Maturity Assessment and Curve Progression in Girls with Idiopathic Scoliosis

Background: Scoliosis progression during adolescence is closely related to patient maturity. Being multidimensional, maturity includes various components including chronological age, height and weight changes, skeletal and sexual maturation. It is not certain which of these dimensions correlates most strongly with scoliosis behavior. This study's purpose is to evaluate various maturity measurements relative to scoliosis progression.

Methods: Physically immature girls with idiopathic scoliosis were followed every six months through their growth period with serial spinal radiographs, hand skeletal ages, Oxford pelvic scores, Risser sign determinations, heights, weights, sexual staging and serologic studies of IGF-1, IGFBP-3, DHEA-s, estradiol, bone specific alkaline phosphatase and osteocalcin levels. These measurements were then correlated with the curve acceleration phase (CAP).

Results: The period and pattern of curve acceleration began during Risser 0 for all patients. Skeletal maturation using the Tanner-Whiteside III (TWIII) RUS method, particularly of the metacarpals and phalanges, was superior to all other dimensions of maturity determination. Regression of the scores allows good estimates of maturity during the period of curve progression (Pearson r=0.93). The initiation of this period occurs simultaneously with digital changes from TWIII stage F to G or covered to capped. At this stage curves also separate into rapid, moderate, and low acceleration patterns with specific curve types for the rapid (Lenke 1 and 3) and moderate groups (Lenke 2, 4, 5, and 6) with distinct prognosis. The low acceleration group is not confined to a specific curve type.

Conclusions: The curve acceleration phase (CAP) separates curves into various types of curve progression with differing prognosis. The TWIII RUS scores are highly correlated with timing relative to the CAP and provide better maturity determination and earlier prognosis during adolescence than the other parameters tested. Accurate skeletal maturity determination should be used as the primary maturity measurement in girls with idiopathic scoliosis.