Clinical use of computer-assisted orthopedic surgery in horses.

OBJECTIVE: To describe clinical applications of computer-assisted orthopedic surgery (CAOS) in horses with a navigation system coupled with a cone beam computed tomography unit. STUDY DESIGN: Retrospective clinical case series. ANIMALS: Thirteen adult horses surgically treated with CAOS. METHODS: Medical records were searched for horses that underwent CAOS between 2016 and 2019. Data retrieved included signalment, diagnosis, lameness grade prior to surgery, surgical technique and complications, anesthesia and surgery time, and information pertaining to the perioperative case management and outcome. RESULTS: In 10 cases, surgical implants were placed in the proximal phalanx, third metatarsal bone, ulna, or medial femoral condyle. In one case, navigated transarticular drilling was performed to promote ankylosis of the distal tarsal joints. In another case, an articular fragment of the middle phalanx was removed with the help of CAOS guidance. In the final case, a focal osteolytic lesion of the calcaneal tuber was curetted with the aid of CAOS. In seven cases, a purpose-built frame was used for the surgical procedure. All surgeries were performed successfully and according to the preoperative plan. CONCLUSION: Computer-assisted orthopedic surgery can be an integral part of the clinical case management in equine surgery. To optimize workflow and time-efficiency, the authors recommend designating one team for operative planning and another for the execution of the surgical plan. Specialized equipment, such as the purpose-built frame, will further improve CAOS applications in equine surgery. CLINICAL SIGNIFICANCE: After they have become familiar with the operational principles, equine surgeons can readily apply CAOS for a broad spectrum of indications.

Radiographic and Computed Tomographic Configuration of Incomplete Proximal Fractures of the Proximal Phalanx in Horses Not Used for Racing.

OBJECTIVE: To characterize the configuration of incomplete proximal fractures of the proximal phalanx (P1) in horses not used for racing and compare radiographic with computed tomography (CT) findings. STUDY DESIGN: Historical cohort. ANIMALS: Twenty-four horses with incomplete fractures of P1. METHODS: Medical records of horses not used for racing diagnosed with an incomplete proximal fracture of P1 based on clinical and radiographic examination and confirmed by CT between 2008 and 2013 were retrieved. Radiographs and CT studies of these horses were analyzed using a subjective grading system and by measuring variables that characterized fracture configuration. RESULTS: Twenty-four horses were included (20 Warmbloods) with a mean age of 9.5 years and mean body weight of 574 kg. Fourteen forelimbs and 10 hind limbs were affected. Mean duration of lameness was 8.7 weeks. Computed tomography was superior to radiography in both identifying the fracture and determining fracture size and location. On CT, 92% of fractures were located in the mid-sagittal plane. Mean proximodistal length of the fracture was 13 mm. Fractures were frequently not bicortical. Fractures in forelimbs were located significantly more dorsally than fractures in hind limbs. A distinct fracture pattern with 2 subchondral lines running parallel in close proximity to each other was identified in 54% of cases. CONCLUSION: Incomplete proximal fractures of P1 have significant variation in their configurations, especially their dorsopalmar/-plantar location. Computed tomography examination allowed clear identification of the fracture configurations and was superior to radiography.

Field performance of two rapid screening tests in active surveillance of transmissible spongiform encephalopathies in small ruminants.

Recently, screening tests for monitoring the prevalence of transmissible spongiform encephalopathies specifically in sheep and goats became available. Although most countries require comprehensive test validation prior to approval, little is known about their performance under normal operating conditions. Switzerland was one of the first countries to implement 2 of these tests, an enzyme-linked immunosorbent assay (ELISA) and a Western blot, in a 1-year active surveillance program. Slaughtered animals (n = 32,777) were analyzed in either of the 2 tests with immunohistochemistry for confirmation of initial reactive results, and fallen stock samples (n = 3,193) were subjected to both screening tests and immunohistochemistry in parallel. Initial reactive and false-positive rates were recorded over time. Both tests revealed an excellent diagnostic specificity (>99.5%). However, initial reactive rates were elevated at the beginning of the program but dropped to levels below 1% with routine and enhanced staff training. Only those in the ELISA increased again in the second half of the program and correlated with the degree of tissue autolysis in the fallen stock samples. It is noteworthy that the Western blot missed 1 of the 3 atypical scrapie cases in the fallen stock, indicating potential differences in the diagnostic sensitivities between the 2 screening tests. However, an estimation of the diagnostic sensitivity for both tests on field samples remained difficult due to the low disease prevalence. Taken together, these results highlight the importance of staff training, sample quality, and interlaboratory comparison trials when such screening tests are implemented in the field.

Atypical scrapie in a Swiss goat and implications for transmissible spongiform encephalopathy surveillance.

Different types of transmissible spongiform encephalopathies (TSEs) affect sheep and goats. In addition to the classical form of scrapie, both species are susceptible to experimental infections with the bovine spongiform encephalopathy (BSE) agent, and in recent years atypical scrapie cases have been reported in sheep from different European countries. Atypical scrapie in sheep is characterized by distinct histopathologic lesions and molecular characteristics of the abnormal scrapie prion protein (PrP(sc)). Characteristics of atypical scrapie have not yet been described in detail in goats. A goat presenting features of atypical scrapie was identified in Switzerland. Although there was no difference between the molecular characteristics of PrP(sc) in this animal and those of atypical scrapie in sheep, differences in the distribution of histopathologic lesions and PrP(sc) deposition were observed. In particular the cerebellar cortex, a major site of PrP(sc) deposition in atypical scrapie in sheep, was found to be virtually unaffected in this goat. In contrast, severe lesions and PrP(sc) deposition were detected in more rostral brain structures, such as thalamus and midbrain. Two TSE screening tests and PrP(sc) immunohistochemistry were either negative or barely positive when applied to cerebellum and obex tissues, the target samples for TSE surveillance in sheep and goats. These findings suggest that such cases may have been missed in the past and could be overlooked in the future if sampling and testing procedures are not adapted. The epidemiological and veterinary public health implications of these atypical cases, however, are not yet known.