[Value of osteo-chondral paste autologous transplantation in experimental cartilage defects reconstruction. Part IV--Microscopic analysis of cellularity and of traits of necrosis in the defect-filling tissue].

INTRODUCTION: Restricted potential of cartilage to regeneration following trauma induced search for new techniques of articular cartilage repair. Present study aimed at defining in experimental conditions of autologous osteochondral paste value by evaluation of cellularity and presence of necrosis in the defect-filling tissue.
MATERIAL AND METHODS: Full thickness defect (IV(o)--ICRS scale) on distal rabbit femur joint surface was made. Three groups were specified: A--defect with paste graft (cartilage and contiguous bone collected from joint surface, crushed into homogenous paste; B--defect with the paste graft covered with periosteum; C--defect left unfilled. The follow-up periods were established at 4, 8, 12 weeks. Repair tissue was evaluated microscopically according to modified O'Driscoll scale.
RESULTS: In evaluation of cellularity in the developed repair tissue, in long-term observations best results were obtained in the group of osteochondral paste (A) and in the group of unfilled defect (C). Following 12 weeks of observation cellularity of the repair tissue in the groups amounted to around 95%, as compared to the surrounding healthy cartilage. In evaluation of necrotic traits in the newly developed tissue, their highest intensity after 4 weeks of observation was noted in the group with periosteum covered osteochondral paste (B), and lower but still significant in the group in which paste alone was applied (A). This resulted from massive dying out of the grafted bone elements, and in the case of group B, also of the periosteal cells in the covering flap and of certain number of chondrocytes composing the graft. The trait was more objectively evaluated in long-term observations, when necrotic foci involved only elements of the proper repair tissue. After 12 weeks of observation degenerative changes showed the least pronounced intensity in the group with the paste alone (A). Following 4 weeks the intensity was least pronounced in the group with the unfilled defect (C), i.a. due to the absence of graft with the decomposing bone elements. However, with elapsing time degenerative lesions intensified in the group, pointing to the low stability of the developed tissue. The results indicated that application of the osteochondral paste in treatment of cartilage defects yields a stable, highly cellular tissue, resistant to time and trauma.