Incomplete fracture of the talus secondary to maladaptive stress remodeling in a horse.

CASE DESCRIPTION: A 6-year-old Quarter Horse gelding used for barrel racing was evaluated for acute onset of non-weight-bearing lameness of the left hind limb following strenuous exercise. CLINICAL FINDINGS: Nuclear scintigraphic imaging revealed focal increased radiopharmaceutical uptake centrally within the left talus. Subsequent standard radiographic and ultrasonographic examinations of the tarsus failed to identify the cause of the increased radiopharmaceutical uptake; however, the lameness was definitively localized to the tarsocrural joint by intra-articular anesthesia. Subsequent MRI sequences of the left tarsus revealed an incomplete fracture of the talus that extended distally from the trochlear groove and evidence of maladaptive stress remodeling of the trochlear groove of the talus and distal intermediate ridge of the tibia. TREATMENT AND OUTCOME: The horse was treated conservatively, with management consisting of stall confinement, physical rehabilitation, therapeutic laser therapy, and intra-articular autologous conditioned serum administration. The lameness resolved, and the horse was competing at its previous level within 15 months after lameness onset. CLINICAL RELEVANCE: Although rare, incomplete fracture of the talus should be considered as a differential diagnosis for horses that develop acute hind limb lameness following strenuous exercise, especially when that exercise involves abrupt changes in direction while the horse is traveling at maximal speed. Acquisition of additional oblique projections during radiographic evaluation of the tarsus might be useful for identification of such fractures, but definitive diagnosis may require advanced diagnostic imaging modalities such as CT and MRI. Horses with incomplete fractures of the talus can be successfully treated with conservative management.

Computed tomography of the pharynx in a closed vs. open mouth position.

The pharynx is anatomically complex and evaluation can be difficult even with cross-sectional imaging. Eight animals had computed tomography (CT) studies of the head performed with the mouth open and closed. The studies were anonymized and evaluated by four radiologists for visibility of six anatomic regions (dorsal wall of nasopharynx, lumen of nasopharynx, dorsal margin of the soft palate, ventral margin of the soft palate, oropharynx, and laryngopharynx) and for certainty of a normal or abnormal diagnosis of four different anatomic regions (nasopharynx, soft palate, oropharynx, and laryngopharynx). Mean visual scores differed significantly between mouth positions and were improved when the mouth was open. The ability of radiologists to classify anatomic regions as normal or abnormal vs. unsure also varied between mouth positions, and there was greater uncertainty when the mouth was closed. In addition, estimated volume of the air-filled nasopharynx differed significantly as a function of mouth position and was greater when the mouth was open (mean=1.187 cm(3) , SE=0.177) vs. closed (mean=0.584 cm(3) , SE=0.116). Computed tomographic evaluation of the pharynx can be improved with the mouth open.

Validation of a 40 MHz B-scan ultrasound biomicroscope for the evaluation of osteoarthritis lesions in an animal model.

OBJECTIVE: To evaluate high frequency (40 MHz) B-mode ultrasound for the detection of osteoarthritis (OA) lesions of varying severity in an animal model of OA. DESIGN: Ultrasound biomicroscopy (UBM) was performed on the femoral articular surface of adult rabbits with unilateral transection of the anterior cruciate ligament at 4, 8 and 12 weeks post-surgery and on control rabbits. The articular cartilage was examined and graded macroscopically and histologically for OA lesions. Histological examination was used as a reference to determine sensitivity and specificity of ultrasonographic and macroscopic examination regarding fibrillation and ulceration of articular cartilage. RESULTS: Identification of slight surface irregularities was made possible with UBM. The sensitivity and specificity of UBM were 92.3% and 96.4%, respectively, to detect histological fibrillation and 90.9% and 97.6%, respectively, to identify histological ulceration. Macroscopic examination using India Ink had a sensitivity and specificity of 80% and 96.4%, respectively, for fibrillation and 90.9% and 90.5%, respectively, for ulceration when compared to histology. A high correlation (rsp=0.90) was found between ultrasonographic and histological scores. CONCLUSIONS: UBM of articular cartilage reflects histological structure and can accurately detect early changes such as fibrillation. UBM has the potential to be a valuable tool for the in vivo identification of early lesions of OA and for monitoring the disease or efficacy of novel therapy if it can be packaged in a minimally invasive format suitable for intra-articular imaging.