Reliability of trunk shape measurements based on 3-D surface reconstructions

Abstract

This study aimed to estimate the reliability of 3-D trunk surface measurements for the characterization of external asymmetry associated with scoliosis. Repeated trunk surface acquisitions using the Inspeck system (Inspeck Inc., Montreal, Canada), with two different postures A (anatomical position) and B (''clavicle'' position), were obtained from patients attending a scoliosis clinic. For each acquisition, a 3-D model of the patient's trunk was built and a series of measurements was computed. For each measure and posture, intraclass correlation coefficients (ICC) were obtained using a bivariate analysis of variance, and the smallest detectable difference was calculated. For posture A, reliability was fair to excellent with ICC from 0.91 to 0.99 (0.85 to 0.99 for the lower bound of the 95% confidence interval). For posture B, the ICC was 0.85 to 0.98 (0.74 to 0.99 for the lower bound of the 95% confidence interval). The smallest statistically significant differences for the maximal back surface rotation was 2.5 and 1.5°for the maximal trunk rotation. Apparent global asymmetry and axial trunk rotation indices were relatively robust to changes in arm posture, both in terms of mean values and withinsubject variations, and also showed a good reliability. Computing measurements from cross-sectional analysis enabled a reduction in errors compared to the measurements based on markers' position.Although not yet sensitive enough to detect small changes for monitoring of curve natural progression, trunk surface analysis can help to document the external asymmetry associated with different types of spinal curves as well as the cosmetic improvement obtained after surgical interventions. The anatomical posture is slightly more reliable as it allows a better coverage of the trunk surface by the digitizing system.

A physically based trunk soft tissue modeling for scoliosis surgery planning systems

“…A smallest detectable difference of 2.5 • for the maximum BSR index was reported by Pazos et al [88] and therefore it is considered here as a threshold value to judge the accuracy of the simulation with regard to trunk asymmetry. The method proposed in the present work produced simulated postoperative trunks that are not only qualitatively similar to their real counterparts but that also quantitatively fall within the acceptable error range for the BSR index in the thoracic region, as given by the threshold value.…”

“…This choice is appropriate since the patient's first concern is for their trunk asymmetry and the BSR quantity has been proven to capture the information related to the rotation of the trunk and the rib hump [86,87,88].…”

Three-Dimensional Assessment of the Scoliosis

“…Moreover, it is closer to the perception of the distortion by the patient, being mainly concerned with the aesthetics 3D deformities induced by the scoliosis rather than the radiological distortion of the spine. (Pazos 2007, Denton 1992, Weisz 1988, Theologis 1997, Sahlstrand 1986 …”

Evaluation of Scoliosis Deviation with Clinical Measurements during Physical Therapy

“…TS symmetry is also one of the elements intergrading and improving the quality of life of patients, an issue vital for any human being. TS analysis can help document the external asymmetry associated with different types of spinal curves in scoliosis as well as the cosmetic improvement obtained after treatment with exercises [2].…”