Abstract: Objective To investigate the distribution of hyaluronic acid (HA) with iohexol tracing in the knee joint cavity of
rabbits using CT plain scan, three-dimensional reconstruction and X-ray and observe how different injection sites affect HA
distribution. Methods Mixtures of HA and iohexol (tracer) were prepared that contained final iohexol concentrations of 2.5%,
5%, 10%, 20%, or 40%. The HA-iohexol mixtures (0.5 ml) were injected into rabbit knee joints, and the optimal iohexol
concentration that allowed clear differentiation of the injected agents from the surrounding tissues was determined using
dual-source CT plain scan and three-dimensional reconstruction technique. The HA-iohexol mixture (0.5 ml) containing the
optimal concentration of iohexol was then injected into the knees of the rabbits either through the patella medial approach or
the medial joint line approach, and HA distribution in the knee joint cavity was observed using CT scan and X-ray. Results The
CT value of HA-iohexol mixture increased progressively with the tracer concentration. After injection of the mixture
containing 2.5%, 5%, 10%, 20%, and 40% iohexol, the CT value ratios of the soft tissue, HA-iohexol mixture and bone cortex
were 2∶7∶46, 2∶14∶44, 2∶28∶44, 2∶60∶46, and 2∶98∶45, respectively, and a iohexol concentration of 5% was determined as
optimal for differntiating the injected agents from the surrounding tissues. The HA-iohexol mixutre containing 5% iohexol
injected through the medial-patellar approach was distributed mainly over the patello-femoral joint, and that injected through
the joint line approach was found mainly over the tibio-femoral joint. Conclusion HA-iohexol mixture containing 5% iohexol
allows clear differentiation of bone cortex and soft tissues in rabit knee joint from the injected agents on CT scan and X-ray, and
the injection approach can influence HAdistribution in the knee joint cavity.