Experimental physial distraction was carried out in the distal part of the femur
in 45 two-month old lambs in order to study the basic mechanisms of lengthening
as well as the viability of the growth cartilage after using this method. The
animals were divided into three groups (A, B and C), and each group into three
subgroups (1, 2 and 3) according to the rate of distraction used (2 mm/day, 1
mm/day, 0.5 mm/day) and the time of sacrifice. The results obtained show that the
basic lengthening mechanisms consists, firstly, in the production of a fracture
between the metaphysis and the epiphysis and, secondly, that the lower the
distraction speed employed, the greater is the short-term and long-term viability
of the growth cartilage. Optimum viability was observed at a distraction rate of
0.5 mm/day. On this basis we conclude that in clinical practice physical
distraction could be indicated for children at an early stage of skeletal growth
and repeated later provided that the rate of distraction is kept within
reasonable limits
