Skeletal age assessment from the olecranon for idiopathic scoliosis at risser grade 0

Background: The main progression of idiopathic scoliosis occurs during peak height growth velocity, which is between the ages of eleven and thirteen years in girls and thirteen and fifteen years in boys and corresponds to the accelerating phase of pubertal growth. The Risser sign remains at grade 0 during this stage of growth. Triradiate cartilage closure occurs at approximately twelve years of age in girls and fourteen years in boys, which is in the middle of this phase. In addition to regular height measurements, a more detailed evaluation of skeletal maturity would be desirable prior to the identification of Risser grade 1. From the method of Sauvegrain et al., Dimeglio derived a simplified method based on the radiographic appearance of the olecranon, which allows skeletal age to be assessed in six-month intervals. The purpose of this study was to determine the accuracy and the value of this simple method for the follow-up of patients with scoliosis. Methods: Five radiographic images demonstrate the typical characteristics of the olecranon during pubertal growth: two ossification nuclei, a half-moon image, a rectangular shape, the beginning of fusion, and complete fusion. This classification method was evaluated by three experienced and independent observers from lateral radiographs of the elbow in 100 boys and 100 girls with idiopathic scoliosis during the time of peak height velocity. Skeletal ages were correlated with the integral Sauvegrain method. The degree of interobserver concordance was determined, and skeletal age was compared with chronological age and the time of triradiate cartilage closure. Results: For the three observers, the average concordance between the Sauvegrain and olecranon methods was excellent (r = 0.977 for boys and r = 0.938 for girls). The interobserver agreement was also excellent (r = 0.987 for the olecranon method and r = 0.958 for the Sauvegrain method for boys, and r = 0.992 and r = 0.985, respectively, for girls). Skeletal and chronological age were considered to correspond to each other within a six-month range for 49% of the boys and 51% of the girls, while 25% of the boys and 26% of the girls had an advanced skeletal age and 26% of boys and 23% of girls had a delayed skeletal age. Triradiate cartilage closure occurred at the same time as the appearance of the rectangular shape of the olecranon in 65% of the boys and 61% of the girls, corresponding to skeletal ages of fourteen and twelve years, respectively. In 91% of the boys and 88% of the girls, the triradiate cartilage fused within six months before to six months after the appearance of the rectangular shape of the olecranon, which occurred between the half-moon image and the beginning of fusion of the olecranon. Conclusions: The method of assessing skeletal age from the olecranon allows skeletal maturity to be evaluated in regular six-month intervals during the phase of peak height velocity. This method is simple, precise, and reliable. It complements the Risser grade-O and the triradiate cartilage evaluation.