In healthy subjects, respiratory maximal volumes are highly dependent on the sagittal range of motion of the T7-T10 segment. In AIS, the abolition of T7-T10 dynamics related to the stiffness induced by the apex region in Lenke IA curves could harm ventilation during maximal breathing. The aim of this study was to analyze the dynamics of the thoracic spine during deep breathing in AIS patients and in healthy matched controls. This is a cross-sectional, case-control study. 20 AIS patients (18 girls, Cobb angle, 54.7±7.9°; Risser 1.35±1.2) and 15 healthy volunteers (11 girls) matched in age (12.5 versus 15.8 yr. mean age) were included. In AIS curves, the apex was located at T8 (14) and T9 (6). Conventional sagittal radiographs of the whole spine were performed at maximal inspiration and exhalation. The ROM of each spinal thoracic functional segment (T1-T7, T7-T10, T10-T12) and the global T1-T12 ROM were measured. In healthy subjects, the mean T1-T12 ROM during forced breathing was 16.7±3.8. AIS patients showed a T1-T12 ROM of 1.1±1.5 (p<0.05), indicating a sagittal stiffness of the thoracic spine. A wide T7-T10 ROM (15.3±3.0) was found in healthy controls (91.6% of the T1–T12 ROM). AIS patients showed only 0.4±1.4 ROM at T7-T10 (36.4% of the T1-T12 ROM) (p<0.001). There was a significant positive correlation between the magnitude of T7-T10 kyphosis in maximal exhalation and both FVC (% of predicted FVC) and FEV1. In conclusion, Lenke 1A AIS patients show a restriction of the thoracic spine motion with an almost complete abolition of T7-T10 ROM, a crucial segment for deep breathing. T7-T10 stiffness could explain the ventilatory limitations found in AIS patients.

The aim of this study was to report the restauration of the normal vertebral morphology and the absence of curve progression after removal the instrumentation in AIS patients that underwent posterior correction of the deformity by common all screws construct whitout fusion. A series of 36 AIS immature patients (Risser 3 or less) were include in the study. Instrumentation was removed once the maturity stage was complete (Risser 5). Curve correction was assessed at pre and postoperative, before instrumentation removal, just post removal, and more than two years after instrumentation removal. Epiphyseal vertebral growth modulation was assessed by a coronal wedging ratio (WR) at the apical level of the main curve (MC). The mean preoperative coronal Cobb was corrected from 53.7°±7.5 to 5.5º±7.5º (89.7%) at the immediate postop. After implants removal (31.0±5.8 months) the MC was 13.1º. T5–T12 kyphosis showed a significant improvement from 19.0º before curve correction to 27.1º after implants removal (p<0.05). Before surgery, WR was 0.71±0.06, and after removal WR was 0.98±0.08 (p<0.001). At the end of follow-up, the mean sagittal range of motion (ROM) of the T12-S1 segment was 51.2±21.0º. SRS-22 scores improved from 3.31±0.25 preoperatively to 3.68±0.25 at final assessment (p<0.001). In conclusion, fusionless posterior approach using a common all pedicle screws construct correct satisfactory scoliotic main curves and permits removal of the instrumentation once the bone maturity is reached. The final correction was highly satisfactory and an acceptable ROM of the previously lower instrumented segments was observed.

To analyze the dynamics of the thoracic spine during deep breathing in AIS patients and in healthy matched controls.

Case-control cross-sectional study. 20 AIS patients (18 girls, Cobb angle, 54.7±7.9°; Risser 1.35±1.2) and 15 healthy volunteers (11 girls) matched in age (12.5 versus 15.8 yr. mean age) were included. In AIS curves, the apex was located in T8 (14) and T9 (6). Conventional sagittal radiographs of the whole spine were performed at maximal inspiration and expiration. The ROM of each spinal thoracic functional segment (T1-T7, T7-T10, T10-T12), the global T1–T12 ROM were measured. Respiratory function was assess by forced vital capacity (FVC), expiratory volume (FEV1), FEV1/FVC, inspiratory vital capacity (IVC) and peak expiratory flow (PEF).

In healthy subjects, the mean T1–T12 ROM during forced breathing was 16.7±3.8. AIS patients showed a T1-T12 ROM of 1.1±1.5 (p<0.05) indicating a sagittal stiffness of thoracic spine. A wide T7–T10 ROM (15.3±3.0) was found in healthy controls (91.6% of the T1–T12 ROM). AIS patients showed only 0.4±1.4 ROM at T7-T10 (36.4% of the T1–T12 ROM) (p<0.001). There was a significant correlation between T7-T10 ROM and IVC.

Lenke 1A AIS patients show a restriction of the thoracic spine motion with an almost complete abolition of T7-T10 ROM, a crucial segment participating in the deep breathing. T7-T10 stiffness could explain the ventilatory limitations found in AIS patients.

Background

Using flexible tethering techniques, porcine models of scoliosis have been previously described. These scoliotic curves showed vertebral wedging but very limited axial rotation. In some of these techniques, a persistent scoliotic deformity was found after tether release. The possibility to create severe progressive true scoliosis in a big animal model would be very useful for research purposes, including corrective therapies.

Background

Oblique implantable total disc replacements (TDR) have been developed in an attempt to partially resect the anterior longitudinal ligament (ALL), together with additional partial resection of lateral annulus fibres. To date, the literature has not addressed the impact of the TDR oblique implantation on the lumbar spine sagittal alignment. The hypothesis of this study was that TDR at the L4-L5 level does not change the sagittal alignment and the range of motion of the lumbar spine when the implant is placed in accurate position.

Background

The improvement of the rib cage deformity (RCD) after surgery correction has not been correlated in detail with the correction of vertebral axial rotation (AR). The loss of at the rib cage after correction has been never monitored. The hypothesis of this work was that the aesthetic improvement of RCD in adolescent idiopathic scoliosis (AIS) does not follow completely the reduction of thoracic AR after correction surgery. Moreover, lesser correction of thorax deformity could be expected in mature patients with more rigid curves.

Background

After surgical correction of thoracic scoliosis, an improvement in the cardio-respiratory adaptation to exercise would be expected because of the correction of the rib cage associated with the spinal deformity. This work intended to evaluate the physiologic responses to incremental exercise in patients undergoing surgical correction of adolescent idiopathic scoliosis (AIS). The hypothesis of this study was that the exercise limitations described in patients with AIS could be related with the physical deconditioning instead of being linked to the severity of the vertebral deformity.

Summary Statement

The spinal cord showed marked sensibility to acute compression causing complete and irreversible injury. On the contrary, the spinal cord has more ability for adaptation to slow progressive compression mechanisms having the possibility of neural recovery after compression release.

Summary Statement

Patients with adolescent idiopathic scoliosis show clear signs of abnormal motor coordination between the long superficial paraspinal muscles and the deep rotators. These findings suggest an abnormal behavior of the deep rotator muscles at the concave side.

Introduction

A new triggered electromyography test for detection of stimulus diffusion to intercostal muscles of the contralateral side during thoracic pedicle screw placement was evaluated. Experimental research was carried out in order to determine if, using this test, neural contact at different aspects of the spinal cord and nerve roots could be discriminated.

Objectives

To determine the limits of spinal displacement before the onset of neurophysiological changes during spinal surgery. Assessing if the type of force applied or the section of the adjacent nerve roots increases the tolerance to displacement.

Purpose of the study: Neurophysiological monitoring during pedicular screw insertion has been used to verity bone integrity of instrumented pedicles. The purpose of this study was to determine, experimentally, whether the EMG thresholds after stimulation of dorsal pedicular screws depend on the distance between the nerve structures and the screw, or on the interposition of different tissues.

Material and methods: EMG thresholds were recorded after stimulation of 18 VPD in fivde pigs, by varying the distance between the screws and the spinal cord (2, 6, 10 mm). The thresholds were recorded after rupture of the median pedicular cortical and after interposition of different tissues (blood, muscle, fat and bone) between the screws and the spinal cord. In four patients with a hemivertebra, four pedicular screws sere stimulated at insertion, just after resection of the hemivertebra.

Results: The average intensity of the EMG thresholds was 5.60±1.90mA when the screws were in contact with the dural sac. When the distance was 2 mm, the average threshold reached ±3.42 mA, at 6 mm 13.59±6.27 mA and at 10mm, 15.86±5.83 mA (p< 0.05). Rupture of the median pedicular cortical and interposition of different biological tissues in experimental animals did not modify the stimulation thresholds of the dorsal pedicle screws. In the four operated patients with resection of a hemivertebra, the EMG stimulation thresholds exhibited a wide spread but did not provide any evidence for a significant change related to interposition of different tissues. The impedance of the bone material was higher than muscle or adipose tissue. In these patients, the distance from the screw to the spinal cord was not correlated with a modification in the stimulation threshold.

Discussion: Further clinical study is needed to better understand the stimulation role of the EMG in the implantation of pedicular screws, considering that this technique does not determine pedicle rupture.

Conclusion: In experimental animals, the electrical impedance appears to depend on the distance between the screw and the nerve structures but not on the integrity of the median pedicular cortical. Response to intensity does not appear to be related to the type of interpositioned tissue.

This work was aimed at study the role of paraspinal muscles on spinal tensegrity. Four different models of spinal tensegrity breakage with and without injury of the posterior spinal muscle were investigated.

Fifteen minipigs (mean age 6-week) underwent costotransversectomy (CTT) at 5 consecutive vertebral segments. In 4 animals ribs and transverse processes (T7–T11) were removed through a posterior midline approach with complete desinsertion of paraspinal muscles. In other 3 animals, CTT was performed by a posterolateral approach (T6–T10) without detachment of paraspinal muscles. Other 4 minipigs underwent rib resection (T7-T11) throughout a thoracoscopic approach avoiding damage of posterior spinal muscles. A final group of 4 animals, a complete detachment of the paraspinal muscles was performed from T7 to T11 without removing bony structures and leaving in deep surgical wax attached to the spinous and transverse processes to avoid reinsertion of the muscles after surgery. Anatomic specimens were radiologically and macroscopically studied just at sacrifice 5 months after surgery

All 4 animals operated on of CTT by midline posterior approach developed structural spinal deformity with curve convexity at the side of rib removal (mean Cobb angle 34,6°). Animals undergoing CTT by posterolateral approach without paraspinal muscle detachment did not develop any significant spinal deformity. Absence of spinal deformity was also found in those animals in which rib resection was performed by thoracoscopy without injury of the posterior spinal muscles. All 4 animals undergoing detachment of the paraspinal muscles without CTT and application of the surgical wax developed scoliotic curves (mean Cobb angle of 28°).

In conclusion, a new insight on the underlying pathogenic mechanisms of scoliotic curves is given by using this spinal tensegrity model. Isolated damage of the posterior muscle-ligamentous structures around the costotransverse joints breaking muscles spine tensegrity seems to be mandatory to induce scoliotic deformity. Rib removal alone appeared to have less scoliotic inductive implication. The finding questions previous knowledge on scoliosis etiopathogeny.

Purpose of the study: Fixing the pedicles can be difficult to achieve during surgical treatment of scoliosis involving the thoracic spine because of the vertebral rotation raising the risk of neurological and vascular disorders. Use of extrapedicular thoracic screws has been proposed for more adapted and safe fixation. No clinical data has been published concerning the safety of these screws.

Material and methods: This multicentric retrospective clinical and radiological study included 467 thoracic screws in 34 patients operated for scoliosis. Neurophysiological monitoring was used for all procedures. Screws were positioned free hand without radioscopic control. Pedicular screws were inserted in T10, T11, T12. Extra-pedicular screws were inserted for thoracic vertebrae above T10 to T4. Correction was achieved with rods bent in situ. The purpose of this study was to evaluate the position of the thoracic screws within the vertebral body and in relation to the great vessels and the cord. The position of the screws in the thoracic spine was studied by two independent observers reading multiple thin-slice CT images. The observers noted malposition as: 1) penetration into the canal more than 2 mm, 2) less than 1 cm hold in the vertebral body, 3) screw protrusion more than 2 mm beyond the vertebral cortical.

Results: Screw malposition was observed for 9 of 161 pedicular screws (5.4%) and for 21 of 306 (6.8%) thoracic screws. None of the screw malpositions had a clinical expression. There was one episode of thoracic effusion associated with thoracoplasty. Two patients required revision (one for poor indication and one for disincarceration). There were no postoperative deep infections. Three cases of intercostals neuralgia subsided within three months.

Conclusion: Insertion of thoracic screws for fixation and correction is a useful technique with few complications. It enables better 3D correction and better control of the deformation. Screw malposition in this series was similar to that observed with classical pedicular techniques. There was no major complication associated with thoracic screws.

Introduction and purpose: We present the results of our surgical method involving nerve decompression, reduction and circumferential spinal fusion via posterior approach for severe spondylolisthesis.

Materials and methods: We studied 14 patients with spondylolisthesis and slippage greater than 50%; mean age 24. Mean slip angle 37° and mean preoperative slip 74%.

Procedure: Via a posterior approach we performed neural decompression and placed pedicle screws in L5-S1 (in one case we instrumented L4 for associated L4-L5 spondylolisthesis) and iliac screws (except in three cases). We removed the annulus fibrosus, the L5-S1 disc and the rounded proximal edge of the sacrum. Following distraction of L5-S1 we inserted bone graft cages (from 3 to 5). We adjusted the bars with spanners to reduce slippage and achieve final curvature of the spine.

The cases were monitored with evoked potentials and epidural catheter.

We studied preoperative, postoperative and final check X-rays. The clinical histories were also reviewed.

Results: One rupture of the dura. Two patients with anterior slippage of a cage. One posterior slippage of L5 screws, without revision surgery. One postoperative infection resolved by surgical cleaning and antibiotic therapy.

After mean follow-up of 32 months the radiographic study showed no pseudoarthrosis. Final mean slippage was 15% and slip angle 5°. Ten patients had no pain or physical limitations. Two presented mild lumbar discomfort and occasional limitation.

Conclusions: The procedure we used was shown to be effective in correcting the deformity with excellent clinical results.

Introduction and purpose: The relationship between congenital heart disease and the increased prevalence of scoliosis is well known, although the same cannot be said about the etiology of scoliosis in these patients. Although thoracotomy is often associated to scoliosis, median sternotomy has so far not been identified as an etiological agent. he purpose of the study is to determine if patients with congenital heart disease who are subjected to a median sternotomy show a higher prevalence of spine deformities.

Materials and methods: A retrospective review is made of patients operated on for congenital heart disease through median sternotomy before the age of 8, assessing the development of spine deformities. Simple chest radiographs of 128 patients were studied once they reached skeletal maturity and it was observed that they presented no spinal or costal deformities before surgery.

Results: The prevalence of scoliosis was 34.3%; 16 of these patients (12.5%) had curves of more than 20° and 33 (25.8%) had thoracic kyphosis of less than 20°. Patients operated on before the age of 18 months had a significantly higher risk to develop scoliosis as compared with those treated later (odds ratio: 3.48; p=0.016). The development of scoliosis was not related with the type of cardiac malformation present.

Conclusions: There is a high prevalence of scoliosis in patients subjected to a median sternotomy for a congenital heart pathology. The prevalence of scoliosis increases in patients operated on at younger ages.