Hump height in idiopathic scoliosis measured using a humpmeter in growing subjects: 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 (beta) and coefficients of determination (R-2) assessed the contribution of age and the Cobb angle to hump variations. RESULTS: The hump height was between 0-50 mm and the Cobb angle was between 0-78 degrees. 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 degrees (SE 0.037 degrees; P=0.000) and 1.857 degrees (SE 0.095 degrees; 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. beta values for age were low with respect to beta 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. CONCLUSIONS: 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.