Search Results

You are looking at 1 - 6 of 6 items for

  • Author or Editor: James T. Robertson x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract

Objective—To investigate the effect of laser shock peening on the fatigue life and surface characteristics of 3.5-mm-diameter cortical bone screws.

Sample Population—32 stainless steel, 3.5-mm-diameter cortical bone screws.

Procedure—Screws were randomly assigned to an untreated control group or 2 power-density treatment groups, 6 gigawatts (GW)/cm2 and 8.5 GW/cm2, for laser shock peening. Number of cycles to failure and findings on scanning electron microscopy-assisted morphometric evaluation, including the mode of failure, surface debris, surface damage, and thread deformation, were compared between control and treated screws.

Results—The 6 GW/cm2 treated screws had a significant (11%) improvement in fatigue life, compared with untreated control screws. The 8.5 GW/cm2 treated screws had a significant (20%) decrease in fatigue life, compared with control screws. A mild but significant increase in thread deformation was evident in all treated screws, compared with control screws. The 8.5 GW/cm2 treated screws had significantly more surface irregularities (elevations and pits), compared with control or 6 GW/cm2 treated screws.

Conclusions and Clinical Relevance—A modest positive increase in fatigue strength was produced by this design of laser shock peening on the midshaft of cortical bone screws. High laser shock peening power densities were detrimental, decreasing screw fatigue strength probably resulting from structural damage. Greater fatigue life of cortical bone screws can be generated with laser shock peening and could reduce screw breakage as a cause of implant failure; however, future studies will be necessary to address biocompatibility, alternative cleaning techniques, alterations in screw strength and pullout characteristics, and effects on susceptibility to corrosion. ( Am J Vet Res 2004;65:972–976)

Restricted access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate use of kinetic gait analysis for detection, quantification, and differentiation of hind limb lameness and spinal ataxia in horses.

Design—Prospective clinical study.

Animals—36 horses.

Procedures—Kinetic gait analysis with a force plate was performed for 12 clinically normal horses, 12 horses with hind limb lameness, and 12 horses with spinal ataxia. Kinetic variables were compared among groups, correlated to subjective grading, and used to build predictive models to assess the accuracy of discrimination.

Results—Subsets of kinetic variables were characteristically altered in ataxic and lame gaits. Ataxic horses had significantly increased lateral force peak and variation in vertical force peaks in both hind limbs. Lame horses had significantly decreased vertical force peak and increased variation in vertical force peaks only in the lame hind limb. These variables were used to differentiate between spinal ataxia and hind limb lameness with excellent accuracy. There were significant correlations between a subset of kinetic variables and subjective lameness and neurologic grades.

Conclusions and Clinical Relevance—Kinetic gait variables, specifically lateral force peak and the variation in vertical force, can be used to support the differential diagnosis between spinal ataxia and hind limb lameness in horses. Kinetic gait analysis may also be applied for quantification of equine hind limb gait abnormalities as well as confirming lack of lameness and ataxia in soundness examinations.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine survival rate and athletic ability after nonsurgical or surgical treatment of cleft palate in horses.

Design—Retrospective case series.

Animals—55 horses with cleft palate.

Procedures—13 of the 55 horses died or were euthanized without treatment and were not included in all analyses. Medical records were reviewed for signalment, history, method of diagnosis, soft or hard palate involvement, type of surgical procedure performed, postoperative complications, and survival to hospital discharge. Information on athletic ability was acquired from race records and follow-up conversations with owners, trainers, or referring veterinarians.

Results—The predominant reason for initial evaluation was milk or feed in the nostrils (60%). The diagnosis was confirmed by means of videoendoscopy of the upper portion of the airway in all cases. Most cases involved the soft palate only (92.7%). Twenty-six of the 55 (47.3%) horses underwent surgical repair, and 12 of these had dehiscence at the caudal edge of the soft palate. Among potential racehorses, 14 of 33 had surgery. Of these, 12 of 14 survived to discharge and 2 horses raced. Among potential racehorses, 10 of 33 were discharged without surgery and 2 of these raced. Among nonracehorses, 12 of 22 underwent surgery and 11 survived to discharge. All horses that were discharged and for which follow-up information was available survived to 2 years of age or older without ill thrift despite dehiscence at the caudal edge of the soft palate and continued mild nasal discharge.

Conclusions and Clinical Relevance—Horses with cleft palate had a higher survival rate than previously reported.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate anesthetic effects of 4 drug combinations used for total intravenous anesthesia of horses undergoing surgical removal of an abdominal testis.

Design—Clinical trial.

Animals—32 healthy cryptorchid horses.

Procedure—Horses were sedated with xylazine and butorphanol and were randomly assigned to 1 of 4 groups: induction of anesthesia with ketamine and diazepam and maintenance with bolus administration of ketamine and xylazine (KD/KX); induction and maintenance of anesthesia with bolus administration of tiletamine-zolazepam, ketamine, and detomidine (TKD); induction and maintenance of anesthesia with continuous infusion of xylazine, guaifenesin, and ketamine; and induction and maintenance of anesthesia with continuous infusion of guaifenesin and thiopental. Horses that moved 3 consecutive times in response to surgical stimulation or for which surgery time was > 60 minutes were administered an inhalant anesthetic, and data from these horses were excluded from analysis.

Results—Quality of induction was not significantly different among groups. Muscle relaxation and analgesia scores were lowest for horses given KD/KX, but significant differences among groups were not detected. Horses anesthetized with TKD had a significantly greater number of attempts to stand, compared with the other groups, and mean quality of recovery from anesthesia for horses in the TKD group was significantly worse than for the other groups. Anesthesia, surgery, and recovery times were not significantly different among groups.

Conclusions and Clinical Relevance—Results suggest that all 4 drug combinations can be used to induce short-term anesthesia for abdominal cryptorchidectomy in horses. However, horses receiving TKD had a poorer recovery from anesthesia, often requiring assistance to stand. (J Am Vet Med Assoc 2000;217:869–873)

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the anesthetic, cardiorespiratory, and metabolic effects of 4 IV anesthetic regimens in Thoroughbred horses recuperating from a brief period of maximal exercise.

Animals—6 adult Thoroughbreds.

Procedure—Horses were preconditioned by exercising them on a treadmill. Each horse ran 4 simulated races, with a minimum of 14 days between races. Races were run at a treadmill speed that caused horses to exercise at 120% of their maximal oxygen consumption. Horses ran until fatigued or for a maximum of 2 minutes. Two minutes after exercise, horses received a combination of xylazine hydrochloride (2.2 mg/kg of body weight) and acepromazine maleate (0.04 mg/kg) IV. Five minutes after exercise, horses received 1 of the following 4 IV anesthetic regimens: ketamine hydrochloride (2.2 mg/kg); ketamine (2.2 mg/kg) and diazepam (0.1 mg/kg); tiletamine hydrochloride-zolazepam hydrochloride (1 mg/kg); and guaifenesin (50 mg/kg) and thiopental sodium (5 mg/kg). Treatments were randomized. Cardiopulmonary indices were measured, and samples of blood were collected before and at specific times for 90 minutes after each race.

Results—Each regimen induced lateral recumbency. The quality of induction and anesthesia after ketamine administration was significantly worse than after other regimens, and the duration of anesthesia was significantly shorter. Time to lateral recumbency was significantly longer after ketamine or guaifenesinthiopental administration than after ketaminediazepam or tiletamine-zolazepam administration. Arterial blood pressures after guaifenesin-thiopental administration were significantly lower than after the other regimens.

Conclusions and Clinical Relevance—Anesthesia can be safely induced in sedated horses immediately after maximal exercise. Ketamine-diazepam and tiletamine- zolazepam induced good quality anesthesia with acceptable perturbations in cardiopulmonary and metabolic indices. Ketamine alone and guaifenesinthiopental regimens are not recommended. (Am J Vet Res 2000;61:1545–1552)

Restricted access
in American Journal of Veterinary Research