In vivo monitoring of circulation in the intact anterior cruciate ligament using the laser Doppler flowmeter.

Laser Doppler flowmetry permits observation of circulation in the microcapillary regions of structures under in vivo conditions. We used a laser device manufactured by the Swedish company Perimed and a special probe to observe the capillary circulation in the anterior cruciate ligament during arthroscopic surgery. This produces measured values in millivolts; these values are relative in nature and cannot be used to determine an absolute value for capillary circulation by volume per unit time. Under standardized conditions, circulation measurements and simultaneous recordings with a two-channel recorder were made from 11 patients. In all cases, pulsations of the capillary circulation synchronous with the heart beat could be seen on three measuring points on the anterior cruciate ligament; these disappeared upon complete deprivation of blood supply. We found a large individual range of variation in the so-called blood cell flux values from 30 to 620 mV. The magnitude of the heart-synchronous pulsations ranged between 20 and 240 mV. Only vague linear relationships were found (a) between the individual measuring points and (b) between the flux values and the magnitude of pulsation; there was no relationship between the flux values and blood pressure and/or red blood count (erythrocyte count, hemoglobin, hematocrit).