Developmental Abnormalities of the Canine Skull

Fox, M. W., The Jackson Laboratory, Bar Harbor, Maine. Developmental Abnormalities of the Canine Skull.

Prognathism of the upper jaw and partial agnathia of the lower jaw and related disorders including dental anomalies, palatitis, and otocephaly are described. Similarly, secondary or concurrent anomalies associated with brachygnathism are discussed where an excess of soft tissue in proportion to the size of the upper jaw and facial (brachyfacial) area may cause a variety of clinical conditions. The higher incidence of neoplasia of the CNS in brachycephalic dogs may be related to reduction in cranial capacity in proportion to brain volume and pressure changes are less easily compensated in the brachygnathic breeds.

     

Osmotic stress in red blood cells from beagles with hemolytic anemia.

Red blood cell populations separated by density centrifugation were compared in a dynamic assay of osmotic stress. Red blood cells from Beagles genotypically normal and nonanemic (nonaffected), Beagles with inherited hemolytic anemia (anemic), and Beagles presumed to be carriers of the anemia trait (trait carriers) were examined for rate and extent of swelling after exposure to the ionophore A23187 in a medium containing calcium and potassium chloride. Comparisons were made between RBC populations separated on the basis of density. Significant differences were observed in the rates of cell swelling in RBC populations separated by density between nonaffected and anemic Beagles. The response of RBC from Beagles presumed to carry the anemia trait was similar to that of RBC from nonaffected dogs. One phenotypic expression of this inherited abnormality of RBC in Beagles was an accelerated rate of RBC swelling under osmotic stress, and this swelling response diminished with increasing RBC density.     

CT and cross-sectional anatomy of the paranasal sinuses in the Holstein cow

The structure of paranasal sinuses in cattle is difficult to understand due to its complexity, age-related changes, and insufficient published data. In this prospective, anatomic study, we described the anatomy of the paranasal sinuses in the Holstein cow using computed tomography (CT) and cross-sectional anatomic slices. Twelve healthy adult Holstein cow heads were used for this study. The heads were scanned using CT, and frozen anatomical sections were taken. The locations, borders, and relationships of the paranasal sinuses were defined on the anatomical sections and CT images. The paranasal sinuses on each side of the head consisted of conchal (dorsal, middle, and ventral), maxillary, lacrimal, palatine, frontal, sphenoid sinuses, and ethmoidal cells. The frontal sinus pneumatized all bones surrounding the cranial cavity, except for the ethmoidal and body of basisphenoid bones. The sphenoid and ventral conchal sinuses were the most asymmetrical, and the middle conchal sinus was the simplest. The ventral conchal sinus was detected in eleven animals, one of which was unilateral. This sinus communicated with the middle nasal meatus (13/21) and ventral nasal meatus (8/21). Findings can be used as background for interpreting CT studies of cattle with clinical signs of sinonasal region diseases. Future cross-sectional radiological and reconstructive anatomical studies and investigation of the postnatal development of related structures in cattle are needed.     

Measurement of transepidermal water loss from clipped and unclipped anatomical sites on the dog

Objectives   To establish a standardised clipping method for the measurement of transepidermal water loss (TEWL) with a VapoMeter® in Beagle dogs and to identify the optimal anatomical site for TEWL measurement.
Procedure   TEWL values obtained from skin sites on five healthy Beagles clipped using two different blade angles (standard vs non-standard) were compared. TEWL values for 48 h were also obtained from seven different anatomical sites that had differing hair density. The hair was clipped in the intensively haired anatomical sites (head, lower and upper back and tail), but not clipped in the sparsely haired sites (ear, inguinal region, footpad).
Results   The TEWL values for the standard and non-standard clipping sites were 6.3 ± 1.31 and 27.2 ± 1.11 g/h/m², respectively. We found the upper back among the clipped sites was the most appropriate site for TEWL measurement over 48 h after clipping, whereas among the unclipped sites the ear was the most appropriate, because the TEWL values from those anatomical sites had the least fluctuation and were less affected by movement.
Conclusion   The clipping method and anatomical site should be standardised in order to minimise the experimental variation in TEWL measurement in dogs.     

Comparative Doppler imaging of the ophthalmic vasculature in normal Beagles and Beagles with inherited primary open-angle glaucoma

The objective of this study was to compare orbital and ocular vasculature velocity, measured by Doppler imaging, in normal Beagles and Beagles with inherited primary open-angle glaucoma. Eight normal Beagles and 13 Beagles with different stages of primary open-angle glaucoma were evaluated twice with a 2–4-week period between measurements. Doppler imaging was performed with the dogs anesthetized, and the Doppler transducer applied directly on the corneal surface. The majority of the orbital vasculature (external ethmoidal artery; internal ophthalmic artery and vein; and external ophthalmic artery and vein) and ocular blood vessels (anterior ciliary artery and veins; long posterior ciliary arteries; short posterior ciliary arteries; primary retinal arteries; and the vortex veins) were identified and Doppler blood velocity parameters were determined. The glaucomatous dogs demonstrated significant differences in the Doppler velocity parameters of several orbital vessels (external ethmoidal, external ophthalmic, and internal ophthalmic arteries), and several ocular vessels (anterior ciliary, short posterior ciliary, and long posterior ciliary arteries). These differences included decreased blood velocities, and increased pulsatility and resistive indexes. The Doppler blood flow velocities of the primary retinal arteries were unchanged between the normal and glaucomatous dogs. In the glaucomatous dogs, the Doppler imaging suggests increased vascular resistance downstream in both the orbital and ocular vasculature. These blood velocity parameter changes may be primary or secondary, and may offer therapeutic opportunities to increase perfusion, prolong the retina and optic nerve head function, and maintain vision in the canine glaucomas.     

Isolation and measurement of carbonic anhydrase isoenzymes in erythrocytes of dogs

OBJECTIVE: To purify canine carbonic anhydrase (CA) isoenzymes CA-I and CA-II and to determine concentrations of CA-I and CA-II in erythrocytes of Beagles and dogs native to Japan. SAMPLE POPULATION: Blood samples from 116 Beagles, including 24 pregnant Beagles, and blood samples from 29 dogs native to Japan. PROCEDURE: Canine CA-I and CA-II were purified by use of column chromatography. Concentrations of CA-I and CA-II in erythrocytes of dogs were determined, using an ELISA. RESULTS: Mean (+/- SD) concentrations of CA-I and CA-II in erythrocytes of Beagles were 3.21+/-0.86 and 1.63+/-0.39 mg/g of Hb, respectively. Mean concentration of CA-I was greater in male Beagles than female Beagles. In contrast, mean concentration of CA-II was greater in female Beagles than male Beagles. Furthermore, concentration of CA-II was greater in pregnant female Beagles than male or nonpregnant female Beagles. Mean concentrations of CA-I and CA-II in erythrocytes of dogs native to Japan were 11.03+/-4.39 and 3.29+/-0.91 mg/g of Hb, respectively. Mean concentration of CA-I was greater in male dogs from Japan than female dogs from Japan. CONCLUSIONS AND CLINICAL RELEVANCE: The ELISA used in this study proved to be precise and sensitive for determining CA-I and CA-II concentrations in dogs. The ELISA may enable study of changes in isoenzymes associated with hereditary or metabolic disorders of blood or other body fluids, using only a small sample. Measurement of the concentrations of CA isoenzymes in dogs may be of diagnostic value.     

Transmission electron microscopy studies in an experimental model of canine atopic dermatitis

Impairment of skin barrier function has been hypothesized in canine atopic dermatitis (AD). In this prospective, controlled study, the ultrastructure of the upper epidermal layers was investigated using an experimental model of canine AD. Seven atopic Beagles sensitized to Dermatophagoides farinae and four healthy Beagles were used as controls. Both normal and atopic dogs were challenged with D. farinae for 3 days. Clinical signs were scored and skin biopsies were taken from the inguinal area before and 3 days after allergen exposure. Samples were processed to enhance lipid visibility and evaluated by Transmission Electron Microscopy. Emphasis was placed on evaluation of the lipid lamellae (LL), and lamellar bodies (LB) of the stratum corneum.
After allergen challenge, atopic Beagles developed severe pruritic dermatitis while no skin lesions were noted in the controls. Ultrastructurally, before allergen challenge, atopic Beagles displayed focally severe abnormalities in LL organization and wider intercellular spaces containing abnormal lipid material. In atopic Beagles, LBs were frequently found inside corneocytes while this finding was not observed in the controls. After allergen challenge, further increase of intercellular spaces was observed in the stratum corneum of atopic Beagles while no appreciable changes were observed in the normal dogs. Intercellular spaces in atopic Beagles were filled with abundant amounts of abnormal lipid material and highly disorganized LL. It is concluded that baseline differences in the ultrastructure of the skin exist between normal and experimentally sensitized atopic Beagles and that these changes are aggravated by allergen challenge and the resulting flare-up of dermatitis.     

Ultrasound‐guided approach for axillary brachial plexus,femoral nerve,and sciatic nerve blocks in dogs

Objective To describe an ultrasound‐guided technique and the anatomical basis for three clinically useful nerve blocks in dogs. Study design Prospective experimental trial. Animals Four hound‐cross dogs aged 2 ± 0 years (mean ± SD) weighing 30 ± 5 kg and four Beagles aged 2 ± 0 years and weighing 8.5 ± 0.5 kg. Methods Axillary brachial plexus, femoral, and sciatic combined ultrasound/electrolocation‐guided nerve blocks were performed sequentially and bilaterally using a lidocaine solution mixed with methylene blue. Sciatic nerve blocks were not performed in the hounds. After the blocks, the dogs were euthanatized and each relevant site dissected. Results Axillary brachial plexus block Landmark blood vessels and the roots of the brachial plexus were identified by ultrasound in all eight dogs. Anatomical examination confirmed the relationship between the four ventral nerve roots (C6, C7, C8, and T1) and the axillary vessels. Three roots (C7, C8, and T1) were adequately stained bilaterally in all dogs. Femoral nerve block Landmark blood vessels (femoral artery and femoral vein), the femoral and saphenous nerves and the medial portion of the rectus femoris muscle were identified by ultrasound in all dogs. Anatomical examination confirmed the relationship between the femoral vessels, femoral nerve, and the rectus femoris muscle. The femoral nerves were adequately stained bilaterally in all dogs. Sciatic nerve block. Ultrasound landmarks (semimembranosus muscle, the fascia of the biceps femoris muscle and the sciatic nerve) could be identified in all of the dogs. In the four Beagles, anatomical examination confirmed the relationship between the biceps femoris muscle, the semimembranosus muscle, and the sciatic nerve. In the Beagles, all but one of the sciatic nerves were stained adequately. Conclusions and clinical relevance Ultrasound‐guided needle insertion is an accurate method for depositing local anesthetic for axillary brachial plexus, femoral, and sciatic nerve blocks.     

Contrast harmonic imaging of canine hepatic tumors

Six adult healthy Beagles were used to investigate the hepatic perfusion dynamics of Levovist, a contrast agent used in contrast harmonic imaging (CHI). In addition, 8 dogs with hepatocellular carcinoma (HCC) and 2 dogs with metastatic hepatic hemangiosarcoma (HSA) were used to characterize both the CHI findings with Levovist. In the Beagles, the start of intravenously injected Levovist into the aorta between the cranial mesenteric and renal arteries and the portal vein at the hepatic hilum were 5.47 +/- 1.52 sec and 16.03 +/- 3.39 sec, respectively. As a characteristic CHI finding in the 8 dogs with HCC, the early arterial phase showed a fine network of blood flow enhanced at the surrounding region and within the tumor in all the 8 dogs (100%), and the post vascular phase demonstrated a defect in the whole tumor and an enhancement of the surrounding hepatic tissues in 7 dogs (87.5%). In the 2 dogs with HSA, characteristic finding in which the early arterial and late vascular phases showed a rim contrast enhancement pattern, and the post vascular phase revealed that the whole tumor lacked contrast enhancement and the surrounding hepatic tissues was clearly enhanced. In dogs, the start of the early arterial and late vascular phases, and the characterizations of the CHI findings in HCC and HSA were suggested to be similar to those in humans. Therefore, CHI is thought to be useful for the diagnosis of HCC and metastatic hepatic HSA in dogs as well as in humans.     

A comparative histochemical and morphometric study of canine skeletal muscle.

The purpose of this study was to determine whether there were differences in skeletal muscle properties in the hindlimb muscles of different types of dogs. Muscle samples were obtained from the gracilis, sartorius cranial head, sartorius caudal head and tibialis anterior muscles of mixed-breed and hound-type dogs and Beagles. Fiber type, fiber size and capillary morphometry determinations of each muscle from each dog were made from sections stained for myofibrillar ATPase activity. Individual animals were bilaterally symmetric for all measured variables. Fiber type, fiber size and capillary geometry varied between dogs of a given type and muscles within a given dog. There were no differences between dog types for fiber type or fiber size; significant variation in log(muscle)/log(body) mass ratios between dog types was observed for all muscles. The results indicate that for a given muscle, significant variation can occur in skeletal muscle characteristics between different types of dogs and that these differences can be independent of differences in exercise history.     

Osteology and Radiographic Anatomy of the Pelvis and Hind Limb of Healthy Ring‐Tailed Lemurs (Lemur catta)

In family Lemuridae, anatomical variations exist. Considering its conservation status (near threatened) and presence of similarities between strepsirrhines and primitive animals, it was thought to be beneficial to describe the gross osteology and radiographic anatomy of the pelvis and hind limb of ring‐tailed lemurs (Lemur catta) as a reference for clinical use and species identification. Radiography was performed in 14 captive adult ring‐tailed lemurs. The radiographic findings were correlated with bone specimens from two adult animals. Additionally, computed tomography of the hind limbs was performed in one animal. The pelvic bone has a well‐developed caudal ventral iliac spine. The patella has a prominent tuberosity on the cranial surface. The first metatarsal bone and digit 1 are markedly stouter than the other metatarsal bones and digits with medial divergence from the rest of the metatarsal bones and digits. Ossicles were seen in the lateral meniscus, inter‐phalangeal joint of digit 1 and in the infrapatellar fat pad. Areas of mineral opacity were seen within the external genitalia, which are believed to be the os penis and os clitoris. Variations exist in the normal osteology and radiographic appearance of the pelvis and hind limb of different animal species. The use of only atlases from domestic cats and dogs for interpretative purposes may be misleading.     

Thoracic wall and pulmonary trauma in dogs sustaining fractures as a result of motor vehicle accidents

The records of 267 dogs seen at the University of Minnesota Veterinary Teaching Hospital for fractures resulting from motor vehicle accidents were examined to determine the prevalence and types of thoracic wall and pulmonary trauma associated with such cases. Results were analyzed for type and prevalence of thoracic wall and pulmonary injury, and for the prevalence of such injury in dogs with and without extrathoracic injury, in dogs with fractures of single vs multiple bones, in dogs with single fractures of specific bones, in dogs with fractures in the cranial vs the caudal one half of the body, and in dogs with fractures ipsilateral vs contralateral to thoracic injury. The overall prevalence of thoracic wall and pulmonary trauma was 38.9%; pulmonary contusions, pneumothorax, and fractured ribs were the most common injuries. More than 1 type of thoracic wall or pulmonary injury was diagnosed in 57.7% of the cases. Of the dogs with thoracic injury, 24% also had extrathoracic injuries; 16.5% of dogs without thoracic injury had extrathoracic injuries, not including fractures. Of the dogs with fractures of 1 bone, 36.3% had thoracic injuries. Of the dogs with fractures of more than 1 bone, 42.3% had thoracic injuries. The prevalence of thoracic wall and pulmonary trauma was significantly associated with the site of the fracture (cranial vs caudal and ipsilateral vs contralateral); significant association with the specific bone fractured was also seen for some fractures.     

Energy requirements of puppies of two different breeds for ideal growth from weaning to 28 weeks of age

To ensure an optimal growth is crucial in raising healthy dogs, especially in large and giant breeds. Dogs with a moderate growth velocity tend to have lesser problems with developmental orthopaedic diseases than those with forced or maximum weight gain. In this study, the energy needs of growing dogs from two different breeds (Beagles as a medium‐size breed and Foxhound crossbreds as a large‐size breed) to ensure a growth development as recommended by the National Research Council (NRC) were determined at the age of 6–28 weeks. After weaning at the age of 6 weeks, the food rations sufficient to meet the energy requirements of each individual puppy were adjusted every other day according to growth level, guaranteeing a development consistent with the recommended weight curve for the respective breed size. The food and therefore energy intake of the puppies was registered daily; it ranged from 0.72 to 2.34 times the maintenance requirements with little effect of age. During the whole period, however, there was a consistent breed difference: Foxhound‐Boxer‐Ingelheim Labrador crossbreds (FBIs) had higher energy intakes expressed as multiples of maintenance than Beagles, suggesting that during the major period of growth, the energy requirement is not a function of age. Adult Beagles and FBIs showed similar differences in energy requirements as already during growth as shown in this study. This indicates that breed differences in energy requirements have already to be taken into account during growth. On the other hand, the results showed clearly lower energy needs for growth in these two different breeds than recommended in the NRC.     

Evaluation of urinary carnitine and taurine excretion in 5 cystinuric dogs with carnitine and taurine deficiency

Five client owned dogs with cystinuria were diagnosed with carnitine and taurine deficiency while participating in a clinical trial that used dietary management of their urolithiasis. Stored 24-hour urine samples collected from the cystinuric dogs before enrollment in the clinical diet trial were quantitatively evaluated for carnitine and taurine. These results were compared to those obtained from 18 healthy Beagles. Both groups of dogs were fed the same maintenance diet for a minimum of 2 weeks before 24-hour urine collection. The protocol used for 24-hour urine collections was the same for cystinuric dogs and healthy Beagles except that cystinuric dogs were catheterized at baseline, 8 hours, 12 hours, and at the end of the collection, whereas Beagles were catheterized at baseline, 8 hours, and at the end of the collection. Three of 5 dogs with cystinuria had increased renal excretion of carnitine. None of the cystinuric dogs had increased renal excretion of taurine, but cystinuric dogs excreted significantly less (P < .05) taurine in their urine than the healthy Beagles. Carnitinuria has not been recognized previously in either humans or dogs with cystinuria, and it may be 1 risk factor for developing carnitine deficiency. Cystinuric dogs in this study were not taurinuric; however, cystine is a precursor amino acid for taurine synthesis. Therefore, cystinuria may be 1 risk factor for developing taurine deficiency in dogs. We suggest that dogs with cystinuria be monitored for carnitine and taurine deficiency or supplemented with carnitine and taurine.     

Small intestinal bacterial overgrowth and enhanced intestinal permeability in healthy beagles.

The small intestine of healthy adult Beagles was examined to determine whether subclinical abnormalities might exist that would be relevant to the use of Beagles in pharmacologic studies. Duodenal juice was obtained for qualitative and quantitative bacteriologic examinations; jejunal mucosa was taken for morphologic and biochemical investigation, and intestinal permeability was assessed by quantification of 24-hour urinary excretion of 51Cr-labeled EDTA after its oral administration. Comparisons were made with findings in healthy adult dogs of other breeds that served as controls. Small intestinal bacterial overgrowth was found in 14 of the 21 Beagles examined, and represented a mixed flora that included obligate anaerobic bacteria in 8 dogs and exclusively aerobic bacteria in 6 dogs. Intestinal permeability (percentage urinary recovery of 51Cr-labeled EDTA; mean +/- SEM) was considerably higher (P < 0.01) in Beagles with anaerobic overgrowth (37.6 +/- 3.2%) or aerobic overgrowth (30.5 +/- 4.8%), compared with Beagles with no overgrowth (17.3 +/- 1.6%) and with controls (11.1 +/- 1.0%). In Beagles, significant (r = 0.54, P = 0.03) correlation was observed between 24-hour urinary recovery of 51Cr-labeled EDTA and bacterial numbers in duodenal juice. Morphologic changes in jejunal mucosa were minimal, and specific activities of brush border enzymes were not significantly decreased, apart from aminopeptidase N, but activities of lysosomal and endoplasmic reticular marker enzymes were higher in the 3 groups of Beagles with anaerobic, aerobic, or no overgrowth, compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of treatment with ticlopidine in heartworm-negative, heartworm-infected, and embolized heartworm-infected dogs.

Ticlopidine hydrochloride was evaluated for its effectiveness in inhibiting platelet aggregation and serotonin release in 5 laboratory Beagles before and after heartworm implantation with 7 adult Dirofilaria immitis, and after embolization with 7 dead heartworms to mimic what happens after heartworm adulticide treatment. Five other laboratory Beagles, similarly implanted and embolized with heartworms, were used as nonmedicated controls. During the heartworm-negative stage, the dosage of ticlopidine that inhibited adenosine diphosphate (ADP)-induced platelet aggregation in 5 dogs by at least 50% after 5 days of treatment was 62 mg/kg of body weight once a day. In the same dogs implanted with 7 adult heartworms 21 days previously, mean (+/- SD) ticlopidine dosage required to obtain similar results was 71 (+/- 13) mg/kg given once daily. During the 21 days after dead heartworms were implanted in heartworm-infected dogs, mean ticlopidine dosage was 108 (+/- 35) mg/kg (range, 62 to 150 mg/kg). Ticlopidine treatment was associated with increased platelet numbers in all 5 dogs during the heartworm-negative stage and in 4 of 5 dogs during the heartworm implantation and heartworm embolization stages. Mean platelet volume tended to decrease as platelet numbers increased. At necropsy, gross and histologic pulmonary lesions were less severe in ticlopidine-treated dogs than in nonmedicated control dogs.     

Radiographic study of the maxillary canine tooth in mesaticephalic dogs

Radiology is the most important diagnostic technique for evaluation of the radicular structure of the tooth and adjacent areas. However, superimposition of other oral or nasal structures often creates difficulties when interpreting radiographic images. The purpose of this study was to identify and locate any anatomical structures that may be superimposed over the root of the maxillary canine tooth in radiographs of dogs. Results showed that the nasal conchae minimally interfere with the visualization of the tooth. The vomer bone and maxillary structures (the conchal crest, the line of conjunction between the maxillary body and the palatine process, and the palatine sulcus) are visible as linear radiopacities, and were found to be responsible for most of the radiographic features in this area. The incisivomaxillary canal and the palatine fissure caused radiolucent images. The incisivomaxillary suture and the nasoincisive suture may appear as radiolucent images in young skulls and linear radiopacities in older skulls. It appears from this study that a compromise between minimal superimposition of dental and non-dental structures and small image distortion is needed to obtain diagnostic radiographic views of the maxillary canine tooth in mesaticephalic dogs. The relative positions of the conchal crest, the line of conjunction between the vertical body of the maxilla and its palatine process, the incisivomaxillary canal, and the tooth, cannot be changed radiographically because of the close anatomic position of these structures.     

Comparison of the biological activity of recombinant human thyroid-stimulating hormone with bovine thyroid-stimulating hormone and evaluation of recombinant human thyroid-stimulating hormone in healthy dogs of different breeds

OBJECTIVE: To evaluate whether use of recombinant human (rh) thyroid-stimulating hormone (TSH) induces equivalent stimulation, compared with bovine TSH (bTSH), and to evaluate activity of rhTSH in dogs of various large breeds. ANIMALS: 18 healthy research Beagles and 20 healthy client-owned dogs of various breeds with body weight > 20 kg. PROCEDURES: The 18 Beagles were randomly assigned to 3 groups, and each dog received either 75 microg of rhTSH, IM or IV, or 1 unit of bTSH, IM, respectively, in a crossover design. The 20 client-owned dogs received 75 microg of rhTSH, IV. Blood samples were taken before and 6 hours after TSH administration for determination of total serum thyroxine (T(4)) concentration. Additional blood samples were taken after 2 and 4 hours in Beagles that received rhTSH, IM. RESULTS: There was a significant increase in T(4) concentration in all dogs, but there were no differences between values obtained after administration of bTSH versus rhTSH or IV versus IM administration of rhTSH. Although there was a significant difference in age and body weight between Beagles and non-Beagles, there was no difference in post-TSH simulation T(4) concentration between the 2 groups. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated an equivalent biological activity of rhTSH, compared with bTSH. Use of 75 microg of rhTSH, IV, did not induce a different magnitude of stimulation in large-breed dogs, compared with Beagles. Euthyroidism was confirmed if post-TSH simulation T(4) concentration was > or = 2.5 microg/dL and at least 1.5 times basal T(4) concentration.     

Occurrence and pattern of long bone fractures in growing dogs with normal and osteopenic bones

A retrospective study was undertaken to record the occurrence and pattern of long bone fractures, and the efficacy of Intramedullary (IM) Steinmann pin fixing in growing dogs. All the records of growing dogs during a 10-year-period were screened to record the cause of trauma, the age and sex of the animal, the bone involved, the type and location of the fracture, the status of fixation, alignment, maintenance of fixation and fracture healing. The results were analysed and comparisons were made between growing dogs with normal and osteopenic bones. Among the 310 cases of fractures recorded, the bones were osteopenic in 91 cases (29%). Minor trauma was the principal cause of fracture in dogs with osteopenia (25%), and indigenous breeds were most commonly affected (38%). Fractures in dogs with osteopenic bones were most commonly recorded in the age group of 2-4 months (53%), whereas fractures in normal dogs were almost equally distributed between 2 and 8 months of age. Male dogs were affected significantly more often in both groups. In osteopenic bones, most fractures were recorded in the femur (56%), and they were distributed equally along the length of the bone. Whereas in normal bones, fractures were almost equally distributed in radius/ulna, femur and tibia, and were more often recorded at the middle and distal third of long bones. Oblique fractures were most common in both groups; however, comminuted fractures were more frequent in normal bones, whereas incomplete fractures were more common in osteopenic bones. Ninety-nine fracture cases treated with IM pinning (66 normal, 33 osteopenic) were evaluated for the status of fracture reduction and healing. In a majority of the cases (61%) with osteopenic bones, the diameter of the pin was relatively smaller than the diameter of the medullary cavity (<70-75%), whereas in 68% of the cases in normal bones the pin diameter was optimum. The status of fracture fixing was satisfactory to good in significantly more osteonormal (59%) than osteopenic dogs (42%). Fracture healing, however, was satisfactory in significantly more cases with osteopenic than normal bones. The appearance of callus was relatively early and the amount of bridging callus was relatively large in greater number of osteopenic bone fractures. Mal-union and non-union were recorded more often in osteopenic cases than in normal cases. However, the incidence of bone shortening and osteomyelitis was significantly higher in normal bones than in osteopenic bones.