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ABSTRACT: PURPOSE: Non-fusion treatment for adolescent idiopathic scoliosis generates interest due to the potential for growth preservation and mobility. Using an established porcine scoliotic model, this study aims to evaluate the global alignment and the morphology of the spine with and without application of a non-fusion corrective tether. METHODS: At 12 weeks of age, 21 immature Yorkshire pigs had an induction of scoliosis. Once a 50° Cobb angle was obtained; animals were placed into one of the following groups: a scoliosis model group (SM, n = 11) where animals were euthanized, tether release group (TR, n = 5) where the inducing tether was removed, and an anterior correction group (AC, n = 5) where the inducing tether was removed and non-fusion corrective tether was applied. TR and AC were observed for a further 20 weeks and then euthanized. Post-mortem CT scans were used to create 3D spinal reconstructions to obtain global and morphologic parameters. RESULTS: Maximal Cobb angle of the scoliotic deformity was significantly lower for AC (27.9° ± 12.0°) than for the two other groups (TR 52.7° ± 10.0°, SM 48.3° ± 7.6°). AC experienced an increase in kyphosis (24.2° ± 15.9°) compared to TR (7.1° ± 6.4°). Correction in the axial plane was also observed in AC versus TR. Correction of vertebral wedging was found for AC compared to SM and TR in the three apical vertebrae. CONCLUSIONS: 3D realignment of scoliotic curves was observed with application of the corrective tether. The correction was the product of both mechanical action and growth modulation. These findings are encouraging for future development of a non-fusion device for the treatment of immature scoliotic curves.
European Spine Journal 03/2013; · 1.97 Impact Factor
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ABSTRACT: Histological growth plate analysis. OBJECTIVE.: To evaluate the histological effects on vertebral growth plates following corrective mechanical tethering in the porcine scoliosis model.
Theoretically, growth modulation allows progressive vertebral correction in the setting of scoliosis (Hueter-Volkmann principle).
This IACUC-approved study divided 9 immature Yorkshire pigs into 2 groups: deforming tether release (TR, n = 4) group and anterior corrective (AC, n = 5) tether group. Once 50° coronal Cobb was demonstrated, TR had release of the deforming tether, whereas AC had release of the deforming tether and additional placement of a corrective tether. After 20 weeks of observation, pigs were killed, spines were removed, and apical samples were prepared for histological study. Growth plate analysis included the following histological parameters: proliferative zone height, hypertrophic zone height, and cell heights within the hypertrophic zone. Student t test was used to evaluate differences within and between groups.
No significant differences were found within the release group on the concave versus convex side in terms of proliferative zone height, hypertrophic zone height, and cell heights in the hypertrophic zone. In the anterior correction group, the proliferative zone height was significantly smaller on the concave side than on the convex side (P < 0.01); no significant differences were found in AC on the concave versus convex side in terms of hypertrophic zone height and cell heights in the hypertrophic zone. No significant differences were found in any parameters between TR and AC on either the concave or the convex side.
No significant decrease in any of the measured parameters was observed in the anterior correction group compared with the tether release group. These histological findings are consistent with preservation of growth potential.
Spine 02/2012; 37(15):E883-9. · 2.08 Impact Factor
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ABSTRACT: Pelvic tilt is an established measure of position which has been tied to sagittal plane spinal deformity. Increased tilt is noted in the setting of the aging spine and sagittal malalignment syndromes such as flatback (compensatory mechanism). However, the femoral heads are often poorly visualized on sagittal films of scoliosis series in adults, limiting the ability to determine pelvic incidence and tilt. There is a need to establish a coronal plane (better visualization) pelvic parameter which correlates closely with pelvic tilt.
This is a retrospective review of 71 adult patients (47 females and 24 males) with full-length standing spine radiographs. Visualization of all spinal and pelvic landmarks was available coronally and sagittally (including pelvis and acetabuli). Pelvic tilt was calculated through validated digital analysis software (SpineView(®)). A new parameter, the sacro-femoral-pubic angle (midpoint of S1 endplate to centroid of acetabuli to superior border of the pubic symphysis) was analyzed for correlation (and predictive ability) with sagittal pelvic tilt.
The sacro-femoral-pubic angle (SFP angle) was highly correlated to PT, and according to this analysis, pelvic tilt could be estimated by the formula: PT = 75 - (SFP angle). A Pearson's correlation coefficient of 0.74 (p < 0.005) and predictive ability of 76% accuracy was obtained (±7.5°). The correlation and predictive ability was greater for males compared to females (male: r = 0.87 and predictive model = 93%; female: r = 0.67 and predictive model = 67%).
The pelvic tilt is an essential measure in the context of radiographic evaluation of spinal deformity and malalignment. Given the routinely excellent visibility of coronal films this study established the SFP as a coronal parameter which can reliably estimate pelvic tilt. The high correlation and predictive ability of the SFP angle should prompt further study and clinical application when lateral radiographs do not permit assessment of pelvic parameters.
European Spine Journal 11/2011; 21(4):719-24. · 1.97 Impact Factor
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ABSTRACT: Prospective and retrospective radiographic study of adult patients with spinal deformities.
Construct predictive models for pelvic tilt (PT) and global sagittal balance (sagittal vertical axis [SVA]) and evaluate the effectiveness of these predictive models against a group of patients after pedicle subtraction osteotomy.
Spinal balance involves a complex interaction between the pelvis and vertebral column. In the setting of adult spinal deformity, prediction of postoperative alignment can be challenging.
The study included 219 adult patients treated for spinal deformity. Full-length standing films were available for all subjects. Multilinear models with a stepwise condition were used on the first group of patients (n = 179) to predict PT and global sagittal balance (measured by the SVA). Prediction models were then applied on a second group of patients (n = 40) to estimate postoperative radiographic parameters after pedicle subtraction osteotomy surgery. Differences between estimated parameters and real values were evaluated.
Multilinear regression analysis applied on the first group of patients led to a predictive formula for PT (r = 0.93, standard error = 4.4°) using the following parameters: pelvic incidence, maximal lordosis, and maximal kyphosis. These parameters with the addition of the predicted PT were then used to predict the SVA (r = 0.89, standard error = 32 mm). Validation of predictive models (second group of patients) used pelvic incidence and postoperative sagittal curves. Postoperative PT was predicted with a mean error of 4.3° (SD 3.5°) and postoperative SVA was predicted with a mean error of 29 mm (SD = 23 mm).
This is the first study to develop and validate pragmatic predictive models for key spino-pelvic parameters (PT and SVA) in the setting of adult spinal deformity. Using a morphologic pelvic parameter (pelvic incidence) and spinal parameters modifiable through surgery (lumbar lordosis and thoracic kyphosis), postoperative sagittal alignment can be predicted.
Spine 01/2011; 36(13):1037-45. · 2.08 Impact Factor
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ABSTRACT: Using a tethering technique, a porcine model of scoliosis has been created. Ideally, tether release before placement and evaluation of corrective therapies would lead to persistent scoliosis.
Does release of the spinal tether result in persistent deformity?
Using a unilateral spinal tether and ipsilateral rib cage tethering, scoliosis was initiated on seven pigs. The spinal tether was released after progression to a Cobb angle of 50°. Biweekly radiographs were taken for 18 weeks after tether release to evaluate longitudinal changes in coronal and sagittal Cobb angles. Postmortem fine-cut CT scans were used to evaluate vertebral and disc wedging and axial rotation; results were compared to a previously published data set of 11 animals euthanized before release of the tether (control group).
Radiographic analysis demonstrated two responses to tether release: a persistent deformity group and an autocorrective group. Differences between these two groups included number of days with the tether in place before reaching a Cobb angle of 50° and degree of deformity immediately after scoliosis induction. CT analysis of the tether release versus tether intact groups demonstrated progression in vertebral body wedging without differences in apical rotation.
With the appropriate inducing parameters, release of the spinal tether does not systematically result in deformity correction. Tether release resulted in a reduction in Cobb angle in the first several weeks followed by steady curve progression. Deformity progression was confirmed using detailed CT morphometric analysis.
Clinical Orthopaedics and Related Research 01/2011; 469(5):1368-74. · 2.53 Impact Factor
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ABSTRACT: Current concepts review.
Outline the basic principles in the evaluation and treatment of adult spinal deformity patients with a focus on goals to achieve during surgical realignment surgery.
Proper global alignment of the spine is critical in maintaining standing posture and balance in an efficient and pain-free manner. Outcomes data demonstrate the clinical effect of spinopelvic malalignment and form a basis for realignment strategies.
Correlation between certain radiographic parameters and patient self-reported pain and disability has been established. Using normative values for several important spinopelvic parameters (including sagittal vertical axis, pelvic tilt, and lumbar lordosis), spinopelvic radiographic realignment objectives were identified as a tool for clinical application. Because of the complex relationship between the spine and the pelvis in maintaining posture and the wide range of "normal" values for the associated parameters, a focus on global alignment, with proportionality of individual parameters to each other, was pursued to provide clinical relevance to planning realignment for deformity across a range of clinical cases.
Good clinical outcome requires achieving proper spinopelvic alignment in the treatment of adult spinal deformity. Although variations in pelvic morphology exist, a framework has been established to determine ideal values for regional and global parameter in an individualized patient approach. When planning realignment surgery for adult spinal deformity, restoring low sagittal vertical axis and pelvic tilt values are critical goals, and should be combined with proportional lumbar lordosis to pelvic incidence.
Spine 12/2010; 35(25):2224-31. · 2.08 Impact Factor
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ABSTRACT: Adult spinal deformity is a complex structural musculoskeletal entity with variable presentation. Recent reports have found that pain and disability resulting from spinal deformity are primarily caused by sagittal malalignment. With increasing sagittal plane malalignment, patients typically complain of severe back pain, which is exacerbated with activity and substantially limits functional capacity. Radiographic acquisition of the sagittal plane requires capturing the spinopelvic axis from at least C7 proximally to the femoral heads distally on a single 36” long standing film. Because of the large range considered “normal”, regional alignment values alone are insufficient in assessing patient-specific alignment and the optimal values to strive for during spinal deformity realignment. It is thus important to consider the idea of spinopelvic harmony, which relates to the proportionality of one given regional parameter to another and in practical terms the global spinopelvic alignment of the individual. Several key surgical principles have been developed to optimize clinical outcomes during sagittal spinopelvic realignment surgery. These include obtaining sagittal vertical axis (SVA) <50 mm, pelvic tilt (PT) <20° and lumbar lordosis (LL)=PI±9°. Many methods for surgical realignment are available; however, to maximize the likelihood of a successful outcome it may be less important exactly what type of realignment technique is applied than to pursue proper analysis and execution of spinopelvic realignment. In many cases, a range of options may exist and the ultimate plan should be tempered by numerous factors, including surgeon expertise and patient co-morbidities. With thorough preoperative clinical and radiographic evaluations, awareness of general and patient-specific alignment objectives, and the surgical skills necessary to complete the task, spinopelvic realignment may then be pursued to optimize standing alignment for the symptomatic adult patient with spinal deformity.
Current Orthopaedic Practice 06/2010; 21(4):356-363.
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Jonathan R Kamerlink,
Thomas Errico,
Shaun Xavier, Ashish Patel,
Amar Patel,
Alexa Cohen,
Mark Reiger,
Joseph Dryer,
David Feldman,
Baron Lonner,
Aleksandar Beric,
Frank Schwab
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ABSTRACT: Retrospective review.
The purpose of this study was to assess the preoperative neurologic risk in a consecutive series of spinal deformity patients undergoing correction surgery at one institution.
During spinal deformity correction surgery, neurologic monitoring techniques are commonly applied to reduce the risk of neurologic deficits. While previous studies have demonstrated risk factors for neurologic changes in the setting of spinal surgery, these involved long time spans and heterogeneous patient populations.
Of 301 cases performed over 1 year, 281 cases were monitorable. Patients were grouped according to diagnosis: neuromuscular (NM) scoliosis, Sagittal Plane deformity, and Scoliosis. Demographic and surgical data were collected for neurologically monitorable patients. Coronal and sagittal parameters were measured using digital images of radiographs. Neurologic status was measured with somatosensory-evoked potentials and/or motor-evoked potentials.
Primary NM scoliosis cases had the highest incidence of neurologic monitoring changes (NMC) (10%) while revision sagittal plane deformity had the second highest (9.8%). Sensitivity and specificity were both 100%. Overall incidence of neurologic deficit was 1.1%. Of the 13 NMCs patients, 3 patients had persistent neurologic deficit. Majority of NMCs occurred before deformity correction. In patients with NM scoliosis, NMCs increased with hybrid constructs with wires (P < 0.01). In patients with scoliosis, NMCs increased with increased body mass index, estimated blood loss, operative time, and postoperative coronal thoracolumbar curve magnitude (P < 0.04). In patients with primarily sagittal plane deformity, NMCs increased with preoperative proximal curve, postoperative proximal and thoracolumbar curves, and postoperative kyphosis and lordosis (P < 0.04).
Primary NM scoliosis and revision sagittal plane deformities appear to carry greatest incidence of NMCs during surgical intervention. Most observed NMCs did not result in a permanent neurologic deficit. Neuromonitoring should be assessed throughout the entire surgical procedure. This study may aid surgeons and patients to better assess neurologic risks related to spinal deformity surgery.
Spine 01/2010; 35(2):240-5. · 2.08 Impact Factor
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ABSTRACT: Computed Tomographic Analysis of the Porcine Scoliosis Model.
To describe the spinal and rib cage modifications using computed tomography (CT).
Optimal development of nonfusion techniques for treatment of adolescent idiopathic scoliosis (AIS) requires a reliable large animal model that achieves spinal and rib cage modifications similar to AIS. Previous work has described the global 3-dimensional nature of the progressive deformity.
This IACUC-approved study includes 11 extracted scoliotic spines from a previous investigation. Scoliosis was induced through unilateral posterior ligament tethering of the spine via pedicle screw fixation, and ipsilateral rib cage tethering. CT analysis was used to quantify rib cage asymmetry, axial rotation, and wedging of the apical functional unit (2 vertebrae and intervening disc) for each specimen.
The mean coronal Cobb angle was 55.7 degrees (n = 11). Vertebral and intervertebral heights of the apical functional unit demonstrated convex heights (untethered) were always larger than concave (tethered) heights (P < 0.05). Axial rotation was maximal (mean, 20 degrees ) at 1 to 2 levels distal to the coronal apex. Maximal rib cage asymmetry was demonstrated at the transverse apex with significant coupling of the rotational and rib cage modifications (r = 0.82). A large initial Cobb index (tether tension) was significantly correlated with vertebral and intervertebral wedging and coronal curve progression.
The present study has used CT analysis to analyze spinal and rib cage modifications in the Porcine Scoliosis Model. Placement of a unilateral ligamentous spinal tether combined with concave rib cage ligament tethering during the rapid growth stage of the Yorkshire pig results in significant apical vertebral and intervertebral wedging and rotational and rib cage modifications. The porcine model is a reliable and duplicable model for scoliosis, which bears significant similarities to AIS.
Spine 01/2010; 35(1):18-25. · 2.08 Impact Factor
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ABSTRACT: Research update, focused review.
Identify the role of the pelvis in the setting of adults with spinal deformity.
Sagittal plane alignment is increasingly recognized as a critical parameter in the setting of adult spinal deformity. Additionally, pelvic parameters reveal to be a key component in the regulation of sagittal alignment.
Analysis of the pelvis in the sagittal plane is commonly assessed by 3 angular measurements: the pelvic incidence (morphologic parameter directly linked to sagittal morphotypes), the pelvic tilt (or pelvis retroversion used to maintain an upright posture in the setting of spinal deformity), and the sacral slope. Recent work using force plate technology has revealed that in the setting of anterior trunk inclination ("spinal imbalance"), the pelvis shifted posteriorly (toward the heels) in order to maintain a balanced mass distribution. The complex relationship between pelvic and spinal parameter were investigated in order to construct predictive formulas of postoperative spinopelvic alignment. It has emerged that pelvic tilt is highly correlated with patient self reported function (ODI, SF-12, and SRS).
It has become evident that good clinical outcome in the treatment of spinal deformity requires proper alignment. Pelvis parameters play an essential role not only in terms of spine morphotypes but also in regulating standing balance and postoperative alignment. Thus, optimal treatment of a patient with spinal deformity requires integration of the pelvis in the preoperative evaluation and treatment plan.
Spine 09/2009; 34(17):1828-33. · 2.08 Impact Factor
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ABSTRACT: Prospective radiographic and clinical analysis.
Investigate the relationship between spino-pelvic parameters and patient self reported outcomes on adult subjects with spinal deformities.
It is becoming increasingly recognized that the study of spinal alignment should include pelvic position. While pelvic incidence determines lumbar lordosis, pelvic tilt (PT) is a positional parameter reflecting compensation to spinal deformity. Correlation between plumbline offset (sagittal vertical axis [SVA]) and Health Related Quality of Life (HRQOL) measures has been demonstrated, but such a study is lacking for PT.
This prospective study was carried out on 125 adult patients suffering from spinal deformity (mean age: 57 years). Full-length free-standing radiographs including the spine and pelvis were available for all patients. HRQOL instruments included: Oswestry Disability Index, Short Form-12, Scoliosis Research Society. Correlation analysis between radiographic spinopelvic parameters and HRQOL measures was pursued.
Correlation analysis revealed no significance pertaining to coronal plane parameters. Significant sagittal plane correlations were identified. SVA and truncal inclination measured by T1 spinopelvic inclination (T1-SPI) (angle between T1-hip axis and vertical) correlated with: Scoliosis Research Society (appearance, activity, total score), Oswestry Disability Index, and Short Form-12 (physical component score). Correlation coefficients ranged from 0.42 < r < 0.55 (P < 0.0001). T1-SPI revealed greater correlation with HRQOL compared to SVA. PT showed correlation with HRQOL (0.28 < r < 0.42) and with SVA (r = 0.64, P < 0.0001).
This study confirms that pelvic position measured via PT correlates with HRQOL in the setting of adult deformity. High values of PT express compensatory pelvic retroversion for sagittal spinal malalignment. This study also demonstrates significant T1-SPI correlation with HRQOL measures and outperforms SVA. This parameter carries the advantage of being an angular measurement which avoids the error inherent in measuring offsets in noncalibrated radiographs.
Spine 08/2009; 34(17):E599-606. · 2.08 Impact Factor
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ABSTRACT: An IACUC-approved study to create a scoliotic deformity representative of adolescent idiopathic scoliosis.
The goal of this study was to develop a reliable porcine scoliosis model and to evaluate the three-dimensional progression of the deformity.
Optimal development of nonfusion techniques for treatment of adolescent idiopathic scoliosis requires a reliable large animal model that achieves a progressive three-dimensional (frontal, sagittal, axial) deformity. Limitations in previous work have led our team to the development of a porcine model.
This IACUC-approved study included 18 Yorkshire pigs, obtained at 11 weeks old. Scoliosis was induced through unilateral posterior ligament tethering of the spine via pedicle screw fixation, and ipsilateral ribcage tethering. Progressive deformity was documented with biweekly radiographs. Frontal, sagittal, and axial modifications were assessed using the Cobb method. Animals were observed until severe deformity (>50 degrees) developed, then killed.
Animals were observed for a mean 11 weeks. The mean coronal Cobb angle was 25 degrees immediately postoperatively and 55 degrees at 11 weeks. The mean lordosis increased from 4 degrees postoperative to 24 degrees at final follow-up. Apical axial rotation (posterior elements into concavity) increased from 4% postoperative to 27% at 11 weeks. Rate of coronal curve progression was significantly correlated with the initial Cobb index.
This study establishes a porcine scoliosis model. With placement of a unilateral ligamentous spinal tether combined with concave ribcage ligament tethering a three-dimensional (frontal, sagittal, and axial) spinal deformity can be obtained. The speed of the progressive deformity leaves significant remaining skeletal growth to assess growth modulating therapies for correction. This work forms the basis for a number of investigative efforts at developing new fusionless therapies for patients suffering from adolescent scoliosis.
Spine 06/2009; 34(11):E397-404. · 2.08 Impact Factor
