[Experimental studies on the ossification of the posterior longitudinal ligament of the cervical spine]

Fluor, which is a natural substance contained in rice, vegetables, marine products and some seasonings, is assimilated into the body through ingestion. Approximately 60% of the total amount of this fluor intake would be based on rice. A histological study of cervical spine, knee ligaments, Achilles tendon and viscera of rabbits (approx. 12-16 weeks old) was made after injection with sodium fluoride in this study. The rabbits were divided into three groups: Group A (administered NaF 86.2 mg/kg, 5.7 mg/ml, 7 rabbits); Group B (administered NaF 31.5 mg/kg, 2.85 mg/ml, 6 rabbits) and a Control Group of 3 rabbits. Five rabbits in Group A (71.4%) and all six rabbits in Group B (100%) developed ossification of the posterior longitudinal ligament. Ossification of the yellow ligament was also found in two rabbits in Group A and one in Group B. No ossification was found in the Control Group. Both enchondral and intramembranous ossification were found in ossification of posterior longitudinal ossification in the rabbits.