A RADIOGRAPHIC TECHNIQUE FOR PELVIMETRY OF UNANAESTHESTISED EWES AND A COMPARISON OF THREE METHODS OF ESTIMATING THE AREA OF THE PELVIC INLET

SUMMARY A radiographic procedure is described which enables reliable estimation of the area of the pelvic inlet of up to 150 ewes per seven-hour day by combining use of a specialized radiographic table, immobilisation of the subject with a blindfold and 2 restraining belts, and a mobile condenser-discharge x-ray generator powered by a domestic electrical supply or a portable generator. Six pelvic dimensions, the distances between the medial ischiatic tuberosities, the lateral ischiatic tuberosities, the length of the pubic symphysis, the acetabular, transverse and conjugate diameters and the area of the pelvic inlet computed as the product of the transverse and conjugate diameters (pelvic axes), were estimated by three methods which allowed for magnification resulting from the dimensions of interest lying at varying heights above the film. The estimates were compared by linear regression analysis with their respective values obtained directly from the pelves dissected after slaughter, method A. Method B was isometric, using a perspex vaginal isometer with radiopaque calibrations. Methods C and D applied the theorem of similar triangles. Method C assumed that the dimensions of interest lay in a horizontal plane halfway through the dorso-ventral or lateral thickness of the subject when thickness was measured on a level with the femoral greater trochanters. Method D assumed that the dimensions of interest lay in the same horizontal plane as the height of the subject's anus above the table top when measured in sternal or lateral recumbency. The test subjects were groups of aged, non-pregnant Dorset Horn or Merino ewes. Method B estimated the pelvic axes unreliably in both breeds. Method D, although almost as reliable as method C in Dorset Horn ewes, was not used in merinos because it was cumbersome. Method C was preferred because the estimates were highly correlated with the exact values for both breeds and it was the easiest to apply since measuring body thickness was essential for calculating exposures. Using method C, R values in Dorset Horns for the transverse and conjugate diameters, and the area of the pelvic inlet, were 0.96, 0.78 and 0.81 respectively. For Merinos the corresponding values were 0.88, 0.80 and 0.84 respectively. As method C over-estimated the area of the pelvic inlet, a prediction equation was derived to minimise this tendency, resulting in revised estimates, accurate within 2.7% and 3.9% respectively, of the values obtained at the autopsy of the merino and Dorset Horn test subjects. All methods were unsatisfactory for estimating dimensions other than the transverse and conjugate diameters, and the area of the pelvic inlet. The procedure recommended has been used in several breeding flocks to determine the role of mature maternal pelvic size in feto-pelvic disproportion, birth injury to the fetal central nervous system and repeated maternal rearing failure.     

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 EXAMINATION OF THE NORMAL CANINE NEONATAL BRAIN

One hundred eighty B-mode ultrasound examinations of the brain were performed in 34 neonatal dogs from six litters using the bregmatic fontanelle to provide an acoustic window. One image from a hydrocephalic neonate of another litter was included for comparison. Histologic verification of anatomic structures was done in 19 of the 34 subjects. Imaging of 15 additional animals indicated the bregmatic fontanelle could serve as a sonographic window during the first three to four weeks after birth. Measured values of the largest lateral ventricle with a normal histologic evaluation were: lateral ventricular height = 0.15 cm, ventricle-hemisphere ratio = 0.09, and ventricle-mantle ratio = 0.15. A Beagle neonate without histologic analysis had a lateral ventricular height of 0.31 cm, a ventricle-hemisphere ratio of 0.19 and a ventricle-mantle ratio of 0.19.     

Measurement of femoral angles in four dog breeds

Objective— To develop a standard method of measurement for femoral angles and report values for normal Labrador Retrievers, Golden Retrievers, German Shepherds, and Rottweilers.
Study Design— Retrospective evaluation of canine pelvis and femoral radiographs.
Sample Population— Radiographs of Labrador Retrievers, Golden Retrievers, German Shepherds, and Rottweilers (n=100 for each breed).
Methods— Anatomic lateral distal and proximal femoral angle, mechanical lateral distal and proximal femoral angle, and femoral angle of inclination were measured from radiographs.
Results— For the 4 breeds (Labrador Retrievers, Golden Retrievers, German Shepherds, and Rottweilers, respectively) anatomic lateral distal femoral angles were 97°, 97°, 94°, and 98°; mechanical lateral distal femoral angles were 100°, 100°, 97°, and 100°; anatomic lateral proximal femoral angles were 103°, 98°, 101°, and 96°; mechanical lateral proximal femoral angles were 100°, 95°, 97°, and 93°; and inclination angles were 134°, 134°, 132°, and 137°. Labrador Retrievers, Golden Retrievers, and Rottweilers had significantly higher values for both anatomic and mechanical lateral distal femoral angle than German Shepherds. Anatomic and mechanical lateral proximal angles were greatest for Labrador Retrievers and lowest for Rottweilers.
Conclusion— Anatomic and mechanical femoral joint angles vary between breeds of dogs.
Clinical Relevance— Values for femoral joint angles may be clinically useful for angular limb deformity diagnosis, treatment, and assessment.     

COMPARISON OF COMPUTED TOMOGRAPHY, TANGENTIAL VIEW RADIOGRAPHY, AND CONVENTIONAL RADIOGRAPHY IN EVALUATION OF CANINE PELVIC TRAUMA

Thirteen dogs with fractures requiring surgical repair were evaluated by standard two-view (i.e., lateral and ventrodorsal) radiography, tangential view (ventro 20 degrees cranial-dorsocaudal [inlet] and ventro 20 degrees caudal-dorsocranial [outlet]) radiography, and computed tomography (CT). Radiographic and CT examinations were reviewed independently by the three authors, and specific anatomic sites were graded for the presence or possibility of lesions. The results of radiographic interpretations were compared to CT scan interpretations. Eighty-one percent of skeletal lesions detected by CT scans were diagnosed definitively radiographically. Differences between the interpretation of CT and radiographic examinations included abnormalities associated with soft-tissue structures (P < 0.0001), the sacroiliac joints (P = 0.02), and the acetabula (P = 0.04). Interpretation of the lateral/ventrodorsal and inlet/outlet radiographic series were not statistically different, although inlet views may be complimentary to the standard radiographic examination. Its use deserves further study. Reader variation was less on evaluation of CT examinations than radiographic examinations. CT multiplaner reformations and three-dimensional reconstructions were useful for surgical planning in seven dogs. CT scanning is superior to survey radiography in assessing skeletal and soft-tissue injuries in dogs with pelvic trauma, although all clinically significant surgical lesions were described accurately radiographically. Based on this small series, the routine CT examination of dogs with pelvic trauma may not be justifiable for diagnosis but may be advantageous for surgical planning, especially if acetabular fractures are suspected on radiographs.     

ASSESSMENT OF THREE RADIOGRAPHIC PROJECTIONS FOR DETECTION OF FLUID IN THE RABBIT TYMPANIC BULLA

Otitis media in the rabbit commonly results in fluid accumulation in the tympanic bulla. Radiographic detection of fluid in the tympanic bulla is only moderately sensitive in the dog and cat. The purpose of this study was to investigate the accuracy of radiographic detection of fluid in the rabbit tympanic bulla for three different radiographic projections. Forty rabbit cadavers were used. Half of the tympanic bullae were randomly allocated to be filled with soft tissue material. Following this procedure, each specimen was radiographed in three projections: dorsoventral (DV), rostro 40° ventral-caudodorsal (R40°V-CdDO), and left and right latero 40° ventral-laterodorsal (Lat40°V-LatDO). After imaging, each specimen was frozen and sectioned to determine the content of the tympanic bullae. Images were interpreted and scored independently by two board-certified radiologists. There was no significant difference in sensitivity or specificity between the three projections when compared with the gross findings following sectioning, but observer confidence was highest for the DV projection. Accuracy of radiographic fluid detection was similar to that reported in the dog and cat. The DV and R40°V-CdDO allow comparison of both tympanic bullae on a single radiograph, but the DV was subjectively easier to position, while the Lat40°V-LatDO requires two radiographs for comparison.     

ULTRASONOGRAPHIC TECHNIQUE AND NORMAL ANATOMIC FEATURES OF THE SACROILIAC REGION IN HORSES

The purpose of this study was to establish the normal percutaneous ultrasonographic appearance of anatomic structures within the equine sacroiliac region. Percutaneous ultrasonography was performed in a cranial-to-caudal direction in 10 normal adult live horses. The following structures were examined in detail: supraspinous ligament, lumbar and sacral spinous processes, thoracolumbar fascia and its caudal extension, tubera sacralia, ilial wings, dorsal and lateral portions of the dorsal sacroiliac ligaments, lateral part of the sacrum, and the lateral sacral crest. After ultrasonography, all animals were euthanized and detailed dissection of the lumbosacropelvic region was performed in six horses. Four lumbosacropelvic specimens were frozen and sectioned transversely for evaluation of cross-sectional anatomy. Gross anatomic findings were correlated with ante-mortem ultrasonographic images. On percutaneous ultrasonography, all horses had tubera sacralia with a mild-to-moderate roughened surface with occasional irregular hyperechoic mineralizations located within the apophyseal cartilage of younger horses. At the level of the tuber sacrale the caudal extension of the thoracolumbar fascia joined the dorsal portion of the dorsal sacroiliac ligament and assumed two different configurations relative to the dorsal portion of the dorsal sacroiliac ligament, with the predominant configuration of the thoracolumbar fascia located medial to the dorsal portion of the dorsal sacroiliac ligament. The less frequently encountered configuration had the thoracolumbar fascia positioned dorsal to the dorsal portion of the dorsal sacroiliac ligament. Caudal to the tuber sacrale the dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia consolidated to form a single, fused structure with a common insertion on the sacral spinous processes. A large variability in linear fiber pattern, echogenicity (small focal hypoechoic areas), ligament height, and cross-sectional measurements was identified in the fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia of normal horses. Diagnosing mild-to-moderate desmitis of the fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia based solely on ultrasonography may therefore be difficult. To correlate ultrasonography with histology, samples of a fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia with bilateral hypoechoic lesions were submitted for histology and revealed diffuse mild-to-moderate loss of fiber density, multifocal fibrocyte degeneration, and cartilagenous metaplasia with multifocal, mild myofiber mineralization, which was compatible with age-related changes. As controls, sections of ultrasonographically normal fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia from three horses demonstrated similar but milder histologic findings, which were considered normal.     

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.     

MAGNETIC RESONANCE IMAGING OF THE LATERAL VENTRICLES IN BEAGLE-TYPE DOGS

Magnetic resonance (MR) imaging was performed on 21 presumed normal Beagle-type dogs. The size and symmetry of their lateral ventricles were evaluated and dogs were categorized on the basis of the percentage of their ventricular height (Vh) to brain height (Bh) and the ratio of the largest to the smallest ventricular area (rVA). Eleven dogs had lateral ventricles classified as normal sized (0–14 %Vh/Bh) while 10 of 21 dogs had moderate enlargement (1525% Vh/Bh) of one or both lateral ventricles. None of the dogs had severe lateral ventricular enlargement. Degree of asymmetry was also arbitrarily categorized on basis of rVA as normal to minimal (rVA < 1S), mild (1.5 < rVA < 2.0), or severe (2.0 < rVA). Of the dogs having normal-sized lateral ventricles, six of eleven had symmetric, three of eleven had mildly asymmetric and two of eleven had severely asymmetric lateral ventricles. Of the dogs having at least one moderately enlarged lateral ventricles, five of ten had symmetric lateral ventricles, and two of ten had mild asymmetry and three of ten had severe asymmetry. Gender and body weight had no statistical relationship to lateral ventricle symmetry. Clinically insignificant ventricular enlargement and asymmetry was common in this group of Beagle dogs.     

ULTRASONOGRAPHIC ANATOMY OF THE TEMPOROMANDIBULAR JOINT IN HEALTHY PURE-BRED SPANISH HORSES

The objective was to describe the normal ultrasonographic appearance of the soft tissue and bony structures of the temporomandibular joint in Pure-Bred Spanish horses using frozen and plastinated sections performed as anatomical references. The temporomandibular joint of five healthy Pure-Bred Spanish horses and the head specimens from 12 Pure-Bred Spanish cadavers that were subjected to euthanasia for reasons other than temporomandibular joint problems were studied sonographically and anatomically. An 11 MHz linear-array transducer was used to obtain longitudinal ultrasonographic images of the temporomandibular joint from rostral, lateral, and caudal approaches. For anatomic study, a gross dissection was performed on six temporomandibular joints. The other six head specimens were first frozen at -30 degrees C for 48h and then, at -70 degrees C for a week. Three millimeter thick anatomic sections were collected in the same plane as the sonographic planes. These sections were plastinated, photographed, and compared with the corresponding ultrasonographic images. The articular surfaces, the articular cartilage, the disc, the intra-articular fat tissue, the joint capsule, and other structures were clearly visualized sonographically. Structures identified on the ultrasonographic images were in accordance with those identified on the corresponding anatomic sections. We confirmed the appearance of structures of the equine temporomandibular joint that have been described previously but we also identified the caudal fibrous expansion of the disc, the caudal compartment of the dorsal synovial pouch, and the lateral ligament. Our results define a reference that will aid in sonographic evaluation of the equine temporomandibular joint region.     

CORRELATIVE ULTRASOUND ANATOMY OF THE FELINE BRACHIAL PLEXUS AND MAJOR NERVES OF THE THORACIC LIMB

Brachial plexus avulsions commonly occur in cats due to traumatic injuries involving the shoulder. Ultrasound may be an effective method for detecting injured nerves. Additional applications may include characterization of brachial plexus neoplasms and guidance of anesthetic nerve blocks. Aims of this study were to describe ultrasonographic approaches and the normal appearance of this plexus and other major nerves of the thoracic limb in cats. Eight feline cadavers were used to determine anatomic landmarks, obtain cross‐sectional anatomic images of the target nerves, and compare these with ultrasound images. An ultrasonographic study was performed in five fresh feline cadavers to assess the brachial plexus and its major components at the levels of the axilla and proximal, middle and distal (lateral and medial approaches) humeral regions. Five healthy adult cats were recruited for an in vivo ultrasonographic study using the same protocol described for the cadaver ultrasonographic study. The roots of the brachial plexus appeared as a cluster of small, round hypoechoic structures surrounded by a hyperechoic rim in the axillary approach. The radialis, medianus, and ulnaris nerves were individually visualized on proximal and middle humeral approaches. The medianus and ulnaris nerves were easily identified on the medial aspect of the humerus in the distal approach. The superficial branch of radialis nerve was seen on the lateral aspect of the distal humerus approach. The nerves appeared as oval‐to‐round hypoechogenic structures with a hyperechogenic rim. Future studies are needed to compare findings from this study with those in cats with confirmed brachial plexus injuries or other lesions.     

COMPUTED TOMOGRAPHIC ANATOMY OF THE EQUINE TARSUS

The purpose of this study was to provide a detailed computed tomographic (CT) anatomic reference for the equine tarsus. CT examinations of the tarsal regions from four clinically and radiographically normal adult horses, which were euthanized for reasons not related to musculoskeletal disease, were included in the study. Limbs were removed at the level of midtibia, and 3-mm contiguous transverse CT images were obtained, starting at a level proximal to the tuber calcanei and continuing distally into the proximal metatarsus. Soft tissue and bone windows were used to image different anatomic features, including bones, joints, and various soft tissue components of the tarsus. Each transverse slice was compared with bone models and dissected specimens to assist in the accurate identification of specific structures. The results of the study consist of nine CT images of the equine tarsus. Each image incorporates labeled soft tissue and bone-window images, a directional compass indicating cranial (Cr) or dorsal (D) and lateral (L), and a reconstructed scout image indicating the level through which the transverse slice was made.     

THE EFFECT OF OBLIQUITY ON THE RADIOGRAPHIC APPEARANCE OF THE TEMPOROMANDIBULAR JOINT IN DOGS

The temporomandibular joint is formed between the condyloid process of the mandible and the mandibular fossa of the temporal bone. The basic anatomy of this joint was assessed and described in a series of skulls including dolichocephalic, mesaticephalic and brachycephalic breeds. The facial index and rotational angles were measured with the facial index providing a useful method of classifying skull types but the rotational angle being of limited use in assessment of the temporomandibular joint until normal breed values are established. Equipment was designed to allow repeatable positioning of the temporomandibular joint for radiography at a variety of lateral and long axis rotational angles relative to the central x-ray beam. The regions of the joint and anatomic features visualized in each view are demonstrated. 10 degrees rotation was required in either axis to project the joints independently of each other. Lateral rotational angles of 10 to 30 degrees in mesaticephalic and dolichocephalic breeds and 20 to 30 degrees in brachycephalics and long axis rotational views of 10 to 30 degrees depending on the region of interest were considered to be the most useful.     

RADIOGRAPHY OF THE CANINE HEAD

Through the use of a purebred dog skull collection, specific positioning recommendations were established for radiography for the three skull types. It is suggested that the central ray of the beam be maintained at the following mean angles relative to the hard palate for the rostrodorsal-to-caudoventral oblique projection of the foramen magnum: dolicocephalic, 30° mesaticephalic, 20° and brachycephalic, 10°. It is recommended that the head be axially rotated as follows to radiographically separate the roots of the superior canine teeth: dolicocephalic, 48° mesaticephalic, 43° and brachycephalic, 35°. If only the cheek teeth require evaluation, the head should be rotated as follows: dolicocephalic, 37° mesaticephalic, 34° and brachycephalic, 25°. For evaluation of the inferior cheek teeth, it is recommended that the head be rotated as follows: dolicocephalic, 46° mesaticephalic, 44° and brachycephalic, 28°. It is recommended that radiographs of the temporo-mandibular joint be made with the skull axially rotated 10° and longitudinally obliqued as follows: dolicocephalic, 10° mesaticephalic, 14° and brachycephalic, 27°. Suggestions for open-mouth projections for evaluation of the tympanic bullae are that the central ray maintain the following angles relative to the hard palate: dolicocephalic, 4° mesaticephalic, 9° and brachycephalic, 21°. It is recommended that a caudoventral-rostrodorsal oblique projection of the nasal cavity made at 30° to the hard palate replace the open-mouth ventrodorsal in brachycephalic breeds.     

COMPUTED TOMOGRAPHIC ARTHROGRAPHY OF THE INTERCARPAL LIGAMENTS OF THE EQUINE CARPUS

Injuries of the intercarpal ligaments are an important cause of lameness in performance horses. The purpose of this prospective cadaver study was to determine whether computed tomography (CT) arthrography would be a feasible method for visualizing and characterizing intercarpal ligaments in the horse. One cadaver limb from each of eight nonlame horses was collected immediately after euthanasia. For each limb, overlapping 2.0 mm CT images were acquired before and after injection of iodinated contrast medium into the antebrachiocarpal joint, middle carpal joint, and carpal sheath. Spin echo magnetic resonance imaging (MRI) sequences were acquired in three planes using a 1.5 Tesla MRI scanner in three limbs. Following MRI, colored resin was injected into the synovial structures of these three limbs, limbs were frozen, and anatomic sections were obtained in three planes. Findings from CT arthrograms were compared to findings from precontrast CT, MRI, anatomic slices, and arthroscopy. Medial and lateral palmar intercarpal ligaments, radiocarpal and transverse intercarpal ligaments, and palmar carpal ligament were visible in CT arthrograms of all limbs. The proximal and distal entheses of all ligaments were readily identifiable. Findings indicated that CT arthrography is feasible for visualizing intercarpal ligaments and may be a useful adjunct imaging technique for diagnosing lameness due to suspected carpal ligament injury in horses.     

Effects of urinary bladder distention on location of the urinary bladder and urethra of healthy dogs and cats

Evaluation of the anatomic location of the distended and empty urinary bladders and urethras of healthy adult male and female dogs and cats by retrograde urethrocystography revealed substantial variations. In 15 dogs in lateral recumbency with empty bladder lumens, the caudal portion of the urinary bladder was within the pelvic canal in 5 of 7 male and 5 of 8 female dogs. In female dogs examined in ventrodorsal recumbency, only 4 of 8 had the empty urinary bladders in part within the pelvic canal. After luminal distention, 3 of 7 male and 3 of 8 female dogs, while in lateral recumbency, had the urinary bladders in part intrapelvically. However, when female dogs were placed in ventrodorsal recumbency, only 1 of 7 urinary bladders was in part within the pelvis. The urinary bladders of 14 cats were consistently within the abdominal cavity, irrespective of whether the bladder lumen was distended or empty. Urethral flexures occurred in dogs with intrapelvic bladders that were distended or empty. Urethral flexures were not found in cats. The urethras of dogs and cats in lateral recumbency were generally closer to the floor of the pelvis after urinary bladder distention than when the bladder was empty. The urethra of the dogs and cats in ventrodorsal recumbency was to the left or right of or on the midsagittal plane, whether the urinary bladder was empty or distended. A greater degree of lateral displacement was encountered in ventrodorsal recumbency after urinary bladder distention.