THE PREDICTIVE VALUE OF SONOGRAPHY OF ANTERIOR CRUCIATE LIGAMENT IN POSTTRAUMATIC HEMARTHROSIS

Periosteal avulsions of the femoral insertion of the anterior cruciate ligament (ACL) should be treated by reinsertion within 2 weeks of the injury. Due to painful muscular hypertension, the clinical examination of ligament stability incorrectly revealed negative results in 12-62% posttraumatically. The only sufficiently sensitive indication of ACL rupture is posttraumatic hemarthrosis. Therefore, early arthroscopy of any posttraumatic hemarthrotic knee joint is required to exclude or confirm ACL rupture. Up to 30% of such procedures are carried out with no clinical consequences. We therefore set out to test the value of sonography of the ACL in hemarthrosis of the injured knee joint. A total of 117 posttraumatic hemarthrotic knee joints were subjected to ultrasound examination prior to arthroscopic evaluation. With a 5 MHz linear scanner, the femoral insertion of the ACL at the femoral condyle is represented in the same projection of injured and noninjured knee joints. In non injured knee joints the hypoechic insertion of the ACL lies directly on the S-shaped line of the lateral femoral condyle. The space between the condyles is hyperechoic. In case of a femoral ACL avulsion the insertion of the ACL and the hyperechoic structures between the condyles are forced aside by a hypoechoic area. Of 51 arthroscopically demonstrated complete ruptures of the ACL, 49 were detected by sonography. In 16 cases sonography suggested ACL rupture, but this could not be confirmed by arthroscopy, though 8 of these cases showed evidence of ACL strain without any lost of stability of the knee joint. For sonography we found a sensitivity of 96.1% and a fairly good specificity of 75.2%. Therefore, ultrasound examination of the femoral insertion of the ACL in knee joints with posttraumatic hemarthrosis can exclude a complete rupture of the ACL relatively precisely. Positive findings should be arthroscopically verified before carrying out arthrotomy. Sonography of the ACL insertion is a noninvasive examination that causes little discomfort to the patient and takes about 5-10 minutes. With our results we can demonstrate that the sonography of the femoral insertion of the ACL is a valuable screening method and restricts the necessity for early arthroscopy in hemarthrotic knee joints.