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Abstract

OBJECTIVE To determine the effects of racetrack surface and shoe characteristics on formation of wear grooves in the horseshoes of racehorses.

SAMPLES 1,121 horseshoes from 242 Thoroughbred racehorses collected during routine horseshoeing procedures at 4 racetracks with dirt or synthetic surfaces.

PROCEDURES Data for 1,014 horseshoes from 233 racehorses were analyzed. Horseshoes were photographed, and length and width of grooves formed at the heels of the solar surface of horseshoes were measured on the photographs. Effects of racetrack, racetrack surface, and shoe characteristics (eg, shoe size, clips, and nails) on length and width of grooves were assessed by use of a mixed-model anova.

RESULTS Length and width of wear grooves differed significantly on the basis of racetrack, nail placement, and limb side (left vs right). Differences in groove dimensions between types of racetrack surface (dirt vs synthetic) were less apparent than differences among racetracks.

CONCLUSIONS AND CLINICAL RELEVANCE Measurements of the length and width of wear grooves in the horseshoes of racehorses may be useful for understanding some aspects of hoof interactions with various racetrack surfaces. Interpretation of differences in wear grooves for various racetrack surfaces will likely require quantitation of the mechanical behavior of the surfaces.

Full access
in American Journal of Veterinary Research

Abstract

Objectives

To test whether femoral ostectomy level, subtrochanteric bone mass removal, and stem-size selection significantly affect stem positioning in canine total hip replacement, and to determine ability of the femoral stem component to restore geometry of the normal femoral head and neck.

Sample Population

Femurs from 8 adult mixed-breed canine cadavers.

Procedure

Femurs were systematically prepared, using 8 combinations of 3 surgical preparation techniques that included level of ostectomy (cervical isthmus vs lesser trochanter), subtrochanteric bone block removal, and femoral stem size (recommended, undersized). Computer-aided analysis of specimen photographs was used to evaluate femoral head offset and position and variability of femoral stem positioning for each of the preparation combinations.

Results

Original femoral head offset and position were reconstructed to within a mean of 0.052 and 0.031 cm, respectively, using an undersized femoral stem after ostectomy at the level of the lesser trochanter. Implantation of an undersized femoral stem after subtrochanteric bone block removal improved ability to centralize the distal tip of the implant and reduce the angle between the femoral diaphyseal and implant axes. Ostectomy at the level of the cervical isthmus tended to force femoral implants into a varus position, and ostectomy at the level of the lesser trochanter tended to force implants into a valgus position.

Conclusions

Geometry of normal canine femurs was most closely reconstructed by implantation of an undersized femoral component after ostectomy at the level of the lesser trochanter. Implantation of an undersized femoral component after subtrochanteric bone block removal resulted in the best alignment and centralization of the stem. (Am J Vet Res 1998;59:1071–1079)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To describe the prevalence, characteristics, and severity of soft-tissue and osseous lesions in the caudal portion of the thoracic and lumbosacral vertebral column and pelvis in Thoroughbred racehorses.

Animals

36 Thoroughbred racehorses that died or were euthanatized at California racetracks between October 1993 and July 1994.

Procedure

Lumbosacral and pelvic specimens were collected and visually examined for soft-tissue and osseous lesions.

Results

Acute sacroiliac joint injury was observed in 2 specimens. Signs of chronic laxity or subluxation of the sacroiliac joint were not observed in any specimens. Impingement of the dorsal spinous processes and transverse processes was observed in 92 and 97% of specimens, respectively. Thoracolumbar articular processes had variable degrees of degenerative change in 97% of specimens. Degenerative changes were observed at lumbar intertransverse joints and sacroiliac articulations in all specimens. Some degenerative changes were widespread and severe.

Conclusions

Numerous degenerative changes affected vertebral processes, intervertebral articulations, and sacroiliac joints in these Thoroughbred racehorses.

Clinical Relevance

Various types of vertebral and pelvic lesions need to be considered during clinical evaluation of the back and pelvis in horses. Undiagnosed vertebral or pelvic lesions could be an important contributor to poor performance and lameness in athletic horses. (Am J Vet Res 1999:60:143-153).

Free access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate the effect of premature closure of the pubic symphysis on pelvic development.

Animals

18, 21-day-old male guinea pigs.

Procedure

The pubic symphysis was surgically approached in 10 guinea pigs of the symphysiodesis group and in 4 of the sham-operated group; 4 guinea pigs served as unoperated controls. The pubic symphysis was destroyed by use of electrocautery in the 10 guinea pigs of the symphysiodesis group. All guinea pigs were allowed to grow to skeletal maturity and were euthanatized at 33 weeks of age. Body weight was recorded throughout the study and was compared between groups. Histologic examination of the symphyses confirmed premature closure of the pubic symphyseal growth plates in guinea pigs of the symphysiodesis group. Pelvic measurements taken from pretreatment radiographic views and from video images of harvested pelves were compared between groups.

Results

There were no significant differences between groups with regard to pretreatment radiographic variables, rate of weight gain, or body weight at any time. Pubic symphysiodesis resulted in significant narrowing of the caudal aspect of the pelvis, narrowing and shortening of the pubic bones, and outward rotation of the acetabula.

Conclusions

The pubic symphyseal growth plates contribute significantly to development of the pelvis. Premature closure of these growth plates (pubic symphysiodesis) results in outward rotation of the acetabula, which might be beneficial in some cases of canine hip dysplasia; however, this rotation is accompanied by concomitant narrowing pf the caudal aspect of the pelvis. (Am J Vet Res 1996;57:1427-1433)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To describe the incidence and types of gross osseous developmental variations and ages of physeal closure in the caudal portion of the thoracic and lumbosacral spine and the pelvis in a sample of Thoroughbred racehorses.

Animals

Thoroughbred racehorses (n = 36) that died or were euthanatized at California racetracks between October 1993 and July 1994.

Procedure

Lumbosacropelvic specimens were collected, and all soft tissues were removed. The osseous specimens were visually examined.

Results

Only 22 (61 %) specimens had the expected number of 6 lumbar and 5 sacral vertebrae. Eight (22%) specimens had thoracolumbar transitional vertebrae, and 13 (36%) had sacrocaudal transitional vertebrae. Articular process asymmetries were present at 1 or more vertebral segments in 30 (83%) specimens. Intertransverse joints (2 to 4 pairs/specimen) were bilaterally distributed in the caudal portion of the lumbar spine and the lumbosacral joint in 31 (86%) specimens. Five (14%) specimens had asymmetric distribution of the intertransverse joints. Intertransverse joint ankylosis was found in 10 (28%) specimens. Lumbosacral vertebral body physeal closure occurred between 4.9 and 6.7 years of age; pelvic physeal closure occurred between 5.2 and 5.8 years of age. Iliac crest and ischial arch epiphyseal formation was evaluated, using a grading system, and fusion to the underlying bone occurred at 7.2 years and 5.4 years of age, respectively.

Conclusions

Numerous vertebral anatomic variations were commonly found in a sample of Thoroughbred racehorses.

Clinical Relevance

Normal anatomic variations and ages of skeletal maturity need to be considered in clinical evaluation of the equine spine and pelvis for differentiation from pathologic findings. (Am J Vet Res 1997;58:1083–1091)

Free access
in American Journal of Veterinary Research

Summary

The metabolic responses of equine articular cartilage to incubation with bacterial lipopolysaccharide (lps) were studied, using explant cultures of articular cartilage obtained from the metatarsophalangeal joints of 15 horses, age of which ranged from 3 months to 20 years. For comparison, explants were also established from the metatarsophalangeal joints of 3 calves. Explants were cultured for 3 days in medium containing various concentrations of lps from 0 (control) to 100 μg/ml. Glycosaminoglycan (gag) released during the 3-day incubation was determined by a spectrophotometric assay, using the dye 1,9-di-methylmethylene blue. Newly synthesized gag content was assayed by measuring [35S]sulfate incorporation during a 3-hour pulse labeling period. In addition, prostaglandin E2 (pge 2) synthesis was quantified, using a [3H]pge 2 radioimmunoassay kit and magnetic separation. Finally, explants from 3 animals were used to evaluate the effect of supplementing culture medium with 5% serum on the response of explants to lps, and explants from 1 horse were used to compare responses to stimulation with lps derived from 2 bacterial sources.

Equine explants cultured with bacterial lps had a dose-dependent decrease in synthesis and increase in release of gag, and these responses were significantly (P < 0.0001) greater in explants from younger horses. In addition, equine explants had a significant (P = 0.0001) dose-dependent increase in concentration of pge 2 released into the culture medium in response to incubation with lps.

Comparison of data for gag synthesis from equine and bovine explants revealed a significant (P = 0.025) difference in responsiveness to lps between the 2 species. Equine explants tended to have a greater suppression of gag synthesis in response to incubation with increasing concentrations of lps than did age-corrected bovine samples. However, similar analysis of data on gag release did not indicate any difference in sensitivity between the 2 species for this response. There was no evidence that the presence or absence of serum supplementation or the use of lps derived from different bacterial sources made a significant difference in the response of explants to incubation with lps.

Free access
in American Journal of Veterinary Research

Summary

Explant cultures were set up, using articular cartilage obtained from metatarsophalangeal joints of 11 horses. Explants from 2 horses were used to determine culture conditions appropriate for tissue viability. The cartilage explants maintained steady-state metabolism of proteoglycans during a 13-day evaluation period. The metabolic response of equine articular cartilage to incubation with recombinant human interleukin 1 (0.01 to 100 ng/ml) was studied, using cartilage obtained from the remaining 9 horses, age of which ranged from 3 months to 20 years. Interleukin 1 induced a dose-dependent release of glycosaminoglycan from the matrix during a 3-day incubation period. It also caused dose-dependent inhibition of glycosaminoglycan synthesis during a 3-hour pulse-labeling period. Expiants obtained from older horses were significantly (P < 0.05) less responsive to interleukin 1, with respect to synthesis and release of glycosaminoglycan.

Free access
in American Journal of Veterinary Research

SUMMARY

Chemical and cytologic effects and bactericidal activity of gentamicin in septic synovial fluid were evaluated in an experimental model of infectious arthritis in horses. Septic arthritis was induced by inoculation of approximately 7.5 × 106 colony-forming units of Escherichia coli into 1 antebrachiocarpal joint in each of 16 clinically normal adult horses. Clinical signs of septic arthritis were evident 24 hours after inoculation. Horses were allotted to 3 groups: group-1 horses (n = 5) each were given 150 mg of gentamicin (50 mg/ml; 3 ml) intra-articularly (ia); group-2 horses (n = 5) each were given 2.2 mg of gentamicin/kg of body weight, iv, every 6 hours; and group-3 horses (n = 6) each were given buffered gentamicin, consisting of 3 mEq of sodium bicarbonate (1 mEq/ml; 3 ml) and 150 mg of gentamicin (50 mg/ml; 3 ml), ia. Synovial fluid specimens were obtained at posttreatment hour (pth) 0, 0.25, 1, 4, 8, 12, and 24 via an indwelling intra-articular catheter. Synovial fluid pH was evaluated at pth 0, 0.25, and 24. Microbiologic culture and cytologic examination were performed on synovial fluid specimens obtained at pth 0 and 24, and gentamicin concentration was measured in all synovial fluid specimens.

At pth 0, E coli was isolated from synovial fluid specimens obtained from all horses. Synovial fluid pH was lower (range, 7.08 to 7.16) and wbc count was higher (range, 88,000 to 227,200 cells/μl) and predominantly neutrophilic (95 to 99%) at pth 0 than before inoculation. Synovial fluid pH was lowered further (mean, pH 6.63) after ia administration of gentamicin in group-1 horses; mean pH remained unchanged (7.07) after buffered-gentamicin administration in group-3 horses. At pth 0.25, mean peak synovial fluid gentamicin concentration in horses of groups 1 and 3 (4,745 and 6,190 μg/ml, respectively) was 1,000 times greater than that in group-2 horses (5.1 μg/ml) at the same time. Synovial fluid gentamicin concentration in group-1 and group-3 horses was always greater than that in group-2 horses and remained greater than a minimal inhibitory concentration of gentamicin (2 μg/ml) against many common equine bacterial pathogens for at least 24 hours after injection. Further, the calculated apparent half-life and clearance of gentamicin in synovial fluid calculated after ia administration were similar in horses of groups 1 and 3. By pth 24, E coli could not be isolated from synovial fluid specimens obtained from group-1 horses. However, moderate to heavy growth of E coli was isolated from synovial fluid specimens obtained at pth 24 from horses in groups 2 and 3 (80 and 66%, respectively).

In selected cases, ia administration of unbuffered gentamicin may be a useful supplement to drainage, lavage, and systemic antibacterial and anti-inflammatory treatment in horses with naturally acquired infectious arthritis.

Free access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To compare the biomechanical behavior of mandibular critical-sized defects stabilized with 2 plating configurations under in vitro conditions resembling clinical situations.

SAMPLE 24 mandibles harvested from 12 adult canine cadavers.

PROCEDURES 8 mandibles were kept intact as control samples. A critical-sized defect was created in 16 mandibles; these mandibles were stabilized by use of a single locking plate (LP [n = 8]) or an LP combined with an alveolar miniplate (LMP [8]). Mandibles were loaded in cantilever bending in a single-load-to-failure test with simultaneous recording of load and actuator displacement. Stiffness, yield, and failure properties were compared among groups. Mode of failure was recorded. Radiographic evidence of tooth root and mandibular canal damage was quantified and compared between groups.

RESULTS Stiffness and yield loads of single LP and LMP constructs were < 30% of values for intact mandibles, and failure loads were < 45% of values for intact mandibles. There were no consistent biomechanical differences at failure between single LP and LMP constructs, but the LMP construct had greater stiffness and strength prior to yield. Frequency of screw penetration of teeth and the mandibular canal was significantly greater for LMP than for single LP constructs.

CONCLUSIONS AND CLINICAL RELEVANCE Both fixation methods were mechanically inferior to an intact mandible. The LMP construct was mechanically stronger than the LP construct but may not be clinically justifiable. Addition of an alveolar miniplate provided additional strength to the construct but resulted in more frequent penetration of tooth roots and the mandibular canal.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To define scintigraphic, physical examination, and scapular ultrasonographic findings consistent with bone fragility syndrome (BFS) in horses; develop indices of BFS severity; and assess accuracy of physical examination, scapular ultrasonography, and serum biomarkers for BFS diagnosis.

Design—Prospective case-control study.

Animals—48 horses (20 horses with BFS and 28 control horses).

Procedures—Horses underwent forelimb scintigraphic evaluation, physical examination, scapular ultrasonography, and serum collection. Scintigraphy was used as a reference standard to which physical examination, scapular ultrasonography, and concentrations of serum biomarkers (carboxy-terminal telopeptide of collagen crosslinks and bone-specific alkaline phosphatase activity) were compared for assessing accuracy in BFS diagnosis.

Results—A diagnosis of BFS was strongly supported on scintigraphy by ≥ 2 regions of increased radiopharmaceutical uptake, including 1 region in the scapular spine and 1 region in the scapular body or ribs; on physical examination by lateral bowing of the scapulae; and on ultrasonography by widening of the scapular spine. None of the tests evaluated were accurate enough to replace scintigraphy for mild disease; however, physical examination and scapular ultrasonography were accurate in horses with moderate to severe BFS. Serum biomarkers were not accurate for BFS diagnosis.

Conclusions and Clinical Relevance—Scintigraphy remained the most informative diagnostic modality for BFS, providing insight into disease severity and distribution; however, physical examination and scapular ultrasonographic abnormalities were diagnostic in horses with moderate to severe disease. Proposed severity indices classified the spectrum of disease manifestations. Clearly defined criteria for interpretation of diagnostic tests aid in the detection of BFS. Severity indices may be useful for assessing disease progression and response to treatment.

Full access
in Journal of the American Veterinary Medical Association