The size and shape of the foramen magnum were studied in skulls from 75 adult and 5 juvenile Pekingese dogs. After maceration of the skulls, the height, width, and area of each foramen magnum were measured, and various skull indices were determined. The shape of the foramen varied from ovoid to rectangular and had a dorsal notch in aU but 2 skulls. Prolapse of cerebellum or brain stem through the enlarged opening was prevented by a fibrous membrane covering he dorsal notch. Mean +/- SD area of the foramen was 138.1 +/- 26.1 mm(2); its mean total height was 15.0 +/- 2.9 mm, and its mean maximal width was 13.3 +/- 1.1 mm. Statistically, variability in the area of the foramen was mainly correlated with total height of the foramen, including the dorsal notch. Total height of the foramen was not correlated with age or gender. The degree of dysplasia, notch index, and occipital index of each foramen magnum were determined. To allow a more accurate evaluation of the morphology of the foramen, the foramen magnum index, defined as the ratio between the maximal width and the total height of the foramen, was also computed. Mean +/- SD foramen magnum index was 91.8 +/- 17.1 in the adult Pekingese dogs. Foramen magnum index was not significantly correlated with age, but was significantly larger in male than in female dogs. The large variability in the shape and size of the foramen magnum and the absence of any neurologic problems in dogs of this study indicate that the dorsal notch of the foramen magnum in brachycephalic dogs is a normal morphologic variation, rather than a pathologic condition.

Intervertebral disk space widths were measured on lateral radiographs of 73 anesthetized dogs. Weight was found to have a significant (P less than 0.01) effect on disk space width. Using weight-adjusted disk space width measurements for all subsequent studies, older (7- to 16-year-old) dogs and males had consistently, but not significantly, wider, disk spaces than did alternative groups. Cervical and lumbar intervertebral disk spaces tended to be wider than those in the caudal thoracic region. The widest cervical intervertebral disk spaces were C4-5 and C5-6 and the narrowest was C2-3. In the lumbar region, L2-3 was the widest disk space and L4-5 was the narrowest. Dachshunds generally had greater mean intervertebral disk space width than did other breeds of dogs. Cervical (n = 6 dogs) and thoracolumbar (n = 6 dogs) disk fenestration resulted in narrow intervertebral disk spaces, regardless of breed. When a ventral approach was used in thoracolumbar fenestration, the mean intervertebral disk space was narrower than that resulting from use of a dorsolateral approach. Spondylosis was found radiographically 1 to 4 years after intervertebral disk fenestration in 3 of 6 dogs that had cervical fenestrations and in 5 of 6 dogs that underwent thoracolumbar fenestration.

The size and shape of the foramen magnum were studied in skulls from 75 adult and 5 juvenile Pekingese dogs. After maceration of the skulls, the height, width, and area of each foramen magnum were measured, and various skull indices were determined. The shape of the foramen varied from ovoid to rectangular and had a dorsal notch in aU but 2 skulls. Prolapse of cerebellum or brain stem through the enlarged opening was prevented by a fibrous membrane covering he dorsal notch. Mean +/- SD area of the foramen was 138.1 +/- 26.1 mm(2); its mean total height was 15.0 +/- 2.9 mm, and its mean maximal width was 13.3 +/- 1.1 mm. Statistically, variability in the area of the foramen was mainly correlated with total height of the foramen, including the dorsal notch. Total height of the foramen was not correlated with age or gender. The degree of dysplasia, notch index, and occipital index of each foramen magnum were determined. To allow a more accurate evaluation of the morphology of the foramen, the foramen magnum index, defined as the ratio between the maximal width and the total height of the foramen, was also computed. Mean +/- SD foramen magnum index was 91.8 +/- 17.1 in the adult Pekingese dogs. Foramen magnum index was not significantly correlated with age, but was significantly larger in male than in female dogs. The large variability in the shape and size of the foramen magnum and the absence of any neurologic problems in dogs of this study indicate that the dorsal notch of the foramen magnum in brachycephalic dogs is a normal morphologic variation, rather than a pathologic condition.

As more sophisticated research is performed to refine fracture fixation techniques for horses, it is important that normal values for the geometric properties of the bones of the appendicular skeleton be determined and that suitable controls be available. We evaluated the geometric properties of total bone width, cortical bone width, and medullary canal/trabecular bone width measured from 2 radiographic projections of equine long bones (humerus, radius, third metacarpal bone, femur, tibia, and third metatarsal bone) obtained from a general population of horses. Measurements were performed on slices separated by intervals equal to 5% of the bone's length. Slices were then grouped into 5 regions: proximal epiphysis, proximal part of the metaphysis, diaphysis, distal part of the metaphysis, and distal epiphysis. Results validated use of the contralateral bone as a control for assessing experimental models or clinical cases. Of 858 homotypic slice comparisons between left and right bones, significant (P less than or equal to 0.05) differences were detected in 31 (3.6%) of the comparisons. Of 168 homotypic region comparisons, significant differences were observed in 3 (1.8%) of the comparisons. The greatest variation between left and right bones was observed in metaphyseal regions, areas with bony protuberances, and regions with prominent bone superimposition. At a power of 0.8 for the statistical tests performed in this study, the mean homotypic variation of bones in each region is < 5.8% for the proximal epiphysis, 11.3% for the proximal part of the metaphysis, 6.8% for the diaphysis, 12.2% for the distal part of the metaphysis, and 5.2% for the distal epiphysis.

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.

Epiglottic augmentation was evaluated in 7 horses, using 7 ml of polytetrafluoroethylene (polytef) paste injected submucosally on the ventral surface of the epiglottis. In 6 horses, an Arnold-Bruning intracordal injection syringe, specifically designed to inject polytef into paralyzed vocal folds in human beings, was used. At necropsy 60 days after surgery, group mean thickness measurement 20 mm from the epiglottic tip was 40% greater (P < 0.01) and, at the epiglottic attachment of the aryepiglottic fold, was 29% greater (P < 0.01) in the 6 polytef-augmented horses than in clinically normal nonsurgically treated controls. At necropsy, extensive epiglottic thickening was seen. This thickening was exclusively attributable to distention of submucosal areas in the ventral aspect of the epiglottis, with foreign body granulomata surrounded by fibrous connective tissue. In 1 horse, polytef paste was injected by use of a disposable syringe and needle. Excess ventral epiglottic swelling and exposed epiglottic cartilage was seen during subsequent endoscopy. At necropsy 60 days after surgery, the epiglottic contour remained deformed and a large deep mucosal ulcer was observed at the injection site. Histologic examination revealed necrotizing suppurative inflammation that extended into the epiglottic cartilage. Surgery was not technically difficult to perform through a laryngotomy, and all horses tolerated the procedure without apparent discomfort. Endoscopy performed after surgery revealed unremarkable and uniform response to the polytef paste in 4 horses, and in 3 horses, revealed excess swelling and inflammation of the ventral epiglottic tissue that resolved over time. Overdistention of the submucosal space with polytef may have accounted for the undesirable tissue responses that developed, including excess inflammation in the ventral epiglottic tissue in 3 horses, migration of polytef in 4 horses, and ventral mucosal ulceration in 3 horses. Thickening of the ventral epiglottic surface that was readily apparent in all horses at necropsy could not be reliably distinguished endoscopically in conscious horses. Qualitative changes in epiglottic thickness and contour could be distinguished on lateral-view laryngeal radiographs; however, thickness measurements made from radiographs did not correlate accurately with actual thickness measurements made at necropsy.