Surgical treatment of spinal deformities in spinal muscular atrophy: a single-center experience from China

Growth-friendly Technique or Posterior Spinal Fusion With T-construct Pelvic Fixation in Nonambulatory Spinal Muscular Atrophy With Severe Scoliosis

BACKGROUND

The surgical treatment of scoliosis in type 2 spinal muscular atrophy (SMA2) is challenging and little described in the literature due to its rarity and fragility of the patients. The aim of this study was to review the surgical strategies and outcomes in patients with SMA2 who underwent surgery for scoliosis at a French reference neuromuscular center.

METHODS

All consecutive patients with genetically confirmed SMA2 who underwent spinal surgery between 2009 and 2022 at our French reference center were retrospectively analyzed. They were divided into 2 groups, according to their primary surgery: either magnetically controlled growing rods (MCGR) or posterior spinal fusion (PSF). Demographic, respiratory, and radiologic parameters were collected preoperatively and at the latest follow-up. All complications were reported. Patients and/or caregiver-reported outcome questionnaires were also used to assess the improvement of sitting posture.

RESULTS

Seventeen patients underwent MCGR, and 9 patients underwent PSF during the inclusion period. Mean follow-up was 5.3±1.8 years in the MGCR group, and 8.0±4.5 years in the PSF group. The average age at surgery was 9.7±1.6 years in the MCGR group and 12.6±1.7 years in the PSF group. Pelvic fixation was performed using a Tconstruct (2 sacral and 2 iliac screws). PSF was performed with all levelled pedicle screws. In the MGCR group, upper thoracic fixation was lateral ribs (n=4), vertebral on three levels (n=9), or hybrid costo-vertebral (n=4). No blood transfusion was required. No differences were found between preoperative and postoperative lung function tests for the 2 surgical procedures. The major curve correction rate was 44% in the MCGR group and 55% in the PSF group. The pelvic obliquity at last follow-up was <5 degrees in all patients. Three unplanned surgeries occurred: 1 MGCR change after lengthening and 2 PSF-one for proximal hook migration and one for infection. All patients improved their ability to sit.

CONCLUSION

In this series, PSF and MGCR allowed stable radiographic and respiratory results, with a reduced rate of global complications. Pelvic fixation with T-construct was a reliable and effective technique to correct pelvic obliquity in this population of patients.

Operative treatment of severe scoliosis and pelvic obliquity in patients with spinal muscular atrophy: assessment of outcomes and complications

BACKGROUND

Few reports exist that focus on patients with spinal muscular atrophy (SMA) and severe spinal deformity. In this study, we aimed to report surgical outcomes and complications for SMA patients with severe scoliosis and pelvic obliquity.

METHODS

A retrospective review of data on operatively treated SMA patients with severe scoliosis and pelvic obliquity (minimum major coronal curve Cobb angle > 100° and pelvic obliquity > 20°) was performed. Radiography findings, pulmonary function, motor status, the sitting function score, and perioperative and postoperative complications were the main clinical outcomes examined. Muscular dystrophy spine questionnaire (MDSQ) responses and caregiver responses to four anchor questions (quality of life/comfort/ease of care/overall health) using Likert scales were recorded.

RESULTS

Of 28 consecutive patients, 22 (79%) completed the minimum 2-year follow-up (mean age at surgery = 16.1, 68% female). The mean follow-up duration was 40.3-mo. All patients underwent one-stage posterior spinal fusion (PSF) with pelvic fixation. Radiographic measurements (main coronal curve, kyphosis, pelvic obliquity) were significantly corrected (all p < 0.001) and were maintained at the last follow-up. The mean forced vital capacity (FVC) remained stable during follow-up, with 50% of patients showing improvement. The percentage of patients who could sit independently increased significantly from 22.7% preoperatively to 77.3% postoperatively (p < 0.001). The total sitting-related MDSQ score significantly increased from 8.5 to 12.5 at 6 months postoperatively, and to 15.0 at the last follow-up (p < 0.001). Six instances of complications (two instances each of pneumonia, epiglottic edema, and delayed wound healing) occurred perioperatively in six patients (27.3%), but no surgical intervention was required.

CONCLUSION

Operative treatment significantly improved radiographic parameters and sitting function and maintained pulmonary function without serious complications in SMA patients with severe scoliosis and pelvic obliquity.

Spinal Muscular Atrophy Scoliosis in the Era of Background Therapies-A Review of the Literature

Spinal deformities are considered an important complication of neuromuscular disorders such as spinal muscular atrophy (SMA). SMA patients typically develop progressive early-onset scoliosis, which is associated with increased functional decline, discomfort, and respiratory dysfunction. Over the second decade of the twenty-first century, a lot has changed in terms of the therapeutic options available to people with SMA. Specifically, the use of pharmaceutical agents such as nusinersen (Spinraza), onasemnogene abeparvovec (Zolgensma), and risdiplam (Evrysdi) has dramatically changed the landscape for SMA patients. These medications significantly alter motor- and respiratory functioning, as well as the natural progression of spinal deformities. When evaluating these agents and their impact on the development of scoliosis and motor functioning, it is important to consider the timing of treatment initiation. In patients treated after they had already developed symptoms, a shift of phenotype to a less severe subtype has been observed. This results in a delay in the onset of scoliosis for the less severe SMA types and an increase in early-onset scoliosis for the severe types in patients who would typically not live to develop scoliosis. Patients who receive treatment before they develop symptoms achieve almost normal motor functioning and will likely have a significant decrease in scoliosis prevalence or at least delay its onset.

Profound hypoxemia and hypotension during posterior spinal fusion in a spinal muscular atrophy child with severe scoliosis: a case report

BACKGROUND

Anesthesia for spinal muscular atrophy (SMA) patients undergoing spinal deformity surgery is challenging. We report an unusual case of an SMA girl who developed severe intraoperative hypoxemia and hypotension during posterior spinal fusion related with surgical positioning.

CASE PRESENTATION

A 13-yr-old girl diagnosed with SMA type 2, severe kyphoscoliosis and thoracic deformity was scheduled for elective posterior spinal fusion. She developed severe hypoxemia and profound hypotension intraoperatively in the prone position with surgical table tilted 45° to the right. Though transesophageal echocardiography (TEE) could not be performed due to limited mouth opening, her preoperative computed tomography revealed a severely distorted thoracic cavity with much reduced volume of the right side. A reasonable explanation was when the surgeons performed surgical procedure with the tilted surgical table, the pressure was directly put on the shortest diameter of the significantly deformed thoracic cavity, causing severe compression of the pulmonary artery, resulting in both hypoxemia and hypotension. The patient stabilized when the surgical table was tilted back and successfully went through the surgery in the leveled prone position.

CONCLUSIONS

Spinal fusion surgery is beneficial for SMA patients in preventing scoliosis progression and improving ventilation. However, severe scoliosis and thoracic deformities put them at risk of both hemodynamic and respiratory instability during surgical positioning. When advanced monitoring like TEE is not practical intraoperatively, preoperative imaging may help with differential diagnosis, and guide the surgical positioning to minimize mechanical compression of the thoracic cavity, thereby helping the patient complete the surgery safely.

Unilateral interlaminar fenestration on the convex side provides a reliable access for intrathecal administration of nusinersen in spinal muscular atrophy: a retrospective study

BACKGROUND

As the first gene therapy for spinal muscular atrophy (SMA), nusinersen is supposed to be administrated via intrathecal injection regularly for a lifetime. However, for SMA patients with severe spinal deformities, bony fusion following posterior spinal instrumentation sets great obstacles for the application of nusinersen. Therefore, efforts have been devoted to the exploration of appropriate approach for nusinersen administration. This study aims to evaluate the safety and reliability of unilateral interlaminar fenestration on the convex side during spinal fusion surgery for intrathecal nusinersen injection in SMA.

RESULTS

SMA patients receiving posterior spinal fusion and interlaminar fenestration in Peking Union Medical College Hospital from January 2020 to October 2021 were retrospectively analyzed. 13 patients were included. Of the 13 patients, 10 were classified into SMA type II and 3 into SMA type III. Distal fusion to pelvis was undertaken in 11 patients; while L5 was selected as the lowest instrumented vertebra in the other 2 patients. All patients received interlaminar fenestration on the convex side only with an area of about 15 mm × 20 mm. Fenestration at L2-L3 level was performed in 6 patients; while L3-L4 level was selected for windowing in the remaining 7 patients. 9 of the 13 patients received lumbar puncture and intrathecal nusinersen administration during the 1-year follow-up, with an accumulative total of 50 times. All injections were performed successfully under ultrasound guidance, with no one transferred to radiographic assistance. No severe complications occurred after injection.

CONCLUSIONS

In SMA with severe scoliosis planning to receive posterior spinal fusion, unilateral lumbar interlaminar fenestration on the convex side provides a feasible and reliable access for intrathecal nusinersen administration after surgery.

Influence of Paraspinal Growth-Friendly Spinal Implants in Children with Spinal Muscular Atrophy on Parasol Deformity, Rib-Vertebral Angles, Thoracic, and Lung Volumes

INTRODUCTION

Children with spinal muscular atrophy (SMA) and progressive neuromuscular scoliosis often require early growth-friendly spinal implant (GFSI) treatment for deformity correction with implant fixation either through pedicle screws or bilateral to the spine using ribto pelvis fixation. It has been proposed that the latter fixation may change the collapsing parasol deformity via changes in the rib-vertebral angle (RVA) with a positive effect on thoracic and lung volume. The purpose of this study was to analyze the effect of paraspinal GFSI with bilateral rib-to-pelvis fixation on the parasol deformity, RVA, thoracic, and lung volumes.

METHODS

SMA children with (n = 19) and without (n = 18) GFSI treatment were included. Last follow-up was before definite spinal fusion at puberty. Scoliosis and kyphosis angles, parasol deformity, and index, as well as convex and concave RVA, were measured on radiographs, whereas computed tomography images were used to reconstruct thoracic and lung volumes.

RESULTS

In all SMA children (n = 37; with or without GFSI), convex RVA was smaller than concave values at all times. GFSI did not crucially influence the RVA over the 4.6-year follow-up period. Comparing age- and disease-matched adolescents with and without prior GFSI, no effect of GFSI treatment could be detected on either RVA, thoracic, or lung volumes. Parasol deformity progressed over time despite GFSI.

CONCLUSION

Despite different expectations, implantation of GFSI with bilateral rib-to-pelvis fixation did not positively influence parasol deformity, RVA and/or thoracic, and lung volumes in SMA children with spinal deformity directly and over time.