The influence of severity of angulatory deformity of rat's tibia on spontaneous correction.

In order to estimate the spontaneous correctability of tibial deformity, retrocurvature of various degrees in the growing rat tibia was observed roentgenologically at 2 to 3 weekly intervals for eight week periods. The results obtained were: in the retrocurvated rat tibia of groups I, II and III, 11.1 +/- 2.6%, 7.2 +/- 1.7% and 7.4 +/- 1.1% respectively of initial base angle were corrected in observation periods of between 3 to 8 weeks and the correction obtained between 3 to 5 weeks in groups I, II and III were 4.2 +/- 1.3 degrees (65.5%), 4.3 +/- 1.5 degrees (64.2%) and 5.0 +/- 1.3 degrees (67.9%), and between 5 to 8 weeks were 2.2 +/- 0.6 degrees (34.4%), 2.4 +/- 0.5 degrees (35.8%) and 2.7 +/- 0.9 degrees (32.1%), respectively. This study confirms that spontaneous correctability of deformed rat tibia decreased when the deformity is severe, and, irrespective of the severity of initial deformity, more than half of the initial base angles were corrected in an early phase, and remainders later. This fact indicates that the physeal and diaphyseal remodelling process is affected to some degree by the severity of the deformity.