E-PTFE IN RABBIT KNEE-JOINTS

The healing of expanded polytetrafluoroethylene (e-PTFE) in articular cartilage and bone was studied. A 1 x 4 mm osteo-chondral defect was c reated in the medial femoral condyle in 10 rabbits (20 knee-joints). A correspondingly broad strip of e-PTFE was placed in the defects and p ulled through two drilled channels to the dorso-lateral side of the co ndyle. The contra-lateral knee-joint served as control. The animals we re not immobilized and allowed to move about freely together in a room . The animals were killed by perfusion fixation after 14 months, the i mplants and tissues retrieved en bloc and examined with scanning elect ron microscopy (SEM) and light microscopic (LM) morphometry. No macros copic signs of inflammation were detected in the knee-joints. Observat ions with SEM in control joints showed that the articular surface rang ed from smooth to irregular with superficial crevices and fibrillation s at the site of the defect. The smooth articular surface of the surro unding articular cartilage partly overlapped the e-PTFE membrane. The surface of the e-PTFE membrane had a nodular character and was surroun ded by fibrocartilage with clusters of chondrocytes. A consistent obse rvation was the large amount of bone around and in direct contact with the surface of e-PTFE membrane. LM morphometry of intact e-PTFE-tissu e specimens in three different section planes showed that 73.1% and 8. 8% of the implant surface was in contact with bone and bone marrow, re spectively. Our morphological observations of e-PTFE in the cartilage and bone of the rabbit knee-joint after a 14-months healing period ind icate that e-PTFE could be a useful material in reconstructive surgery of smaller non-weight-bearing joints.