Acute patellar tendon ruptures: The diagnostic utility of sonography for tear detection and characterization in the emergent setting.

Purpose To determine the accuracy of ultrasound for diagnosing and characterizing acute patellar tendon ruptures, as well as to investigate secondary sonographic signs that may aide in identifying tear location, using surgical findings as the reference standard. Methods The sonographic findings of 46 consecutive knee ultrasounds obtained for clinically-suspected extensor mechanism injury (23 cases reporting a torn patellar tendon and 23 cases reporting an intact patellar tendon) were compared with intra-operative findings in those patients who underwent patellar tendon surgery. Twomusculoskeletal radiologists blindly and retrospectively reviewed all 46 cases to indicate the presence or absence of a patellar tendon tear, to identify suspected tear location, and to comment on refraction artifact and peritendinous fluid, which were also correlated with intraoperative findings. Results The sensitivity, specificity, positive predictive value, and negative predictive value of ultrasound for diagnosing patellar tendon rupture were 100%. Further, ultrasound correctly identified tear location in 94% of surgically-proven cases. The presence of refraction artifact (P \u3c 0.05) and increasing amount of peritendinous fluid (P \u3c 0.05) were associated with higher likelihood of tear. Relying solely on refraction artifact to identify tear location proved less accurate (P \u3c 0.05, P = 0.08) than using all sonographic signs available. There was no difference in tear location accuracy with varying amount of peritendinous fluid (P \u3e 0.24) or conspicuity of refraction artifact (P = 1.0). Conclusions Ultrasound is highly accurate for diagnosing and characterizing acute patellar tendon ruptures. Because acute repair is preferred in order to avoid long-term morbidity, and missed clinical diagnosis reportedly ranges from 10-50%, we advocate for an increasing role of ultrasound in the emergency setting to rapidly and effectively evaluate the integrity of the patellar tendon