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

Abstract: To compare effusion scores obtained via ultrasound (US) and computed tomography (CT) in equine cervical articular process joints (CAPJs). Unassigned: Cadaveric cervical specimens (skull through C7) from 6 horses were used. One specimen was used to establish maximal joint distension volume. In the main study phase, 50 CAPJs were randomly assigned to receive 0, 2, or 4 mL of positive contrast solution. The CAPJs were imaged via US and CT before and after injection. Effusion was subjectively graded on a scale of 0 to 4 for both modalities. Statistical analyses compared pre- and post-injection effusion scores across cervical sites, injection volumes, and imaging techniques. Unassigned: Pre-injection effusion scores did not differ between US and CT. Post-injection effusion scores significantly increased at the C2-C3, C3-C4, and C5-C6 sites (P ≤ .01) for both modalities. At C6-C7, CT showed a significant increase in score compared to US (P < .001). Volume-dependent effects were significant at C4-C5 for both modalities and at C6-C7 for CT only. Extravasation occurred in 39 of 50 CAPJs following injection. Unassigned: Ultrasonography accurately detected effusion within equine CAPJs, yielding comparable scores to CT across most cervical sites and injection volumes. Computed tomography demonstrated greater sensitivity at caudal cervical levels and more readily identified volume-dependent change. Unassigned: US represents an easy, accessible tool for identifying CAPJ effusion in horses. While CT remains more effective in the caudal cervical region, US offers a reliable first-line approach for detecting effusion and therefore guiding therapeutic interventions.