A biomechanical study on the effects of rib head release on thoracic spinal motion (original) (raw)
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An In Vitro Human Cadaveric Study Investigating the Biomechanical Properties of the Thoracic Spine
Spine, 2002
Study Design. An in vitro human cadaveric study comparing the effects of anterior and posterior sequential destabilization conditions on thoracic functional unit mechanics was studied. Objectives. To investigate the biomechanical properties of the human thoracic spine. Summary of Background Data. Few studies have addressed the mechanical role of the costovertebral joints under torsion in the stability of the human thoracic spine. Methods. Sixteen functional spinal units with intact costovertebral joints were obtained from six human cadavers and randomized into two groups based on destabilization procedures: Group 1, anterior to posterior sequential resection; and Group 2, posterior to anterior sequential destabilization. Biomechanical testing was performed after each destabilization procedure, and the range of motion under maximum load was calculated. Results. Group 1: Under flexion-extension, lateral bending, and axial rotation loading, discectomy increased the range of motion by 193%, 74%, and 111%, respectively. Moreover, subsequent right rib head resection further increased the range of motion by 81%, 84%, and 72%, respectively. Group 2: Under all loading conditions laminectomy ϩ medial facetectomy resulted in a 22-30% increase in range of motion. Subsequent total facetectomy led to an additional 15-28% increase in range of motion. Conclusion. The rib head joints serve as stabilizing structures to the human thoracic spine in the sagittal, coronal, and transverse planes. In anterior scoliosis surgery additional rib head resection after discectomy may achieve greater curve and rib hump correction. The lateral portion of the facet joints plays an important role in providing spinal stability and should be preserved to minimize postoperative kyphotic deformity and segmental instability when performing decompressive wide laminectomy.
Analysis of the interaction between vertebral lateral deviation and axial rotation in scoliosis
Journal of Biomechanics, 1991
There is a lack of clear biomechanical analyses to explain the interaction of the lateral and axial deformity of the spine in idiopathic scoliosis. A finite element model which represented an isolated ligamentous spine with realistic elastic properties and idealized geometry was used to analyse this interaction. Three variations of this model were used to investigate two different hypotheses about the etiology of scoliosis and to define the forces required to produce a scoliosis deformity. The first hypothesis is that coupling within a motion segment produces the interaction between lateral deviation and axial rotation. The second hypothesis is that posterior tethering by soft tissues in the growing spine produces the observed interaction. Modeling of both hypotheses failed to produce the clinically observed pattern of interaction.
Scoliosis and Spinal Disorders
Background: Axial vertebral rotation is a key characteristic of adolescent idiopathic scoliosis (AIS), and its reduction is one of the goals of corrective surgery. Recurrence of deformity after surgical correction may relate to rotation changes that occur in the anterior vertebral column after surgery, but whether any change occurs within the fused segment or in adjacent unfused levels following thoracoscopic anterior spinal fusion (TASF) is unknown. An analysis of measurements from an existing postoperative CT dataset was performed to investigate the occurrence of interand intra-vertebral rotation changes after TASF within and adjacent to the fused spinal segment and look for any relationships with the Cobb angle and rib hump in the two years after surgery. Methods: 39 Lenke Type 1 main thoracic patients underwent TASF for progressive AIS and low dose computed tomography scanning of the instrumented levels of the spine at 6 and 24 months after surgery. Vertebral rotation was measured at the superior and inferior endplates on true axial images for all vertebral levels in the fused segment plus one adjacent level cranially and caudally. Intra-observer variability for rotation measurements was assessed using 95% limits of agreement to detect significant changes in inter/intra-vertebral rotation. Results: Significant local changes in inter-and intra-vertebral rotation were found to have occurred between 6 and 24 months after anterior surgical fusion within the fused spinal segment, albeit with no consistent pattern of location or direction within the instrumented fusion construct. No significant en-bloc movement of the entire fused spinal segment relative to the adjacent un-instrumented cranial and caudal intervertebral levels was found. No clear correlation was found between any vertebral rotation changes and Cobb angle or rib hump measures. Conclusions: Localised inter-and intra-vertebral rotation occurs between 6 and 24 months after TASF, both within the instrumented spinal segments and in the adjacent un-instrumented levels of the adolescent spine. The lack of measurable en-bloc movement of the fused segment relative to the adjacent un-instrumented levels suggests that overall stability of the instrumented construct is achieved, however the vertebrae within the fusion mass continue to adapt and remodel, resulting in ongoing local anatomical and biomechanical changes in the adolescent spine.
Institute of Health and Biomedical Innovation; Science & Engineering Faculty, 2017
Background Context: In recent years, there has been increasing appreciation of the need to treat scoliosis as a three-dimensional deformity. Purpose: Assessment of surgical strategies and outcomes should consider not only the coronal plane correction but also derotation of the transverse plane deformity that can affect trunk appearance. Study Design: This study included a cohort of 29 female adolescent idiopathic scoliosis patients who received thoracoscopic single rod anterior fusion (TASF) surgery. This study used pre-and postoperative low-dose computed tomographic (CT) scans to accurately measure apical axial vertebral rotation (AVR). Methods: The pre-and postoperative values for clinically measured coronal Cobb correction and rib hump correction as well as AVR were compared to determine whether these values improved postoperatively. There are no conflicts of interest to report for authors of this investigation. Results: As expected, statistically significant reductions in coronal Cobb angle (mean preoperative Cobb 51 , reducing to 24 at the twoyear follow-up) and rib hump (mean preoperative rib hump 15 , reducing to 7 at two-year follow-up) were achieved. The mean reduction in apical AVR measured using CT was only 3 (mean preoperative AVR 16 , reducing to 13 at two-year follow-up), which was statistically but not clinically significant. Significant correlations were found between Cobb angle and rib hump, between Cobb angle and AVR, and between AVR and rib hump, suggesting that patients with greater coronal Cobb correction also achieve better derotation with this surgical procedure. Conclusions: The historical low-dose CT data set permitted detailed three-dimensional assessment of the deformity correction that is achieved using thoracoscopic anterior spinal fusion for progressive adolescent idiopathic scoliosis.
Journal of Spine, 2017
Introduction Recent developments of spinal instruments allow to address nearly all components of idiopathic scoliosis. Direct vertebral rotation (DVR) maneuver was introduced to correct apical axial vertebral rotation. It is however still not well established how efficiently DVR affects results of scoliosis correction. The object of the study was to evaluate en bloc apical vertebral rotation (DVR) and its impact on coronal and sagittal correction of the spine in patients undergoing surgical scoliosis treatment. Materials and methods Thirty-six consecutive patients who underwent posterior spinal fusion with pedicle screws only constructs for idiopathic scoliosis. Fifteen patients (20 curves) were corrected by rod derotation only and 21 patients (26 curves) had both rod derotation and DVR. Curve measurements were performed on x-rays obtained before and postoperatively-coronal curves, kyphosis (T2-T12, T5-T12). Spine flexibility was assessed on prone bending x-rays. Apical axial rotation was determined on CT scans obtained intraoperatively and postoperatively. Rotation angle (RAsag) was measured according to Aaro and Dahlborn. Results We observed reduction of RAsag in all patients; however, in DVR group, decrease was greater, by 31.8% comparing to non-DVR group, by 8.6% (p = 0.0003). Mean coronal correction in DVR group was 68.8% and in rod derotation group without DVR 55% (p = 0.002). No significant correlation was found between degree of derotation obtained and coronal correction. In DVR group T2-T12 kyphosis has increased in 28 (65%) patients whereas in non-DVR group in 31 (69%) cases. Mean value of T2-T12 kyphosis growth was 16.7% in DVR and 22.1% in non-DVR group. These differences however did not occur statistically significant. Conclusions Direct vertebral rotation (DVR) maneuver reduces significantly apical rotation of the spine, enhances ability of coronal correction, and it does not reduce thoracic kyphosis.
Spine deformity, 2017
In recent years, there has been increasing appreciation of the need to treat scoliosis as a three-dimensional deformity. Assessment of surgical strategies and outcomes should consider not only the coronal plane correction but also derotation of the transverse plane deformity that can affect trunk appearance. This study included a cohort of 29 female adolescent idiopathic scoliosis patients who received thoracoscopic single rod anterior fusion (TASF) surgery. This study used pre- and postoperative low-dose computed tomographic (CT) scans to accurately measure apical axial vertebral rotation (AVR). The pre- and postoperative values for clinically measured coronal Cobb correction and rib hump correction as well as AVR were compared to determine whether these values improved postoperatively. There are no conflicts of interest to report for authors of this investigation. As expected, statistically significant reductions in coronal Cobb angle (mean preoperative Cobb 51°, reducing to 24° a...
Anterior Vertebral Body Tethering for Idiopathic Scoliosis
Spine, 2014
Objective. To report the 2-year results of the initial cohort undergoing anterior vertebral body tethering (VBT). Summary of Background Data. Anterior VBT is a promising new technique with abundant preclinical studies but very few clinical results. It is a growth modulation technique, which utilizes patients' growth to attain progressive correction of their scoliosis. We report 2-year results of the initial cohort undergoing this procedure. Methods. After obtaining institutional review board approval, we retrospectively reviewed our fi rst 11 consecutive patients who underwent anterior VBT with 2-year follow-up. We collected pertinent preoperative, intraoperative, and most recent clinical and radiographical data. Student t test and Fisher exact test were utilized to compare different time points. Results. Eleven patients with thoracic idiopathic scoliosis (8 females) were identifi ed, with a mean age of 12.3 ± 1.6 years. Preoperatively, all were skeletally immature (Sanders mean = 3.4 ± 1.1; Risser mean = 0.6 ± 1.1). All underwent tethering of an average of 7.8 ± 0.9 (range: 7-9) levels, with the most proximal being T5 and the most distal L2. Preoperative thoracic Cobb angle averaged 44.2 ± 9.0 ° and corrected to 20.3 ± 11.0 ° on fi rst erect, with progressive From the improvement at 2 years (Cobb angle = 13.5 ± 11.6 ° , % correction = 70%; P < 0.00002). Similarly, the preoperative lumbar curve of 25.1 ± 8.7 ° demonstrated progressive correction (fi rst erect = 14.9 ± 4.9 ° , 2 yr = 7.2 ± 5.1 ° , % correction = 71%; P < 0.0002). Thoracic axial rotation as measured by a scoliometer went from 12.4 ± 3.3 ° preoperatively to 6.9 ± 3.4 ° at the most recent measurement ( P < 0.01). No major complications were observed. As anticipated, 2 patients returned to the operating room at 2 years postoperatively for loosening of the tether to prevent overcorrection. Conclusion. Anterior VBT is a promising technique for skeletally immature patients with idiopathic scoliosis. This technique can be performed safely and can result in progressive correction.