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

Abstract: Objective: Explore the value of musculoskeletal ultrasound in detecting canine 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 orthopaedic examination. Advanced diagnostics would be required for further evaluation. While a common tool in human medicine, magnetic resonance imaging (MRI) is of limited use in canines due to cost and the need for general anaesthesia. Musculoskeletal ultrasound (MSK-US) can be performed without anaesthesia but there are no current studies to date evaluating its usefulness in detecting partial tears of the cranial cruciate ligament. Evidentiary value: This is a retrospective case series of 32 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. Results: Compared to surgical findings, 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 18-5 MHz 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 or arthrotomy 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 canine stifle. Its application can help guide treatment recommendations prior to a more invasive diagnostic / therapeutic procedure such as surgery or arthroscopy.