Radiographic localisation of the entheses of the equine stifle.

REASON FOR PERFORMING STUDY: Injury to the tendons and ligaments of the equine stifle is a common cause of lameness in horses. Individual radiographic localisation of each tendon and ligament of the stifle has not been previously reported or demonstrated in multiple radiographic projections. OBJECTIVE: To create a series of radiographs identifying the origins and/or insertions of the tendons and ligaments of the equine stifle. STUDY DESIGN: Descriptive study of radiographic anatomy. METHODS: The location of all entheses were determined by gross dissection. The proximal tibia and fibula, distal femur, patella and menisci were isolated from one horse and used as a template. A series of 4 radiographs was obtained with each enthesis identified with barium paste. The radiographic landmarks for each enthesis were described and the best projection(s) for evaluation of each structure of interest identified. RESULTS: Forty-eight radiographic images were produced that demonstrated the best radiographic projections to define each enthesis. CONCLUSIONS: Radiography is the imaging modality most frequently used to evaluate the equine stifle. The images presented here will serve as a guide for evaluating radiographs of the equine stifle, particularly identifying avulsions and enthesopathies of ligamentous and tendinous origins and insertions.

In vivo diffusion characteristics following perineural injection of the deep branch of the lateral plantar nerve with mepivacaine or iohexol in horses.

REASONS FOR PERFORMING STUDY: Hindlimb proximal suspensory desmopathy is a common injury of sport horses but diagnosis can be difficult because diagnostic analgesia of the region lacks specificity. Perineural analgesia of the deep branch of the lateral plantar nerve (DBLPN) has been proposed as a more specific method of isolating pain of the proximal aspect of the suspensory ligament but the technique has not been evaluated in vivo. OBJECTIVES: To determine the extent of diffusion of contrast medium and mepivacaine following DBLPN analgesia using a single-needle injection technique and to determine if there is inadvertent involvement of the tarsal sheath and/or tarsometatarsal (TMT) joint using this technique. STUDY DESIGN: In vivo experimental study. METHODS: Perineural injection of the DBLPN was performed in 16 limbs with 3 ml of either mepivacaine hydrochloride or positive contrast medium. Contrast medium-injected limbs were radiographed 5, 15, and 30 min post injection and diffusion characteristics were described. In mepivacaine-injected limbs, synovial fluid from the TMT joint was obtained 10 and 20 min post injection and mepivacaine concentrations were analysed. RESULTS: At 5, 15 and 30 min post injection, the contrast medium extended, on average, 19.6, 20.6 and 21.0 mm proximal and 38.0, 43.5 and 51.9 mm distal to the injection site, respectively. Three of 8 (37.5%) limbs had evidence of contrast medium in the tarsal sheath. Two of 8 (25%) limbs had mepivacaine concentrations within the TMT joint sufficient to produce analgesia (>300 mg/l) at 10 min post injection. CONCLUSIONS: Contrast medium diffused further in a distal direction than in a proximal direction. Analgesia of the DBLPN can result in inadvertent involvement of the tarsal sheath and/or TMT joint.

Accuracy of a radiographic stitching technique to measure tibial plateau angle in large and giant breed dogs.

OBJECTIVE: To determine if a novel radiographic stitching technique yields accurate tibial plateau angle (TPA) measurements in large and giant breed dogs. METHODS: Three medio-lateral digital radiographic projections (traditional TPLO, stifle-centred, tarsus-centred) were obtained from each of 17 pairs of pelvic limbs from skeletally mature large and giant breed dogs. Eight observers performed image stitching followed by TPA measurements on the stitched (sTPA) and traditional radiographs (tTPA). The TPA was also measured on photographs made of isolated anatomical tibial specimens (aTPA). Measurements were compared between observers and between image type using ANOVA and correlation coefficients. RESULTS: There was no statistically significant difference in TPA between observers for tTPA or sTPA radiographs (p >0.05); both sTPA and tTPA were highly correlated with aTPA and with each other (r = 0.88, 0.89, and 0.97 respectively). CLINICAL RELEVANCE: This novel digital stitching method provides an alternative technique for accurately measuring TPA utilizing a stifle-centred radiograph that may be useful when traditional TPLO radiographs are difficult to obtain. This may be particularly useful in large and giant breed dogs because collimation to include the entire tibial length can preclude proper centring of the radiographic beam over the stifle.

Analysis of conformational variations of the cricoid cartilages in Thoroughbred horses using computed tomography.

REASONS FOR PERFORMING STUDY: Loss of arytenoid abduction is a common post operative complication of laryngoplasty without a definitive cause. It has been a clinical impression during laryngoplasty surgery that there is great conformational variability along the caudal edge of the Thoroughbred cricoid cartilage that could impact post operative retention of suture position. A change in suture position would probably lead to some loss of abduction. Defining any structural variability of the cricoid would be an initial step in determining whether this variability could impact on the retention of suture position. HYPOTHESIS: Anatomical variations in the larynx of Thoroughbred horses may be detected and measured using objective analysis and computed tomography. METHODS: Larynges were harvested from 15 mature Thoroughbred horses. Helical CT scans were performed on each specimen. Three independent observers performed a series of measurements on 2D and 3D reconstruction images using digital software. Measurements included the lateral cricoid angle, the caudal cricoid prominences, the distance to the cricoid slope, the angle of the cricoarytenoid joints (CAJ), the cricoid thickness and the suture angle. Mean, standard deviation, coefficient of variation and linear regression analysis were performed among all observers and all measurements. RESULTS: Notable conformational differences were evident on the 3D reconstructions. The highest degree of variability was found in 3 measurements: the distance to the lateral cricoid slope, the lateral cricoid angle and the cricoid thickness. A larger left CAJ angle directly and significantly correlated with a larger suture angle. CONCLUSIONS: There are notable conformational differences among cricoid specimens in the Thoroughbred larynx. POTENTIAL RELEVANCE: The morphometric differences identified may impact on optimal prosthesis placement and long-term retention. Since a larger lateral cricoid angle may facilitate abduction loss secondary to a displaced and loosened suture, alternative techniques for suture placement may be of value to prevent arytenoid abduction loss.