Ultrashort Echo Time Quantitative Magnetic Resonance Imaging of the Cruciate Ligaments in Normal Beagles.

OBJECTIVE: The aim of this study was to provide normative ultrashort echo time magnetic resonance imaging (UTE MRI) data of the patellar ligament (PL), cranial cruciate ligament (CrCL) and caudal cruciate ligament (CdCL) in non-lame Beagles. STUDY DESIGN: Eight stifles from four subjects obtained immediately postmortem were imaged using UTE MRI in the true sagittal plane. Regions of interest were drawn manually and the total (T2*), short T2* (T2*S) and long T2* (T2*L) values of the signal decay were calculated to evaluate the bound and free water components of the tendon. The T2*S, T2*L and T2* values were compared between the PL, CrCL and CdCL RESULTS: The mean and standard deviation of T2*S, T2*L and T2* were as follows: 0.54 ± 0.13, 4.65 ± 1.08 and 8.35 ± 0.82 ms for the PL; 0.46 ± 0.14, 5.99 ± 0.52 and 8.88 ± 0.4 ms for the CrCL and 0.41 ± 0.13, 7.06 ± 0.57 and 9.26 ± 0.18 ms for the CdCL. Significant differences were found between the T2*L component of the PL and each CrCL/CdCL and a smaller difference was noted between the T2*L of the CrCL and CdCL (p = 0.05). No difference of the T2*S value was found between any of the ligaments. CONCLUSION: Establishing normative UTE data of the canine stifle is valuable for comparison in future studies in which normal and damaged ligaments may be evaluated, particularly in those affected limbs in which no instability is identified on physical examination in which normal and damaged ligaments may be evaluated.

Correlation of Arthroscopic Grading and Optical Coherence Tomography as Markers of Early Repair and Predictors of Later Healing Evident on MRI and Histomorphometric Assessment of Cartilage Defects Implanted with Chondrocytes Overexpressing IGF-I.

OBJECTIVE: Injury of articular cartilage is common, and due to the poor intrinsic capabilities of chondrocytes, it can precipitate joint degradation and osteoarthritis (OA). Implantation of autologous chondrocytes into cartilaginous defects has been used to bolster repair. Accurate assessment of the quality of repair tissue remains challenging. This study aimed to investigate the utility of noninvasive imaging modalities, including arthroscopic grading and optical coherence tomography (OCT) for assessment of early cartilage repair (8 weeks), and MRI to determine long-term healing (8 months). DESIGN: Large (15 mm diameter), full-thickness chondral defects were created on both lateral trochlear ridges of the femur in 24 horses. Defects were implanted with autologous chondrocytes transduced with rAAV5-IGF-I, autologous chondrocytes transduced with rAAV5-GFP, naïve autologous chondrocytes, or autologous fibrin. Healing was evaluated at 8 weeks post-implantation using arthroscopy and OCT, and at 8 months post-implantation using MRI, gross pathology, and histopathology. RESULTS: OCT and arthroscopic scoring of short-term repair tissue were significantly correlated. Arthroscopy was also correlated with later gross pathology and histopathology of repair tissue at 8 months post-implantation, while OCT was not correlated. MRI was not correlated with any other assessment variable. CONCLUSIONS: This study indicated that arthroscopic inspection and manual probing to develop an early repair score may be a better predictor of long-term cartilage repair quality following autologous chondrocyte implantation. Furthermore, qualitative MRI may not provide additional discriminatory information when assessing mature repair tissue, at least in this equine model of cartilage repair.

Age and Sex Comparison of the Canine Supraspinatus Tendon Using Quantitative Magnetic Resonance Imaging T2 Mapping.

OBJECTIVE: The normal canine supraspinatus tendon has properties commonly attributed to damage such as core hyperintensity and increased width. Little is published regarding the normal tendon, including how senescent changes and sex differences may affect the appearance. Conventional magnetic resonance imaging (MRI) techniques provide subjective analysis of tendons based on observer assessment of signal intensity and appearance. Quantitative MRI (qMRI) techniques such as T2 mapping provide an objective comparison of collagen orientation with analysis of a decay constant, T2. This study investigates age and sex related changes in the canine supraspinatus tendon using the qMRI technique of T2 mapping. STUDY DESIGN: In this study, 34 tendons of clinically sound male and female dogs (0.6-13 years) were imaged using qMRI T2 mapping techniques. Sagittal plane T2 maps of the supraspinatus tendon were depth-normalized, and profiles compared using two separate four-parameter logistic equations describing T2 mapping profiles as sigmoidal curves. Combined parameters evaluated included range of T2 values, curve steepness, vertical curve shift, lower bound of T2, upper bound of T2 and horizontal curve shift. RESULTS: A significant reduction in the most central portion of the supraspinatus tendon was found for every increased year in age (-1.56 ± 0.47 milliseconds [-2.56, -0.56, p = 0.004]). No significant difference in curve parameters was found between sexes. CONCLUSION: The reduction in T2 with age suggests a senescent change may be anticipated with the canine supraspinatus tendon.

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.

Assessment of osteoarthritis functional outcomes and intra-articular injection volume in the rat anterior cruciate ligament transection model.

The rat surgical anterior cruciate ligament transection (ACLT) model is commonly used to investigate intra-articular osteoarthritis (OA) therapies, and histological assessment is often the primary outcome measure. However, histological changes do not always correlate well with clinical outcomes. Therefore, this study evaluated functional outcomes in the rat surgical ACLT model and compared intra-articular injection volumes ranging from 20 to 50 µl. Unilateral ACLT was surgically induced and static weight-bearing, mechanical allodynia, motor function, and gait were assessed in four groups of male, Sprague-Dawley rats (n = 6 per group). Intra-articular injections of 20 µl Dulbecco's phosphate-buffered saline (DPBS), 50 µl DPBS, or 50 µl of synthetic biomimetic boundary lubricant were administered once weekly for 3 weeks postoperatively. Structural changes were evaluated histologically at 20 weeks. Rat cadaver knees were injected with 20, 30, 40, or 50 µl of gadolinium solutions and were imaged using magnetic resonance imaging (MRI). Static weight-bearing, mechanical allodynia, and gait parameters in ACLT groups revealed differences from baseline and naïve controls for 4 weeks post-ACLT; however, these differences did not persist beyond 6 weeks. Different intra-articular DPBS injection volumes did not result in functional or histological changes; however, peri-articular leakage was documented via MRI following 50, 40, and 30 µl but not 20 µl gadolinium injections. Statement of clinical significance: Differences in functional parameters were predominantly restricted to early, postoperative changes in the rat surgical ACLT model despite evidence of moderate histologic OA at 20 weeks. Injection volumes of 20-30 µl are more appropriate for investigating intra-articular therapies in the rat knee.

Differences in the magnetic resonance imaging parameter T2* may be identified during the course of canine patellar tendon healing: a pilot study.

BACKGROUND: Previous studies have utilized ultrashort echo (UTE) magnetic resonance imaging (MRI), and derived T2* maps, to evaluate structures with highly ordered collagen structures such as tendon. T2* maps may provide a noninvasive means to assess tendon damage and healing. This pilot study evaluated the longitudinal relationship of an induced mechanical strain on the patellar tendon with corresponding UTE T2* metrics, histologic and biomechanical evaluation at two post-operative time points. METHODS: A total of 27 patellar tendons in male Beagles were surgically subjected to stretching by a small diameter (SmD) or a large diameter (LgD) diameter rod to induce damage due to strain, and evaluated at 4- and 8-week intervals using quantitative MRI (qMRI), biomechanical testing, and histology. A separate set of 16 limbs were used as controls. RESULTS: The tendons experienced a 67% and 17% prolongation of short T2* values as compared to controls at 4 and 8 weeks post-operatively, respectively. Histologic analysis displayed a trend of increased collagen disruption at 4 weeks followed by presence of greater organization at 8 weeks. Biomechanical evaluation found a reduction of tendon modulus and failure strain at both time points, and an increase in cross-sectional area at 4 weeks as compared to controls. CONCLUSIONS: These findings display tendon healing in response to an imposed strain and present the utility of qMRI to evaluate longitudinal differences of patellar tendon T2* values in a model of induced subclinical tendon damage. The qMRI technique of UTE provides a means to non-invasively evaluate the healing process of a mechanically damaged tendon.

Integrin α10ß1-Selected Mesenchymal Stem Cells Mitigate the Progression of Osteoarthritis in an Equine Talar Impact Model.

BACKGROUND: Early intervention with mesenchymal stem cells (MSCs) after articular trauma has the potential to limit progression of focal lesions and prevent ongoing cartilage degeneration by modulating the joint environment and/or contributing to repair. Integrin α10ß1 is the main collagen type II binding receptor on chondrocytes, and MSCs that are selected for high expression of the α10 subunit have improved chondrogenic potential. The ability of α10ß1-selected (integrin α10high) MSCs to protect cartilage after injury has not been investigated. PURPOSE: To investigate integrin α10high MSCs to prevent posttraumatic osteoarthritis in an equine model of impact-induced talar injury. STUDY DESIGN: Controlled laboratory study. METHODS: Focal cartilage injuries were created on the tali of horses (2-5 years, n = 8) by using an impacting device equipped to measure impact stress. Joints were treated with 20 × 106 allogenic adipose-derived α10high MSCs or saline vehicle (control) 4 days after injury. Synovial fluid was collected serially and analyzed for protein content, cell counts, markers of inflammation (prostaglandin E2, tumor necrosis factor α) and collagen homeostasis (procollagen II C-propeptide, collagen type II cleavage product), and glycosaminoglycan content. Second-look arthroscopy was performed at 6 weeks, and horses were euthanized at 6 months. Joints were imaged with radiographs and quantitative 3-T magnetic resonance imaging. Postmortem examinations were performed, and India ink was applied to the talar articular surface to identify areas of cartilage fibrillation. Synovial membrane and osteochondral histology was performed, and immunohistochemistry was used to assess type I and II collagen and lubricin. A mixed effect model with Tukey post hoc and linear contrasts or paired t tests were used, as appropriate. RESULTS: Integrin α10high MSC-treated joints had less subchondral bone sclerosis on radiographs (P = .04) and histology (P = .006) and less cartilage fibrillation (P = .04) as compared with control joints. On gross pathology, less India ink adhered to impact sites in treated joints than in controls, which may be explained by the finding of more prominent lubricin immunostaining in treated joints. Prostaglandin E2 concentration in synovial fluid and mononuclear cell synovial infiltrate were increased in treated joints, suggesting possible immunomodulation by integrin α10high MSCs. CONCLUSION: Intra-articular administration of integrin α10high MSCs is safe, and evidence suggests that the cells mitigate the effects of joint trauma. CLINICAL RELEVANCE: This preclinical study indicates that intra-articular therapy with integrin α10high MSCs after joint trauma may be protective against posttraumatic osteoarthritis.

T1ρ, T2 mapping, and EPIC-µCT Imaging in a Canine Model of Knee Osteochondral Injury.

The dog is the most commonly used large animal model for the study of osteoarthritis. Optimizing methods for assessing cartilage health would prove useful in reducing the number of dogs needed for a valid study of osteoarthritis and cartilage repair. Twelve beagles had critical-sized osteochondral defects created in the medial femoral condyle of both knees. Eight dogs had T1ρ and T2 magnetic resonance imaging (MRI) performed approximately 6 months after defect creation. Following MRI evaluations, all 12 dogs were humanely euthanatized and cartilage samples were obtained from the medial and lateral femoral condyles, medial and lateral tibial plateaus, trochlear groove, and patella for proteoglycan and collagen quantification. Equilibrium partitioning of an ionic contrast (EPIC)-µCT was then performed followed by the histologic assessment of the knees. Correlations between T1ρ, T2, EPIC-µCT and proteoglycan, collagen, and histology scores were assessed using a multivariate analysis accounting for correlations from samples within the same knee and in the same dog. Pearson's correlation coefficients were calculated to assess the strength of significant relationships. Correlations between µCT values and biochemical or histologic assessment were weak to moderately strong (0.09-0.41; p < 0.0001-0.66). There was a weak correlation between the T2 values and cartilage proteoglycan (-0.32; p = 0.04). The correlation between T1ρ values and cartilage proteoglycan were moderately strong (-0.38; p < 0.05) while the strongest correlation was between the T1ρ values and histological assessment of cartilage with a correlation coefficient of 0.58 (p < 0.0001). These data suggest that T1ρ shows promise for possible utility in the translational study of cartilage health and warrants further development in this species. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:368-377, 2020.

Nonarticular osseous cyst-like lesions of the intermedioradial carpal bone may be incidental magnetic resonance imaging findings in dogs.

As magnetic resonance imaging (MRI) becomes more readily available and more frequently utilized in the assessment of canine carpal lameness, both normal variations and early pathologic conditions must be recognized to optimize patient care and provide accurate diagnosis. On cross sectional studies of the canine carpus, cyst-like lesions have been detected at the dorsolateral aspect of the intermedioradial carpal bone. The cross-sectional imaging and histologic properties of these lesions have not been described. The purpose of this observational study is to evaluate the MRI and histologic features of these cyst-like lesions in a cohort of clinically sound dogs. It was hypothesized that the lesions would show features similar to intraosseous ganglion cysts of the human wrist. Twenty-five cadaveric canine carpi were obtained and a total of 13 lesions were detected on MRI. Based on MRI, six carpi with lesions of varying size and one normal carpus were submitted for histological evaluation. Five of the abnormal carpi had nonarticular cyst-like lesions; one specimen with a positive magnetic resonance image for a cyst-like lesion had no cyst-like lesion on histology. Conspicuity of a medium-size lesion as evaluated on radiographs was poor. Given the presence of these nonarticular cyst-like lesions in a population of clinically sound patients, their clinical importance is uncertain. The development of these lesions may relate to altered mechanics or genetic predispositions, requiring additional study.

Quantitative Magnetic Resonance Imaging and Histological Comparison of Normal Canine Menisci.

OBJECTIVE: The purpose of this observational study was to establish normative data for the canine menisci using magnetic resonance imaging (MRI). METHODS: Ten fresh stifles from five normal male Beagles were obtained from animals with no known lameness. Conventional MRI and ultrashort echo time (UTE) imaging were performed and T2* values calculated. Five stifles were assessed histologically. RESULTS: The caudal horn of the medial meniscus had significantly prolonged T2* values (4.6 ± 1.27 ms; p = 0.002) as compared with the cranial horn of the medial meniscus (3.25 ± 0.86 ms), and the cranial (3.06 ± 0.54 ms) and caudal (3.64 ± 0.72 ms) horns of the lateral meniscus. Histology demonstrated normal tibial, femoral, interior and peripheral meniscal margins, and normal cellularity. The medial meniscus was noted to be obliquely oriented to the scan plane compared with the relatively perpendicular orientation of the lateral meniscus as compared with the bore of the magnet in a limb-extended orientation. CLINICAL SIGNIFICANCE: Variability of MRI UTE T2* is seen in the normal canine meniscus, with prolongation of the caudal horn, medial meniscus. Prolongation may be due to magic angle effects, as the medial meniscus of the Beagle is not perpendicular to the axis of the main magnetic field. Canine meniscal injury is a common sequela to cruciate tear, and detecting meniscal damage is important for directing patient care. The non-invasive quantitative MRI technique of UTE imaging can be used for the evaluation of collagen orientation, while acknowledging inherent regions of prolongation.

Evaluation of two collagen conduits and autograft in rabbit sciatic nerve regeneration with quantitative magnetic resonance DTI, electrophysiology, and histology.

BACKGROUND: We compared different surgical techniques for nerve regeneration in a rabbit sciatic nerve gap model using magnetic resonance diffusion tensor imaging (DTI), electrophysiology, limb function, and histology. METHODS: A total of 24 male New Zealand white rabbits were randomized into three groups: autograft (n = 8), hollow conduit (n = 8), and collagen-filled conduit (n = 8). A 10-mm segment of the rabbit proximal sciatic nerve was cut, and autograft or collagen conduit was used to bridge the gap. DTI on a 3-T system was performed preoperatively and 13 weeks after surgery using the contralateral, nonoperated nerve as a control. RESULTS: Overall, autograft performed better compared with both conduit groups. Differences in axonal diameter were significant (autograft > hollow conduit > collagen-filled conduit) at 13 weeks (autograft vs. hollow conduit, p = 0.001, and hollow conduit vs. collagen-filled conduit, p < 0.001). Significant group differences were found for axial diffusivity but not for any of the other DTI metrics (autograft > hollow conduit > collagen-filled conduit) (autograft vs. hollow conduit, p = 0.001 and hollow conduit vs. collagen-filled conduit, p = 0.021). As compared with hollow conduit (autograft > collagen-filled conduit > hollow conduit), collagen-filled conduit animals demonstrated a nonsignificant increased maximum tetanic force. CONCLUSIONS: Autograft-treated rabbits demonstrated improved sciatic nerve regeneration compared with collagen-filled and hollow conduits as assessed by histologic, functional, and DTI parameters at 13 weeks.

Magnetic resonance imaging and histologic features of the supraspinatus tendon in nonlame dogs.

OBJECTIVE To characterize the MRI and histologic features of the supraspinatus tendon in nonlame dogs. ANIMALS 7 cadavers (14 shoulder joints) of nonlame 2-year-old sexually intact male Beagles. PROCEDURES Multiple MRI fluid-sensitive pulse sequences were obtained for both shoulder joints of each cadaver, and the thickness, volume, and signal intensity of each supraspinatus tendon were assessed. After MRI scanning was complete, the shoulder joints were processed for histologic examination. Tissue specimens were stained with various stains to determine tendon morphology and composition. Histologic and MRI findings were correlated and described. RESULTS All supraspinatus tendons had a trilaminar appearance on sagittal and transverse MRI images, which was characterized by a thick, hyperintense center layer (central substance) sandwiched between thin hypointense superficial and deep margins. The mean ± SD central substance-to-superficial margin and central substance-to-deep margin thickness ratios were 8.4 ± 1.2 and 9.0 ± 0.9, respectively; supraspinatus tendon-to-triceps brachii muscle signal intensity ratio was 1.3 ± 0.2; and tendon volume was 445 ± 20 mm3. The superficial and deep margins histologically resembled other tendons with highly ordered collagen fibers. The central substance was comprised of water-rich glycosaminoglycans interspersed among haphazardly arranged collagen bundles. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated histologically normal canine supraspinatus tendons have a trilaminar appearance on MRI images. In dogs, a diagnosis of supraspinatus tendinosis should not be based solely on the tendon having a hyperintense signal on MRI images; other MRI evidence of shoulder joint disease and diagnostic findings are necessary to support such a diagnosis.

Magnetic Resonance Imaging T2 Values of Stifle Articular Cartilage in Normal Beagles.

OBJECTIVES: The purpose of this study was to evaluate regional differences of canine stifle articular cartilage using the quantitative magnetic resonance imaging (MRI) technique of T2 mapping. METHODS: Fourteen stifle joints from seven juvenile male Beagle dogs with no evidence or prior history of pelvic limb lameness were imaged ex vivo using standard of care fast spin echo MRI and quantitative T2 mapping protocols. Regions of interest were compared between the femoral, patellar and tibial cartilages, as well as between the lateral and medial femorotibial compartments. Limbs were processed for histology with standard stains to confirm normal cartilage. RESULTS: The average T2 value of femoral trochlear cartilage (37.5 ± 2.3 ms) was significantly prolonged (p < 0.0001) as compared with the femoral condylar, patellar and tibial condylar cartilages (33.1 ± 1.5 ms, 32.8 ± 2.3 ms, and 28.0 ± 1.7 ms, respectively). When comparing medial and lateral condylar compartments, the lateral femoral condylar cartilage had the longest T2 values (34.8 ± 2.8 ms), as compared with the medial femoral condylar cartilage (30.9 ± 1.9 ms) and lateral tibial cartilage (29.1 ± 2.3 ms), while the medial tibial cartilage had the shortest T2 values (26.7 ± 2.4 ms). CLINICAL SIGNIFICANCE: As seen in other species, regional differences in T2 values of the canine stifle joint are identified. Understanding normal regions of anticipated prolongation in different joint compartments is needed when using quantitative imaging in models of canine osteoarthritis.

An in vivo model of a mechanically-induced bone marrow lesion.

Bone marrow lesions (BMLs) are radiologic abnormalities in magnetic resonance images of subchondral bone that are correlated with osteoarthritis. Little is known about the physiologic processes within a BML, although BMLs are associated with mechanical stress, bone tissue microdamage and increased bone remodeling. Here we establish a rabbit model to study the pathophysiology of BMLs. We hypothesized that in vivo loads that generate microdamage in cancellous bone would also create BMLs and increase bone remodeling. In vivo cyclic loading (0.2-2.0 MPa in compression for 10,000 cycles at 2 Hz) was applied to epiphyseal cancellous bone in the distal femurs of New Zealand white rabbits (n=3, right limb loaded, left limb controls experienced surgery but no loading). Magnetic resonance images were collected using short tau inversion recovery (STIR) and T1 weighted sequences at 1 and 2 weeks after surgery/loading and histological analysis of the BML was performed after euthanasia to examine tissue microdamage and remodeling. Loaded limbs displayed BMLs while control limbs showed only a small BML-like signal caused by surgery. Histological analysis of the BML at 2 weeks after loading showed increased tissue microdamage (p=0.03) and bone resorption (p=0.01) as compared to controls. The model described here displays the hallmarks of load-induced BMLs, supporting the use of the model to examine changes in bone during the development, progression and treatment of BMLs.

Two-Year Evaluation of Osteochondral Repair with a Novel Biphasic Graft Saturated in Bone Marrow in an Equine Model.

Objective To evaluate a biphasic cartilage repair device (CRD) for feasibility of arthroscopic implantation, safety, biocompatibility, and efficacy for long-term repair of large osteochondral defects. Methods The CRD was press-fit into defects (10 mm diameter, 10 mm deep) created in the femoral trochlea of 12 horses. In the contralateral limb, 10 mm diameter full-thickness chondral defects were treated with microfracture (MFX). Radiographs were obtained pre- and postoperatively, and at 4, 12, and 24 months. Repeat arthroscopy was performed at 4 and 12 months. Gross assessment, histology, mechanical testing, and magnetic resonance imaging (MRI) were performed at 24 months. Results The CRD was easily placed arthroscopically. There was no evidence of joint infection, inflammation, or degeneration. CRD-treated defects had significantly more sclerosis compared to MFX early ( P = 0.0006), but was not different at 24 months. CRD had better arthroscopic scores at 4 months compared to MFX ( P = 0.0069). At 24 months, there was no difference in repair tissue on histology or mechanical testing. Based on MRI, CRD repair tissue had less proteoglycan (deep P = 0.027, superficial P = 0.015) and less organized collagen (deep P = 0.028) compared to MFX. Cartilage surrounding MFX defects had more fissures compared to CRD. Conclusion The repair tissue formed after CRD treatment of a large osteochondral lesion is fibrocartilage similar to that formed in simple chondral defects treated with MFX. The CRD can be easily placed arthroscopically, is safe, and biocompatible for 24 months. The CRD results in improved early arthroscopic repair scores and may limit fissure formation in adjacent cartilage.

Non-invasive magnetic resonance imaging diagnosis of presumed intermedioradial carpal bone avascular necrosis in the dog.

A 5-year-old, spayed female Weimaraner dog was evaluated for progressive left forelimb lameness localized to the carpus. Magnetic resonance imaging (MRI) was used to arrive at a presumptive diagnosis of intermedioradial carpal (IRC) bone fracture with avascular necrosis (AVN). To the authors' knowledge, this is the first report of naturally occurring AVN of the canine IRC diagnosed using MRI.

Diagnostic non invasif, à l'aide d'imagerie par résonnance magnétique, d'une nécrose avasculaire présumée de l'os intermédioradial du carpe chez le chien. Une chienne Weimaraner stérilisée âgée de 5 ans a été évaluée pour une boiterie progressive de la patte avant gauche située au carpe. L'imagerie par résonance magnétique (IRM) a été utilisée pour parvenir à un diagnostic présomptif d'une fracture de l'os intermédioradial du carpe (IRC) avec nécrose avasculaire. À la connaissance des auteurs, il s'agit du premier rapport d'une nécrose avasculaire naturelle l'IRC canin diagnostiquée à l'aide de l'IRM.(Traduit par Isabelle Vallières).

BioCartilage Improves Cartilage Repair Compared With Microfracture Alone in an Equine Model of Full-Thickness Cartilage Loss.

BACKGROUND: Microfracture (MFx) remains a dominant treatment strategy for symptomatic articular cartilage defects. Biologic scaffold adjuncts, such as particulated allograft articular cartilage (BioCartilage) combined with platelet-rich plasma (PRP), offer promise in improving clinical outcomes as an adjunct to MFx. PURPOSE: To evaluate the safety, biocompatibility, and efficacy of BioCartilage and PRP for cartilage repair in a preclinical equine model of full-thickness articular cartilage loss. STUDY DESIGN: Controlled laboratory study. METHODS: Two 10-mm-diameter full-thickness cartilage defects were created in 5 horses in the trochlear ridge of both knees: one proximal (high load) and another distal (low load). Complete blood counts were performed on each peripheral blood and resultant PRP sample. In each horse, one knee received MFx with BioCartilage + PRP, and the other knee received MFx alone. Horses were euthanized at 13 months. Outcomes were assessed with serial arthroscopy, magnetic resonance imaging (MRI), micro-computed tomography (micro-CT), and histology. Statistics were performed using a mixed-effects model with response variable contrasts. RESULTS: No complications occurred. PRP generated in all subjects yielded an increase in platelet fold of 3.8 ± 4.7. Leukocyte concentration decreased in PRP samples by an average fold change of 5 ± 0.1. The overall International Cartilage Repair Society repair score in both the proximal and distal defects was significantly higher (better) in the BioCartilage group compared with MFx (proximal BioCartilage: 7.4 ± 0.51, MFx 4.8 ± 0.1, P = .041; distal BioCartilage: 5.6 ± 0.98, MFx 2.6 ± 1.5, P = .022). BioCartilage-treated proximal defects demonstrated improved histologic scores for repair-host integration (BioCartilage, 96 ± 9; MFx, 68 ± 18; P = .02), base integration (BioCartilage, 100 ± 0; MFx, 70 ± 37; P = .04), and formation of collagen type II (BioCartilage, 82 ± 8; MFx, 58 ± 11; P = .05) compared with the positive control. On MRI, T2 relaxation time was significantly shorter (better) in the superficial region of BioCartilage-treated distal defects compared with MFx (P = .05). There were no significant differences between BioCartilage and MFx on micro-CT analysis. CONCLUSION: BioCartilage with PRP safely improved cartilage repair compared with MFx alone in an equine model of articular cartilage defects up to 13 months after implantation. CLINICAL RELEVANCE: The 1-year results of BioCartilage + PRP suggest that homologous allograft tissue provides a safe and effective augmentation of traditional MFx.

High-Resolution Methods for Diagnosing Cartilage Damage In Vivo.

Advances in current clinical modalities, including magnetic resonance imaging and computed tomography, allow for earlier diagnoses of cartilage damage that could mitigate progression to osteoarthritis. However, current imaging modalities do not detect submicrometer damage. Developments in in vivo or arthroscopic techniques, including optical coherence tomography, ultrasonography, bioelectricity including streaming potential measurement, noninvasive electroarthrography, and multiphoton microscopy can detect damage at an earlier time point, but they are limited by a lack of penetration and the ability to assess an entire joint. This article reviews current advancements in clinical and developing modalities that can aid in the early diagnosis of cartilage injury and facilitate studies of interventional therapeutics.

The effect of freeze-thawing on magnetic resonance imaging T2* of freshly harvested bovine patellar tendon.

BACKGROUND: Analysis of fresh specimens in research studies is ideal; however, it is often necessary to freeze samples for evaluation at a later time. Limited evaluation of the effect of freeze-thawing of tendon tissue samples on inherent magnetic resonance imaging (MRI) parameters, such as ultrashort echo time (UTE) T2* values, have been performed to date. METHODS: This study performed UTE MRI on 14 bovine patellar tendons at harvest and after four consecutive freeze-thaw cycles. RESULTS: Results demonstrated a small but significant reduction (12%) in tendon T2* values after the first freeze thaw cycle, but not after successive cycles. Tendons from juvenile animals with open physis had a significant reduction of T2* following a single freeze thaw cycle, P<0.0001. CONCLUSIONS: The results of this study emphasize the importance of using uniform tendon storage protocols when using UTE MRI in preclinical models.

Ultrashort echo imaging of cyclically loaded rabbit patellar tendon.

Tendinopathy affects individuals who perform repetitive joint motion. Magnetic resonance imaging (MRI) is frequently used to qualitatively assess tendon health, but quantitative evaluation of inherent MRI properties of loaded tendon has been limited. This study evaluated the effect of cyclic loading on T2* values of fresh and frozen rabbit patellar tendons using ultra short echo (UTE) MRI. Eight fresh and 8 frozen rabbit lower extremities had MR scans acquired for tendon T2* evaluation. The tendons were then manually cyclically loaded for 100 cycles to 45 N at approximately 1 Hz. The MR scanning was repeated to reassess the T2* values. Analyses were performed to detect differences of tendon [Formula: see text] values between fresh and frozen samples prior to and after loading, and to detect changes of tendon T2* values between the unloaded and loaded configurations. No difference of T2* was found between the fresh and frozen samples prior to or after loading, p=0.8 and p=0.1, respectively. The tendons had significantly shorter T2* values, p=0.023, and reduced T2* variability, p=0.04, after cyclic loading. Histologic evaluation confirmed no induced tendon damage from loading. Shorter T2* , from stronger spin-spin interactions, may be attributed to greater tissue organization from uncrimping of collagen fibrils and lateral contraction of the tendon during loading. Cyclic tensile loading of tissue reduces patellar tendon T2* values and may provide a quantitative metric to assess tissue organization.