Impact of telescopic intramedullary rodding on the growing tibia: an experimental study

Introduction Telescopic intramedullary osteosynthesis (TIO) is used in children with osteogenesis imperfecta and other diseases accompanied by frequent fractures and deformities of long bones due to pathological bone tissue featuring reduced strength properties. Purpose In an animal experiment to study the growth characteristics of an intact tibia under conditions of intramedullary reinforcement with a telescopic rod. Material and methods A non‑randomized controlled study was conducted on 4 animals (puppies, littermates) that underwent TIO of the right limb tibia with a telescopic titanium rod (outer diameter of 4.2 mm) at the age of 5 months. X-ray parameters (length of the tibia, angles of inclination of the articular surfaces, telescoping magnitude) were studied before surgery, on the day of rod placement, and after the end of spontaneous growth of the segment (7 months after surgery). The contralateral left tibia served as a control, and its X-ray parameters were studied at the same time-points. Results Transphyseal reinforcement with a telescopic rod caused growth retardation with loss of length in only one case out of four (8 mm or 4.8 % of residual growth). In other cases, no difference in the length of the tibias of the right and left lower extremities was found. Eccentric insertion of the transphyseal rods into the posterior third of the distal epiphysis (due to the natural anatomy of the canine tibial shaft) formed an angular deformity during growth: a significant increase in the distal anterior and lateral tibial angles of the operated limb compared to the intact limb. The amount of divergenceof the parts of the rods was, on average, 11.3 mm. There were no cases of migration of intramedullary rods or loss of fixation of threaded sections in the epiphyses. Conclusion Under experimental conditions, the slowing down of longitudinal bone growth is not a constantly observed effect. Titanium telescopic rods are not prone to blocking during the limb growth or to losing the position of the threaded parts in the epiphyses. The eccentric passage of the rods through the growth zones causes angular deformities in the course of growth of the segment.