Magnetic resonance signal alterations in the acute onset of heterotopic ossification in patients with spinal cord injury

Early diagnosis of heterotopic ossification with a NIR fluorescent probe by targeting type II collagen

Heterotopic ossification (HO) is a devastating sequela in which the pathologic extracellular matrix of the cartilage and bone forms abnormally in soft tissues following traumatic injuries or orthopaedic surgeries. Early treatment is essential for inhibiting the progression of HO but is currently limited by the absence of sensitive and specific early diagnosis. Herein, this study exploits the enrichment of type II collagen (Col2a1) in the HO cartilage formation stage towards developing a near-infrared (NIR) probe for early HO diagnosis, namely WL-808 by conjugating a Col2a1-binding peptide (WYRGRL) and a cyanine dye (IR-808). WL-808 exhibits high specificity for targeting the cartilage in vitro and in vivo with no apparent cytotoxicity. The NIR signal of WL-808 can be detected in the HO cartilage lesions as early as 1 week after injury when micro-CT cannot show any ectopic bone formation. Moreover, the probe is rarely distributed in the normal knee articular cartilage in vivo via the intravenous administration method. Taken together, WL-808 demonstrates great potential in early HO diagnosis under NIR imaging, facilitating early HO prophylaxis and treatment in the clinic.

Impact of Heterotopic Ossification on Functional Recovery in Acute Spinal Cord Injury

Objective: In spinal cord injury (SCI), heterotopic ossification is a frequent secondary complication, commonly associated with limited range of motion of affected joints, which could lead to secondary disability in activities of daily living. Additionally, heterotopic ossifications might challenge the effect of regeneration-promoting therapies on neurological and functional recovery. This study evaluated the impact of heterotopic ossification on clinical recovery within the first year after SCI.

Methods: The study was conducted as a monocentric longitudinal paired cohort study. Recruitment was based on consecutive sampling in the framework of the European Multicenter about Spinal Cord Injury (EMSCI). Recovery profiles were determined using standardized neurological and functional clinical assessments within the 1st year following SCI. All study participants underwent at least two comprehensive standardized neurological and functional clinical examinations according to the International Standards for Neurological Classification of SCI and the Spinal Cord Independence Measure, respectively. Data regarding the diagnosis and treatment of heterotopic ossification were obtained by reviewing the patient medical records. The most similar “digital twin” from the entire EMSCI database were matched in terms of age, acute neurological and functional status to each individual with SCI, and heterotopic ossification.

Results: Out of 25 participants diagnosed with heterotopic ossification, 13 individuals were enrolled and matched to control individuals. Most individuals presented with motor complete injury (75%). Ossifications were most frequently located at the hip joints (92%) and mainly occurred within the first 3 months after SCI. Individuals with heterotopic ossification achieved around 40% less functional improvement over time compared to their matched counterparts, whereas neurological recovery was not altered in individuals with SCI and heterotopic ossification.

Conclusion: Heterotopic ossification—a common complication of SCI—unfavorably affects functional recovery, which in the end is most relevant for the best possible degree of independence in activities of daily living. Upon presentation with heterotopic ossification, neurological improvement achieved through potential restorative therapies might not translate into clinically meaningful functional improvement. Diagnostic algorithms and effective early prevention/treatment options for heterotopic ossification need to be established to ensure the best possible functional outcome.

Clinical Trial Registration: NCT01571531 (https://clinicaltrials.gov).

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.

Pelvic MRI in spinal cord injury patients: incidence of muscle signal change and early heterotopic ossification

STUDY DESIGN

Prospective observational study.

OBJECTIVE

To evaluate pelvic MRI muscle signal changes and their association with early heterotopic ossification (HO) in patients with spinal cord injuries.

SETTING

National Spinal Injuries Unit, Stoke Mandeville, UK.

METHODS

Forty patients were imaged with at least two interval magnetic resonance (MR) studies of the pelvis in the first 6 months following a spinal cord injury. Scans were reviewed and scored for heterotopic ossification, muscle signal change and extent of muscle involvement.

RESULTS

Muscle signal change was present in 28 (70%) on the initial MRI and 31 (77%) by the second study. Six patients developed MR changes of prodromal or immature heterotopic ossification (15%). No restricted diffusion was demonstrated and no patient developed mature HO. Patients developing MR changes of early HO were more likely to have grade 3 muscle changes.

CONCLUSION

Increased T2 muscle signal is common following cord injury, is frequently progressive in the subacute period and is associated with complete injury and early MR signs of heterotopic ossification.

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.

The traumatic bone: trauma-induced heterotopic ossification

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

Bedside, Benchtop, and Bioengineering: Physicochemical Imaging Techniques in Biomineralization

The need to quantify physicochemical properties of mineralization spans many fields. Clinicians, mineralization researchers, and bone tissue bioengineers need to be able to measure the distribution, quantity, and the mechanical and chemical properties of mineralization within a wide variety of substrates from injured muscle to electrospun polymer scaffolds and everything in between. The techniques available to measure these properties are highly diverse in terms of their complexity and utility. Therefore it is of the utmost importance that those who intend to use them have a clear understanding of the advantages and disadvantages of each technique and its appropriateness to their specific application. This review provides all of this information for each technique and uses heterotopic ossification and engineered bone substitutes as examples to illustrate how these techniques have been applied. In addition, we provide novel data using advanced techniques to analyze human samples of combat related heterotopic ossification.

Identifying the Cellular Mechanisms Leading to Heterotopic Ossification

Heterotopic ossification (HO) is a debilitating condition defined by the de novo development of bone within non-osseous soft tissues, and can be either hereditary or acquired. The hereditary condition, fibrodysplasia ossificans progressiva is rare but life threatening. Acquired HO is more common and results from a severe trauma that produces an environment conducive for the formation of ectopic endochondral bone. Despite continued efforts to identify the cellular and molecular events that lead to HO, the mechanisms of pathogenesis remain elusive. It has been proposed that the formation of ectopic bone requires an osteochondrogenic cell type, the presence of inductive agent(s) and a permissive local environment. To date several lineage-tracing studies have identified potential contributory populations. However, difficulties identifying cells in vivo based on the limitations of phenotypic markers, along with the absence of established in vitro HO models have made the results difficult to interpret. The purpose of this review is to critically evaluate current literature within the field in an attempt identify the cellular mechanisms required for ectopic bone formation. The major aim is to collate all current data on cell populations that have been shown to possess an osteochondrogenic potential and identify environmental conditions that may contribute to a permissive local environment. This review outlines the pathology of endochondral ossification, which is important for the development of potential HO therapies and to further our understanding of the mechanisms governing 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.

Early detection of heterotopic ossification using near-infrared optical imaging reveals dynamic turnover and progression of mineralization following Achilles tenotomy and burn injury

Heterotopic ossification (HO) is the abnormal formation of bone in soft tissue. Current diagnostics have low sensitivity or specificity to incremental progression of mineralization, especially at early time points. Without accurate and reliable early diagnosis and intervention, HO progression often results in incapacitating conditions of limited range of motion, nerve entrapment, and pain. We hypothesized that non-invasive near-infrared (NIR) optical imaging can detect HO at early time points and monitor heterotopic bone turnover longitudinally. C57BL6 mice received an Achilles tenotomy on their left hind limb in combination with a dorsal burn or sham procedure. A calcium-chelating tetracycline derivative (IRDye 680RD BoneTag) was injected bi-weekly and imaged via NIR to measure accumulative fluorescence for 11 wk and compared to in vivo microCT images. Percent retention of fluorescence was calculated longitudinally to assess temporal bone resorption. NIR detected HO as early as five days and revealed a temporal response in HO formation and turnover. MicroCT could not detect HO until 5 wk. Confocal microscopy confirmed fluorophore localization to areas of HO. These findings demonstrate the ability of a near-infrared optical imaging strategy to accurately and reliably detect and monitor HO in a murine model.

Musculoskeletal pitfalls and pseudotumours in the pelvis: a pictorial review for body imagers

Many musculoskeletal abnormalities in the pelvis are first seen by body imagers while reviewing pelvic cross-sectional studies, and some of these abnormalities may mimic malignancy or another aggressive process. This article describes nine musculoskeletal pseudotumours and interpretative pitfalls that may be seen on CT, MRI and ultrasound imaging of the pelvis. Awareness of these pitfalls and pseudotumours may help avoid misdiagnosis and prevent inappropriate intervention or management.

The use of spect/ct in the evaluation of heterotopic ossification in para/tetraplegics

Objective:

To evaluate the stage of maturation and the metabolism of neurogenic heterotopic ossification by using SPECT/CT.

Methods:

A total of 12 medical records of patients with spinal cord injury, all of them classified according to the ASIA protocol (disability scale from the American Spinal Injury Association) in complete lesion (A) and partial lesions (B, C and D) and registered at the Laboratory of Biomechanics and Rehabilitation of the Locomotor System, were submitted to SPECT/CT evaluation.

Results:

Sixteen hips with heterotopic ossification observed in X-ray were studied and only two (12.5%) had high osteoblastic activity. Five hips showed medium activity, three (18.75%) low activity and six (37.5%) did not present any activity detected by SPECT/CT.

Conclusion:

SPECT/CT helps to determinate which patients have a greater risk of relapse after surgical resection, proving to be a useful imaging study in preoperative evaluation that can be used to determinate the postoperative prognosis of these patients. Level of Evidence III, Investigating a Diagnostic Test.

Pelvic heterotopic ossification: when CT comes to the aid of MR imaging

Objective

This article compares various imaging aspects of magnetic resonance (MR) and computed tomography (CT) of heterotopic ossification (HO) in the pelvic soft tissues in paraplegic patients. Our aim is to highlight the benefits of integrating MR and CT imaging in the diagnosis of immature HO, which may be challenging with MR images alone.

Methods

Paraplegic patients examined on the same day by contrast-enhanced 0.4-T pelvic MR and unenhanced CT for pressure-sore-related infections were selected. MR imaging was performed on a Hitachi-Aperto 0.4 T; the Open Magnet served as a more favourable configuration for the required limb positioning of these patients. CT images were attained on a six-slice Siemens-Somaton-Emotion.

Results

MR images of HO differ according to the degree of bone maturity. The more immature the HO process, the more heterogeneous is the signal, characterised mostly by focal iso-hypointensity on T1-weighted images and hyperintensity on T2-weighted/short TI inversion recovery (STIR). These characteristics correlate to different CT patterns.

Conclusions

MR and CT features of pelvic HO in paralysed patients were reviewed with a focus on the different aspects associated with the degree of ossification. Based solely on the MR findings, immature heterotopic ossification may be difficult to differentiate from other soft tissue pelvic lesions.

Teaching points

• The pelvis and hip are common locations of heterotopic ossifications (HO), often occurring in paraplegic patients.

• With respect to HO, MR imaging allows for a confident diagnosis in mature ossified lesions only. The MR aspect of immature ossification may be confused with other pathologies.

• Plain radiographs and CT may show various phases of ossification: amorphous calcification, immature and mature ossification.

• Integrating MR with CT can help recognise HO foci and differentiate them from infections and other soft tissue lesions.

Early presentation of heterotopic ossification mimicking pyomyositis - two case reports -

Early diagnosis and treatment of heterotopic ossification (HO) is essential to the prevention of complications. It is difficult to diagnose HO in its initial phase because non-specific clinical manifestations, laboratory findings and imaging findings of immature HO may mimic other diseases such as cellulitis, osteomyelitis, thrombophlebitis, deep vein thrombosis and local infection with abscess. We experienced two cases of HO, which were misdiagnosed as pyomyositis at first by clinical signs and MRI findings indicating the deep infection; the extensive intramuscular ossification appeared later on. We observed an increase of C-reactive protein and creatine kinase followed by the elevation of alkaline phosphatase with abnormal triphasic bone scan. The trajectory of these biomarkers was analyzed to get more insight into the early stages of HO along with the imaging findings. Although our cases cannot be generalized as typical of immature HO, they clearly demonstrate that the change of specific biomarkers with a careful history taking and physical examination should be noted to detect HO as early as possible while avoiding confusion with other mimicking conditions.

The changing landscape of spinal cord injury

In the past quarter century, spinal cord injury medicine has welcomed the proliferation of new medications and technologies that improve the survival and quality of life for people with spinal cord injury, but also endured the failure of strategies we hoped would salvage the cord in the acute phase. Surgical decompression and spinal stabilization should be pursued whenever indicated and feasible; however, there is no compelling evidence that early decompression facilitates neurological improvement. Methylprednisolone, the subject of over two decades of trials, has proven to be of marginal benefit in improving functional outcome. Recent advances in the management of the respiratory, cardiovascular, autonomic, endocrine, skeletal and integumentary systems have not only changed morbidity and survival of spinal cord injury patients but also improved quality of life. Progress has been made in the early diagnosis and effective treatment of cardiac arrhythmias, neurogenic shock, autonomic dysreflexia and orthostatic hypotension. Aggressive respiratory care for high cervical level of injury patients should include an option for phrenic nerve pacing as it is a viable rehabilitative strategy for appropriately selected patients. Pressure ulcers remain a significant psychological, financial, and functional burden for many people with SCI and for healthcare providers. This area will continue to require further work on early prevention and education. Despite extensive scientific and clinical data on neurogenic osteoporosis, there is no consensus regarding the best pharmacotherapeutic agents, dosing regimens, or rehabilitative strategies for prevention and treatment of bone loss. This chapter will focus on the advances.

BMP-9-induced muscle heterotopic ossification requires changes to the skeletal muscle microenvironment

Heterotopic ossification (HO) is defined as the formation of bone inside soft tissue. Symptoms include joint stiffness, swelling, and pain. Apart from the inherited form, the common traumatic form generally occurs at sites of injury in damaged muscles and is often associated with brain injury. We investigated bone morphogenetic protein 9 (BMP-9), which possesses a strong osteoinductive capacity, for its involvement in muscle HO physiopathology. We found that BMP-9 had an osteoinductive influence on mouse muscle resident stromal cells by increasing their alkaline phosphatase activity and bone-specific marker expression. Interestingly, BMP-9 induced HO only in damaged muscle, whereas BMP-2 promoted HO in skeletal muscle regardless of its state. The addition of the soluble form of the ALK1 protein (the BMP-9 receptor) significantly inhibited the osteoinductive potential of BMP-9 in cells and HO in damaged muscles. BMP-9 thus should be considered a candidate for involvement in HO physiopathology, with its activity depending on the skeletal muscle microenvironment.

[Imaging features of neurologic and orthopedic complications from severe trauma]

Cranial and spinal trauma are a frequent cause of disability in the general population. Post-traumatic paraplegia or quadriplegia or hemiplegia from vascular injury (CVA) can lead to early complications (respiratory, cardiovascular, urinary, cutaneous, infectious...) that may have an impact on the immediate prognosis. Neurologic and orthopedic complications occur later and further impair the quality of life of patients. Orthopedic complications include: neurogenic paraosteoarthropathy (NPOA) or neurogenic osteoma or myositis ossificans (NMO). The nomenclature currently in use is NMO; Osseous complications: osteoporosis and secondary insufficiency fractures; Joint complications: degenerative arthropathy and stiffness; Overuse mechanical complications; Muscular complications; Infectious complications: arthritis and myositis complicating skin ulcers and bed sores. The purpose of this paper is to describe these neuro-orthopedic complications and review their imaging features.

Sonographic diagnosis of neurogenic heterotopic ossification in patients with severe acquired brain injury in a neurorehabilitation unit

PURPOSE

To illustrate the ultrasonographic (US) and power Doppler US (PDUS) features of neurogenic heterotopic ossification (NHO) in consecutive patients with severe acquired brain injury and to evaluate the role of bedside US in diagnosis of NHO.

METHODS

Ninety-two consecutive patients with severe acquired brain injury underwent clinical and laboratory screening for NHO. In 6 of 92 patients, bedside US confirmed the clinical suspicion of NHO. US diagnosis of NHO was then confirmed by other imaging methods.

RESULTS

The incidence of clinical NHO was 7% (9/92) with one patient having multifocal involvement. In NHO of the hip, US demonstrated the classic pattern of zone phenomenon, and PDUS demonstrated vascular signal within mineralized NHO and in outer hypoechoic area. No vascular signal was observed in the central hypoechoic core. In NHO of the knee, a heterogeneously hypoechoic mass was seen and in the elbow a hyperechoic mineralized mass was visualized, with vascular signals seen within the lesions. Spectral wave analysis demonstrated low resistance vessels in NHO.

CONCLUSIONS

Bedside US is a useful tool in the diagnosis of NHO. PDUS adds data regarding neoangiogenetic activity of NHO.

Bedside ultrasound in early diagnosis of neurogenic heterotopic ossification in patients with acquired brain injury

OBJECTIVE

To illustrate ultrasound (US) and power Doppler US (PDUS) aspects of neurogenic heterotopic ossification (NHO) in consecutive patients with severe acquired brain injury, to evaluate the role of bedside US and PDUS in early diagnosis of NHO, to study incidence and outcome of NHO in this neurorehabilitative setting.

METHODS

Ninety-two consecutive patients with severe acquired brain injury underwent clinical and laboratory screening to pose suspect of NHO. In 6/92 patients bedside US examination confirmed the clinical suspect of NHO. US diagnosis of NHO was then confirmed by other imaging methods. All affected patients started therapy with indometacin, disodium etidronate, 6-methylprednisolone and they were followed-up for 1 year to evaluate the outcome.

RESULTS

The incidence of NHO in this setting was 6.5% (only one patient with multifocal involvement). In hip NHO US demonstrated the classical pattern of zone phenomenon, and PDUS demonstrated vascular signals within mineralized NHO and in the outer hypoechoic area. No vascular signal was observed in the central hypoechoic core. In knee and elbow NHO only a heterogeneously hypoechoic mass or hyperechoic mineralized mass were respectively evident, with vascular signals within the lesions at PDUS. Spectral wave analysis (SWA) demonstrated low resistance vessels in NHO. After 1 year of therapy only one patient showed a severe ankylosis of the hips.

CONCLUSIONS

Bedside US is a safe, cheap and useful tool in diagnosis of NHO and it allows to start therapy in early stages of NHO formation. PDUS adds data about neoangiogenetic activity of early NHO.

Heterotopic ossification of the knee joint in intensive care unit patients: early diagnosis with magnetic resonance imaging

INTRODUCTION

Heterotopic ossification (HO) is the formation of bone in soft tissues. The purpose of the present study was to evaluate the magnetic resonance imaging (MRI) findings on clinical suspicion of HO in the knee joint of patients hospitalised in the intensive care unit (ICU).

METHODS

This was a case series of 11 patients requiring prolonged ventilation in the ICU who had the following diagnoses: head trauma (nine), necrotising pancreatitis (one), and fat embolism (one). On clinical suspicion of HO, x-rays and MRI of the knee joint were performed. Follow-up x-rays and MRI were also performed.

RESULTS

First x-rays were negative, whereas MRI (20.2 +/- 6.6 days after admission) showed joint effusion and in fast spin-echo short time inversion-recovery (STIR) images a 'lacy pattern' of the muscles vastus lateralis and medialis. The innermost part of the vastus medialis exhibited homogeneous high signal. Contrast-enhanced fat-suppressed T1-weighted images also showed a 'lacy pattern.' On follow-up (41.4 +/- 6.6 days after admission), STIR and contrast-enhanced T1-weighted images depicted heterogeneous high signal and heterogeneous enhancement, respectively, at the innermost part of the vastus medialis, whereas x-rays revealed a calcified mass in the same position. Overall, positive MRI findings appeared simultaneously with clinical signs (1.4 +/- 1.2 days following clinical diagnosis) whereas x-ray diagnosis was evident at 23 +/- 4.3 days (p = 0.002).

CONCLUSION

MRI of the knee performed on clinical suspicion shows a distinct imaging pattern confirming the diagnosis of HO earlier than other methods. MRI diagnosis may have implications for early intervention in the development of HO.

Popliteus muscle sesamoid bone (cyamella): appearance on radiographs, CT and MRI

Popliteus muscle sesamoid bone, also known as cyamella, is an accessory ossicle that is located in the vicinity of the proximal musculo tendinous junction. While commonly seen in small mammals such as cats and dogs, its presence in humans is very rare. In this report, we present the radiological findings of the popliteus muscle sesamoid bone, incidentally detected in a 47-year-old male. CT and MRI features of this ossicle are described.