The compound nerve action potential (CNAP) of the superficial peroneal nerve of dogs was investigated to determine: (1) the influence of the stimulation technique on the configuration of the CNAP, with particular attention to late components; (2) the fiber diameter (FD) distribution; and (3) the relationship between FD distribution and CNAP configuration, by reconstruction of CNAP made on the basis of FD distributions. The CNAP were evoked in 9 dogs under halothane anesthesia by 2 stimulation methods: percutaneous needle electrode stimulation and direct stimulation of the exposed superficial peroneal nerve. Recordings were made with percutaneous needle electrodes. Full nerve cross sections of 7 superficial peroneal nerves were prepared for FD morphometric analysis. Reconstruction of CNAP were made on the basis of the FD distributions. Late components of the CNAP could be evoked with either stimulation method, but only with a stimulus intensity of 3 to 5 times maximal for the main (early) component of the CNAP. The FD histograms of 7 analyzed nerves had bimodal distribution. In 5 nerves, peaks were at 4.2 to 4.5 micrometer and 9.0 to 10.0 micrometer with 60% of the fibers in the small-diameter group. In 2 nerves with lower maximal conduction velocities, peaks were shifted toward smaller values. The CNAP reconstructions made by use of FD data closely resembled actual recordings when a fifth-order polynomial function was applied to the relationship between nerve conduction velocity and FD. Reconstructions made by use of 1 or 2 linear functions did not accurately resemble actual recordings. The results indicate clinical sensory electroneurographic recordings can provide accurate information regarding both large- and small-diameter fibers, if adequate stimulus intensities are used. To understand the recorded potential more completely, further studies are needed to determine the effects of volume conduction on configuration of the CNAP. It should then be possible to estimate FD distributions even more accurately by analyzing CNAP of normal nerves, or of diseased nerves in which the normal relation between FD and conduction velocity is preserved.

A histochemical and morphometric study of fiber types in a variety of skeletal muscles of healthy young adult cats was undertaken to provide normative data not available previously. Using a standardized system of nomenclature, fiber types 1, 2A, 2B, and 2C were identified in most cat muscles on the basis of myosin ATPase staining at pH 4.45. Type-2M fibers were present in temporalis (TEM) and masseter (MAS) muscles. Type-1 fibers predominated in medial head of triceps (MHT) and soleus muscles. Type-2B fibers were dominant in biceps femoris, lateral head of gastrocnemius, cranial tibial, long head of triceps, and superficial digital flexor muscles; type-2A fibers were dominant in buccinator muscle samples; and type-2M fibers were dominant in TEM and MAS muscles. Numbers of type-2C fibers did not exceed 2 to 3% of the myofiber population in any muscle. In CT and LHT muscles, a gradient of fiber type distribution was observed, with significant (P < 0.05) increase in numbers of type-1 and type-2A fibers in deeper regions of the muscles. The distribution of fiber types was compartmentalized in MHT and MAS specimens. Diameter of type-2B fibers was significantly (P < 0.05) larger than that of type-1 and type-2A fibers in biceps femoris, lateral head of gastrocnemius, cranial tibial, long head of triceps, and superficial MHT muscles. Diameter of type-2M fibers was significantly (P < 0.05) larger than that of type-1 fibers in TEM and MAS muscles. The soleus type-1 muscle fibers were the largest fibers encountered in any muscle. In MHT muscle, fiber diameter of type-1 and type-2B fibers varied significantly (P < 0.05) in oxidative and glycolytic compartments. Variability coefficients were less than 200 in all muscles. In every muscle specimen, the number of fibers with internal nuclei was less than or equal to 2%.

Magnification of cervical radiographs prevents accurate interpretation of vertebral canal absolute minimum sagittal diameter (MSD) values and application of the established MSD values for diagnosis of cervical stenotic myelopathy (CSM). Variability in MSD determination in human beings, owing to radiographic magnification, is minimized by assessing a ratio of the vertebral canal diameter to the sagittal width of the vertebral body. This relative measurement technique improves the accuracy of diagnosis of cervical spinal stenosis in human beings. The MSD of the vertebral canal was determined in 50 horses with CSM and 50 control horses, using a radiopaque marker method for correction of magnification. In addition, a ratio of the absolute MSD to the sagittal width of the vertebral body and a ratio of the absolute MSD to the length of the vertebral body were determined in 100 CSM-affected and 100 control horses. Response operating characteristic curve analysis of each method determined that the sagittal ratio method of canal diameter assessment provided the most accurate interpretation of cervical radiographs for diagnosis of CSM, with sensitivity and specificity of larger than or equal to 89% at each vertebral site. The accuracy of the ratio method, without consideration of bony malformation, supports the importance, and perhaps prerequisite, of generalized vertebral canal stenosis in the pathogenesis of CSM. Subjective evaluation of bony malformations from cervical radiographs of 100 CSM-affected horses and 100 control horses indicated that CSM-affected horses have more severe bony malformation than do control horses. However, moderate to marked degenerative joint disease of the articular processes was frequently observed in control horses. Subjective evaluation of bony malformation does not distinguish between CSM-affected and unaffected horses.

The umbilical stalk, vein, and arteries, urachal region, and urinary bladder of 9 healthy Holstein calves were scanned ultrasonographically at weekly intervals from 1 day to 3 weeks of age. Four additional calves of representative ages, 1 day, 1 week, 2 weeks. and 3 weeks were euthanatized after ultrasonographic evaluation of the umbilical structures. Umbilical structures from these 4 calves were dissected, photographed, and examined histologically to ensure normalcy. These gross specimens were correlated with the ultrasonographic images and compared with serial ultrasonograms of 9 calves. The ultrasonographic scanning technique and the appearance of normal umbilical stalk, arteries, and vein, and urachus in calves were different from those described for foals. The umbilical vein of calves was scanned from the umbilical stalk to the liver along the right abdominal wall. Two veins, which merged within the body wall, were identified within the stalk. Umbilical arteries were not found within the umbilical stalk; they ended abruptly near the apex of the urinary bladder. A urachal remnant was not identified in any of the calves. A range of normal values for measurement of the umbilical stalk, umbilical arteries, and umbilical vein at 3 sites was determined. The described ultrasonographic appearance and measurements of the normal Holstein calf umbilicus may be used as a reference for evaluation of calves with internal umbilical abnormalities.

Fetal activity and mobility and changes in diameter of the allantoic fluid compartment in the uterine horns were studied in mares between days 69 and 81 of pregnancy by use of transrectal ultrasonography (n = 12) and transcervical videoendoscopy (n = 8). The insertion tube of the videoendoscope was positioned within the allantoic sac to permit viewing of the fetus and entrance to each uterine horn. Each uterine horn was divided ultrasonographically into 3 segments of equal length, and the horns were designated on the basis of side of umbilical attachment (cord vs noncord horns). The diameter of the allantoic fluid compartment in the cornual segments increased (P < 0.05) over the cranial (18.6 +/- 1.9 mm), middle (35.6 +/- 2.9 mm), and caudal (51.7 +/- 4.4 mm) segments, but differences between cord and noncord horns were not evident. Dynamic changes in diameter of the allantoic fluid compartment in cornual segments (ultrasonography) and at the entrance to each uterine horn (videoendoscopy) were detected (no significant difference between methods). During continuous videoendoscopic viewing (17 to 60 min/mare), extreme changes in allantoic fluid compartment diameter (76 to 100% of maximum to 0 to 25% of maximum or vice-versa) occurred an equivalent of 2.6 times/h/horn entrance; changes had an average duration of 3.4 minutes. A change from 100% (maximal diameter) to 0% (no visible lumen) or vice-versa occurred an equivalent of 1.3 times/h/horn entrance. Sometimes the uterine wall was so closely constricted around the fetal-amniotic unit that no intervening allantoic fluid was ultrasonographically detectable, whereas at other times, the uterus in the same location was widely dilated. Results indicated that extensive allantoic fluid shifts were associated with frequent diameter changes in various segments of the uterus. On the basis of 30-second activity trials every 10 minutes, the fetus was active 27% and was quiet 73% of the time (combined ultrasonographic and videoendoscopic data). Activity sometimes involved only movements of extremities, head, or mouth, whereas at other times, a sudden burst of intense whole-body activity was observed. The vigorous whole-body movements buoyed the fetus into the allantoic fluid, and movements of the extremities often caused the fetus to push away from the allantoic wall, resulting in marked changes in location, recumbency, and presentation (direction faced by fetus). Several instances were observed during videoendoscopic examination, in which the fetal-amniotic unit appeared to be forced through a constricted horn entrance into the allantoic fluid compartment at the dilated uterine body. On the basis of continuous videoendoscopic viewing, the fetus changed locations among the major portions of the uterus (body and each horn), on average, 5.0 times/h. Changes in recumbency and presentation occurred, on average, 10.5 and 5.0 times/h, respectively. The frequency of type of recumbency decreased (P < 0.005) as follows: lateral, 23 of 39 (59%); dorsal, 15 of 39 (38%); and ventral, 1 of 39 (3%). Frequency of cranial, caudal, and transverse presentation was not different between cord and noncord horn. Caudal presentation was more common (P < 0.005) when the fetus was in a uterine horn (47/70, 67%) than when it was in the uterine body (15/50, 30%; combined ultrasonographic and videoendoscopic data). Transverse presentation was more common (P < 0.005) when the fetus was in the uterine body (14/50, 28%) than when it was in a horn (4/70, 6%). Results indicated that the early stage equine fetus (days 69 to 81) is extremely mobile within the allantoic fluid, with frequent (several times per hour) changes in location, recumbency, and presentation.

The carotid artery of clinically normal goats was examined, using duplex ultrasonography and arteriography. The diameter of the carotid artery was measured by use of two-dimensional ultrasonography and Doppler ultrasonography, respectively, before and after xylazine administration. The diameter of the artery was also measured by use of an arteriography technique in halothane-anesthetized goats. There was no significant difference between the mean diameter of the carotid artery measured by ultrasonography in conscious nonsedated goats and that determined by arteriography in goats under halothane anesthesia. On the other hand, ultrasonography of xylazine-sedated goats revealed an increase of carotid artery diameter of 20 to 30%. There was no change in the velocity of blood flow after xylazine administration.

Objective-To compare variables for screw insertion, pushout strength, and failure modes for a headless tapered compression screw inserted in standard and oversize holes in a simulated lateral condylar fracture model. Sample Population-6 pairs of third metacarpal bones from horse cadavers. Procedure-Simulated lateral condylar fractures were created, reduced, and stabilized with a headless tapered compression screw by use of a standard or oversize hole. Torque, work, and time for drilling, tapping, and screw insertion were measured during site preparation and screw implantation. Axial load and displacement were measured during screw pushout. Effects of drill hole size on variables for screw insertion and screw pushout were assessed by use of Wilcoxon tests. Results-Drill time was 59% greater for oversize holes than for standard holes. Variables for tapping (mean maximum torque, total work, positive work, and time) were 42%, 70%, 73%, and 58% less, respectively, for oversize holes, compared with standard holes. Variables for screw pushout testing (mean yield load, failure load, failure displacement, and failure energy) were 40%, 40%, 47%, and 71% less, respectively, for oversize holes, compared with standard holes. Screws could not be completely inserted in 1 standard and 2 oversize holes. Conclusions and Clinical Relevance-Enlarging the diameter of the drill hole facilitated tapping but decreased overall holding strength of screws. Therefore, holes with a standard diameter are recommended for implantation of variable pitch screws whenever possible. During implantation, care should be taken to ensure that screw threads follow tapped bone threads.

Dogs have been used extensively as an experimental model for studying musculoskeletal disorders. Many of these studies incorporated sequential radiography to quantitate a particular treatment's effect, using the contralateral bone as the control condition. The contralateral bone can be used as a control only if there is bilateral symmetry between right and left limbs. We performed radiography (craniocaudal and lateromedial views) on 10 pairs of humeri, radii, femora, and tibiae from dogs, using an alignment jig, to radiographically determine homotypic geometric variations of long bones. The bones were divided into 5 regions: proximal epiphysis, proximal metaphysis, diaphysis, distal metaphysis, and distal epiphysis. The total bone diameter, medullary diameter, and cortical width (total of medial + lateral cortex or total of cranial + caudal cortex) were measured at specified slices throughout each of these regions. Fourteen of 540 homotypic comparisons revealed significant differences between right and left bones at either a slice or region. Although there were only 14 significant differences between right and left bones at any region or slice, measurements were more precise with lower coefficients of variation in the diaphyseal and epiphyseal regions. Homotypic differences in diaphyseal and epiphyseal regions were < 5.3 and 7.5%, respectively power = 0.8). In metaphyseal regions, however, homotypic differences were larger; these differences could have been as large as 11.5% for total bone diameter, 15.6% for medullary diameter, and 80.0% for cortical width without achieving significant differences between populations (power = 0.8). This study validated the concept of using the contralateral limb as the control condition in orthopedic studies using dogs, particularly when evaluating the geometric properties of long bones radiographically.

A morphologic and morphometric study was carried out on the facial nerve: to determine normal histologic data in myelinated fibers of clinically normal young adult dogs; to establish reference values for mean fiber diameter, and to delineate the relative diameter frequency distribution curve. Few degenerative changes were observed in single teased-nerve fibers and semithin cross-sectional nerve preparations. Statistical difference was not observed between left and right facial nerves. The distribution of fiber diameters in the facial nerve was unimodal. Mean (+/- SD) fiber diameter of the facial nerve was 3.92 +/- 1.18 micromole. Approximately 89% of fibers in the facial nerve had diameter between 3 and 6 micromole. Fiber diameter ranged from 2 to 12 micromole; however, < 1% of fibers had diameter > 8 micromole.

Dogs were treated with the cyclo-oxygenase inhibitors flunixin meglumine IV or flurbiprofen topically. Acute inflammation was induced in the eyes by disruption of the anterior lens capsule, using a neodymium:yttrium aluminum garnet laser. Pupil diameter and intraocular pressure were measured before and after inducing ocular inflammation. Both drugs maintained mydriasis and increased intraocular pressure in the inflamed eyes, compared with untreated controls.