NONGRAFTED AND GRAFTED OSTEOTOMIES OF PROXIMAL SESAMOID BONES OF THE HORSE

A radiographic study of healing patterns of nongrafted and grafted basilar osteotomies of proximal sesamoid bones in 14 horses was performed. Osteotomies were created in one proximal sesamoid bone of each fromt leg. One was treated by an autogenous rib graft, and the other was left nongrafted. Wedge-shaped cortical bone, corticocancellous bone with multiple drill holes, and chips of cancellous hbone were used as autogenous grafts. Presurgical, surgical, and postsurgical radiographic examinations were performed. The longest follow-up period was 40 weeks. High detail radiography of 3-mm bone sections and microangiography were also perofromed. Radiographic interpretation of lack of bone healing was erroneous in approximately one-half of the cases. Lack of an external bridging callus was incorrectly interpreted as lack of bony union. If noted, periosteal new bone formation failed to develop into a pattern of bridging callus. Radiographs did not permiit detection of the osteotomy line entering the articular surface or displacement of distal fragments. From angiography obtained ten weeks after surgery, the pattern of blood supply was similar in nontreated and grafted sesamoid bones. Microangiography showed rich vascularization of the cancellous graft and callus, reflecting good healing activity, whitle vascularization of the osteotomy site was absent in the nontreated osteotomies.     

SCINTIGRAPHIC PATTERN OF 99mTc–MDP UPTAKE IN EXERCISE INDUCED PROXIMAL PHALANGEAL TRAUMA IN HORSES

Sixty–nine horses having radionuclide bone scans of the foredigit region between 1985 and 1988 were retrospectively analyzed for proximal phalangeal cortical ^99mTc–MDP uptake. Patterns of uptake were determined and the factors of age, breed, sex, occupation, and duration of signs prior to imaging were assessed. Twenty–three horses had abnormal proximal phalangeal uptake. Two patterns of uptake were seen, either as linear, diffuse or focal, discrete, fusiform–shaped cortical uptake. The dorsal cortex was always affected in these 23 horses; the palmar cortex was affected in 14 horses, and this uptake was always linear in appearance. There was significant correlation of proximal phalangeal cortical uptake and regular jumping activity, either as a jumping, hunting or three–day event horse ( p < .005). No correlations were determined between uptake and the factors of age, breed, sex or duration of signs prior to imaging. The scintigraphic appearance patterns were similar to those seen in scintigraphic studies of exercise induced traumatic bone injuries in humans.     

RADIOGRAPHIC STUDY OF DISTAL RADIAL PHYSEAL CLOSURE IN THOROUGHBRED HORSES

Monthly radiography was performed to study distal radial physeal closure in ten male and ten female Throughbred horses. The height, thoracic circumference and metacarpus circumference were also measured. Distal radial physeal closure time was sooner in females than males, and took 701 ± 37 and 748 ± 55 days respectively.     

REPEATABILITY AND REPRODUCIBILITY OF TRANSABDOMINAL ULTRASONOGRAPHIC INTESTINAL WALL THICKNESS MEASUREMENTS IN THOROUGHBRED HORSES

The aims of this study were to assess the repeatability and reproducibility of transabdominal ultrasonography to assess intestinal wall thickness in adult Thoroughbred horses (n=8). Ultrasonographic cineloops were captured by one examiner from each horse for five consecutive days. During each examination at least three cineloops were obtained for five different intestinal tract locations. Measurements were performed by three separate observers to assess reproducibility and measured on three separate occasions by three observers to evaluate short‐term repeatability. The repeatability of measurements from the duodenum (0.3 ± 0.04 cm), jejunum (0.29 ± 0.05 cm), ventral colon (0.37 ± 0.01 cm), and cecum (0.42 ± 0.03 cm) were good ( P >0.291). The reproducibility of measurements from the duodenum, jejunum, and ventral colon were good ( P >0.394). Reproducibility of measurement of the cecal wall was inadequate ( P =0.01), although the maximum difference between observers was 0.07 cm. It was possible to image all areas on all days, with the exception of the duodenum, which could not be imaged in one horse, on 1 day. Equine intestinal wall measurements are therefore repeatable and reproducible with the exception of reproducibility of the measurements of cecal wall. Although an accepted clinical technique, measurement of cecal wall thickness from intestinal ultrasound images in a clinical setting must be interpreted with care.     

STRESS FRACTURES OF THE HUMERUS, RADIUS, AND TIBIA IN HORSES

The medical records, radiographic and nuclear scintigraphic findings of 26 racing horses with 27 stress fracture episodes of the humerus, radius, or tibia were reviewed. The purposes of this study were to describe the radiographic and/or scintigraphic features of stress fractures of the humerus, radius, or tibia, and to evaluate the signalment and history of horses in which stress fracture occurred. Stress fractures of the three long bones examined were primarily seen in 2-and 3-year-old male Thoroughbred horses; commonly, the onset of lameness was immediately following training gallops or racing. There were 13 humeral stress fracture episodes in 12 horses. Ten were in the proximal caudolateral cortex, and three were in the distal craniomedial cortex. Radial stress fractures were seen in three horses, all in the midshaft radius. Tibial stress fractures were diagnosed in 11 horses. They were located in the proximal lateral tibia in six horses, the distal caudolateral tibia in three horses, and the midshaft tibia in three horses. Fifteen stress fractures were diagnosed with radiographs alone, one was diagnosed with scintigraphy alone, nine were diagnosed with radiographs and scintigraphy, and, in two horses, radiographs were negative, but the scintigraphic findings were consistent with stress fracture.     

SCINTIGRAPHIC EVALUATION OF THE PROXIMAL METACARPAL AND METATARSAL REGIONS IN CLINICALLY SOUND HORSES

In recent years, pain arising from the proximal metacarpal and metatarsal regions has become well recognized as a cause of lameness and various disease entities have been identified. However, our knowledge of normal patterns of radiopharmaceutical uptake is limited, making interpretation of images problematic. It is therefore important to characterize normal patterns of radiopharmaceutical uptake at specific sites to ensure valid interpretation of images in clinical cases with subtle lesions. The purpose of this study was to describe the pattern of radiopharmaceutical uptake in the proximal metacarpal and proximal metatarsal regions in clinically sound horses. Scintigraphic images from 64 clinically normal horses were evaluated. All the images were assessed subjectively. The lateral, dorsal, and plantar scintigraphic images were assessed qualitatively using horizontal line profiles through the proximal metacarpal and proximal metatarsal regions. Mean ratios of radiopharmaceutical uptake were calculated from three regions of interest sited over the proximal metacarpal and proximal metatarsal regions and a reference site. In 78% of forelimbs the peak of radiopharmaceutical activity was at the dorsal to central portion of the proximal metacarpal region. Seventy-five per cent of the dorsal plane profiles of activity were symmetrical, with the highest peak over the medial to central portion of the proximal metacarpal region. In 80% of hindlimb lateral images the peak radiopharmaceutical activity was at the central to plantar aspect of the proximal metatarsal region. All (100%) plantar image profiles of activity were symmetrical, with the highest peak being over the lateral portion of the proximal metatarsal region. There was no significant left and right variation between sites for mean ratios on the lateral and dorsal images of the proximal metacarpal region. However, using lateral images the mean ratios from all regions of the right proximal metatarsal were greater than left (dorsal P = 0.003, plantar P < 0.0001 and whole proximal metatarsal, P = 0.0006). There was no significant variation in mean ratios between left and right on plantar images. However, the mean ratio for the lateral proximal metatarsal region was significantly greater than for the medial proximal metatarsal regions (P < 0.0001). There was no significant effect of age. Left/right symmetry of radiopharmaceutical uptake was shown in the proximal metacarpal region. However, there was a significant difference between left and right proximal metatarsal regions. There was higher radiopharmaceutical uptake in the right proximal metatarsal region than the left, which agrees with previous studies of the tarsal and metatarsophalangeal joints. There were differences in the pattern of radiopharmaceutical uptake between the forelimbs and hindlimbs. In the forelimbs maximum radiopharmaceutical uptake was located at the dorsal to central portion of the proximal metacarpal region in the lateral image, with peak activity over the medial to central portion of the proximal metacarpal region on dorsal images. In the hindlimbs the maximum radiopharmaceutical uptake was at the central to plantar aspect of the proximal metatarsal region in the lateral image, with peak activity over the lateral portion of proximal metatarsal region on plantar images. The results of this study support the hypothesis that there would be a standard pattern of radiopharmaceutical uptake across the proximal metacarpal and l metatarsal regions, but the pattern of uptake observed would be different in the proximal metacarpal region compared with the proximal metatarsal region. There was left/right symmetry of radiopharmaceutical uptake in the proximal metacarpal region. However, there was a significant difference between left and right proximal metatarsal regions, with higher radiopharmaceutical uptake in the right. There was no variation of radiopharmaceutical uptake pattern with age.     

IMAGING DIAGNOSIS—ARTERIAL AND VENOUS THROMBOSES OF THE PROXIMAL LIMB IN TWO THOROUGHBRED RACEHORSES

Thromboses of the cranial tibial vein (Horse 1) and brachial, median, and cranial circumflex humeral arteries (Horse 2) were identified as causes of unilateral lameness in two Thoroughbred racehorses. Nuclear scintigraphy was performed for suspicion of long bone stress fractures but instead allowed identification of unusual areas of increased radiopharmaceutical uptake within soft tissues of the affected limbs. Ultrasonography of these regions allowed identification of occlusive thrombi within a 25 cm length of the cranial tibial vein (Horse 1) and variable lengths of affected arteries in Horse 2. Horse 1 developed secondary infections and was euthanized. Staphylococcus aureus was isolated from all sites. The cause of thrombosis was not identified in Horse 2.     

MAGNETIC RESONANCE IMAGING FINDINGS IN THE EQUINE DEEP DIGITAL FLEXOR TENDON AND DISTAL SESAMOID BONE IN ADVANCED NAVICULAR DISEASE—AN EX VIVO STUDY

We describe the abnormal magnetic resonance (MR) imaging findings in the deep digital flexor tendon (DDFT) and distal sesamoid bone in horses with radiographic changes compatible with navicular syndrome. Thirteen postmortem specimens were examined using a 1.5-T magnetic field, with spin echo (SE) T1-weighted, turbo SE (TSE) proton density-weighted (with and without fat saturation), and fat saturation TSE T2-weighted sequences. The limbs were then dissected to compare the MR findings with the gross assessment and histologic examination of the DDFT and distal sesamoid bones. Tendonous abnormalities were detected by MR imaging in 12 DDFTs and confirmed at necropsy. Most tendon lesions were located at the level of the distal sesamoid bone and the proximal recess of the podotrochlear bursa. Tendon lesions were classified based on their MR imaging features as core lesions, dorsal lesions, dorsal abrasions, and parasagittal splits. Areas of increased MR signal in the DDFTs were characterized by tendon fiber disturbance and lack of continuity of the collagen fibers, foci of edema, hemorrhages, and formation of lakes containing eosinophilic plasma-like material or amphophilic material of low density. Bone marrow signal alterations in the distal sesamoid bone were seen in all digits. Two main phenomena were responsible for the abnormal signal, respectively, in T1-weighted (decreased signal) and in T2-weighted fat-suppressed images (increased signal): a decrease in the fat marrow content in the trabecular spaces and an increase in the fluid content. Histologic examination revealed foci of bone marrow edema, hemorrhage, necrosis, and fibrosis. Cyst formation and trabecular abnormalities (disorganization, thinning, remodelling) were also observed in areas of abnormal signal intensity. Increased bone density because of trabecular thickening induced a decrease in signal in all sequences.     

CLINICAL, MAGNETIC RESONANCE, AND SONOGRAPHIC IMAGING FINDINGS IN HORSES WITH PROXIMAL PLANTAR METATARSAL PAIN

Sonography is commonly used for diagnosis of desmopathy of the proximal part of the suspensory ligament in horses. However, magnetic resonance (MR) imaging has been stated to be superior for detecting disease and localizing lesions. In this retrospective study of 39 horses or 46 hind limbs with lameness due to proximal plantar metatarsal pain, the clinical and diagnostic findings are discussed and sonography and MR imaging compared for examination of the proximal part of the suspensory ligament. With MR imaging interpreted as the clinical gold standard, desmopathy of the proximal part of the suspensory ligament was diagnosed in 21 hind limbs, proximal plantar metatarsal pain of unknown cause in 12, an osseous injury at the origin of the suspensory ligament in four and a condition unrelated to the suspensory ligament in nine. Based on these findings, sonography had a sensitivity of 0.77 and 0.66 and specificity of 0.33 and 0.31 for diagnosing proximal suspensory desmopathy and for accurately localizing lesions, respectively. MR imaging changes consistent with proximal suspensory desmopathy were signal hyperintensities and an increase in cross-sectional area compared with the contralateral limb. Anesthesia of the deep branch of the lateral plantar nerve is not specific neither for proximal suspensory desmopathy, as conditions unrelated to the suspensory ligament were diagnosed, nor for diagnosis of proximal plantar metatarsal pain, as conditions outside the proximal plantar metatarsal region were also diagnosed.     

THE DORSOPROXIMAL-DORSODISTAL PROJECTION OF THE DISTAL CARPAL BONES IN HORSES: AN EVALUATION OF DIFFERENT BEAM-CASSETTE ANGLES

To estimate the extent of the third carpal bone (C3) visible for evaluation in the dorsoproximal-dorsodistal oblique projection of the distal row of carpal bones, 13 forelimbs collected at post mortem from 7 horses were examined radiographically. The limbs were frozen with the carpal joints flexed then radiographed using fixed beam-cassette angles of 15 degrees to 45 degrees, at 5 degree intervals. The influence of beam-cassette angle on; the depth of the proximal articular surface examined, the radiographic appearance of C3 and the assessment of subchondral sclerosis was evaluated. Beam-cassette angles of 25 degrees to 40 degrees produced subjectively acceptable radiographs and did not appear to influence assessments of sclerosis. The mean depth of the examined proximal articular surface of the C3 increased significantly with each 5 degree increase in beam-cassette angle up to 40 degrees. The use of beam-cassette angles >35 degrees is recommended for the DPr-DDiO projection.     

PREVALENCE AND DISTRIBUTION OF THE FIRST AND FIFTH CARPAL BONES IN STANDARDBRED HORSES AS DETERMINED BY RADIOGRAPHY

In a radiographic study of 200 Standardbred horses, a first carpal bone was observed unilaterally in 21 (10.5%) horses and bilaterally in 45 (22.5%) horses. There was no significant effect of sex on the absence or presence of the first carpal bone. No fifth carpal bone was seen in this study.     

结症马的血流动力学初探

用无创伤性血流动力学方法对患结症的马进行了探讨,结果表明病马有不同程度的血流动力学异常。表现在SV、SI、VPE、LVWI、PP、FEK、MHR的明显降低(p<0.01～0.05)和PAWP、TPR、MPT的明显升高(0.01～0.05),说明患结症的马存在着心脏功能的异常和血液循环障碍。     

IMAGING FEATURES OF DISCOSPONDYLITIS IN TWO HORSES

Two horses with discospondylitis are described with emphasis on the imaging modalities used and their contribution to the final diagnosis and outcome. Radiographic findings were vertebral endplate lysis with sclerosis in both horses, with additional vertebral subluxation and ventral spondylosis in one horse. Ultrasonographic findings included vertebral malalignment and obliteration of the intervertebral disc by spondylotic bone in one horse and irregular endplates, a widened disc space, a hypoechoic paravertebral abscess and hypoechoic, atrophic adjacent musculature with loss of linear fiber pattern in the other horse. Bone scintigraphy excluded additional affected sites. A systematic approach is recommended when performing an ultrasound examination of the spine.     

POWER DOPPLER ASSESSMENT OF THE NEOVASCULARIZATION DURING UNCOMPLICATED FRACTURE HEALING OF LONG BONES IN DOGS AND CATS

The aims of this prospective study were to test the feasibility of assessing neovascularization with power Doppler ultrasonography and to investigate its usefulness to follow fracture healing of long bones in dogs and cats. A total of 51 patients (44 dogs and seven cats) were followed. Fracture types differed from simple to comminuted. Therapy ranged from external coaptation to plate osteosynthesis. Patients were followed with radiography, B-mode real time and power Doppler ultrasonography every 2-4 weeks until the fracture was healed. All fractures healed uneventfully. A semi-quantitative numerical score based on signal intensity, vessel area, and number of Doppler signals was assigned and the mean value was used to compare patients and examinations. Time postoperatively was divided into periods of 10 days. No Doppler signal was present during the first 10 days. The mean of the scores was highest between 11 and 20 days postoperatively and the median of the scores peaked between 21 and 30 days. A gradual decrease was seen thereafter. The mean of the scores was zero at 71-80 days and the median at 51-0 days postoperatively for the grouped results. In all positive power Doppler examinations, signals were present in and close to the callus. In seven patients (five dogs and two cats) signals were also present in the peripheral soft tissues in one of the follow up examinations. The normal healing process of fractured bones can be visualized using power Doppler ultrasonography and follows a distinctive time-dependent pattern.     

CLINICAL AND DIAGNOSTIC IMAGING FINDINGS IN HORSES WITH SUBCHONDRAL BONE TRAUMA OF THE SAGITTAL GROOVE OF THE PROXIMAL PHALANX

Eight sports horses with unilateral (4) or bilateral (3) forelimb or unilateral hindlimb (1) lameness had subtle radiologic abnormalities of the subchondral bone of the sagittal groove of the proximal phalanx associated with moderate or intense increased radiopharmaceutical uptake. High‐field or low‐field magnetic resonance (MR) imaging confirmed the presence of a fissure fracture or subchondral and trabecular bone trauma. Seven of eight lesions were located approximately midway between the dorsal and palmar cortices of the proximal phalanx; the eighth was sited more dorsally. Two horses underwent follow‐up MR imaging and abnormal signal intensity persisted, with little change.     

COMPUTED TOMOGRAPHY IN HORSES

Computed tomography (CT) is a valuable imaging procedure but one that requires significant technical support. Although scanners are available for veterinary use, their successful installation requires in-depth facility planning. Maintenance costs for these highly complex systems are high and may greatly exceed acquisition costs. Equipment to move anesthetized horses and support them during scanning is also expensive. Transport and scan table equipment suitable for equine CT studies are described. Clinical scan protocols used for CT of the equine skull and extremities are detailed. Precise positioning is essential for interpretable scans. Significant training in anatomy and CT physics is required for the veterinary computed tomographer.     

AORTO-CARDIAC FISTULAS IN SEVEN HORSES

This report describes the history, clinical, electrocardiographic and echocardiographic findings, treatment, outcome, and post-mortem findings in seven horses with aorto-cardiac fistula. Affected horses included 5 stallions, one gelding and one mare; 2 each of the Thoroughbred, Arabian and Standardbred breeds and one Thoroughbred-cross with a mean ± s.d. age of 12 ± 4 years, range 6–18 years. The presenting sings were acute distress (four horses), exercise intolerance (two horses) and the lesion was detected during a routine examination in one horse. Five horses had monomorphic ventricular tachycardia on admission and one other had a history of this arrhythmia. Five horses had a characteristic continuous murmur loudes in the right fourth intercostal space. Echocardiography (six horuses) and/or post-mortem examination (four horses) revealed the horses had aorto-cardiac fistulas arising from the right aortic sinus in all five horses in which the site was recorded. Two horses had ruptured aneurysmall dilatations of the aortic wall at this site. Fistulas extended into the right ventricle in four horses; the right atrium in two horses, the left ventricle in one horse, and five horses had dissecting tracts in the septal myocardium. Horses survived for periods ranging from 24th to 4 years. Aorto-cardiac fistula should be considered in the differential diagnosis for horses presenting with acute distress, bounding arterial pulse, a right-sided continuous murmur and/or monomorphic ventricular tachycardia, particularly in middle-aged or older stallions. Echocardiography is the technique of choice for confirming the diagnosis and demonstrating accompanying cardiac changes.