RADIOGRAPHIC CHANGES IN AN EQUINE PATELLA FOLLOWING MEDIAL PATELLAR DESMOTOMY

Medial patellar desmotomy has been considered a benign surgical treatment in horses with suspected upward fixation of the patella. Our clinic has previously observed radiographic changes in the equine stifle following medial patellar desmotomy but preoperative radiographs were not made and the changes therefore could not be directly associated with the desmotomy. In this report we describe a case with normal stifle radiographs before medial patellar desmotomy. Radiographs made 3 months later demonstrated degeneration of the patella with enthesophytes, osteolysis and bone fragments. It is hypothesized that the lesion developed as a result of lateral rotation of the patella creating stress concentration in the subchondral bone of the distal articular surface of the patella. The pathogenesis of the patellar lesion is thought to be similar to the "gull wing" lesion on the distal palmar aspect of the third metacarpal bone. We recommend a more prudent approach to medial patellar desmotomy in the horse.     

FAT OPACITIES DORSAL TO THE EQUINE ANTEBRACHIOCARPAL JOINT

Radiolucencies due to fat in the soft tissues dorsal to the equine antebrachiocarpal joint were studied in 12 necropsy specimens. In lateral-to-medial xeroradiographs of these 12 specimens, focal radiolucencies were present in ten, one focal radiolucency was present in one, and no focal radiolucencies were present in ten, one focal radiolucency was present in one, and no focal radiolucencies were in another. These radiolucencies were identified as fat in the antebrachiocarpal joint capsule. The fat was in two locations within this joint capsule. It was associated with the synovial membrane of the extensor carpi radialis tendon sheath and the synovial membrane of the antebrachiocarpal joint.     

Muscle fatigue in the horse: A review

The onset of fatigue within a muscle depends on several factors, including the duration or intensity of work and amount of training. In aerobic work over prolonged time it appears to be the level of glycogen stored within the muscle fibers that becomes limiting. In anaerobic work the limiting factor may be a combination of the amount of substrate available to the cell and the ability of the cell to continue working at low pH. Further work is needed to establish which is the most limiting of these two factors, levels of stored glycogen or accumulating levels of lactate and concomitant lowering of muscle pH.     

RADIOGRAPHIC AND MYELOGRAPHIC EXAMINATION OF THE CERVICAL VERTEBRAL COLUMN IN 306 ATAXIC HORSES

This study consists of a review of 306 ataxic horses subjected to survey radiography and myelography of the cervical vertebral column. Fifty-eight percent of horses had evidence of compressive spinal cord lesion on myelography. Sixty-six percent of horses were less than 3 years old. Age had no effect on the distribution of spinal cord compressive lesions. No conclusion could be drawn from sex and breed distribution. The most common sites of cord compression on myelography in order of decreasing frequency were C_3–4, C_6–7, C_5–6, and C_4–5. Twenty-nine percent of horses with myelographic evidence of cord compression had multiple compressive sites. Survey radiographs were not reliable to diagnose compressive spinal cord lesions. Myelography was a safe and more accurate procedure. Several factors may result in misinterpretation of the myelographic examination.     

Generation of Airborne Particles from Different Bedding Materials Used for Horse Keeping

Among other factors (eg, feed), bedding material has an important effect on stable air quality with respect to airborne particle formation. This study was designed to establish which material is suited to create an improved stable environment for horses. First, the following materials were analyzed under standardized conditions in a laboratory experiment: wheat straw, dry wood shavings, hemp shives, linen shives, wheat straw pellets, paper cuttings (unprinted newspaper). The second investigation was carried out under in situ conditions in which three of these bedding materials (wheat straw, wood shavings, and straw pellets) were analyzed under practical conditions. In both experiments, airborne particle concentrations were detected online with the gravimetrically measuring analyzer TEOM 1400a (Rupprecht & Patashnick Co., Franklin, MA). In the laboratory experiment, the TEOM was equipped successively with different inlets to measure the particle fractions PM₁, PM_2.5, PM₁₀, and PM₂₀. During the in situ experiment, only the fraction PM₁₀ was detected. In the laboratory experiment, hemp and linen had the highest generation of airborne particles in all fractions. The lowest particle generation was detected with straw pellets. Results of the in situ investigation supported results of the laboratory experiment with respect to mean particle generation of straw pellets. With an average of 111.2 ± 149.2 μg/m³, it was significantly lower than the mean particle generation of wheat straw with 227.5 ± 280.8 μg/m³. The particle generation of wood shavings had an average of 140.9 ± 141.9 μg/m³ and also was significantly lower than the generation by wheat straw. An activity-correlated variation of particle concentrations was found. In conclusion, taking both experiments into consideration, straw pellets seemed to be suitable for horse stables, to promote an improvement in the stable climate in relation to airborne particle formation.     

Skeletal Atavism in a Miniature Horse

An 8-month-old miniature horse filly was presented for evaluation of severe rotational and angular limb deformities of the thoracic and pelvic limbs. On radiographic examination, complete ulnas and fibulas were identified. These findings are consistent with a condition previously described as a form of atavism. The term atavism is used to describe the reappearance of a trait or character that was seen in all earlier evolutionary specimens of a particular species, but has not been seen in recent ancestors. The atavistic traits of complete ulnas and fibulas have previously been described in Welsh and Shetland Ponies, all of which had severe rotational and angular limb deformities. In this horse, bilateral osteochondritis dissecans of the medial trochlear ridge of the talii were also identified. To the authors' knowledge, this is the first report of the atavistic traits of complete ulnas and fibulas seen in the miniature horse.