Indirect signs of anterior cruciate ligament injury on SPET: Comparison with MRI and arthroscopy

Indirect signs of anterior cruciate ligament (ACL) injury on magnetic reson ance imaging (MRI) include bony contusions in the lateral femoral condyle a nd the posterior portion of the lateral tibial plateau. This study was unde rtaken to assess the value of single photon emission tomography (SPET) in t he diagnosis of ACL injury by examining the uptake pattern in the distal fe mur and the proximal tibia. Thirty-five patients were examined using SPET, MRI and arthroscopy. Seventeen patients were found to have ACL tears on art hroscopy. The duration of symptoms was 4 days to 10 years (mean 26.4 months ). MRI and SPET images were analysed retrospectively without information fr om arthroscopic examination. Radionuclide uptake in the lateral femoral con dyle and the posterior lateral tibial plateau was considered an indirect si gn of ACL injury on SPET. We evaluated the diagnostic value of indirect sig ns of ACL injury obtained on SPET by comparing these findings with arthrosc opic and MRI results. Fifteen of 17 patients with ACL injury showed indirec t signs on SPET. The sensitivity, specificity, positive predictive value an d negative predictive value for indirect signs of ACL injury were 88%, 56%, 65% and 83% on SPET and 59%, 94%, 91% and 71% on MRI, respectively. Howeve r, despite the higher sensitivity of indirect signs on SPET than on MRI, th e overall diagnostic value of MRI is better than that of SPET. In the clini cal setting, indirect signs of ACL injury may be of value in interpreting i ncidental findings on SPET. ((C) 2000 Lippincott Williams & Wilkins).