3.2% reductions in ALP activity. Osteoblast mineralization data after 21 days suggested that nanogel 1:1, 5:1, and 10:1 RNAi treatments decreased mineralization (ie, HA deposition) from cultures treated only with rhBMP-2 (p < 0.001). However, despite RNAi attack on Runx2 and Osx, HA deposition levels remained greater than non-rhBMP-2-treated cell cultures.

CONCLUSIONS

Although mRNA and protein knockdown were confirmed as a result of RNAi treatments against Runx2 and Osx, complete elimination of mineralization processes was not achieved. RNAi targeting mid- and late-stage osteoblast differentiation markers such as ALP, osteocalcin, osteopontin, and bone sialoprotein) may produce the desired RNAi-nanogel nanostructured polymer HO prophylaxis.

CLINICAL RELEVANCE

Successful HO prophylaxis should target and silence osteogenic markers critical for heterotopic bone formation processes. The identification of such markers, beyond RUNX2 and OSX, may enhance the effectiveness of RNAi prophylaxes for HO.

Biology and principles of scar management and burn reconstruction

Hypertrophic scarring is extremely common and is the source of most morbidity related to burns. The biology of hypertrophic healing is complex and poorly understood. Multiple host and injury factors contribute, but protracted healing of partial thickness injury is a common theme. Hypertrophic scarring and heterotopic ossification may share some basic causes involving marrow-derived cells. Several traditional clinical interventions exist to modify hypertrophic scar. All have limited efficacy. Laser interventions for scar modification show promise, but as yet do not provide a definitive solution. Their efficacy is only seen when used as part of a multimodality scar management program.