[Importance of ultrasound in postoperative follow-up after reconstruction of the anterior cruciate ligament].

Eighty-eight male patients following reconstruction of the anterior cruciate ligament (ACL; mean 24 months since operation) had a thorough clinical examination including instrumented measurement of laxity using the KT 1000. These results were correlated with an ultrasound (US) grading that evaluates the reconstruction itself as well as its functional behaviour during the anterior drawer test. Thirty-four magnetic resonance (MR) studies of 33 patients were available. Undoubtedly postoperative visualization of the reconstructed ACL is superior to that of both normal control ACL and acute trauma cases. Especially operative procedures which use the patellar or semitendinosus tendon lend themselves to accurate evaluation of the intraarticular reconstruction. The sensitivity, specificity, positive and negative predictive values and overall accuracy of US/MR versus the clinical laxity measurement are calculated to be 66.7%/96.0%, 71.2%%/23.8%, 59.5%/60.0%, 77.1%/83.3% and 69.4%/63.0% respectively. US has a satisfactory diagnostic value and performs similarly well on all these parameters. MR, on the other hand, correctly diagnoses nearly all unstable knees but is associated with a high number of false positives. There is no statistically significant, linear correlation between MR and US; r = -0.0769, P = 0.6706. Only three times did the reconstructed ACL appear normal on MR, whereas 48.5% of the reconstructions were graded type I (normal) on US. Clinical Consequences: Ultrasound and MRT should not be considered rival but rather complementary methods: ultrasound is a good method for documenting changes within the knee joint on an outpatient basis, while the indications for MR in the postoperative course are any occurrences of pain, instability or reinjury.