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

Abstract

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.

Finite Element Comparison of the Spring Distraction System and the Traditional Growing Rod for the Treatment of Early Onset Scoliosis

“…The use of the SDS springs allows for increased loadsharing of the IVDs during periods of increased loading. Recent studies on “growth-friendly” implants have shown that IVDs within a distraction construct show a decrease in height and volume over time coincident with degenerative changes seen on MRI 20,21 . In the present model, the SDS IVDs were under more distraction during the first 6 months.…”

“…Recent studies on ''growth-friendly'' implants have shown that IVDs within a distraction construct show a decrease in height and volume over time coincident with degenerative changes seen on MRI. 20,21 In the present model, the SDS IVDs were under more distraction during the first 6 months. However, this effect reversed after the first TGR distraction, with the spanned IVDs in the TGR model under increasing amounts of distraction, whereas the IVDs in the SDS model were increasingly subjected to compressive forces again.…”

“…17,18 The continuous SDS force application removes the need for reoperations and the dynamic coupling of the rods should allow for residual spinal motion and could prevent stress-shielding of the spine, which may lower implant stresses, and prevent intervertebral disc (IVD) height loss. [19][20][21] Investigating these potential advantages in vivo is difficult, especially from an ethical point of view. However, in-silico comparisons between implants that use continuous distractive forces (e.g., SDS) and those that use intermittent forces (e.g., TGR) could be a second-best alternative.…”

Disc and Vertebral Body Morphology From Birth to Adulthood

“…Recently, there have also been several studies suggesting an important role of the intervertebral disc in the treatment of early onset scoliosis with traditional growing rod distractions. 27,28 These radiological studies have shown (in 2D and 3D) that epiphyseal growth with distraction-based growing rods, coincides with height-and volume loss of the intervertebral disc. The present study shows that in preadolescent normal growth, intervertebral disc volume increases while intervertebral disc height remains stable (thoracic) or increases somewhat (lumbar).…”

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

“…Literature concerning bone health in children and adolescents after treatment with GFSI is very limited. Morphometric changes of vertebral bodies and disks in such cases were analyzed by Hasler et al, Lippross et al, and Hell et all, reporting reduced vertebral body depth and height, as well as pedicle size, also accompanied by degenerated intervertebral disks with smaller volume 25–28 . Cognetti et al observed in their case report smaller pedicles on the side of the implanted growing rods 29 .…”