Variability of geometric measurements from three-dimensional reconstructions of scoliotic spines and rib cages

Labelle, Hubert; Dansereau, J.; Bellefleur, Christian; Jéquier, Jean-Claude

doi:10.1007/bf00278918

Cited by 79 publications

(36 citation statements)

References 14 publications

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“…However, the fundamental limitation of visualizing the key anatomical landmarks still exists. Some studies reported inter and intra observer differences during measurements of sagittal spine curvatures [21][22][23]. The differences are due to the inherent anatomical variants that alters the normal spine symmetry from side-to-side [24,25].…”

Section: Introductionmentioning

confidence: 99%

Influence of implant rod curvature on sagittal correction of scoliosis deformity

et al. 2014

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PURPOSE:To analyze the changes of implant rod angle of curvature during surgery and establish its influence on sagittal correction of scoliosis deformity. STUDY DESIGN:A retrospective analysis of the preoperative and postoperative implant rod geometry and angle of curvature was conducted.PATIENT SAMPLE: Twenty adolescent idiopathic scoliosis patients underwent surgical operation. Average age at the time of operation was 14 years. OUTCOME MEASURES:The preoperative and postoperative implant rod angle of curvature expressed in degrees was obtained for each patient. METHODS:Two implant rods were attached to the concave and convex side of the spinal deformity. The preoperative implant rod geometry was measured before surgical implantation.The postoperative implant rod geometry after surgery was measured by Computed Tomography scanner. The implant rod angle of curvature at the sagittal plane was obtained from the implant rod geometry. The angle of curvature between the implant rod extreme ends was measured before implantation and after surgery. The sagittal curvature between the corresponding spinal levels of healthy adolescents obtained by previous studies was compared to the implant rod angle of curvature to evaluate the sagittal curve correction. The difference between the postoperative implant rod angle of curvature and normal spine sagittal curvature of the corresponding instrumented level was used to evaluate over or under correction of the sagittal deformity.Page | 3 RESULTS:The implant rods at the concave side of deformity of all patients were significantly deformed after surgery. The average degree of rod deformation Δθ at the concave and convex side was 15.8 deg. and 1.6 deg., respectively. The average preoperative and postoperative implant rod angle of curvature at the concave side was 33.6 deg. and 17.8 degrees, respectively. The average preoperative and postoperative implant rod angle of curvature at the convex side was 25.5 degrees and 23.9 degrees, respectively. A significant relationship was found between the degree of rod deformation and preoperative implant rod angle of curvature (r = 0.60, p < 0.005). The implant rods at the convex side of all patients did not have significant deformation. The results indicate that the postoperative sagittal outcome could be predicted from the initial rod shape. CONCLUSIONS:Changes in implant rod angle of curvature may lead to over or under correction of the sagittal curve. Rod deformation at the concave side suggests that corrective forces acting on that side are higher than the convex side.

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Section: Introductionmentioning

confidence: 99%

Influence of implant rod curvature on sagittal correction of scoliosis deformity

et al. 2014

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“…The variability of the geometric parameters calculated from the 3D models has been shown to be smaller or within the inter-and intra-observer errors of similar clinical measurements made on radiographs with various rulers or goniometers [16].…”

Section: Methodsmentioning

confidence: 82%

Long-term three-dimensional changes of the spine after posterior spinal instrumentation and fusion in adolescent idiopathic scoliosis

Papin

Delorme

Aubin

et al. 1999

European Spine Journal

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This is a prospective study comparing the short-and long-term three-dimensional (3D) changes in shape, length and balance of the spine after spinal instrumentation and fusion in a group of adolescents with idiopathic scoliosis. The objective of the study was to evaluate the stability over time of the postoperative changes of the spine after instrumentation with multi rod, hook and screw instrumentation systems. Thirty adolescents (average age: 14.5 ± 1.6 years) undergoing surgery by a posterior approach had computerized 3D reconstructions of the spine done at an average of 3 days preoperatively (stage I), and 2 months (stage II) and 2,5 years (stage III) after surgery, using a digital multi-planar radiographic technique. Stages I, II and III were compared using various geometrical parameters of spinal length, curve severity, and orientation. Significant improvement of curve magnitude between stages I and II was documented in the frontal plane for thoracic and lumbar curves, as well as in the orientation of the plane of maximum deformity, which was significantly shifted towards the sagittal plane in thoracic curves. However, there was a significant loss of this correction between stages II and III. Slight changes were noted in apical vertebral rotation, in thoracic kyphosis and in lumbar lordosis. Spinal length and height were significantly increased at stage II, but at long-term follow-up spinal length continued to increase while spinal height remained similar. These results indicate that although a significant 3D correction can be obtained after posterior instrumentation and fusion, a significant loss of correction and an increase in spinal length occur in the years following surgery, suggesting that a crankshaft phenomenon may be an important factor altering the long-term 3D correction after posterior instrumentation of the spine for idiopathic scoliosis.

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“…Labelle et al [13] reported reliability of 1.1°for rib hump measured on rib cage 3-D reconstructions, based on repeated measures but not on repeated acquisitions. The reliability of the apparent rib hump index, based on back surface rotation, was comparable, with a typical error of measurement of 1.4°, considering that our results included the repositioning error.…”

Section: Differences Between the Two Posturesmentioning

confidence: 99%

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

et al. 2007

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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.

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Variability of geometric measurements from three-dimensional reconstructions of scoliotic spines and rib cages

Cited by 79 publications

References 14 publications

Influence of implant rod curvature on sagittal correction of scoliosis deformity

Influence of implant rod curvature on sagittal correction of scoliosis deformity

Long-term three-dimensional changes of the spine after posterior spinal instrumentation and fusion in adolescent idiopathic scoliosis

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

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