E. RuTiSHAUSER ct al.: Experimental Studies of Vascular Pannus 63 



Experimental Studies of the Non-inflammatory Vascular Pannus 



E. RuTiSHAusER, W. Taillard, B. Friedli 

 Institut de Pathologic, Universite de Geneve, Geneve, Suisse. 



Ischemia produces a profound transformation of the vascularization of the osteo- 

 articular tissue. A vascular bud of tissue sprouts from the articular capsule and 

 becomes adherent to the cartilaginous surface (the surface or articular pannus). There 

 is stasis and arterial ischemia in the bone marrow, particularly pronounced at the epi- 

 physeal extremities, and the articular plate is invaded by histiocytic and vascular 

 buds which constitute the internal pannus. This phenomenon has already been 

 recognized in human pathology (Rutishauser, 1963), and the present paper is an 

 experimental contribution to its study. 



Material 



Series I: In 50 young adult rabbits, ischemia of the femoral bone marrow was 

 produced by injection of a carbon suspension into the femoral nutrient artery or by 

 intramedullary injection of a thrombin solution. The techniques used, and the dia- 

 physeal and metaphyseal lesions observed in these animals have been described 

 (Rutishauser et al., 1960). 



Series II: In 14 young adult rabbits, the lateral vascular connections of the 

 patella were severed along with the insertions of the vasti lateralis and medialis 

 (HuGUENiN-ViRCHAUX, to be published). 



Series III: The neck of the right femur and the sciatic nerve of 17 young adult 

 rabbits were severed. 



Results 



Series I: Both methods used in this series yielded identical results. In 35 of the 

 animals, the circulatory disturbances produced by the injection did not affect the 

 epiphyseal regions, and the joints remained normal. In the other 15, alterations in the 

 epiphyseal circulation were noted, and the joints also showed discrete but definite 

 changes. One animal (033), after 23 days, presented some of the most marked articu- 

 lar effects. There was a deepening of the coxo-femoral recesses, and the synovial villi 

 were characterized by congestion, edema, and proliferation of the synovial cells. The 

 congested periosteum invaded the cartilage, which presented a fuso-cellular meta- 

 plasia of chondrocytes. The terminal plate was partially destroyed (Fig. 1 a). 



This same rabbit also presented alterations in the distal femoral epiphysis. The 

 epiphyseal marrow and the cruciate ligaments were congested. From the bases of the 

 ligaments there were fibro-capillary expansions into the cartilage (Fig. 1 b). 



Fig. 2 a (103, 5 days) is an example of more discrete, though clearly noticeable, 

 articular alterations. Near the cruciate ligaments, vessels penetrated the terminal 

 plate, reached the cartilage, and provoked a fuso-cellular metaplasia. The edges of 

 the femoral cartilage were reduced by a border of fuso-cellular tissue which con- 

 tained small vessels. 



Series II: The patella was the site of vascular congestion and of active peri- and 

 endosteal resorption. The cartilage was eroded from the periphery by periosteal 



