Peak Height Velocity as a Predictor of Curve Progression in Idiopathic Scoliosis

Summary: Peak height velocity (PHV) has been shown to be a significant predictor of scoliosis curve progression. A retrospective review identified 55 adolescent females with idiopathic scoliosis and curves between 20 and 45º. We found that 30º of curvature at PHV is a significant predictive indicator for curve progression to a surgical magnitude. Menarche and Risser grade lag behind PHV. PHV is a more accurate predictor of time of maximal curve progression than the other variables.

Introduction: Peak height velocity (PHV) is a significant predictor of scoliosis curve progression. This study hypothesizes: 1) PHV accurately predicts the timing of maximal curve progression 2) curves greater than 30º at PHV progress to surgical indications.

Methods: A retrospective review identified 55 adolescent females with idiopathic scoliosis and curves between 20 and 45º. Data included: age, height, menarche, Risser grade, and Cobb angle. Progression to surgical magnitude was defined as progression of 10° to 45º. Regression analysis, F-test for variance, and t-test were used for analysis.

Results: Fifty-five patients were followed for a minimum of 2.5 years with an average follow-up of 4.8 years. Fifty curves progressed. Mean PHV was 8.9 cm/yr. Cessation of growth occurred an average of 2.4 years after PHV. Menarche and Risser 1 lagged behind PHV by 4 and 11 months respectively. Maximal curve progression was assessed in relationship to PHV, Risser grade, and menarche in 33 of the 55 patients. PHV grouped patients better for maximal curve progression than either menarche or Risser. 49% (16/33) underwent maximal progression while still at Risser 0, and 15% while at Risser 4. 25 of 28 (89%) patients with curves greater than 30º at PHV progressed to surgical indications. 3 of 22 (14%) that were less than 30º at PHV progressed to surgical indications (p <.0001; sensitivity 89%; specificity 86%; accuracy 88%). 30º curvature before menarche was a sensitive (100%), but less specific (41%), and less accurate (74%) predictor of progression to 45º.

Discussion: 30º of curvature at PHV is a significant predictive indicator for curve progression to a surgical magnitude. Menarche and Risser grade lag behind PHV. PHV is a more accurate predictor of time of maximal curve progression than the other variables.