Hump height in idiopathic scoliosis measured using a humpmeter in growing subjects: the relationship between the hump height and the Cobb angle and the effect of age on the hump height

BACKGROUND: The comparison between Cobb angle and hump height measured using a humpmeter in idiopathic scoliosis have produced contradictory findings concerning the association between the two variables in growing subjects. AIM: To analyze the relationship between the hump height and the Cobb angle and the effect of age on the first. DESIGN: Cross-sectional, descriptive analytical study. SETTING: A tertiary university hospital. POPULATION: One thousand two-hundred forty-five subjects with diagnosed idiopathic scoliosis or with a hump without spine deformity, aged between 3-21. METHODS: The hump was measured with subjects in a forward-bending position using a pocket humpmeter; the Cobb angle was determined on a traditional radiograph. A linear regression estimated the Cobb angle in relation to the hump height, and a multiple regression based on standardized regression coefficients (ß) and coefficients of determination (R2) assessed the contribution of age and the Cobb angle to hump variations. RESULTS AND CONCLUSIONS: The hump height was between 0-50 mm and the Cobb angle was between 0-78°. Based on regression coefficients, every unit (1 mm) increase in the thoracic/thoracolumbar and lumbar humps corresponded to an average increase in the Cobb angle of 1.542° (SE 0.037°; P=0.000) and 1.857° (SE 0.095°; P=0.000), respectively. The 95% confidence intervals for the estimated mean Cobb angles and those for the individual angles with respect to a given hump height lead to various hypotheses regarding the interconnection between the two entities. ß values for age were low with respect to ß values for the Cobb angle both at the thoracic level (0.095 vs. 0.807) and at the lumbar one (0.138 vs. 0.651), and R2, after the age-variable was excluded, decreased slightly from 70.3% to 69.4% and from 48.5% to 46.7%, respectively. Humpmeter measurements can thus be considered reliable in diagnosed idiopathic scoliosis and in asymmetric children - having a hump without deformity in spine - regardless of age. CLINICAL REHABILITATION IMPACT: Hump severity can be considered the balance needle when children with idiopathic scoliosis and asymmetric children are being treated and/or monitored. The humpmeter technique, coupled with Cobb angle measurement, can facilitate the clinical evaluation.