Aim: Investigations on human hyaline cartilage of late stage degenerative arthritis showed that the vascular derived endothelian growth factor (VEGF) seems to play a role in the development of degenerative arthritis. The current study was designed to evaluate the expression of VEGF on chondrocytes of hyaline cartilage in the time course of degenerative arthritis.

Methods: In twelve white new-zealand-rabbits the anterior cruciate ligament was resected to create an anterior instability of the knee. In twelve control rabbits only a sham operation without resection of the ACL was done. Another four animals have not been operated at all (0 weeks). Four animals of each group were sacrificed at three, six and twelve weeks each. After opening of the knee joint, the degenerative arthritis was macroscopically graded and the hyaline cartilage of the load bearing area was evaluated histologically according to Mankin and by immunostaining for VEGF.

Results: The macroscopic and histological grade of degenerative arthritis according to Mankin showed a positive linear correlation to the time after surgery. The scores of the control group were constant in the time course. In the cartilage of the untreated animals (0 weeks) an average of 12 percent (SD 2.6) VEGF-positive chondrocytes were found. After 3 weeks the trial group (17.6%; SD 5.7) as well as the control group showed a significant increase (16.2%; SD 4.7). After 6 weeks the value in the control group dropped to normal (11.5%; SD 5.9) and remained constant after 12 weeks (11.6%; SD 3.3). In the trial group the percentage of VEGF positive chondrocytes rose steadily (19.4%; SD 4.6 after 6 weeks; 21.3%; SD 5.4 after 12 weeks). There was a positive linear correlation between the percentage of VEGF positive cells and the Mankin score (r=0.767; p< 0.01) and the macroscopic score (r=0.518; p=0.02).

Conclusion: The current study shows for the first time an in-vivo increase of VEGF expression on chondrocytes in the time course of osteoarthritis, which is dependent on macroscopic and histological grades. Further studies are needed to evaluate whether this pattern applies to human beings and whether new treatment approaches could evolve from this knowledge.

Aim: Previous investigations have shown the vital role of chondrocyte CD44 in cartilage homeostasis and matrix attachment and indicated a participation of CD44v5 in the development of osteoarthritis. However, all reports dealt with late stage human osteoarthritis, as human specimens are only available at the time of surgery. Thus, little is known about the expression of CD44v5 in the time course of osteoarthritis. The current study was designed to evaluate the expression of CD44v5 on chondrocytes of hyaline cartilage in the time course of osteoarthritis.

Methods: In twelve white new-zealand-rabbits the anterior cruciate ligament was resected to create an anterior instability of the knee. In twelve control rabbits only a sham operation without resection of the ACL was done. Four animals of each group were sacrificed at three, six and twelve weeks each. After opening of the knee joint, osteoarthritis was macroscopically graded and hyaline cartilage of the load bearing area was evaluated histologically according to Mankin and by immunostaining for CD44v5.

Results: In the trial group, macroscopic and histological grades of OA showed a positive linear correlation to the time after surgery. Immunostaining showed an increased expression of CD44v5 in the control group after 3 and 6 weeks, which dropped to normal after twelve weeks. There was no difference between control and trial groups after 3 and 6 weeks, but after 12 weeks. We found a significant positive correlation between CD44v5-expression and macroscopic (r=0.294) and histological (r=0.314) grades of OA.

Conclusion: The current study shows in-vivo an increase of expression of the hyaluronan receptor CD44v5 in the time course of osteoarthritis. Further studies are needed to evaluate whether this pattern applies to human beings and whether new treatment approaches could evolve from this knowledge.

Despite widespread use of radiofrequency (RF) shrinkage, there have been no animal studies on the effects of post-operative immobilisation on the histological properties of the shrunken tissue. We have therefore examined the role of post-operative immobilisation after RF shrinkage with special emphasis on the histological properties of collagenous tissue.

One patellar tendon of 66 New Zealand White rabbits was shrunk. Six rabbits were killed immediately after the operation. Twenty rabbits were not immobilised, 20 were immobilised for three weeks and 20 for six weeks. Fibroblasts, collagen and vascular quality and density were evaluated on sections, stained by haematoxylin and eosin.

Nine weeks after operation the histological properties were inferior to those of the contralateral control tendons. Shrunk tendons did not return to normal at any time after operation irrespective of whether the animals had been immobilised or not. All the parameters improved significantly between zero and three weeks after operation. Immobilised tendons tended to have a better and faster recovery.

Careful rehabilitation is imperative after RF shrinkage. Immobilisation aids recovery of the histological properties. Our findings in this animal model support a period of immobilisation of more than three weeks.

Aims: In recent years more and more studies tried to evaluate possible inßuences of different growth factors on hyaline cartilage regeneration. In a rabbit model, HGF (hepatocyte growth factor) was proven to increase the amount of hyaline-like chondrocytes in a mixed þbrocartilaginous regenerate of small defects. The present study was undertaken to evaluate, whether intraarticular administration of hepatocyte growth factor inßuences the ingrowth of osteochondral grafts in a sheep model. Methods: Both knee joints of a sheep were opened surgically and osteochondral grafts were harvested and simultaneously transplanted to the contralateral compartment. The sheeps were divided into two groups. In one group hepatocyte growth factor was administered by intraarticular injections given three times a week for four weeks. The control group received isotonic sodium chloride injections. The animals were sacriþced after three months and the received knee joints were evaluated histologically. Results: Histological evaluation showed that the autologous osteochondral grafts were healed in at the level of the subchondral bone. A healing or ingrowth at the level of the cartilage could not be observed. Anyway, histological evaluation of the transplanted grafts according to Mankin showed, that the cartilage of the HGF group showed less signs of degeneration than the control group. In the HGF group less cloning of chondrocytes and less irregularities of the articular surface were observed. Conclusion: In conclusion, HGF positively inßuenced the structure of the transplanted osteochondral graft, but could not diminish the þssures in the marginal zone of the grafts.