IL-1ra gene therapy in equine osteoarthritis improves physiological, anatomical, and biological outcomes of joint degeneration.

OBJECTIVE: To evaluate the effects of a gene transfer approach to IL-1ß inhibition in an equine osteochondral chip fragment model of joint injury using a self-complementary adeno-associated virus with interleukin receptor antagonist transgene cassette (scAAVIL-1ra), as posttraumatic osteoarthritis in horses, similar to people, is a significant clinical problem. ANIMALS: 16 horses were utilized for the study. METHODS: All horses had an osteochondral chip fragment induced arthroscopically in one middle carpal joint while the contralateral joint was sham operated. Eight horses received either scAAVIL-1ra or saline in the osteoarthritis joint. Horses were evaluated over 70 days clinically (lameness, imaging, and biomarker analysis) and euthanized at 70 days and evaluated grossly, with imaging and histopathology. RESULTS: The following findings were statistically significant. Injection of scAAVIL-1ra resulted in high synovial fluid levels of IL-1ra (0.5 to 9 µg/mL) throughout the duration of the experiment (70 days). Over the duration, we observed scAAVIL-1ra to improve lameness (lameness score relative improvement of 1.2 on a scale of 0 to 5), cause suppression of prostaglandin E2 (a relative decline of 30 pg/mL), and result in histological improvement in articular cartilage (decreased chondrocyte loss and chondrone formation) and subchondral bone (less osteochondral splitting and osteochondral lesions). Within the synovial membrane of scAAVIL-1ra-treated joints, we also observed perivascular infiltration with CD3-positive WBCs, suggesting lymphocytic T-cell perivascular infiltration commonly observed with viral transduction. CLINICAL RELEVANCE: These data provide support for further evaluation and optimization of scAAVIL-1ra gene therapy to treat equine osteoarthritis.

Dynamic three-dimensional computed tomographic imaging facilitates evaluation of the equine cervical articular process joint in motion.

BACKGROUND: Dynamic computed tomography (CT) imaging has been introduced in human orthopaedics and is continuing to gain popularity. With dynamic CT, video sequences of anatomical structures can be evaluated in motion. OBJECTIVES: To investigate the feasibility of dynamic CT for diagnostic imaging of the equine cervical articular process joints (APJs) and to give a detailed description of the APJ movement pattern. STUDY DESIGN: Descriptive cadaver imaging. METHODS: Cervical specimens of twelve Warmblood horses were included. A custom-made motorised testing device was used to position and manipulate the neck specimens and perform dynamic 2D and 3D CT imaging. Images were obtained with a 320-detector-row CT scanner with a 160 mm wide-area (2D) solid-state detector design that allows image acquisition of a volumetric axial length of 160 mm without moving the CT couch. Dynamic videos were acquired and divided into four phases of movement. Three blinded observers used a subjective scale of 1 (excellent) to 4 (poor) to grade the overall image quality in each phases of motion cycle. RESULTS: With an overall median score of 1 the image quality, a significantly lower score was observed in the dynamic 3D videos over the four phases by the three observers compared with the 2D videos for both flexion (3D 95% CI: 1-2 and 2D 95% CI: 1-3; P = .007) and extension movement (3D 95% CI: 1-2 and 2D 95% CI: 1-3; P = .008). Median Translational displacement of the APJ surface was significantly greater in flexion than in extension movement (P = .002). MAIN LIMITATIONS: The small number of specimens included. Excision of spines and removal of musculature. CONCLUSIONS: The study is a first step in the investigation of the potential of dynamic 3D CT in veterinary medicine, a technique that has only begun to be explored and leaves much room for refinement prior to its introduction in routine practice. CT with a detector coverage of 16 cm and a rotation speed of 0.32 seconds provides high-quality images of moving objects and gives new insight into the movement pattern of equine cervical APJs.

TLR-activated mesenchymal stromal cell therapy and antibiotics to treat multi-drug resistant Staphylococcal septic arthritis in an equine model.

Background: Rapid development of antibiotic resistance necessitates advancement of novel therapeutic strategies to treat infection. Mesenchymal stromal cells (MSC) possess antimicrobial and immunomodulatory properties, mediated through antimicrobial peptide secretion and recruitment of innate immune cells including neutrophils and monocytes. TLR-3 activation of human, canine and equine MSC has been shown to enhance bacterial killing and clearance in vitro, in rodent Staphylococcal biofilm infection models and dogs with spontaneous multi-drug-resistant infections. The objective of this study was to determine if intra-articular (IA) TLR-3-activated MSC with antibiotics improved clinical parameters and reduced bacterial counts and inflammatory cytokine concentrations in synovial fluid (SF) of horses with induced septic arthritis. Methods: Eight horses were inoculated in one tarsocrural joint with multidrug-resistant Staphylococcus aureus (S. aureus). Bone marrow-derived MSC from three unrelated donors were activated with TLR-3 agonist polyinosinic, polycytidylic acid (pIC). Recipient horses received MSC plus vancomycin (TLR-MSC-VAN), or vancomycin (VAN) alone, on days 1, 4, 7 post-inoculation and systemic gentamicin. Pain scores, quantitative bacterial counts (SF, synovium), SF analyses, complete blood counts, cytokine concentrations (SF, plasma), imaging changes (MRI, ultrasound, radiographs), macroscopic joint scores and histologic changes were assessed. Results were reported as mean ± SEM. Results: Pain scores (d7, P=0.01, 15.2±0.2 vs. 17.9±0.5), ultrasound (d7, P=0.03, 9.0±0.6 vs. 11.8±0.5), quantitative bacterial counts (SF d7, P=0.02, 0±0 vs. 3.4±0.4; synovium P=0.003, 0.4±0.4 vs. 162.7±18.4), systemic neutrophil (d4, P=0.03, 4.6±0.6 vs. 7.8±0.6) and serum amyloid A (SAA) (d4, P=0.01, 1,106.0±659.0 vs. 2,858.8±141.3; d7, P=0.02, 761.8±746.2 vs. 2,357.3±304.3), and SF lactate (d7, P<0.0001, 5.4±0.2 vs. 15.0±0.3), SAA (endterm, P=0.01, 0.0 vs. 2,094.0±601.6), IL-6 (P=0.03, 313.0±119.2 vs. 1,328.2±208.9), and IL-18 (P=0.02, 11.1±0.5 vs. 13.3±3.8) were improved in TLR-MSC-VAN vs. VAN horses. Study limitations include the small horse sample size, short study duration, and lack of additional control groups. Conclusions: Combined TLR-activated MSC with antibiotic therapy may be a promising approach to manage joint infections with drug resistant bacteria.

Three-Dimensional Segmentation and in silico Comparison of Equine Deep Digital Flexor Tendon Pathology in Horses Undergoing Repeated MRI Examination.

The use of magnetic resonance imaging (MRI) has led to increased clinical and research applications using 3D segmentation and reconstructed volumetric data in musculoskeletal imaging. Lesions of the deep digital flexor tendon (DDFT) are a common pathology in horses undergoing MRI. Three-dimensional MRI reconstruction performed for volumetric tendon analysis in horses has not previously been documented. The aim of this proof-of-concept study was to evaluate the 3D segmentation of horses undergoing repeated MRI at several time points and to perform an analysis of the segmented DDFTs across time. MRI DICOM files were acquired from six horses undergoing repeated MRI examination of the foot for DDFT injury. Once segmented, volumetric tendon surface tessellation language (STL) files were created. Thickness and volumetric data were acquired for each tendon in addition to a tendon comparison across timepoints within each horse. Pearson correlation coefficients were calculated for comparison of MRI reports to computer analysis. There was a significant and positive correlation between MRI and medial record reports of clinical improvement or deterioration and computer analysis (r = 0.56, p = 0.01). The lower end range limit for tendon thickness varied between 0.16 and 1.74 mm. The upper end range limit for DDFT thickness varied between 4.6 and 23.6 mm. During tendon part comparison, changes in DDFT were reported between -3.0 and + 14.3 mm. Changes in DDFT size were non-uniform and demonstrated fluctuations throughout the tendon. The study was successful in establishing the volumetric appearance and thickness of the DDFT as it courses in the foot and tracking this over time. We encountered difficulties in accurate segmentation of the distal insertion of the DDFT as it blends with the distal phalanx. The data demonstrated that the DDFT can be segmented and volumetric studies based on size and shape can be performed using an in silico approach.

Non-weight bearing ultrasonographic examination allows the diagnosis of longitudinal fiber disruption (split) in equine suspensory ligament branches not visible on weight bearing examination.

When evaluating suspensory ligament branch splits, there is a discrepancy between high field MRI findings and weight bearing ultrasonographic imaging characteristics. In this descriptive and retrospective case series, ultrasonographic examination was performed on suspensory ligament branches with the limbs in weight bearing and non-weight bearing positions. Suspensory ligament branch splits were defined as linear regions of decreased echogenicity when imaged with the limb in a weight bearing position that increased in size and became anechoic with the limb in a non-weight bearing position. This appearance was considered an indication of pathologic change in the branch. A total of 62 suspensory ligament branches were included in the study from 37 horses, with 14 partial splits, 11 intrasubstance splits, and 14 complete splits of which two had extension of fetlock synovial fluid and synovial membrane through the split. Recheck ultrasonographic examinations performed in eight horses up to 14 months following the initial examination demonstrated persistence of the split in two horses, partial resolution in five horses, and complete resolution in one horse. Ultrasonographic examination using the non-weight bearing approach proved valuable for increasing the lesion conspicuity as compared to the weight bearing images. Certain abnormalities, such as longitudinal fiber disruption (split) in suspensory ligament branches may only be evident when imaged non-weight bearing. The use of this technique provides a more accurate representation of lesion severity and allows for monitoring over time. A longitudinal study is necessary to determine the clinical relevance of suspensory ligament branch splits.

Physiologic effects of long-term immobilization of the equine distal limb.

OBJECTIVE: To describe the effects of distal limb immobilization and remobilization in the equine metacarpophalangeal joint. STUDY DESIGN: Randomized, prospective experimental study. ANIMALS: Eight healthy, skeletally mature horses. METHODS: One forelimb of each horse was immobilized in a fiberglass cast for 8 weeks; this was followed by 12 weeks of a treadmill-based training program after the cast had been removed. Clinical examinations, radiography, computed tomography (CT), nuclear scintigraphy, MRI, and histomorphometry were used to examine the third metacarpal (MC3), proximal phalanx, proximal sesamoid bones, and associated soft tissues in each horse. Serum and synovial fluid were collected for biomarker analyses. RESULTS: Distal limb immobilization resulted in persistent lameness (P < .001), effusion (P = .002), and a decreased range of motion (P = .012) as well as radiographically visible fragments (P = .036) in the cast forelimb. Bone density was decreased (P < .001) in MC3 according to CT, and trabecular bone fluid was increased (P < .001) according to MRI in the cast forelimb. The cast forelimbs had a change (P = .009) in the appearance of the deep digital flexor tendon according to MRI immediately after removal of the cast. Numerous clinical, radiographic, CT, and MR abnormalities were visible at the end of the study period. CONCLUSION: Eights weeks of cast immobilization induced changes in bone, cartilage, and periarticular soft tissues that were not reversed after 12 weeks of remobilization. CLINICAL SIGNIFICANCE: Cast application should be used judiciously in horses with musculoskeletal injuries, balancing appropriate stabilization with potential morbidity secondary to cast placement.

Standing MRI lesions of the distal interphalangeal joint and podotrochlear apparatus occur with a high frequency in warmblood horses.

Foot pain is a common presenting complaint in Warmblood horses. The aim of this retrospective, cross-sectional study was to determine the spectrum of foot lesions detected by magnetic resonance imaging (MRI) in Warmblood horses used for dressage, jumping, and eventing. The medical records of 550 Warmblood horses with foot pain that were scanned using standing MRI were reviewed and the following data were recorded: signalment, occupation, lameness, diagnostic analgesia, imaging results, treatments, and follow-up assessments. Associations between standing MRI lesions and chronic lameness following treatment were tested. Abnormalities of the navicular bone (409 horses, 74%), distal interphalangeal joint (362 horses, 65%), and deep digital flexor (DDF) tendon (260 horses, 47%) occurred with the highest frequency. The following abnormalities were significantly associated (P < .05) with chronic lameness following conservative therapy: moderate to severe MRI lesions in the trabecular bone of the navicular bone, mild or severe erosions of the flexor surface of the navicular bone, moderate sagittal/parasagittal DDF tendinopathies, and moderate collateral sesamoidean desmopathies. Also, identification of concurrent lesions of the DDF tendon, navicular bone, navicular bursa, and distal sesamoidean impar ligament was associated with chronic lameness after conservative therapy. Development of effective treatment options for foot lesions that respond poorly to conservative therapy is necessary.

Biomechanical and histologic evaluation of the effects of underwater treadmill exercise on horses with experimentally induced osteoarthritis of the middle carpal joint.

OBJECTIVE To evaluate the effects of exercise in an underwater treadmill (UWT) on forelimb biomechanics and articular histologic outcomes in horses with experimentally induced osteoarthritis of the middle carpal joint. ANIMALS 16 horses. PROCEDURES An osteochondral fragment was induced arthroscopically (day 0) in 1 middle carpal joint of each horse. Beginning on day 15, horses were assigned to exercise in a UWT or in the UWT without water (simulating controlled hand walking) at the same speed, frequency, and duration. Thoracic and pelvic limb ground reaction forces, thoracic limb kinematics, and electromyographic results for select thoracic limb muscles acting on the carpi were collected on days -7 (baseline), 14, 42, and 70. Weekly evaluations included clinical assessments of lameness, response to carpal joint flexion, and goniometric measurements of thoracic limb articulations. At study conclusion, articular cartilage and synovial membrane from the middle carpal joints was histologically examined. RESULTS Exercise in a UWT significantly reduced synovial membrane inflammation and resulted in significant clinical improvements with regard to symmetric thoracic limb loading, uniform activation patterns of select thoracic limb muscles, and return to baseline values for carpal joint flexion, compared with results for horses with simulated hand walking. CONCLUSIONS AND CLINICAL RELEVANCE Overall improvements in thoracic limb function, joint range of motion, and synovial membrane integrity indicated that exercise in a UWT was a potentially viable therapeutic option for the management of carpal joint osteoarthritis in horses.

INJURIES OF THE SAGITTAL GROOVE OF THE PROXIMAL PHALANX IN WARMBLOOD HORSES DETECTED WITH LOW-FIELD MAGNETIC RESONANCE IMAGING: 19 CASES (2007-2016).

Sagittal groove injuries of the proximal phalanx are an important cause of lameness in performance horses. The purpose of this retrospective case series study was to describe standing low-field magnetic resonance imaging (MRI) characteristics of these injuries in a group of Warmblood horses. Horses with an MRI diagnosis of sagittal groove injuries involving the proximal phalanx and that had follow-up MRI and clinical outcome information were included. Findings from clinical examinations, diagnostic tests, and other imaging modalities were recorded. All MRI studies were retrieved for re-evaluation by an experienced, board-certified veterinary radiologist. A total of 19 horses met inclusion criteria. All horses had MRI lesions consistent with unilateral or bilateral sagittal groove injuries of the proximal phalanx and abnormal mineralization of the sagittal ridge of the third metacarpal/metatarsal bone. Fifteen horses (79%) had concurrent osteoarthritis of the affected metacarpophalangeal/metatarsophalangeal joint. Eighteen horses received conservative therapy and all horses still had osseous abnormalities detected at the time of follow-up MRI. Thirteen horses (68.5%) were still lame at the time of follow-up, whereas the other six horses (31.5%) had become sound and returned to the previous level of exercise. Findings indicated that, for mature Warmblood horses, acute or chronic injuries of the sagittal groove of the proximal phalanx may have variable standing low-field MRI characteristics. Based on this sample of 19 horses, findings also indicated that the prognosis for performance soundness in horses diagnosed with sagittal groove injury of the proximal phalanx and concurrent osteoarthritis is poor.

Efficacy of intravenous administration of hyaluronan, sodium chondroitin sulfate, and N-acetyl-d-glucosamine for prevention or treatment of osteoarthritis in horses.

OBJECTIVE To evaluate the efficacy of IV administration of a product containing hyaluronan, sodium chondroitin sulfate, and N-acetyl-d-glucosamine for prevention or treatment of osteoarthritis in horses. ANIMALS 32 healthy 2- to 5-year-old horses. PROCEDURES The study involved 2 portions. To evaluate prophylactic efficacy of the test product, horses received 5 mL of the product (n = 8) or saline (0.9% NaCl) solution (8; placebo) IV every fifth day, starting on day 0 (when osteoarthritis was induced in the middle carpal joint of 1 forelimb) and ending on day 70. To evaluate treatment efficacy, horses received either the product or placebo (n = 8/treatment) on days 16, 23, 30, 37, and 44 after osteoarthritis induction. Clinical, diagnostic imaging, synovial fluid, gross anatomic, and histologic evaluations and other tests were performed. Results of each study portion were compared between treatment groups. RESULTS Limb flexion and radiographic findings were significantly worse for horses that received the test product in the prophylactic efficacy portion than for placebo-treated horses or product-treated horses in the treatment efficacy portion. In the prophylactic efficacy portion, significantly less articular cartilage erosion was identified in product-treated versus placebo-treated horses. In the treatment efficacy portion, joints of product-treated horses had a greater degree of bone edema identified via MRI than did joints of placebo-treated horses but fewer microscopic articular cartilage abnormalities. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that caution should be used when administering the evaluated product IV to horses, particularly when administering it prophylactically, as it may have no benefit or may even cause harm.

COMPARISON BETWEEN COMPUTED TOMOGRAPHIC ARTHROGRAPHY, RADIOGRAPHY, ULTRASONOGRAPHY, AND ARTHROSCOPY FOR THE DIAGNOSIS OF FEMOROTIBIAL JOINT DISEASE IN WESTERN PERFORMANCE HORSES.

The femorotibial joints are a common source of lameness in Western performance horses. The objective of this prospective study was to compare the radiography, ultrasonography, computed tomographic arthrography (CTA), and arthroscopy findings in horses with lameness localized to the femorotibial joints. Twenty-five stifles in 24 horses were included and were evaluated with all four of these diagnostic methods. Defects detected in femorotibial joint structures were compared between diagnostic methods using a McNemar's test to evaluate for disagreement. Cranial medial meniscotibial desmopathy was most detected on arthroscopy (in 14/25 cases) and was only detected on ultrasonography in three out of 11 (27.3%) arthroscopically observed cases, but was detected on CTA in nine out of 12 (75%) arthroscopically observed cases. Medial meniscal injury located on the craniolateral border was most detected on arthroscopy (n = 9) and was detected on CTA in five cases, but on ultrasonography in 0 cases. Detection of articular cartilage defects on the medial femoral condyle was most detected with arthroscopy (24/25, 96% cases) and was also detected on CTA in 12/20 (60%) cases with a significant disagreement identified between modalities (P = 0.02). Cranial and caudal cruciate ligament defects were detected on CTA in 6/22 (27.3%) and 7/19 (36.8%) cases, respectively, and with arthroscopy in 3/25 (12%) and 2/25 (8%) cases, respectively. The use of CTA detected more defects in the cruciate ligaments, proximal tibia, and ligament entheses than the other diagnostic methods, but was not reliable for detection of articular cartilage damage on the medial femoral condyle.

Addition of Mesenchymal Stem Cells to Autologous Platelet-Enhanced Fibrin Scaffolds in Chondral Defects: Does It Enhance Repair?

BACKGROUND: The chondrogenic potential of culture-expanded bone-marrow-derived mesenchymal stem cells (BMDMSCs) is well described. Numerous studies have also shown enhanced repair when BMDMSCs, scaffolds, and growth factors are placed into chondral defects. Platelets provide a rich milieu of growth factors and, along with fibrin, are readily available for clinical use. The objective of this study was to determine if the addition of BMDMSCs to an autologous platelet-enriched fibrin (APEF) scaffold enhances chondral repair compared with APEF alone. METHODS: A 15-mm-diameter full-thickness chondral defect was created on the lateral trochlear ridge of both stifle joints of twelve adult horses. In each animal, one defect was randomly assigned to receive APEF+BMDMSCs and the contralateral defect received APEF alone. Repair tissues were evaluated one year later with arthroscopy, histological examination, magnetic resonance imaging (MRI), micro-computed tomography (micro-CT), and biomechanical testing. RESULTS: The arthroscopic findings, MRI T2 map, histological scores, structural stiffness, and material stiffness were similar (p > 0.05) between the APEF and APEF+BMDMSC-treated repairs at one year. Ectopic bone was observed within the repair tissue in four of twelve APEF+BMDMSC-treated defects. Defects repaired with APEF alone had less trabecular bone edema (as seen on MRI) compared with defects repaired with APEF+BMDMSCs. Micro-CT analysis showed thinner repair tissue in defects repaired with APEF+BMDMSCs than in those treated with APEF alone (p < 0.05). CONCLUSIONS: APEF alone resulted in thicker repair tissue than was seen with APEF+BMDMSCs. The addition of BMDMSCs to APEF did not enhance cartilage repair and stimulated bone formation in some cartilage defects. CLINICAL RELEVANCE: APEF supported repair of critical-size full-thickness chondral defects in horses, which was not improved by the addition of BMDMSCs. This work supports further investigation to determine whether APEF enhances cartilage repair in humans.

Effects of the combination of microfracture and self-assembling Peptide filling on the repair of a clinically relevant trochlear defect in an equine model.

BACKGROUND: The goal of this study was to test the ability of an injectable self-assembling peptide (KLD) hydrogel, with or without microfracture, to augment articular cartilage defect repair in an equine cartilage defect model involving strenuous exercise. METHODS: Defects 15 mm in diameter were created on the medial trochlear ridge and debrided down to the subchondral bone. Four treatment groups (n = 8 each) were tested: no treatment (empty defect), only defect filling with KLD, only microfracture, and microfracture followed by filling with KLD. Horses were given strenuous exercise throughout the one-year study. Evaluations included lameness, arthroscopy, radiography, and gross, histologic, immunohistochemical, biochemical, and biomechanical analyses. RESULTS: Overall, KLD-only treatment of defects provided improvement in clinical symptoms and improved filling compared with no treatment, and KLD-only treatment protected against radiographic changes compared with microfracture treatment. Defect treatment with only microfracture also resulted in improved clinical symptoms compared with no treatment, and microfracture treatment resulted in repair tissue containing greater amounts of aggrecan and type-II collagen compared with KLD-only treatment. Microfracture treatment also protected against synovial fibrosis compared with no treatment and KLD-only treatment. Treatment with the self-assembling KLD peptide in combination with microfracture resulted in no additional improvements over microfracture-only treatment. In general, the nature of the predominant tissue in the defects was a mix of noncartilaginous and fibrocartilage tissue, with no significant differences among the treatments. CONCLUSIONS: Treatment of defects with only KLD or with only microfracture resulted in an improvement in clinical symptoms compared with no treatment; the improvement likely resulted from different causes depending on the treatment. Whereas microfracture improved the quality of repair tissue, KLD improved the amount of filling and protected against radiographic changes. CLINICAL RELEVANCE: Treatment of defects with only microfracture and with KLD only resulted in clinical improvements compared with untreated defects, despite differing with respect to the structural improvements that they induced.

Effect of limb positioning on the radiographic appearance of the distal and proximal interphalangeal joint spaces of the forelimbs of horses during evaluation of dorsopalmar radiographs.

OBJECTIVE: To determine the effect of limb positioning on the radiographic appearance of the distal and proximal interphalangeal joint spaces of the forelimbs of horses during evaluation of dorsopalmar radiographs. DESIGN: Evaluation study. ANIMALS: 14 forelimbs from 9 adult horses. PROCEDURES: Each horse was in standing position with its forelimbs positioned on blocks. Dorsopalmar radiographs of each foot were obtained with the forelimbs positioned squarely (the metacarpus of both forelimbs was perpendicular to the ground as determined by visual examination [abducted 0°]; baseline) and abducted 5° and 10°. The width of the space at the medial and lateral aspects of the distal and proximal interphalangeal joints (medial and lateral joint space width, respectively) was measured. Mediolateral joint balance was calculated as the difference between the widths of the lateral and medial joint spaces, and joint space width and mediolateral joint balance were compared among all 3 positions. RESULTS: As the extent of limb abduction increased, the medial aspect of the proximal and distal interphalangeal joints became narrower, compared with the corresponding lateral aspect of those joints. For both the distal and proximal interphalangeal joints, the mediolateral joint balance differed significantly among all limb positions. CONCLUSIONS AND CLINICAL RELEVANCE: Forelimb position significantly affected the mediolateral joint balance of the interphalangeal joints of horses. Thus, it is crucial that the forelimbs of horses be squarely positioned when dorsopalmar radiographs are obtained for accurate evaluation of interphalangeal joint space and balance.

New concepts in standing advanced diagnostic equine imaging.

This article addresses the clinical application of magnetic resonance imaging (MRI) and computed tomography (CT) as applied to the standing equine patient. This discussion includes the logistics, advantages, disadvantages, and limitations of imaging a standing horse. In addition, a brief review is given of the physics of these modalities as applied in clinical practice, and the currently available hardware and software required by these techniques for image acquisition and artifact reduction. The appropriate selection of clinical cases for standing MRI and CT is reviewed, focusing on cases that are capable of undergoing standing surgeries following lesion diagnosis.

The effect of varying echo time using T2-weighted FSE sequences on the magic angle effect in the collateral ligaments of the distal interphalangeal joint in horses.

Eight skeletally mature equine cadaver distal forelimbs were imaged using T2-weighted fast spin echo (FSE) sequences in a 1.0 T horizontal bore magnet. Each limb was parallel to the main magnetic field and with 16° angulation of the limb relative to the main magnetic field, which places one of the collateral ligaments of the distal interphalangeal joint at or near the magic angle. Each limb was imaged using an echo time (TE) of 80, 100, 120, and 140 ms. Reversal of the magic angle effect was achieved at echo time of 140 ms. However, given the alterations in tissue contrast and subjective decrease in the signal-to-noise ratio at this TE, it may be preferable to use a shorter TE for clinical imaging. A T2-weighted FSE sequence with an echo time of 120 ms maintained image quality while subjectively minimizing the magic angle effect. A sequence with long TE can be used to aid in the differentiation of pathologic change from artifactual increases in signal intensity in collateral ligaments of the equine distal interphalangeal joint, but could decrease the sensitivity for small or low contrast lesions. Multiple factors should be considered when selecting the TE for a T2-weighted FSE sequence that will be utilized in a musculoskeletal protocol including evaluation of equine feet.

Imaging of the equine proximal suspensory ligament.

Injury to the suspensory ligament can result in significant lameness. Multiple imaging modalities may be required to fully characterize injury to the suspensory ligament. Ultrasonography of the suspensory ligament is challenging, due to the normal anatomy. This article describes imaging of the proximal suspensory ligament in the front and hind limbs of the horse.

Recheck magnetic resonance imaging examinations for evaluation of musculoskeletal injury.

Recheck magnetic resonance imaging (MRI) studies are critical to assess response to treatment and correctly determine both a horse's ability to return to exercise and an appropriate exercise program. As with any other modality, many diagnoses require additional monitoring. This principle applies to MRI despite the more significant financial investment and potential requirement for general anesthesia. This article explores the use of recheck MRIs in case management and proposes time frames for these studies based on the initial diagnosis.