Vertebral body changes after continuous spinal distraction in scoliotic children

Scoliosis Treatment With Growth-Friendly Spinal Implants (GFSI) Relates to Low Bone Mineral Mass in Children With Spinal Muscular Atrophy

BACKGROUND

Children with spinal muscular atrophy (SMA) frequently develop neuromuscular scoliosis at an early age, requiring surgical treatment with growth-friendly spinal implants (GFSI), such as magnetically controlled growing rods. This study investigated the effect of GFSI on the volumetric bone mineral density (vBMD) of the spine in SMA children.

METHODS

Seventeen children (age 13.2±1.2 y) with SMA and GFSI-treated spinal deformity were compared with 25 scoliotic SMA children (age 12.9±1.7 y) without prior surgical treatment as well as age-matched healthy controls (n=29; age 13.3±2.0). Clinical, radiologic, and demographic data were analyzed. For the calculation of the vBMD Z-scores of the thoracic and lumbar vertebrae, phantom precalibrated spinal computed tomography scans were analyzed using quantitative computed tomography (QCT).

RESULTS

Average vBMD was lower in SMA patients with GFSI (82.1±8.4 mg/cm3) compared with those without prior treatment (108.0±6.8 mg/cm3). The difference was more prominent in and around the thoracolumbar region. The vBMD of all SMA patients was significantly lower in comparison with healthy controls, especially in SMA patients with previous fragility fractures.

CONCLUSIONS

The results of this study support the hypothesis of reduced vertebral bone mineral mass in SMA children with scoliosis at the end of GFSI treatment in comparison with SMA patients undergoing primary spinal fusion. Improving vBMD through pharmaceutical therapy in SMA patients could have a beneficial effect on the surgical outcome of scoliosis correction while reducing complications.

LEVEL OF EVIDENCE

Therapeutic Level III.

Thoracic insufficiency syndrome: Approaches to assessment and management

Thoracic insufficiency syndrome (TIS) was described in 2003 as the inability of the thorax to support normal respiration or lung growth. TIS includes a broad and disparate group of typically degenerative thoracospinal conditions. Although TIS arises due to a heterogeneous group of disorders and thus its incidence is not well quantified, general approaches to management and treatment exist. Evolving imaging techniques and measurements of health-related quality of life augment tests of pulmonary function to quantify disease burden, longitudinally and pre- and post-intervention. Intervention is primarily via growth-sparing surgery, for which several device options exist, to preserve vertical growth prior to a definitive spinal fusion at skeletal maturity.

Children with Spinal Muscular Atrophy Have Reduced Vertebral Body Height and Depth and Pedicle Size in Comparison to Age-Matched Healthy Controls

BACKGROUND

Most children with spinal muscular atrophy (SMA) develop spinal deformity, which may require surgical intervention. In addition to poor bone stock, vertebral body shape may hinder the placement of spinal implants resulting in complications and poor outcome. The aim of this study was to analyze whether vertebral body morphology of children and adolescents with SMA is altered in comparison to healthy age-matched controls.

METHODS

In this prospective cohort study, 17 children with SMA (mean age 8.7 ±1.0 years) and 13 adolescents with SMA (mean age 13.6 ±1.4 years), all with some degree of neuromuscular scoliosis, were analyzed by standardized radiographic measurements to evaluate vertebral body height and depth. Results were compared with age-matched healthy controls (n = 10 children; mean age 9.1 ± 1.6 years; n = 20 adolescents, mean age 13.1 ± 0.5 years). Computed tomography scans of 27 adolescents with SMA (13.5 ±1.2 years) and 25 healthy age-matched controls (13.8 ±2.0 years) were analyzed to define pedicle diameters.

RESULTS

All children and adolescents with SMA had decreased vertebral height and depth in comparison to age-matched healthy controls. In adolescents, reduced depth was more pronounced than height in the thoracic spine. Pedicle size was significantly reduced in the lower thoracic and lumbar area.

CONCLUSIONS

Reduced vertebral body height and depth and pedicle size in children and adolescents with SMA may influence surgical treatment of spinal deformity. Surgeons should be aware of anatomical differences and choose implant devices accordingly.

Smaller Intervertebral Disc Volume and More Disc Degeneration after Spinal Distraction in Scoliotic Children

In recent decades, magnetically controlled growing rods (MCGR) were established to treat progressive early-onset scoliosis. The aim of this investigation was to assess the effect of long-term MCGR with continuous distraction on intervertebral discs in scoliotic children. Magnetic resonance imaging (MRI) of 33 children with spinal muscular atrophy was analyzed by grading intervertebral disc degeneration (IDD) and measuring intervertebral disc volume. Cohort I (n = 17) were children who had continuous spinal distraction with MCGRs for 5.1 years and MRI before (av. age 8.1) and after (av. age 13.4) MCGR treatment. Cohort II (n = 16, av. age 13.7) were patients without prior surgical treatment. Lumbar intervertebral disc volume of cohort I did not change during 5.1 years of MCGR treatment, whereas disc volumes were significantly larger in age- and disease-matched children without prior treatment (cohort II). Cohort I showed more IDD after MCGR treatment in comparison to early MRI studies of the same patients and children without surgical treatment. MRI data showed a volume reduction and disc degeneration of lower thoracic and lumbar intervertebral discs in scoliotic children after continuous spinal distraction with MCGRs. These effects were confirmed in the same subjects before and after treatment as well as in surgically untreated controls.