Blood flow measurement in reconstructed anterior cruciate ligaments using laser Doppler flowmetry

Laser Doppler flowmetry (LDF) was used to measure blood flow in anterior cruciate ligaments (ACL) reconstructed using a bone-patellar tendon-bone autograft. Thirty-five patients (17 men, 18 women) undergoing second-look arthroscopy for a reconstructed ACL were selected at random for postoperative participation in the study at 6, 12, and 18 months. Eight patients with an intact ACL had their blood flow measured arthroscopically for a control. Under arthroscopic visualization, a 3 mm probe was placed through a trocar sleeve into the ACL. Functional flow was evaluated using LDF, for which the output signal, the blood cell flux (BCF), is expressed in terms of volts. These patients also underwent magnetic resonance imaging (MRI); MRI, IKDC final evaluation, and second-look arthroscopic findings for each patient were compared with the others. In normal ACL, the BCF value ranged from 120 to 130 mV, and synovial blood flow, 90-132 mV. Significantly high BCF values for the reconstructed ACL were noted at 6 and 12 months, but there was no change in synovial BCF postoperatively. There was a gradual return to near normal BCF values for the reconstructed ACL 18 months after surgery. Significantly abnormal BCF values (580 ± 20 mV) were seen in cases with a severely abnormal IKDC final evaluation; there were few differences in BCF values between normal, nearly normal, and abnormal. LDF is easy to use and appears to be a reproducible technique for evaluating blood flow in the reconstructed ACL, offering distinct advantages for evaluating its maturation. Six months after surgery, there was a decrease in MRI with a high signal intensity, whereas the BCF values in the reconstructed ACL generally needed 18 months to return to near normal; the return was gradual. We believe the blood supply of the reconstructed ACL may originate from the synovium of posterior joint capsule within 6 months after surgery.