Cadaveric studies suggest that a thick part of the distal interosseous membrane (DIOM), known as the distal oblique bundle (DOB), contributes to the distal radioulnar joint (DRUJ)’s stability. We hypothesized that the DIOM thickness, measured through magnetic resonance imaging (MRI), has a clinically significant association with DRUJ stability.

We retrospectively reviewed patients, from February 2018 to April 2019, who underwent wrist MRI examination with physical examination for DRUJ stability. We evaluated the correlation between their MRI findings (i.e., triangular fibrocartilage complex [TFCC] tears and presence of the DOB) and DRUJ instability.

Out of 85 patients with an average age of 42 years, 45 (53%) had foveal TFCC tears, 29 (34%) had a DOB, and 38 patients (45%) had clinical DRUJ instability. Patients with DRUJ instability had a significantly higher incidence of foveal TFCC tears (30/38, vs 15/47, p < 0.001), while DOB was absent (36/38 vs. 20/47, p < 0.001). Among 45 patients with foveal TFCC tears, only 1 out of 13 patients with a DOB had DRUJ instability, whereas 29 out of 32 patients without a DOB had DRUJ instability (p < 0.001). The odds ratio for DRUJ instability was 11.7 (95% CI 2.9–47.5, p = 0.001) for foveal TFCC tear and 54.2 (95% CI 8.2–358.2, p < 0.001) for the absent DOB.

Clinical DRUJ instability was less common when the DOB is present in patients with foveal TFCC tears, which supports DOB's role as a secondary DRUJ stabilizer.