Accuracy of Computed Tomography in Diagnosing Temporomandibular Joint Osteoarthritis Relative to Histopathological Findings-An Ex Vivo Study of 41 Horses.

Overview

• This research evaluated how accurately computed tomography (CT) can diagnose osteoarthritis (OA) in the temporomandibular joints (TMJ) of horses by comparing CT imaging results to histopathological findings (microscopic tissue analysis).
• The study found that certain CT findings commonly attributed to OA may actually represent normal age-related joint changes, affecting the accuracy of using CT alone to diagnose TMJ OA in horses.

Background and Purpose

• Computed tomography (CT) is an imaging technique used to visualize internal structures, including joints, to identify disease.
• In equine veterinary medicine, CT is employed to assist in diagnosing temporomandibular joint (TMJ) diseases such as osteoarthritis (OA), a degenerative joint condition causing cartilage and bone damage.
• However, the accuracy of CT in correctly diagnosing TMJ OA relative to the gold standard—histopathological examination—had not been definitively established prior to this study.
• The purpose was to assess whether CT findings reliably correlate with actual OA changes seen in tissue samples from the joints.

Methods

• A sample of 82 TMJs taken from 41 horses was used in this ex vivo (outside the living organism) study.
• Each joint underwent CT imaging to identify abnormalities within the joint structures.
• Following imaging, the joints were sampled for histopathology, allowing microscopic examination of joint tissue to confirm presence or absence of OA.
• The horses and their joints were classified into groups based on age-related changes or OA-related changes observed histologically and radiologically.
• Statistical analysis was performed to evaluate:
• The frequency of CT findings in all joints.
• Correlations between CT findings and histopathological diagnosis of OA.
• Diagnostic performance (sensitivity and specificity) of CT in detecting TMJ OA under different criteria.

Key Findings

• CT abnormalities were detected in 79% of the joints examined.
• A substantial number of CT findings were classified as ‘CT anatomical variations,’ which are likely related to normal age-associated joint remodeling rather than disease.
• Only 50% of joints showing CT abnormalities also demonstrated histopathological signs of OA, indicating many CT findings do not correspond to actual disease.
• When all CT findings were considered indicative of OA (even those reflecting normal anatomical variation), the specificity was low (0.41), meaning many false positives were diagnosed.
• Excluding all anatomical variations from CT criteria to improve specificity led to lower sensitivity (0.56), causing many false negatives where OA was missed.
• A compromise was found by including one particular anatomical variation—subchondral bone cysts—as a sign of OA on CT scans:
• This approach increased sensitivity to 0.79, meaning more true cases of OA were detected.
• Specificity also remained high at 0.92, reducing false positives significantly.

Conclusions and Implications

• Not all CT changes in equine TMJs represent osteoarthritic disease; some reflect normal aging or remodeling.
• CT alone, if interpreted strictly by presence of any abnormality, tends to overdiagnose TMJ OA due to false positives.
• Conversely, excluding all subtle anatomical variations risks missing cases of OA, leading to false negatives.
• Including subchondral bone cysts as a diagnostic criterion for TMJ OA on CT improves diagnostic accuracy by balancing sensitivity and specificity.
• Since this study was conducted on cadaver samples, the clinical applicability and diagnostic performance of these criteria need to be validated in live horses (in vivo studies).
• This information can guide veterinarians in more accurate interpretation of TMJ CTs, potentially improving diagnosis and treatment decisions for equine TMJ OA.