Ultrasonographic detection of cranial cruciate ligament pathology in canine stifles without cranio-caudal instability

Objective Explore the value of musculoskeletal ultrasound in detecting cruciate ligament pathology  Background Partial tears of the cranial cruciate ligament (CCL) can be difficult to diagnose due to the lack of instability present on orthopedic examination. Advanced diagnostics would be required for further evaluation. While a common tool in human medicine, MRI is of limited use in canines due to cost and the need for general anesthesia. Musculoskeletal ultrasound (MSK-US) can be performed without anesthesia but there are no current studies to date evaluating its usefulness in detecting partial tears of the cruciate ligaments Evidentiary value This is a retrospective case series (n=32) of dogs that underwent diagnostic MSK-US of the stifle who later had a surgical procedure (stifle arthroscopy/arthrotomy) to evaluate the intra-articular space. Methods Medical records were evaluated between May 2014 - April 2020 for canines with clinically stable stifles that underwent both an MSK-US of the stifle followed by stifle surgery. Ultrasound findings of the CCL were compared to surgical findings (considered gold standard). Results Compared to arthroscopy, ultrasound was a very sensitive test in detecting CCL pathology however it is less specific. Its sensitivity (SN), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV) were 100%, 58.3%, 81.5%, and 100% respectively. Conclusion MSK-US is a non-invasive test that can be performed with little to no sedation. Using a high frequency 18-5MHz linear transducer, MSK-US is a sensitive test for detecting partial CCL injuries in dogs and may aid in its diagnosis for canines without stifle instability and be useful in guiding treatment. As it is less specific, arthroscopy would be necessary to further confirm the intra-articular pathology. Application Diagnostic MSK-US is a non-invasive tool that can be used to detect CCL pathology in the stifle. Its application can help guide treatment recommendations prior to a more invasive diagnostic/therapeutic procedure such as surgery or arthroscopy.