Histopathological features of unilateral stapling in animal experiments.

Blount stapling of the proximal medial tibial growth was performed in 10-week-old domestic pigs. A total of 37 animals for up to 17 weeks were followed up. The histological evaluation showed a different reaction of the growth plate in the medial (stapled), central and lateral area. Up to 6 days after stapling the morphological features were characterized by deviations of the cell column from the axial alignment. Herniations of mature chondrocytes as well as isles of epiphyseal cartilage splintered into the adjacent metaphyseal cancellous bone were seen. From the 10th to the 11th postoperative day on there was a decline in the number of distal hypertrophic and degenerating cartilage cells due to impaired proliferation. Cell atrophy due to disturbed maturation or cell degeneration was evident. Local clusters of chondrocytes with loss of columnar arrangement indicated impaired chondrogenesis. Twenty-eight days after the operation coarser structures and changed alignment of cancellous bone characterized the morphological picture. The postoperative follow-up showed epiphyseal plates bounded by mature bone blocks or even a distinct sheet of horizontally oriented bone plates on the metaphyseal side. Many metaphyseal findings, such as augmented hypertrophic cells in the early postoperative period, or platelike limitations of the epiphyseal plate complete the morphological picture.