An FE investigation simulating intra-operative corrective forces applied to correct scoliosis deformity

Background: Adolescent idiopathic scoliosis (AIS) is a deformity of the spine, which may 34 require surgical correction by attaching a rod to the patient’s spine using screws 35 implanted in the vertebral bodies. Surgeons achieve an intra-operative reduction in the 36 deformity by applying compressive forces across the intervertebral disc spaces while 37 they secure the rod to the vertebra. We were interested to understand how the 38 deformity correction is influenced by increasing magnitudes of surgical corrective forces 39 and what tissue level stresses are predicted at the vertebral endplates due to the 40 surgical correction. 41 Methods: Patient-specific finite element models of the osseoligamentous spine and 42 ribcage of eight AIS patients who underwent single rod anterior scoliosis surgery were 43 created using pre-operative computed tomography (CT) scans. The surgically altered 44 spine, including titanium rod and vertebral screws, was simulated. The models were 45 analysed using data for intra-operatively measured compressive forces – three load 46 profiles representing the mean and upper and lower standard deviation of this data 47 were analysed. Data for the clinically observed deformity correction (Cobb angle) were 48 compared with the model-predicted correction and the model results investigated to 49 better understand the influence of increased compressive forces on the biomechanics of 50 the instrumented joints. 51 Results: The predicted corrected Cobb angle for seven of the eight FE models were 52 within the 5° clinical Cobb measurement variability for at least one of the force profiles. 53 The largest portion of overall correction was predicted at or near the apical 54 intervertebral disc for all load profiles. Model predictions for four of the eight patients 55 showed endplate-to-endplate contact was occurring on adjacent endplates of one or 56 more intervertebral disc spaces in the instrumented curve following the surgical loading 57 steps. 58 Conclusion: This study demonstrated there is a direct relationship between intra-59 operative joint compressive forces and the degree of deformity correction achieved. The 60 majority of the deformity correction will occur at or in adjacent spinal levels to the apex 61 of the deformity. This study highlighted the importance of the intervertebral disc space 62 anatomy in governing the coronal plane deformity correction and the limit of this 63 correction will be when bone-to-bone contact of the opposing vertebral endplates 64 occurs.

Inter-vertebral rotational deformity after endoscopic anterior scoliosis correction may contribute to rib hump recurrence after two years

Introduction. Endoscopic anterior scoliosis correction has been employed recently as a less invasive and level-sparing approach compared with open surgical techniques. We have previously demonstrated that during the two-year post-operative period, there was a mean loss of rib hump correction by 1.4 degrees. The purpose of this study was to determine whether intra- or inter-vertebral rotational deformity during the post-operative period could account for the loss of rib hump correction. Materials and Methods. Ten consecutive patients diagnosed with adolescent idiopathic scoliosis were treated with an endoscopic anterior scoliosis correction. Low-dose computed tomography scans of the instrumented segment were obtained post-operatively at 6 and 24 months following institutional ethical approval and patient consent. Three-dimensional multi-planar reconstruction software (Osirix Imaging Software, Pixmeo, Switzerland) was used to create axial slices of each vertebral level, corrected in both coronal and sagittal planes. Vertebral rotation was measured using Ho’s method for every available superior and inferior endplate at 6 and 24 months. Positive changes in rotation indicate a reduction and improvement in vertebral rotation. Intra-observer variability analysis was performed on a subgroup of images. Results. Mean change in rotation for vertebral endplates between 6 and 24 months post-operatively was -0.26˚ (range -3.5 to 4.9˚) within the fused segment and +1.26˚ (range -7.2 to 15.1˚) for the un-instrumented vertebrae above and below the fusion. Mean change in clinically measured rib hump for the 10 patients was -1.6˚ (range -3 to 0˚). The small change in rotation within the fused segment accounts for only 16.5% of the change in rib hump measured clinically whereas the change in rotation between the un-instrumented vertebrae above and below the construct accounts for 78.8%. There was no clear association between rib hump recurrence and intra- or inter-vertebral rotation in individual patients. Intra-rater variability was ± 3˚. Conclusions. Intra- and inter-vertebral rotation continues post-operatively both within the instrumented and un-instrumented segments of the immature spine. Rotation between the un-instrumented vertebrae above and below the fusion was +1.26˚, suggesting that the un-instrumented vertebrae improved and de-rotated slightly after surgery. This may play a role in rib hump recurrence, however this remains clinically insignificant.

Postoperative pain relief using intermittent intrapleural analgesia following thoracoscopic anterior correction for progressive adolescent idiopathic scoliosis

Background Thoracoscopic anterior scoliosis instrumentation is a safe and viable surgical option for corrective fusion of progressive adolescent idiopathic scoliosis (AIS) and has been performed at our centre on 205 patients since 2000. However, there is a paucity of literature reporting on or examining optimum methods of analgesia following this type of surgery. A retrospective study was designed to present the authors’ technique for delivering intermittent local anaesthetic boluses via an intrapleural catheter following thoracoscopic scoliosis surgery; report the pain levels that may be expected and any adverse effects associated with the use of intrapleural analgesia, as part of a combined postoperative analgesia regime. Methods Records for 32 patients who underwent thoracoscopic anterior correction for AIS were reviewed. All patients received an intrapleural catheter inserted during surgery, in addition to patient-controlled opiate analgesia and oral analgesia. After surgery, patients received a bolus of 0.25% bupivacaine every four hours via the intrapleural catheter. Patient’s perceptions of their pain control was measured using the visual analogue pain scale scores which were recorded before and after local anaesthetic administration and the quantity and time of day that any other analgesia was taken, were also recorded. Results 28 female and four male patients (mean age 14.5 ± 1.5 years) had a total of 230 boluses of local anaesthetic administered in the 96 hour period following surgery. Pain scores significantly decreased following the administration of a bolus (p < 0.0001), with the mean pain score decreasing from 3.66 to 1.83. The quantity of opiates via patient-controlled analgesia after surgery decreased steadily between successive 24 hours intervals after an initial increase in the second 24 hour period when patients were mobilised. One intrapleural catheter required early removal due to leakage; there were no other associated complications with the intermittent intrapleural analgesia method. Conclusions Local anaesthetic administration via an intrapleural catheter is a safe and effective method of analgesia following thoracoscopic anterior scoliosis correction. Post-operative pain following anterior thoracic scoliosis surgery can be reduced to ‘mild’ levels by combined analgesia regimes. Keywords: Adolescent idiopathic scoliosis; Thoracoscopic anterior spinal fusion; Anterior fusion; Intrapleural analgesia; Endoscopic anterior surgery; Pain relief; Scoliosis surgery

Is intermittent intrapleural analgesia safe and effective following thoracoscopic anterior scoliosis correction surgery?

Introduction: Thoracoscopic anterior instrumented fusion (TASF) is a safe and viable surgical option for corrective stabilisation of progressive adolescent idiopathic scoliosis (AIS) [1-2]. However, there is a paucity of literature examining optimum methods of analgesia following this type of surgery. The aim of this study was to identify; if local anaesthetic bolus via an intrapleural catheter provides effective analgesia following thoracoscopic scoliosis correction; what pain levels may be expected; and any adverse effects associated with the use of intermittent intrapleural analgesia at our centre. Methods: A subset of the most recent 80 patients from a large single centre consecutive series of 201 patients (April 2000 to present) who had undergone TASF had their medical records reviewed. 32 patients met the inclusion criteria for the analysis (i.e. pain scores must have been recorded within the hour prior and within two hours following an intrapleural bolus being given). All patients received an intrapleural catheter inserted during surgery, in addition to patient-controlled opiate analgesia and oral analgesia as required. After surgery, patients received a bolus of 0.25% bupivacaine every four hours via the intrapleural catheter. Visual analogue pain scale scores were recorded before and after the bolus of local anaesthetic and the quantity and time of day that any other analgesia was taken, were also recorded. Results and Discussion: 28 female and four male patients (mean age 14.5 ± 1.5 years) had a total of 230 boluses of local anaesthetic administered intrapleurally, directly onto the spine, in the 96 hour period following surgery. Pain scores significantly decreased following the administration of a bolus (p<0.0001), with the mean pain score decreasing from 3.66 to 1.83. The quantity of opiates via patient-controlled analgesia after surgery decreased steadily between successive 24 hours intervals after an initial increase in the second 24 hour period when patients were mobilised. One intrapleural catheter required early removal at 26 hours postop due to leakage; there were no other associated complications with the intermittent intrapleural analgesia method. Post-operative pain following anterior scoliosis correction was decreased significantly with the administration of regular local anaesthetic boluses and can be reduced to ‘mild’ levels by combined analgesia regimes. The intermittent intrapleural analgesia method was not associated with any adverse events or complications in the full cohort of 201 patients.

Segmental torso masses and gravity-induced coronal plane joint moments in adolescent idiopathic scoliosis

Introduction: Calculating segmental (vertebral level-by-level) torso masses in Adolescent Idiopathic Scoliosis (AIS) patients allows the gravitational loading on the scoliotic spine during relaxed standing to be estimated. This study used supine CT scans of AIS patients to measure segmental torso masses and explored the joint moments in the coronal plane, particularly at the apex of a scoliotic major curve. Methods: Existing low dose CT data from the Paediatric Spine Research Group was used to calculate vertebral level-by-level torso masses and joint moments occurring in the spine for a group of 20 female AIS patients with right sided thoracic curves. The mean age was 15.0 ± 2.7 years and all curves were classified Lenke Type 1 with a mean Cobb angle 52 ± 5.9°. Image processing software, ImageJ (v1.45 NIH USA) was used to create reformatted coronal plane images, reconstruct vertebral level-by-level torso segments and subsequently measure the torso volume corresponding to each vertebral level. Segment mass was then determined by assuming a tissue density of 1.04x103 kg/m3. Body segment masses for the head, neck and arms were taken from published anthropometric data (Winter 2009). Intervertebral joint moments in the coronal plane at each vertebral level were found from the position of the centroid of the segment masses relative to the joint centres with the segmental body mass data. Results and Discussion: The magnitude of the torso masses from T1-L5 increased inferiorly, with a 150% increase in mean segmental torso mass from 0.6kg at T1 to 1.5kg at L5. The magnitudes of the calculated coronal plane joint moments during relaxed standing were typically 5-7 Nm at the apex of the curve, with the highest apex joint torque of 7Nm. The CT scans were performed in the supine position and curve magnitudes are known to be 7-10° smaller than those measured in standing, due to the absence of gravity acting on the spine. Hence, it can be expected that the moments produced by gravity in the standing individual will be greater than those calculated here.

A biomechanical analysis of anterior instrumentation used in the surgical correction of adolescent idiopathic scoliosis

Scoliosis is a deformity of the spine which affects children and adolescents, and remains a challenge to treat. This study measured the forces used during surgery to correct scoliosis and studied changes to spinal mechanics from the implantation of metal rods used to hold the spine straight. The results of this study will help surgeons and engineers understand how to straighten the spine more efficiently to provide patients with better outcomes.

A biomechanical analysis of growing rods used in the management of early onset scoliosis (EOS)

The use of dual growing rods is a fusionless surgical approach to the treatment of early onset scoliosis (EOS) which aims to harness potential growth in order to correct spinal deformity. This study compared through in-vitro experiments the biomechanical response of two different rod designs under axial rotation loading. The study showed that a new design of telescoping growing rod preserved the rotational flexibility of the spine in comparison with rigid rods indicating them to be a more physiological way to improve the spinal deformity.

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 are 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 trunk in Adolescent Idiopathic Scoliosis patients. Methods Existing low-dose Computed Tomography 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 Computed Tomography 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 0.6kg at T1 to 1.5kg at L5. Similarly, the segmental thickness corresponding to each vertebral level 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.

Supine to standing Cobb Angle change in idiopathic scoliosis: The effect of endplate preselection

Introduction Standing radiographs are the ‘gold standard’ for clinical assessment of adolescent idiopathic scoliosis (AIS), with the Cobb Angle used to measure the severity and progression of the scoliotic curve. Supine imaging modalities can provide valuable 3D information on scoliotic anatomy, however, due to changes in gravitational loading direction, the geometry of the spine alters between the supine and standing position which in turn affects the Cobb Angle measurement. Previous studies have consistently reported a 7-10° [1-3] Cobb Angle increase from supine to standing, however, none have reported the effect of endplate pre-selection and which (if any) curve parameters affect the supine to standing Cobb Angle difference. Methods Female AIS patients with right-sided thoracic major curves were included in the retrospective study. Clinically measured Cobb Angles from existing standing coronal radiographs and fulcrum bending radiographs [4] were compared to existing low-dose supine CT scans taken within 3 months of the reference radiograph. Reformatted coronal CT images were used to measure Cobb Angle variability with and without endplate pre-selection (end-plates selected on the radiographs used on the CT images). Inter and intra-observer measurement variability was assessed. Multi-linear regression was used to investigate whether there was a relationship between supine to standing Cobb Angle change and patient characteristics (SPSS, v.21, IBM, USA). Results Fifty-two patients were included, with mean age of 14.6 (SD 1.8) years; all curves were Lenke Type 1 with mean Cobb Angle on supine CT of 42° (SD 6.4°) and 52° (SD 6.7°) on standing radiographs. The mean fulcrum bending Cobb Angle for the group was 22.6° (SD 7.5°). The 10° increase from supine to standing is consistent with existing literature. Pre-selecting vertebral endplates was found to increase the Cobb Angle difference by a mean 2° (range 0-9°). Multi-linear regression revealed a statistically significant relationship between supine to standing Cobb Angle change with: fulcrum flexibility (p=0.001), age (p=0.027) and standing Cobb Angle (p<0.001). In patients with high fulcrum flexibility scores, the supine to standing Cobb Angle change was as great as 20°.The 95% confidence intervals for intra-observer and inter-observer measurement variability were 3.1° and 3.6°, respectively. Conclusion There is a statistically significant relationship between supine to standing Cobb Angle change and fulcrum flexibility. Therefore, this difference can be considered a measure of spinal flexibility. Pre-selecting vertebral endplates causes only minor changes.

A biomechanical analysis of growing rods used in the management of early onset scoliosis

INTRODUCTION Managing spinal deformities in young children is challenging, particularly early onset scoliosis (EOS). Surgical intervention is often required if EOS has been unresponsive to conservative treatment particularly with rapidly progressive curves. An emerging treatment option for EOS is fusionless scoliosis surgery. Similar to bracing, this surgical option potentially harnesses growth, motion and function of the spine along with correcting spinal deformity. Dual growing rods are one such fusionless treatment, which aims to modulate growth of the vertebrae. The aim of this study was to ascertain the extent to which semiconstrained growing rods (Medtronic, Sofamor, Danek, Memphis, TN) with a telescopic sleeve component, reduce rotational constraint on the spine compared with standard "constrained / rigid" rods and hence potentially provide a more physiological mechanical environment for the growing spine. METHODS Six 40-60kg English Large White porcine spines served as a model for the paediatric human spine. Each spine was dissected into a 7 level thoracolumbar multi-segment unit (MSU), removing all non-ligamentous soft tissues and leaving 3cm of ribs either side. Pure nondestructive axial rotation moments of ±4Nm at a constant rotation rate of 8deg.s-1 were applied to the mounted MSU spines using a biaxial Instron testing machine. Displacement of each vertebral level was captured using a 3D motion tracking system (Optotrak 3020, Northern Digital Inc, Waterloo, ON). Each spine was tested in an un-instrumented state first and then with appropriately sized semi-constrained growing rods and rigid rods in alternating sequence. The rods were secured by multi-axial pedicle screws (Medtronic CD Horizon) at levels 2 and 6 of the construct. The range of motion (ROM), neutral zone (NZ) size and stiffness (Nm.deg-1) were calculated from the Instron load-displacement data and intervertebral ROM was calculated through a MATLAB algorithm from Optotrak data. RESULTS Irrespective of the order of testing, rigid rods significantly reduced the total ROM compared with semi-constrained rods (p<0.05) with in a significantly stiffer spine for both left and right axial rotation (p<0.05). Analysing the intervertebral motion within the instrumented levels 2-6, rigid rods showed reduced ROM compared with semi-constrained growing rods and compared with un-instrumented motion segments. CONCLUSION Semi-constrained growing rods maintain similar stiffness in axial rotation to un-instrumented spines, while dual rigid rods significantly reduce axial rotation. Clinically the effect of semi-constrained growing rods as observed in this study is that they would be expected to allow growth via the telescopic rod components while maintaining the axial flexibility of the spine, which may reduce occurrence of the crankshaft phenomenon.

Thoracoscopic scoliosis surgery – a cheaper option? A cost analysis of 189 consecutive cases

INTRODUCTION: Increasing health care costs, limited resources and increased demand makes cost effective and cost-efficient delivery of Adolescent Idiopathic Scoliosis (AIS) management paramount. Rising implant costs in deformity correction surgery have prompted analysis of whether high implant densities are justified. The objective of this study was to analyse the costs of thoracoscopic scoliosis surgery, comparing initial learning curve costs with those of the established technique and to the costs involved in posterior instrumented fusion from the literature. METHODS: 189 consecutive cases from April 2000 to July 2011 were assessed with a minimum of 2 years follow-up. Information was gathered from a prospective database covering perioperative factors, clinical and radiological outcomes, complications and patient reported outcomes. The patients were divided into three groups to allow comparison; 1. A learning curve cohort, 2. An intermediate cohort and 3. A third cohort of patients, using our established technique. Hospital finance records and implant manufacturer figures were corrected to 2013 costs. A literature review of AIS management costs and implant density in similar curve types was performed. RESULTS: The mean pre-op Cobb angle was 53°(95%CI 0.4) and was corrected postop to mean 22.9°(CI 0.4). The overall complication rate was 20.6%, primarily in the first cohort, with a rate of 5.6% in the third cohort. The average total costs were $46,732, operating room costs of $10,301 (22.0%) and ICU costs of $4620 (9.8%). The mean number of screws placed was 7.1 (CI 0.04) with a single rod used for each case giving average implant costs of $14,004 (29.9%). Comparison of the three groups revealed higher implant costs as the technique evolved to that in use today, from $13,049 in Group 1 to $14577 in Group 3 (P<0.001). Conversely operating room costs reduced from $10,621 in Group 1 to $7573 (P<0.001) in Group 3. ICU stay was reduced from an average of 1.2 to 0 days. In-patient stay was significantly (P=0.006) lower in Groups 2 and 3 (5.4 days) than Group 1 (5.9 days) (i.e. a reduction in cost of approximately $6,140). CONCLUSIONS: The evolution of our thoracoscopic anterior scoliosis correction has resulted in an increase in the number of levels fused and reduction in complication rate. Implant costs have risen as a result, however, there has been a concurrent decrease in those costs generated by operating room use, ICU and in-patient stay with increasing experience. Literature review of equivalent curve types treated posteriorly shows similar perioperative factors but higher implant density, 69-83% compared to the 50% in this study. Thoracoscopic Scoliosis surgery presents a low density, reliable, efficient and effective option for selected curves. A cost analysis of Thoracoscopic Scoliosis Surgery using financial records and a prospectively collected database of all patients since 2000, demonstrating a clear cost advantage compared to equivalent posterior instrumentation and fusion.

A biomechanical analysis of growing rods used in the management of early onset scoliosis

INTRODUCTION Managing spinal deformities in young children is challenging, particularly early-onset scoliosis (EOS). Any progressive spinal deformity particularly in early life presents significant health risks for the child and a challenge for the treating surgeon. Surgical intervention is often required if EOS has been unresponsive to conservative treatment particularly with rapidly progressive curves. An emerging treatment option particularly for EOS is fusionless scoliosis surgery. Similar to bracing this surgical option potentially harnesses growth, motion and function of the spine along with correcting spinal deformity. Dual growing rods is one such fusionless treatment, which aims to modulate growth of the vertebrae. The aim of this study was to ascertain the extent to which semi-constrained growing rods (Medtronic, Memphis, TN) with a telescopic sleeve component, reduce rotational constraint on the spine compared with standard rigid rods and hence potentially provide a more physiological mechanical environment for the growing spine. METHODS Six 40-60kg English Large White porcine spines served as a model for the paediatric human spine. Each spine was dissected into 7 level thoracolumbar multi-segment unit (MSU) spines, removing all non-ligamentous soft tissues. Appropriately sized semi-constrained growing rods and rigid rods were secured by multi-axial screws (Medtronic) prior to testing in alternating sequences for each spine. Pure nondestructive moments of +/4Nm at a constant rotation rate of 8deg/s was applied to the mounted MSU spines. Displacement of each level was captured using an Optotrak (Northern Digital Inc, Waterloo, ON). The range of motion (ROM), neutral zone (NZ) size and stiffness (Nm/deg) were calculated from the Instron load-displacement data and intervertebral ROM was calculated through a MATLAB algorithm from Optotrak data. RESULTS Irrespective of sequence order rigid rods significantly reduced the total ROM (deg) than compared to semi-constrained rods (p<0.05) and resulted in a significantly stiffer (Nm/deg) spine for both left and right axial rotation testing (p<0.05). Analysing the intervertebral motion within the instrumented levels, rigid rods showed reduced ROM (Deg) than compared to semi-constrained growing rods and the un-instrumented (UN-IN) test sequences. CONCLUSION The semi-constrained growing rods maintained rotation similar to UN-IN spines while the rigid rods showed significantly reduced axial rotation across all instrumented levels. Clinically the effect of semi-constrained growing rods evaluated in this study is that they will allow growth via the telescopic rod components while maintaining the axial rotation ability of the spine, which may also reduce the occurrence of the crankshaft phenomenon.

Supine to standing Cobb angle change in idiopathic scoliosis : the effect of endplate pre-selection

Background Supine imaging modalities provide valuable 3D information on scoliotic anatomy, but the altered spine geometry between the supine and standing positions affects the Cobb angle measurement. Previous studies report a mean 7°-10° Cobb angle increase from supine to standing, but none have reported the effect of endplate pre-selection or whether other parameters affect this Cobb angle difference. Methods Cobb angles from existing coronal radiographs were compared to those on existing low-dose CT scans taken within three months of the reference radiograph for a group of females with adolescent idiopathic scoliosis. Reformatted coronal CT images were used to measure supine Cobb angles with and without endplate pre-selection (end-plates selected from the radiographs) by two observers on three separate occasions. Inter and intra-observer measurement variability were assessed. Multi-linear regression was used to investigate whether there was a relationship between supine to standing Cobb angle change and eight variables: patient age, mass, standing Cobb angle, Risser sign, ligament laxity, Lenke type, fulcrum flexibility and time delay between radiograph and CT scan. Results Fifty-two patients with right thoracic Lenke Type 1 curves and mean age 14.6 years (SD 1.8) were included. The mean Cobb angle on standing radiographs was 51.9° (SD 6.7). The mean Cobb angle on supine CT images without pre-selection of endplates was 41.1° (SD 6.4). The mean Cobb angle on supine CT images with endplate pre-selection was 40.5° (SD 6.6). Pre-selecting vertebral endplates increased the mean Cobb change by 0.6° (SD 2.3, range −9° to 6°). When free to do so, observers chose different levels for the end vertebrae in 39% of cases. Multi-linear regression revealed a statistically significant relationship between supine to standing Cobb change and fulcrum flexibility (p = 0.001), age (p = 0.027) and standing Cobb angle (p < 0.001). The 95% confidence intervals for intra-observer and inter-observer measurement variability were 3.1° and 3.6°, respectively. Conclusions Pre-selecting vertebral endplates causes minor changes to the mean supine to standing Cobb change. There is a statistically significant relationship between supine to standing Cobb change and fulcrum flexibility such that this difference can be considered a potential alternative measure of spinal flexibility.

The effect of endplate preselection when measuring supine versus standing cobb angle change in idiopathic scoliosis

The primary aim of this study was to determine whether endplate pre-selection makes a difference to the Cobb Angle change between supine and standing which is known to occur in idiopathic scoliosis. A secondary aim of this study was to identify which (if any) patient characteristics were correlated with supine versus standing Cobb change. The study found that pre-selecting vertebral endplates causes only has a minor effect on supine to standing Cobb change in scoliosis. There is a statistically significant relationship between supine to standing Cobb Angle change and fulcrum flexibility. Therefore, supine to standing Cobb Angle change can be considered as a measure of spinal flexibility when both standing and supine images are clinically available.

Growing rod analysis for the fusionless correction of early onset scoliosis (EOS)

Managing spinal deformities in young children is challenging, particularly early onset scoliosis (EOS). Surgical intervention is often required if EOS has been unresponsive to conservative treatment particularly with rapidly progressive curves. An emerging treatment option for EOS is fusionless scoliosis surgery. Similar to bracing, this surgical option potentially harnesses growth, motion and function of the spine along with correcting spinal deformity. Dual growing rods are one such fusionless treatment, which aims to modulate growth of the vertebrae. The aim of this study was to ascertain the extent to which semi-constrained growing rods (Medtronic Sofamor Danek Memphis, TN, USA) with a telescopic sleeve component, reduce rotational constraint on the spine compared with standard rigid rods and hence potentially provide a more physiological mechanical environment for the growing spine. This study found that semi-constrained growing rods would be expected to allow growth via the telescopic rod components while maintaining the axial flexibility of the spine and the improved capacity for final correction.