[Experimental study of tangential osteochondral and chondral fracture of the patella]

It has been reported that trauma is not an only responsible factor for tangential osteochondral fracture (OF) in the patellofemoral joint, but other factors predisposing to OF are also involved in many clinical cases. The present investigator manually dislocated the patella of 25 young rabbits without anesthesia (group 1). In other 25 young rabbits (group 2), dislocation of the patella followed the experimental production of the patellar subluxation which was considered as an etiology of OF. The resulting patellar cartilage changes were compared between these groups of rabbits to clarify the relation between the preceding cartilage change and the development of OF. As a result, the present study confirmed that OF was not caused by mere dislocation of the patella but was induced only when dislocation was superimposed on an existing cartilage change resulting from the patellar subluxation. In treating clinical cases of OF, it is, therefore, important to evaluate cartilageous degeneration thoroughly and clarify its pathologic process.