MRI CHARACTERISTICS AND HISTOLOGY OF BONE MARROW LESIONS IN DOGS WITH EXPERIMENTALLY INDUCED OSTEOARTHRITIS

Post-mortem feasibility of dual-energy computed tomography in the detection of bone edema-like lesions in the equine foot: a proof of concept

Introduction

In this proof-of-concept study, the post-mortem feasibility of dual-energy computed tomography (DECT) in the detection of bone edema-like lesions in the equine foot is described in agreement with the gold standard imaging technique, which is magnetic resonance imaging (MRI).

Methods

A total of five equine cadaver feet were studied, of which two were pathological and three were within normal limits and served as references. A low-field MRI of each foot was performed, followed by a DECT acquisition. Multiplanar reformations of DECT virtual non-calcium images were compared with MRI for the detection of bone edema-like lesions. A gross post-mortem was performed, and histopathologic samples were obtained of the navicular and/or distal phalanx of the two feet selected based on pathology and one reference foot.

Results

On DECT virtual non-calcium imaging, the two pathological feet showed diffuse increased attenuation corresponding with bone edema-like lesions, whereas the three reference feet were considered normal. These findings were in agreement with the findings on the MRI. Histopathology of the two pathologic feet showed abnormalities in line with bone edema-like lesions. Histopathology of the reference foot was normal.

Conclusion

DECT virtual non-calcium imaging can be a valuable diagnostic tool in the diagnosis of bone edema-like lesions in the equine foot. Further examination of DECT in equine diagnostic imaging is warranted in a larger cohort, different locations, and alive animals.

Bone marrow lesions: plugging the holes in our knowledge using animal models

Bone marrow lesions (BMLs), which are early signs of osteoarthritis (OA) that are associated with the presence, onset and severity of pain, represent an emerging imaging biomarker and clinical target. Little is known, however, regarding their early spatial and temporal development, structural relationships or aetiopathogenesis, because of the sparsity of human early OA imaging and paucity of relevant tissue samples. The use of animal models is a logical approach to fill the gaps in our knowledge, and it can be informed by appraising models in which BMLs and closely related subchondral cysts have already been reported, including in spontaneous OA and pain models. The utility of these models in OA research, their relevance to clinical BMLs and practical considerations for their optimal deployment can also inform medical and veterinary clinicians and researchers alike.

Re-thinking osteoarthritis pathogenesis: what can we learn (and what do we need to unlearn) from mouse models about the mechanisms involved in disease development

Efforts to develop effective disease-modifying drugs to treat osteoarthritis have so far proved unsuccessful with a number of promising drug candidates from pre-clinical studies failing to show efficacy in clinical trials. It is therefore timely to re-evaluate our current understanding of osteoarthritis pathogenesis and the similarities and differences in disease development between commonly used pre-clinical mouse models and human patients. There is substantial heterogeneity between patients presenting with osteoarthritis and mounting evidence that the pathways involved in osteoarthritis (e.g. Wnt signalling) differ between patient sub-groups. There is also emerging evidence that the pathways involved in osteoarthritis differ between the STR/ort mouse model (the most extensively studied mouse model of spontaneously occurring osteoarthritis) and injury-induced osteoarthritis mouse models. For instance, while canonical Wnt signalling is upregulated in the synovium and cartilage at an early stage of disease in injury-induced osteoarthritis mouse models, this does not appear to be the case in the STR/ort mouse. Such findings may prove insightful for understanding the heterogeneity in mechanisms involved in osteoarthritis pathogenesis in human disease. However, it is important to recognise that there are differences between mice and humans in osteoarthritis pathogenesis. A much more extensive array of pathological changes are evident in osteoarthritic joints in individual mice with osteoarthritis compared to individual patients. There are also specified differences in the pathways involved in disease development. For instance, although increased TGF-β signalling is implicated in osteoarthritis development in both mouse models of osteoarthritis and human disease, in mice, this is mainly mediated through TGF-β3 whereas in humans, it is through TGF-β1. Studies in other tissues have shown TGF-β1 is more potent than TGF-β3 in inducing the switch to SMAD1/5 signalling that occurs in osteoarthritic cartilage and that TGF-β1 and TGF-β3 have opposing effects on fibrosis. It is therefore possible that the relative contribution of TGF-β signalling to joint pathology in osteoarthritis differs between murine models and humans. Understanding the similarities and differences in osteoarthritis pathogenesis between mouse models and humans is critical for understanding the translational potential of findings from pre-clinical studies.

Comparison of Digital Radiography, Computed Tomography, and Magnetic Resonance Imaging Features in Canine Spontaneous Degenerative Stifle Joint Osteoarthritis

Canine stifle joint osteoarthritis (OA) is characterized by damage and degeneration of the articular cartilage and subchondral bone, bony hypertrophy at the margins, and synovial joint membrane changes. Non-invasive imaging modalities, such as digital radiography (DR), computed tomography (CT), and magnetic resonance imaging (MRI), can be used to describe these changes. However, the value of MRI in diagnosing spontaneous canine OA and the comparison of different imaging modalities have seldom been addressed. This study compared multiple noninvasive imaging modalities in canine spontaneous stifle OA cases. Four client-owned dogs with five spontaneously affected OA stifle joints were recruited and underwent DR, CT, and MRI. Information on osteophytes/enthesophytes, ligament/tendon lesions, synovial effusion and membrane thickening, subchondral bone lesions, and meniscal and cartilage lesions were scored and compared. The results showed that MRI provides the most comprehensive and superior lesion detection sensitivity for ligament, meniscus, cartilage, and synovial effusions. DR provides adequate bony structure information, while CT provides the most delicate images of bony structure lesions. These imaging findings may provide further understanding of the disease and help clinicians draft a more precise treatment plan.

Knee Cartilage and Subchondral Bone Evaluations by Magnetic Resonance Imaging Correlate with Histological Biomarkers in an Osteoarthritis Rabbit Model

OBJECTIVE

To evaluate pathological changes in cartilage and subchondral bone MRI biomarkers in a rabbit model of osteoarthritis (OA) and correlate these with histological variations.

DESIGN

Transection of the anterior cruciate ligament was performed on the right knee of eighteen 12-week-old New Zealand white rabbits to induce OA. 3-Tesla MR images were obtained from 18 healthy control knees (left) and 18 knees with OA (right). Imaging biomarkers included volume, thickness, T1 and T2* cartilage parametric maps, and several subchondral bone features: bone volume to total volume ratio, trabecular thickness, trabecular spacing, trabecular number (TbN), 2D and 3D fractal dimensions, and quality of trabecular score (QTS). Microscopic analysis of the lateral femoral condyles was set as the ground truth.

RESULTS

When healthy and osteoarthritic knees were compared, significant differences were seen in the T1 and T2* values of the femur and tibia cartilage and in the subchondral bone volume to total volume, TbN, and QTS of both the lateral and medial aspects of the femur and tibia. Histological findings revealed significant osteoarthritic changes between healthy and osteoarthritic knees in stain, structure, chondrocyte density, total score, and subchondral bone biomarker levels. A positive correlation was found between histological staining, structure, chondrocyte density, and total score variables in T1 and T2* cartilage biomarkers. A negative correlation was observed between histological subchondral bone variables and magnetic resonance D2D and QTS biomarkers.

CONCLUSION

Quantification of several cartilage and subchondral bone imaging biomarkers in a rabbit model of OA allows the detection of significant changes, which are correlated with histological findings.

Moving Beyond the Limits of Detection: The Past, the Present, and the Future of Diagnostic Imaging in Canine Osteoarthritis

Osteoarthritis (OA) is the most common orthopedic condition in dogs, characterized as the chronic, painful end-point of a synovial joint with limited therapeutic options other than palliative pain control or surgical salvage. Since the 1970s, radiography has been the standard-of-care for the imaging diagnosis of OA, despite its known limitations. As newer technologies have been developed, the limits of detection have lowered, allowing for the identification of earlier stages of OA. Identification of OA at a stage where it is potentially reversible still remains elusive, however, yet there is hope that newer technologies may be able to close this gap. In this article, we review the changes in the imaging of canine OA over the past 50 years and give a speculative view on future innovations which may provide for earlier identification, with the ultimate goal of repositioning the limit of detection to cross the threshold of this potentially reversible disease.

Animal Models of Bone Marrow Lesions in Osteoarthritis

Bone marrow lesions are abnormalities in magnetic resonance images that have been associated with joint pain and osteoarthritis in clinical studies. Increases in the volume of bone marrow lesions have been associated with progression of joint degeneration, leading to the suggestion that bone marrow lesions may be an early indicator of—or even a contributor to—cartilage loss preceding irreversible damage to the joint. Despite evidence that bone marrow lesions play a role in osteoarthritis pathology, very little is known about the natural history of bone marrow lesions and their contribution to joint degeneration. As a result, there are limited data regarding the cell activity within a bone marrow lesion and any associated bone‐cartilage cross‐talk. Animal models provide the best approach for understanding bone marrow lesions at their early, reversible stages. Here, we review the few animal studies of bone marrow lesions. An ideal animal model of a bone marrow lesion occurs in joints large enough to accurately measure bone marrow lesion volume. Additionally, the ideal animal model would facilitate the study of bone‐cartilage cross‐talk by generating the bone marrow lesion immediately adjacent to subchondral bone and would do so without causing direct damage to neighboring soft tissues to isolate the effects of the bone marrow lesion on cartilage loss. Early reports demonstrate the feasibility of such an animal model. Given the irreversible nature of osteoarthritic changes in the joint, factors such as bone marrow lesions that are present early in disease pathogenesis remain an enticing target for new therapeutic approaches. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Pathogenesis of Axial Spondyloarthritis - Sources and Current State of Knowledge

Scientific breakthroughs have culminated in the development of the spondyloarthritis (SpA) concept as a family of rheumatic diseases, distinct from rheumatoid arthritis. The demonstration of inflammatory lesions in the sacroiliac joints and spine of patients with axial symptoms of SpA who lacked radiographic features of ankylosing spondylitis (AS) helped refine the SpA concept. Axial SpA includes patients with AS and patients with axial symptoms previously categorized as undifferentiated SpA. This review examines the sources of knowledge that inform axial SpA pathogenesis, highlighting current limitations, and a basic working model of axial SpA pathogenesis.

Bone marrow lesions in knee osteoarthritis: regional differences in tibial subchondral bone microstructure and their association with cartilage degeneration

OBJECTIVE

The aim of this study was to investigate how bone microstructure within bone marrow lesions (BMLs) relates to the bone and cartilage across the whole human tibial plateau.

DESIGN

Thirty-two tibial plateaus from patients with osteoarthritis (OA) at total knee arthroplasty and eleven age-matched non-OA controls, were scanned ex vivo by MRI to identify BMLs and by micro CT to quantitate the subchondral (plate and trabecular) bone microstructure. For cartilage evaluation, specimens were processed histologically.

RESULTS

BMLs were detected in 75% of the OA samples (OA-BML), located predominantly in the anterior-medial (AM) region. In contrast to non-OA control and OA-no BML, in OA-BML differences in microstructure were significantly more evident between subregions. In OA-BML, the AM region contained the most prominent structural alterations. Between-group comparisons showed that the AM region of the OA-BML group had significantly higher histological degeneration (OARSI grade) (P < .0001, P < .05), thicker subchondral plate (P < .05, P < .05), trabeculae that are more anisotropic (P < .0001, P < .05), well connected (P < .05, P = n.s), and more plate-like (P < 0.05, P < 0.05), compared to controls and OA-no BML at this site. Compared to controls, OA-no BML had significantly higher OARSI grade (P < .0001), and lower trabecular number (P < .05).

CONCLUSION

In established knee OA, both the extent of cartilage damage and microstructural degeneration of the subchondral bone were dependent on the presence of a BML. In OA-no BML, bone microstructural alterations are consistent with a bone attrition phase of the disease. Thus, the use of BMLs as MRI image-based biomarkers appear to inform on the degenerative state within the osteochondral unit.

Degree of Preoperative Subchondral Bone Marrow Lesion Is Associated With Postoperative Outcome After Medial Opening Wedge High Tibial Osteotomy

BACKGROUND

In osteoarthritis of the knee, subchondral bone marrow lesion (BML) is known to be significantly associated with the severity of pain. However, little is known about the influence of preoperative BML on postoperative outcomes after medial opening wedge high tibial osteotomy (MOWHTO).

PURPOSE

To compare patient-reported outcomes for those who underwent MOWHTO according to the severity of BML based on magnetic resonance imaging.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 136 patients who underwent MOWHTO between June 2011 and May 2016 with clinical and radiologic assessments before and after surgery were retrospectively enrolled. Patients were divided into 2 groups according to the presence or absence of BMLs. They were then subdivided into 4 or 3 groups based on the sum of BML scores of the medial femoral condyle and tibial plateau according to MRI (magnetic resonance imaging) Osteoarthritis Knee Score or Filardo classification, respectively. Associations between the severity of BML and postoperative 1- and 2-year Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) subscores were evaluated through linear regression analysis. At postoperative 2 years, the rate of patients having a WOMAC score improvement of 15 points based on minimum clinically important difference and patient satisfaction were compared between groups.

RESULTS

BMLs were present in 96 (70.6%) of 136 cases. There were no significant differences in demographics or radiographic variables between groups according to the presence/absence or severity of BMLs (all P > .05). There was a significant association between preoperative or 1-year postoperative WOMAC pain/function score and the extent or intensity of BMLs (all P < .05). After adjusting for age, body mass index, osteoarthritis grade, and hip-knee-ankle angle, the significance persisted in the association between the extent or intensity of BMLs and WOMAC pain/function score at 1 year after surgery (all P < .05). However, a significant association was not found at postoperative 2 years (all P > .05). All groups showed similar rates of WOMAC score showing 15 points of improvement and satisfaction after MOWHTO (all P > .05). At 2 years after surgery, 82.5% of patients with BMLs were satisfied with their operation, as compared with 84.4% of those without BMLs (P = .801).

CONCLUSION

Although worse clinical outcomes were associated with severe BML during the recovery period, MOWHTO provided a high degree of clinical improvement on patient-reported outcomes regardless of the severity of BML at 2 years postoperatively.

Relative skeletal distribution of proliferating marrow in the adult dog determined using 3'-deoxy-3'-[18 F]fluorothymidine

3'-deoxy-3'-[¹⁸ F]fluorothymidine (¹⁸ FLT) is a radiopharmaceutical tracer used with positron emission tomography (PET), often in combination with computed tomography (CT), to image DNA synthesis, and thus, cellular proliferation. Characteristic accumulation of the tracer within haematopoietic bone marrow provides a noninvasive means to assess marrow activity and distribution throughout the living animal. The present study utilizes three-dimensional analysis of ¹⁸ FLT-PET/CT scans to quantify the relative skeletal distribution of active marrow by anatomic site in the dog. Scans were performed on six healthy, adult (3-6 years of age), mixed-breed dogs using a commercially available PET/CT scanner consisting of a 64-slice helical CT scanner combined with an integrated four ring, high-resolution LSO PET scanner. Regions of interest encompassing 11 separate skeletal regions (skull, cervical vertebral column, thoracic vertebral column, lumbar vertebral column, sacrum, ribs, sternum, scapulae, proximal humeri, ossa coxarum, and proximal femora) were manually drawn based on CT images and thresholded by standardized uptake value to delineate bone marrow activity. Activity within each skeletal region was then divided by the total skeletal activity to derive the per cent of overall marrow activity within an individual site. The majority of proliferative marrow was located within the vertebral column. Of the sites traditionally accessed clinically for marrow sampling, the proximal humerus contained the largest percentage, followed by the ossa coxarum, proximal femur, and sternum, respectively. This information may be used to guide selection of traditional marrow sampling sites as well as inform efforts to spare important sites of haematopoiesis in radiation therapy planning.

Clinical magnetic resonance-enabled characterization of mono-iodoacetate-induced osteoarthritis in a large animal species

INTRODUCTION

Osteoarthritis (OA) is the most common form of arthritis. Medical and surgical treatments have yet to substantially diminish the global health and economic burden of OA. Due to recent advances in clinical imaging, including magnetic resonance imaging (MRI), a correlation has been established between structural joint damage and OA-related pain and disability. Existing preclinical animal models of OA are useful tools but each suffers specific roadblocks when translating structural MRI data to humans. Intraarticular injection of mono-iodoacetate (MIA) is a reliable, well-studied method to induce OA in small animals but joint size discrepancy precludes the use of clinical grade MRI to study structural disease. The porcine knee is suited for clinical MRI and demonstrates homology with humans. We set out to establish the first large animal model of MIA-induced knee OA in swine characterized by structural MRI.

MATERIALS AND METHODS

Yucatan swine (n = 27) underwent ultrasound-guided injection of knees with 1.2, 4, 12, or 40 mg MIA. MRI was performed at several time points over 12 weeks (n = 54 knees) and images were assessed according to a modified clinical grading scheme. Knees were harvested and graded up to 35 weeks after injection.

RESULTS

MIA-injected knees (n = 25) but not control knees (n = 29) developed gross degeneration. A total of n = 6,000 MRI measurements were recorded by two radiologists. MRI revealed progressive cartilage damage, bone marrow edema, erosions, and effusions in MIA-injected knees. Lesion severity and progression was influenced by time, dose, and inter-individual variability.

CONCLUSIONS

Intraarticular injection of MIA produced structural knee degradation that was reliably characterized using clinical MRI in swine. Destruction was progressive and, similar to human OA, lesion severity was heterogeneous between and within treatment groups.

The Site of Bone Marrow Acquisition Affects the Myeloid to Erythroid Ratio in Apparently Healthy Dogs

Bone marrow (BM) cytology and histopathology are complementary tools used to investigate hematological diseases. The purpose of this study was to determine if there are site-dependent differences in the diagnostic quality, myeloid to erythroid ratio (MER), and discordant findings in samples from different sites in the same dog. Eighteen apparently healthy dogs were used in the study. The sequence of sample acquisition was randomized according to a Latin square, and samples for BM cytology and histology were collected from both humeri and both ilial crests immediately after death. Board-certified clinical and anatomical pathologists read the cytology and histology, respectively. The data were analyzed using a mixed-effect model. The site of BM acquisition did not affect BM sample quality. The rate of discordant clinical findings between sites was 0.05 (95% confidence interval, 0.01-0.13). In general, by cytology, the MERs were slightly but significantly greater in samples from the ilial crests than from the humeri ( P = .01). The measured MER for histology was nearly twice that for cytology for all sites ( P < .001). In conclusion, there was a low-rate, site-dependent discordance in diagnostic findings in BM samples and differences in MER between the ilial crest and the humerus. A similar study is justified in sick dogs with hematological disease to determine the effect of sampling site on discordant findings between sites.

Cross-sectional and longitudinal associations between serum inflammatory cytokines and knee bone marrow lesions in patients with knee osteoarthritis

OBJECTIVE

To describe cross-sectional and longitudinal associations between serum levels of interleukin (IL) - 6, IL-17A, IL-17F, IL-23 and knee bone marrow lesions (BMLs) in patients with knee osteoarthritis (OA).

DESIGN

Patients (n = 192) with symptomatic knee OA (mean 63 years, range 50-79, female 53%) were assessed at baseline and after 24 months. At each time point, serum IL-6, IL-17A, IL-17F and IL-23 were measured using Bio-Plex^® Multiplex Immunoassays with Luminex xMAP technology. Knee BMLs were scored using the modified whole organ MRI score (WORMS) from T2 weighted fat-suppressed fast spin echo magnetic resonance imaging (MRI). Multivariable linear regression and log binominal regression were used to determine the associations between cytokines and BMLs.

RESULTS

Baseline IL-6 (quarters) were significantly associated with total knee BMLs (P < 0.01 for the trend) as well as associated with an increase in BML score (P = 0.05 for the trend), after adjustment for confounders. Baseline IL-17F and IL-23 (highest quarters vs others) was associated with an increase in BML score in females (P = 0.04 for IL-17F; P = 0.01 for IL-23), but not in males, in multivariable analyses. In contrast, IL-17A was not significantly associated with BMLs in either females or males.

CONCLUSION

IL-6 is associated with increased knee BMLs in both females and males with OA. Serum IL-17F and IL-23 predicted increased knee BML scores in females only, suggesting that inflammation is involved in BML pathogenesis in knee OA, especially in women.

TRAIL REGISTRATION

ClinicalTrials.gov identifier: NCT01176344; Australian New Zealand Clinical Trials Registry: ACTRN12610000495022.

Bone marrow lesions in hip osteoarthritis are characterized by increased bone turnover and enhanced angiogenesis

OBJECTIVE

Bone marrow lesions (BML), previously denoted bone marrow edema, are detected as water signals by magnetic resonance imaging (MRI). Previous histologic studies were unable to demonstrate any edematous changes at the tissue level. Therefore, our aim was to investigate the underlying biological mechanisms of the water signal in MRI scans of bone affected by BML.

METHODS

Tetracycline labeling in addition to water sensitive MRI scans of 30 patients planned for total hip replacement surgery was undertaken. Twenty-one femoral heads revealed BML on MRI, while nine were negative and used as controls (CON). Guided by the MRI images cylindrical biopsies were extracted from areas with BML in the femoral heads. Tissue sections from the biopsies were subjected to histomorphometric image analyses of the cancellous bone envelope.

RESULTS

Patients with BML exhibited an average 40- and 18-fold increase of bone formation rate and mineralizing surface, respectively. Additionally, samples with BML demonstrated 2-fold reduction of marrow fat and 28-fold increase of woven bone. Immunohistochemical analysis showed a 4-fold increase of angiogenesis markers CD31 and von Willebrand Factor (vWF) in the BML-group compared to CON.

CONCLUSION

This study indicates that BML are characterized by increased bone turnover, vascularity and angiogenesis in keeping with it being a reparatory process. Thus, the water signal, which is the hallmark of BML on MRI, is most probably reflecting increased tissue vascularity accompanying increased remodeling activity.

THE USE OF SMALL FIELD-OF-VIEW 3 TESLA MAGNETIC RESONANCE IMAGING FOR IDENTIFICATION OF ARTICULAR CARTILAGE DEFECTS IN THE CANINE STIFLE: AN EX VIVO CADAVERIC STUDY

Noninvasive identification of canine articular cartilage injuries is challenging. The objective of this prospective, cadaveric, diagnostic accuracy study was to determine if small field-of-view, three tesla magnetic resonance imaging (MRI) was an accurate method for identifying experimentally induced cartilage defects in canine stifle joints. Forty-two canine cadaveric stifles (n = 6/group) were treated with sham control, 0.5, 1.0, or 3.0 mm deep defects in the medial or lateral femoral condyle. Proton density-weighted, T1-weighted, fast-low angle shot, and T2 maps were generated in dorsal and sagittal planes. Defect location and size were independently determined by two evaluators and compared to histologic measurements. Accuracy of MRI was determined using concordance correlation coefficients. Defects were identified correctly in 98.8% (Evaluator 1) and 98.2% (Evaluator 2) of joints. Concordance correlation coefficients between MRI and histopathology were greater for defect depth (Evaluator 1: 0.68-0.84; Evaluator 2: 0.76-0.83) compared to width (Evaluator 1: 0.30-0.54; Evaluator 2: 0.48-0.68). However, MRI overestimated defect depth (histopathology: 1.65 ± 0.94 mm; Evaluator 1, range of means: 2.07-2.38 mm; Evaluator 2, range of means: 2-2.2 mm) and width (histopathology: 6.98 ± 1.32 mm; Evaluator 1, range of means: 8.33-8.8 mm; Evaluator 2, range of means: 6.64-7.16 mm). Using the paired t-test, the mean T2 relaxation time of cartilage defects was significantly greater than the mean T2 relaxation time of adjacent normal cartilage for both evaluators (P < 0.0001). Findings indicated that MRI is an accurate method for identifying cartilage defects in the cadaveric canine stifle. Additional studies are needed to determine the in vivo accuracy of this method.

MAGNETIC RESONANCE IMAGING SCORING OF AN EXPERIMENTAL MODEL OF POST-TRAUMATIC OSTEOARTHRITIS IN THE EQUINE CARPUS

Magnetic resonance imaging (MRI) is the most sensitive imaging modality to detect the early changes of osteoarthritis. Currently, there is no quantifiable method to tract these pathological changes over time in the horse. The objective of this experimental study was to characterize the progression of MRI changes in an equine model of post-traumatic osteoarthritis using a semiquantitative scoring system for whole-organ evaluation of the middle carpal joint. On day 0, an osteochondral fragment was created in one middle carpal joint (OCI) and the contralateral joint (CON) was sham-operated in 10 horses. On day 14, study horses resumed exercise on a high-speed treadmill until the completion of the study (day 98). High-field MRI examinations were performed on days 0 (preosteochondral fragmentation), 14, and 98 and scored by three blinded observers using consensus agreement. Images were scored based on 15 independent articular features, and scores were compared between and within-groups. On days 14 and 98, OCI joints had significantly (P ≤ 0.05) higher whole-organ median scores (29.0 and 31.5, respectively), compared to CON joints (21.5 and 20.0, respectively). On day 14, OCI joints showed significant increases in high-signal bone lesion scores, and osteochondral fragment number and size. On day 98, high-signal bone lesion, low-signal bone lesion, osteophyte formation, cartilage signal abnormality, subchondral bone irregularity, joint effusion, and synovial thickening scores were significantly increased in OCI joints. Study results suggest that the MRI whole-organ scoring system reported here may be used to identify onset and progression of pathological changes following osteochondral injury.

Bone marrow lesions detected by specific combination of MRI sequences are associated with severity of osteochondral degeneration

BACKGROUND

Bone marrow lesions (BMLs) are useful diagnostic and prognostic markers in knee osteoarthritis (OA), but what they represent at the tissue level remains unclear. The aim of this study was to provide comprehensive tissue characterization of BMLs detected using two specific MRI sequences.

METHODS

Tibial plateaus were obtained from 60 patients (29 females, 31 males), undergoing knee arthroplasty for OA. To identify BMLs, MRI was performed ex vivo using T1 and PDFS-weighted sequences. Multi-modal tissue level analyses of the osteochondral unit (OCU) were performed, including cartilage volume measurement, OARSI grading, micro-CT analysis of bone microstructure, routine histopathological assessment and quantitation of bone turnover indices.

RESULTS

BMLs were detected in 74 % of tibial plateaus, the remainder comprising a No BML group. Of all BMLs, 59 % were designated BML 1 (detected only by PDFS) and 41 % were designated BML 2 (detected by both PDFS + T1). The presence of a BML was related to degeneration of the OCU, particularly within BML 2. When compared to No BML, BML 2 showed reduced cartilage volume (p = 0.008), higher OARSI scores (p = 0.004), thicker subchondral plate (p = 0.002), increased trabecular bone volume and plate-like structure (p = 0.0004), increased osteoid volume (p = 0.002) and thickness (p = 0.003), more bone marrow oedema (p = 0.03), fibrosis (p = 0.002), necrosis (p = 0.01) and fibrovascular cysts (p = 0.04). For most measures, BML 1 was intermediate between No BML and BML 2.

CONCLUSIONS

BMLs detected by specific MRI sequences identify different degrees of degeneration in the OCU. This suggests that MRI characteristics of BMLs may enable identification of different BML phenotypes and help target novel approaches to treatment and prevention of OA.

Treatment of bone marrow lesions (bone marrow edema)

Bone marrow lesions (BMLs) or using older terminology 'Bone marrow edema' is characterised by excessive water signals in the marrow space on magnetic resonance imaging or ultrasound; BMLs constitute a central component of a wide variety of inflammatory and non-inflammatory rheumatologic conditions affecting the musculoskeletal system: BMLs are not only considered significant sources of pain but also linked to increased disease activity in many musculoskeletal conditions (for example, osteoarthritis, rheumatoid arthritis). The purpose of this review is to summarise current knowledge about the treatment of BMLs, with an emphasis on the clinical and histological features of this entity in inflammatory and non-inflammatory disease. We also try to pair this hypothesis with the apparent beneficial effects of various treatment regimens, mainly within the group of bone antiresorptive drugs (calcitonin, bisphosphonates) on symptoms associated with BMLs.

Association of patellar bone marrow lesions with knee pain, patellar cartilage defect and patellar cartilage volume loss in older adults: a cohort study

AIM

To examine the cross-sectional and longitudinal associations of patellar bone marrow lesion (BMLs) with knee pain, cartilage defects and cartilage volume in older adults.

METHODS

A total of 904 randomly selected subjects (mean 62.4 years, 49.9% female) were studied. Fat suppressed T1-weighted spoiled gradient recall and T2-weighted fast spin echo magnetic resonance imaging (MRI) sequences were used to assess cartilage volume, cartilage defects and/or BMLs at baseline (n = 904) and 2.6 (range: 1.4-4.8) years' follow-up (n = 414). Knee pain was assessed by self-administered Western Ontario McMaster Osteoarthritis Index (WOMAC) questionnaire at baseline (n = 904) and follow-up (n = 790).

RESULTS

The prevalence of any patellar BMLs was 19% and was higher in those with tibiofemoral BMLs. In multivariable analyses, patellar BMLs were positively associated with any knee pain at baseline and an increase in knee pain when going up/down stairs (odds ratio (OR): 1.67, 95% confidence interval (CI): 1.08, 2.59) but not with other knee pain subscales. Patella BMLs were also associated with patellar cartilage defects both at baseline and change over time (OR: 1.76, 95% CI: 1.00, 3.70) but not tibiofemoral defects. Patellar BMLs were negatively associated with baseline and change in patella cartilage volume (β: -2.10%, 95% CI: -3.39%, -0.80%). These associations remained significant after further adjustment for tibiofemoral BMLs.

CONCLUSIONS

Patellar BMLs were consistently associated with increased knee pain especially going up/down stairs, increased patellar cartilage defects, and decreased patellar cartilage volume cross-sectionally and longitudinally, suggesting a predominantly compartment specific role for patellar BMLs.

[Bone marrow edema and joint injuries]

BACKGROUND

The development of bone marrow edema in body regions adjacent to joints can have many causes and a differentiation is not possible using magnetic resonance imaging (MRI).

DEFINITION

Bone marrow edema is not necessarily an indication for microfractures. The definition of bone marrow edema is a purely radiological description. There is no uniform classification of bone marrow edema. The clinical significance, therapy and course are heterogeneous; therefore, there are no uniform recommendations for therapy.

DIAGNOSTICS

A bone marrow edema visible in MRI does not always lead to certain inferences regarding the pathogenesis. In order to be able to detect fractures it is necessary to carry out a biopsy and a histological examination.

CONCLUSION

The interpretation of MRI results and the derivation of a therapy in every case need a balanced assessment of the MRI results, medical history, clinical investigations and clinical symptoms.

Subchondral bone in osteoarthritis: insight into risk factors and microstructural changes

Osteoarthritis (OA) is a major cause of disability in the adult population. As a progressive degenerative joint disorder, OA is characterized by cartilage damage, changes in the subchondral bone, osteophyte formation, muscle weakness, and inflammation of the synovium tissue and tendon. Although OA has long been viewed as a primary disorder of articular cartilage, subchondral bone is attracting increasing attention. It is commonly reported to play a vital role in the pathogenesis of OA. Subchondral bone sclerosis, together with progressive cartilage degradation, is widely considered as a hallmark of OA. Despite the increase in bone volume fraction, subchondral bone is hypomineralized, due to abnormal bone remodeling. Some histopathological changes in the subchondral bone have also been detected, including microdamage, bone marrow edema-like lesions and bone cysts. This review summarizes basic features of the osteochondral junction, which comprises subchondral bone and articular cartilage. Importantly, we discuss risk factors influencing subchondral bone integrity. We also focus on the microarchitectural and histopathological changes of subchondral bone in OA, and provide an overview of their potential contribution to the progression of OA. A hypothetical model for the pathogenesis of OA is proposed.

Correlation between histopathologic, arthroscopic, and magnetic resonance imaging findings in dogs with medial coronoid disease

OBJECTIVE

To describe the magnetic resonance imaging (MRI), arthroscopic, and histopathologic changes in dogs with medial coronoid disease and to identify potential relationships between these findings.

STUDY DESIGN

Retrospective case series.

SAMPLE POPULATION

Twenty-five diseased medial coronoid processes (MCP) were collected from 19 dogs with a confirmed diagnosis of medial coronoid disease that were surgically treated by subtotal coronoid ostectomy. A reference group of normal MCP was collected from 9 dogs euthanatized for reasons unrelated to elbow disease.

METHODS

MCP specimens were evaluated by MRI using a novel grading scheme (all dogs), arthroscopy using a modified Outerbridge scheme (affected dogs only) and histopathology (all dogs).

RESULTS

The common histopathologic findings were subchondral microfractures, subchondral microfractures continuous with cartilaginous fissures, moderate to severe hypercellularity of the marrow space, trabecular bone necrosis, and articular cartilage degeneration. The severity of cartilage disease in the MCP was moderate to severe in most specimens, even in cases with minimal arthroscopic pathology. Three distinct patterns of bone marrow lesion (BML) were identified adjacent to the MCP, but there was no correlation between BML pattern and either histopathologic or arthroscopic findings. There was moderate correlation between modified Outerbridge scores and MRI scores. No correlation was identified between the histopathologic changes and either MRI or arthroscopic scores.

CONCLUSION

There was no significant correlation between the clinical scores and histopathologic changes. Ongoing improvements in the resolution of noninvasive imaging techniques will likely improve description and understanding of the MCP disease in dogs.

Evaluation of bone marrow lesion volume as a knee osteoarthritis biomarker--longitudinal relationships with pain and structural changes: data from the Osteoarthritis Initiative

INTRODUCTION

Bone marrow lesion (BML) size may be an important imaging biomarker for osteoarthritis-related clinical trials and reducing BML size may be an important therapeutic goal. However, data on the interrelationships between BML size, pain, and structural progression are inconsistent and rarely examined in the same cohort. Therefore, we evaluated the cross-sectional and longitudinal associations of BML volume with knee pain and joint space narrowing (JSN).

METHODS

A BML volume assessment was performed on magnetic resonance images of the knee collected at the 24- and 48-month Osteoarthritis Initiative visits from a convenience sample of 404 participants in the progression cohort. During the same visits, knee pain was assessed with WOMAC pain scores and knee radiographs were acquired and scored for JSN. BML volume was summed to generate a total knee volume and an index tibiofemoral compartment volume (compartment with greater baseline JSN). Primary analyses included multiple linear regressions (outcome = pain, predictor = total knee BML volume) and logistic regressions (outcome = JSN, predictor = index tibiofemoral compartment BML volume).

RESULTS

This sample was 49% female with a mean age of 63 (9.2 standard deviation (SD)) years, and 71% had radiographic osteoarthritis in the study knee. Larger baseline BMLs were associated with greater baseline knee pain (P = 0.01), the presence of JSN at baseline (odds ratio (OR) = 1.50, 95% confidence interval (CI) = 1.23 to 1.83), and JSN progression (OR = 1.27, 95%CI = 1.11 to 1.46). Changes in total knee BML volume had a positive association with changes in knee pain severity (P = 0.004) and this association may be driven by knees that were progressing from no or small baseline BMLs to larger BMLs. In contrast, we found no linear positive relationship between BML volume change and JSN progression. Instead, regression of medial tibiofemoral BML volume was associated with JSN progression compared to knees with no or minimal changes in BML volume (OR = 3.36, 95%CI = 1.55 to 7.28). However, follow-up analyses indicated that the association between JSN progression and BML volume change may primarily be influenced by baseline BML volume.

CONCLUSION

Large baseline BMLs are associated with greater baseline knee pain, the presence of JSN at baseline, and disease progression. Additionally, BML regression is associated with decreased knee pain but not a reduced risk of concurrent JSN progression.

Fast presurgical magnetic resonance imaging of meniscal tears and concurrent subchondral bone marrow lesions. Study of dogs with naturally occurring cranial cruciate ligament rupture

Meniscal tears and subchondral bone marrow lesions have both been described in dogs with cranial cruciate ligament rupture, but their possible concurrence has not been evaluated. In a population of 14 dogs exhibiting signs of stifle pain with surgically confirmed cranial cruciate ligament rupture, a short presurgical 1.5T magnetic resonance (MR) imaging protocol including dorsal proton density, dorsal T1-weighted gradient recalled echo, and sagittal fat-saturated dual echo sequences was tested to further investigate these features and illustrate meniscal tears. Interobserver agreement for detection of medial meniscal tears (k=0.83) and bone marrow lesions (k=0.87) was excellent. Consensus MR reading allowed detection of nine out of 12 surgically confirmed medial meniscal tears and there was no false positive. All dogs had cruciate ligament enthesis-related bone marrow lesions in the tibia, femur or both bones. Additionally, among the 12 dogs with confirmed medial meniscal tears, subchondral bone marrow lesions were present in the caudomedial (9 dogs) and caudoaxial (11 dogs) regions of the tibial plateau, resulting in odds ratios (13.6, p=0.12, and 38.3, p=0.04, respectively) that had large confidence intervals due to the small group size of this study. The other two dogs had neither tibial bone marrow lesions in these locations nor medial meniscal tears. These encouraging preliminary results warrant further investigation using this clinically realistic preoperative MR protocol. As direct diagnosis of meniscal tears remained challenging in dogs even with high-field MR, identification of associated signs such as subchondral bone marrow lesions might indirectly allow suspicion of an otherwise unrecognized meniscal tear.

Epidemiological investigation of osteoarthritis in middle-aged mongolian and senior residents of the inner mongolia autonomous region

Background

To investigate the prevalence and characteristics of osteoarthritis (OA) in Mongolian middle-aged and senior residents of the Inner Mongolia autonomous region, compared with the prevalence of OA in different regions, to understand the OA-associated factors and provide theoretical evidences for intervention and prevention.

Objectives

Thereby the prevalence, distribution characteristics and correlative factors of OA in Mongolian middle-aged and senior residents in the Inner Mongolia autonomous region were investigated in this study.

Materials and Methods

Rural and urban residents in Hohhot, Baotou and Erdos were selected using stratified, multi-stage and cluster random sampling. 2000 residents aging over 45 filled out questionnaires, underwent specialized physical and X-ray examinations. The factors affecting OA were analyzed by the multivariate unconditional logistic regression.

Results

Obtained total of 1877 questionnaires were completed. 93% of the residents were unaware of OA-related issues. The prevalence of radiological OA and clinical OA (neck OA: 36.72%; waist OA: 44.02%; knee OA: 12.43%; hand OA: 6.83%) were 62.17% and 56.15%, respectively. Urban residents were more subjected to cervical spine (χ² = 8.92, P = 0.005) and less to lumbar spine disease (χ² = 10.32, P = 0.004) compared to rural ones. The prevalence of OA in knees and hands of females (χ² = 8.65, P = 0.003) was significantly higher than males (χ²=4.37, P=0.042). The prevalence of OA in postmenopausal females was slightly higher than males (χ² = 3.86, P = 0.052), with no statically significant difference. The risks of OA obviously increased with age. The residents with hypertension, diabetes and atherosclerosis were more subjected to OA.

Conclusions

The prevalence of OA in Mongolian middle-aged and senior residents in part of the Inner Mongolia autonomous region was similar to the other ethnic groups. The prevalence of OA was affected by age, gender, location, hypertension, diabetes, atherosclerosis and osteoporosis. The residents need further educations about OA prevention and treatment.

Fadiga óssea: causa de dor em joelhos na osteoartrite

A dor no joelho é o sintoma mais comum na osteoartrite, sendo a principal causa de incapacidade crônica em idosos e uma das principais fontes de morbidade atribuível à osteoartrite em geral. As causas de dor no joelho em pessoas com osteoartrite não são facilmente entendidas e o conhecimento sobre as causas da dor é fundamental para que futuramente sejam realizadas intervenções específicas. A fadiga óssea representa o remodelamento do osso subcondral na osteoartrite, levando a uma consequente alteração na forma do osso e/ou perda óssea. No entanto, a fadiga óssea não é algo facilmente interpretado, pois é de difícil detecção na ausência de defeitos claros da cortical e pela sobreposição de estruturas ósseas nas radiografias convencionais. A fadiga óssea está associada não apenas a dor no joelho, mas também a rigidez e incapacidade. Se a fadiga ocorre antes da osteoartrite avançada, isso sugere que alterações no osso subcondral podem ocorrer simultaneamente a alterações da cartilagem e que tratamentos visando sua preservação podem não ser eficazes. Lesões com padrão de edema ósseo estão associadas e são fatores preditivos para fadiga óssea. Este trabalho tem por objetivo rever a literatura mostrando a importância da fadiga óssea e de como diagnosticar esta alteração nos exames de imagem.

[Bone marrow edema in magnetic resonance imaging. A misleading term?]

Magnetic resonance imaging (MRI) is a mainstay in musculoskeletal imaging. The term"bone marrow edema" is frequently used for describing the radiological findings, especially with respect to rheumatic diseases. The referring physician should be aware that this term has a purely descriptive character and the pathophysiology of signal alterations in MRI shows a broad spectrum certainly not always corresponding to increased liquid contents. The recommendations therefore tend towards the use of the neutral terms"osteitis","bone marrow edema-like lesion" or"bone marrow lesion" instead of the misleading term"bone marrow edema".

Bone marrow lesions: a universal bone response to injury?

The ever increasing use of magnetic resonance imaging in clinical practice has led to the recognition of a new entity, bone marrow lesions (BMLs). These lesions are characterized by excessive water signals in the marrow space and have emerged as a central component of many different diseases affecting the musculoskeletal system. BMLs have in particular been associated with a wide variety of inflammatory and non-inflammatory rheumatologic conditions and are not only considered significant sources of pain, but also linked to the worsening of patient prognosis in many disease states. In this review, we summarize the current knowledge on BMLs with an emphasis on the clinical and histological features of this entity in inflammatory and non-inflammatory disease and provide a unifying hypothesis based on the appearance with various imaging technologies. We also try to pair this hypothesis with the apparent beneficial effects of various treatment regimens, mainly within the group of bone antiresorptive drugs (calcitonin, bisphosphonates) on symptoms associated with BMLs.

Chondroitin sulphate reduces both cartilage volume loss and bone marrow lesions in knee osteoarthritis patients starting as early as 6 months after initiation of therapy: a randomised, double-blind, placebo-controlled pilot study using MRI

Objective

To determine the effect of chondroitin sulphate (CS) treatment on cartilage volume loss, subchondral bone marrow lesions (BML), synovitis and disease symptoms in patients with knee osteoarthritis (OA).

Methods

In this pilot multicentre, randomised, double-blind, controlled trial in primary knee OA, 69 patients with clinical signs of synovitis were randomised to receive CS 800 mg or placebo once daily for 6 months followed by an open-label phase of 6 months in which patients in both groups received CS 800 mg once daily. Cartilage volume and BML were assessed by MRI at baseline and at 6 and 12 months; synovial membrane thickness was assessed at baseline and at 6 months.

Results

The CS group showed significantly less cartilage volume loss than the placebo group as early as 6 months for the global knee (p=0.030), lateral compartment (p=0.015) and tibial plateaus (p=0.002), with significance persisting at 12 months. Significantly lower BML scores were found for the CS group at 12 months in the lateral compartment (p=0.035) and the lateral femoral condyle (p=0.044). Disease symptoms were similar between the two groups.

Conclusion

CS treatment significantly reduced the cartilage volume loss in knee OA starting at 6 months of treatment, and BML at 12 months. These findings suggest a joint structure protective effect of CS and provide new in vivo information on its mode of action in knee OA.

Bone marrow lesions predict site-specific cartilage defect development and volume loss: a prospective study in older adults

Introduction

Recent evidence suggests that bone marrow lesions (BMLs) play a pivotal role in knee osteoarthritis (OA). The aims of this study were to determine: 1) whether baseline BML presence and/or severity predict site-specific cartilage defect progression and cartilage volume loss; and 2) whether baseline cartilage defects predict site-specific BML progression.

Methods

A total of 405 subjects (mean age 63 years, range 52 to 79) were measured at baseline and approximately 2.7 years later. Magnetic resonance imaging (MRI) of the right knee was performed to measure knee cartilage volume, cartilage defects (0 to 4), and BMLs (0 to 3) at the medial tibial (MT), medial femoral (MF), lateral tibial (LT), and lateral femoral (LF) sites. Logistic regression and generalized estimating equations were used to examine the relationship between BMLs and cartilage defects and cartilage volume loss.

Results

At all four sites, baseline BML presence predicted defect progression (odds ratio (OR) 2.4 to 6.4, all P < 0.05), and cartilage volume loss (-0.9 to -2.9% difference per annum, all P < 0.05) at the same site. In multivariable analysis, there was a significant relationship between BML severity and defect progression at all four sites (OR 1.8 to 3.2, all P < 0.05) and BML severity and cartilage volume loss at the MF, LT, and LF sites (β -22.1 to -42.0, all P < 0.05). Additionally, baseline defect severity predicted BML progression at the MT and LF sites (OR 3.3 to 3.7, all P < 0.01). Lastly, there was a greater increase in cartilage volume loss at the MT and LT sites when both larger defects and BMLs were present at baseline (all P < 0.05).

Conclusions

Baseline BMLs predicted site-specific defect progression and cartilage volume loss in a dose-response manner suggesting BMLs may have a local effect on cartilage homeostasis. Baseline defects predicted site-specific BML progression, which may represent increased bone loading adjacent to defects. These results suggest BMLs and defects are interconnected and play key roles in knee cartilage volume loss; thus, both should be considered targets for intervention.

Bone marrow lesions in people with knee osteoarthritis predict progression of disease and joint replacement: a longitudinal study

OBJECTIVES

The presence of bone marrow lesions (BMLs) has been linked to pain and progression of knee OA. The aim of this study was to determine the relationship between BMLs and longitudinal change in tibial cartilage volume and risk of knee joint replacement in subjects with knee OA.

METHODS

One hundred and nine men and women with symptomatic knee OA were recruited. The same knee was imaged using MRI at baseline and ∼2 years later. Tibial cartilage volume and BMLs were measured. Knee joint replacement over 4 years was determined.

RESULTS

The mean age of the subjects at baseline was 63.2 (s.d. 10.3) years. BMLs were present in 66% of the subjects. Cross-sectionally, BMLs were negatively associated with both medial (regression coefficient -121.4; 95% CI -183.8, -859.1; P<0.001) and lateral (regression coefficient -142.1; 95% CI -241.8, -42.4; P=0.01) tibial cartilage volume data. Longitudinally, for every 1-score increase in baseline BML severity (range 0-4), the annual total tibial cartilage loss was increased by 1.14% (95% CI 0.29%, 1.87%; P=0.01). The risk of knee joint replacement over 4 years increased with increasing BML score (odds ratio 1.57; 95% CI 1.04, 2.35; P=0.03).

CONCLUSION

The prevalence and severity of BMLs are associated with less tibial cartilage volume and greater cartilage loss over 2 years. Moreover, severity of BMLs was positively associated with risk of knee joint replacement over 4 years. This provides further support for the importance of BMLs in identifying those with OA most likely to progress. Identifying factors that prevent or reduce the severity of BMLs may provide an important target in the prevention of disease progression and treatment of OA, and the subsequent need for arthroplasty.

Diagnostic imaging of the canine stifle: a review

The stifle joint, a common location for lameness in dogs, is a complex arrangement of osseous, articular, fibrocartilaginous, and ligamentous structures. The small size of its component structures, restricted joint space, and its intricate composition make successful diagnostic imaging a challenge. Different tissue types and their superimposition limit successful diagnostic imaging with a single modality. Most modalities exploit the complexity of tissue types found in the canine stifle joint. Improved understanding of the principles of each imaging modality and the properties of the tissues being examined will enhance successful diagnostic imaging.

Comparison of magnetic resonance imaging, computed tomography, and radiography for assessment of noncartilaginous changes in equine metacarpophalangeal osteoarthritis

We compared the ability of 1.5 T magnetic resonance imaging (MRI), computed tomography (CT), and computed radiography (CR) to evaluate noncartilaginous structures of the equine metacarpophalangeal joint (MCP), and the association of imaging changes with gross cartilage damage in the context of osteoarthritis. Four CR projections, helical single-slice CT, and MRI (Ti-weighted gradient recalled echo [GRE], T2*-weighted GRE with fast imaging employing steady-state acquisition [FIESTA], T2-weighted fast spin echo with fat saturation, and spoiled gradient recalled echo with fat saturation ISPGR-FS]) were performed on 20 racehorse cadaver forelimbs. Osteophytosis, synovial effusion, subchondral bone lysis and sclerosis, supracondylar lysis, joint fragments, bone marrow lesions, and collateral desmopathy were assessed with each modality. Interexaminer agreement was inferior to intraexaminer agreement and was generally moderate (i.e., 0.4 < kappa < 0.6). Subchondral bone sclerosis scores using CT or MRI were correlated significantly with the reference quantitative CT technique used to assess bone mineral density (P < 0.0001). Scores for subchondral lysis and osteophytosis were higher with MRI or CT vs. CR (P < 0.0001). Although differences between modalities were noted, osteophytosis, subchondral sclerosis, and lysis as well as synovial effusion were all associated with the degree of cartilage damage and should be further evaluated as potential criteria to be included in a whole-organ scoring system. This study highlights the capacity of MRI to evaluate noncartilaginous changes in the osteoarthritic equine MCP joint.

Correlation of signal attenuation-based quantitative magnetic resonance imaging with quantitative computed tomographic measurements of subchondral bone mineral density in metacarpophalangeal joints of horses

OBJECTIVE

To evaluate the ability of signal attenuation-based quantitative magnetic resonance imaging (QMRI) to estimate subchondral bone mineral density (BMD) as assessed via quantitative computed tomography (QCT) in osteoarthritic joints of horses.

SAMPLE POPULATION

20 metacarpophalangeal joints from 10 horse cadavers.

PROCEDURES

Magnetic resonance (MR) images (dorsal and transverse T1-weighted gradient recalled echo [GRE] and dorsal T2*-weighted GRE fast imaging employing steady-state acquisition [T2*-FIESTA]) and transverse single-slice computed tomographic (CT) images of the joints were acquired. Magnetic resonance signal intensity (SI) and CT attenuation were quantified in 6 regions of interest (ROIs) in the subchondral bone of third metacarpal condyles. Separate ROIs were established in the air close to the joint and used to generate corrected ratios and SIs. Computed tomographic attenuation was corrected by use of a calibration phantom to obtain a K(2)HPO(4)-equivalent density of bone. Correlations between QMRI performed with different MR imaging sequences and QCT measurements were evaluated. The intraobserver repeatability of ROI measurements was tested for each modality.

RESULTS

Measurement repeatability was excellent for QCT (R(2) = 98.3%) and QMRI (R(2) = 98.8%). Transverse (R(2) = 77%) or dorsal (R(2) = 77%) T1-weighted GRE and QCT BMD measurements were negatively correlated, as were dorsal T2*-FIESTA and QCT (R(2) = 80%) measurements. Decreased bone SI during MR imaging linearly reflected increased BMD.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this ex vivo study suggested that signal attenuation-based QMRI was a reliable, clinically applicable method for indirect estimation of subchondral BMD in osteoarthritic metacarpophalangeal joints of horses.

Targeting subchondral bone for treating osteoarthritis: what is the evidence?

Over the past few decades, significant progress has been made with respect to new concepts about the pathogenesis of osteoarthritis (OA). This article summarises some of the knowledge we have today on the involvement of the subchondral bone in OA. It provides substantial evidence that changes in the metabolism of the subchondral bone are an integral part of the OA disease process and that these alterations are not merely secondary manifestations, but are part of a more active component of the disease. Thus, a strong rationale exists for therapeutic approaches that target subchondral bone resorption and/or formation, and data evaluating the drugs targeting bone remodelling raise the hope that new treatment options for OA may become available.

Subchondral bone marrow lesions are highly associated with, and predict subchondral bone attrition longitudinally: the MOST study

OBJECTIVE

Subchondral bone attrition (SBA) is defined as flattening or depression of the osseous articular surface. The causes of attrition are unknown, but remodeling processes due to chronic overload that are reflected as bone marrow edema-like lesions (BMLs) on magnetic resonance imaging (MRI) might predispose the subchondral bone to subsequent attrition. The aim of this study was to evaluate the cross-sectional and longitudinal association of BMLs with SBA in the same subregion of the knee.

DESIGN

The Multicenter Osteoarthritis (MOST) study is a longitudinal observational study of individuals who have or are at high risk for knee osteoarthritis. Subjects with available baseline and 30-months follow-up MRI were included. Patients with a recent history of trauma or findings suggestive of post-traumatic bone marrow changes were excluded. Subchondral BMLs and SBA were scored semiquantitatively from 0 to 3 in 10 tibiofemoral subregions. We evaluated the association of prevalent BMLs at baseline with the presence of prevalent and incident SBA on a per-subregion basis using logistic regression. We also cross-sectionally evaluated the association of BML grade severity and presence of baseline SBA.

RESULTS

One thousand and twenty-five knees were included. 8.9% of the analyzed knee subregions showed SBA present at baseline and 9.2% of subregions exhibited prevalent subchondral BMLs. The adjusted odds ratio (OR) for prevalent SBA for subregions with prevalent BMLs was 18.8 [95% confidence intervals (CI) 15.9-22.4]. A larger BML size was directly associated with an increased risk of prevalent SBA. 195 (2.2%) subregions exhibited incident SBA at follow-up. The adjusted OR for incident SBA was 5.3 [95% CI 3.6-7.7] when compared to subregions without BMLs as the reference.

CONCLUSIONS

Prevalent and incident SBA is strongly associated with subchondral BMLs in the same subregion. One explanation for the presence and development of SBA is subchondral remodeling due to increased stress, which is reflected as BMLs on MRI.

MRI-detected subchondral bone marrow signal alterations of the knee joint: terminology, imaging appearance, relevance and radiological differential diagnosis

OBJECTIVE

To discuss terminology, radiological differential diagnoses and significance of magnetic resonance imaging (MRI)-detected subchondral bone marrow lesions (BMLs) of the knee joint.

METHODS

An overview of the published literature is presented. In addition, the radiological appearance and differential diagnosis of subchondral signal alterations of the knee joint are discussed based on expert consensus. A recommendation for terminology is provided and the relevance of these imaging findings for osteoarthritis (OA) research is emphasized.

RESULTS

A multitude of differential diagnoses of subchondral BMLs may present with a similar aspect and signal characteristics. For this reason it is crucial to clearly and specifically define the type of BML that is being assessed and to use terminology that is appropriate to the condition and the pathology. In light of the currently used terminology, supported by histology, it seems appropriate to apply the widely used term "bone marrow lesion" to the different entities of subchondral signal alterations and in addition to specifically and precisely define the analyzed type of BML. Water sensitive sequences such as fat suppressed T2-weighted, proton density-weighted, intermediate-weighted fast spin echo or short tau inversion recovery (STIR) sequences should be applied to assess non-cystic BMLs as only these sequences depict the lesions to their maximum extent. Assessment of subchondral non-cystic ill-defined BMLs on gradient echo-type sequences should be avoided as they will underestimate the size of the lesion. Differential diagnoses of OA related BMLs include traumatic bone contusions and fractures with or without disruption of the articular surface. Osteonecrosis and bone infarcts, inflammation, tumor, transient idiopathic bone marrow edema, red marrow and post-surgical alterations should also be considered.

CONCLUSION

Different entities of subchondral BMLs that are of relevance in the context of OA research may be distinguished by specific imaging findings, patient characteristics, symptoms, and history and are discussed in this review.

Use of routine clinical multimodality imaging in a rabbit model of osteoarthritis--part I

OBJECTIVE

To evaluate in vivo the evolution of osteoarthritis (OA) lesions temporally in a rabbit model of OA with clinically available imaging modalities: computed radiography (CR), helical single-slice computed tomography (CT), and 1.5 tesla (T) magnetic resonance imaging (MRI).

METHODS

Imaging was performed on knees of anesthetized rabbits [10 anterior cruciate ligament transection (ACLT) and contralateral sham joints and six control rabbits] at baseline and at intervals up to 12 weeks post-surgery. Osteophytosis, subchondral bone sclerosis, bone marrow lesions (BMLs), femoropatellar effusion and articular cartilage were assessed.

RESULTS

CT had the highest sensitivity (90%) and specificity (91%) to detect osteophytes. A significant increase in total joint osteophyte score occurred at all time-points post-operatively in the ACLT group alone. BMLs were identified and occurred most commonly in the lateral femoral condyle of the ACLT joints and were not identified in the tibia. A significant increase in joint effusion was present in the ACLT joints until 8 weeks after surgery. Bone sclerosis or cartilage defects were not reliably assessed with the selected imaging modalities.

CONCLUSION

Combined, clinically available CT and 1.5 T MRI allowed the assessment of most of the characteristic lesions of OA and at early time-points in the development of the disease. However, the selected 1.5 T MRI sequences and acquisition times did not permit the detection of cartilage lesions in this rabbit OA model.

Temporal assessment of bone marrow lesions on magnetic resonance imaging in a canine model of knee osteoarthritis: impact of sequence selection

OBJECTIVE

To assess the evolution of bone marrow lesions (BMLs) in a canine model of knee osteoarthritis (OA) using three different magnetic resonance imaging (MRI) sequences.

DESIGN

Three MRI sequences [coronal, T1-weighted three-dimensional fast gradient recalled echo (T1-GRE), sagittal fat-suppressed 3D spoiled gradient echo at a steady state (SPGR), and sagittal T2-weighted fast spin echo with fat saturation (T2-FS)] were performed at baseline, and at week 4, 8 and 26 in five dogs following transection of the anterior cruciate ligament. The same reader scored (0-3) subchondral BMLs twice, in blinded conditions, according to their extent in nine joint subregions, for all imaging sessions, and independently on the three MRI sequences. Correlation coefficients and Bland-Altman plots evaluated intra-reader repeatability. Readings scores were averaged and the nine subregions were summed to generate global BML scores.

RESULTS

BMLs were most prevalent in the central and medial portions of the tibial plateau. Intra-reader repeatability was good to excellent for each sequence (r(s)=0.87-0.97; P<0.001). Maximal intra-reader variability (24%) was reached on T2-FS and was associated to higher scores (P<0.05). Global BML scores increased similarly on all three sequences until week 8 (P<0.05). At week 26, score on T2-FS was decreased, being lower when compared to T1-GRE and SPGR (P<0.05).

CONCLUSION

In this canine OA model, the extent of BMLs varies in time on different MRI sequences. Until the complex nature of these lesions is fully resolved, it is suggested that to accurately assess the size and extent of BMLs, a combination of different sequences should be used.

Osteophytosis, subchondral bone sclerosis, joint effusion and soft tissue thickening in canine experimental stifle osteoarthritis: comparison between 1.5 T magnetic resonance imaging and computed radiography

OBJECTIVE

To compare use of 1.5 T magnetic resonance imaging (MRI) and computed radiography (CR) for morphologic and temporal evaluation of osteophytosis, subchondral sclerosis, joint effusion, and synovial thickening in experimentally induced canine stifle osteoarthritis (OA).

STUDY DESIGN

Prospective study.

ANIMALS

Dogs (n=8).

METHODS

CR (mediolateral and caudocranial projections) and MRI (dorsal 3D T1-weighted gradient echo, sagittal 3D SPGR and T2-weighted fast spin echo with fat saturation) were performed at baseline (n=8) and at week 4 (n=5), week 8 (n=8), and week 26 (n=5) after cranial cruciate ligament transection. Osteophytosis, subchondral bone sclerosis, and joint effusion were scored on CR and MRI, and synovial thickening on MRI.

RESULTS

MRI was more sensitive than CR for detection of osteophytosis and could better discriminate joint effusion from soft tissue thickening, although scores for these variables strongly correlated between modalities (rho=0.94 [osteophytosis] and 0.80 [effusion]; P<.001). Scores for subchondral bone sclerosis also correlated (rho=0.54, P<.004), although this variable may have been over interpreted on CR. Joint effusion and synovial thickening peaked at week 8, before partially regressing at week 26. Conversely, osteophytosis and sclerosis progressed semi-linearly over 26 weeks.

CONCLUSION

MRI is more sensitive than radiography in assessing onset and progression of osteophytosis in canine experimental stifle OA and provides enhanced discrimination between joint effusion and synovial thickening.

CLINICAL RELEVANCE

MRI is as a more powerful imaging modality that should be increasingly used in animals to assess the joint related effects of disease-modifying OA drugs.