Investigating the change in three dimensional deformity for idiopathic scoliosis using axially loaded MRI

Background

Adolescent idiopathic scoliosis is a complex three-dimensional deformity, involving a lateral deformity in the coronal plane and axial rotation of the vertebrae in the transverse plane. Gravitational loading plays an important biomechanical role in governing the coronal deformity, however, less is known about how they influence the axial deformity. This study investigates the change in three-dimensional deformity of a series of scoliosis patients due to compressive axial loading.

Methods

Magnetic resonance imaging scans were obtained and coronal deformity (measured using the coronal Cobb angle) and axial rotations measured for a group of 18 scoliosis patients (Mean major Cobb angle was 43.4^o). Each patient was scanned in an unloaded and loaded condition while compressive loads equivalent to 50% body mass were applied using a custom developed compressive device.

Findings

The mean increase in major Cobb angle due to compressive loading was 7.4^o (SD 3.5^o). The most axially rotated vertebra was observed at the apex of the structural curve and the largest average intravertebral rotations were observed toward the limits of the coronal deformity. A level-wise comparison showed no significant difference between the average loaded and unloaded vertebral axial rotations (intra-observer error = 2.56^o) or intravertebral rotations at each spinal level.

Interpretation

This study suggests that the biomechanical effects of axial loading primarily influence the coronal deformity, with no significant change in vertebral axial rotation or intravertebral rotation observed between the unloaded and loaded condition. However, the magnitude of changes in vertebral rotation with compressive loading may have been too small to detect given the resolution of the current technique.     

Remodelling of vertebral endplate subchondral bone in scoliosis: A micro-CT analysis in a porcine model

Background

Disc degeneration has been correlated with alteration of bone density of adjacent vertebral bodies. Abnormal mechanical loading appears in scoliosis as compared to normal spines. How vertebral endplate was remodelled in scoliosis is not well understood.

Methods

We conducted a micro-CT analysis of subchondral bone of the vertebral endplate at the curve apex in a porcine scoliosis model. Two adjacent thoracic T₅–T₆ and lumbar L₁–L₂ levels were instrumented in six four-week-old pigs with a custom offset implant connected by a flexible stainless steel wire. Two months after implantation, three cylindrical specimens were harvested into the vertebral endplate of each of the scoliosis levels: centre, convexity and concavity, and from the dorsal T₉–T₁₀ vertebral units obtained from nine three-month-old non-instrumented pigs used as controls. Micro-CT analysis was carried out on each specimen.

Findings

In the concavity of the scoliotic spine, bone volume fraction, trabecular thickness, and trabecular separation significantly increased whereas in the convexity, only trabecular separation increased. Connectivity index and trabecular number decreased significantly.

Interpretation

This was the first micro-CT study of subchondral bone microarchitecture of the scoliotic vertebral end plate. At the curve apex, increased compression in the concavity induced an osteogenic process. In the convexity, diminished compression caused an osteolytic process with a local resorption. Clinically, the unbalanced tissue remodelling could play a role in the convective and diffusive transports into the end plate, which is of prime importance for the segment homeostasis in scoliosis treatment with or without surgery.     

Biomechanical modeling of the lateral decubitus posture during corrective scoliosis surgery

Background

Patient prone positioning in scoliosis surgeries modifies the spinal curves prior to instrumentation. However, the biomechanical effects of the lateral decubitus posture, used in anterior approaches and minimally invasive techniques, have not yet been investigated. The objectives were to develop and validate a finite element model simulating the spinal changes resulting from this positioning.

Methods

The 3D pre-op reconstructed geometries of six adolescent patients with idiopathic scoliosis were used to develop personalized finite element models of the spine, which integrated a three-step method simulating the lateral posture. Clinical indices were measured on pre- and intra-operative radiographs to validate the finite element model.

Findings

The major Cobb angle and apical vertebral translation were reduced by 44% and 37% respectively between the pre- and intra-op postures. Using appropriately oriented gravity forces and boundary conditions, the finite element model simulations represented adequately these changes, with average differences of 4° for the major Cobb angle and 4 mm for the apical vertebral translation with the radiographic values.

Interpretation

Lateral decubitus positioning significantly reduces the spinal deformities prior to instrumentation, as demonstrated by the finite element model. This study is a first step in the development of a modeling tool for the optimal adjustments of intra-operative positioning, which remains to be further investigated with complementary clinical studies.     

Females exhibit shorter paraspinal reflex latencies than males in response to sudden trunk flexion perturbations

Background

Females have a higher risk of experiencing low back pain or injury than males. One possible reason for this might be altered reflexes since longer paraspinal reflex latencies exist in injured patients versus healthy controls. Gender differences have been reported in paraspinal reflex latency, yet findings are inconsistent. The goal here was to investigate gender differences in paraspinal reflex latency, avoiding and accounting for potentially gender-confounding experimental factors.

Methods

Ten males and ten females underwent repeated trunk flexion perturbations. Paraspinal muscle activity and trunk kinematics were recorded to calculate reflex latency and maximum trunk flexion velocity. Two-way mixed model analyses of variance were used to determine the effects of gender on reflex latency and maximum trunk flexion velocity.

Findings

Reflex latency was 18.7% shorter in females than in males (P = 0.02) when exposed to identical trunk perturbations, and did not vary by impulse (P = 0.38). However, maximum trunk flexion velocity was 35.3% faster in females than males (P = 0.01) when exposed to identical trunk perturbations, and increased with impulse (P < 0.01). While controlling for differences in maximum trunk flexion velocity, reflex latency was 16.4% shorter in females than males (P = 0.04).

Interpretation

The higher prevalence of low back pain and injury among females does not appear to result from slower paraspinal reflexes.     

Creation of an asymmetrical gradient of back muscle activity and spinal stiffness during asymmetrical hip extension

Background

Low back pain is often associated with increased spinal stiffness which thought to arise from increased muscle activity. Unfortunately, the association between paraspinal muscle activity and paraspinal stiffness, as well as the spatial distribution of this relation, is unknown. The purpose of this investigation was to employ new technological developments to determine the relation between spinal muscle contraction and spinal stiffness over a large region of the lumbar spine.

Methods

Thirty-two male subjects performed graded isometric prone right hip extension at four different exertion levels (0%, 10%, 25% and 50% of the maximum voluntary contraction) to induce asymmetric back muscle activity. The corresponding stiffness and muscle activity over bilateral paraspinal lumbar regions was measured by indentation loading and topography surface electromyography, respectively. Paraspinal stiffness and muscle activity were then plotted and their correlation was determined.

Findings

Data from this study demonstrated the existence of an asymmetrical gradient in muscle activation and paraspinal stiffness in the lumbar spine during isometric prone right hip extension. The magnitude and scale of the gradient increased with the contraction force. A positive correlation between paraspinal stiffness and paraspinal muscle activity existed irrespective of the hip extension effort (Pearson correlation coefficient, range 0.566–0.782 (P < 0.001)).

Interpretation

Our results demonstrate the creation of an asymmetrical gradient of muscle activity and paraspinal stiffness during right hip extension. Future studies will determine if alterations in this gradient may possess diagnostic or prognostic value for patients with low back pain.     

Segmental torso masses in adolescent idiopathic scoliosis

Background

Adolescent idiopathic scoliosis is the most common type of spinal deformity whose aetiology remains unclear. Studies suggest that gravitational forces in the standing position play an important role in scoliosis progression, therefore anthropometric data is required to develop biomechanical models of the deformity. Few studies have analysed the trunk by vertebral level and none have performed investigations of the scoliotic trunk. The aim of this study was to determine the centroid, thickness, volume and estimated mass, for sections of the scoliotic trunk.

Methods

Existing low-dose CT scans were used to estimate vertebral level-by-level torso masses for 20 female adolescent idiopathic scoliosis patients. ImageJ processing software was used to analyse the CT images and enable estimation of the segmental torso mass corresponding to each vertebral level.

Findings

The patients' mean age was 15.0 (SD 2.7) years with mean major Cobb angle of 52 (SD 5.9)° and mean patient weight of 58.2 (SD 11.6) kg. The magnitude of torso segment mass corresponding to each vertebral level increased by 150% from 0.6 kg at T1 to 1.5 kg at L5. Similarly, segmental thickness from T1–L5 increased inferiorly from a mean 18.5 (SD 2.2) mm at T1 to 32.8 (SD 3.4) mm at L5. The mean total trunk mass, as a percentage of total body mass, was 27.8 (SD 0.5) % which was close to values reported in previous literature.

Interpretation

This study provides new anthropometric reference data on segmental (vertebral level-by-level) torso mass in adolescent idiopathic scoliosis patients, useful for biomechanical models of scoliosis progression and treatment.     

New brace design combining CAD/CAM and biomechanical simulation for the treatment of adolescent idiopathic scoliosis

Background

A numerical based brace design platform, including biomechanical simulation, Computer Aided Design and Computer Aided Manufacturing (CAD/CAM) was developed to rationalize braces for the treatment of adolescent idiopathic scoliosis. The objective of this study was to test the feasibility of the approach and assess the effectiveness of braces issued from this platform as compared to standard brace design.

Methods

The biomechanical finite element model was built using the 3D reconstruction of the trunk skeleton from bi-planar radiographs and of the torso surface from surface topography. The finite element model is linked to a CAD/CAM software (Rodin4D), allowing the iterative design and simulation of the correction provided by the brace, as well as predicting pressures exerted on the torso. The resulting brace design was then fabricated using a numerical controlled carver. A brace designed using this platform (New Brace) as well as a standard thoraco-lumbo-sacral orthosis (Standard Brace) were built for six scoliotic patients. Both brace effectiveness was assessed using radiographs and compared to the simulations.

Findings

The New Brace corrected on average the spine deformities within 5° of Cobb angle of the simulated correction and with a similar correction as compared to the Standard Brace (average correction of 16° vs. 11° (MT); P = 0.1 and 13° vs. 16° (TL/L); P = 0.5 for the Standard Brace and the New Brace respectively). The two braces had a similar 10° lordosing effect of the thoracic curve. The coronal balance was quite similar (7.3 vs. 6.8 mm balance improvement respectively for New Brace vs. Standard Brace).

Interpretation

These first clinical results showed the feasibility of building computer-assisted braces, equivalent to standard orthosis. An extended study on more cases is under way to fully assess this new design paradigm, which in the long term would allow improving brace design and rationalize the conservative treatments of scoliosis.     

Relationship of forces acting on implant rods and degree of scoliosis correction

Background

Adolescent idiopathic scoliosis is a complex spinal pathology characterized as a three-dimensional spine deformity combined with vertebral rotation. Various surgical techniques for correction of severe scoliotic deformity have evolved and became more advanced in applying the corrective forces. The objective of this study was to investigate the relationship between corrective forces acting on deformed rods and degree of scoliosis correction.

Methods

Implant rod geometries of six adolescent idiopathic scoliosis patients were measured before and after surgery. An elasto-plastic finite element model of the implant rod before surgery was reconstructed for each patient. An inverse method based on Finite Element Analysis was used to apply forces to the implant rod model such that it was deformed the same after surgery. Relationship between the magnitude of corrective forces and degree of correction expressed as change of Cobb angle was evaluated. The effects of screw configuration on the corrective forces were also investigated.

Findings

Corrective forces acting on rods and degree of correction were not correlated. Increase in number of implant screws tended to decrease the magnitude of corrective forces but did not provide higher degree of correction. Although greater correction was achieved with higher screw density, the forces increased at some level.

Interpretation

The biomechanics of scoliosis correction is not only dependent to the corrective forces acting on implant rods but also associated with various parameters such as screw placement configuration and spine stiffness. Considering the magnitude of forces, increasing screw density is not guaranteed as the safest surgical strategy.     

Effects of Bracing in Adult With Scoliosis: A Retrospective Study

Objective

To assess the effectiveness of bracing in adult with scoliosis.

Prevalence and Predictors of Adolescent Idiopathic Scoliosis in Adolescent Ballet Dancers

Objective

To determine any differences between the prevalence of adolescent idiopathic scoliosis in ballet dancers who are girls compared with age-matched nondancers, and to establish if any relations exist between the presence of scoliosis and generalized joint hypermobility, age of menarche, body mass index (BMI), and the number of hours of dance training per week.

Design

Cross-sectional, matched pair study.

Setting

Dance school.

Participants

Dancers (n=30) between the ages of 9 and 16 years were recruited from a certified dance school in Western Australia; each dancer provided a consenting age-matched nondancer (n=30).

Interventions

Not applicable.

Main Outcome Measures

Measurements were taken for angle of trunk rotation using a scoliometer (presence of scoliosis) and for height and weight to produce generalized joint hypermobility using Beighton criteria and an age-adjusted BMI, respectively. A subjective questionnaire regarding age of menarche and participation in dance and other sports was completed.

Results

Thirty percent of dancers tested positive for scoliosis compared with 3% of nondancers. Odds ratio calculations suggest that dancers were 12.4 times more likely to have scoliosis than nondancers of the same age. There was a higher rate of hypermobility in the dancer group (70%) compared with the nondancers (3%); however, there were no statistically significant relations between scoliosis and hypermobility, age of menarche, BMI, or hours of dance per week.

Conclusions

Adolescent dancers, similar to adult dancers, are at significantly higher risk of developing scoliosis than nondancers of the same age. Vigilant screening and improved education of dance teachers and parents of dance students may be beneficial in earlier detection and, consequently, reducing the risk of requiring surgical intervention.     

Bone properties by nanoindentation in mild and severe osteogenesis imperfecta

Background

Osteogenesis imperfecta is a heterogeneous genetic disorder characterized by bone fragility. Previous research suggests that impaired collagen network and abnormal mineralization affect bone tissue properties, however, little data is yet available to describe bone material properties in individuals with this disorder. Bone material properties have not been characterized in individuals with the most common form of osteogenesis imperfecta, type I.

Methods

Bone tissue elastic modulus and hardness were measured by nanoindentation in eleven osteotomy specimens that were harvested from children with osteogenesis imperfecta during routine surgeries. These properties were compared between osteogenesis imperfecta types I (mild, n = 6) and III (severe, n = 5), as well as between interstitial and osteonal microstructural regions using linear mixed model analysis.

Findings

Disease severity type had a small but statistically significant effect on modulus (7%, P = 0.02) and hardness (8%, P < 0.01). Individuals with osteogenesis imperfecta type I had higher modulus and hardness than did those with type III. Overall, mean modulus and hardness values were 13% greater in interstitial lamellar bone regions than in osteonal regions (P < 0.001).

Interpretation

The current study presents the first dataset describing bone material properties in individuals with the most common form of osteogenesis imperfecta, i.e., type I. Results indicate that intrinsic bone tissue properties are affected by phenotype. Knowledge of the material properties of bones in osteogenesis imperfecta will contribute to the ability to develop models to assist in predicting fracture risk.     

Out-of-hospital cardiac arrest outcomes stratified by rhythm analysis

Background

Survival data for out-of-hospital cardiac arrest (OHCA) victims initially in PEA or asystole who convert to a shockable rhythm during attempted resuscitation, relative to an initial shockable rhythm, have never been previously reported. This study was done to assess OHCA outcomes among a large cohort of adults in the CARES dataset stratified by three rhythm categories: initial shockable (IS), converted shockable (CS), and never shockable (NS).

Methods

The study was IRB approved. All adult index events at participating sites (2005–2010) were study eligible. All patient data elements were provided. Odds ratios of CS and NS status for survival to hospital discharge were calculated via multivariate logistic regression that adjusted for demographics, site, resuscitation initiators, AED use, and other covariates.

Results

There were 40,274 OHCA records submitted to the CARES registry during the study period. After exclusions, our final sample size was 30,939 (7404 IS [23.9%], 3225 CS [10.4%], 20,310 NS [65.7%]). Raw survival rates of CS and NS patients were similar (4.7% vs. 4.1%, respectively; p = 0.08) but significantly lower than IS patients (26.9%; p < 0.001). The adjusted OR of survival to hospital discharge for CS was 0.17 (95%CI: 0.14, 0.20) and for NS it was 0.17 (95%CI: 0.15, 0.18) with IS as the referent.

Conclusion

After OHCA, the survival rate for CS victims is significantly lower than for IS patients. These findings suggest that CS and IS are different entities and that alternatives to existing resuscitation algorithm tailored to patients with CS should be investigated.     

Serum level and prognostic value of neopterin in patients after ischemic stroke

Background

We hypothesized that serum level of neopterin is significantly predictive of prognostic outcome in patients after acute ischemic stroke (IS).

Methods

Between November 2008 and May 2010, serum levels of neopterin were prospectively collected at 48 h after acute IS in 157 patients.

Results

Serum neopterin levels were substantially higher in patients with severe neurological impairment [National institutes of Health Stroke Scale (NIHSS) score ≥ 12] than in those with NIHSS < 12 (p < 0.008). Furthermore, Spearman's test showed a strongly positive correlation between neopterin level and NIHSS (p = 0.003). Multiple logistic regression analysis demonstrated that serum neopterin level was strongly and independently predictive of NIHSS ≥ 12 (p = 0.002) at 48 h after acute IS and 90-day major adverse clinical outcome (defined as NIHSS ≥ 12, recurrent stroke or death) (p = 0.003).

Conclusion

Serum level of neopterin was notably increased after acute IS. This biomarker was strongly and independently predictive of 90-day unfavorable clinical outcome in patients after acute IS.     

Effects of Stimulating Hip and Trunk Muscles on Seated Stability,Posture, and Reach After Spinal Cord Injury

Objective

To determine the stimulated strength of the paralyzed gluteal and paraspinal muscles and their effects on the seated function of individuals with paralysis.

Design

Case series with subjects acting as their own concurrent controls.

Setting

Hospital-based clinical biomechanics laboratory.

Participants

Users (N=8) of implanted neuroprostheses for lower extremity function with low-cervical or thoracic level injuries.

Interventions

Dynamometry and digital motion capture both with and without stimulation to the hip and trunk muscles.

Main Outcome Measures

Isometric trunk extension moment at 0°, 15°, and 30° of flexion; seated stability in terms of simulated isokinetic rowing; pelvic tilt, shoulder height, loaded and unloaded bimanual reaching to different heights, and subjective ratings of difficulty during unsupported sitting.

Results

Stimulation produced significant increases in mean trunk extension moment (9.2±9.5Nm, P<.001) and rowing force (27.4±23.1N, P<.012) over baseline volitional values. Similarly, stimulation induced positive changes in average pelvic tilt (16.7±15.7°) and shoulder height (2.2±2.5cm) during quiet sitting and bimanual reaching, and increased mean reach distance (5.5±6.6cm) over all subjects, target heights, and loading conditions. Subjects consistently rated tasks with stimulation easier than voluntary effort alone.

Conclusions

In spite of considerable intersubject variability, stabilizing the paralyzed trunk with electrical stimulation can positively impact seated posture, extend forward reach, and allow exertion of larger forces on objects in the environment.     

Biomechanical loading of the sacrum in adolescent idiopathic scoliosis

Background

The pelvis maintains an important role in transferring loads from the upper body to the lower extremities and hence contributes to the standing postural balance. Even though changes in spino-pelvic relative alignment are involved in the pathophysiology of scoliosis, the mechanism through which the transferred load between the spine and pelvis is related to the spinal deformity is not well understood.

Methods

A personalized finite element model of the spine and pelvis was constructed for 11 right main thoracic and 23 left thoracolumbar/lumbar adolescent idiopathic scoliosis and 12 asymptomatic controls. The compressive stress distribution on the sacrum endplate was computed. The position of the stress distribution barycenter on the sacrum superior endplate in reference to the central hip vertical axis was projected on the transverse plane and compared between scoliotic subgroups and controls.

Findings

The medio-lateral position of the stress distribution barycenter on the sacrum superior endplate was significantly different between the scoliotic subgroups and controls (p < 0.05). The stress distribution barycenter on the sacrum superior endplate was located at the right side of the central hip vertical axis in 82% of the right main thoracic patients and to the left side of the central hip vertical axis in 91% of the left thoracolumbar/lumbar patients.

Interpretation

Analysis of the transferred load to the sacrum provided insight into the biomechanical spino-pelvic interaction in 3D, showing that a thoracolumbar/lumbar scoliotic curve has an increased influence on sacral loads when compared to a main thoracic scoliotic curve.     

Influence of growth modulation on the effective permeability of the vertebral end plate. A porcine experimental scoliosis model

Background

Abnormal mechanical loading occurs in scoliosis as compared to normal spines. Intervertebral disc degeneration has been correlated with alteration of bone density in adjacent vertebral bodies. How vertebral end plate remodels in scoliosis and the consequences on disc homeostasis are not well understood. Permeability is a relevant physical measure to quantify mass transport in porous media. We hypothesized that effective permeability of the vertebral end plate was modified by growth modulation in a scoliosis animal model.

Methods

Flexible asymmetric posterior instrumentation was undertaken on six healthy four-week-old pigs. Two sets of left pedicle screws were inserted and connected with a stainless steel cable. After two months, the apical intervertebral unit and three units located cranially and caudally, were harvested. One central and two lateral specimens were investigated using a previously validated method for measuring permeability.

Findings

A three-dimensional deformity was obtained in all six animals with an average of 42° right thoracic curve, 44° lordosis and 21° rotation. Permeability was significantly greater in the center of the end plates than in the periphery and it was decreased by − 45% towards the apex of the deformity. Fluid flow direction did not play a significant role. No significant difference was found between the convex side and the concave side.

Interpretation

The end plate is a crucial zone for diffusive and convective transport and we showed in a scoliosis animal model that a growth modulation may decrease its effective permeability. The proposed methodology and associated results could help to understand degenerative changes in human spine.     

The Role of Preload Forces in Spinal Manipulation: Experimental Investigation of Kinematic and Electromyographic Responses in Healthy Adults

Objectives

Previous studies have identified preload forces and an important feature of skillful execution of spinal manipulative therapy (SMT) as performed by manual therapists (eg, doctors of chiropractic and osteopathy). It has been suggested that applying a gradual force before the thrust increases the spinal unit stiffness, minimizing displacement during the thrust. Therefore, the main objective of this study was to assess the vertebral unit biomechanical and neuromuscular responses to a graded increase of preload forces.

Methods

Twenty-three participants underwent 4 different SMT force-time profiles delivered by a servo-controlled linear actuator motor and varying in their preload forces, respectively, set to 5, 50, 95, and 140 N in 1 experimental session. Kinematic markers were place on T6, T7, and T8 and electromyographic electrodes were applied over paraspinal muscles on both sides of the spine.

Results

Increasing preload forces led to an increase in neuromuscular responses of thoracic paraspinal muscles and vertebral segmental displacements during the preload phase of SMT. Increasing the preload force also yielded a significant decrease in sagittal vertebral displacement and paraspinal muscle activity during and immediately after the thrust phase of spinal manipulation. Changes observed during the SMT thrust phase could be explained by the proportional increase in preload force or the related changes in rate of force application. Although only healthy participants were tested in this study, preload forces may be an important parameter underlying SMT mechanism of action. Future studies should investigate the clinical implications of varying SMT dosages.

Conclusion

The present results suggest that neuromuscular and biomechanical responses to SMT may be modulated by preload through changes in the rate of force application. Overall, the present results suggest that preload and rate of force application may be important parameters underlying SMT mechanism of action.     

Physiological Responses to Spinal Manipulation Therapy: Investigation of the Relationship Between Electromyographic Responses and Peak Force

Objective

It is believed that systematic modulation of spinal manipulative therapy (SMT) parameters should yield varying levels of physiological responses and eventually a range of clinical responses. However, investigation of SMT dose–physiological response relationship is recent and has mostly been conducted using animal or cadaveric models. The main objective of the present study is to investigate SMT dose–physiological response relation in humans by determining how different levels of force can modify electromyographic (EMG) responses to spinal manipulation.

Methods

Twenty-six participants were subjected to 2 trials of 4 different SMT force-time profiles using a servo-controlled linear actuator motor. Normalized EMG activity of paraspinal muscles (left and right muscles at level T6 and T8) was recorded during and after SMT, and EMG values were compared across the varying levels of force.

Results

Increasing the level of force yielded an increase in paraspinal muscle EMG activity during the thrust phase of SMT but also in the two 250-millisecond time windows after the spinal manipulation impulse. These muscle activations quickly attenuated (500 milliseconds after spinal manipulation impulse).

Conclusion

The study confirmed the presence of a local paraspinal EMG response after SMT and highlighted the linear relationship between the SMT peak force and paraspinal muscle activation.     

Three-dimensional stereoradiographic modeling of rib cage before and after spinal growing rod procedures in early-onset scoliosis

Background

Early-onset scoliosis frequently leads to major thoracic deformity and pulmonary restrictive disease. Growing rods surgical techniques were developed to achieve a satisfactory correction of the spinal curves during growth. The effect on the rib cage deformity has not yet been documented. The purpose of this study was to analyze the changes of the thoracic geometry after implantation of a growing rod, and to evaluate a stereoradiographic reconstruction method among young scoliotic patients.

Methods

Four patients were enrolled in the study, and four additional patients in the reproducibility study. Three-dimensional spine and rib cage models were generated after low-dose stereoradiographic imaging (EOS). Three-dimensional parameters were computed before and after surgery. Intra and inter-observer reproducibility was calculated, and the accuracy was assessed in comparison to volumetric CT-scan.

Findings

The average Cobb angle was reduced from 50.8° to 26°. The surgery resulted in a complex 3D effect on the rib cage, combining frontal, lateral, and axial rotation. This effect was dependent of the side (concave or convex), and the position relative to the apical vertebra. Mean errors in comparison to CT-scan were 3.5 mm.

Interpretation

The results on the spinal deformity are comparable to other series. The effect on the rib cage is of a smaller magnitude than in the case of a spinal arthrodesis. A longer follow-up is necessary to confirm the positive effect on the rib cage deformity. Further research should be performed to improve the reproducibility of 3D parameters.     

Effects of Unilateral Facet Fixation and Facetectomy on Muscle Spindle Responsiveness During Simulated Spinal Manipulation in an Animal Model

Objectives

Manual therapy practitioners commonly assess lumbar intervertebral mobility before deciding treatment regimens. Changes in mechanoreceptor activity during the manipulative thrust are theorized to be an underlying mechanism of spinal manipulation (SM) efficacy. The objective of this study was to determine if facet fixation or facetectomy at a single lumbar level alters muscle spindle activity during 5 SM thrust durations in an animal model.

Methods

Spinal stiffness was determined using the slope of a force-displacement curve. Changes in the mean instantaneous frequency of spindle discharge were measured during simulated SM of the L₆ vertebra in the same 20 afferents for laminectomy-only and 19 laminectomy and facet screw conditions; only 5 also had data for the laminectomy and facetectomy condition. Neural responses were compared across conditions and 5 thrust durations (≤ 250 milliseconds) using linear-mixed models.

Results

Significant decreases in afferent activity between the laminectomy-only and laminectomy and facet screw conditions were seen during 75-millisecond (P < .001), 100-millisecond (P = .04), and 150-millisecond (P = .02) SM thrust durations. Significant increases in spindle activity between the laminectomy-only and laminectomy and facetectomy conditions were seen during the 75-millisecond (P < .001) and 100-millisecond (P < .001) thrust durations.

Conclusion

Intervertebral mobility at a single segmental level alters paraspinal sensory response during clinically relevant high-velocity, low-amplitude SM thrust durations (≤ 150 milliseconds). The relationship between intervertebral joint mobility and alterations of primary afferent activity during and after various manual therapy interventions may be used to help to identify patient subpopulations who respond to different types of manual therapy and better inform practitioners (eg, chiropractic and osteopathic) delivering the therapeutic intervention.