The effect of pressure pad location of spinal orthosis on the treatment of adolescent idiopathic scoliosis (AIS)

Patient with moderate AIS is usually prescribed with spinal orthosis aiming to mechanically support and prevent the spine from further deterioration. In the conventional fitting method, pre-brace X-ray is the main reference, thus, the pressure pad of spinal orthosis may not be accurately located to the strategic areas because the spinal deformities could change 3-dimensionally once pressure pad is applied. A high correlation (r > 0.98) between Cobb's angle and spinous process angle (SPA) was found in the recent studies. With the advancements of 3D clinical ultrasound (3D CUS), tracing SPA along a scoliotic spine becomes possible and this can be used to estimate Cobb's angle. This study aimed to evaluate the effect of pressure pad location of spinal orthosis in the treatment of AIS and 3D CUS was used to trace SPA for estimation of Cobb's angle. The in-brace X-rays were assessed for confirmation of treatment effectiveness. The subjects were divided into ultrasound-guided fitting group A (n=21) and conventional fitting group B (n=22). In the group A, pressure pads were tested at 5 locations - the prescribed location as in the conventional fitting (referred to the pre-brace X-ray), and 1 cm and 2 cm above and below the prescribed location, and 3D CUS was applied to trace the SPA in these 5 pad locations, and the pad location with the lowest estimated Cobb's angle was selected in the final fitting. The assessments of inbrace X-rays showed that the mean Cobb's angle of group A decreased from 28.9° (pre-brace) to 18.6° (immediate in-brace) while the mean Cobb's angle of group B decreased from 27.1° (pre-brace) to 22.5° (immediate in-brace). There was a significant difference (p < 0.05) in the correction of Cobb's angle between the two groups. The results showed that accurate pressure pad location does play an important role in the reduction of Cobb's angle and 3D CUS can be considered as a non-invasive and effective assessment tool to improve orthotic treatment of AIS.