The Change of Cobb Angle According To Position in Adolescent Idiopathic Scoliosis / 대한척추외과학회지

ABSTRACT

STUDY DESIGN: Consecutive, prospective, radiographic review of adolescent idiopathic scoliosis (AIS) patients. OBJECTIVE: To analyze the change of Cobb angle according to position in AIS. SUMMARY OF BACKGROUND DATA Cobb angle on standing radiographs was corrected spontaneously while the patients were in the supine position. However, there are few reports on Cobb angle in standing versus supine position in AIS. MATERIALS AND METHODS: We checked AP plain radiographs of 101 AIS patients, 18 male and 83 female, in standing and supine position. Sixty-three cases were under Risser stage V and 38 were Risser stage V. In standing plain radiograph, 27 cases were in Cobb angle 10-19 degrees, 35 in 20-29 degrees, 15 in 30-39 degrees, and 24 over 40 degrees. According to curve pattern, 31 curves were classified as King type I, 32 as type II, 8 as type III, 11 as type IV, 17 as type V, 1 thoracolumbar curve and 1 lumbar curve. Cobb angle reduction was measured on AP radiographs from each group, according to sex, maturation, Cobb angle and curve pattern. RESULTS: Average reduction of Cobb angle was 8.2 degrees(range, 1-21 degrees ), 6.4 degrees for male and 8.6 degrees for female (p=0.19). The reduction value according to maturation was 8.3 degrees for the growing group and 8.0 degrees for the grown group (p=0.73). The average reduction value in Cobb angle 10-19 degrees was 5.4 degrees(40.3%), 20-29 degrees was 7.1 degrees(30.9%), 30-39 degrees was 8.6 degrees(25.7%) and over 40 degrees was 12.8 degrees (23.6%) (p=0.001). The reduction rate decreased in proportion to Cobb angle measured in standing position. The reduction value was 8.2 degrees in King type I curves, 8.6 degrees in type II, 9.1 degrees in type III, 9.1 degrees in type IV and 6.2 degrees in type V (p=0.238). CONCLUSION: An average 8 degrees Cobb angle reduction in supine position, compared with standing position, can influence treatment strategy in AIS patients, because a Cobb angle change more than 5-6 degrees is a threshold value to decide curve worsening. Thus, serial Cobb angle measurement should be performed in standing position.