The periosteum in growth plate failure.

To investigate the periosteal contribution to the integrity of the growth plate, the authors subjected the proximal tibias of 110 male and female Sprague-Dawley rats between the ages of 25 and 65 days to axial and perpendicular forces to produce epiphysiolysis by use of a slow-loading technique and a cross-head speed of 10 mm per minute. Paired tibias of each rat were loaded under identical conditions, the only difference being the presence or absence of an intact periosteum. Mean values of body weight, tibial length, and cross-sectional areas of the growth plate after epiphysiolysis showed a linear increase with the age of the rat. No significant differences at the 5% level were observed in the tibial length and cross-sectional areas of the paired tibias. However, a consistently higher force was needed to produce epiphysiolysis with the periosteum intact. This was significant at all ages in both axial and perpendicular loading but was marked for young rats aged 45 days and under that were subjected to axial loading, where the level of significance was less than 1%. Calculated stress values showed a similar significant trend. The periosteum contributes significantly to the stiffness of the system, as shown by typical load deformation curves, and if it is divided, the gradient of the curve is clearly reduced up to epiphysiolysis. All periosteal fibers are not recruited in resisting a perpendicular force. Histologic examination of the specimens showed two patterns of failure corresponding to axial and perpendicular loading and also showed the failure path.