HISTOCHEMICAL ASPECTS OF THE PROTEOGLYCANS OF PATELLAR TENDON AUTOGRAFTS USED TO REPLACE THE POSTERIOR CRUCIATE LIGAMENT

In the female German black-faced sheep the posterior cruciate ligament was replaced by a free patellar tendon autograft and after 2, 6, 16, 26 and 52 weeks tissue samples of the graft's center (axial region far from bones) were removed for histochemistry and electron microscopy. To localize the proteoglycans Alcian Blue and 0.3 M MgCl2 were added t o the fixative solution. The distribution of the proteoglycans in the graft was compared to that of a normal patellar tendon and of a normal posterior cruciate ligament. In the patellar tendon spindle-shaped ce lls predominated and proteoglycans appeared as short filaments at regu lar intervals between the collagen fibrils. In the posterior cruciate ligament chondroid cells and long filaments in a net-work-like arrange ment were seen. In the patellar tendon autografts short interfibrillar filaments prevailed after 2, 6 and 16 weeks. After 26 weeks and parti cularly after 52 weeks long filaments also appeared. Digestion with Ch ondroitinase ABC, AC and Hyaluronidase suggested that the short filame nts were PGs containing dermatan sulfate. In grafts, in the early phas es the fibroblasts predominated, while in the late phases mainly chond roid cells were observed. The grafts showed aspects of the normal post erior cruciate ligament. However, differences remained, for example th e thin collagen fibrils, which could represent one of the reasons for a secondary graft failure.