Ultrasonography accurately detects equine cervical articular process joint effusion with comparable performance to computed tomography.

Overview

• The study evaluated the effectiveness of ultrasonography (US) in detecting joint effusion in equine cervical articular process joints (CAPJs) and compared its performance to computed tomography (CT).
• Results showed that US detects effusion with accuracy comparable to CT in most cervical sites, though CT was more sensitive in the caudal cervical region.

Introduction and Aim

• The cervical articular process joints (CAPJs) in horses are important for neck movement and are prone to joint effusion—an accumulation of fluid suggesting inflammation or injury.
• Detecting effusion accurately helps in diagnosing joint disorders and guiding treatments.
• Computed tomography (CT) is a sensitive imaging technique but less accessible and more expensive.
• Ultrasonography (US) is more accessible and portable but its accuracy for detecting CAPJ effusion needed validation.
• The researchers aimed to compare effusion scores obtained via US and CT in equine CAPJs under controlled experimental conditions.

Methods

• Cadaveric cervical specimens including the skull through C7 vertebra were collected from 6 horses.
• One specimen was used initially to determine the maximum joint distension volume for the study.
• For the main phase, 50 CAPJs were randomly assigned to receive 0 mL (control), 2 mL, or 4 mL of a positive contrast fluid injected intra-articularly to simulate effusion.
• Each CAPJ was imaged by both US and CT before and after injection.
• Effusion was graded subjectively on a 0-4 scale in both imaging modalities.
• Statistical analyses compared pre- and post-injection effusion scores across:
• Cervical joint sites (C2-C3 through C6-C7)
• Differing injected volumes
• Imaging techniques (US vs CT)

Results

• Pre-injection effusion scores were similar for US and CT, confirming baseline equivalence.
• Post-injection, significant increases in effusion scores were found at cervical joints C2-C3, C3-C4, and C5-C6 using both US and CT (P ≤ .01).
• At the C6-C7 joint (the caudal-most segment examined), CT showed significantly higher effusion scores compared to US (P < .001), indicating better sensitivity of CT at this level.
• Volume-dependent increases in effusion scores were significant at C4-C5 for both modalities, meaning higher injected fluid volumes corresponded with higher effusion grades.
• At C6-C7, only CT demonstrated significant volume-dependent effects.
• Extravasation, or leakage of contrast fluid outside the joint space, occurred in 39 of 50 CAPJs, a factor considered in interpreting imaging results.

Discussion

• Ultrasonography was able to accurately detect joint effusion in CAPJs across most cervical sites and injection volumes, with comparable grading to CT.
• However, at the caudal cervical level (C6-C7), CT was superior in detecting effusion and in detecting fluid volume changes.
• The extravasation noted could complicate interpretation but was common despite careful injection.
• Given that US is a readily available, non-invasive, and relatively low-cost tool, it offers a practical first-line diagnostic method for evaluating CAPJ effusion in horses.
• CT, while more cumbersome and expensive, remains more sensitive especially in more caudal joints, and is preferable where detailed evaluation or precise volume assessment is needed.

Conclusions

• The study supports the use of ultrasonography as an effective, accessible modality for detecting CAPJ effusion in horses and monitoring joint health.
• This finding provides clinicians with confidence to use US as a first step in diagnosis, reserving CT for cases requiring more detailed imaging, particularly in the caudal cervical region.
• Overall, ultrasonography can guide therapeutic interventions effectively by identifying joint effusion without the need for immediate CT imaging in most cases.