Xue C. Liu

Relationship between Quantec measurement and Cobb angle in patients with idiopathic scoliosis.

The Quantec Spinal Imaging System (QSIS) is a raster stereography used to measure three-dimensional trunk images. The Q angle, a coronal plane measurement generated by the Quantec Spinal Imaging System (QSIS), was compared with the Cobb angle in assessment of scoliosis curve magnitude. One hundred forty-nine patients with idiopathic scoliosis were evaluated using both the Quantec system and plane radiographs. The Cobb and Q angles demonstrated significant correlation in the thoracic region (r = 0.65, p < 0.05), lumbar region (r = 0.63, p < 0.05), and in the thoracolumbar region (r = 0.70, p < 0.05). The difference between the Q and Cobb angles was small when the Cobb angle was <21 degrees with less than 6 degrees of axial surface rotation, as measured by the QSIS method. For smaller curves with minimal rotation, there is close correlation between the Cobb angle and the Quantec angle.

Functional classification of patients with idiopathic scoliosis assessed by the Quantec system: a discriminant functional analysis to determine patient curve magnitude.

Study Design. A stepwise discriminant analysis was used to define a spinal deformity score based on three-dimensional measurements by the Quantec spinal image system (raster stereophotograph). Objective. To provide functional classification of spinal deformity in patients with mild idiopathic scoliosis without using radiographs. Summary of Background Data. Most studies classify the degree of spinal deformity in terms of coronal plane radiograph without analyzing transverse rotation. To the authors’ knowledge, no studies investigating classification of spinal deformity in idiopathic scoliosis using Quantec system measurements have been documented. Methods. In this study, 129 patients with a single curve and 119 patients with a double curve were divided into three groups according to Cobb angle: Group 1 (less than 10°), Group 2 (10–20°), and Group 3 (greater than 20°). Results. The patients were assigned to the group with the highest scores after application of a stepwise discriminant analysis. The accuracy of the classification system by functional scores for the patients with a single curve was 85% for Group 1, 63.5% for Group 2, and 71.7% for Group 3. The accuracy of classification by functional scores for the patients with a double curve was 87.1% for Group 2 and 76.1% for Group 3. Conclusion. The back surface image study is a method for providing a quantitative assessment of mild spinal deformity, allowing evaluation of patients by integrated three-dimensional parameters with no reference to radiographs.

Variability in three-dimensional measurements of back contour with raster stereography in normal subjects

Forty normal children with a mean age of 9.1 years were investigated by using a Quantec Spinal Image System (QSIS). The QSIS uses computerized raster stereography technology to acquire three-dimensional measurements of back contour. Within a 95-percentile confidence interval (a) coronal-plane QSIS angles ranged from 0.05 to 2.36 degrees; (b) transverse-plane QSIS angles ranged from 0.03 to 1.96 degrees; and (c) sagittal-plane QSIS angles ranged from 36.8 to 44.8 degrees. Trunk-alignment deviation ranged from 3.51 to 7.45 mm within a 95-percentile confidence interval. An intraobserver standard deviation of +/-4.2 degrees was noted across all angular metrics. Normal ranges of QSIS-determined values for a population of 40 children without clinical evidence of pathology are reported.

Three-dimensional rotations of the thoracic spine after distraction with and without rib resection: a kinematic evaluation of the apical vertebra in rabbits with induced scoliosis.

An experimental model of induced scoliosis in New Zealand rabbits was studied to evaluate the effects of rib resection on the apical vertebra during distraction for scoliosis surgery. After concave distraction, three-dimensional rotations of the apical vertebra were measured using a motion analysis system, which included three cameras and six reflective markers. Distraction with rib resection on the convexity produced minimal rotations in the coronal plane (0.77 degrees), sagittal plane (0.96 degrees), and transverse plane (0.61 degrees) compared with no rib resection. The distraction maneuver with rib resection has no significant effect on derotation of the apical vertebra in the coronal and transverse plane, but slightly greater forward rotation was apparent in the sagittal plane (p < 0.05). Resection of three convex ribs directly corrects the rib prominence and does not seem to improve derotation.

Reproducibility of newly developed spinal topography measurements for scoliosis.

Objective: In an effort to limit exposure to ionizing radiation and fully characterize three dimensional changes in the spine of patients with scoliosis reliable non-invasive methods of spinal back contour analysis (Milwaukee Topographic Scanner) (MTS) have been developed. Study Design: The current study compares spinal topography measurements among different subject positions and evaluates the reproducibility of the system for both inter-rater and intra-rater reliability. Methods: A dummy cast (plastic cast) of one patient with adolescent idiopathic scoliosis was created in order to test the reliability of the MTS. The dummy cast was positioned and rotated in 3D while scanned by two investigators using the MTS. A total of twelve parameters including Q-angle (an analog to X-ray’s Cobb angle) were extracted. Results: All measurements of intra-rater and inter-rater reliability were excellent (Intraclass Correlation Coefficients ranging from 0.89 to 0.99) with the exception of Pelvic Tilt (intra-rater ICC is 0.61) and lordosis angle (inter-rater ICC is 0.82). No significant variability among investigators was observed for all tested metrics. No significant variability due to position was observed for the majority of back contour measurements but there were significant changes in the T1-S1 angle, T1-S1 deviation, T1-NC angle, T1-NC deviation, and Back Height metric (p< 0.05). Conclusions: The MTS is a reliable method of raster stereography in the measurement of the back contour, which will help monitor the progression of children with idiopathic scoliosis and reduce the use of X-rays.

Computerized evaluation of the surface measurement of kyphosis and lordosis in idiopathic scoliosis

Hypokyphosis is usually seen in patients with idiopathic scoliosis. The Quantec spinal image system provides an alternative to measuring the sagittal plane surface contour. The Cobb method and Quantec is significantly correlated (p<0.05), however, differences are larger in kyphosis than in lordosis. The advantage of the QSIS is to reduce X-ray exposure.

Dynamic plantar pressure measurements in children with tarsal coalition

Tarsal coalition is a congenital foot anomaly seen in childhood. It results in a rigid flatfoot deformity. Radiographic studies are needed to confirm the diagnosis. Characterization of this foot deformity during normal gait was done using the Emed plantar pressure system (Novel Electronics Inc, St Paul, USA). The hindfoot demonstrated higher than normal peak pressure and increased peak pressure on the third metatarsal area with an increased plantar contact area on the midfoot. The center of pressure line had a normal trajectory.

Dynamic plantar pressure in the treated clubfoot: an orthopaedic engineering study

Dynamic plantar pressure assessment provides a quantitative functional tool for monitoring foot kinetics. In this study 26 idiopathic clubfeet that had complete subtalar releases at an average of 7.5 years underwent EMED plantar pressure study. As compared to 68 normal subjects, treated clubfoot patients showed greater differences in plantar contact area and peak pressure at the midfoot, and hallux. A significant lateral shift of the center of pressure in the region of the forefoot was also found. The effects of complete subtalar releases on the forefoot pressures is a unique finding.