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 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.     

RADIOGRAPHIC ASSESSMENT OF CRANIAL CRUCIATE LIGAMENT RUPTURE IN THE DAIRY COW

Case records and radiographs of 37 dairy cows presented to the University of Illinois Veterinary Medicine Teaching Hospital with a diagnosis of cranial cruciate ligament rupture were reviewed. Signalment, history, duration of lameness prior to clinical presentation, and physical examination findings were evaluated. Survey radiographs were examined and radiographic lesions were documented. Individual cows were classified into groups (A, B, C) based on the severity of radiographic lesions, with Group A cows having minimal radiographic lesions. Cows in Groups A and B had radiographic lesions similar to Class I in beef bulls reported in another study.^3,4 An attempt was made to relate the severity of radiographic lesions with age and duration of lameness. Group A animals tended to be younger cows (x?= 4.58 years) with a short duration of lameness. Group B cows were older (x?= 7.87 years) with a somewhat longer duration of lameness. Group C cows were slightly younger (x?= 7.30 years) than Group B cows; however, their duration of lameness was much longer (x?= 57.2 weeks vs 6.35 weeks for Group B and 2.54 weeks for Group A). The pathogenesis of cranial cruciate ligament rupture and its associated lameness appeared to differ in dairy cows from beef bulls. The majority of animals in this study had radiographic lesions of mild to moderate severity (Groups A and B). In contrast, based on previous work, beef bulls had a greater tendency to be similar to our Group C designation. Beef bulls became lame with cranial cruciate ligament rupture only after severe lesions of degenerative joint disease had already occurred. It has been stated that lameness associated with cranial cruciate ligament rupture in the beef bull is, therefore, secondary to degenerative joint disease. In contrast, the syndrome in dairy cows, as evidenced here, differs, since they often presented with cranial cruciate ligament rupture with little or no radiographic evidence of degenerative joint disease.     

LOW-FIELD MAGNETIC RESONANCE IMAGING OF EARLY SUBCHONDRAL CYST-LIKE LESIONS IN INDUCED CRANIAL CRUCIATE LIGAMENT DEFICIENT DOGS

Six healthy adult male mongrel dogs underwent cranial cruciate ligament transection in the left stifle. Survey radiography of both stifles and low-field (0.064 T) MRI of the left stifle were performed preoperatively and at 2, 6, and 12 weeks postoperatively. Focal changes in signal intensity were seen with MRI in the subchondral bone of the medial tibial condyle at 2 and 6 weeks postoperatively. At 12 weeks postoperative, a cyst-like lesion was detected using MRI in the subchondral bone of the medial tibial condyle in 4 of 6 dogs and a less defined lesion at this site in the remaining 2 dogs. The cyst-like lesion was spherical in shape and showed typical characteristics of fluid with low signal intensity on T1-weighted images, high signal intensity on T2-weighted images and high signal intensity on inversion recovery images. The lesion was seen in the subchondral bone of the caudal medial and/or middle region of the tibial plateau slightly cranial to the insertion of the caudal cruciate ligament. No subchondral cysts were seen in the tibia on radiographs. Histopathologically, the tibia was characterized by a loose myxomatous phase of early subchondral cyst formation.     

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.     

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.     

ABERRANT ORIGIN OF THE CRANIAL CRUCIATE LIGAMENT MIMICKING AN OSTEOCHONDRAL LESION RADIOGRAPHICALLY: A CASE HISTORY REPORT

An aberrant cranial cruciate ligament mimicked an osteochondral lesion of the lateral femoral condyle in a young dog. This rare condition was diagnosed at surgery. At a four-year follow-up, no radiographic evidence of the apparent osteochondral defect was seen.     

COMPUTED TOMOGRAPHIC ARTHROGRAPHY OF THE STIFLE FOR DETECTION OF CRANIAL AND CAUDAL CRUCIATE LIGAMENT AND MENISCAL TEARS IN DOGS

The purpose of this study was to evaluate the utility of single-detector computed tomographic arthrography (CT arthrography) for the diagnosis of cranial and caudal cruciate ligament and meniscal lesions in the dog stifle. Four normal and 25 abnormal stifle joints, determined to have lesions related to intra-articular ligamentous insufficiency based on clinical history, orthopedic examination, and survey orthogonal radiographs, were imaged using a previously developed CT arthrography protocol. Surgery was performed immediately following the CT procedure. Three board-certified radiologists inexperienced at interpreting CT stifle arthrograms reviewed all CT studies independently, and then as a group, without knowledge of surgical or necropsy findings. Sensitivity, specificity, positive predictive value, and negative predictive value for determination of cranial and caudal cruciate and meniscal tears were calculated for each individual reviewer and based on group consensus. All reviewers identified the normal canine stifle joints imaged correctly. Reviewers did well in discriminating normal from torn cranial cruciate ligaments, with sensitivities of 96–100% and specificities of 75–100%. No reviewer correctly identified the solitary caudal cruciate ligament tear and specificity ranged from 89.3% to 100%. Reviewers were less adept at discriminating normal from torn meniscal fibrocartilage, with sensitivities of 13.3–73.3% and specificities of 57.1–100%. Interpretive accuracy improved slightly when consensus scores were compared with surgical findings. Single-detector CT arthrography may be useful for identifying pathology of the canine cruciate ligaments but is of limited value for assessing the menisci.     

MORPHOMETRIC ASSESSMENT OF THE PROXIMAL PORTION OF THE TIBIA IN DOGS WITH AND WITHOUT CRANIAL CRUCIATE LIGAMENT RUPTURE

Based on the clinical observation that dogs with a steep tibial plateau slope had variable tibial morphology, we hypothesized that these dogs could be further characterized using measurements developed by examining computer generated models of specific proximal tibial malformations. A 3D tibial model was created from a normal canine tibia. The model was manipulated to reproduce two specific proximal tibial anomalies representing deformities originating from the tibial plateau or the proximal tibial shaft. Data from these models were used to create specific measurements that would characterize the shape of these anomalies. These measurements included the diaphyseal tibial axis (DTA)/proximal tibial axis (PTA) angle, which defined the orientation of the proximal portion of the shaft in relation to the tibial mid-shaft. These measurements were then made on radiographs of dogs with and without cranial cruciate ligament (CCL) rupture. Models with tibial plateau and proximal shaft deformities had a steep tibial plateau slope (TPS). Models with proximal shaft deformity had a markedly increased DTA/PTA angle. The model with a 10 degree proximal shaft deformity had a DTA/PTA angle of 11.23 degrees. Six dogs (9.0%) had a DTA/PTA angle larger than 11.23 degrees (range, 11.4-13.9 degrees). Dogs in this group had ruptured CCL and a steep TPS. Dogs with CCL rupture had higher TPS (mean, 31.8 +/- 4.1 degrees) and DTA/PTA angle (mean, 6.0 +/- 3.3 degrees) than dogs without CCL rupture (means, 23.6 +/- 3.4 degrees and 4.1 +/- 2.2 degrees, respectively). Dogs with proximal shaft deformity represented a distinct group, which could not be identified using the magnitude of the TPS alone. Characterizing more precisely the shape of the proximal portion of the tibia in dogs contributes to our understanding of the pathogenesis of steep TPS and may facilitate the optimization of the surgical management of dogs with CCL rupture.     

ULTRASONOGRAPHIC ANATOMY OF THE NORMAL CANINE STIFLE

Ultrasonographic examination of the normal canine stifle joint was performed to characterize its normal anatomy. Stifles of four normal adult dogs were imaged in sagittal and transverse planes and each anatomic structure visualized was recorded. Normal anatomic structures consistently seen included the patellar tendon, medial and lateral menisci, the cranial cruciate ligament and femoral condyle cartilage. The caudal cruciate ligament was visualized in two dogs. Collateral ligaments and meniscal ligaments were not visualized. The dogs were then euthanized and each stifle was isolated. Following removal of superficial muscles and skin, each stifle was imaged in a water bath to definitively identify the structures that had previously been visualized on the live dogs. The ultrasonographic appearance of the isolated stifle specimens was similar to that found in live dogs. The results of this study indicate that ultrasound can be used to image the normal anatomy of the canine stifle. The echogenicity of the patellar ligament, cruciate ligaments, menisci and articular cartilage was similar to that previously reported in equine stifles and human knees.     

LOW-FIELD MRI AND ARTHROSCOPY OF MENISCAL LESIONS IN TEN DOGS WITH EXPERIMENTALLY INDUCED CRANIAL CRUCIATE LIGAMENT INSUFFICIENCY

Little is known about the magnetic resonance imaging (MRI) appearance of canine meniscal lesions. The aim of this study is to describe the MR appearance of meniscal lesions in dogs with experimentally induced cranial cruciate ligament (CCL) deficiency. The pilot study revealed dogs weighing approximately 10 kg to be too small for meniscal evaluation on low-field MRI. In the main study, dogs weighing approximately 35 kg were used. The left CCL was transected and low-field MRI was performed regularly until 13 months post-surgery. Normal menisci were defined as grade 0. Intrameniscal lesions not reaching any surface corresponded to grade 1 if focal and to grade 2 if linear or diffuse. Grade 3 lesions consisted in linear tears penetrating a meniscal surface. Grade 4 lesions included complex signal changes or meniscal distortion. Between 2 and 13 months post-surgery, all dogs developed grade 4 lesions in the medial meniscus. Most of them corresponded to longitudinal or bucket handle tears on arthroscopy and necropsy. Two dogs showed grade 3 lesions reaching the tibial surface of the lateral meniscus on MRI but not in arthroscopy. Such tears are difficult to evaluate arthroscopically; MRI provides more accurate information about the tibial meniscal surface. Grades 1 and 2 lesions could not be differentiated from presumably normal menisci with our imaging technique. An MRI grading system better adapted to canine lesions has yet to be developed. MRI is a helpful tool for the diagnosis of complete tears in the canine meniscus, especially in larger dogs.     

Accuracy of 3 Tesla magnetic resonance imaging using detection of fiber loss and a visual analog scale for diagnosing partial and complete cranial cruciate ligament ruptures in dogs

Canine cranial cruciate ligament rupture is often bilateral and asymmetrical, ranging from partial to complete rupture. The purpose of our diagnostic accuracy study was to assess the accuracy of 3 Tesla magnetic resonance imaging (MRI) detection of fiber loss and use of a visual analog scale in the diagnosis of complete versus partial cranial cruciate ligament rupture in 28 clinical dogs with unilateral complete rupture and contralateral partial rupture. Three Tesla MRI was performed on 56 stifles using sagittal sequences (T2‐weighted fast spin echo with fat saturation, proton density fast spin echo, and T2‐weighted 3D fast spin echo CUBE). Two MRI observers assessed the cranial cruciate ligament for fiber loss and completed a visual analog scale. The MRI data were compared to arthroscopy and clinical status. Accuracy classifying partial or complete rupture was assessed using receiver operating characteristic analysis. Compared to arthroscopy, for complete cranial cruciate ligament rupture, sensitivity, specificity, and accuracy of MRI detection of fiber loss were 0.78, 0.50–0.60, and 0.68–0.71, respectively, and, for partial tears, specificity was 1.00. An MRI visual analog scale score ≥79 was indicative of complete cranial cruciate ligament rupture (sensitivity 0.72–0.94 and specificity 0.71–0.84). Using a visual analog scale cut‐point ≥79, observers achieved good accuracy discriminating clinical status of partial or complete cranial cruciate ligament rupture (area under the curve 0.87–0.93). MRI evaluation for fiber loss and use of a visual analog scale are specific in stifles with clinically stable partial cranial cruciate ligament rupture. In stifles with clinically unstable complete cranial cruciate ligament rupture, both MRI tests are sensitive though not specific compared to arthroscopy. As a diagnostic imaging method, MRI may help guide treatment in patients with cranial cruciate ligament damage, particularly for stable partial 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.     

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.     

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.     

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.     

SONOGRAPHIC EVALUATION OF THE CRANIAL MEDIASTINUM IN SMALL ANIMALS

Clinical records, radiographs, and sonograms of 17 animals presented for possible cranial mediastinal disease were reviewed. Radiographs were evaluated for accuracy in detection of mediastinal masses. Sonography of the mediastinum was performed using a parasternal approach with the animals in sternal or lateral recumbency. The mediastinum was evaluated for the presence of a mass or other disease. Masses were characterized by echogenicity, size, number, and margination. Mediastinal vessels were studied to determine if there was vascular invasion or compression. A comparison of radiographic and sonographic assessment in cranial mediastinal disease indicates sonography adds valuable information in the diagnosis of mediastinal disease. Results of ultrasound-guided, fine-needle aspirate were documented and found to be advantageous in establishing a diagnosis in mediastinal masses.     

RADIOGRAPHIC AND COMPUTED TOMOGRAPHIC EVALUATION OF THE CANINE INTERCONDYLAR FOSSA IN NORMAL STIFLES AND AFTER NOTCHPLASTY IN STABLE AND UNSTABLE STIFLES

The role of the intercondylar fossa in cranial cruciate ligament injury has gained notable attention in humans and it's role is now being questioned in animals. Controversy exists regarding the accuracy of radiographs and computed tomography (CT) in evaluating the intercondylar fossa. This study compared radiographic and CT evaluation with gross evaluation of the intercondylar fossa. Six greyhounds were evaluated before notchplasty, immediately after notchplasty and 6 months after notchplasty in stable and unstable stifles. A fossa width index was used for comparison because it negates the effects of patient size and radiographic magnification. The fossa width index is calculated by dividing the width of the intercondylar fossa by the total condylar width.
The fossa width indices of dogs determined from radiographs and CT were not significantly different before notchplasty except for the cranial fossa width indices which were more inconsistent and tended to underestimate the size when compared to gross measurements. At six months, both stable and unstable stifles had refilling of the notchplasty, but the unstable stifles had significantly greater refilling resulting in no significant enlargement in intercondylar fossa size as compared to the prenotchplasty size. Osteophytes that occurred within the intercondylar fossa were less radiopaque and more easily visualized by computed tomography. Computed tomography provided several advantages, including clearer visualization of the intercondylar fossa, avoiding superimposition of the intercondylar fossa by caudal thigh muscles or tuber ischii and the ability to analyze the cranial and caudal components of the intercondylar fossa separately.     

ANATOMICAL STUDY OF CRANIAL NERVE EMERGENCE AND SKULL FORAMINA IN THE DOG USING MAGNETIC RESONANCE IMAGING AND COMPUTED TOMOGRAPHY

Twenty-two magnetic resonance imaging (MRI) brain studies of different breeds of dogs were reviewed to assess the anatomy of cranial nerve (CN) origins and associated skull foramina. These included five anatomic studies of normal brains using 2-mm-thick slices and 17 studies using conventional clinical protocols with 3- or 4-mm slices on both normal and abnormal brains. Images were obtained in transverse, sagittal, and dorsal planes to allow a thorough comparison between studies. CNs II, III, V (and its divisions), and VIII were observed consistently on conventional studies. On the thin-slice studies, the origins and proximal portions of CNN IV, VII, and the group of IX, X, and XI could be seen. The origins of CNN VI and XII were not observed with certainty. In parallel, a computed tomography study of an isolated skull was performed with a thin copper wire within each of the skull foramina to determine precisely each CN exit and to facilitate recognition of the course of CNs when exiting the skull on MRI images.