The Effect of Traditional Single Growing Rod Technique on the Growth of Unsegmented Levels in Mixed-Type Congenital Scoliosis

Abstract

Study design: Retrospective case series.

Objectives: To present outcomes concerning patients with early-onset mixed-type congenital scoliosis (EOMTCS) treated with the traditional single growing rod (TSGR), focusing on the growth of unsegmented levels (USLs).

Methods: Patients with EOMTCS who underwent TSGR and had a minimum of 4 USLs, 4 distractions, and 3-year follow-up were enrolled. Spine radiographs before and after index surgery and at the latest follow-up were evaluated. The length of the concave and convex side of USLs and thoracic parameters were measured. The absolute value and percentage of growth were calculated.

Results: Fourteen patients (mean age, 7.3 ± 2.8 years) were enrolled. The average follow-up duration was 4.9 ± 1.2 years, during which time 84 distractions and 8 final fusions were performed. The average number of USLs was 6.3 ± 2.2. The total and annual percent growth of concave side of USLs was significantly higher than convex side (32.2 ± 13.3% vs. 23.9 ± 9.5%, p = 0.007; 6.8 ± 2.7%/year vs. 5.1% ± 2.2%/year, p = 0.007, respectively). The concave-to-convex ratio of USLs increased from 58.6 ± 6.4 ± 7.6% at baseline to 68.8 ± 9.3% at the latest follow-up (p < 0.001). The Campbell's space available for lung ratio increased from 74.9 ± 11.1% at baseline to 89.6 ± 7.0% at the latest follow-up (p < 0.001).

Conclusions: In patients with EOMTCS, unilateral repetitive lengthening with TSGR can accelerate the growth of the concave side of USLs and improve the symmetry of the thorax.

Keywords: failure of segmentation; mixed-type congenital scoliosis; single growing rod; spinal growth.

Figure 1.

Schema of radiograph measurements. a) Freehand measurement of the concave and convex side of unsegmented levels; b and b’) coronal and sagittal T1-T12 height; c and c’) coronal and sagittal T1-S1 height; d) maximal thoracic width; e) Campbell’s space available for lung ratio; f) maximal thoracic depth.

Figure 2.

A & B) All-spine radiographs before index surgery; C) 3-D CT showed extensive vertebral malformation and segmentation failure; D & E) T2-weighted coronal and axial MRI identified type 2 split cord malformation at the thoracolumbar area. F & G) After index surgery. H & I) After seventh distraction with in-situ fusion.

Figure 3.

A & B) Coronal films before and after index surgery. Patient No. 8 experienced a 50% decrease of MEP when T2 screw insertion (yellow arrow), which was resolved by adjusting the direction of the screw. C & D) Coronal films before and after index surgery. Patient No. 9 had complex deformity with syringomyelia and tethered cord. He suffered a 60% decrease of MEP during correction maneuver, which was resolved by a slight compromise of correction rate (reducing the amount of distraction).