ULTRASONOGRAPHY OF THE EQUINE STIFLE

Ten stifles from 5 clinically sound adult horses were scanned by high-resolution ultrasound. Normal anatomic structures seen consistently included the subcutaneous tissue, the medial, middle and lateral patellar ligaments, the medial and lateral collateral ligaments, the femoral trochlear ridges, and menisci. Cruciate ligaments could not be visualized in the standing horse. Four stifle specimens obtained from 2 of these normal horses at necropsy were scanned in a water bath to create optimal technical conditions. The sonographic appearance of stifle specimens was similar to that found in live horses. Results from ultrasonographic examination of 3 horses with stifle abnormalities were described to illustrate some applications of ultrasonography in the evaluation of the equine stifle. In these horses, ultrasound was a valuable diagnostic tool to study joint effusion, synovial thickening, articular cartilaginous and subchondral defects, and soft tissue/bony injuries.     

COMPUTED TOMOGRAPHIC ARTHROGRAPHY OF THE NORMAL CANINE STIFLE

Computed tomographic (CT) imaging of eight normal cadaveric canine stifles was performed before and after intra-articular administration of iodinated contrast medium. Transverse CT images were reconstructed in dorsal, parasagittal, and oblique planes. The following ligamentous structures were identified on transverse CT images in all stifles: cranial cruciate ligament, caudal cruciate ligament, medial meniscus, lateral meniscus, and the medial and lateral collateral ligaments. The following ligamentous structures were identified on transverse computed tomographic arthrography (CTA) images in all stifles: cranial cruciate ligament, caudal cruciate ligament, medial meniscus, lateral meniscus, meniscofemoral ligament, cranial meniscotibial ligaments, caudal meniscotibial ligaments, intermeniscal (transverse) ligament, and the medial and lateral collateral ligaments. The patellar tendon was identified on transverse and reconstructed dorsal and sagittal CT and CTA images in all stifles. Multiplanar reconstructions enabled further evaluation of the continuity of the cranial and caudal cruciate ligaments and menisci. The medial and lateral collateral ligaments were not clearly identified on CT or CTA multiplanar reconstructed images.     

LOW-FIELD MAGNETIC RESONANCE IMAGING OF THE CANINE STIFLE JOINT: NORMAL ANATOMY

Low-field magnetic resonance imaging (MRI) was performed on the stifle joints of four normal adult mongrel dogs using a 0.064 Tesla scanner. Markers were placed on each stifle joint to serve as reference points for comparing gross sections with the images. A T1-weighted sequence was used to image one stifle joint on each dog in the sagittal plane and the other stifle joint in the dorsal plane. The dogs were euthanized immediately following MRI and the stifle joints frozen intact. Each stifle joint was then embedded in paraffin, again frozen, and sectioned using the markers as reference points. On T1-weighted images, synovial fluid had low signal intensity (dark) compared to the infrapatellar fat pad which had a high signal intensity (bright). Articular cartilage was visualized as an intermediate bright signal and was separated from trabecular bone by a dark line representing subchondral bone. Menisci, fibrous joint capsule, and ligamentous structures appeared dark. In the true sagittal plane, the entire caudal cruciate ligament was often seen within one image slice. The patella was visualized as an intermediate bright signal (trabecular bone) surrounded by a low intensity signal (cortical bone). The trochlea and the intercondylar notch were difficult areas to analyze due to signal volume averaging of the curved surface of these areas and the presence of several types of tissues.     

SONOGRAPHY OF THE CANINE STIFLE

When diagnosing disease of the stifle in dogs ultrasonography is a good addition to clinical and radiological examination. Radiology can evaluate the bony aspects of the joint and their relationship to each other. In contrast, sonography allows visualization of the soft tissue. For most evaluations the 7.5 MHz linear scanner is suited best. Normal stifles of 58 dogs of different breeds were evaluated using a standardized examination procedure. This procedure had been derived from that used in humans. The stifle is divided into several regions which are examined and evaluated. These are the suprapatellar, infrapatellar, lateral, caudal and medial region. One hundred twenty seven patients which had problems associated with the stifle joint were examined sonographically after a clinical and radiographic exam. Osteochondrosis dissecans, ruptured cranial cruciate ligament, meniscal damage, arthritis, tumor, post surgical conditions, injuries of the patella, patellar ligament or tibial tuberosity and luxating patella were examined sonographically and the findings recorded.     

NORMAL ULTRASONOGRAPHIC ANATOMY OF THE CANINE NECK

High-resolution, real-time ultrasonographic examinations of the neck were performed on eight normal dogs maintained under general anesthesia. Water-soluble dye was injected into imaged structures under sonographic guidance in two dogs. The anatomy of the neck was verified at postmortem by visualization of dye deposited in the injected structures. Anatomical mapping was then completed by performing complete cervical ultrasound examinations in the remaining six dogs. Normal ultrasonographic anatomy of the canine neck and major anatomic landmarks useful in clinical imaging are described.     

LONG-STANDING AND TRAUMATIC LIGAMENT INJURIES AND MENISCAL RUPTURES OF THE CANINE STIFLE

Stifle joint lesions, especially in large dogs, have been recognized since 1899, but not until 1943 was a detailed study of meniscal lesions published. Further study led to the publication in 1952 of a major study that demonstrated that dogs with long-standing injury of the stifle joint commonly displayed rupture of the cranial cruciate ligament, medial meniscal tear, and degenerative joint disease. From this study came the well-known Paatsama operation. Treatment of cruciate ligament rupture has been done using new materials in the intervening years, but the same basic principles have been followed.     

ECHOGRAPHIC EXAMINATION OF THE STIFLE JOINT AFFECTED BY CRANIAL CRUCIATE LIGAMENT RUPTURE IN THE DOG

Ultrasound is a useful technique for the study of normal and pathologic stifle joints, in particular for soft tissue examination. The aim of this study was to evaluate sonography for examination of stifle joints affected by cranial cruciate ligament rupture. Forty-two medium to giant breed dogs were studied. Tibial compression radiography was performed. A 7.5 MHz transducer with an incorporated 2 cm thick standoff was employed. Sagittal and midsagittal images were collected. The stifle was positioned in maximum flexion during sonography. Sonographic findings were compared with pathologic findings at surgery. Ultrasound was useful in evaluating the presence of fibrous tissue within the joint due to repair processes. It was observed in 70% of stifles with radiographic evidence of chronic osteoarthritis. In 19.6% of the joints it was possible to identify the ruptured cranial cruciate ligament. Ultrasound was not an accurate test for cruciate rupture evaluation, but was specific for the soft tissue pathologic changes which were observed consequent to joint instability.     

ULTRASONOGRAPHIC ANATOMY OF THE NORMAL CANINE CALCANEAL TENDON

To provide a series of detailed ultrasonographic images of the canine calcaneal tendon, greyhound cadaver pelvic limbs were scanned with a high-resolution transducer, and images compared with dissected specimens. The three components of the calcaneal tendon are the tendons of insertion of the gastrocnemius, superficial digital flexor, and a conjoined tendon formed by tendons from the biceps femoris, semitendinosus, and gracilis. Each of these three tendons was visible in transverse ultrasound images, each measuring 2.4-3.2-mm thick at mid-calcaneal tendon. Improved understanding of the anatomy of the calcaneal tendon will support clinical ultrasonography of this region.     

EFFECTS OF STIFLE FLEXION ANGLE AND SCAN PLANE ON VISIBILITY OF THE NORMAL CANINE CRANIAL CRUCIATE LIGAMENT USING LOW‐FIELD MAGNETIC RESONANCE IMAGING

Low‐field magnetic resonance imaging (MRI) is commonly used to evaluate dogs with suspected cranial cruciate ligament injury; however, effects of stifle positioning and scan plane on visualization of the ligament are incompletely understood. Six stifle joints (one pilot, five test) were collected from dogs that were scheduled for euthanasia due to reasons unrelated to the stifle joint. Each stifle joint was scanned in three angles of flexion (90°, 135°, 145°) and eight scan planes (three dorsal, three axial, two sagittal), using the same low‐field MRI scanner and T2‐weighted fast spin echo scan protocol. Two experienced observers who were unaware of scan technique independently scored visualization of the cranial cruciate ligament in each scan using a scale of 0–3. Visualization score rank sums were higher when the stifle was flexed at 90° compared to 145°, regardless of the scan plane. Visualization scores for the cranial cruciate ligament in the dorsal (H (2) = 19.620, P = 0.000), axial (H (2) = 14.633, P = 0.001), and sagittal (H (2) = 8.143, P = 0.017) planes were significantly affected by the angle of stifle flexion. Post hoc analysis showed that the ligament was best visualized at 90° compared to 145° in the dorsal (Z = ?3.906, P = 0.000), axial (Z = ?3.398, P = 0.001), and sagittal (Z = ?2.530, P = 0.011) planes. Findings supported the use of a 90° flexed stifle position for maximizing visualization of the cranial cruciate ligament using low‐field MRI in dogs.     

ULTRASONOGRAPHIC ANATOMY OF THE CANINE ELBOW

To produce detailed ultrasonographic images of the soft tissue structures around the canine elbow joint, a series of greyhound cadaver limbs were scanned both intact and dissected in a water bath. Suitable transducer positions and bone landmarks are described and the ultrasonographic appearance of the lateral collateral ligament, anconeal process, triceps tendon, origin of olecranon ligament, biceps tendon insertion, medial collateral ligament, and medial coronoid process are illustrated. Improved understanding of the anatomy of the canine elbow will support clinical ultrasonography of this region.     

ULTRASONOGRAPHIC ANATOMY OF THE NORMAL CANINE KIDNEY*

Radiographic and ultrasonic examinations were performed in 12 normal dogs. Initial ultrasound examinations were performed in normally hydrated dogs. The ultrasonic appearance of the diuresed kidney was evaluated after excretory urography and intramuscular administration of furosemide. The dogs were euthanized for anatomic correlation with the sonographic appearance of the kidneys. Renal cortex, medulla, pelvic diverticula, intrarenal vessels, renal pelvis, and renal sinus fat were identified sonographically. Kidney enlargement during diuresis was due to increase renal medullary size. Veterinary Radiology, Vol. 25, No. 4, 1984; pp 173–178.     

THE USE OF SMALL FIELD‐OF‐VIEW 3 TESLA MAGNETIC RESONANCE IMAGING FOR IDENTIFICATION OF ARTICULAR CARTILAGE DEFECTS IN THE CANINE STIFLE: AN EX VIVO CADAVERIC STUDY

Noninvasive identification of canine articular cartilage injuries is challenging. The objective of this prospective, cadaveric, diagnostic accuracy study was to determine if small field‐of‐view, three tesla magnetic resonance imaging (MRI) was an accurate method for identifying experimentally induced cartilage defects in canine stifle joints. Forty‐two canine cadaveric stifles (n = 6/group) were treated with sham control, 0.5, 1.0, or 3.0 mm deep defects in the medial or lateral femoral condyle. Proton density‐weighted, T1‐weighted, fast‐low angle shot, and T2 maps were generated in dorsal and sagittal planes. Defect location and size were independently determined by two evaluators and compared to histologic measurements. Accuracy of MRI was determined using concordance correlation coefficients. Defects were identified correctly in 98.8% (Evaluator 1) and 98.2% (Evaluator 2) of joints. Concordance correlation coefficients between MRI and histopathology were greater for defect depth (Evaluator 1: 0.68–0.84; Evaluator 2: 0.76–0.83) compared to width (Evaluator 1: 0.30–0.54; Evaluator 2: 0.48–0.68). However, MRI overestimated defect depth (histopathology: 1.65 ± 0.94 mm; Evaluator 1, range of means: 2.07–2.38 mm; Evaluator 2, range of means: 2–2.2 mm) and width (histopathology: 6.98 ± 1.32 mm; Evaluator 1, range of means: 8.33–8.8 mm; Evaluator 2, range of means: 6.64–7.16 mm). Using the paired t‐test, the mean T2 relaxation time of cartilage defects was significantly greater than the mean T2 relaxation time of adjacent normal cartilage for both evaluators (P < 0.0001). Findings indicated that MRI is an accurate method for identifying cartilage defects in the cadaveric canine stifle. Additional studies are needed to determine the in vivo accuracy of this method.     

MAGNETIC RESONANCE IMAGING OF THE EQUINE STIFLE

The purpose of this study was to define normal gross anatomic structures in the equine stifle with magnetic resonance images. Magnetic resonance (MR) images were made in sagittal, 15° supinated, transverse, and dorsal planes of two equine stifles. The MR images were scrutinized by comparing MR images to dissection specimens and frozen cross sections of stifle joints. Sagittal and 15° supinated images were the most valuable in assessing articular cartilage, subchondral bone, and soft tissue structures within the joint. Cranial and caudal cruciate ligaments, medial and lateral menisci, meniscotibial and meniscofemoral ligaments, long digital extensor tendon, and patellar ligaments were easily evaluated. MR images provided substantially more gross anatomical information than the currently available imaging modalities.     

ULTRASONOGRAPHIC EVALUATION OF CRANIAL CRUCIATE LIGAMENT RUPTURE VIA DYNAMIC INTRA-ARTICULAR SALINE INJECTION

Ultrasonographic examination of both stifle joints of five clinically and radiographically normal adult dogs was performed before and after surgical transection of the cranial cruciate ligament (CrCL). At pre- and postsurgery, the hyperechoic patellar ligament and the infrapatellar fat interfered with sonographic visualization of the CrCL. When the stifle joint, however, was imaged via dynamic intra-articular saline injection, the hyperechoic ligament was visualized because of the separation of the infrapatellar fat and the CrCL and the contrasting effect of anechoic saline. When the stifle joint was imaged by real-time scanning after the transection of the CrCL, flutter of the ligament and an anechoic area between the bone and the CrCL were identified. The increased diameter of the ligament and the increased thickness of the joint space were identified as well. Ultrasonographic examination via dynamic saline injection into the joint space has potential as a diagnostic tool for assessing CrCL rupture.     

MAGNETIC RESONANCE ARTHROGRAPHY OF THE CANINE STIFLE JOINT TECHNIQUE AND APPLICATIONS IN ELEVEN MILITARY DOGS

The stifle joints of eleven military working dogs were evaluated using conventional magnetic resonance (MR) imaging and MR arthrography. A protocol optimizing MR imaging of the canine stifle joint is discussed, as well as potential uses for administration of intra-articular gadolinium. The technique for performing MR arthrography is described, and post-contrast image findings are reviewed. MR arthrography was performed by using an intra-articular injection of diluted gadolinium. Consistently good quality images were obtained, and no complications were clinically detected following MR arthrography. Cranial cruciate ligament abnormalities were seen in six dogs, meniscal abnormalities were visualized in nine menisci, and synovitis and medial ligament strain were seen in eight dogs. Surgical and post-mortem confirmation of these findings is discussed in seven dogs. Although MR arthrography adds an invasive procedure to conventional MR imaging, it can provide useful information on pathologic changes in the canine stifle joint.     

PREVALENCE,ASSOCIATION WITH STIFLE CONDITIONS,AND HISTOPATHOLOGIC CHARACTERISTICS OF TIBIAL TUBEROSITY RADIOLUCENCIES IN DOGS

A tibial tuberosity radiolucency is sometimes identified on lateral radiographs of canine stifle joints, however little is known about the cause or significance. The purpose of this study was to describe the prevalence, association with other stifle conditions, and histopathologic characteristics of tibial tuberosity radiolucencies in a group of dogs. Radiographs of all canine stifle joints over 5 years were evaluated. Presence or absence of a tibial tuberosity radiolucency was recorded by an observer who was unaware of clinical status. Patient signalment and presence of other stifle joint conditions were recorded from medical records. A tibial tuberosity radiolucency was found in 145/675 dogs (prevalence = 21.5%). Statistically significant associations were identified between tibial tuberosity radiolucency and stifle condition (P < 0.0001), breed size (P = 0.011), and younger age of presentation (P = 0.001), but not with gender (P = 0.513). Dogs with a tibial tuberosity radiolucency had higher odds of having a medial patellar luxation than dogs without (OR = 9.854, P < 0.0001, 95% CI 6.422–15.120). Dogs with a tibial tuberosity radiolucency had lower odds of having a cranial cruciate ligament rupture than dogs without (OR = 0.418, P < 0.0001, 95% CI 0.287–0.609). Four canine cadavers, two with normal stifles and two with tibial tuberosity radiolucencies, underwent radiographic, computed tomographic, and histologic examination of the stifles. Computed tomography revealed a hypoattenuating cortical defect in the lateral aspect of the proximal tibial tuberosity that corresponded histopathologically to a hyaline cartilage core. Findings indicated that the tibial tuberosity radiolucency may be due to a retained cartilage core and associated with medial patellar luxation in dogs.     

PARTIAL AVULSION OF THE ORIGIN OF THE CRANIAL CRUCIATE LIGAMENT IN A 4 YEAR-OLD DOG

A four year-old intact male Dalmatian was referred to the veterinary teaching hospital at Louisiana State University for acute, non-weight-bearing left hindlimb lameness of three weeks duration. Information supplied by the referring veterinarian indicated the lameness was first diagnosed and treated seven months previously, but recurred three weeks ago. External rotation of the left stifle, mild discomfort upon stifle flexion, mild to moderate muscle atrophy and palpable joint effusion were noted during physical examination. Slight cranial drawer movement with a soft end-point was discovered during manipulation of the left stifle. A triangular bone fragment and thickened, confluent intracapsular soft tissues were observed on radiographs of the stifle. Radiographically, moderate degenerative changes suggested chronicity. This report describes the clinical and radiographic findings of a rarely reported partial avulsion of the origin of the cranial cruciate ligament in a skeletally mature dog.     

ULTRASONOGRAPHIC ANATOMY OF THE NORMAL CANINE SPINAL CORD AND CORRELATION WITH HISTOPATHOLOGY AFTER INDUCED SPINAL CORD TRAUMA

Prior to trauma, intraoperative ultrasound of the spinal canal in 31 normal dogs was performed through a hemilaminectomy in the left pedicle of L2. A ventral compressive model of spinal cord injury was performed as part of a clinical drug trial. Maximum ultrasonographic spinal cord diameter ranged from 4.9–7.2 mm (5.7 × 0.6). Significant positive correlation (p = 0.023, r = 0.49) was found between age and spinal cord diameter. The dura mater was a separate, well-defined, echogenic horizontal line in 28 (90%) dogs, dorsally, and in 29 (94%) dogs, ventrally. Cerebrospinal fluid was anechoic. Eighteen (58%) dogs had a well-defined anechoic dorsal subarachnoid space, whereas 22 (71%) had a well-defined ventral space. Pia mater was thin but strongly echogenic and covered spinal cord. Central canal was a double hyperechoic line in 17 (55%) dogs and a single-line in 14 (45%) dogs. A difference in the ultrasonographic appearance between gray and white matter was not seen. Epidural fat and connective tissue was a lobular echogenic material in the ventral epidural space. The periosteal-vertebral body interface was seen as a bright curvilinear echo with distal acoustic shadowing. Spinal cord parenchyma could be classified subjectively into four groups based upon ultrasonographic appearance. Spinal cord parenchyma had a uniform hypoechogenicity in 8 (27%) dogs (Group 1), subtle low level echoes in 7 (23%) dogs (Group 2), multiple clusters of defined echogenic foci in 12 (37%) dogs (Group 3), and multiple sharply-defined linear echoes in 4 (13%) dogs (Group 4). There was a significant relationship between pre-trauma ultrasonographic appearance of the spinal cord and histopathology 21 days after trauma. One (13%) dog in Group 1, 4 (57%) dogs in Group 2,10 (91%) dogs in Group 3, and 3 (75%) dogs in Group 4 had malacia on histological evaluation. Therefore, dogs with echogenic spinal cords or linear echoes within cord parenchyma were significantly more likely to develop malacia rather than Wallerian degeneration after induced spinal cord trauma (p = 0.002). Spinal cord echogenicity may indicate vascularity in a segment of spinal cord and might be prognostic following spinal cord trauma. No complications were found related to intraoperative ultrasound. Hematoma or fibrous tissue formation appeared to impede percutaneous ultrasound of the spinal cord in dogs re-evaluated forty-eight hours and one week after surgery.     

ULTRASONOGRAPHIC DESCRIPTION OF CANINE MASTITIS

Ultrasonographic images were acquired of the mammary glands of 40 bitches with physiologically lactating (n = 20) or inflamed glands (n = 20). Echogenicity, structure, homogeneity, thickness, and distinguishability of each tissue layer were assessed. Additionally, overall echogenicity was noted. In the normal lactating gland, different tissues could be differentiated easily. The parenchyma was, without exception, separated from adjacent tissues and was visible as medium echogenic tissue with a coarse-grained structure. The tissue always had some echogenic lines and anechoic areas and was slightly heterogeneous. The loss of distinct layering of the tissue was characteristic of an inflamed mammary gland and inflamed regions had reduced echogenicity. Additionally in five bitches with mastitis, the ultrasound examination was repeated five times for documentation of the progress of the illness and associated changes, supplemented with a color Doppler sonogram to assess changes in blood vessel density. Information from the examinations carried out via B-mode did not allow treatment success to be predicted. Two bitches with reduced blood vessel density centrally had a poor outcome whereas three bitches with increased blood vessel density had a good outcome. Thus, Doppler sonography might be a useful tool to obtain information of the prognosis in acute canine mastitis.