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

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.

Synovial fluid proteome profile of surgical versus chemical induced osteoarthritis in rabbits

BACKGROUND

Animal models are significant for understanding human osteoarthritis (OA). This study compared the synovial fluid proteomics changes in surgical and chemical induced OA models.

METHODS

Thirty rabbits either had anterior cruciate ligament transection (ACLT) procedure or injected intra-articularly with monosodium iodoacetate (MIA, 8 mg) into the right knee. The joints were anatomically assessed, and the synovial fluid proteins analyzed using two-dimensional polyacrylamide gel electrophoresis (2DGE) and MALDI TOF/TOF mass spectrometry analysis at 4, 8 and 12 weeks. The proteins' upregulation and downregulation were compared with control healthy knees.

RESULTS

Seven proteins (histidine-rich glycoprotein, beta-actin-like protein 2 isoform X1, retinol-binding protein-4, alpha-1-antiproteinase, gelsolin isoform, serotransferrin, immunoglobulin kappa-b4 chain-C-region) were significantly expressed by the surgical induction. They characterized cellular process (27%), organization of cellular components or biogenesis (27%), localization (27%) and biological regulation (18%), which related to synovitis, increased cellularity, and subsequently cartilage damage. Three proteins (apolipoprotein I-IV precursor, serpin peptidase inhibitor and haptoglobin precursor) were significantly modified by the chemical induction. They characterized stimulus responses (23%), immune responses (15%), biological regulations (15%), metabolism (15%), organization of cellular components or biogenesis (8%), cellular process (8%), biological adhesions (8%) and localization (8%), which related to chondrocytes glycolysis/death, neovascularization, subchondral bone necrosis/collapse and inflammation.

CONCLUSIONS

The surgical induced OA model showed a wider range of protein changes, which were most upregulated at week 12. The biological process proteins expressions showed the chemical induced joints had slower OA progression compared to surgical induced joints. The chemical induced OA joints showed early inflammatory changes, which later decreased.

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.

Comparison of bone and articular cartilage changes in osteoarthritis: a micro-computed tomography and histological study of surgically and chemically induced osteoarthritic rabbit models

BACKGROUND

Osteoarthritis (OA) is a multifaceted condition that affects both the subchondral bones and the articular cartilage. Animal models are widely used as an effective supplement and simulation for human OA studies in investigating disease mechanisms and pathophysiology. This study is aimed to evaluate the temporal changes of bone and cartilage in surgically and chemically induced osteoarthritis using micro-computed tomography and histology.

METHODS

Thirty rabbits underwent either anterior cruciate ligament transection (ACLT) procedure or injected intraarticularly with monosodium iodoacetate (MIA, 8 mg) at the right knee joint. The subchondral bones were scanned via micro-CT, and articular cartilage was assessed histologically at 4-, 8- and 12-week post-induction.

RESULTS

Based on bone micro-architecture parameters, the surgically induced group revealed bone remodelling processes, indicated by increase bone volume, thickening of trabeculae, reduced trabecular separation and reduced porosity. On the other hand, the chemically induced group showed active bone resorption processes depicted by decrease bone volume, thinning of trabeculae, increased separation of trabecular and increased porosity consistently until week 12. Histologically, the chemically induced group showed more severe articular cartilage damage compared to the surgically induced group.

CONCLUSIONS

It can be concluded that in the ACLT group, subchondral bone remodelling precedes articular cartilage damage and vice versa in the MIA group. The findings revealed distinct pathogenic pathways for both induction methods, providing insight into tailored therapeutic strategies, as well as disease progression and treatment outcomes monitoring.

Chondroprotective Effects of a Standardized Extract (KBH-JP-040) from Kalopanax pictus, Hericium erinaceus, and Astragalus membranaceus in Experimentally Induced In Vitro and In Vivo Osteoarthritis Models

The aim of this study was to investigate the chondroprotective effect of a standardized extract (KBH-JP-040) of the Korean traditional herbs Kalopanax pictus Castor-Aralia, Hericium erinaceus (Bull.) Persoon, and Astragalus membranaceus Schischkin on in vivo and in vitro osteoarthritis (OA) models. Cultured rat chondrocytes were pre-treated with KBH-JP-040 (50, 100 and 200 μg/mL) for 1 h, then recombinant human IL-1α (rhIL-1α) for 24 h. For the in vivo model, rabbits (n = 60) were equally divided into experimental groups: normal control (NC), a collagenase-induced OA group, and OA groups treated with KBH-JP-040 (75, 100, and 150 mg/kg body weight) and celecoxib (Cx, 100 mg/kg) orally for 28 days. Treatment with KBH-JP-040 significantly attenuated inflammatory cytokines and matrix metalloproteinases (MMPs), suppressed the expression of IκBα, NF-κB, and JNK/p38 mitogen-activated protein (MAP) kinase, and upregulated aggrecan and collagen type-II expression in rhIL-1α-stimulated chondrocytes. Furthermore, the serum and synovial levels of inflammatory cytokines of rabbits also decreased in the treatment groups when compared with the OA group. Improved magnetic resonance imaging and histopathological findings further confirmed the therapeutic efficacy of KBH-JP-040 against OA. In conclusion, these results indicate that KBH-JP-040 possesses chondroprotective effects, suppressing inflammation and MMPs, and downregulating IκBα, NF-κB, and JNK/p38 MAP kinase-signaling pathways. This might be a potential therapeutic candidate for OA treatment.

Sustained intra-cartilage delivery of low dose dexamethasone using a cationic carrier for treatment of post traumatic osteoarthritis

Disease-modifying osteoarthritis drugs (DMOADs) should reach their intra-tissue target sites at optimal doses for clinical efficacy. The dense, negatively charged matrix of cartilage poses a major hindrance to the transport of potential therapeutics. In this work, electrostatic interactions were utilised to overcome this challenge and enable higher uptake, full-thickness penetration and enhanced retention of dexamethasone (Dex) inside rabbit cartilage. This was accomplished by using the positively charged glycoprotein avidin as nanocarrier, conjugated to Dex by releasable linkers. Therapeutic effects of a single intra-articular injection of low dose avidin-Dex (0.5 mg Dex) were evaluated in rabbits 3 weeks after anterior cruciate ligament transection (ACLT). Immunostaining confirmed that avidin penetrated the full cartilage thickness and was retained for at least 3 weeks. Avidin-Dex suppressed injury-induced joint swelling and catabolic gene expression to a greater extent than free Dex. It also significantly improved the histological score of cell infiltration and morphogenesis within the periarticular synovium. Micro-computed tomography confirmed the reduced incidence and volume of osteophytes following avidin-Dex treatment. However, neither treatment restored the loss of cartilage stiffness following ACLT, suggesting the need for a combinational therapy with a pro-anabolic factor for enhancing matrix biosynthesis. The avidin dose used caused significant glycosaminoglycan (GAG) loss, suggesting the use of higher Dex : avidin ratios in future formulations, such that the delivered avidin dose could be much less than that shown to affect GAGs. This charge-based delivery system converted cartilage into a drug depot that could also be employed for delivery to nearby synovium, menisci and ligaments, enabling clinical translation of a variety of DMOADs.

Protective effect of zoledronic acid on articular cartilage and subchondral bone of rabbits with experimental knee osteoarthritis

Subchondral bone reabsorption and remodeling are responsible for the initiation and progression of osteoarthritis (OA). Zoledronic acid (ZOL), a third-generation bisphosphonate (BIS), is an inhibitor of bone reabsorption. However, the intervention effect of ZOL on OA has not been fully characterized and remains to be directly demonstrated in animal experiments. The present study examined the microscopic and macroscopic changes in the anterior cruciate ligament transection (ACLT) model of OA in rabbits and evaluated the effects of ZOL on cartilage degeneration and subchondral bone loss. A total of 32 New Zealand white rabbits were randomly divided into four groups: High-, medium- and low-dose ZOL groups, which received an intravenous injection of 250, 50 and 10 µg/kg ZOL, respectively, after modeling, as well as an untreated group. The bone mineral density (BMD) of the knee joint was evaluated by dual-energy X-ray absorptiometry scanning immediately after modeling and at 4 and 8 weeks. At week 8, quantitative measurement of cartilage was performed by a specialized magnetic resonance imaging (MRI) technique, including three-dimensional fat-suppressed spoil gradient-recalled sequence and T2 mapping. The rabbits were sacrificed by air embolism after anesthesia and both knee joints were harvested and evaluated by general and histological observation. Toluidine blue and hematoxylin and eosin staining were used to assess histological changes in the articular cartilage. Quantitative analysis of cartilage histopathology was performed according to the Mankin scoring system. The BMD of ACLT joints dropped after modeling, which was effectively suppressed by ZOL at the high and medium dose but not the low dose. MRI scans demonstrated that in the untreated group, articular cartilages on ACLT knees were thinner than those on normal knees. The high dose of ZOL preserved the cartilage tissue thickness more efficiently than the medium and low doses. Observation of specimens and pathological slices revealed that the articular cartilage degeneration in the high-dose ZOL group was lightest, while that in the medium- and low-dose ZOL group was moderate, and the untreated group exhibited the most severe defect. The untreated group had the highest Mankin score, whereas the high-dose ZOL group had the lowest score. In conclusion, ZOL increased the subchondral bone density, improved the microstructure and reduced the degeneration of articular cartilage in OA according to morphological as well as quantitative observation. ZOL exerted significant chondroprotective effects in a dose-dependent manner. A favorable chondroprotective effect was induced at the dose of 250 µg/kg. ZOL may represent a novel promising drug to complement the treatment of OA.

Assessment of cortical and trabecular bone changes in two models of post-traumatic osteoarthritis

Subchondral bone is thought to play a significant role in the initiation and progression of the post-traumatic osteoarthritis. The goal of this study was to document changes in tibial and femoral subchondral bone that occur as a result of two lapine models of anterior cruciate ligament injury, a modified ACL transection model and a closed-joint traumatic compressive impact model. Twelve weeks post-injury bones were scanned via micro-computed tomography. The subchondral bone of injured limbs from both models showed decreases in bone volume and bone mineral density. Surgical transection animals showed significant bone changes primarily in the medial hemijoint of femurs and tibias, while significant changes were noted in both the medial and lateral hemijoints of both bones for traumatic impact animals. It is believed that subchondral bone changes in the medial hemijoint were likely caused by compromised soft tissue structures seen in both models. Subchondral bone changes in the lateral hemijoint of traumatic impact animals are thought to be due to transmission of the compressive impact force through the joint. The joint-wide bone changes shown in the traumatic impact model were similar to clinical findings from studies investigating the progression of osteoarthritis in humans.

Intra-articular delivery of adipose derived stromal cells attenuates osteoarthritis progression in an experimental rabbit model

Introduction

Cell therapy is a rapidly growing area of research for the treatment of osteoarthritis (OA). This work is aimed to investigate the efficacy of intra-articular adipose-derived stromal cell (ASC) injection in the healing process on cartilage, synovial membrane and menisci in an experimental rabbit model.

Methods

The induction of OA was performed surgically through bilateral anterior cruciate ligament transection (ACLT) to achieve eight weeks from ACLT a mild grade of OA. A total of 2 × 10⁶ and 6 × 10⁶ autologous ASCs isolated from inguinal fat, expanded in vitro and suspended in 4% rabbit serum albumin (RSA) were delivered in the hind limbs; 4% RSA was used as the control. Local bio-distribution of the cells was verified by injecting chloro-methyl-benzamido-1,1'-dioctadecyl-3,3,3'3'-tetra-methyl-indo-carbocyanine per-chlorate (CM-Dil) labeled ASCs in the hind limbs. Cartilage and synovial histological sections were scored by Laverty's scoring system to assess the severity of the pathology. Protein expression of some extracellular matrix molecules (collagen I and II), catabolic (metalloproteinase-1 and -3) and inflammatory (tumor necrosis factor- α) markers were detected by immunohistochemistry. Assessments were carried out at 16 and 24 weeks.

Results

Labeled-ASCs were detected unexpectedly in the synovial membrane and medial meniscus but not in cartilage tissue at 3 and 20 days from ASC-treatment. Intra-articular ASC administration decreases OA progression and exerts a healing contribution in the treated animals in comparison to OA and 4% RSA groups.

Conclusions

Our data reveal a healing capacity of ASCs in promoting cartilage and menisci repair and attenuating inflammatory events in synovial membrane inhibiting OA progression. On the basis of the local bio-distribution findings, the benefits obtained by ASC treatment could be due to a trophic mechanism of action by the release of growth factors and cytokines.

A review of translational animal models for knee osteoarthritis

Knee osteoarthritis remains a tremendous public health concern, both in terms of health-related quality of life and financial burden of disease. Translational research is a critical step towards understanding and mitigating the long-term effects of this disease process. Animal models provide practical and clinically relevant ways to study both the natural history and response to treatment of knee osteoarthritis. Many factors including size, cost, and method of inducing osteoarthritis are important considerations for choosing an appropriate animal model. Smaller animals are useful because of their ease of use and cost, while larger animals are advantageous because of their anatomical similarity to humans. This evidence-based review will compare and contrast several different animal models for knee osteoarthritis. Our goal is to inform the clinician about current research models, in order to facilitate the transfer of knowledge from the "bench" to the "bedside."

Early-term effect of adult chondrocyte transplantation in an osteoarthritis animal model

In this study, we investigated the efficacy of the transplantation of autologous articular chondrocytes seeded onto a hyaluronan-based scaffold, known as Hyaff(®)-11, on the treatment of early cartilage lesions in a rabbit osteoarthritis (OA) model. The hypothesis of the study was that this treatment could enhance cartilage repair after OA induction. OA was surgically induced by Anterior Cruciate Ligament Transection (ACLT) in thirty rabbits. Animals were divided into three groups, according to treatment: group 1: ACLT; group 2: Chondrocytes+Hyaff-11; and group 3: Hyaff-11 alone. The animals were euthanized, respectively, at 3 and 6 months after the treatment. Histomorphometrical analyses were performed by means of fibrillation index, cartilage thickness, and subchondral bone thickness evaluations. Histological appearance was scored according to Modified Kraus' Mankin and Osteoarthritis Research Society International (OARSI) scores. Immunohistochemical analyses were carried out for type I and II collagens, MMP-1, and MMP-3. A comparison between groups and follow-up for each outcome was performed with the general linear model with Sidak correction. Histomorphometrical evaluations at 3 and 6 months demonstrated that OA lesions became significantly worse followed by Hyaff-11 treatment, whereas Chondrocytes+Hyaff-11 treatment had the best overall subjective grade. Overall raw histological scores demonstrated a significant improvement with chondro-hyaluronic acid (HA) treatment at 3 months compared with HA in cartilage repair processes. Immunohistochemical analyses displayed a strong positivity for type II collagen in the Chondrocytes+Hyaff-11group at 3 months compared with the HA group. No staining was observed in MMP-3 expression in this group at any experimental point. The use of Chondrocytes+Hyaff-11 for the treatment of early OA lesions produced, already at 3 months, a repair tissue showing better macroscopic, histological, and immunohistochemical results than those observed after Hyaff-11 treatment. Thus, the transplantation of Chondrocytes+Hyaff-11 would seem to be advocated in the very early stage of the OA disease when a precocious action is mandatory.

Imaging longitudinal changes in articular cartilage and bone following doxycycline treatment in a rabbit anterior cruciate ligament transection model of osteoarthritis

OBJECTIVE

The development of osteoarthritis following traumatic anterior cruciate ligament (ACL) injury is well established. However, few reliable indicators of early osteoarthritic changes have been established, which has limited the development of effective therapies. T(1ρ) and T(2) mapping techniques have the ability to provide highly accurate and quantitative measurements of articular cartilage degeneration in vivo. Relating these cartilaginous changes to high-resolution bone-densitometric evaluations of the late-stage osteoarthritic bone is crucial in elucidating the mechanisms of development of traumatic osteoarthritis (OA) and potential therapies for early- or late-stage intervention.

METHODS

Twelve rabbits were monitored with in vivo magnetic resonance imaging (MRI) scans following ACL transection surgery with a contralateral leg sham operation. Six of the rabbits were treated with oral doxycycline for the duration of the experiment. At 12 weeks, the excised knees from three animals from each group (n=6 overall) were subjected to micro-computed tomography (CT) analysis.

RESULTS

Consistent with previous studies, initial elevations in T(1ρ) and T(2) values in ACL-transected animals were observed with relative normalization towards values see in sham-operated legs over the 12-week study. This biphasic pattern could hold diagnostic potential to differentiate osteoarthritic cartilage by tracking the relative proportions of T(1ρ) and T(2) values as they rise with inflammation then fall as collagen and proteoglycan loss leads to further dehydration. The addition of doxycycline resulted in inconclusive, yet potentially interesting, cartilaginous changes in several compartments of the rabbit legs. Micro-CT studies demonstrated decreased bone densitometrics in ACL-transected knees. Correlation studies suggest that the cartilaginous changes may be associated with some aspects of bony change and the development of OA.

CONCLUSION

We conclude that there are definite relationships between cartilaginous changes as seen on MRI and late-stage microstructural bony changes after traumatic ACL injury in rabbits. In addition, doxycycline may show promise in mitigating early-stage cartilage damage that may serve to lessen late-stage osteoarthritic changes. This study demonstrates the ability to track OA progression and therapeutic efficacy with imaging modalities in vivo.

Evaluation of bee venom and hyaluronic acid in the intra-articular treatment of osteoarthritis in an experimental rabbit model

The aim of this study was to investigate bee venom and hyaluronic acid in the intra-articular treatment of osteoarthritis in an experimental rabbit model. Forty-five rabbits were used and they were randomly divided into three groups (BVI, BVII, and HA) and each group was divided to two subgroups to evaluate the radiologic, magnetic resonance imaging, histopathologic, and biochemical evaluation in post treatment second week (a) and twelfth week (b). Radiologically, a significant difference was observed in the HA group (P<0.05). The MRI evaluation of at any time in group BVI(b) was found to be different. No significant differences were seen between the groups, biochemically. Histopathologically, cellularity, and orthochromasia was evident with Safranin-O in the BVI(b) and BVII(a); adhesions were seen in the BVII(a) group and clustering of chondrocyte in the HA(b) group were found to be different. Consequently, intra-articular application of HA and BV for experimental model of osteoarthritis has no significant influence upon recovery after therapy.

Significance of the serum CTX-II level in an osteoarthritis animal model: a 5-month longitudinal study

OBJECTIVE

The aim of this study was to investigate the clinical value of serum measurement of C-telopeptide of type II collagen (CTX-II). In correlation with late stages of osteoarthritis (OA) evaluated with histological assessment, the evolution of serum CTX-II concentration was followed during a 20-week longitudinal study in rabbit anterior cruciate ligament transection (ACLT) OA model in adult and growing animals.

METHODS

OA was induced in five adult and nine growing rabbits. Four adult and four young rabbits were unoperated. Serum sampling was made at week 0, 1, 2, 3, 4, 6, 8, 10, 12, 14, 16 and 20 after the surgery in all rabbits. Animals were euthanized 20 weeks after the surgery. Serum CTX-II levels were analyzed with a recently available enzyme-linked immunosorbent assay (ELISA) kit, the protocol of which has been modified to increase the sensitivity of the test.

RESULTS

Significant differences for the CTX-II levels at W3, W6, W8, W10, W12, W14, W16 and W20 were observed between the adult ACLT and the control groups. A negative correlation between CTX-II levels and cartilage thickness of the medial compartment of the knee at W8, W10, W12 and a positive correlation between the CTX-II levels and the histomorphological score of the medial compartment of the knee at W3, W6, W8, W10, W12 were noted in adult animals. In young animals, operated or not, we observed high CTX-II levels at the beginning of the study, which decreased until the end.

CONCLUSION

Our results suggest the interest of the serum CTX-II monitoring for the OA progression and the relevance of the multiple time point analysis of this biomarker. Moreover, they address the question of the importance of correctly choosing the age of the animals used in the pre-clinical studies of OA.

The OARSI histopathology initiative - recommendations for histological assessments of osteoarthritis in the rabbit

AIM

The primary goal of this body of work is to suggest a standardized system for histopathological assessment of experimental surgical instability models of osteoarthritis (OA) in rabbits, building on past experience, to achieve comparability of studies from different centres. An additional objective is to review methodologies that have been employed in the past for assessing OA in rabbits with particular reference to the surgical anterior cruciate ligament transection (ACLT) model.

METHODS

A panel of scientists and clinician-scientists with recognized expertise in assessing rabbit models of OA reviewed the literature to provide a critical appraisal of the methods that have been employed to assess both macroscopic and microscopic changes occurring in rabbit joint tissues in experimental OA. In addition, a validation of the proposed histologic histochemical grading system was performed.

RESULTS

The ACLT variant of the surgical instability model in skeletally mature rabbits is the variation most capable of reproducing the entire range of cartilage, synovial and bone lesions recognized to be associated with OA. These lesions can be semiquantitatively graded using macroscopic and microscopic techniques. Further, as well as cartilage lesions, this ACLT model can produce synovial and bone lesions similar to that of human OA.

CONCLUSIONS

The ACLT variant of the surgical instability model in rabbits is a reproducible and effective model of OA. The cartilage lesions in this model and their response to therapy can be graded according to an adapted histological and histochemical grading system, though also this system is to some extent subjective and, thus, neither objective nor entirely reproducible.

Fat-suppressed spoiled gradient-recalled imaging of equine metacarpophalangeal articular cartilage

The purpose was to evaluate the capacity of 1.5 T magnetic resonance (MR) imaging to assess articular cartilage in racehorses with naturally occurring metacarpophalangeal joint osteoarthritis. A sagittal, three-dimensional spoiled gradient-recalled echo (SPGR) with fat saturation (FS) sequence was acquired ex vivo on 20 joints. Following joint dissection, specific areas on the third metacarpal condyle were designated for subsequent sampling for histologic cartilage thickness measurement and modified Mankin scoring. Cartilage thickness was measured and cartilage signal intensity was also graded (0-3) on MR images at these selected metacarpal sites. Cartilage structure was graded (0-3) macroscopically and on MR images by two examiners in defined subregions of the proximal phalanx, third metacarpal, and proximal sesamoid bones. There was good precision (mean error 0.11 mm) and moderate correlation (r = 0.44; P < 0.0001) of cartilage thickness measurements between MR images (0.90 +/- 0.17mm) and histology (0.79 +/- 0.16 mm). There was moderate correlation between modified Mankin histologic score and signal intensity of cartilage (r = 0.36; P < 0.01) or MR cartilage structure assessment (r = 0.49, P > 0.001) on SPGR-FS. The sensitivity to detect full-thickness cartilage erosion on MR was only moderate (0.56), and these lesions were often underestimated, particularly when linear in nature. However, the specificity to detect such lesions on MR was high (0.92). While few limitations were identified, the use of a clinically applicable SPGR-FS sequence allows a reasonably accurate method to assess structural changes affecting the articular cartilage of the equine metacarpophalangeal joint.

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.