Dennis M. Meagher

Pathologic findings and pathogenesis of racetrack injuries.

Many lesions of the musculoskeletal system of racing horses are either acute traumatic lesions or are chronic biomechanically induced lesions that become suddenly unstable and provoke acute clinical signs. The latter lesions along with those of DJD are much more common and are of much greater overall economic importance to the racing industry than are the acute traumatic injuries. Chronic biomechanical lesions occur at predictable sites and are the result of an imbalance between repetitive microtrauma sustained in athletic performance and adaptive repair mechanisms of skeletal tissues. The distribution of these lesions in the limbs reflects the patterns of biomechanical forces placed on the skeleton during work at racing speeds and, therefore, reflects the type of racing activity for which the horse was bred. Lesions result when there is a failure of the stressed skeletal structures to adapt to the biomechanical forces placed upon them. Rest or a reduction in the level of training activity permit the healing of many asymptomatic and presumably some symptomatic lesions of the bony tissues. Articular cartilage, tendons, and ligaments have a lower capacity to resolve the damage and return to normal structure and function.

Pathophysiology of Navicular Syndrome

Navicular syndrome is a degenerative disorder of the distal half of the flexor surface of the proximal sesamoid bone that is predisposed by faulty foot conformation. In horses that become symptomatic, the faulty conformation results in sustained application of nonphysiologic pressure by the deep digital flexor tendon against the flexor cortex of the bone. This force stimulates an intense bone remodeling response in order to attenuate the pressure. An unfortunate sequela of this response is active hyperemia and edema formation in the medullary cavity of the bone. The edema is organized by fibrous tissue resulting in venous entrapment, venous hypertension, vascular bone pain, and the onset of clinical signs.

STRESS FRACTURES OF THE HUMERUS, RADIUS, AND TIBIA IN HORSES

The medical records, radiographic and nuclear scintigraphic findings of 26 racing horses with 27 stress fracture episodes of the humerus, radius, or tibia were reviewed. The purposes of this study were to describe the radiographic and/or scintigraphic features of stress fractures of the humerus, radius, or tibia, and to evaluate the signalment and history of horses in which stress fracture occurred. Stress fractures of the three long bones examined were primarily seen in 2-and 3-year-old male Thoroughbred horses; commonly, the onset of lameness was immediately following training gallops or racing. There were 13 humeral stress fracture episodes in 12 horses. Ten were in the proximal caudolateral cortex, and three were in the distal craniomedial cortex. Radial stress fractures were seen in three horses, all in the midshaft radius. Tibial stress fractures were diagnosed in 11 horses. They were located in the proximal lateral tibia in six horses, the distal caudolateral tibia in three horses, and the midshaft tibia in three horses. Fifteen stress fractures were diagnosed with radiographs alone, one was diagnosed with scintigraphy alone, nine were diagnosed with radiographs and scintigraphy, and, in two horses, radiographs were negative, but the scintigraphic findings were consistent with stress fracture.

Perioperative medical care for equine abdominal surgery.

Rational perioperative management improves the success rate of abdominal surgery. Important aspects of management are discussed, including principles of fluid therapy, nutrition, intravenous catheterization, antimicrobial prophylaxis, and the use of nonsteroidal anti-inflammatory medication. Current advances in the area of immunotherapy are mentioned.

Prevalence of abnormal radiographic findings in 2-year-old Thoroughbreds at in-training sales and associations with racing performance

OBJECTIVE To estimate the prevalence of radiographic abnormalities (lesions) in Thoroughbred racehorses at 2-year-old in-training sales and determine whether these lesions and 1-furlong presale workout times were associated with subsequent racing performance. DESIGN Retrospective cohort study. ANIMALS 953 Thoroughbreds. PROCEDURES Repository radiographs of carpal, metacarpophalangeal and metatarsophalangeal (fetlock), stifle, and tarsal (hock) joints were examined. Horses with lesions were classified by lesion type and location. Race performance variables were compared between horses with and without lesions and between horses categorized by 1-furlong presale workout times (< or ≥ 11 seconds). RESULTS 299 horses had ≥ 1 lesion, and 654 had no lesion detected. Odds of starting a race and of earning money racing were lower for horses with any lesion and lower for horses with proximal phalangeal dorsoproximal articular margin chip fracture, proximal sesamoid bone fracture or sesamoiditis, or wedge-shaped central or third tarsal bones, compared with horses that had no lesion. For horses that raced, proximal phalangeal dorsoproximal articular margin chip fractures were associated with lower lifetime earnings, and flattening of the medial femoral condyle was associated with fewer 3-year-old racing starts, compared with values for horses that had no lesion. Horses with workout times < 11 seconds had greater odds of having lifetime starts, lifetime earnings, and maximum purse above threshold (median) values than did horses with slower workout times. CONCLUSIONS AND CLINICAL RELEVANCE No radiographic lesions prevented all affected horses from racing. Among horses that raced, few differences were found in performance for horses with and without lesions.

Lag screw fixation of a sagittal fracture of the talus in the horse

Summary This is a report of the surgical technique used to repair a non-displaced, complete sagittal fracture of the talus in a horse utilizing lag screw compression. A review of tarsal fractures in horses along with the history, clinical signs, and diagnostic workup which led to the diagnosis of a previously unreported type of tarsal fracture is presented. The horse presented in this report, returned to race successfully but at a lower level of competition.

FOREIGN BODY OBSTRUCTION IN THE CERVICAL ESOPHAGUS OF THE HORSE: A CASE REPORT

Summary Two cases of wood obstruction of the cervical esophagus are presented. The literature on esophageal surgery in the horse is reviewed. The diagnostic workup, medical and surgical management of the 2 cases is presented. Surgical removal of the obstruction was successful in each case. Healing of the incisions was by first intention and both horses returned to a normal hay and pasture diet without signs of “choke.”