OBJECTIVESTo compare the sagittal profiles between thoracic idiopathic scoliosis (IS) patients with different curve progression and to determine the risk factors associated with curve progression.

METHODSA total of 83 thoracic IS patients from September 2009 to May 2010 were included in this study and were divided into 3 groups according to different curve progression. All the patients did not receive any previous treatments. There were 26 skeletally mature patients whose Risser sign were 5 degree with Cobb angle < 40° in non-curve progression group (NCP group), 29 mature patients whose Risser sign were 5 degree with Cobb angle ≥ 40° in moderate curve progression group (MCP group) and 28 immature patients whose Risser sign ≤ 3 degree with Cobb angle ≥ 40° in severe curve progression group (SCP group). Five sagittal parameters, including thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic incidence (PI) and pelvic tilt (PT) were measured on the lateral X-ray films. Analysis of variance was used to compare these parameters among the 3 groups.

RESULTSThe average thoracic Cobb angle was significantly smaller in NCP group when compared with MCP group (P < 0.01) or SCP group (P < 0.01), but not significantly different between the 2 latter groups (P = 0.619). The average TK was 19° ± 7° in NCP group, 13° ± 6° in MCP group and 8° ± 5° in SCP group. The average TK was significantly smaller in SCP group when compared with MCP group (P = 0.011) or NCP group (P < 0.01), while the average TK was significantly smaller in MCP group when compared with NCP group (P < 0.01). None of the other 4 parameters showed any significant difference between the 3 groups (P > 0.05).

CONCLUSIONSThoracic hypokyphosis is strongly associated with curve progression in thoracic IS patients. Pelvic sagittal profile may not be involved in the underlying mechanism of curve progression in thoracic IS patients.