Is expansion thoracoplasty a safe procedure for mobility and growth potential of the spine? Spontaneous fusion after multiple chest distractions in young children

Autofusion in growing rod surgery for early onset scoliosis; what do we know so far?

The evolving landscape of early onset scoliosis management has shifted from the traditional paradigm of early definitive spinal fusion towards modern growth-friendly implants, particularly Growing Rods (GR). Despite the initial classification of GR treatment as a fusionless procedure, the phenomenon of autofusion has emerged as a critical consideration in understanding its outcomes. Studies have demonstrated the presence of autofusion since the early 1980s. The consequences of autofusion are extensive, impacting curve correction, diminishing trunk growth rate, and contributing to the "law of diminishing returns" in growing rod surgery. The literature suggests that autofusion may complicate definitive fusion surgery, leading to prolonged and intricate procedures involving multiple osteotomies. Additionally, it poses challenges in identifying anatomical landmarks during surgery, potentially increasing the risk of complications and revisions. While autofusion poses challenges to achieving optimal outcomes in growing rod treatment, it cannot be considered a standalone replacement for definitive fusion. Recent advances aim to limit autofusion and enhance treatment outcomes. In this review, we will delve into the existing literature on autofusion, examining studies that have documented its presence, probable causes, pathophysiology, potential implications for long-term patient outcomes, and possible new implants and techniques that decrease its incidence.

Does vertebral body tethering cause disc and facet joint degeneration? A preliminary MRI study with minimum two years follow-up

BACKGROUND CONTEXT

Vertebral body tethering (VBT), a flexible compression-based growth modulation technique, was claimed to prevent disc degeneration due to its less rigid nature compared to other growth-friendly techniques. Yet, the consequences of VBT surgery on discs and facet joints have not been precisely acknowledged.

PURPOSE

The purpose of this study was to determine the changes in the intermediate and adjacent levels at least 2 years after surgery.

STUDY DESIGN/SETTING

Prospectively-followed consecutive patient cohort PATIENT SAMPLE: Adolescent idiopathic scoliosis patients who underwent thoracoscopic VBT between 2014 and 2017 were included.

OUTCOME MEASURES

Degeneration of the intervertebral discs using the Pfirrmann classification; Degeneration of facet joints using a scale of 0 to 3.

METHODS

Demographic, perioperative, clinical, radiographic data were collected. Skeletal maturity and height gain were assessed in every follow-up. Overcorrection, tether breakage, mechanical and pulmonary complications as well as readmission and reoperations were recorded. MRIs taken before surgery and at a minimum of 2 years follow-up were evaluated for degeneration at the intermediate and adjacent segment intervertebral discs and facet joints by a blinded senior radiologist and compared.

RESULTS

Twenty-five patients with a mean of 38.6±10.6 months (24-62) of follow-up were included. The mean age at surgery was 12.2 (10-14), and the median Sanders stage was 3 (1-7). A mean of 7.7±1.1 (6-11) levels were tethered. The mean preoperative main thoracic curve magnitude of 46°±7.7° was corrected to 23.3°±5.9° postoperatively, which was subsequently modulated to 12° ±11.5° during the follow-up. At the time of the MRI (mean 29±9.5 (24-62) months), the median Sanders stages was 7 (5-8). A total of 217 levels of discs and bilateral facet joints were evaluated in the preoperative and follow-up MRI images. Analyses of disc and facet scores revealed no significant differences between patients. Deterioration of previously degenerated discs was noted in one patient (from grade 2 to 3), while previously healthy lower adjacent facet joints were degenerated (grade 2) in another patient.

CONCLUSIONS

Intermediate discs and facet joints were preserved after growth modulation with VBT surgery at a mean of 29 months of follow-up. Studies in larger cohorts with longer follow-up are warranted to have more in-depth analyses of the effects of relative stabilization and altered biomechanical loads.

Nonsurgical Management of Early-onset Scoliosis

Early-onset scoliosis is potentially fatal if left untreated. Although surgical management with growing instrumentation may be necessary, this is not a panacea and is associated with high complication rates. Recent evidence has demonstrated that nonsurgical treatment can be an effective early management strategy in delaying or even precluding the need for surgery, especially surgery with growing instrumentation. The goal of both nonsurgical and surgical management is to control or correct the spinal curve to allow appropriate pulmonary development while delaying definitive fusion until an appropriate skeletal age. Although more commonly used to delay surgery, serial cast correction using the Cotrel and Morel elongation-derotation-flexion technique may result in complete correction in patients with infantile idiopathic scoliosis and smaller curve magnitudes.

Recent advances in the management of early onset scoliosis

As the undesired results of early spinal fusion have become apparent, "growth-friendly" management methods for early onset scoliosis have been increasing during recent years. Current literature supports the use of repeated corrective cast applications as the initial management for most early onset progressive spinal deformities as either definitive treatment or as a temporizing measure. If casting is not an option or the deformity cannot be controlled via casting, one of the growth-friendly instrumentation techniques is chosen. Growth-friendly surgical methods and implants have been evolving as understanding of the disease improves.

Pulmonary and Radiographic Outcomes of VEPTR (Vertical Expandable Prosthetic Titanium Rib) Treatment in Early-Onset Scoliosis

BACKGROUND

VEPTR (vertical expandable prosthetic titanium rib) expansion thoracoplasty is used to manage thoracic insufficiency syndrome in early-onset scoliosis. Literature regarding the effects of this technique on pulmonary function is scarce. The aim of this study was to report the intermediate-term results of VEPTR expansion thoracoplasty.

METHODS

Twenty-one children with thoracic insufficiency syndrome underwent VEPTR expansion thoracoplasty from 2002 to 2012 and had complete chart data, preoperative and follow-up radiographs, and pulmonary function tests performed at the index implantation, first expansion, and last expansion. Pulmonary function tests with forced and passive deflation techniques developed for children under general anesthesia were performed prior to the index implantation and each expansion surgery under the same anesthetic conditions. Pulmonary and radiographic parameters were analyzed longitudinally.

RESULTS

Mean follow-up was six years, and mean age at implantation was 4.8 years. The mean number of expansion procedures per patient was eleven, and the mean number of pulmonary function tests was ten. The mean interval between surgical procedures was 6.4 months. Mean forced vital capacity (FVC) increased from 0.65 to 0.96 L (p < 0.0001). However, the percentage of the predicted FVC decreased from 77% to 58%. Respiratory system compliance normalized on the basis of body weight, Crs/kg, decreased by 39%, from 1.4 to 0.86 mL/cm H₂O/kg. The mean Cobb angle before treatment was 80°, and the mean maximum thoracic kyphosis angle was 57° (range, 7° to 107°). The initial coronal correction was maintained at the time of final follow-up (67°); however, there was a trend toward a decrease in the maximum thoracic kyphosis angle (to 66°, p = 0.08). Clinically apparent proximal thoracic kyphosis occurred in four patients, and spinal imbalance occurred in seven. The mean gain in T1-T12 height during the treatment period was 18 mm (2.9 mm/year).

CONCLUSIONS

FVC improved over time; however, this increase in lung volume did not keep up with the growth of the child, as the percentage of the predicted FVC decreased, and the chest wall stiffness increased. Coronal correction was maintained, but the increase in proximal thoracic kyphosis is concerning.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

2014 Update on the 'growing spine surgery' for young children with scoliosis

PURPOSE OF REVIEW

Spinal fusion procedures that are the mainstay of the treatment of progressive or severe curves in adolescents and adults are not suitable for most young children as there is a large magnitude of remaining growth. Early spinal fusion stunts the growth of the thorax and may interfere with the development of the lungs. Therefore, in children with early-onset scoliosis, 'growth friendly' instrumentation systems have been utilized to control the deformity while allowing the growth of the spine and the thoracic cage.

RECENT FINDINGS

The experience with growing rods has been increasing, along with expanding indications. Several self-lengthening instrumentation systems have been introduced aiming for guided spinal growth. There has been considerable progress in the clinical and laboratory studies using magnetically controlled growing rod constructs. Growing rods and vertical expandable prosthetic titanium rib (VEPTR) systems provide deformity control while allowing for spinal growth along with a risk of spontaneous vertebral fusions. VEPTR may cause rib fusions as the implants overlie the thoracic cage and, therefore, the use in pure spinal deformities is controversial.

SUMMARY

There have been exciting recent advances concerning the treatment of spinal deformities in young children. Despite these advances, the surgical treatment of early-onset scoliosis remains far from optimal and more development is on the way.

Metabolic Effects of Angulation, Compression, and Reduced Mobility on Annulus Fibrosis in a Model of Altered Mechanical Environment in Scoliosis

STUDY DESIGN

Comparison of disc tissue from rat tails in 6 groups with different mechanical conditions imposed.

OBJECTIVES

To identify disc annulus changes associated with the supposed altered biomechanical environment in a spine with scoliosis deformity using an immature rat model that produces disc narrowing and wedging.

BACKGROUND

Intervertebral discs become wedged and narrowed in a scoliosis curve, probably partly because of an altered biomechanical environment.

METHODS

We subjected tail discs of 5-week-old immature Sprague-Dawley rats to an altered mechanical environment using an external apparatus applying permutations of loading and deformity for 5 weeks. Together with a sham and a control group, we studied 4 groups of rats: A) 15° angulation, B) angulation with 0.1 MPa compression, C) 0.1 MPa compression, and R) reduced mobility. We measured disc height changes and matrix composition (water, deoxyribonucleic acid, glycosaminoglycan, and hyaluronic acid content) after 5 weeks, and proline and sulphate incorporation and messenger ribonucleic acid expression at 5 days and 5 weeks.

RESULTS

After 5 weeks, disc space was significantly narrowed relative to internal controls in all 4 intervention groups. Water content and cellularity (deoxyribonucleic acid content) were not different at interventional levels relative to internal controls and not different between the concave and convex sides of the angulated discs. There was increased glycosaminoglycan content in compressed tissue (in Groups B and C), as expected, and compression resulted in a decrease in hyaluronic acid size. We observed slightly increased incorporation of tritiated proline into the concave side of angulated discs and compressed discs. Asymmetries of gene expression in Groups A and B and some group-wise differences did not identify consistent patterns associating the discs' responses to mechanical alterations.

CONCLUSIONS

Intervertebral discs in this model underwent substantial narrowing after 5 weeks, with minimal alteration in tissue composition and minimal evidence of metabolic changes.