Accelerated endochondral growth in adolescents with idiopathic scoliosis: a preliminary histomorphometric study

BACKGROUND Abnormal longitudinal growth has been identified in the early pubertal stage of idiopathic scoliosis (IS) and is thought to contribute to the development of scoliosis. This phenotype may be caused by abnormal endochondral ossification, but histological evidence is lacking. The aim of this study was to investigate whether there is abnormal endochondral ossification in IS patients at early stage of puberty by histomorphometric analysis of their iliac cartilage. METHODS Fifty-two patients with IS and 19 controls were recruited and grouped according to their Risser grade (Group A: Risser grade 0 with Oxford stage 2-3; Group B: Risser grade 2). Group A consisted of 20 IS patients (mean age: 12.3 years) and 9 controls (mean age: 12.0 years), while Group B included 32 IS patients (mean age: 13.8 years) and 10 controls (mean age: 13.7 years). Biopsies of the iliac cartilage were harvested intra-operatively and prepared using routine histological methods. Histomorphometric analysis was performed to quantify the thickness of the hypertrophic zone, the area and number of chondrocytes in the cell-nest, and the number of chondrocytes in the proliferative zone using Image-Pro Plus software. RESULTS In Group A, a significantly thicker hypertrophic zone and larger cell-nest area and number of cells within the cell-nest, and in the proliferative zone, were found in iliac cartilages from IS patients compared with those of controls (all P < 0.05). In group B however, there were no significant differences in histomorphometric parameters between IS patients and the controls. CONCLUSIONS The differences in the histomorphometric results between IS patients and their controls for patients with Risser grade 0 and Oxford grades 2 & 3, but not in those with Risser grade 2, indicated a pattern of accelerated endochondral growth in IS at the early stage of puberty, but not at the late stage. TRIAL REGISTRATION Current Controlled Trials: ChiCTR-CCC-13003988. Registered 17 December 2013. http://www.chictr.org/usercenter/project/edit.aspx?proj=6233.