Sonographic finding of medial ankle subcutaneous edema and its association with posterior tibial tenosynovitis

Background: To evaluate if the sonographic finding of medial ankle subcutaneous (subQ) edema is associated with posterior tibial tenosynovitis (PTTS). Methods: Sonographic images of the medial ankle soft tissues from 40 patients with PTTS and 37 patients with a normal posterior tibial tendon (PTT) were randomized and independently evaluated by two musculoskeletal radiologists for the presence or absence of subQ edema. Both radiologists were blinded to the images and status of the PTT and the patient's history. Statistical analyses included the Chi-square test and Cohen's Kappa statistics for inter-observer agreement. Results: A statistically significant association was seen for the presence of medial ankle subQ edema and PTTS among both radiologists' findings. Of the 40 patients with PTTS, 33 (82.5%) were found positive by the first radiologist for medial ankle subQ edema, while no subQ edema was found in 28 of the 37 (75.7%) patients with a normal PTT (P < 0.001). Similarly, the second radiologist found that 33 of the 40 (82.5%) with PTTS were positive for subQ edema, while no subQ edema was found in 24 of the 37 (64.9%) patients with a normal PTT (P < 0.001). There was also substantial inter-observer agreement between the 2 radiologists (kappa-value = 0.79; 95% confidence intervals: 0.65, 0.93). Conclusion: A statistically significant association was present for the association of the sonographic finding of medial ankle subQ edema and the presence of PTTS. Further studies could evaluate if the sonographic finding of medial ankle subQ edema is an early predictor of PTT dysfunction.