Three-dimensional models of the equine larynx can be used to perform traditional measures of arytenoid abduction and permit the positioning of modeled implants to demonstrate the anatomic feasibility of placing a rigid implant across the cricoarytenoid joint.

OBJECTIVE: To develop 3D models of larynges to compare arytenoid abduction measurements between specimens and models, and to investigate the anatomic feasibility of placing an implant across the cricoarytenoid joint (CAJ) with or without arthrotomy. SAMPLES: Cadaveric equine larynges (n = 9). PROCEDURES: Equine larynges underwent sequential CT scans in a neutral position and with 2 arytenoid treatments: bilateral arytenoid abduction (ABD) and bilateral arytenoid abduction after left cricoarytenoid joint arthrotomy (ARTH). Soft tissue, cartilage, and luminal volume 3-dimensional models were generated. Rima glottidis cross-sectional area (CSA) and left-to-right quotient (LRQ) angles were measured on laryngeal specimens and models. Arytenoid translation, articular contact area, and length of modeled implants placed across the CAJ were measured on models. Data were analyzed using paired t test or ANOVA and Tukey's post hoc test or non-parametric equivalents (P < .05). RESULTS: ARTH CSA was larger for laryngeal specimens than models (P = .0096). There was no difference in all other measures of CSA and LRQ angle between treatment groups or between specimens and models. There was no difference between ABD and ARTH groups for arytenoid cartilage translation, contact area, and implant length. The articular contact area was sufficient for modeled implant placement across the CAJ with a narrow range of implant lengths (17.59 mm to 23.87 mm) across larynges with or without arthrotomy. CLINICAL RELEVANCE: These results support further investigation of a CT-guided, minimally invasive surgical procedure. Future studies will evaluate the outcomes of the new procedure for technical precision, biomechanical stability, and post-operative success rates for horses with recurrent laryngeal neuropathy (RLN).

Pathology in Practice.

In collaboration with the American College of Veterinary Pathologists.

Use of a circular fixator construct to facilitate closed reduction and percutaneous stabilization of a distal femoral physeal fracture in a dog.

Background: Fractures of the distal femoral physis are the most common physeal fracture sustained by skeletally immature dogs. Reduction and stabilization of these fractures can sometimes be achieved through closed reduction, primarily in fractures that are nominally displaced. Circular external fixator constructs have been used to assist in indirect, closed reduction of fractures at other anatomic locations in dogs and this report describes application of this method to reduce a displaced Salter-Harris type II fracture of the distal femur in a 1-year-old dog. Case Description: A 1-year-old female spayed Akita was referred for treatment of a Salter-Harris type II fracture of the right distal femur. The epiphyseal segment was laterally and slightly caudally displaced. Multiple attempts to manually reduce the fracture during surgery were unsuccessful, so a two-ring circular external fixator construct was applied to facilitate distraction and reduction. The construct was applied by placing a medial-to-lateral Kirschner wire in both the mid-femoral diaphysis and in the distal femoral epiphysis. Distraction of the construct provided sufficient separation of the fracture segments to facilitate near anatomic reduction. The fracture was stabilized with two percutaneously placed Steinmann pins placed in Rush fashion. Radiographic union was confirmed 5 weeks after surgery. The dog was not lame and was bearing more weight on the right pelvic limb, as assessed using force plate analysis, 9 months following surgery. Goniometric measurements of stifle range of motion and thigh muscle circumference were similar between the pelvic limbs. Conclusion: Application of a two-ring circular construct would appear to be useful to facilitate closed reduction and percutaneous stabilization of distal femoral physeal fractures.

Long-term outcome following cranial biceps brachii tendon transposition in a dog with a traumatic cranial scapulohumeral luxation.

Background: Cranial luxation of the scapulohumeral has been rarely reported in dogs and there is limited information available regarding surgical management of this condition, particularly with respect to long-term functional outcomes. Case Description: This report describes the successful resolution of a chronic traumatic cranial scapulohumeral joint luxation in a dog that was stabilized by cranial transposition of the biceps brachii tendon of origin. At surgery, an osteotomy of the greater tubercle was performed and a trough was made in the exposed bed of the osteotomy. The transverse humeral ligament was incised, and the bicipital tendon was levered into the trough and secured in that location by reattachment of the greater tubercle using multiple Kirschner wires and a figure-of-eight tension band wire. Postoperatively, the dog was maintained in a Spica splint for 2 weeks. Although surgical reduction was performed 4 months after the original injury, the luxation did not recur and the dog did not have appreciable lameness 14 months following the surgery. Conclusion: Although cranial transposition of the bicipital tendon is an invasive procedure, this dog's scapulohumeral luxation did not recur and the procedure yielded an excellent long-term functional outcome.

Radiographic anatomy of the equine distal tibia.

The radiographic anatomy of the equine distal tibia is complex and is not widely described in the current literature. Superimposition and radiographic similarities between the different osseous structures of the equine distal tibia can make it difficult for anatomic localization of pathology. The purpose of this prospective, descriptive, anatomic study was to detail the normal anatomy of the equine distal tibia using routine radiographic projections and CT of the equine tarsus. Radiographic identification of the different osseous protuberances of the distal tibia on three cadaveric limbs was achieved using radiopaque markers and evaluation of multiplanar and 3D CT reconstructions to create anatomical maps. It was found that the lateral malleolus is composed of cranial and caudal protuberances that are superimposed over the intermediate cochlear ridge of the distal tibia on the lateromedial, dorsal 45° lateral-plantaromedial, and dorsal 65° medial-plantarolateral oblique views, thereby hindering visualization of the cranial protuberance of the lateral malleolus. The medial malleolus is a simple rounded protuberance with discrete margins. On the dorsal 65° medial-plantarolateral oblique, the medial malleolus is ill-defined due to superimposition with the talus. The intermediate cochlear ridge of the distal tibia extends in a craniolateral to caudomedial direction, with its cranial protuberance largely superimposed with the calcaneus and talus on the dorsoplantar view. In summary, the distal tibial anatomy is complex and a thorough anatomical reference is necessary when reviewing radiographs of the equine tarsus for pathology. A plantaro 15° distal 85° lateral-dorsoproximomedial oblique projection is proposed to isolate all distal tibial protuberances.

Use of combined transarticular pinning and external skeletal fixation for the reduction and stabilization of multiple metatarsophalangeal luxations in a cat.

CASE SUMMARY: A 1-year-old spayed female domestic shorthair cat presented for evaluation of a non-weight bearing right pelvic limb lameness after falling from a 4 m height. On orthopedic examination there was substantial swelling and pain on manipulation of the right pes. Radiographs were obtained under sedation, and these revealed dorsoproximal luxations of the third, fourth and fifth metatarsophalangeal joints, and lateral rotation of the second digit. Closed manual reduction under sedation was unsuccessful and open reduction under general anesthesia was therefore performed. Combined transarticular pinning and external skeletal fixation were performed to maintain reduction of the third and fourth digits. Marked postoperative swelling of the distal pes and internal rotation of the third and fourth digits were noted within 24 h of surgery. Three weeks postoperatively, the cat had a persistent weight bearing right pelvic limb lameness and minor pin tract inflammation. All implants were removed and the limb was splinted for 1 week. Internal rotation and pin tract inflammation had resolved at the time of splint removal, and the lameness resolved within 6 weeks of surgery. The cat was not lame, but radiographs revealed mild-to-moderate degenerative osteoarthrosis when the cat was evaluated 6 months after surgery. RELEVANCE AND NOVEL INFORMATION: There are limited reports describing metatarsophalangeal luxations in cats. Although several surgical techniques have been advocated, specific outcomes in clinical cases have not been reported. This report describes the clinical application and outcome of combined transarticular pinning and external skeletal fixation for the management of multiple metatarsophalangeal luxations in a cat.

Surgical management of dorsal scapular luxation in three dogs.

Scapular luxation is an uncommon cause of forelimb lameness in dogs and cats. Traumatic rupture of the serratus ventralis muscle allows the scapula to displace dorsally during weight-bearing. Specific documentation regarding clinical presentation and surgical techniques is limited, with no medium- to long-term results of surgical intervention in dogs described. Presented here are three cases of scapular luxation in dogs, treated with a modified surgical technique. Clinical outcome was considered good to excellent, with resolution of lameness and abnormal scapular motion in all three dogs. Medium- and long-term outcomes were assessed in two of the dogs, with an excellent outcome in both cases.

Analysis of feline splenic radiographic measurements and their correlation to ultrasonographic measurements.

Objectives The purpose of this study was to establish a method for feline splenic measurement on abdominal radiographs and evaluate for correlation between the radiographic measurements and ultrasonographic measurements. Methods One hundred cats with normal abdominal radiographs and ultrasound (US) studies of the spleen were evaluated. The hypothesis was that the measurement of the spleen on the radiographs would correlate with the measurement of the spleen on US. The radiographic and ultrasonographic measurements were tabulated and compared using linear regression and t-tests using unequal variances. Results The measurement of the spleen on the ventrodorsal projection was characterized as one of three shapes (A, B or C), and thereby based on the thickest part of the spleen (when corrected for radiographic magnification: A = 9.9 ± 2.2 mm; B = 8.1 ± 1.8 mm; C = 8.0 ± 2.3 mm). There were 48 cats where the head of the spleenwas seen on the right lateral (n = 10), the left lateral (n = 24) or both (n = 14) projections. On one left lateral, both the head and tail of the spleen were seen. There was weak correlation between the radiographic and US measurements(R ⩼0.6). Splenic thickness of shape A on the ventrodorsal projection was significantly greater than categories B and C. Conclusions and relevance Radiographic measurement of the spleen is not a reliable indicator of its ultrasonographic measurement. The ultrasonographic measurements seen in this study (mean of 8.0 ± 1.6 mm) were similar to measurements of the spleen reported in previous studies. It is rare to see the tail of the spleen on lateral feline abdominal radiographs.

CORRELATION OF ARTICULAR CARTILAGE THICKNESS MEASUREMENTS MADE WITH MAGNETIC RESONANCE IMAGING, MAGNETIC RESONANCE ARTHROGRAPHY, AND COMPUTED TOMOGRAPHIC ARTHROGRAPHY WITH GROSS ARTICULAR CARTILAGE THICKNESS IN THE EQUINE METACARPOPHALANGEAL JOINT.

Osteoarthritis of the metacarpophalangeal joint is common cause of lameness in equine athletes, and is hallmarked by articular cartilage damage. An accurate, noninvasive method for measuring cartilage thickness would be beneficial to screen for cartilage injury and allow for prompt initiation of interventional therapy. The objective of this methods comparison study was to compare computed tomographic arthrography (CTA), magnetic resonance imaging (MRI), and magnetic resonance arthrography (MRA) measurements of articular cartilage thickness with gross measurements in the metacarpophalangeal joint of Thoroughbred horses. Fourteen cadaveric, equine thoracic limbs were included. Limbs were excluded from the study if pathology of the metacarpophalangeal articular cartilage was observed with any imaging modality. Articular cartilage thickness was measured in nine regions of the third metacarpal bone and proximal phalanx on sagittal plane MRI sequences. After intra-articular contrast administration, the measurements were repeated on sagittal plane MRA and sagittal CTA reformations. In an effort to increase cartilage conspicuity, the volume of intra-articular contrast was increased from 14.5 ml, to maximal distention for the second set of seven limbs. Mean and standard deviation values were calculated, and linear regression analysis was used to determine correlations between gross and imaging measurements of cartilage thickness. This study failed to identify one imaging test that consistently yielded measurements correlating with gross cartilage thickness. Even with the use of intra-articular contrast, cartilage surfaces were difficult to differentiate in regions where the cartilage surfaces of the proximal phalanx and third metacarpal bone were in close contact with each other.

New concepts in standing advanced diagnostic equine imaging.

This article addresses the clinical application of magnetic resonance imaging (MRI) and computed tomography (CT) as applied to the standing equine patient. This discussion includes the logistics, advantages, disadvantages, and limitations of imaging a standing horse. In addition, a brief review is given of the physics of these modalities as applied in clinical practice, and the currently available hardware and software required by these techniques for image acquisition and artifact reduction. The appropriate selection of clinical cases for standing MRI and CT is reviewed, focusing on cases that are capable of undergoing standing surgeries following lesion diagnosis.