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Foot infections
Abstracts / Journal of Equine Veterinary Science 32 (2012) 667-673
(Figs. 9 and 10). These disparate cases suggest that high sensitivity in reported findings is lacking, both with lowand high-field examinations. The cartilage abnormalities seen with this imaging protocol appeared as focal, multifocal, or diffuse hypointense lesions on the 3D GE T1 sequence. Although we are unsure how many clinically significant articular cartilage lesions go undetected or are underestimated using this pulse sequence, our experience (including our post mortem findings) suggests that the visible lesions are authentic. The articular lesions identified are considered abnormal findings, but their clinical significance is dependent upon the severity of the abnormalities and on the other aspects of each clinical case. The vast majority of the horses studied had other soft tissue or bony abnormalities that were deemed to be of greater clinical significance than the cartilage lesions. Furthermore, when the opposite (sound) limb was scanned for comparison, the articular findings frequently were bilateral, and in numerous cases more pronounced in the sound limb. These patterns suggest that a lot of the cartilage lesions identified were subclinical. However, the horses with advanced articular changes and/ or significant subchondral bone lesions often had clinical presentations compatible with an arthropathy. The postmortem comparison shown in Figure 10 revealed marked cartilage degeneration in the coffin joint, but the radiographs were completely unremarkable. The patient’s radiographs were rarely submitted with routine clinical MRI studies, so a correlation of radiographic abnormalities with MRI findings cannot be made from this study. In summary, various articular cartilage abnormalities are commonly seen at 0.25T in the joints of equine athletes. In our experience, the isotropic 3D GE T1 sequence used at 0.25T appears to allow acceptable evaluation of articular cartilage in the distal limb, as well as the fibrocartilage layer on the flexor margin of the navicular bone. Although most of the articular cartilage and fibrocartilage lesions described were considered mild and subclinical, the identification of more advanced lesions was critical to the diagnosis and management of the case. Acknowledgments: The authors thank all of the institutions that provided clinical scans for this review, and particularly the staff at Equine Services, LTD in Wellington, FL for assisting with some postmortem work. Disclosure: No funding or support was received for any of this clinical work. The first author provides independent MRI consultation for equine practices and others (including Universal Medical Systems, a distributor for the Esaote Vet MR Grande). References [1] Gold GE, Chen CA, Koo S, et al. Recent advances in MRI of articular cartilage. AJR Am J Roentgenol 2009;193(3):628-38. [2] Potter HG, Black BR, Chong le R. New techniques in articular cartilage imaging. Clin Sports Med 2009;28(1):77-94. [3] Olive J, D’Anjou MA, Girard C, et al. Fat-suppressed spoiled gradientrecalled imaging of equine metacarpophalangeal articular cartilage. Vet Radiol Ultrasound 2010;51(2):107-15. [4] O’Brien T, Baker TA, Brounts SH, et al. Detection of articular pathology of the distal aspect of the third metacarpal bone in thoroughbred racehorses: comparison of radiography, computed tomography and magnetic resonance imaging. Vet Surg 2011;40(8):942-51. [5] Murray RC, Branch MV, Tranquille C, et al. Validation of magnetic resonance imaging for measurement of equine articular cartilage
[6]
[7]
[8]
[9]
[10]
[11]
671
and subchondral bone thickness. Am J Vet Res 2005;66(11):19992005. Olive J, D’Anjou MA, Girard C, et al. Imaging and histological features of central subchondral osteophytes in racehorses with metacarpophalangeal joint osteoarthritis. Equine Vet J 2009;41(9):859-64. Sherlock CE, Mair TS, Ter Braake F. Osseous lesions in the metacarpo(tarso)phalangeal joint diagnosed using low-field magnetic resonance imaging in standing horses. Vet Radiol Ultrasound 2009; 50(1):13-20. Murray RC, Mair TS, Sherlock CE, et al. Comparison of high-field and low-field magnetic resonance images of cadaver limbs of horses. Vet Rec 2009;165(10):281-8. Smith MA, Dyson SJ, Murray RC. Reliability of high- and low-field magnetic resonance imaging systems for detection of cartilage and bone lesions in the equine cadaver fetlock. Equine Vet J; 2012. Werpy NM, Ho CP, Pease AP, et al. The effect of sequence selection and field strength on detection of osteochondral defects in the metacarpophalangeal joint. Vet Radiol Ultrasound 2011;52(2):154-60. Olive J. Distal interphalangeal articular cartilage assessment using low-field magnetic resonance imaging. Vet Radiol Ultrasound 2010; 51(3):259-66.
Abstracts Foot infections Raul J. Bras DVM, CJF Podiatry Department, Rood and Riddle Equine Hospital, Lexington, KY Take-home message: Most superficial infections resolve with proper drainage. If there is no improvement after 48 hours or if there is continued drainage after several days, then infection of the deeper structures should be considered. Radiography and microbial culture and sensitivity are important components of diagnosis and treatment for deep infections of the foot. Introduction: Foot infections are a common source of lameness in horses. To be able to understand infections of the foot, it is important to have a complete understanding of the complex anatomy and all the structures that could be involved. The sensitive structures of the foot are protected by the hoof capsule, which consists of the hoof wall and sole. In order for an infection to occur, the microorganisms must gain entry through this protective hoof capsule. The horse’s foot is constantly in contact and interacting with its environment, so it is susceptible to various types of trauma and injuries. The causes of foot infection include hoof capsule defects (e.g. cracks, white line disease), chronic wounds (e.g. to the digital cushion), instability (e.g. laminitis), canker, quittor (i.e. infection of the collateral or ungual cartilage), keratoma, and systemic infection. Infections of the foot can be classified as superficial or deep. Superficial Infections: Superficial infections involve the tissue between the epidermis (hoof capsule) and the underlying dermis. The majority of superficial infections are easily located and opened to establish drainage. Most of these cases show continuous improvement once drainage is established. If there is no improvement in the 48 hours after drainage is established, or if there is continued drainage after several days, then we should be concerned that deeper structures may be involved. Deep Infections: Deep infections involve any of the structures deep to the dermis: the coffin bone, digital cushion, tendons, ligaments, and synovial structures. Samples obtained from the infection site are very useful for bacteria
672
Abstracts / Journal of Equine Veterinary Science 32 (2012) 667-673
identification and antimicrobial selection. Radiography should also be used to check for involvement of deeper structures. Puncture wounds to the central region of the foot, in particular, should be treated as an emergency and all necessary diagnostic procedures performed to determine which structures are involved. It must be noted that successful treatment of foot infections depends on a good veterinarian–farrier–owner relationship.
Original Research MRI of the equine stifle–61 clinical cases Alexia L. McKnight DVM, DACVR Take-home message: An area of growth in the field of equine MRI is the ability to image the stifle in adult performance horses. Numerous pathologies are easily identified in the stifle that are difficult or impossible to evaluate with any other imaging modality. Focused treatment plans can then lead to improved outcomes. Introduction: As newer regenerative therapies have advanced the field of equine medicine and surgery, magnetic resonance imaging (MRI) similarly offers significant advantages for diagnosis and prognosis. Over the past 10 years of equine MRI, much has been learned about pathologies in the distal limb, particularly in the palmar foot, pastern/fetlock, and proximal metacarpus/metatarsus, as well as in the carpus and tarsus. This lecture will review recent efforts to pioneer MRI of the stifle in performance horses. The equine stifle has not been amenable to MRI in the live performance horse, due to size constraints of the horse and the gantry. Although MRI of the stifle in the live horse has been reported using an ultra-short, wide-bore 1.5T magnet (Siemens Espree), clinical exams are not typically performed with this system due to the difficulty in positioning and size limitations of most performance horses. Here we report the clinical findings in 64 stifles from 61 performance horses (all clinical cases), following MRI examination of the stifle using a 0.25T Rotating Grande MRI system. To date, there are 5 different equine referral practices operating this scanner that currently scan the equine stifle of clinical cases: 4 in the United States, and 1 in Europe. Materials and Methods: A review of medical records was conducted to identify horses presented for clinical evaluation that had complete MRI examinations of the right or left stifle at one of the participating equine referral hospitals between April 2008 and July 2012. Specific abnormalities identified in the MRI report were then compiled, along with signalment and presenting complaint. All examinations were performed using the Esaote 0.25T Rotating Vet MR Grande system. The magnet was rotated 90o so that the bore was vertically oriented. All horses were scanned under general anesthesia in lateral/dorsal recumbency, with the hind limb of interest extended vertically so that the femorotibial joint was in the magnet isocenter. A flex coil was wrapped around the dorsal aspect of the stifle. For most all horses, the MRI protocol included PDand T2-weighted sequences, STIR, and an isotropic 3D, GE, T1 sequence.
In addition to the cases thus identified, imaging had been attempted on several particularly short-legged Quarter Horses, but the examination was aborted when it was determined that the femorotibial joint could not safely be placed in the magnet isocenter. Results: A total of 61 horses fit the selection criteria. They ranged in age from 2 years to 19 years and represented a variety of breeds, including Quarter Horse (22), Warmblood (19), Thoroughbred (4), Standardbred (2), Saddlebred (2), Morgan (2), Friesian (1), and Tennessee Walking Horse (1); the breed was unspecified in 8 cases. All but one of the horses were referred for lameness isolated to the stifle; in the other case, the MRI exam was requested by the owner without convincing clinical signs of stifle lameness. Almost all of the examinations were unilateral, with the right stifle evaluated in 27 cases and the left stifle in 31 cases; 3 exams were bilateral, for a total of 64 stifles examined in 61 horses. In 1 horse, the examination was terminated and the horse was euthanized because the prognosis was poor, but the MRI examination was completed following euthanasia. Specific abnormalities. Most horses had evidence of osteoarthritis in one or both femorotibial joints, although in some cases it was mild. Abnormalities of one or several meniscotibial ligaments (MTL) also were frequently seen, being found in most of the stifles evaluated. Abnormalities were seen more often in the craniomedial and craniolateral MTL than in the caudomedial MTL. Discrete tears and additional degenerative pathologies were often seen in both menisci, involving one or several horns. Signal abnormalities were also commonly noted in the cranial and/or caudal cruciate ligaments. Other lesions identified were femoral and tibial cystic lesions, including degenerative resorption at entheses, vascular reactions, other subchondral and bone marrow lesions, medial and lateral collateral desmitis, enostosis-like lesions, and osteochondrosis. Several horses had floating tissue fragments and numerous cases had evidence of effusion. Discussion/Conclusion: Clinical evaluation of the equine stifle is possible in the performance horse using an Esaote 0.25T Rotating Vet MR Grande MRI system. This approach provides valuable diagnostic information that is instrumental to case management. Acknowledgments: Special thanks to Equine Services Surgical Hospital in Simpsonville KY, Equine MRI of Palm Beach in Wellington, FL, Delta Equine Center in Vinton, LA, Cave Creek Equine Surgical Center in Phoenix, AZ, and Pferdeklinik Aschheim in Aschheim, Germany for performing the MRI examinations.
Practical approach to treating the laminitic horse Raul J. Bras DVM, CJF Podiatry Department, Rood and Riddle Equine Hospital, Lexington, KY Take-home message: Successful management begins with an understanding of the normal digital anatomy, the disease process, and the structural failure that results in the laminitic foot. Immediate
(Figs. 9 and 10). These disparate cases suggest that high sensitivity in reported findings is lacking, both with lowand high-field examinations. The cartilage abnormalities seen with this imaging protocol appeared as focal, multifocal, or diffuse hypointense lesions on the 3D GE T1 sequence. Although we are unsure how many clinically significant articular cartilage lesions go undetected or are underestimated using this pulse sequence, our experience (including our post mortem findings) suggests that the visible lesions are authentic. The articular lesions identified are considered abnormal findings, but their clinical significance is dependent upon the severity of the abnormalities and on the other aspects of each clinical case. The vast majority of the horses studied had other soft tissue or bony abnormalities that were deemed to be of greater clinical significance than the cartilage lesions. Furthermore, when the opposite (sound) limb was scanned for comparison, the articular findings frequently were bilateral, and in numerous cases more pronounced in the sound limb. These patterns suggest that a lot of the cartilage lesions identified were subclinical. However, the horses with advanced articular changes and/ or significant subchondral bone lesions often had clinical presentations compatible with an arthropathy. The postmortem comparison shown in Figure 10 revealed marked cartilage degeneration in the coffin joint, but the radiographs were completely unremarkable. The patient’s radiographs were rarely submitted with routine clinical MRI studies, so a correlation of radiographic abnormalities with MRI findings cannot be made from this study. In summary, various articular cartilage abnormalities are commonly seen at 0.25T in the joints of equine athletes. In our experience, the isotropic 3D GE T1 sequence used at 0.25T appears to allow acceptable evaluation of articular cartilage in the distal limb, as well as the fibrocartilage layer on the flexor margin of the navicular bone. Although most of the articular cartilage and fibrocartilage lesions described were considered mild and subclinical, the identification of more advanced lesions was critical to the diagnosis and management of the case. Acknowledgments: The authors thank all of the institutions that provided clinical scans for this review, and particularly the staff at Equine Services, LTD in Wellington, FL for assisting with some postmortem work. Disclosure: No funding or support was received for any of this clinical work. The first author provides independent MRI consultation for equine practices and others (including Universal Medical Systems, a distributor for the Esaote Vet MR Grande). References [1] Gold GE, Chen CA, Koo S, et al. Recent advances in MRI of articular cartilage. AJR Am J Roentgenol 2009;193(3):628-38. [2] Potter HG, Black BR, Chong le R. New techniques in articular cartilage imaging. Clin Sports Med 2009;28(1):77-94. [3] Olive J, D’Anjou MA, Girard C, et al. Fat-suppressed spoiled gradientrecalled imaging of equine metacarpophalangeal articular cartilage. Vet Radiol Ultrasound 2010;51(2):107-15. [4] O’Brien T, Baker TA, Brounts SH, et al. Detection of articular pathology of the distal aspect of the third metacarpal bone in thoroughbred racehorses: comparison of radiography, computed tomography and magnetic resonance imaging. Vet Surg 2011;40(8):942-51. [5] Murray RC, Branch MV, Tranquille C, et al. Validation of magnetic resonance imaging for measurement of equine articular cartilage
[6]
[7]
[8]
[9]
[10]
[11]
671
and subchondral bone thickness. Am J Vet Res 2005;66(11):19992005. Olive J, D’Anjou MA, Girard C, et al. Imaging and histological features of central subchondral osteophytes in racehorses with metacarpophalangeal joint osteoarthritis. Equine Vet J 2009;41(9):859-64. Sherlock CE, Mair TS, Ter Braake F. Osseous lesions in the metacarpo(tarso)phalangeal joint diagnosed using low-field magnetic resonance imaging in standing horses. Vet Radiol Ultrasound 2009; 50(1):13-20. Murray RC, Mair TS, Sherlock CE, et al. Comparison of high-field and low-field magnetic resonance images of cadaver limbs of horses. Vet Rec 2009;165(10):281-8. Smith MA, Dyson SJ, Murray RC. Reliability of high- and low-field magnetic resonance imaging systems for detection of cartilage and bone lesions in the equine cadaver fetlock. Equine Vet J; 2012. Werpy NM, Ho CP, Pease AP, et al. The effect of sequence selection and field strength on detection of osteochondral defects in the metacarpophalangeal joint. Vet Radiol Ultrasound 2011;52(2):154-60. Olive J. Distal interphalangeal articular cartilage assessment using low-field magnetic resonance imaging. Vet Radiol Ultrasound 2010; 51(3):259-66.
Abstracts Foot infections Raul J. Bras DVM, CJF Podiatry Department, Rood and Riddle Equine Hospital, Lexington, KY Take-home message: Most superficial infections resolve with proper drainage. If there is no improvement after 48 hours or if there is continued drainage after several days, then infection of the deeper structures should be considered. Radiography and microbial culture and sensitivity are important components of diagnosis and treatment for deep infections of the foot. Introduction: Foot infections are a common source of lameness in horses. To be able to understand infections of the foot, it is important to have a complete understanding of the complex anatomy and all the structures that could be involved. The sensitive structures of the foot are protected by the hoof capsule, which consists of the hoof wall and sole. In order for an infection to occur, the microorganisms must gain entry through this protective hoof capsule. The horse’s foot is constantly in contact and interacting with its environment, so it is susceptible to various types of trauma and injuries. The causes of foot infection include hoof capsule defects (e.g. cracks, white line disease), chronic wounds (e.g. to the digital cushion), instability (e.g. laminitis), canker, quittor (i.e. infection of the collateral or ungual cartilage), keratoma, and systemic infection. Infections of the foot can be classified as superficial or deep. Superficial Infections: Superficial infections involve the tissue between the epidermis (hoof capsule) and the underlying dermis. The majority of superficial infections are easily located and opened to establish drainage. Most of these cases show continuous improvement once drainage is established. If there is no improvement in the 48 hours after drainage is established, or if there is continued drainage after several days, then we should be concerned that deeper structures may be involved. Deep Infections: Deep infections involve any of the structures deep to the dermis: the coffin bone, digital cushion, tendons, ligaments, and synovial structures. Samples obtained from the infection site are very useful for bacteria
672
Abstracts / Journal of Equine Veterinary Science 32 (2012) 667-673
identification and antimicrobial selection. Radiography should also be used to check for involvement of deeper structures. Puncture wounds to the central region of the foot, in particular, should be treated as an emergency and all necessary diagnostic procedures performed to determine which structures are involved. It must be noted that successful treatment of foot infections depends on a good veterinarian–farrier–owner relationship.
Original Research MRI of the equine stifle–61 clinical cases Alexia L. McKnight DVM, DACVR Take-home message: An area of growth in the field of equine MRI is the ability to image the stifle in adult performance horses. Numerous pathologies are easily identified in the stifle that are difficult or impossible to evaluate with any other imaging modality. Focused treatment plans can then lead to improved outcomes. Introduction: As newer regenerative therapies have advanced the field of equine medicine and surgery, magnetic resonance imaging (MRI) similarly offers significant advantages for diagnosis and prognosis. Over the past 10 years of equine MRI, much has been learned about pathologies in the distal limb, particularly in the palmar foot, pastern/fetlock, and proximal metacarpus/metatarsus, as well as in the carpus and tarsus. This lecture will review recent efforts to pioneer MRI of the stifle in performance horses. The equine stifle has not been amenable to MRI in the live performance horse, due to size constraints of the horse and the gantry. Although MRI of the stifle in the live horse has been reported using an ultra-short, wide-bore 1.5T magnet (Siemens Espree), clinical exams are not typically performed with this system due to the difficulty in positioning and size limitations of most performance horses. Here we report the clinical findings in 64 stifles from 61 performance horses (all clinical cases), following MRI examination of the stifle using a 0.25T Rotating Grande MRI system. To date, there are 5 different equine referral practices operating this scanner that currently scan the equine stifle of clinical cases: 4 in the United States, and 1 in Europe. Materials and Methods: A review of medical records was conducted to identify horses presented for clinical evaluation that had complete MRI examinations of the right or left stifle at one of the participating equine referral hospitals between April 2008 and July 2012. Specific abnormalities identified in the MRI report were then compiled, along with signalment and presenting complaint. All examinations were performed using the Esaote 0.25T Rotating Vet MR Grande system. The magnet was rotated 90o so that the bore was vertically oriented. All horses were scanned under general anesthesia in lateral/dorsal recumbency, with the hind limb of interest extended vertically so that the femorotibial joint was in the magnet isocenter. A flex coil was wrapped around the dorsal aspect of the stifle. For most all horses, the MRI protocol included PDand T2-weighted sequences, STIR, and an isotropic 3D, GE, T1 sequence.
In addition to the cases thus identified, imaging had been attempted on several particularly short-legged Quarter Horses, but the examination was aborted when it was determined that the femorotibial joint could not safely be placed in the magnet isocenter. Results: A total of 61 horses fit the selection criteria. They ranged in age from 2 years to 19 years and represented a variety of breeds, including Quarter Horse (22), Warmblood (19), Thoroughbred (4), Standardbred (2), Saddlebred (2), Morgan (2), Friesian (1), and Tennessee Walking Horse (1); the breed was unspecified in 8 cases. All but one of the horses were referred for lameness isolated to the stifle; in the other case, the MRI exam was requested by the owner without convincing clinical signs of stifle lameness. Almost all of the examinations were unilateral, with the right stifle evaluated in 27 cases and the left stifle in 31 cases; 3 exams were bilateral, for a total of 64 stifles examined in 61 horses. In 1 horse, the examination was terminated and the horse was euthanized because the prognosis was poor, but the MRI examination was completed following euthanasia. Specific abnormalities. Most horses had evidence of osteoarthritis in one or both femorotibial joints, although in some cases it was mild. Abnormalities of one or several meniscotibial ligaments (MTL) also were frequently seen, being found in most of the stifles evaluated. Abnormalities were seen more often in the craniomedial and craniolateral MTL than in the caudomedial MTL. Discrete tears and additional degenerative pathologies were often seen in both menisci, involving one or several horns. Signal abnormalities were also commonly noted in the cranial and/or caudal cruciate ligaments. Other lesions identified were femoral and tibial cystic lesions, including degenerative resorption at entheses, vascular reactions, other subchondral and bone marrow lesions, medial and lateral collateral desmitis, enostosis-like lesions, and osteochondrosis. Several horses had floating tissue fragments and numerous cases had evidence of effusion. Discussion/Conclusion: Clinical evaluation of the equine stifle is possible in the performance horse using an Esaote 0.25T Rotating Vet MR Grande MRI system. This approach provides valuable diagnostic information that is instrumental to case management. Acknowledgments: Special thanks to Equine Services Surgical Hospital in Simpsonville KY, Equine MRI of Palm Beach in Wellington, FL, Delta Equine Center in Vinton, LA, Cave Creek Equine Surgical Center in Phoenix, AZ, and Pferdeklinik Aschheim in Aschheim, Germany for performing the MRI examinations.
Practical approach to treating the laminitic horse Raul J. Bras DVM, CJF Podiatry Department, Rood and Riddle Equine Hospital, Lexington, KY Take-home message: Successful management begins with an understanding of the normal digital anatomy, the disease process, and the structural failure that results in the laminitic foot. Immediate