Radiographic Edema Is a Predictor of de Quervain's Tenosynovitis

Background  de Quervain's tenosynovitis (DeQ) is a clinical diagnosis; however, due to the symptom overlap with other pathologies, it can occasionally be challenging to make an accurate diagnosis, especially for nonorthopaedic trained physicians. Questions/Purposes  We hypothesized that the ratio of radial-sided to ulnar-sided soft tissue swelling could serve as a universally accessible diagnostic tool to assist in differentiating DeQ from other upper extremity conditions. Patients and Methods  We retrospectively identified patients with isolated DeQ (M65.4), thumb carpometacarpal arthritis (M18.X), or carpal tunnel syndrome (G56.0x) between 2018 and 2019. Five blinded, independent reviewers evaluated anterior-posterior radiographs of the affected wrist. A digital caliper was used to measure the shortest distance from the lateral cortex of the distal radius and the medial cortex of the distal ulna to the outer edge of the radial and ulnar soft tissue shadows, respectively. Results  The mean radial:ulnar ratio in the DeQ group was significantly larger than in the control groups. The interclass correlation coefficient showed strong agreement between all measurements. Patients with a radial:ulnar ratio of 1.7 or higher had a 61% chance of having DeQ with a 56.5% sensitivity, 66.3% specificity, 59.3% positive predictive value (PPV), and 63.8% negative predictive value. A ratio of more than 2.5 correlates to a 55% chance of having DeQ with a sensitivity of 12.9%, specificity of 96.9%, and PPV of 78.6%. Conclusion  The ratio of radial- to ulnar-sided wrist edema can be used as a novel diagnostic aid in DeQ, especially for those not trained in orthopaedics or hand surgery. Level of Evidence  Level IV, diagnostic study.