CHANGES IN THE EXTRACELLULAR-MATRIX OF THE AUTOGENOUS PATELLAR TENDONGRAFT AFTER POSTERIOR CRUCIATE LIGAMENT RECONSTRUCTION - A BIOCHEMICAL-STUDY IN SHEEP

The left knee joints of female German sheep were operated, replacing t he posterior cruciate ligament by the central third of the patellar te ndon. After 2, 6, 16, 26 and 52 weeks the graft of the operated leg as well as the contralateral central third of the patellar tendon and th e posterior cruciate ligament were dissected and used for biochemical analysis. The total glycosaminoglycan content in grafts increases with in the first pear up to 5 fold and is higher than that of the patellar tendon, but is lower than that of the cruciate ligament. The distribu tion pattern of glycosaminoglycans differ in the posterior cruciate li gament and the patellar tendon. In cruciate ligament the main componen ts are chondroitin sulfate (76%) and hyaluronan (15%). In the patellar tendon a higher portion of dermatan sulfate (approx. 16%) was found, next to 52% chondroitin sulfate and 22% hyaluronan. During the examina tion time the grafts show changes in the concentration and the distrib ution pattern of glycosaminoglycans. The chondroitin sulfate content i ncreases during the experimen tal period from 1.4 +/- 1.2 mu mol/g dry weight (d.w.) to 8.7 +/- 2.9 mu mol/g d.w. After 1 year the chondroit in sulfate content in the graft does not differ significantly from tha t of the cruciate ligament. In the grafts the concentration of chondro itin (non sulfated) increases after 6 weeks up to 1.3 +/- 0.6 mu mol/g d.w. in comparison to the value after 2 weeks (0.2 +/- 0.1 mu mol/g d .w.) and also in the other groups (16, 26 and 52 weeks) it remains sig nificantly increased. After 1 year the dermatan sulfate content in the graft has increased up to the fifth-fold compared to the value after 2 weeks and is higher than in the patellar tendon and in the cruciate ligament. In graft the hyaluronan content (1.0 +/- 0.4 mu mol/g d.w. d oes not differ significantly in the groups 2, 6, 16, 26 and 52 weeks a fter operation, but in all five groups it is lower than in the cruciat e ligament (2.4 +/- 1.0 mu mol/g d.w.). Dermatan and heparan sulfate a re not or only little detected in all three tissues. The distribution pattern of glycosaminoglycans in graft shows chondroitin sulfate and d ermatan sulfate being the major parts of glycosaminoglycans with a sli ght increase of these components in the different groups during the ex perimental period. Hyaluronan makes up to 24 +/- 5% of the whole conte nt of glycosaminoglycans after 2 weeks and decrease to 8 +/- 1% after 52 weeks. From 6th to 52th week the portion of hyaluronan in grafts is lower than in patellar tendons and cruciate ligaments. In grafts the portion of keratan sulfate decreases after 26 weeks from the value aft er 2 weeks, but is even higher than in cruciate ligament and patellar tendon. These changes of glycosaminoglycans could be an indication mar k for an adjustment of the graft to the intraarticular milieu and to t he new function as a cruciate ligament reconstruction.