Abstract:

Objective   To investigate high-frequency ultrasonography manifestation and clinical value in diagnosis of acute lateral traumatic patellar dislocation(LTPD). Methods   Both knees of 40 patients with acute LTPD were examined by high-frequency ultrasonography, and compared with the high-frequency ultrasonography images of healthy knees. The diagnostic accordance rate and accuracy of high-frequency ultrasonography compared with surgical findings were analyzed. Results   ①High-frequency ultrasonography can show medial patellofemoral ligament(MPFL) injury, vastus medialis obliquus (VMO) edema and/or elevation, articular cartilage injury of the medial patella and the lateral femoral condyle, medial collateral ligament (MCL) injury , and knee hemarthrosis. Elevation of the VMO muscle fibers by measuring the vertical distance from the adductor tubercle to the inferior margin of the VMO muscle in the coronal plane of the adductor tendon, and the shortest distance between the cortex of the medial femoral condyle in the sagittal plane were 2.3cm(0.7~4.2cm)and 0.45cm(0.1~2.9cm).  These measurements were significantly larger than the corresponding values in the control group. ②The accordance rate, sensitivity and specificity of high-frequency ultrasonography diagnosis on partial MPFL tear were 92.3%, 85.7% and 94.7% respectively. The accordance rate, sensitivityand specificity of high-frequency ultrasonography diagnosis on complete MPFL tear were 90%, 94.7% and 85.7% respectively. The accordance rate, sensitivity and specificity of high-frequency ultrasonography diagnosis on grade Ⅱarticular cartilage injury were 57.1%, 36.4% and 85% respectively. The accordance rate, sensitivity and specificity of high-frequency ultrasonography diagnosis on grade Ⅲ articular cartilage injury were 75%, 81.8% and 85% respectively. The accordance rate, sensitivity and specificity of high-frequency ultrasonography diagnosis on grade Ⅳ articular cartilage injury were 81.8%, 100% and 90.9% respectively. Conclusion   High-frequency ultrasonography can clearly show MPFL as well as adjunctive structures， and can clearly and accurately show injuries after acute LTPD. High-frequency ultrasonography is an easy, reliable and rapid method in diagnosing injuries after acute LTPD.

Key words: High-frequency ultrasonography； Lateral traumatic patellar dislocation； Medial patellofemoral ligament