Pins or nails passed diagonally across the epiphyseal cartilaginous plate prevent growth in length from that end of the bone. Such pins fix the epiphysis to the diaphysis and prevent the progression necessary for length growth. In check experiments in which the pins were removed immediately after insertion, no loss of growth resulted. This finding rules out the possibility that the loss of growth is due to primary injury to cartilage cells.
This method has not been applied to growing humans, but its relative simplicity may warrant its use in clinical cases of discrepancy in length of the lower extremities.
The question regarding the activity of cartilage cells after removal of the restricting device—wire loops, staples, crossed pins, or nails—has not been answered completely. In most of the experiments, there is evidence that the growth property of the plate is not so active as normal, and in some instances there is almost complete loss. In removing any of the devices, there is additional destruction of the circulation to the plate, damage to the plate itself, and the possibility of producing a bridge of bone across the plate. It is believed that a method which produces less injury at the time of removal will improve the results.
It is advisable to place markers in both the normal bone and that which has been operated upon, so as to have a record of the growth from each epiphyseal plate. In some experiments, there was evidence of compensatory growth from the non-restricted plate at the opposite end of the bone. In the human, markers should be placed on both the normal bone and that which has been operated upon, for accurate study of the relative amount of growth. Also, it is recommended that careful teleoroentgenograms or scanograms be taken to obtain exact growth indices and to rule out the possibility of inaccurate measurements.
Unilateral retardation of growth was produced when two pins were inserted so as to fix only half of the plate. Some restriction was noticed on the opposite side as well, causing shortening of the entire bone. There is also the possibility of permanently damaging that side of the plate, when removing the restraining device. If permanent injury has been produced, a deformity in the opposite direction may take place.
Pins or nails passed immediately above the epiphyseal plate caused some loss of length growth. The mechanism of this restriction may depend upon fixing of the periosteum, which secondarily may hinder, to some extent, the advancement of the epiphysis away from the metaphysis.
The experiments in which the pins or nails were passed longitudinally through the epiphyseal plate produced a rather surprising amount of growth restriction in some cases. The growth retardation was most marked when the pins approached the articular cartilage.