Chondrocyte injection in distraction epiphysiolysis (rabbit model).
The purpose of this study was to determine if cultured chondrocytes could prevent premature closure of the physis after physeal distraction in a rabbit model. Epiphyseal distraction at the proximal tibial epiphysis was performed in 24 immature rabbits. Chondrocytes were harvested from the iliac apophysis. The animals were divided into three groups: A, epiphyseal distraction alone; B, injection of phosphate buffered saline (PBS) after epiphyseal distraction; and C, injection of cultured chondrocytes after epiphyseal distraction. After epiphyseal separation was noted radiographically, each animal was evaluated at routine intervals. At 2 to 4 weeks, significant tibial lengthening as compared to the contralateral tibia was noted in all three groups. At 10 weeks, lengthening was apparent only in group C; in groups A and B, the operated tibia was shorter than the unoperated one. Histologic examination at 4 weeks revealed partial bony bridge formation with cell clustering in the fibrocartilaginous matrix in groups A and B. In group C, the matrix showed a typical hyaline aspect with cells organized in columns at the injection site. The zone of hypertrophic chondrocytes was enlarged. It appears that the injected cells differentiated into hypertrophic chondrocytes and delayed premature physeal closure. At 10 weeks after distraction of the physis, the width of the physis was restored to 75% of normal, but disordered chondrocyte growth with cell clustering was present in the cell-injected group.