A TECHNIQUE FOR MAGNETIC RESONANCE IMAGING OF EQUINE CADAVER SPECIMENS

We tested an adaptation of a technique for performing magnetic resonance (MR) imaging of human cadaver limbs in the horse. The forelimbs from a normal horse were collected, frozen, and sealed with a paraffin-polymer combination prior to imaging with either a high- or midfield magnetic resonance scanner. Each forelimb was defrosted, scanned, and refrozen on two separate occasions. A five-point scale was used to evaluate the quality of each set of sagittal and transverse, T1-weighted images of each digit. There was no difference in image quality between first and second scans of either specimen (p > 0.05). We conclude that this technique allows investigators to bank tissue specimens for future magnetic resonance imaging without significant loss of image quality.     

Magnetic resonance imaging of the palmar aspect of the equine podotrochlear apparatus: normal appearance

The purpose of this study was to describe the normal magnetic resonance (MR) imaging characteristics of the palmar structures of the equine podotrochlear apparatus by means of retrospective evaluation of MR imaging studies of 16 cadaver limbs. The articular aspect of the distal sesamoid bone was not evaluated in this study. Equine digits were imaged with a human knee radiofrequency coil in a 1.5 T magnetic field, using spin echo (SE) T1-weighted, turbo spin echo proton density (TSE PD)-weighted with and without fat saturation (FS), and FS TSE T2-weighted sequences. The limbs were dissected after imaging to validate the absence of gross abnormalities of the flexor aspect of the distal sesamoid bone, of the deep digital flexor tendon, and the distal impar sesamoidean ligament. Seven deep digital flexor tendons were subjected to histologic examination to exclude any microscopic tendon pathology. The anatomic structures of the podotrochlear apparatus were easily identified on MR images. Compact bone of the flexor cortex of the distal sesamoid bone had low intensity signal on all sequences. In 11 digits an increased signal was seen within the thickness of the sagittal eminence of the flexor cortex in SE T1-weighted images and in TSE PD-weighted images without FS. Trabecular bone had a granular appearance and high signal in SE T1-weighted sequences and TSE images without FS. The deep digital flexor tendon had low signal on FS T2-weighted images, while on short echo time sequences (T1- and PD-weighted sequences), the tendon signal varied depending on the relative orientation between its fibers and the static magnetic field. Seven tendons had stippled appearance due to small intratendonous foci of slightly increased signal on transverse T1-weighted images. MR imaging provides a thorough evaluation of the anatomical structure of the podotrochlear apparatus: A good knowledge of the MR imaging appearance and anatomy and an awareness of potential pitfalls will improve diagnostic specificity for the detection of pathologic changes.     

Implantation of an Uncemented Total Hip Prosthesis Technique and Initial Results of 100 Arthroplasties

A porous-coated modular total hip system was developed for uncemented implantation in dogs. The operative technique was developed in cadaver bones and live animals. One hundred uncemented total hip arthroplasties were performed in 92 dogs. Results were successful in 98% of the joints during follow-ups of 3 months or more. Complications included three luxations of the prosthetic joint, two fissure fractures of the femoral cortex, and one complete displacement of the acetabular component from its bony bed. Four complications were resolved successfully.     

Hormonal response to dobutamine cardiac stress testing in a conscious canine model of early left ventricular dysfunction induced by chronic rate overload

The aims of this study were to investigate (1) hormonal activation before and during dobutamine cardiac stress testing (DST) in a canine model of early left ventricular dysfunction (ELVD) induced by rapid right ventricular pacing (RRVP) and (2) the relationship between this hormonal profile and carnitine concentrations.Before the pacing period, the 6 dogs were assigned to 2 groups according their baseline total plasma carnitine concentration. A DST was performed on each dog before activation of the pacemaker and every 3 to 4 days during development of 3 progressive stages of ELVD (stages 1, 2 and 3). Plasma atrial natriuretic factor (ANF), angiotensin II (ANG II) and endothelin-1 (ET-1) levels were measured at the start and at the end of each DST. Effects of ELVD, DST and plasma carnitine concentration on these measurements were tested.The RRVP induced a significant increase of ANF and ANG II and a non significant trend toward increase of ET-1 in all dogs.Before the pacing period, ANF remained constant during the DST in dogs with normal total plasma carnitine concentration, while it significantly decreased in dogs with low total plasma carnitine concentration. Dobutamine stress testing induced a significant decrease in ANF in all dogs in ELVD. Dobutamine infusion induced a significant increase in ANG II in all dogs before as well as during the pacing period while ET-1 was unchanged.These results suggest that investigation of the hormonal profile before and after a dobutamine challenge might provide important diagnostic information in dogs with asymptomatic or mildly symptomatic cardiac dysfunction of different origins.