Platelet calmodulin levels in adolescent idiopathic scoliosis: Do the levels correlate with curve progression and severity?

Study Design. This ongoing longitudinal study evaluates simultaneous radiographic and platelet calmodulin determinations for patients with idiopathic scoliosis who are skeletally immature. Objectives. To determine whether platelet calmodulin levels correlate with curve progression and severity. Summary of Background Data. A previous study based on a single calmodulin determination and a single radiograph identified higher calmodulin levels in progressive curves and in higher magnitude curves. A longitudinal study was needed to demonstrate the relation of calmodulin to curve changes for individual patients over time during the growth period. Methods. In this study, 55 patients with idiopathic scoliosis of varying types and severity were followed longitudinally with serial radiographs and platelet calmodulin determinations. A Risser sign was recorded for each radiograph at each visit. Results. Calmodulin levels increased in all the patients with progressive curves (13/13), remained stable in 73% of the patients with nonprogressive curves (11/15), and were higher generally in curves greater than 30° and double structural curves. Calmodulin levels usually decreased in patients undergoing brace treatment (14/17) or spine fusion (9/10). Conclusions. It appears that platelet calmodulin levels correlate closely with curve progression and stabilization by bracing or spine fusion. Correlation with nonprogressive curves was not as consistent, with 27% noncorrelation. Longer follow-up evaluation and enrollment of additional patients will be necessary to determine whether calmodulin may serve as a biochemical marker of curve progression and to help identify stable and progressive curves.