Impact of late surgical intervention on heterotopic ossification of the hip after traumatic neurological injury

Comparative analysis of 'functional excision' of heterotopic ossification around the hip - computed tomography (CT) navigation guided versus conventional excision

PURPOSE

We aim to analyse and compare the efficacy of the excision of HO around the hip with and without CT-guided navigation. We also aim to compare the functional outcome between CT navigation guided versus conventional excision of HO.

PATIENTS AND METHODS

This study is a retrospective analysis of prospectively collected data from 2015 to 2022. There were 23 patients (24 hips) in the final cohort. Intraoperative CT navigation guided excision was performed in 7 hips and conventional excision of HO was done in 17 hips. The HO was classified by Brooker's grading in radiographs. CT scan was taken preoperatively in all patients to exactly identify the volume, location and preoperative planning. The functional outcome was analysed according to Harris Hip Score (HHS) and International Hip Outcome Tool (iHOT) for self-ambulatory patients and improvement in the sitting or nursing care was assessed in patients mobilising with wheelchair or walker support. Any complications or recurrence noted postoperatively and in follow-up were recorded.

RESULTS

The mean follow-up was 41.2 months in the CT navigation-guided excision group and 55 months in the conventional excision group. According to Brooker's grading, grade IV was present in 20 hips and grade III in four hips. Twelve patients were self-ambulatory and the other 12 patients were requiring support for mobilisation. There was a significant improvement in the HHS from 21.3 ± 3.7, 18.3 ± 2.5 preoperatively to 75.2 ± 8.3, 72.2 ± 4.3 postoperatively in the CT navigation guided and conventional group respectively (p < 0.001) in the self-ambulatory group. There was one anterior wall and one partial posterior wall fracture in the conventional group. One patient in the conventional group had a deep infection and recurrence. One patient had a superficial infection and another had superficial vein thrombosis in the CT guided excision group.

CONCLUSION

Intraoperative CT navigation helps to exactly localize the HO and facilitates safe excision. Functional excision of the HO leads to better nursing care and functional outcomes between both groups.

Genetic regulation of injury-induced heterotopic ossification in adult zebrafish

Heterotopic ossification is the inappropriate formation of bone in soft tissues of the body. It can manifest spontaneously in rare genetic conditions or as a response to injury, known as acquired heterotopic ossification. There are several experimental models for studying acquired heterotopic ossification from different sources of damage. However, their tenuous mechanistic relevance to the human condition, invasive and laborious nature and/or lack of amenability to chemical and genetic screens, limit their utility. To address these limitations, we developed a simple zebrafish injury model that manifests heterotopic ossification with high penetrance in response to clinically emulating injuries, as observed in human myositis ossificans traumatica. Using this model, we defined the transcriptional response to trauma, identifying differentially regulated genes. Mutant analyses revealed that an increase in the activity of the potassium channel Kcnk5b potentiates injury response, whereas loss of function of the interleukin 11 receptor paralogue (Il11ra) resulted in a drastically reduced ossification response. Based on these findings, we postulate that enhanced ionic signalling, specifically through Kcnk5b, regulates the intensity of the skeletogenic injury response, which, in part, requires immune response regulated by Il11ra.

Bacterial Lipopolysaccharides Exacerbate Neurogenic Heterotopic Ossification Development

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

Contemporary perspectives on heterotopic ossification

Heterotopic ossification (HO) is the formation of ectopic bone that is primarily genetically driven (fibrodysplasia ossificans progressiva [FOP]) or acquired in the setting of trauma (tHO). HO has undergone intense investigation, especially over the last 50 years, as awareness has increased around improving clinical technologies and incidence, such as with ongoing wartime conflicts. Current treatments for tHO and FOP remain prophylactic and include NSAIDs and glucocorticoids, respectively, whereas other proposed therapeutic modalities exhibit prohibitive risk profiles. Contemporary studies have elucidated mechanisms behind tHO and FOP and have described new distinct niches independent of inflammation that regulate ectopic bone formation. These investigations have propagated a paradigm shift in the approach to treatment and management of a historically difficult surgical problem, with ongoing clinical trials and promising new targets.

Spinal cord injury reprograms muscle fibroadipogenic progenitors to form heterotopic bones within muscles

The cells of origin of neurogenic heterotopic ossifications (NHOs), which develop frequently in the periarticular muscles following spinal cord injuries (SCIs) and traumatic brain injuries, remain unclear because skeletal muscle harbors two progenitor cell populations: satellite cells (SCs), which are myogenic, and fibroadipogenic progenitors (FAPs), which are mesenchymal. Lineage-tracing experiments using the Cre recombinase/LoxP system were performed in two mouse strains with the fluorescent protein ZsGreen specifically expressed in either SCs or FAPs in skeletal muscles under the control of the Pax7 or Prrx1 gene promoter, respectively. These experiments demonstrate that following muscle injury, SCI causes the upregulation of PDGFRα expression on FAPs but not SCs and the failure of SCs to regenerate myofibers in the injured muscle, with reduced apoptosis and continued proliferation of muscle resident FAPs enabling their osteogenic differentiation into NHOs. No cells expressing ZsGreen under the Prrx1 promoter were detected in the blood after injury, suggesting that the cells of origin of NHOs are locally derived from the injured muscle. We validated these findings using human NHO biopsies. PDGFRα⁺ mesenchymal cells isolated from the muscle surrounding NHO biopsies could develop ectopic human bones when transplanted into immunocompromised mice, whereas CD56⁺ myogenic cells had a much lower potential. Therefore, NHO is a pathology of the injured muscle in which SCI reprograms FAPs to undergo uncontrolled proliferation and differentiation into osteoblasts.

Lymphocytes Are Not Required for Neurogenic Heterotopic Ossification Development after Spinal Cord Injury

Neurogenic heterotopic ossifications (NHOs) are incapacitating complications of traumatic brain and spinal cord injuries (SCI) that manifest as abnormal bone formation in periarticular muscles. Using a unique model of NHO after SCI in genetically unmodified mice, we have previously established that the innate immune system plays a key driving role in NHO pathogenesis. The role of adaptive immune cells in NHO pathogenesis, however, remains unexplored in this model. Here we established that B lymphocytes were reduced in the spleen and blood after SCI and increased in muscles of mice in which NHO develops, whereas minimal changes in T cell frequencies were noted. Interestingly, Rag1^-/- mice lacking mature T and B lymphocytes, developed NHO, similar to wild-type mice. Finally, mice that underwent splenectomy before SCI and muscle damage also developed NHO to the same extent as non-splenectomized SCI controls. Overall, our findings show that functional T and B lymphocytes have minimal influence or dispensable contributions to NHO development after experimental SCI in mice.

Comparison of magnetic resonance imaging and computed tomography for bone assessment of neurogenic heterotopic ossification of the hip: a preliminary study

Background

Neurogenic heterotopic ossification (NHO) is a frequent complication, often involving the hip. The functional impact may require surgical management and pre-surgical imaging assessment is necessary, usually by computed tomography (CT). We aimed to compare the performances of magnetic resonance imaging (MRI) and CT for bone assessment on pre-surgical imaging of the heterotopic ossifications and their features in NHO of the hip.

Methods

This single-center prospective preliminary study included all patients who underwent surgery for NHO with joint limitation from July 2019 to March 2020. All patients had a CT after biphasic iodinated solution injection and an MRI including T1-weighted, STIR and ZTE sequences. Standardized reports were completed for both exams for each patient, evaluating location, implantation and fragmentation of NHO, relation to the joint capsule and bone mineralization, then were compared.

Results

Seven patients from 32 to 70 years old (mean = 50.2 ± 17.2 years) were evaluated. NHO were bilateral in 2 patients, for a total of nine hips: six right hips and three left hips. Observed concordance rates between MRI and CT were, respectively, 94.4% for location, 100% for circumferential extension, 87.3% for implantation 88.9% for fragmentation, 77.8% for relation to the joint capsule and 66.7% for bone mineralization. It was 100% for femoral neck fracture and osteonecrosis of the femoral head.

Conclusion

This preliminary study suggests that pre-surgical MRI imaging should be considered as effective as CT for bone assessment of NHO and their features.

Trial registration: ClinicalTrials.gov, NCT03832556. Registered February 6, 2019, https://clinicaltrials.gov/ct2/show/NCT03832556.

Neurogenic heterotopic ossification in the upper limb

Neurogenic heterotopic ossifications (NHOs) are periarticular ectopic ossifications that frequently develop after a central nervous system injury, most often a traumatic one. They limit range of motion and cause pain, interfering with limb positioning and function, whether active or passive. Highly described in the lower limbs, NHOs can also develop in the upper limb, with specific characteristics depending on their location. This article provides a summary of the diagnostic and therapeutic management of NHOs in the upper limb, based on the current literature.

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

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

Neurogenic Heterotopic Ossifications Develop Independently of Granulocyte Colony-Stimulating Factor and Neutrophils

Neurogenic heterotopic ossifications (NHOs) are incapacitating heterotopic bones in periarticular muscles that frequently develop following traumatic brain or spinal cord injuries (SCI). Using our unique model of SCI-induced NHO, we have previously established that mononucleated phagocytes infiltrating injured muscles are required to trigger NHO via the persistent release of the pro-inflammatory cytokine oncostatin M (OSM). Because neutrophils are also a major source of OSM, we investigated whether neutrophils also play a role in NHO development after SCI. We now show that surgery transiently increased granulocyte colony-stimulating factor (G-CSF) levels in blood of operated mice, and that G-CSF receptor mRNA is expressed in the hamstrings of mice developing NHO. However, mice defective for the G-CSF receptor gene Csf3r, which are neutropenic, have unaltered NHO development after SCI compared to C57BL/6 control mice. Because the administration of recombinant human G-CSF (rhG-CSF) has been trialed after SCI to increase neuroprotection and neuronal regeneration and has been shown to suppress osteoblast function at the endosteum of skeletal bones in human and mice, we investigated the impact of a 7-day rhG-CSF treatment on NHO development. rhG-CSF treatment significantly increased neutrophils in the blood, bone marrow, and injured muscles. However, there was no change in NHO development compared to saline-treated controls. Overall, our results establish that unlike monocytes/macrophages, neutrophils are dispensable for NHO development following SCI, and rhG-CSF treatment post-SCI does not impact NHO development. Therefore, G-CSF treatment to promote neuroregeneration is unlikely to adversely promote or affect NHO development in SCI patients. © 2020 American Society for Bone and Mineral Research.

The Survey of Cells Responsible for Heterotopic Ossification Development in Skeletal Muscles-Human and Mouse Models

Heterotopic ossification (HO) manifests as bone development in the skeletal muscles and surrounding soft tissues. It can be caused by injury, surgery, or may have a genetic background. In each case, its development might differ, and depending on the age, sex, and patient's conditions, it could lead to a more or a less severe outcome. In the case of the injury or surgery provoked ossification development, it could be, to some extent, prevented by treatments. As far as genetic disorders are concerned, such prevention approaches are highly limited. Many lines of evidence point to the inflammatory process and abnormalities in the bone morphogenetic factor signaling pathway as the molecular and cellular backgrounds for HO development. However, the clear targets allowing the design of treatments preventing or lowering HO have not been identified yet. In this review, we summarize current knowledge on HO types, its symptoms, and possible ways of prevention and treatment. We also describe the molecules and cells in which abnormal function could lead to HO development. We emphasize the studies involving animal models of HO as being of great importance for understanding and future designing of the tools to counteract this pathology.

Arthroscopic Excision of Heterotopic Ossification in the Supraspinatus Muscle

Heterotopic ossification is formation of bone in atypical extra-skeletal tissues and usually occurs spontaneously or following neurologic injury with unknown cause. We report a 46-year-old female with right shoulder pain and restricted range of motion (ROM) for 3 months without history of trauma. Magnetic resonance imaging (MRI) showed a lesion within the rotator cuff supraglenoid. Excisional biopsy from a previous institution revealed a heterotopic ossificans (HO ). Following repeat MRI and bone scan, histopathology from arthroscopic resection confirmed an HO. The patient demonstrated improved pain and ROM at follow-up. Idiopathic HO rarely occurs in the shoulder joint, and resection of HO should be delayed until maturation of the lesion to avoid recurrence. The current case showed that arthroscopic HO resection provides an excellent surgical view to ensure complete lesion removal and minimize soft tissue damage at the supraglenoid area. Furthermore, the minimally invasive procedure of arthroscopy may reduce rehabilitation time and facilitate early return to work.

Resection of heterotopic ossification around the hip after trauma

Traumatic neurological lesions may lead to development of heterotopic ossification. These cases are classified as ‘neurogenic heterotopic ossifications’ (NHOs). The associated neurological lesions can be caused by cranial trauma or spinal cord injury and may sometimes include a local trauma.

NHOs that form around the hip joints are of particular interest because they often cause the patient to avoid the sitting position or the resumption of walking.

Whilst NHO can involve the knee, shoulder and elbow joints, hip-involving NHOs are more numerous, and sometimes develop in close contact with vascular or neurological structures.

Multi-disciplinary clinical examination is fundamental to evaluate patients for surgical intervention and to define the objectives of the surgery. The best investigation to define an NHO mass is a computerized tomography (CT) scan.

Resection is performed to liberate a fused joint to provide functionality, and this need not be exhaustive if it is not necessary to increase the range of motion.

While recurrence does occur post-surgery, a partial resection does not pose a greater risk of recurrence and there are no adjuvant treatments available to reduce this risk.

The greatest risks associated with NHO surgical resection are infection and haematoma; these risks are very high and must be considered when evaluating patients for surgery.

Cite this article: EFORT Open Rev 2019;4 DOI: 10.1302/2058-5241.4.180098

Inhibition of JAK1/2 Tyrosine Kinases Reduces Neurogenic Heterotopic Ossification After Spinal Cord Injury

Neurogenic heterotopic ossifications (NHO) are very incapacitating complications of traumatic brain and spinal cord injuries (SCI) which manifest as abnormal formation of bone tissue in periarticular muscles. NHO are debilitating as they cause pain, partial or total joint ankylosis and vascular and nerve compression. NHO pathogenesis is unknown and the only effective treatment remains surgical resection, however once resected, NHO can re-occur. To further understand NHO pathogenesis, we developed the first animal model of NHO following SCI in genetically unmodified mice, which mimics most clinical features of NHO in patients. We have previously shown that the combination of (1) a central nervous system lesion (SCI) and (2) muscular damage (via an intramuscular injection of cardiotoxin) is required for NHO development. Furthermore, macrophages within the injured muscle play a critical role in driving NHO pathogenesis. More recently we demonstrated that macrophage-derived oncostatin M (OSM) is a key mediator of both human and mouse NHO. We now report that inflammatory monocytes infiltrate the injured muscles of SCI mice developing NHO at significantly higher levels compared to mice without SCI. Muscle infiltrating monocytes and neutrophils expressed OSM whereas mouse muscle satellite and interstitial cell expressed the OSM receptor (OSMR). In vitro recombinant mouse OSM induced tyrosine phosphorylation of the transcription factor STAT3, a downstream target of OSMR:gp130 signaling in muscle progenitor cells. As STAT3 is tyrosine phosphorylated by JAK1/2 tyrosine kinases downstream of OSMR:gp130, we demonstrated that the JAK1/2 tyrosine kinase inhibitor ruxolitinib blocked OSM driven STAT3 tyrosine phosphorylation in mouse muscle progenitor cells. We further demonstrated in vivo that STAT3 tyrosine phosphorylation was not only significantly higher but persisted for a longer duration in injured muscles of SCI mice developing NHO compared to mice with muscle injury without SCI. Finally, administration of ruxolitinib for 7 days post-surgery significantly reduced STAT3 phosphorylation in injured muscles in vivo as well as NHO volume at all analyzed time-points up to 3 weeks post-surgery. Our results identify the JAK/STAT3 signaling pathway as a potential therapeutic target to reduce NHO development following SCI.

Clinical Prediction Rule for Heterotopic Ossification of the Hip in Patients with Spinal Cord Injury

STUDY DESIGN

A case-control study; clinical prediction rule.

OBJECTIVE

The aim of this study was to construct and internally validate a clinical prediction rule to identify patients at high risk of developing heterotopic ossification (HO) after spinal cord injury (SCI).

SUMMARY OF BACKGROUND DATA

HO after SCI can lead to loss of joint mobility, loss of function, peripheral nerve entrapment, and pressure sores. HO is usually diagnosed on the basis of clinical symptoms, as no laboratory tests are yet available to identify patients with early HO formation. Risk factors include a complete SCI; patient age; spasticity; urinary tract infection (UTI); pneumonia; pelvic trauma; cervical or thoracic injury; and pressure sores.

METHODS

We analyzed a total of 558 patients with SCI, of whom 221 developed HO of the hip. A parametric survival model was fitted to estimate the probability of developing HO of the hip within 3 months of a SCI. Hazard ratios (HRs) calculation, internal validation, calibration, and model reduction were performed over 200 bootstrapped resamples. A risk score for clinical used was developed.

RESULTS

Risk factors contributing to the risk score were completeness of the injury, age, sex, UTI, spasticity, and pneumonia. The model demonstrated good discrimination (AUC = 0.72). According to the risk score quintiles, the risk of developing HO after SCI was 1.0 for persons with a score of 0 to 17 and increased 2.47-fold for persons with a score of 1 to 21, 4.75-fold for persons with a score of 22 to 27, 6.95-fold for persons with a score of 28 to 31, and 9.23-fold for persons with a score of 32-35.

CONCLUSION

The risk score demonstrated good discrimination in predicting the occurrence of HO within 3 months of a SCI. Further development and validation of the model in other populations is warranted.

LEVEL OF EVIDENCE

3.

Rescue of ankylosing hip following open reduction and internal fixation of acetabular fracture by surgical resection of heterotopic ossification: A case report

•

Heterotopic ossification is a major complication after surgical treatment of acetabular fractures.

•

Whether delayed or early surgical resection of heterotopic ossification is more effective remains controversial.

•

Early surgical resection is not necessarily contraindication.

Introduction

Heterotopic ossification is a major complication after surgical treatment of acetabular fractures. Heterotopic ossification generally involves the large joints, often limits the range of motion, and may cause ankylosis.

Presentation of case

This case report describes a 59-year-old man with severe heterotopic ossification who developed an acetabular fracture and resultant hip ankylosis, which was rescued by surgical resection of the heterotopic ossification. He had accompanying head injury and multiple other fractures, which were treated conservatively. Open reduction with internal fixation of the acetabular fracture was performed through the ilioinguinal and Kocher–Langenbeck combined approach. The patient unexpectedly returned to our hospital 7.5 months after the fracture surgery. We found that his left hip joint was completely ankylosed by severe heterotopic ossification. We performed surgical resection of the heterotopic ossification through a direct lateral approach 9.5 months after the initial surgery. At the final follow-up, 5.5 years after the heterotopic ossification resection surgery, the hip function including the range of motion was satisfactory. Radiographs showed no signs of recurrence, and he could walk with no support.

Discussion

The only effective treatment for established HO is surgical excision. Whether delayed or early surgical resection of heterotopic ossification is more effective remains controversial.

Conclusion

We considered that waiting for a long time before surgical resection of the heterotopic ossification would lead to more disability, and early resection of the heterotopic ossification was not a contraindication despite the fact that the uptake on the bone scan was still intense.

Postinfectious heterotopic ossification of the ilium involving the iliacus muscle

Heterotopic ossification in soft tissue or muscle is rare in the pediatric and adolescent age group. Most cases are associated with musculoskeletal injury and trauma to the central nervous system. Here, we describe an adolescent patient without a history of trauma or lesions in the central nervous system who presented with a painful limp with limited motion of the left hip. Investigations indicated unusually large heterotopic ossification extending from the inner aspect of the ilium down to the anterior part of the hip, highly likely to have developed after an unrecognized periacetabular pyomyositis primarily involving the iliacus muscle. Surgical excision was performed successfully without perioperative complications. No recurrence was detected at the final follow-up.

Ankylosing Neurogenic Myositis Ossificans of the Hip: A Case Series and Review of Literature

Purpose

Neurogenic myositis ossificans (NMO) in patients with traumatic spinal cord or brain injuries can cause severe joint ankylosis or compromise neurovascularture. The purpose of this study was to evaluate the clinical and radiological outcomes of and review considerations relevant to surgical resection of NMO of the hip joint.

Materials and Methods

Six patients (9 hips) underwent periarticular NMO resection between 2015 and 2017. The medical records of these patients were retrospectively reviewed. Preoperative computed tomography including angiography was performed to determine osteoma location and size. Improvement in hip motion allowing sitting was considered the sole indicator of a successful surgery. The anterior approach was used in all patients. The ranges of motion (ROM) before and after surgery were compared.

Results

The mean time from accident to surgery was 3.6 years. Average ROM improved from 24.3°(flexion and extension) to 98.5°(flexion and extension) after surgery, and improvement was maintained at the last follow-up. No commom complications (e.g., deep infection, severe hematoma, deep vein thrombosis) occurred in any patient. Improvement in ROM in one hip in which surgical resection was performed 10 years after the accident was not satisfactory owing to the pathologic changes in the joint.

Conclusion

Surgical excision of periarticular NMO of the hip joint can yield satisfactory results, provided that appropriate preoperative evaluation is performed. Early surgical intervention yields satisfactory results and may prevent the development of intra-articular pathology.

Neurological heterotopic ossification: Current understanding and future directions

Neurological heterotopic ossification (NHO) involves the formation of bone in soft tissue following a neurological condition, of which the most common are brain and spinal cord injuries. NHO often forms around the hip, knee and shoulder joints, causing severe pain and joint deformation which is associated with significant morbidity and reduced quality of life. The cellular and molecular events that initiate NHO have been the focus of an increasing number of human and animal studies over the past decade, with this work largely driven by the need to unearth potential therapeutic interventions to prevent the formation of NHO. This review provides an overview of the present understanding of NHO pathogenesis and pathobiology, current treatments, novel therapeutic targets, potential biomarkers and future directions.

Surgical treatment of hip ankylosis due to heterotopic ossification secondary to spinal cord injury

OBJECTIVES

To expose our experience in the diagnostic and surgical treatment of neurogenic heterotopic ossification of the hip.

MATERIAL AND METHODS

We designed an observational retrospective descriptive study including 20 patients (30 hips) with neurogenic heterotopic ossification of the hip secondary to spinal cord injury attended in our institution in the last 10 years, with a minimum of one year follow-up. Medical files and imaging studies were reviewed. The study variables analyzed were: type and localization of neurogenic heterotopic ossification, pre-post excision range of motion, level and aetiology of spinal cord injury, ASIA score, smoking history, surgical approach and complications associated with surgery.

RESULTS

A total of 20 patients were treated with resection of heterotopic ossification in 30 hips. 16 patients presented ASIA A spinal cord injury and 4 ASIA B spinal cord injury. Preoperatively all the patients had severe ankylosis in the hip that made sitting in a wheel chair and activities such as repositioning and hygiene difficult. The average postoperative motion at the follow-up evaluation was 90° in flexion, 20° of internal rotation and 40° of external rotation. Immediately after surgery all the patients followed a specific intensive physiotherapy regime for the hip and celecoxib 200 mg was administrated daily orally for a month to prevent recurrence of heterotopic bone formation. None of the patients reviewed suffered a recurrence of heterotopic bone formation.

CONCLUSIONS

Surgical excision of hip ossification in order to achieve functional ROM of the hip is the best treatment for patients with neurogenic heterotopic ossification of the hip.

Resection of neurogenic heterotopic ossification (NHO) of the hip

Neurogenic heterotopic ossification of the hip is secondary to neurologic lesions such as cranial trauma, stroke, medullary injury or cerebral anoxia. We shall not deal here with the other etiologies of heterotopic ossification. There are numerous locations within the hip, depending on etiology and relations with adjacent neurovascular structures are sometimes close. Preoperative work-up should include contrast-enhanced CT; scintigraphy is non-contributive. Indications for surgery are decided in a multidisciplinary team meeting, with a contract laying out expected functional gain. It is this contract that determines the extent of resection, without seeking complete resection, which would incur an increased risk of complications. The surgical approach and resection strategy depend on lesion location and any resulting neurovascular compression. The most common complications are infection and postoperative hematoma. No adjuvant treatments have demonstrated efficacy against recurrence.

Peripheral denervation participates in heterotopic ossification in a spinal cord injury model

We previously reported the development of a new acquired neurogenic HO (NHO) mouse model, combining spinal cord transection (SCI) and chemical muscle injury. Pathological mechanisms responsible for ectopic osteogenesis after central neurological damage are still to be elucidated. In this study, we first hypothesized that peripheral nervous system (PNS) might convey pathological signals from injured spinal cord to muscles in NHO mouse model. Secondly, we sought to determine whether SCI could lead to intramuscular modifications of BMP2 signaling pathways. Twenty one C57Bl6 mice were included in this protocol. Bilateral cardiotoxin (CTX) injection in hamstring muscles was associated with a two-stage surgical procedure, combining thoracic SCI with unilateral peripheral denervation. Volumes of HO (Bone Volume, BV) were measured 28 days after surgery using micro-computed tomography imaging techniques and histological analyses were made to confirm intramuscular osteogenesis. Volume comparisons were conducted between right and left hind limb of each animal, using a Wilcoxon signed rank test. Quantitative polymerase chain reaction (qPCR) was performed to explore intra muscular expression of BMP2, Alk3 and Id1. Nineteen mice survive the complete SCI and peripheral denervation procedure. When CTX injections were done right after surgery (n = 7), bilateral HO were detected in all animals after 28 days. Micro-CT measurements showed significantly increased BV in denervated paws (1.47 mm3 +/- 0.5) compared to contralateral sides (0.56 mm3 +/-0.4), p = 0.03. When peripheral denervation and CTX injections were performed after sham SCI surgery (n = 6), bilateral HO were present in three mice at day 28. Quantitative PCR analyses showed no changes in intra muscular BMP2 expression after SCI as compared to control mice (shamSCI). Peripheral denervation can be reliably added to spinal cord transection in NHO mouse model. This new experimental design confirms that neuro inflammatory mechanisms induced by central or peripheral nervous system injury plays a key role in triggering ectopic osteogenesis.

Results from the surgical resection of severe heterotopic ossification of the hip: a case series of 26 patients

INTRODUCTION

Surgical resection of heterotopic ossification (HO) around the hip joint is often challenging. The aim of this study is to evaluate the clinical and radiological outcomes following surgical resection of Brooker's type III and IV HO of the hip.

METHODS

We retrospectively reviewed clinical and radiological data, between November 2006 and January 2013, of all patients who underwent surgical resection of severe HO of the hip. Brooker's grading, range of motion and the Harris Hip Score before and after surgery were recorded in all cases. The combined radiation (700 cGy preoperatively) and indomethacin regimen was used to prevent heterotopic ossification recurrence.

RESULTS

Twenty-six patients (22 males and 4 females) were included in our study. Mean patient age was 47.38 years (range 24-72). The HO was graded as Brooker grade III in 3 patients (11.5%) and Brooker grade IV in 23 patients (88.5%). Mean time interval between HO development and resection was 40.8 months (range 13-156 months). All patients had CT scans prior to surgery. Mean follow-up was 31.4 months (range 24-40 months). There was no severe HO recurrence. Complications included one intraoperative injury of a femoral artery branch, one intraoperative femoral neck fracture treated with intramedullary nailing, one sciatic nerve injury and one superficial infection treated conservatively.

CONCLUSIONS

Surgical resection of severe HO of the hip along with preoperative radiation and indomethacin provides excellent results; however, the complication rate is relatively high. Careful evaluation of the preoperative CT scan and wide exposure are required in order to identify all the involved neurovascular structures.

Nyka W. Neurogenic heterotopic ossifi cation – case study

The authors presented the case of a 30-year-old man in whom sudden cardiac arrest occurred as a result of high voltage electric shock. Starting from the 2nd week after the accident, rehabilitation was carried out in hospital conditions, designed to maintain range of motion in the joints, and from the 6th week, intensive rehabilitation was performed at the patient’s home. Despite the implemented treatment, total mobility restriction was observed in the hip joints, and based on spatial projection radiography and a CT, the patient was diagnosed with massive neurogenic heterotopic ossifi cation (NHO). Two surgeries were performed to remove the NHO: fi rst, from the left area (15th month after the accident), and then the right hip joint (18th month following the accident). After the intervention there was a signifi cant increase in mobility of both hips and a decrease in pain, which resulted in signifi cantly improved functional capabilities of the patient. In addition, prophylaxis to prevent the recurrence of NHO was implemented in order to maintain both passive and active range of motion, and the use of physical therapy treatments in the form of deep oscillation were performed. The results of the CT conducted in the 41st month following the accident revealed lesser NHO than the originally diagnosed. Rolka Ł., Browiński D., Kwiatek-Rolka K., Sielska M., Sielski G., Nyka W.M. Neurogenic heterotopic ossification – case study. Med Rehabil 2016; 20(4): 22-27. DOI: 10.5604/01.3001.0009.5482

Recurrence of heterotopic ossification after removal in patients with traumatic brain injury: A systematic review

OBJECTIVE

A systematic review of the literature to determine whether in patients with neurological heterotopic ossification (NHO) after traumatic brain injury, the extent of the neurological sequelae, the timing of surgery and the extent of the initial NHO affect the risk of NHO recurrence.

DATA SOURCES

We searched MEDLINE via PubMed and Cochrane library for articles published up to June 2015. Results were compared with epidemiological studies using data from the BANKHO database of 357 patients with central nervous system (CNS) lesions who underwent 539 interventions for troublesome HO.

RESULTS

A large number of studies were published in the 1980s and 1990s, most showing poor quality despite being performed by experienced surgical teams. Accordingly, results were contradictory and practices heterogeneous. Results with the BANKHO data showed troublesome NHO recurrence not associated with aetiology, sex, age at time of CNS lesion, multisite HO, or "early" surgery (before 6months). Equally, recurrence was not associated with neurological sequelae or disease extent around the joint.

CONCLUSIONS

The recurrence of NHO is not affected by delayed surgery, neurological sequelae or disease extent around the joint. Surgical excision of NHO should be performed as soon as comorbid factors are under control and the NHO is sufficiently constituted for excision.

Link Between Clinical Predictors of Heterotopic Ossification and Histological Analysis in Combat-Injured Service Members

BACKGROUND

Heterotopic ossification (HO) is a debilitating condition that occurs following traumatic injury and may restrict range of motion and delay rehabilitation. The timing and efficacy of surgical resection have varied widely, and there is a gap in knowledge between clinical predictors of HO recurrence and histological analysis.

METHODS

Thirty-three service members seen at Walter Reed National Military Medical Center for symptomatic HO were enrolled in an institutional review board-approved study. Participants took oxytetracycline on four scheduled days prior to HO resection to determine the mineral apposition rate (bone growth rate).

RESULTS

Detailed histological analyses included scanning electron microscopy with backscattered electron imaging and light microscopy. Data indicated that the mineral apposition rate of trauma-induced HO was approximately 1.7 μm/day at the time of operative intervention, which was 1.7 times higher than the rate in non-pathological human bone. The mineral apposition rate and postoperative alkaline phosphatase values were demonstrated to be positively and significantly related (ρ = 0.509, p = 0.026, n = 19). When the analysis was limited to patients with no more than a two-year period from injury to excision (thereby removing outliers who had a longer time period than their counterparts) and traumatic brain injury and nonsteroidal anti-inflammatory drugs (known correlates with HO development) were controlled for in the statistical analysis, the mineral apposition rate and recurrence severity were significantly related (ρ = -0.572, p = 0.041, n = 11).

CONCLUSIONS

Data demonstrated a link between benchtop research and bedside care, with the mineral apposition rate elevated in patients with HO and correlated with recurrence severity; however, a larger sample size and more clinical factors are needed to refine this model.

LEVEL OF EVIDENCE

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

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.

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

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

Heterotopic ossification of the shoulder after central nervous system lesion: indications for surgery and results

BACKGROUND

Heterotopic ossification (HO) of the shoulder after central nervous system damage has seldom been studied.

MATERIALS AND METHODS

We performed a single-center retrospective study from 1993 to 2009 including patients who underwent surgery for troublesome shoulder HO. Demographic data, HO location, surgical approach, preoperative and postoperative shoulder range of motion, etiologies, and postoperative complications were collected from patients' files.

RESULTS

We found 19 shoulder HOs in 16 patients (traumatic brain injury in 11, spinal cord injury in 2, stroke in 1, and cerebral anoxia in 2). The data in 2 files were incomplete and were therefore not used. HO locations around the joint were anteroinferomedial in 4 (21.1%), posteroinferomedial in 5 (26.3%), encircling in 3 (15.8%), superior in 1 (5.3%), and mixed (2 associated HOs that are not encircling) in 6 (31.6%). The surgical approaches were as follows: deltopectoral, 5 (26.3%); Neer, 3 (15.8%); posterior, 5 (26.3%); axillary, 1 (5.3%); Martini, 2 (10.5%); posterior associated with deltopectoral, 2 (10.5%); and Neer (superolateral) associated with deltopectoral, 1 (5.3%). The mean range of motion increased significantly (gain at follow-up of 69°, 60°, and 13° in forward elevation, abduction, and lateral rotation, respectively). Regarding postoperative complications, there was 1 case of capsulitis and 1 reoperation for insufficient excision (because of hemorrhage during surgery). There were no other side effects.

CONCLUSION

Anatomic relations with nerves and vessels, as well as limited range of motion, require a case-by-case surgical approach, a preoperative scan (looking for a gutter), and sometimes, electromyography. Surgical indications depend on the degree of loss of function or hygiene, control of comorbid factors, and discussion with the patient and his or her family.

Heterotopic ossification after central nervous system trauma: A current review

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

Surgical excision of heterotopic ossification of hip in a rare case of Moyamoya disease with extra articular ankylosis

We report a case of isolated ossification of iliopsoas with ankylosis of the left hip in a 27-year-old female. The patient was diagnosed to have Moyamoya disease, a rare chronic occlusive disorder of cerebrovascular circulation following an acute onset of hemiplegia. The patient presented 9 months later to us with ankylosis of left hip which was successfully treated by surgical excision of the heterotopic bone and there was no recurrence at the end of 5 years. A review of literature failed to reveal a similar case with isolated and complete ossification of iliopsoas muscle associated with Moyamoya disease which required surgical intervention. Surgical excision resulted in dramatic improvement in the quality of life. Surgical excision of neurogenic type of heterotopic ossification is a very successful procedure and timely intervention after maturity of mass is very important to prevent the onset of secondary complications and to avoid recurrence.

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

Background

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

Methodology/Principal Findings

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

Conclusions/Significance

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

Animal models of typical heterotopic ossification

Heterotopic ossification (HO) is the formation of marrow-containing bone outside of the normal skeleton. Acquired HO following traumatic events is a common and costly clinical complication. In contrast, hereditary HO is rarer, progressive, and life-threatening. Substantial effort has been directed towards understanding the mechanisms underlying HO and finding efficient treatments. However, one crucial limiting factor has been the lack of relevant animal models. This article reviews the major currently available animal models, summarizes some of the insights gained from these studies, and discusses the potential future challenges and directions in HO research.

Heterotopic ossification following cardiac arrest and hypoxic brain damage

Aims

Heterotopic bone can cause restriction of movement when deposited in the soft tissues around joints. Neurogenic heterotopic ossification may follow brain injury. This article describes research into the incidence of heterotopic ossification after brain injury, and its impact on rehabilitation.

Methods

Thirty-nine patients who were admitted to the rehabilitation unit of University Hospital Bydgoszcz, Poland, after hypoxic brain injury due to cardiac arrest, were examined.

Findings

Six patients were identified as having developed heterotopic bone around one or more joints causing limitation of movement and delay in the rehabilitation process.

Conclusions

Heterotopic ossification occurs in up to 15% of patients following hypoxic brain injury. The development of the condition may often be missed clinically, and can hinder rehabilitation.