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Abstract

OBJECTIVE

To determine the effects of 2 augmentation techniques on the mechanical properties of titanium cannulated bone screws.

SAMPLE

33 titanium cannulated bone screws (outer diameter, 6.5 mm; guide channel diameter, 3.6 mm).

PROCEDURES

11 screws were allocated to each of 3 groups. The guide channel of each screw was filled with polymethyl methacrylate bone cement alone (OCS group) or in combination with a 3.2-mm-diameter orthopedic pin (PCS group) or remained unmodified (control group) before mechanical testing. Each screw underwent a single-cycle 3-point bending test to failure with a monotonic loading rate of 2.5 mm/min. Failure was defined as an acute decrease in resistance to load of ≥ 20% or a bending deformation of 15 mm. Mechanical properties were determined for each screw and compared among the 3 groups.

RESULTS

All screws in the control and OCS groups and 1 screw in the PCS group broke during testing; a 15-mm bending deformation was achieved for the remaining 10 screws in the PCS group. Maximum load and load at failure differed significantly among the 3 groups. Stiffness and load at yield for the PCS group were significantly greater than those for the control and OCS groups but did not differ between the control and OCS groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of bone cement and an orthopedic pin to fill the guide channel of cannulated screws significantly increased the strength of the construct, but ex vivo and in vivo studies are necessary before this augmentation technique can be recommended for clinical patients.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effects of phenylbutazone (PBZ) on bone activity and bone formation in horses.

Animals—12 healthy 1- to 2-year-old horses.

Procedures—Biopsy was performed to obtain unicortical bone specimens from 1 tibia on day 0 and from the contralateral tibia on day 14. Fluorochromic markers were administered IV 2 days prior to and on days 0, 10, 15, and 25 after biopsy was performed. Six horses received PBZ (4.4 mg/kg of body weight, PO, q 12 h) and 6 horses were used as controls. All horses were euthanatized on day 30 and tissues from biopsy sites, with adjacent cortical bone, were collected. Osteonal density and activity, mineral apposition rate (MAR), and percentage of mineralized tissue filling the biopsy-induced defects in cortical bone were assessed. Serum samples from all horses were analyzed for bone-specific alkaline phosphatase activity and concentration of PBZ.

Results—MAR was significantly decreased in horses treated with PBZ. Regional acceleratory phenomenon was observed in cortical bone in both groups but was significantly decreased in horses treated with PBZ. Osteonal activity was similar at all time points in all horses. In control horses, percentage of mineralized tissue filling the cortical defects was significantly greater in defects present for 30 days, compared with defects present for 14 days. Differences in percentage of mineralized tissue were not detected in horses treated with PBZ.

Conclusions and Clinical Relevance—PBZ decreased MAR in cortical bone and appeared to decrease healing rate of cortical defects in horses. (Am J Vet Res 2000;61:537–543)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To assess biometric tools for gait analysis in healthy calves by use of pressure mat sensors, a handheld algometer, and serial circumferential measurements of selected joints.

Animals—20 six- to eight-week-old healthy male Holstein calves.

Procedures—Calves were evaluated over a 4-day period. Gait analysis was performed by training calves to walk over a pressure-sensitive mat, which recorded quantitative measurements. An algometer was applied perpendicular to each joint until an aversion response was observed or a preset limit of 50 N/cm2 was obtained. Circumference measurements of the carpal and tarsal joints were obtained by the application of a flexible measuring tape to defined areas of each limb. Variability between joint circumference measurements and pressure mat variables were analyzed with a standard least squares means model. Algometer measurements were dichotomized, and logistic regression was used to assess the probability that a calf reacted to algometer-applied pressure.

Results—1 calf was removed from the study because of lameness. Mean carpal and tarsal joint circumference measurements were reliable and consistent among calves. Algometry results suggested that healthy calves were more sensitive to pressure applied to the elbow and stifle joints, compared with pressure applied to the carpal, tarsal, and metacarpophalangeal or metatarsophalangeal joints. Pressure mat variables of stance time and stride velocity varied greatly among calves, whereas impulse and maximum forces varied little.

Conclusions and Clinical Relevance—Findings can serve as reference points for other studies and be used for comparison with results for calves with lameness or altered gaits.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the precision of a clinical illness score (CIS) system for identification of clinical signs in calves with experimentally induced Mycoplasma bovis pneumonia and to evaluate the accuracy of CISs in relation to pulmonary consolidation scores assigned at necropsy.

Animals—178 Holstein bull calves that were 52 to 91 days of age at the time of pneumonia induction.

Procedures—5 trials involved calves challenged with M bovis and scheduled for euthanasia and necropsy 12 to 24 days afterward. Nine veterinarian observers with various degrees of experience simultaneously assigned CISs to calves within 48 hours before necropsy. The precision of the CIS system among observers was evaluated via the Cohen κ statistic. The accuracy of each observer's CISs relative to 6 cutoffs (≥ 5%, ≥ 10%, ≥ 15%, ≥ 20%, ≥ 25%, and ≥ 30%) of percentage pulmonary consolidation was determined by comparing prenecropsy CISs with the gross pulmonary consolidation scores assigned at necropsy. Estimates for sensitivity and specificity were calculated relative to the 6 pulmonary consolidation cutoffs.

Results—A slight level of agreement was evident among observers (κ range, 0.10 to 0.21 for the individual trials) and overall (κ = 0.16; 95% confidence interval, 0.10 to 0.24). Median sensitivity and specificity changed with pulmonary consolidation score cutoff. Median sensitivity for all observers ranged from 81.7% to 98.9%, and median specificity ranged from 80.8% to 94.9% over all cutoff values.

Conclusions and Clinical Relevance—Agreement among observers assigning CISs to calves was low; the accuracy of the CIS system in relation to that of pulmonary consolidation scoring varied with the severity of consolidation considered to represent bovine respiratory disease.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine indications for cesarean section in alpacas and llamas, and clinical management and outcome of alpacas and llamas undergoing cesarean section.

Design—Retrospective case series.

Animals—27 alpacas and 7 llamas.

Procedures—Medical records were reviewed and information gathered on signalment, anamnesis including reproductive history, physical examination findings, indication for cesarean section, anesthetic protocol, surgical technique, number of crias delivered (alive or dead), additional treatment, duration of hospitalization, and postoperative complications. Follow-up information was gathered via email or telephone interview with owners.

Results—Uterine torsion (13/34 [38%]) was the most common reason for cesarean section. The most common surgical approach was the left proximal lateral abdominal approach (21/34 [62%]). Thirty-four crias were delivered via cesarean section. Twenty (59%) were born alive and discharged from the hospital. Retained placenta was the most common complication observed after surgery. A significant association was found between prolonged dystocia and fetal death. Of the 34 dams that underwent cesarean section, 21 were rebred, and 19 of the 21 (90.5%) dams that were rebred became pregnant. Fifteen of 19 dams were confirmed to have ≥ 1 normal vaginal delivery with a live cria following cesarean section.

Conclusions and Clinical Relevance—The results of the present study indicated that cesarean section was an effective method of resolving dystocia in camelids without negatively affecting future fertility or parturition by the dam. Prompt referral of patients with dystocia is advised to improve fetal viability. Retained fetal membranes seemed to be a common complication of cesarean section in camelids but was not associated with negative outcomes.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To compare the mechanical characteristics of polymerized caprolactam and monofilament nylon loops with those of the cranial cruciate ligament (CCL) in cattle.

Sample—6 femorotibial joints harvested from 3 cows and suture constructs made from No. 8 polymerized caprolactam, 80-lb test monofilament nylon fishing line, and 450-lb test monofilament nylon fishing line.

Procedures—Joints were cleared of soft tissue structures except the CCL, connected to a load frame, and loaded to failure while measuring force and elongation. Synthetic constructs tested in a similar manner included single-stranded and 3-stranded No. 8 polymerized caprolactam, 3- and 6-stranded 80-lb test monofilament nylon fishing line, and 3- and 6-stranded 450-lb test monofilament nylon fishing line.

Results—The CCL ruptured at a mean ± SD force of 4,541 ± 1,417 N with an elongation of 2.0 ± 0.3 cm. The tensile strength of 3-stranded 450-lb test monofilament nylon fishing line was similar to that of the CCL, rupturing at loads of 5,310 ± 369 N (braided strands) and 6,260 ± 239 N (parallel strands). Elongation was greater for braided constructs.

Conclusions and Clinical Relevance—The 3-stranded cords of 450-lb test monofilament nylon fishing line most closely approximated the strength of the CCL. Marked increases in elongation occur when large-sized materials are constructed in braided configurations, and this elongation would likely not provide stability in CCL-deficient stifle joints. Additional studies are needed to determine whether any of these materials are suitable CCL replacements in cattle.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the effects of orally administered phenylbutazone on proteoglycan synthesis and chondrocyte inhibition by IL-1β in articular cartilage explants of horses.

Animals—11 healthy 1- to 2-year-old horses.

Procedure—Horses were randomly assigned to the control (n = 5) or treated group (4.4 mg of phenylbutazone/ kg of body weight, PO, q 12 h; n = 6). Articular cartilage specimens were collected before treatment was initiated (day 0), after 14 days of treatment, and 2 weeks after cessation of treatment (day 30). Proteoglycan synthesis and stromelysin concentration in cartilage extracts were assessed after 72 hours of culture in medium alone or with recombinant human interleukin-1β (IL-1β; 0.1 ng/ml).

Results—On day 0, proteoglycan synthesis was significantly less in cartilage explants cultured in IL-1β, compared with medium alone. Mean proteoglycan synthesis in explants collected on days 14 and 30 was significantly less in treated horses, compared with controls. However, incubation of explants from treated horses with IL-1β did not result in a further decrease in proteoglycan synthesis. Significant differences in stromelysin concentration were not detected between or within groups.

Conclusions and Clinical Relevance—Oral administration of phenylbutazone for 14 days significantly decreased proteoglycan synthesis in articular culture explants from healthy horses to a degree similar to that induced by in vitro exposure to IL-1β. Phenylbutazone should be used judiciously in athletic horses with osteoarthritis, because chronic administration may suppress proteoglycan synthesis and potentiate cartilage damage. (Am J Vet Res 2001; 62:1916–1921)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the insulin response curve during IV glucose tolerance testing of mature Holstein bulls.

Animals—8 Holstein bulls between 5 and 8 years old and weighing between 911.5 and 1035.5 kg.

Procedure—A 50% glucose solution was rapidly administered IV so that each bull received a mean dose of 258 mg of glucose/kg of body weight. Serum glucose and insulin concentrations were determined before and 30, 60, 120, and 240 minutes after glucose infusion.

Results—Serum glucose concentrations 30 and 60 minutes after infusion were significantly greater than baseline concentration. Concentrations returned to baseline values 120 minutes after infusion. Serum insulin concentration was significantly greater 30 minutes after glucose administration, compared with baseline and 240-minute concentrations.

Conclusions and Clinical Relevance—Intravenous glucose tolerance testing of mature Holstein bulls resulted in a characteristic insulin response curve. Baseline and peak insulin concentrations were higher in these bulls, compared with values reported for mature Norwegian Red cows. (Am J Vet Res 2000; 61:61–63)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the usefulness of physiologic, behavioral, and pathological changes as objective indicators of early respiratory disease in calves with Mannheimia haemolytica pneumonia.

Animals—14 crossbred beef steers.

Procedures—Disease was experimentally induced in healthy calves through endoscopic pulmonary inoculation of M haemolytica. Calves were necropsied on days 1, 2, 3, 5, 7, and 9 after inoculation. Physical examination variables (rectal temperature, heart rate, and respiration characteristics), clinical illness score, and degree of activity were assessed 3 times daily beginning 4 days prior to inoculation and continuing throughout the study. Twice before inoculation and on days 1, 2, 3, 5, 7, and 9, arterial blood gas measurements, serum biochemical analyses, and CBCs were performed. Pedometers and accelerometers were used to monitor cattle behavior and activity throughout the trial.

Results—All calves became clinically ill after inoculation and had gross and histopathologic signs of bronchopneumonia. No variable was a reliable indicator of disease progression as judged by percentage of pulmonary involvement. However, activity as measured by total steps taken in a 24-hour period was lower after versus before disease induction.

Conclusions and Clinical Relevance—This single-pathogen challenge model successfully yielded clinical signs and pathological effects consistent with naturally acquired respiratory disease. Routine laboratory variables and subjective measures were not reliable indicators of lung involvement or the progression of pneumonia. However, activity, objectively measured with pedometers and accelerometers, appeared to be a promising indicator for early recognition of bovine respiratory disease.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To estimate intraocular pressure (IOP) in eyes of healthy camelids, using applanation tonometry.

Animals—The eyes of 34 camelids (16 llamas [Lama glama] and 18 alpacas [L pacos]) that did not have major abnormalities of the ocular surface or intraocular abnormalities.

Procedure—Tonometry measurements were obtained from each eye 3 times during a 24-hour period. Each measurement was the mean of several corneal applanations obtained by use of an applanation tonometer. Data were analyzed, using an ANOVA for a repeated-measures design.

Results—Mean (± SEM) IOP of llamas and alpacas was 13.10 ± 0.35 and 14.85 ± 0.45 mm Hg, respectively. Range of IOP was 7 to 18 mm Hg for llamas and 11 to 21 mm Hg for alpacas. Mean IOP of llamas was significantly less than the mean IOP of alpacas. Significant differences in IOP were not detected between the right and left eye of animals. Significant differences in IOP were not attributed to sex, age, or time of measurement within llamas or alpacas.

Conclusions and Clinical Relevance—Establishing the mean and range of IOP of clinically normal llamas and alpacas provides a frame of reference that is important for use in a complete ophthalmic examination of camelids, which can assist clinicians in the diagnosis of glaucoma and uveitis. Reasons for the difference in mean IOP between llamas and alpacas are unknown. Although the difference may be unimportant clinically, this finding reiterates the fact that caution must be used when extrapolating IOP among species. (Am J Vet Res 2000;61:1542–1544)

Full access
in American Journal of Veterinary Research