E-PTFE in rabbit knee-joints

The healing of expanded polytetrafluoroethylene (e-PTFE) in articular cartilage and bone was studied. A 1×4 mm osteo-chondral defect was created in the medial femoral condyle in 10 rabbits (20 knee-joints). A correspondingly broad strip of e-PTFE was placed in the defects and pulled through two drilled channels to the dorso-lateral side of the condyle. The contra-lateral knee-joint served as control. The animals were not immobilized and allowed to move about freely together in a room. The animals were killed by perfusion fixation after 14 months, the implants and tissues retrieved en bloc and examined with scanning electron microscopy (SEM) and light microscopic (LM) morphometry. No macroscopic signs of inflammation were detected in the knee-joints. Observations with SEM in control joints showed that the articular surface ranged from smooth to irregular with superficial crevices and fibrillations at the site of the defect. The smooth articular surface of the surrounding articular cartilage partly overlapped the e-PTFE membrane. The surface of the e-PTFE membrane had a nodular character and was surrounded by fibrocartilage with clusters of chondrocytes. A consistentobservation was the large amount of bone around and in direct contact with the surface of e-PTFE membrane. LM morphometry of intace e-PTFE-tissue 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, respectively. Our morphological observations of e-PTFE in the cartilage and bone of the rabbit knee-joint after a 14-months healing period indicate that e-PTFE could be a useful material in reconstructive surgery of smaller non-weight-bearing joints.