An experimental study on injuries to the growth plate--effects on the growth of long bones following placement of smooth pins across the growth plate of immature rabbits
Kameyama, M.
Nihon Seikeigeka Gakkai Zasshi 67(7): 662-676
1993
ISSN/ISBN: 0021-5325 PMID: 8409636 Document Number: 409549
Displaced epiphyseal separation is difficult to reduce and fix. We usually pass a few Kirschner wires from the epiphysis to the metaphysis to maintain the position of reduction. However there are various opinions about the effects of penetrating smooth pins, concerning whether it causes retarded bone growth. In this experimental study on immature rabbits, stainless steel pins 0.7, 1.2, 2.0, or 3.5 mm in diameter or a single crystal alumina ceramic pin 1.2 mm in diameter were driven into a drill hole of equivalent bore in the intercondylar portion of the right femur across the central portion of the growth plate. Using this model, we analyzed effects on the growth plate and bone growth macroscopically, radiographically and histologically. The follow-up intervals were 3, 6, 12 and 24 weeks. At 12 and 24 weeks after insertion of the 3.5 mm stainless steel pin, shortening of the operated femur was observed. In other groups there was no difference in the length of the femur. The pin position after insertion was divided into two types; in one the pin position remained located in the growth plate, and in the other the pin migrated proximally beyond the growth plate. Histologic studies showed regenerated growth cartilage in the implant canal at the plane of the growth plate. At 12 weeks after insertion of a 3.5 mm stainless steel pin there was bone bridge between epiphysis and metaphysis without clear regenerated growth cartilage. The role of regenerated growth cartilage, therefore, appears to prevent bone bridge formation. There was no significant difference between the stainless steel pin and the single crystal alumina ceramic pin. When the diameter of the pin is sufficiently large and also low growth plate activity due to aging is present, retarded bone growth would be anticipated.