Distribution of blood flow in normal and arthritic joints. Role of arteriovenous shunting studied in growing dogs.

Juvenile dog knee with chronic carrageenin-induced arthritis was studied under general anesthesia with 15-microns and 50-microns-sized microspheres (MS) to compare the distribution of absolute and weight-standardized blood flow in normal and arthritic limbs and to localize possible sites of arteriovenous (AV) shunting. Arthritic joints had severe synovial and capsular hyperemia. Absolute as well as standardized blood flow was increased in juxta-articular epiphyses and patella. Shafts were atrophic and had decreased absolute flow but normal standardized flow. However, redistribution of blood flow occurred among regions within the shafts, e.g., in metaphyses away from growth plates. The mean nonentrapment of 15-microns MS was 13.8% in arthritic limbs and 4.2% in control limbs. The uptake of 50-microns MS was lower than that of 15-microns MS in all bony flow compartments due to differences in their rheologic behavior in larger arteries. The relative distribution of 50-microns MS and 15-microns MS varied considerably among regions within bone. Arthritis caused a net shift in the uptake of 50-microns MS relative to that of 15-microns MS from central to subchondral epiphyseal bone, evidencing precapillary vasodilation, but the relationship was strictly unchanged when bones were examined in toto. This result militates against the hypothesis of AV shunting in arthritic bone.