Measurement of Bite Force in Dogs: A Pilot Study

A force transducer was developed to measure bite force in dogs. A total of 101 readings was obtained from 22 pet dogs ranging in size from 7 to 55 kg. Bite forces ranged from 13 to 1394 Newtons with a mean for all dogs of 256 Newtons and a median of 163 Newtons. Most measurements fell within the low end of the range, with 55% of the biting episodes less than 200 Newtons and 77% less than 400 Newtons.

The VetMousetrap: a device for computed tomographic imaging of the thorax of awake cats

The VetMousetrap, a novel device that allows computed tomography (CT) of awake cats and provides a clinically supportive environment, is described. Ten normal cats were used to test the device for ambient internal oxygen, carbon dioxide levels, and temperature. Twenty-two awake normal cats were imaged using a 16-multislice helical CT unit to evaluate dose-equivalent protocols. Two different X-ray tube potentials (kV), 80 and 120, and two different helical pitches, 0.562 and 1.75, were evaluated. The signal intensity of the pulmonary parenchyma (SIlung), signal intensity of background (SIbackgr), contrast, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were calculated. Three evaluators ranked the images for sharpness of liver margins, motion, helical, and windmill artifacts. CT was successfully completed in 20 of 22 cats. No artifacts directly related to the device were detected. Overall, 75 of 80 (94%) examinations were judged to have absent or minimal motion artifact. A statistically significant difference was found for SNR (P = 0.001) and CNR (P = 0.001) between all protocols. The higher pitch protocols had significantly lower noise and higher SNR and CNR, lower motion artifact but greater helical artifacts. A protocol using 80 kV, 130 mA, 0.5s, and 0.562 pitch with 1.25mm slice thickness, and 0.625 mm slice reconstruction interval is recommended. The VetMousetrap appears to provide the opportunity for diagnostic CT imaging of the thorax of awake cats.

Evaluation of an osteoconductive resorbable calcium phosphate cement and polymethylmethacrylate for augmentation of orthopedic screws in the pelvis of canine cadavers

OBJECTIVE

To evaluate the effect of an osteoconductive resorbable calcium phosphate cement (CPC) on the holding power of bone screws in canine pelvises and to compare the effect with that for polymethylmethacrylate (PMMA).

SAMPLE POPULATION

35 pelvises obtained from canine cadavers.

PROCEDURE

Each pelvis was sectioned longitudinally. Within each pair of hemipelvises, one 4.0-mm cancellous screw was placed in the sacroiliac (SI) region and another in the iliac body. Similar regions on the contralateral-matched hemipelvis were assigned 1 of 3 augmentation techniques (CPC-augmented 4.0-mm cancellous screws, PMMA-augmented 4.0-mm cancellous screws, and CPC-augmented 3.5-mm cortical screws). Pullout force was compared between matched screws and between treatment groups prior to examination of cross sections for evaluation of cement filling and noncortical bone-to-cortical bone ratio.

RESULTS

CPC and PMMA augmentation significantly increased pullout force of 4.0-mm screws inserted in the SI region by 19.5% and 33.2%, respectively, and CPC augmentation significantly increased pullout force of 4.0-mm cancellous screws inserted in the iliac body by 21.2%. There was no difference in the mean percentage augmentation between treatment groups at either location. Cement filling was superior in noncortical bone, compared with filling for cortical bone. Noncortical bone-to-cortical bone ratio was significantly greater in the sacrum (6.1:1) than the ilium (1.3:1).

CONCLUSIONS AND CLINICAL RELEVANCE

CPC and PMMA improve the ex vivo holding strength of 4.0-mm cancellous screws in the SI and iliac body regions and SI region, respectively. Cement augmentation may be more effective in areas with greater noncortical bone-to-cortical bone ratios.

Tablet computers in the veterinary curriculum

Tablet computers offer a new method of information management in veterinary medical education. With the tablet computer, students can annotate class notes using electronic ink, search for keywords, and convert handwriting to text as needed. Additional electronic learning resources, such as medical dictionaries and electronic textbooks, can be readily available. Eleven first-year veterinary students purchased tablet computers and participated in an investigation of their working methods and perceptions of the tablet computer as an educational tool. Most students found the technology useful. The small size and portability of the tablet allowed easy transport and use in a variety of environments. Most students adapted to electronic notetaking by the second week of classes; negative experiences with the tablet centered on a failure to become comfortable with taking notes and navigating on the computer as opposed to writing and searching on paper. A few performance-related problems, including short battery life, were reported. Tablet software allowed conversion of faculty course notes from a variety of original formats, meaning that instructors could maintain their original methods of note preparation. Adopting a consistent naming convention for files helped students to locate the files on their computers, and smaller file sizes helped with computer performance. Collaboration between students was fostered by tablet use, which offers possibilities for future development of collaborative learning environments.

The effect of axial and abaxial release on meniscal displacement in the dog

The meniscal release (MR) is used to minimize meniscal pathology after Tibial Plateau Leveling Osteotomy (TPLO) surgery. The purposes of this study were: (i) to describe meniscal orientation in a unaltered cadaveric canine stifle, a cruciate deficient stifle, TPLO repaired stifle with and without the MR using magnetic resonance imaging; (ii) to determine if the abaxial release is equivalent to the axial release in its ability to affect caudal pole displacement in a TPLO repaired stifle and (iii) to evaluate with MRI the effect of MR on the femorotibiol articular cartilage contact area in a TPLO repaired stifle. Briefly, cadaver limbs were placed into a jig designed to mimic a weight-bearing stance at 140 degrees and 90 degrees at the stifle. The limbs were sequentially evaluated from the unaltered state; after cranial cruciate ligament transection; after TPLO stabilization; and finally after a meniscal release. No significant difference was found between the intrameniscal area (IMA) of the abaxial and axial meniscal releases although there was an increase in the IMA after the meniscal release compared to the IMA in the normal, cranial cruciate ligament deficient stifle, and TPLO stabilized stifle. In the abaxial release, a meniscal remnant remained in situ and provided a space effect between the femur and the tibial plateau. This is in contrast to the axial meniscal release, where the entire caudal pole of the medial meniscus relocated caudolaterally and consequently permitted more direct femorotibial contact. Overall, however, there was evidence of caudal pole compression of the medial meniscus throughout the MRI series which was ameliorated by either of the MR procedures.

A Mechanical Comparison of 4.5 mm Narrow and 3.5 mm Broad Plating Systems for Stabilization of Gapped Fracture Models

OBJECTIVE

To evaluate and compare the mechanical properties of 4.5 narrow and 3.5 broad plating systems using their respective cortical and cancellous screws in unstable, central, and eccentric gap fracture models.

STUDY DESIGN

Mechanical evaluation and comparison of 2 dynamic compression plate (DCP) systems.

SAMPLE POPULATION

Eighteen cortical and 30 cancellous gapped fracture models.

METHODS

DCP (4.5 mm narrow, 3.5 mm broad) with their respective cortical screws were applied to cortical bone density polyurethane foam blocks to construct center gap cortical fracture models that were tested in gap closing monotonic 4-point bending. DCP (4.5 mm narrow, 3.5 mm broad) with their respective cancellous screws were applied to cancellous bone density polyurethane foam blocks to construct eccentric gap cancellous fracture models. The cancellous constructs were tested in monotonic gap opening and gap closing cantilever bending and in cyclic axial loading. Univariate and multivariate repeated measures ANOVA were used to compare the maximum loads at failure of the 4.5 mm constructs and 3.5 mm constructs.

RESULTS

The 4.5 mm narrow plating system withstood significantly higher loads at failure than the 3.5 mm broad plating system in 4-point bending (P<.0001) and gap opening cantilever bending (P<.0001). The 4.5 mm system failed in gap closing cantilever bending by plastic deformation of the plate, whereas the 3.5 mm system failed by screw pullout. There was no difference between the 2 systems in cyclic axial loading.

CONCLUSION

Results indicate that the 4.5 mm narrow plating system has a mechanical advantage over the 3.5 mm broad plating system for stabilization of gapped fracture models.

CLINICAL RELEVANCE

The 4.5 mm narrow plating system may be mechanically advantageous compared with the 3.5 mm broad plating system for stabilizing unreconstructed comminuted long bone fractures in large dogs.

Comparison of the effects of four different power scalers on enamel tooth surface in the dog

The surface roughness of tooth enamel was quantitatively evaluated following scaling with four power scalers at three different tip forces. Ceramic and tooth samples were evaluated for surface roughness using surface profilometry. Applied tip forces were produced with a horizontal balanced arm holding the scaler handpiece and load weight, and were measured using a load cell. The power scalers evaluated were the ultrasonic piezoelectric, ultrasonic magnetostrictive (ferromagnetic stack), sonic, and rotosonic. For the tooth samples, at 50 grams of force, the piezoelectric, magnetostrictive, and sonic scaler roughnesses were similar and the rotosonic scaler outcome was statistically higher. Increasing the applied force significantly increased the roughness produced by the rotosonic and piezoelectric scalers. The results of this study indicate that the type of power scaler and applied tip force used determines the post-scaling surface roughness of ceramic and tooth enamel surfaces.

Evaluation of a skin stapler for belt-loop gastropexy in dogs

A new method for attachment of a belt-loop gastropexy using disposable, stainless steel skin staples was compared with a traditional hand-sewn belt-loop gastropexy technique in 24 fresh dog cadavers. Mean gastropexy times were 212 seconds for the stapled technique and 435 seconds for the hand-sewn technique. The stapled belt-loop gastropexy was significantly faster than the hand-sewn technique (P less than 0.001). There was no statistically significant difference in the mean maximum tensile strength between the two attachment methods. This study provides a basis for clinical evaluation of the stapled belt-loop gastropexy technique in dogs.

Triple pelvic osteotomy: effect on limb function and progression of degenerative joint disease

The objective of this study was to evaluate prospectively the outcome of 21 clinical patients treated with triple pelvic osteotomies during the year following surgery. Specific aims included documenting the time of and extent of improved limb function as measured by force plate analysis, evaluating the progression of degenerative joint disease (DJD) in the treated and untreated coxofemoral joints, and determining whether or not triple pelvic osteotomy resulted in degenerative joint changes in the ipsilateral stifle and hock. Twelve dogs were treated unilaterally and nine dogs were treated bilaterally with triple pelvic osteotomies. There were no differences in mean anteversion angles, angles of inclination, or preoperative DJD between treated hips and untreated hips. Degenerative joint disease progressed significantly in all hips regardless of treatment. Two cases developed hyperextension of their hocks after the triple pelvic osteotomies. However, no radiographic evidence of DJD was observed for any of the stifles or hocks at any observation time. A significant increase in vertical peak force (VPF) scores was noted for treated legs by two-to-three months after surgery, which continued over time. Untreated legs did not show a significant change in VPF scores over time. No differences were found in progression to higher scores when unilaterally treated legs, first-side treated legs, and second-side treated legs were compared.

Rehabilitation of dogs with surgically treated cranial cruciate ligament-deficient stifles by use of electrical stimulation of muscles

OBJECTIVE

To determine effect of electrical muscle stimulation (EMS) on rate and degree of return to function of the limb and development of degenerative joint disease (DJD) after surgical creation and subsequent stabilization of the cranial cruciate ligament (CrCL)-deficient stifle.

ANIMALS

12 clinically normal adult large (19.5 to 31.5 kg) dogs.

PROCEDURE

Dogs were anesthetized, and the right CrCL was severed via arthrotomy, destabilizing the stifle. After 3 weeks, the stifle was surgically stabilized. Three weeks later, 6 dogs were subjected to an EMS treatment protocol for the thigh muscles. At 5, 9, 13, and 19 weeks after stifle destabilization, treated (n = 6) and control (n = 6) dogs were evaluated for return of stifle function. Gross and histologic evaluations of the stifles were performed at 19 weeks after stifle destabilization.

RESULTS

Treated dogs had significantly (P = 0.001) better lameness score than did control dogs. There was less palpable crepitation of the stifle in treated dogs (P = 0.06); treated dogs also had significantly (P = 0.01) fewer radiographic signs of bone changes. Thigh circumference was significantly (P = 0.02) larger in treated dogs. There was less gross cartilage damage (P = 0.07) in the EMS-treated dogs, but more medial meniscal damage (P = 0.058, cranial pole; P = 0.051, caudal pole).

CONCLUSIONS

Improved lameness scores, larger thigh circumference, and decreased radiographically apparent bony changes observed for the treated group of dogs support the hypothesis that dogs treated by EMS after surgical stabilization of the CrCL-deficient stifle had improved limb function, with less DJD, than did dogs treated with the currently accepted clinical protocol of cage rest and slow return to normal activity. However, results of force plate evaluation did not support the hypothesis. Increased meniscal damage in dogs treated by EMS may be cause for concern.

Correlation between anatomic features and low-field magnetic resonance imaging of the equine metacarpophalangeal joint

OBJECTIVE

To expand our current knowledge and to establish limits of correlation between signal intensities of the magnetic resonance (MR) image and actual macroscopic and microscopic anatomic features of the imaged structures of the equine metacarpophalangeal joint (MCPJ).

SAMPLE POPULATION

The right MCPJ was obtained from 4 adult horses that were euthanatized for reasons unrelated to the musculoskeletal system.

PROCEDURE

The distal portion of the right forelimbs was collected from 4 equine cadavers. The bones were drilled to provide fixed reference points and examined by MR imaging. After imaging, the joints were sectioned for gross and histologic inspection. The MR images were aligned and correlated with digitized gross and histologic images to identify tissue types.

RESULTS

Comparison of the images resulted in identification of different bone types, articular cartilage, and soft tissue structures of the equine MCPJ.

CONCLUSION

Results provided relevant information regarding the appearance of the imaged tissues of the equine MCPJ.

CLINICAL RELEVANCE

Although MR imaging does not have current clinical applications for equine practitioners, its wide acceptance as the imaging modality used for most human musculoskeletal derangements may aid in developing more realistic applications in equine medicine.

Evaluation of fibular head transposition, lateral fabellar suture, and conservative treatment of cranial cruciate ligament rupture in large dogs: a retrospective study

Sixty-one large dogs (weighing 22.7 kg or more) with cranial cruciate ligament ruptures (CCLRs) were treated with either fibular head transpositions (FHTs; n = 22 stifles), lateral fabellar sutures (LFSs; n = 39 stifles), or conservatively (CT; n = 11 stifles) with rest and aspirin. Based on owner evaluation, dogs treated with FHTs or CT did not perform as well as dogs treated with LFSs (p less than 0.05). There was no difference in owner evaluation scores for the dogs treated with FHTs or CT. Thirty dogs were reevaluated by investigators. No differences between treatment groups regarding age, sex, or time until diagnosis were noted. No differences in scores for lameness, stifle instability, or forceplate analysis among the treatment groups were observed. Degenerative joint disease progressed or remained severe regardless of treatment, based upon radiographic evidence.

Measurement of bite force in dogs: a pilot study

A force transducer was developed to measure bite force in dogs. A total of 101 readings was obtained from 22 pet dogs ranging in size from 7 to 55 kg. Bite forces ranged from 13 to 1394 Newtons with a mean for all dogs of 256 Newtons and a median of 163 Newtons. Most measurements fell within the low end of the range, with 55% of the biting episodes less than 200 Newtons and 77% less than 400 Newtons.

An approach to validation of a leg simulation by the comparison of two dynamic models

The dynamics of a jointed leg were simulated using two different models, one based on a recursive Newton-Euler method and one on a closed-form Lagrange method. To validate the models, the simulations were run in parallel and the intermediate steps and output of the two methods were compared to one another to reveal the presence and locations of errors. Sources of error and the use of this method for the detection of errors are discussed. Some errors could not have been detected using only a single simulation.

Three-dimensional kinematics of the intact and cranial cruciate ligament-deficient stifle of dogs

Joint motion was measured for the intact and cranial cruciate ligament (CCL)-deficient stifle in five large dogs using an instrumental spatial linkage and radiophotogrammetry. The linkage was directly attached to the bones using modified bone plates. Motion data were presented in terms of a clinical coordinate system. Stifle kinematics were highly reproducible for a given dog. For intact stifle kinematics, the swing phase included flexion-extension, internal-external rotation and abduction-adduction, while stance-phase kinematics included only flexion-extension. Loss of the CCL altered joint kinematics over the entire gait cycle. At the swing-stance transition, the CCL-deficient stifle demonstrated an abrupt cranial subluxation of the tibia which was sustained throughout stance. At the beginning of the swing phase the CCL-deficient joint returned to the cranial-caudal alignment seen in the intact joint. The dog's stifle was shown to be CCL-dependent during stance. The dog compensated for CCL loss by reducing the external limb load and by carrying the limb in greater flexion throughout the gait cycle, but was unable to prevent joint subluxation during stance. Stifle kinematics are greatly altered following CCL loss. It is the repetitive, mechanical, dynamic subluxation in a CCL-deficient joint which may be the cause of joint degeneration.

Joint laxity and its association with hip dysplasia in Labrador retrievers

A study was done to determine whether radiographic-distraction measurement of coxofemoral joint (hip) laxity at 4 and 8 months of age can serve as a predictor of hip dysplasia in older Labrador Retrievers. The method of Smith, Biery, and Gregor was used for radiologic examination of hips and for evaluation of radiographs. Mean (+/- SEM) distraction laxity (ie, distraction index) for 10 adult disease-free dogs was 0.29 +/- 0.05, whereas a group of 8 dogs with dysplastic hips had mean distraction index of 0.60 +/- 0.10 (P < 0.05). Mean distraction index at 4 months of age for 11 pups of 4 litters from matings between dogs with normal hips was 0.39 +/- 0.07, and was 0.54 +/- 0.04 for 31 pups of 7 litters from matings between dogs with hip dysplasia. The distraction index and, thus, joint laxity at that age was significantly (P = 0.0351) different for the 2 groups. The distraction index at 4 months correlated positively with the distraction index at a later age at necropsy (r = 0.43; P = 0.0289). Distraction index < 0.4 at 4 months of age predicted normal hips in 88% of cases and distraction index > or = 0.4 predicted hip dysplasia in 57% of the dogs. Logistic regression modeling indicated that the odds of a hip being normal decreased with increasing distraction index, and thus, with increasing joint laxity. The logistic regression models provided a reasonable mathematical description of the data. Based on the logistic model of the data, distraction indexes between 0.4 and 0.7 at either 4 or 8 months of age were not associated strongly enough with evidence of disease to be clinically reliable in predicting, on an individual basis, the outcome for dysplastic hip conformation when dogs were older. Index > 0.7 was associated with high probability for developing dysplastic joints and distraction index < 0.4 predicted normal hips with high probability.

Evaluation of support bandaging during measurement of proximal sesamoidean ligament strain in horses by use of a mercury strain gauge

Liquid mercury strain gauges were implanted in the forelimb proximal sesamoidean ligaments (PSL) of 8 adult horses. The gauges measured PSL strain while horses were standing with or without external support. In 6 of the horses, the gauges also measured PSL strain in horses at a walk, with or without external support. Gauges were enclosed within sliding polypropylene tubes to prevent nonaxial deformation. Each gauge was placed in 1 arm of a low-resistance half-bridge circuit. To provide temperature compensation, a dummy gauge was placed in the adjacent arm of the bridge circuit and was implanted next to the active gauge in the surrounding fascial tissue. External support included fiberglass cast support (CAST), dorsal fetlock splint support (DFS), support wraps of 3 bandage materials (SW1, SW2, and SW3), and support wrap with caudal splint (SW4). The cast was applied, with the fetlock and foot in weightbearing position, from the proximal portion of the metacarpus distal to and including the foot. The DFS was applied by placing the cranial half of the fiberglass cast on the dorsal aspect of the instrumented limb. The SW1, SW2, and SW3 were applied in a figure-8 pattern around the fetlock, using 50% of the linear stretch capacity of the bandage material, with the horse standing squarely on all 4 limbs. The SW4 was applied identically to the other support wraps, with the exception of addition of a flexible caudal splint incorporated in the support wrap. Mean maximal strain while standing (epsilon S) without external support for 8 horses was 6.0% (range, 3.8 to 7.5%).(ABSTRACT TRUNCATED AT 250 WORDS)

Composition and morphologic features of the interosseous muscle in Standardbreds and Thoroughbreds

Suspensory ligaments (SL) from 32 Thoroughbreds and 32 Standardbreds were collected to evaluate the variation in muscle content with respect to age, breed, sex, limb, and use. Six transverse sections, each 3 to 5 mm thick, were obtained from each SL. Four sections were taken from the body of the SL and 1 from the midportion of each branch. Sections were stained with van Gieson picric acid-fuchsin solution, then photographed, and black-and-white slides were made from the processed negatives. The transverse-sectional area of the SL and the contained muscle were determined by use of a computer with a color monitor and a digitizing device with its associated software. The percentage of muscle was then calculated for each section, for the entire ligament, and for each horse. Results were analyzed by multiple-regression analysis and Duncan multiple-range test, using the General Linear Model of SAS. Standardbreds had 40% more muscle in their SL than did Thoroughbreds. There was no significant difference in the percentage of SL muscle among sex, age, use, individual limb, or forelimb vs hind limb. For Standardbred horses, females had significantly greater muscle area content than intact males. Also, hind limb muscle area content was significantly greater than forelimb muscle content. Thoroughbred horses between 2 and 10 years of age not in training had significantly more muscle content than horses of the same age not in training. The reasons for these differences remain unclear.

Biomechanical properties of canine cortical bone allografts: effects of preparation and storage

The effects of various preparation and storage procedures and of different storage times on structural properties of canine cortical bone allografts were determined by evaluation of the compressive load to failure of a whole diaphyseal segment, the ability of a screw to resist being pulled from a cortical segment, and the torque required to strip the threads of a screw hole in a cortical segment. Preparation and storage procedures evaluated were sterile collection and storage at -20 C; ethylene oxide sterilization and storage at room temperature (22 C); chemical sterilization (methanol and chloroform, then iodoacetic acid) and storage at -20 C; and chemical sterilization, partial decalcification, and storage at -20 C. Storage times were 1, 16, and 32 weeks for each procedure. After 1 week of storage, aseptically collected frozen bone and ethylene oxide-sterilized bone had an increase, compared with matched controls, in load to failure in compression, but pullout load or screw-stripping torque did not change. Chemically sterilized bone had not changed after 1 week of storage, whereas chemically sterilized and partially decalcified bone had a 40% to 60% decrease in compressive load to failure, pullout load, and screw-stripping torque. Chemically sterilized and partially decalcified bone remained weak after 16 and 32 weeks of storage. Significant structural alterations were not detected in aseptically collected bone after 16 or 32 weeks of storage. Ethylene oxide-sterilized bone had a reduced pullout load after 32 weeks of storage. Chemically sterilized bone had significantly reduced compressive load to failure and pullout load after 16 and 32 weeks of storage.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of screw removal on bone strain in an idealized plated bone model

An idealized plated bone model was used to test the hypothesis that selected screw removal could alter the bone strain field and be a viable treatment for stress protection osteoporosis. Eighteen bone screw modifications were evaluated for their effects on bone strain. The three variables studied were number, position, and length of screws. Removal of two or four bone screws from an eight hole plate significantly increased the strain per load on the bone model over the values with eight screws in the plate (p less than 0.05). The four screw configurations increased bone strain more than the six screw configurations. It also was shown that the position of screws in the plate could significantly alter the bone strain per load results. Removal of six bone screws from an eight hole plate also increased the bone strain per load, but to excess in some tests. In those configurations, the results were not statistically different from the unplated configuration. Replacement of the full length screws with eight half length screws that engaged only the near cortex significantly reduced bone strain per load as compared with eight bicortical bone screws.

A comparison of steady state and transient thermography techniques using a healing tendon model

Steady state and transient thermal techniques were used to define the thermal signatures of surgically sectioned and sham-operated common calcanean tendons in four dogs. All limbs were imaged from the lateral side using an Inframetrics 525 system at - 1, 2, 4, 6, and 8 weeks after surgery. Individual video frames were used to compute absolute surface temperatures and rewarm curves for five predetermined 1 cm2 skin areas. Angiography was performed at each observation period to correlate changes in vascular morphology and thermal data. Thermal signatures and angiograms were similar in all animals before surgery. At 2 and 4 weeks after surgery, the absolute surface temperatures of the entire lateral crus area were elevated in three of four animals. During weeks 6 and 8, the surface temperatures, rewarm curves, and angiograms returned to presurgical values for the controls. Skin areas over the repaired tendons remained warmer and were shown to correlate with vascular proliferation by transient but not steady state techniques. Steady state and transient thermal imaging techniques can be used to detect vascular changes in the area around a healing tendon. However, our data indicate that transient thermal techniques are more suitable than steady state methods for localizing vascular disturbances in tissues. Thermographic imaging techniques may become a reliable noninvasive method to monitor wound healing processes if starting temperatures, cool down techniques, and time intervals for data collection are fully evaluated in future studies using transient thermal imaging protocols.

Uterine motility during the estrous cycle: studies in healthy bitches

Natural and drug-induced uterine motilities (UM) were recorded via uterine-implanted catheter-tip pressure transducers in 5 bitches during proestrus and estrus and in 6 bitches during early (30 days) and late (60 days) diestrus. The UM was monitored in unanesthetized bitches for 2 days after the estrous-cycle stage had been determined by vaginal cytologic findings. Natural UM, expressed as Alexandria units (pressure X frequency X duration of contractions), was greatest during estrus, moderate during proestrus, and appreciably decreased or lacking during early and late diestrus. During proestrus and estrus, prostaglandin F2 alpha (5 micrograms/kg of body weight, IV) induced intrauterine pressures of 107 and 115 mm of Hg, respectively, and oxytocin (0.05 USP units/kg, IV) induced pressures of 106 and 116 mm of Hg, respectively. In contrast, the intrauterine pressure values induced by prostaglandin F2 alpha given IV during early and late diestrus were 61 and 58 mm of Hg, respectively, and for oxytocin, were 61 and 51 mm of Hg, respectively. Prostaglandin F2 alpha given IM (50 micrograms/kg) also induced a greater intrauterine pressure during proestrus and estrus than during diestrus. We concluded that in the bitch, natural and drug-induced UM are decreased during early and late diestrus.

Effects of isobutyl-2-cyanoacrylate on bone healing

An in vivo evaluation of isobutyl-2-cyanoacrylate as an osseous adhesive was performed to determine its effect on bone healing. Oblique cortical fractures were induced at the tibial-fibular junctions of adult rabbits. Forty-eight fractures were repaired by the use of isobutyl-2-cyanoacrylate and a full cerclage wire. The opposite control fracture was repaired with a full cerclage wire only. One hundred percent of the glued fractures were not united through the glue interface, although normal periosteal new bone formation (secondary bone healing) took place around the glue. One hundred percent of the nonglued fractures healed by secondary bone union. Reactions were not seen in the bone or soft tissue adjacent to the adhesive material.

Osteochondritis dissecans of the femoral head of a Pekingese

An 8-month-old male Pekingese was admitted with a 1-month history of right hindlimb lameness and crepitation in the right coxofemoral joint. There was radiographic evidence of a focus of subchondral osteolysis of the right femoral head. The tentative diagnosis was avascular necrosis of the femoral head. The problem was corrected by femoral head ostectomy. Gross and microscopic examination of the femoral head resulted in a diagnosis of osteochondritis dissecans. Osteochondritis dissecans is an uncommon diagnosis both in small breeds of dogs and in the coxofemoral joint.

Chondrolysis associated with cartilage canals of the epiphyseal cartilage of the distal humerus of growing pigs

The articular-epiphyseal (A-E) cartilage of the distal humeri of 7 pigs weighing 13.1 to 18.2 kg and of 3 pigs weighing 36.4 to 40.9 kg was studied. Frozen samples of A-E cartilage were stained for the presence of reduced nicotinamide adenine dinucleotide dehydrogenase, lactate dehydrogenase, isocitrate dehydrogenase, and uridine diphosphate galactose-4-epimerase. Additional frozen sections and paraffin-processed sections were stained using the Alcian blue-critical electrolyte concentration method, safranin O-fast green, and hematoxylin and eosin. An area of grossly visible, opaque A-E cartilage of the medial condyle corresponded to regions of chondrolysis of the epiphyseal cartilage. The chondrolytic regions contained chondrocytes that did not stain for enzymes, had reduced staining for proteoglycans in the matrix, and were located at the site where the A-E cartilage increased in thickness. Cartilage canals were associated with the chondrolytic areas. Cartilage canals in both groups of pigs were commonly in various stages of chondrification, some of which were associated with degenerative cartilage. The regions of chondrolysis may indicate sites of biomechanical weakness in the A-E cartilage during the transformation of the epiphyseal cartilage into bone.

Effects of whole blood clots, time, and implant size on vascularization and collagen deposition along Teflon-ensheathed carbon fibers implanted in ewes

Seventy-two subcutaneous implants were examined to evaluate connective tissue response to Teflon-ensheathed carbon fibers and whole blood clots. Carbon fibers significantly (P less than or equal to 0.001) increased vascularization and collagen formation within the Teflon sheath. Carbon fibers provide a potentially strong scaffold that would physically support cell migration during wound healing. However, obvious foreign body reactions occurred, which indicate that further studies on the biologic features of carbon fiber are needed before carbon fibers become entirely acceptable for long-term implantation. Compared with no-clot controls, Teflon tubes containing only whole blood clots stimulated a significant (P less than or equal to 0.001) wound-healing response, including organized collagen fiber formation. Other variables tested in this study such as length and diameter of the Teflon tubes did not significantly influence connective tissue responses.

Evidence for an oscillator other than luteinizing hormone controlling the secretion of progesterone in cattle

The objective of this study was to quantify and compare the frequencies of pulses in ovarian and systemic concentrations of progesterone, systemic concentrations of luteinizing hormone (LH) and rate of ovarian blood flow. Blood was collected simultaneously from previously implanted catheters in the ovarian venous circulation and jugular vein on Day 12 or 13 of estrous cycles from 4 nonlactating dairy cows. Blood was collected at a rate of 2.5 ml/min for 5 min out of every 10 min over an 8-h period. The mean rate of blood flow in the ovarian artery during the 5-min collection period was estimated by an electromagnetic blood flow transducer. Pulses were observed over time in both ovarian and systemic concentrations of progesterone at frequencies that ranged between 0.625 and 0.875 cycles/h (1.1 to 1.5 h/cycle) among the animals. Only one or two episodes of release of LH were observed during the 8-h period, and transient increases in blood flow to the ovaries were associated temporally with each episode of LH release. The estimated frequencies for release of LH and increased blood flow were the same for each animal and ranged between 0.250 and 0.375 cycles/h. A second cycle with a frequency similar to that for LH was evident in the spectral density functions for ovarian and systemic concentrations of progesterone. This cycle was eliminated when the cycle for LH was removed from the data for progesterone, but the magnitude and frequency of the pulses in progesterone were not affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Three-dimensional osteometric scaling and normative modelling of skeletal segments

Many analytical biomechanics methods require extensive three-dimensional descriptions of anatomical geometry. In particular, researchers requiring the three-dimensional coordinates of specific boney landmarks (e.g. tendon and ligament attachments) are often forced to extrapolate such measurements from an experimental specimen set to their subject geometry. This work offers an approach to two problems inherent above; accurate extrapolation of specimen landmark locations to subject homologues and statistical accumulation of normative three-dimensional anatomical landmark data bases. A least squares solution for an affine scaling transformation from specimen to subject is used which incorporates both right-left and same hand comparisons. A two stage technique is formulated to consecutively remove landmark location variation and to size a normative specimen from a set of similar specimens. This ability to statistically represent a specimen set will provide better geometric models for other analytical studies and prosthetic design and evaluation.