Vertebral Translation Research Articles

Total disc arthroplasty: consequences for sagittal balance and lumbar spine movement

This in vivo biomechanical study was undertaken to analyze the consequences for sagittal balance and lumbar spine movement in three different lumbar disc prostheses. A total of 105 patients underwent total disc replacement in three different centers. The Maverick prosthesis was used in 46 patients, the SB Charité device was used in 49 patients and the Prodisc device was utilized in 10 patients. The analysis was computer assisted, using Spineview and Matlab softwares. The intra and inter-observer reliability and measurement uncertainty was performed. The analysis of lateral X-ray films in flexion-extension allowed to measure the prosthesis positioning, the range of motion (ROM), the localization of the mean center of rotation (MCR), the vertebral translation and the disc height, for each prosthesis device. The sagittal balance was analyzed on a full spine film. The parameters studied were described by Duval-Beaupère. The results were compared to the data found in literature, and compared to 18 asymptomatic volunteers, and 61 asymptomatic subjects, concerning the sagittal balance. The prostheses allowed an improvement of the ROM of less than 2 degrees. The ROM of L5-S1 prostheses ranged from 11.6 to 15.6% of the total lumbar motion during flexion-extension. At L4-L5 level, the ROM decreased when there was an arthrodesis associated at the L5-S1 level. There was no difference of ROM between the three prostheses devices. The MCR was linked to the ROM, but did not depend on the prosthesis offcentering. The disc height improved for any prosthesis, and decreased in flexion or in extension, when the prosthesis was offcentered. An increase of translation indicated a minor increase of the ROM at L4-L5 level after Maverick or SB Charité implantation. The L5-S1 arthrodesis was linked with an increase of the pelvic tilt. The lumbar lordosis curvature increased between L4 and S1, even more when a prosthesis was placed at the L3-L4 level. Total disc arthroplasty is useful in the surgical management of discogenic spinal pathology. The three prostheses studied allowed to retorate the disc height, the ROM, without disrupting the sagittal balance, but induced modification of the lumbar curvature.

P139. Adult Scoliosis Correction: A Comparison of Techniques

BACKGROUND CONTEXT: Rod derotation, in situ rod bending, and direct vertebral translation to the rod with sublaminar wires have all been used to correct adult scoliosis. A new implant-based method (without cables or wires) of direct vertebral translation has also been developed. No studies compare curve correction, complications, and patient outcomes between these techniques.

Dynamic MR and Quantitative MR Applied to the Study of Intervertebral Disk Degeneration

MR and CT demonstrate morphological changes in intervertebral disks. However the images do not provide an effective means to document interval changes in the disk due to degeneration, aging or healing. Functional imaging that may assesses the biomechanical or the biochemical integrity of the disk, may provide a measure of changes in the disk over time. To study the biomechanical function of the disk, translation and rotation of spinal vertebrae can be measured with CT or MR as the spine is subjected to a specific load or torque. Biochemical integrity of the disk can be assessed by the estimation of the water content from a measurement of the T2 relaxation time of disk tissue.

SPECIFIC FEATURES OF DEGENERATIVE LUMBAR SPINE DISEASE IN ELDERLY AND SENILE PATIENTS

Objective. To study clinical and morphological features of degenerative lumbar spine disease in elderly and senile patients for substantiation of optimal surgical treatment. Material and Methods. Prospective study included 128 consecutive patients operated for lumbar spine degeneration during 2003–2005. Patients were divided into two age groups: 88 patients of 60–83 years of age (mean 65.7 years) and 40 patients of 19–40 years of age (mean 31.8 years). Complex diagnosis consisted of anamnestic, general clinical, neurological, X-ray, MRI, and CT examinations. Results. Patients with clinical manifestations of segmental instability and neurogenic intermittent claudication syndrome prevailed in the older group. Clinical symptoms in elderly patients were associated primarily with degenerative stenosis of the spinal canal. Radiological and CT signs of segmental instability (or hypermobility) were more frequent in older age group than in young patients. Degenerative spondylolisthesis and degenerative scoliosis of the lumbar spine were found only in elderly patients (20.4 % and 21.5 % of cases, respectively). Segmental hypermobility in elderly patients was presented predominantly as a linear translation of vertebrae. Sagittal translation of vertebrae over 3 mm was registered in 54.5 % of older age group patients and only in 22.5 % of young ones (р < 0,01). Flexion-extension hyperangulation of damaged spine segments was found in 61.3 % of older patients and in 65.0 % of young ones. Conclusion. It may be assumed that surgical treatment of degenerative lumbar spine disease in elderly and senile patients should involve not only extensive decompression of neurovascular formations but also stabilization of damaged spine segments despite a higher risk and implementation difficulties of the surgery.

Stepwise reduction of functional spinal structures increase vertebral translation and intradiscal pressure

To date, there are only a few studies that provide data to efficiently calibrate finite element models for the spine due to its complexity. In a recent study, we quantified the range of motion rotation and the lordosis angle. This paper provides complementary results regarding two more parameters, intradiscal pressure and vertebral translation. All parameters were obtained as a function of stepwise anatomical reduction, loading direction and magnitude. Eight lumbar spinal segments (L4–5) with a median age of 52 years (38–59 years) and no signs of disc degeneration were used for the in vitro testing. A miniaturized pressure probe was implanted into the nucleus. An ultrasound-based motion-tracking system was employed to record spatial movements of several landmarks on the specimens. The center of L4, the anterior, posterior, left and right point of the lower endplate of L4 were digitized as landmarks and its translation was determined. Specimens were loaded with pure moments (1–10 Nm) in the three principal anatomical planes at a loading rate of 1.0°/s. Anatomy was stepwise reduced by cutting different ligaments, facet capsules and joints and removing nucleus. Translation analysis showed that the L4 center point had its largest displacement in sagittal direction and almost none vertically. Removal of the supra- and interspinous, flaval ligaments showed a slight increase and further removal of structures, a higher increase of translation. Axial rotation also was accompanied with L4 to elevate when torsion was applied. This effect was found to be larger with progressing defects. Nucleotomy exhibited the most unstable situation for specimens. Results of the intradiscal pressure indicated a large increase after removing the facet capsules and joints. Furthermore, it was found that intradiscal pressure correlated well with data of range of motion for rotation. Predicting and simulating clinical defects, surgical intervention or treatment methods requires a well performed calibration based on in vitro data, whereas it is important to adapt all including structures with as many known parameters as possible. Results provided by these studies may be used as a database for researchers aiming to calibrate or validate finite element models of L4–5 segments.

Is there a role for selective anterior instrumentation in neuromuscular scoliosis?

Our objective was to report on the clinical and radiological outcome from a cohort of patients with neuromuscular scoliosis who underwent selective anterior single rod instrumentation for correction of thoraco-lumbar and lumbar scoliosis. Traditionally combined anterior release with long posterior instrumentation has been advocated for the treatment of neuromuscular scoliosis. Neuromuscular curves tend to be long and may have significant pelvic obliquity. However, certain neuromuscular curves with minimal pelvic obliquity may lend themselves to selective anterior correction thereby saving motion segments and allow continued ambulation for those patients. Nine patients with neuromuscular scoliosis underwent selective anterior instrumentation between 1994 and 2000. The mean follow up was 2 years and 9 months (range 24-55 months). The clinical outcome (including parent and caregiver satisfaction), radiological outcome (Cobb angle, apical vertebral translation, pelvic obliquity, truncal shift, thoracic kyphosis, lumbar lordosis, sagittal vertical axis) and complications are reported. Subjective outcome was excellent in six patients and good in three. All nine patients retained their ability to walk. There were no neurological or vascular complications. Supplementary posterior surgery was required in two patients. The mean pre-operative Cobb angle of 52 degrees (range 44-60) improved to 20 degrees (range 10-28) at 3 months, achieving Cobb angle correction of 61% and was 19 degrees (range 7-28) at final follow-up. The mean pre-operative compensatory curve of 31 degrees (range 20-42) spontaneously corrected to 18 degrees (range 14-24) at 3 months and was maintained at 18 degrees (range 10-26) at final follow up. The mean pre-operative pelvic obliquity of 7 degrees (range 0-14) corrected to 4 degrees (range 0-8) at 3 months and was 3 degrees (range 0-8) at final follow up. Selective anterior instrumentation and fusion in carefully selected patients with neuromuscular scoliosis (short flexible curves, minimal pelvic obliquity, pre-operative walkers, slow or non-progressive pathology) appears to have satisfactory clinical and radiological outcome at least in the short-term.

Comparison of Manual and Digital Measurements in Adolescent Idiopathic Scoliosis

Comparison of manual and digital measurement of radiographic parameters in patients with adolescent idiopathic scoliosis (AIS). To assess the reliability of digital measures as compared to manual measures in the evaluation of AIS. Radiographic parameters are critical to the evaluation of patients with AIS, and are frequently used to monitor curve progression and guide treatment decisions. The reliability of many of the more common radiographic measures has only recently been elucidated for both manual and digital measures. However, a comparative analysis of manual versus digital measures has been performed only for coronal Cobb angles. The inter-technique reliability of these parameters will have increasing importance as digital radiographic viewing and analysis become commonplace. There were 2 independent, blinded observers that measured 30 complete sets of preoperative (posterior-anterior, lateral, and both side-bending) and postoperative (posterior-anterior and lateral) radiographs on 4 different occasions. For the first 2 iterations, manual measurements were taken using the same pencil and protractor. For the last 2 iterations, measurements of digitized radiographs were taken on a software measurement program (PhDx, Albuquerque, NM). Coronal measures included the main thoracic and thoracolumbar/lumbar standing and side-bending Cobb angles, apical vertebral translation, coronal balance, T1 tilt angle, lowest instrumented vertebrae angle, angulation of the disc inferior to the lowest instrumented vertebrae, apical Nash-Moe vertebral rotation, and Risser grade. Sagittal parameters included T2-T5 and T5-T12 regional thoracic kyphosis, T2-T12 thoracic kyphosis, T10-L2 thoracolumbar junction sagittal curvature, T12-S1 lumbar lordosis, and global sagittal balance. The technique-dependent measurement variability and the inter-technique (manual vs. digital), intraobserver reliability were evaluated for each radiographic parameter (within 3 degrees ). Digital measurement showed decreased intraobserver variability for many (9 of 15) of the radiographic parameters assessed. Likewise, digital measures indicated good or excellent correlation with the absolute values obtained with manual measurement for many (10 of 15) parameters. All but 1 of those parameters having moderate-to-poor correlation had been previously shown to have poor reliability, regardless of measurement technique. Statistically significant differences between measurement variability were noted for 6 measures, including 2 favoring digital and 4, manual. Significant differences in the absolute values were noted for 5 measures, determined at a difference of 3 degrees . However, the differences in both parameter variability and absolute values tended to be small and of little clinical significance for manual versus digital measurement. Digital measurement showed improved measurement precision and good correlation with manual measurements for the majority of AIS parameters. Absolute differences between manual and digital measurements were generally small. Therefore, digital measures are acceptable as a valid technique for scoliosis evaluation. The importance of digital versus manual measurement reliability will increase as digital radiographic viewing becomes more prevalent.

Short anterior correction of the thoracolumbar/lumbar curve in King 1 idiopathic scoliosis: the behaviour of the instrumented and non-instrumented curves and the trunk balance

This is a retrospective clinical, radiological and patient outcome assessment of 21 consecutive patients with King 1 idiopathic adolescent scoliosis treated by short anterior selective fusion of the major thoracolumbar/lumbar (TL/L) curve. Three-dimensional changes of both curves, changes in trunk balance and rib hump were evaluated. The minimal follow-up was 24 months (max. 83). The Cobb angle of the TL/L curve was 52 degrees (45-67 degrees) with a flexibility of 72% (40-100%). The average length of the main curve was 5 (3-8) segments. An average of 3 (2-4) segments was fused using rigid single rod implants with side-loading screws. The Cobb angle of the thoracic curve was 33 degrees (18-50 degrees) with a flexibility of 69% (29-100%). The thoracic curve in bending was less than 20 degrees in 17 patients, and 20-25 degrees in 4 patients. In the TL/L curve there was an improvement of the Cobb angle of 67%, of the apex vertebral rotation of 51% and of the apex vertebral translation of 74%. The Cobb angle of the thoracic curve improved 29% spontaneously. Shoulder balance improved significantly from an average preoperative imbalance of 14.5-3.1 mm at the last follow-up. Seventy-five percent of the patients with preoperative positive shoulder imbalance (higher on the side of the thoracic curve) had levelled shoulders at the last follow-up. C7 offset improved from a preoperative 19.8 (0-40) to 4.8 (0-18) mm at the last follow-up. There were no significant changes in rotation, translation of the thoracic curve and the clinical rib hump. There were no significant changes in thoracic kyphosis or lumbar lordosis. The average score of the SRS-24 questionnaire at the last follow-up was 91 points (max. 120). We conclude that short anterior selective fusion of the TL/L curve in King 1 scoliosis with a thoracic curve bending to 25 degrees or less (Type 5 according to Lenke classification) results in a satisfactory correction and a balanced spine. Short fusions leave enough mobile lumbar segments for the establishment of global spinal balance. A positive shoulder imbalance is not a contraindication for this procedure. Structural interbody grafts are not necessary to maintain lumbar lordosis.

Quantitative Analysis of Changes in Cervical Intervertebral Foramen Size With Vertebral Translation

Simulated translation of the C5 vertebra was performed in 20 embalmed cadaveric cervical spines, and cross-sectional areas of the C4-C5 and C5-C6 intervertebral foramina were measured and compared before and after translation of the C5 vertebra. To determine the relationship of cross-sectional intervertebral foraminal areas to the degrees of vertebral translation. The common feature of clinical instability and adjacent diseases of the cervical spine is malalignment of the cervical spine (i.e., there is ventral and dorsal translation of vertebral body with respect to the adjacent upper and lower vertebral body, respectively). To our knowledge, no previous study has analyzed the quantitative effect of vertebral translation on the size of the intervertebral foramina. The cross-sectional areas of the intervertebral foramina at C4-C5 and C5-C6 were measured on computerized tomography. The images were then transferred to the personal computer, where consecutive dorsal translations of C5 vertebrae with a 1-mm increment from 1 to 5-mm displacements were performed using Microsoft paint software (Microsoft, Corp., Redmond, WA). National Institutes of Health (Bethesda, MD) Image J software (V1.33m) was then used to measure the areas of both sides of C4-C5 and C4-C6 foramina at normal and each displacement level in the computer. Following dorsal translation of C5 vertebra, anterolisthesis of C4 relative to C5 and retrolisthesis of C5 relative to C6 was noted. No significant difference was found between the measured values using Aquarius Image software (Microsoft, Corp.) on computerized tomography and National Institutes of Health image J software on the desktop computer (P > 0.05). When compared with normal values, there was an increase in the C4-C5 intervertebral foraminal area (i.e., 6%, 14%, 18%, 21%, and 26% with anterolisthesis of C4 relative to C5 following 1, 2, 3, 4, and 5-mm dorsal translation of the C5 vertebra, respectively). There was a 12% decrease in the C5-C6 intervertebral foraminal area, with each 1-mm incremental retrolisthesis of C5 relative to C6 vertebra. Statistically significant differences were found among residual cross-sectional foraminal areas following different degrees of dorsal translation (P < 0.05). There is a significant increase in size with anterolisthesis and decrease in size with retrolisthesis of upper and lower adjacent vertebral intervertebral foramina, respectively.

In Vitro Study of Shear Force on Interbody Implants

The lordosis of the lumbar spine and body weight result in significant shear forces through the lumbosacral disc spaces. These forces result in translational motion across the disc space, which is resisted but not completely abolished by pedicle screw stabilization. It is postulated that this motion may be a factor in the development of nonunion of lumbar interbody fusions. An in vitro study of the micromotion of porcine specimens implanted with serrated or smooth interbody spacers and subjected to shear forces under compressive preload was conducted to determine whether the surface serrations on vertebral interbody implants significantly resist shear forces and resulting sagittal translation. Measurements of anterior vertebral translation were recorded on porcine cervical spine segments, subjected to 25 N of anteroposterior shear load while under a 300-N compressive preload. Baseline testing was performed on intact specimens and partially destabilized specimens (facet joints removed). Following partial discectomy, the specimens were divided into two groups for testing: one using smooth-surfaced and one using serrated interbody spacers. Under 25-N shear load, the specimens tested with the serrated spacers showed anterior vertebral translation of 0.046 +/- 0.013 mm, whereas those tested with the smooth spacers measured 0.152 +/- 0.075 mm (P < 0.01). The presence of surface serrations on the interbody implants significantly increased the resistance to shear forces in this model. In the clinical setting, we postulate that micromotion at interbody fusion sites will be substantially less when serrated implants are used and may help reduce the incidence of nonunion.

Anatomic Changes in Lateral Spondylolisthesis Associated with Adult Lumbar Scoliosis

Prospective consecutive series. To analyze the anatomic changes in lateral spondylolisthesis. Previous studies have focused on the correlation between lateral spondylolisthesis, and curve progression and pain. To our knowledge, there has not been any detailed report concerning anatomic changes in lateral spondylolisthesis. We examined 24 consecutive patients (mean age 66 years), with lateral spondylolisthesis associated with lumbar scoliosis who had computerized tomography (CT) after myelography. Coronal reconstruction CT was used to measure the vertebral translation. Vertebral rotation was measured by the Aaro method using transaxial CT. The Cobb angle averaged 26 degrees (range 13 degrees-75 degrees). Lateral spondylolisthesis was found most commonly at the lower-end vertebra. The cephalad-slipped vertebra rotated toward the convex side of the main curve, whereas the caudal vertebra rotated toward the convex side of the lumbosacral hemi (or fractional) curve below. Mean lateral translation and vertebral rotation were 7 mm and 8 degrees, respectively. There was a significant correlation between lateral translation and vertebral rotation (r = 0.49; P = 0.018). The convex superior articular process of the caudal vertebra had compressed the nerve root laterally in 21 patients, of whom 10 had radicular pain. The concave, inferior articular process of the cephalad vertebra had compressed the dural sac posteriorly, and 2 patients had radicular pain. To our knowledge, this study has been the first attempt to analyze anatomic changes in lateral spondylolisthesis using CT. It may offer further insight into the pathogenesis of adult lumbar scoliosis.

Cervical spine mobilizations in subjects with chronic neck problems: An interventional MRI study

Manual therapists frequently use posteroanterior mobilisation as both an examination tool and a form of conservative treatment. At present our knowledge of the principles underlying this technique are scant. This study aimed to investigate changes in vertebral kinematics and soft tissue displacement as a result of a sustained posteroanterior (PA) mobilisation applied to the cervical spine of a subject with a history of chronic neck pain. Five subjects were recruited and written informed consent obtained. Subjects were scanned using a General Electric Signa SPI0 Open Interventional MRI scanner. Subjects were scanned in the prone position with their necks in both neutral and flexed positions. In each position a PA mobilisation to the 2nd and 6th cervical vertebrae was performed. Sagittal images of the spine were obtained prior to, during and following the mobilisation, from which measures of vertebral angulation and translation were recorded. Measurements of intervertebral angulation and translation demonstrated little if any motion during the application of a PA mobilisation. Marked and significant changes were seen in terms of soft tissue compression and in some instances overall angulation of the cervical spine. These initial studies suggest that the application of a PA mobilisation to the cervical spine produces minimal if any intervertebral motion. This is in agreement with earlier studies investigating motion in healthy normal spines.

Correction of Adolescent Idiopathic Scoliosis Using Thoracic Pedicle Screw Fixation Versus Hook Constructs

This retrospective study was undertaken to determine the effectiveness and cost of thoracic pedicle screws versus laminar and pedicle hooks in patients undergoing surgical correction of adolescent idiopathic scoliosis (AIS). Immediate preoperative and 6-week postoperative radiographs were examined in 25 consecutive cases of children with AIS who were divided into two groups, those with thoracic pedicle screw constructs and those with thoracic hook constructs. Endpoints collected included radiographic measures, complications, surgical time, implant cost, and quality-of-life measures. Ten children underwent spinal fusion using thoracic pedicle screw fixation and 15 underwent thoracic constructs composed of hooks. Similar sex and age distribution were noted in both groups, and among the 20 girls and 5 boys the average age was 14.5. The mean preoperative Cobb angle was 53.5 degrees for the screw group and 52.5 degrees for the hook group. Correction averaged 70.2% for the screw group and 68.1% for the hook group. There were no significant differences between the two patient groups in terms of percentage of or absolute curve change after surgery. The apical vertebral translation, end vertebral tilt angle, and coronal balance did not differ significantly between the two patient groups. Comparison of operative time and quality of life revealed no significant differences. Screw constructs were significantly more expensive than hook constructs. The correction obtained from thoracic pedicle screw fixation is comparable to traditional hook constructs in AIS. Surgery using either construct effectively corrects AIS.

Assessment of Trunk Balance in Thoracic Scoliosis

A retrospective radiographic review was undertaken in patients with idiopathic thoracic scoliosis. To determine if a mathematical relationship exists between the 2 methods used to assess trunk balance (lateral trunk shift [LTS] and thoracic apical vertebral translation [AVT]), and to determine if one of these measurements can satisfactorily predict the value of the other. No previous reports exist, to our knowledge, comparing these 2 methods used to asess trunk balance. Coronal balance (CB), LTS, thoracic AVT, and curve magnitude were measured from standing preoperative posteroanterior radiographs of 91 patients with Lenke 1A/1B curves. The data were analyzed to determine if predictive relationships existed between LTS and thoracic AVT alone or between LTS and the sum of CB and thoracic AVT. A statistically significant relationship was shown between LTS and the sum of thoracic AVT and CB. In general, the LTS can be estimated by taking two thirds of the sum of thoracic AVT and CB (in centimeters) and subtracting 0.8. This relationship weakened as CB improved. The relationship between LTS and AVT was not statistically significant when CB was excluded. In patients with thoracic idiopathic scoliosis, if the CB and thoracic AVT values are known, then the LTS can be reliably estimated. The use of correct terminology for describing trunk balance and CB is important if valid comparisons of spinal deformity literature are desired.

P17. Adult scoliosis correction by direct vertebral translation technique: 2 year clinical and radiographic results

P17. Adult scoliosis correction by direct vertebral translation technique: 2 year clinical and radiographic results

Operative Treatment of Scoliosis With the Kaneda Anterior Spine System

Prospective, single-cohort study. To evaluate thoracic and thoracolumbar scoliosis using the Kaneda anterior spine dual-rod system (KASS). In selected cases, anterior correction of scoliosis has several advantages over the traditional posterior instrumentation. Other than 2 primary reports by Kaneda, there are no clinical outcome reports with the KASS in the literature. A total of 24 patients with thoracic (n = 10)/thoracolumbar (n = 14) scoliosis were corrected using the KASS. Sagittal and coronal plane radiologic parameters were evaluated before surgery, 1-year after surgery, and at final follow-up (approximately 40 months). Average coronal correction of the primary curve was from 61 degrees to 24 degrees (61%). Apical vertebral rotation decreased by 69%. Apical vertebral translation decreased 10-2 cm. The secondary thoracic and lumbar curves showed a spontaneous correction between 27% and 46%, respectively. Thoracic kyphosis increased 25 degrees -38 degrees (52%), lumbar lordosis showed a minimal decrease from 48 degrees to 43 degrees . Fusion was achieved in all cases. No neurovascular or implant-related problems were observed at final follow-up. Anterior instrumented fusion for thoracic/thoracolumbar scoliosis using the KASS is a good treatment option for idiopathic thoracic/thoracolumbar curves.

Reliability Analysis for Manual Adolescent Idiopathic Scoliosis Measurements

Manual radiographic measurement analysis. To determine the intraobserver and interobserver reliability of numerous radiographic process measures used in the assessment of adolescent idiopathic scoliosis. Analysis of scoliosis requires a thorough radiographic evaluation to completely assess the deformity. Numerous radiographic process measures have been studied extensively and used for outcomes assessment and thus become the de facto standard of care. However, many of these measures have not been evaluated to determine the reliability and reproducibility. Validation of radiographic process measures is necessary to compare these measures with patient-focused outcome measures, as well as to permit valid comparison of different surgical techniques. Thirty complete sets of long-cassette scoliosis radiographs (anteroposterior [AP], lateral and side-bending preoperative and AP, and lateral postoperative) were analyzed by three independent experienced observers on two separate occasions. Coronal image measures included the coronal Cobb angles, side-bending Cobb, apical vertebral translation, coronal balance, T1 tilt, lowest instrumented vertebrae (LIV) tilt, angulation of the disc below the LIV, apical vertebral rotation (Nash-Moe),and Risser sign; sagittal measures included T2-T5, T5-T12, T2-T12, T10-L2, T12-S1, and sagittal balance. Intraobserver and interobserver reliability for each measure was then assessed. The vast majority of the radiographic process measures assessed demonstrated good to excellent or excellent intraobserver and interobserver reliability. However, the angulation of the disc below the LIV demonstrated only fair interobserver reliability for postoperative measurements (rho = 0.59). Likewise, Risser grade measurements reflected good intraobserver (0.81-0.99) but only fair interobserver reliability (0.60-0.70). Apical vertebral rotation assessed by the technique of Nash and Moe produced good intraobserver reliability before surgery (0.74-0.85) but only fair reliability after surgery (0.50-0.85). The interobserver reliability for apical Nash-Moe rotation was fair to poor (0.53-0.59). For T2-T5 regional kyphosis, intraobserver (0.22-0.83) and interobserver (0.33-0.47) reliability was generally poor. Overall, the reliability of postoperative measurements tended to be decreased relative to preoperative values, likely due to instrumentation overlying radiographic landmarks. Most of the radiographic process measures evaluated in this study demonstrated good or excellent reliability. The reliability of measuring the angulation of the disc below the LIV, the apical Nash-Moe rotation, and Risser grading was decreased relative to other measures. The reliability of measuring T2-T5 regional kyphosis was disappointing and poor. With regards to the other 13 measures assessed, our findings support the use of these process measures obtained by experienced deformity surgeons via manual measurement for routine clinical and academic purposes.

Selective thoracic fusion in adolescent idiopathic scoliosis

OBJECTIVE: To define the criteria of selective thoracic fusion in adolescent idiopathic scoliosis patients. METHODS: By reviewing the roentgenograms of adolescent idiopathic scoliosis patients undergoing selective thoracic fusion, the curve type, Cobb angle, apical rotation and translation, trunk shift, and thoracolumbar kyphosis were measured and analyzed. RESULTS: There were 12 King type II patients (PUMC type: IIb1 9, IIc3 3). The coronal Cobb angle of thoracic curve before and after surgery were 54.0 degrees and 19.0 degrees respectively, and the average correction rate was 62.7%. The coronal Cobb angle of lumbar curve before and after surgery were 34.6 degrees and 12.5 degrees respectively, and the average spontaneous correction rate was 64.7%. At the final follow-up, the coronal Cobb angle of thoracic and lumbar curve was 18.8 degrees and 15.9 degrees respectively. There was no significant change in the coronal Cobb angle, apical vertebral translation and rotation compared with that after surgery. 1 patient had 12 degrees of thoracolumbar kyphosis after surgery, no progression was noted at the final follow-up. There was no trunk decompensation or deterioration of the lumbar curve. In this group, 3.5 levels were saved compared with fusing both the thoracic and lumbar curves. CONCLUSION: Selective thoracic fusion can be safely and effectively performed in patients with a moderate and flexible lumbar curves, which can save more mobile segments to maintain a good coronal and sagittal balance.

Thoracic scoliosis fusion in adolescent and adult idiopathic scoliosis using posterior translational corrective techniques (Isola): is maximum correction of the thoracic curve detrimental to the unfused lumbar curve?

Background context Postoperative coronal decompensation in selective thoracic fusion was reported with derotation maneuvers when using the Cotrel-Dubousset (CD) system. Isola instrumentation is a multiple anchor system that corrects spine deformity with segmental vertebral translation to a predetermined contoured longitudinal member. Purpose To evaluate the efficacy of translational corrective techniques using Isola instrumentation in thoracic fusion for adolescent and adult idiopathic scoliosis patients. Study design/setting This is a retrospective review of adolescent and adult patients with idiopathic scoliosis who underwent posterior thoracic fusion using translational corrective techniques with Isola instrumentation. Patient sample Twenty-two patients (14 adolescents with idiopathic scoliosis, 8 adults with scoliosis) who underwent posterior thoracic fusion using translational corrective techniques were evaluated. Outcome measures The charts, radiographs and self-assessment questionnaire were reviewed. Methods Comparative analysis was done between patients who had Lenke Type A curves (Group 1) and Lenke Type B or C curves (Group 2) for both adolescent and adult scoliosis groups. Results The mean follow-up was 54 months (range, 33 to 80 months). The mean preoperative Cobb angle of thoracic and lumbar curves in all 22 patients was 48 degrees (range, 34 to 64 degrees) and 31 degrees (range, 20 to 46 degrees), respectively. Postoperative measurements were 16 degrees (range, 0 to 28 degrees) for thoracic and 13 degrees (range, 2 to 25 degrees) for lumbar (67% thoracic and 60% lumbar correction) in Group 1, and 19 degrees (range, 1 to 33 degrees) for thoracic and 12 degrees (1 to 21 degrees) for lumbar at latest follow-up (61% thoracic and 61% lumbar correction) in Group 2. There was no difference in the final correction of the lumbar curves between Groups 1 (64%) and 2 (58%), although the Cobb angle in Group 2 was larger. Radiographic coronal decompensation occurred in only one patient in Group 2, who remained asymptomatic and required no further treatment. Clinical outcome assessment showed 100% satisfaction (n = 15), 92% relief of symptoms (n = 13) and 92% improvement of activities in both groups. Conclusions Fusion of the major thoracic curve using translational corrective technique (Isola) in patients with idiopathic scoliosis is an effective procedure that achieves high patient satisfaction while providing excellent correction of both the thoracic and lumbar curves. Unlike rotational corrective techniques (CD), clinical decompensation requiring further treatment did not occur in any patient treated with this method.

Anterior Single Rod Instrumentation for Thoracolumbar Adolescent Idiopathic Scoliosis With And Without the Use of Structural Interbody Support

A radiographic and clinical outcomes analysis of 41 patients treated for thoracolumbar adolescent idiopathic scoliosis utilizing a single anterior rigid rod construct. To evaluate the necessity of structural interbody support to improve primary curve correction and preserve or augment lordosis when used in conjunction with a single anterior rigid rod construct, to identify parameters that predict horizontalization of the lowest instrumented vertebra, adjacent disc angulation, and distal uninstrumented vertebrae, and to assess patient satisfaction following surgery. Instrumentation-induced kyphosis has been a concern with nonrigid anterior systems used in the past for the treatment of scoliosis. Interbody structural support has been recommended to maintain appropriate sagittal profile when anterior systems are utilized. It has also been suggested that the use of structural interbody support creates a fulcrum to increase curve correction when compression is applied to the convexity of the deformity. However, the necessity of interbody structural support when used in conjunction with a rigid anterior system has not been previously evaluated in patients with adolescent idiopathic scoliosis. Forty-one patients mean age 15.9 years (range 12.1-18.6 years) with thoracolumbar adolescent idiopathic scoliosis underwent anterior spinal fusion using a single 6.0 to 6.5 mm solid rod construct between June 1995 and August 1999 performed by the senior author (T.G.L.). Four additional patients with thoracolumbar curves with similar anterior instrumentation over the same time period were lost to follow-up or had incomplete records and were not included in the study. Structural interbody support was used in 21 patients and packed morselized autograft alone was used in 20 patients. The patients in the group with packed morselized bone alone generally underwent surgery earlier in the series before the author began using structural interbody support on a regular basis. Each patient had a minimum follow-up of 3 years. Preoperative, initial, and most recent (>3 years) follow-up radiographs were reviewed to determine in each group Cobb angle measurements, flexibility of primary, secondary, and fractional curves, apical and end vertebral translation, lowest instrumented vertebral and caudal disc angulation, global coronal and sagittal balance, and sagittal Cobb measurements in both instrumented levels as well as lumbar lordosis (T12-S1). In addition, the SRS outcomes instrument was completed by 38 of 41 patients. The mean preoperative primary curve in patients with structural support was 47 degrees (Group II) and 45 degrees in patients without structural support (Group I). Mean curve correction was to 13 degrees in Groups I and II. One patient in Group II became slightly more unbalanced at final follow-up; otherwise all were improved after surgery. Sagittal measurements over instrumented segments as well as total lumbar lordosis (T12-S1) was maintained between preoperative and final postoperative values in both groups. Similarly, in both groups, when horizontalization of the distal end instrumented vertebra was achieved on the preoperative reverse side-bending radiograph, more normal relationships were achieved between instrumented and distal noninstrumented segments (adjacent disc angulation and fractional lumbar curve) at final follow-up (P <or= 0.01). Patients in both groups were equally pleased with their clinical outcomes based on the SRS outcomes instrument. The use of interbody structural support does not appear to be necessary to maintain an appropriate sagittal profile or to maximize coronal curve correction when a rigid rod construct with packed morselized bone is used for the treatment of thoracolumbar adolescent idiopathic scoliosis. Parameters predicting horizontalization of the lower instrumented vertebra and uninstrumented segments below the construct were identified, which, if achieved, should predict an optimal long-term outcome. Clinical outcomes were very good in both groups.