The effect of intra-articular methylprednisolone acetate and exercise on equine carpal subchondral and cancellous bone microhardness.

Dorsal carpal osteochondral injury is a major cause of lameness in horses undergoing high intensity training. Intra-articular corticosteroid treatment is used commonly to manage exercise-associated articular pain, but its use remains highly controversial in the equine athlete. This project, therefore, aimed to compare the mechanical properties of intra-articular MPA and diluent-treated middle carpal subchondral and cancellous bone in horses undergoing a short-term treadmill exercise programme. It was hypothesised that subchondral and cancellous bone mechanical properties are influenced by intra-articular administration of methylprednisolone acetate (MPA). Eight 2-year-old female horses had MPA or diluent administered into contralateral middle carpal joints at 14 day intervals, for a total of 4 treatments per horse. Horses underwent a standard treadmill exercise protocol until euthanasia (Day 70). Standard sites were located on the dorsal aspect of third, radial and intermediate carpal bones. Osteochondral samples from each test site were divided into subchondral bone and cancellous bone portions. These were dried, resin-embedded and gold-coated. Microhardness measurements were obtained at each test site. No significant effect of intra-articular treatment was detected. At each site, cancellous bone trabecular struts had an 18-19% higher microhardness value than the overlying subchondral bone. These findings indicate that intra-articular administration of MPA at this dose has no effect on subchondral or cancellous bone adaptation to short-term exercise and, therefore, on the propensity of carpal bones to injury. Further investigation into the calcified cartilage layer, effect of different corticosteroid preparations and diffusion of medication are required.

Purification of two equine pepsinogens by use of high-performance liquid chromatography.

OBJECTIVES: To purify and characterize pepsinogens in equine gastric mucosa. SAMPLE POPULATION: Stomachs collected from 2 healthy horses at necropsy. PROCEDURE: After collection, stomachs were placed immediately in ice before storage at -48 C. After slow thawing, the mucosa was scraped off while the tissue was immersed in 0.1M potassium phosphate (pH 7.4) at 4 C, then was homogenized. The filtered extract was subjected to anion-exchange chromatography. Fractions that were found to contain pepsin or pepsinogen were further chromatographed. Individual fractions were tested for pepsinogen or pepsin content by monitoring proteolytic activity at pH 2 and 3, respectively. Fractions from all columns were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to confirm molecular weight of pepsinogens and pepsin. RESULTS: Two pepsinogens and at least 1 pepsin were purified from equine gastric mucosa. CONCLUSIONS: On the basis of molecular mass, equine gastric mucosa contains 2 pepsinogens. CLINICAL RELEVANCE: Results of this study will enable future development of an ELISA or radioimmunoassay for use in the diagnosis of equine gastric ulceration.

Congenital dental disease of horses.

Equine congenital dental deformities are not limited merely to those presented here; however, the examples discussed offer the reader an appreciation for the range of severity and complexity that may be found in affected horses. The veterinarian is obligated to provide the best possible care for the patient and to relieve animal suffering. The lack of definitive evidence for heritability of many of these defects can place the veterinarian in an untenable position, particularly when presented with literature that proclaims or suggests without evidence that a particular condition is inherited. In such cases, the veterinarian is encouraged to counsel owners, citing substantiated medical information, and to recommend that owners make the decision to eliminate the affected animals' ability to reproduce.

The effects of intra-articular methylprednisolone and exercise on the mechanical properties of articular cartilage in the horse.

INTRODUCTION: Intra-articular corticosteroids are widely used as anti-inflammatory agents for symptomatic management of arthritis, but their administration with concurrent exercise remains controversial. Biochemical and morphologic analysis of treated cartilage has revealed conflicting results, but previous biomechanical assessment has not been undertaken. OBJECTIVE: To compare the biomechanical properties of intra-articular methylprednisolone acetate (MPA) and diluent treated cartilage in treadmill exercised horses. METHODS: Eight 2-year-old female horses had MPA or diluent administered into contralateral middle carpal joints at 14 day intervals for a total of four treatments per horse. Horses underwent a standard treadmill exercise protocol until euthanasia (day 70). Standard sites were tested on the third, radial and intermediate carpal bones using an automated indentation apparatus to obtain the creep and recovery behavior of the articular cartilage. Using previously validated biphasic creep indentation methodology, aggregate modulus, Poisson's ratio, permeability, shear modulus, thickness, creep and recovery equilibrium times and percent recovery were obtained at each site. Results were analyzed using ANOVA and multiple comparisons of the means (P < 0.05). RESULTS: Cartilage intrinsic material properties and thickness demonstrated significant differences between MPA and diluent treated joints. Diluent treated cartilage had a 97% increase in compressive stiffness modulus (P = 0.0001), was 121% more permeable (P = 0.0001), had 88% increase in shear modulus (P = 0.0001), and was 24% thicker (P = 0.0001) than MPA treated articular cartilage. CONCLUSIONS: The findings indicate that repetitive intra-articular administration of MPA to exercising horses alters the mechanical integrity of articular cartilage, which could lead to early cartilage degeneration.

Biomechanical comparison of the Herbert and AO cortical bone screws for compression of an equine third carpal bone dorsal plane slab osteotomy.

OBJECTIVE: To assess feasibility of insertion of 4.5-mm Herbert cannulated bone screws (HS) using fluoroscopic guidance and compare the mechanical shear strength of these HS and 4.5-mm AO cortical bone screws (AO) for fixation of dorsal plane slab osteotomies in equine cadaver third carpal bones (C3). ANIMALS OR SAMPLE POPULATION: Eight equine cadavers. METHODS: Bone mineral composition and density of contralateral C3 were confirmed to be equivalent using dual-energy x-ray absorptiometry. A standard 10-mm C3 slab osteotomy was reduced using HS or AO instrumentation under fluoroscopic guidance. Specimens were loaded in shear until failure, using a materials testing apparatus. RESULTS: HS and AO instrumentation allowed accurate reconstruction of the osteotomy, but there was difficulty encountered seating the HS proximal self-tapping threads. There was no significant difference in maximal load to failure, stiffness, or mode of failure of constructs created with the HS and AO screws. CONCLUSIONS: Use of 4.5-mm HS for repair of C3 radial facet, dorsal plane slab fractures may result in a mechanically comparable fixation to a repair using a 4.5-mm AO. Equine dorsal C3 may be too dense, however, to allow placement of the proximal self tapping threads of the HS without potentially excessive application of torque to the screw itself. CLINICAL RELEVANCE: Dorsal plane, radial facet slab fractures of the equine C3 are a significant clinical problem. Accurate reconstruction and stabilization are necessary for return to athletic function.

Characterization of anatomic communications of the fetlock in cattle, using intra-articular latex injection and positive-contrast arthrography.

OBJECTIVE: To evaluate the frequency and sites of communication between the lateral and medial synovial sacs of the metatarsophalangeal or metacarpophalangeal joints in cattle. ANIMALS: 188 limbs were obtained from 55 fresh bovine cadavers submitted for necropsy because of problems unrelated to the fetlocks. PROCEDURE: In each ox, lateral or medial synovial sacs of each fetlock were randomly assigned. Joints were injected with a mixture of latex and barium sulfate. Communication between 2 joints was determined by presence of latex and contrast material in a joint adjacent to the injected joint by examining frozen sections and use of positive-contrast arthrography. RESULTS: Communication between the 2 synovial sacs existed in 186 of 188 (98.9%) specimens. The communication site between lateral and medial synovial sacs was located at the level of the proximal sesamoid bones, between the distal aspect of the interdigital band of the axial branch of the interosseus muscle and the metacarpal or metatarsal bone. CONCLUSIONS AND CLINICAL RELEVANCE: Although communication between the lateral and medial synovial sacs did not exist in 2 specimens, the fetlock in cattle can be treated as 1 compartment.

Characterization of anatomic communications among the antebrachiocarpal, middle carpal, and carpometacarpal joints in cattle, using intra-articular latex, positive-contrast arthrography, and fluoroscopy.

OBJECTIVE: To evaluate the frequency and sites of communication among the antebrachiocarpal, middle carpal, and carpometacarpal joints in cattle. ANIMALS: 137 limbs were obtained from 72 fresh bovine cadavers submitted for necropsy because of problems unrelated to the carpus. PROCEDURE: 1 of the 3 injection sites was randomly assigned to both carpi of each ox, and a mixture of latex and barium sulfate was injected into the joint. Communication between 2 or more joints was determined by the presence of latex and contrast material in a joint adjacent to the injected joint by examination of frozen sections, positive-contrast arthrography, and fluoroscopy. RESULTS: Communication existed among the 3 joints in 18 specimens (13.1%). The middle carpal joint and the carpometacarpal joint always communicated. The antebrachiocarpal joint communicated with the middle carpal joint between the ulnar and intermediate carpal bones. The middle carpal and carpometacarpal joints always communicated between the fourth and fused second and third carpal bones. In a few specimens, additional sites of communication were identified at the palmar aspect of the fourth carpal bone and the fused second and third carpal bones. CONCLUSIONS AND CLINICAL RELEVANCE: Individual anatomic variation of the carpus in cattle should be considered when diagnostic or treatment protocols are established.

Improved osseointeraction of calcium phosphate-coated external fixation pins. Studies in calves.

We investigated osseointeraction of solution-precipitated calcium phosphate (SPCP)-coated transfixation pins used in external skeletal fixation of a calf stable fracture model. One group (SPCP) received centrally-threaded transfixation pins which had SPCP coating; the other group (control) received identical, but not coated, pins. Radiographs were obtained 1 and 40 days after surgery and examined for evidence of osteolysis. Bone phase 99mTc-MDP studies were performed 6 and 28 days after surgery. Calves were killed 40 days after surgery and mechanical tests performed. Dual-energy x-ray absorptiometry (DEXA) and histomorphometric analyses were done. A smaller proportion of SPCP pins (5/24) had evidence of discharge during the study compared with control pins (21/24). A smaller proportion of SPCP pins (4%) had radiographic evidence of osteolysis compared with control pins (42%). Uptake of 99mTc-MDP was similar for SPCP and control calves. Uptake was significantly greater in bone segments showing radiographic evidence of osteolysis than in bone segments not having osteolysis. Yield stress (MPa) for axial displacement was similar in the treatment groups. Bone mineral density was less in SPCP pins. Affinity index and interface histologic score were greater and osteoclastic index less in SPCP calves. Coating of transfixation pins with solution-precipitated calcium phosphate improved the osseointeraction of pin and bone during this 40-day study.

Characterization of anatomic communications between the femoropatellar joint and lateral and medial femorotibial joints in cattle, using intra-articular latex, positive contrast arthrography, and fluoroscopy.

OBJECTIVE: To evaluate the frequency of communication between the lateral and medial femorotibial joints and the femoropatellar joint in cattle. DESIGN: 1 of 3 injection sites was randomly assigned to each ox. ANIMALS: 102 limbs were obtained from 55 fresh bovine cadavers presented for necropsy with problems unrelated to the stifle. PROCEDURE: The joints were injected with a mixture of latex and barium sulfate. Communication between 2 or more joints was determined by the presence of latex and contrast material in a joint adjacent to the injected joint by examining frozen sections and positive-contrast arthrography. RESULTS: Communication between the 3 joints was present in 58 (56.9%) limbs. The femoropatellar and the medial femorotibial joints always communicated. Thirteen of 38 (34.2%) specimens injected in the lateral femorotibial joint did not communicate with the 2 other joints. The femoropatellar joint communicated with the lateral and medial femorotibial joints on the distal abaxial aspect of the trochlear ridge. CONCLUSION: Individual anatomic variation of the stifle in cattle should be considered when diagnostic or treatment protocols are established. CLINICAL RELEVANCE: The lateral femorotibial joint should be treated separately because it does not consistently communicate with the femoropatellar or medial femorotibial joint.

Application of a hook plate for management of equine ulnar fractures.

Closed fractures of the proximal aspect of the ulna were repaired in 10 horses younger than or equal to 6 months of age by application of a hook plate using a tension band principle. Ulnar fractures were classified as type 1A (2 horses), type 1B (4 horses), type 2 (1 horse), type 3 (1 horse), and type 4 (2 horses); all fractures had displacement of a proximal fragment. Complications were implant deformation (4 horses), screw pullout (1 horse), osseous sequestration (1 horse), ulnar fracture through a hole used to apply a tension device (1 horse), and metacarpophalangeal deformity associated with a displaced anconeal fragment (1 horse). Hook deformation was likely associated with failure to insert screws in all of the proximal holes of the plate and also in two horses, possibly with difficult recovery from anesthesia. Seven horses were discharged from the hospital and were being used for athletic activities. Insertion of the hook through the tendon of the triceps muscle and incorporation of the fragment within the hook can be used to effectively reduce and stabilize a fragment that might otherwise not hold screws.

Ovariohysterectomy in six mares.

Six mares had ovariohysterectomy performed for chronic pyometra associated with cervical abnormalities, uterine neoplasia, or removal of a macerated fetus. Ovariohysterectomy was performed through a ventral midline incision with access to the ovarian and uterine vessels aided by traction on the uterus and retraction of abdominal viscera. Abdominal pain, the most common complication after surgery, occurred in four mares but resolved within 36 hours. Peritonitis occurred in two mares; one mare was subsequently euthanatized. Other complications that resolved with treatment included infection of the uterine stump (two mares), abdominal hemorrhage (one mare), diarrhea (one mare), and incisional infection (one mare). Complications after surgery can be reduced by removing as much of the uterus as possible, minimizing peritoneal contamination with uterine contents, and providing a secure closure of the caudal reproductive tract.

Acute effects of perineural administration of sodium hyaluronate on palmar digital neurectomy sites in horses.

Biaxial palmar digital neurectomy of all limbs was performed on 6 mixed-breed castrated adult male horses, using a standard guillotine method. Using a Teflon catheter, 20 mg (2 ml) of sodium hyaluronate (group 1), 2 ml of phosphate-buffered saline solution (group 2), or catheter placement with no infusion (group 3) was applied to 4 (group 1) or 2 (groups 2 and 3) of 8 incisions/horse. Treatments were administered after closure of the neurectomy incision, and the catheter was removed. Horses were evaluated daily for 1 week, then weekly over a 9-week period for evidence of lameness, swelling, and ultrasonographic changes. On week 9, horses were euthanatized and neurectomy sites were removed en bloc for histologic evaluation of axonal regrowth, inflammation, and fibrosis. Neither lameness nor sign of painful neuroma was observed clinically in any of the horses. Neurectomy eliminated cutaneous heel sensation in all limbs for the duration of the study. Swelling was evident at all neurectomy sites. There were no significant differences between treatment sites for measurement of pastern circumference or ultrasonographic evaluation of incisional swelling. Foci of ultrasonographic hyperechogenicity increased over time, but there was no significant difference in hyperechogenicity between treatment groups. Histologic evidence of neuroma formation was observed at all sites. Morphometric assessment of neuroma cross-sectional areas revealed no significant difference between the groups, as did subjective histologic assessment of neuroma density and fibrous tissue content.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of chemical restraint on the endoscopic appearance of laryngeal and pharyngeal anatomy and sensation in adult cattle.

Effects of 2 drugs commonly used for chemical restraint of cattle were evaluated for their effect on laryngeal and pharyngeal anatomy, function, and response to stimuli. Eighteen adult Jersey cows, free of respiratory tract disease, were studied. Cows were assigned at random to 1 of 3 treatment groups. Endoscopic evaluations were performed before and at a predetermined time interval after administration of each drug. Responses to stimuli were evaluated by stimulating 7 preselected sites (epiglottis, left and right arytenoid cartilages, left and right vocal folds, and left and right dorsolateral pharyngeal walls) with a closed, transendoscopic biopsy probe. Xylazine HCl (0.05 mg/kg of body weight, i.v.) was administered to group-1 cows (n = 6), and endoscopy was repeated 5 minutes after administration of the drug. Xylazine (0.07 mg/kg, i.v.) was administered to group-2 cows (n = 6), and endoscopy was repeated 5 minutes after administration of the drug. Acepromazine maleate (0.035 mg/kg, i.v.) was administered to group-3 cows (n = 6), and endoscopy was repeated 10 minutes after administration of the drug. Responses to stimuli were scored as brisk (0), moderate (1), slow (2), and absent (3). Scores for responses to stimuli were compared, using the Wilcoxon signed-rank test for data within groups, and a general linear models procedure, using the Kruskal-Wallis test between groups. Interobserver agreement rates were generated for each group. A value of P < 0.05 was considered significant. Xylazine profoundly changed laryngeal sensitivity and function at both dosages. The corniculate processes of the arytenoid cartilages were observed to be in a markedly adducted position after sedation.(ABSTRACT TRUNCATED AT 250 WORDS)

Endoscopic evaluation of the nasopharynx, pharynx, and larynx of Jersey cows.

Endoscopy of the nasopharynx, pharynx, and larynx was performed in each of 25 adult Jersey cows, age and body weight of which ranged from 2 to 6 years and 300 to 365 kg, respectively. The endoscopic appearance of normal anatomic structures of the proximal portion of the airway were described. Observations specific to female dairy cattle were: the nasal septum, which tapered caudodorsally in the distal third of the nasal passage; the ability to observe both ethmoturbinates from the same viewing side; presence of a pharyngeal septum; the nasopharyngeal opening of the auditory tubes dorsolateral to the pharyngeal septum; and the appearance of the larynx--a triangular epiglottis with round borders and prominent corniculate process of the arytenoid cartilages. Tracheoscopy was performed in 13 cows. Of 11 cows for which the soft palate could be observed immediately after withdrawing the endoscope, 7 had dorsal displacement of the soft palate.

Persistent dorsal displacement of the soft palate in two young bulls.

Dorsal displacement of the soft palate was diagnosed by means of endoscopy and radiography in a 10-month-old Chianina/Angus bull and an 11-month-old Limousin bull. Both bulls produced respiratory noise that was audible in all phases of respiration. The Limousin bull also had exercise intolerance and became dyspneic when excited. The Chianina/Angus bull was treated with anti-inflammatory medication and rest. The respiratory noise resolved over a 4-month period, and the Chianina/Angus bull has been breeding successfully on pasture. Sternothyroideus and sternohyoideus myectomy was performed in the Limousin bull. Immediate postoperative improvement was noticed clinically and endoscopically. The bull had normal respiration 4 months after surgery and was successfully breeding on pasture. Although rare, dorsal displacement of the soft palate should be considered when evaluating cattle with respiratory noise or exercise intolerance.

Incarceration of the jejunum in the epiploic foramen of a four month old foal.

A 4-month Arabian filly presented for abdominal pain of 30 hours duration was found to have tachycardia, tachypnea, congested mucous membranes and gross abdominal distension. Further examination disclosed gastric reflux and small intestinal distension. Dehydration, prerenal azotemia, electrolyte abnormalities and metabolic alkalemia were observed. There was a progressive nonresponse to analgesic medication and deterioration in the foal's physiologic condition consistent with a small intestinal strangulating obstruction. Surgical exploration was declined. Necropsy examination revealed incarceration of the mid-jejunum in the epiploic foramen with proximal jejunal distension. This case is remarkable as the first report of entrapment of the jejunum in the epiploic foramen of a young foal.

Comparison of stainless steel fascial staples and polypropylene suture material for closure of the linea alba in dogs.

Five centimeter segments of the linea alba in mature, female, mixed breed dogs were incised and then approximated with either stainless steel fascial staples or size 0 polypropylene suture material. Breaking strength of the linea alba closures was determined at 0 (Phase I, 18 dogs) and at 7, 14, and 31 days (Phase II, 18 dogs). Histology and videointeractive planar morphometry were used to evaluate healing of the linea alba. Breaking strength and histologic and morphometric variables were analyzed statistically using analysis of variance in a split plot design. In a clinical trial, 20 cm linea alba incisions were approximated with stainless steel fascial staples after elective ovariohysterectomy in mature, female, mixed breed dogs (Phase III, eight dogs). The dogs were evaluated at 1, 2, 7, 14, 31, 90, and 180 days. Linea alba incisions approximated with polypropylene suture material were significantly stronger than linea alba incisions approximated with stainless steel fascial staples on day 0. There was no significant difference between breaking strength values, histologic, and morphometric appearance of linea alba incisions closed with stainless steel fascial staples or polypropylene suture material when compared 7, 14, and 31 days after surgery. All of the dogs in the clinical trial appeared to be normal at all evaluation times. Approximation of linea alba incisions with stainless steel fascial staples compares favorably to closure with a simple continuous pattern of polypropylene suture material with regard to breaking strength, clinical, histologic, and morphometric appearance.

Clinical and pathologic effects of a modified technique for application of spiral prostheses to the cervical trachea of dogs.

A modified surgical technique for application of extraluminal polypropylene spiral prostheses (PSP) to the trachea was developed. A portion of the segmental blood supply to the collapsed segment of trachea was maintained by fenestrating rather than completely dissecting the right lateral pedicle. Polypropylene spiral prostheses were applied to the cervical trachea of 12 dogs (group I) via the modified technique and to 12 dogs (group II) with the identical surgical dissection but without PSP applied. Clinical abnormalities included mild coughing in group I dogs and swelling of the incisions in both groups. Limited necrosis and moderate degeneration and inflammation were observed histologically in both groups. Pathologic changes were worse in the caudal cervical segment of the trachea. Mucosal regeneration was present on day 10 in both groups. Transmural tracheal necrosis was not observed. The modified technique for application of PSP is recommended by the authors because it provides adequate surgical exposure and the blood supply preserved by segmentally dissecting the right lateral pedicle is adequate to maintain tracheal viability.

Congenital diseases of the equine head.

Many questions concerning heritability arise when a veterinarian is asked to supervise and treat disease of congenital origin. Genetic counseling, ethics, and legality are often confronted in discussions between animal health professionals and laymen in animal industry. Guidelines have been offered as in the 1984 statement of the Judicial Council of the American Veterinary Medical Association: "Performance of surgical procedures in all species for the purpose of concealing genetic defects in animals to be shown, raced, bred, or sold as breeding animals is unethical. However, should the health or welfare of the individual patient require correction of such genetic defects, it is recommended that the patient be rendered incapable of reproduction." The Australian Veterinary Law, Ethics, Etiquette and Convention declares it fraud to alter a defect for sale purposes and unethical for a veterinarian to perform such treatments. It is permissible to correct defects causing discomfort or inconvenience, but the veterinarian is required to advise appropriate breeding counseling. Genetic counseling has progressed significantly in human medicine. This has been supported by better diagnostic methods for genetic disorders, greater acceptance of preventive measures, and extended screening programs to identify carriers of specific abnormal genes or chromosomal aberrations. Congenital diseases in veterinary medicine are constantly under investigation. The veterinary practitioner must continue to operate with an appreciation of the incomplete understanding of most of these abnormalities and act in accordance with personal ethical judgment and the guidance of the American Veterinary Medical Association when treating the affected individual animal patient.