Single distraction-rod constructs in severe early-onset scoliosis: Indications and outcomes

Since the study of Thompson, et al in 2005, use of dual-growing rod constructs have become the gold standard for operative treatment in early-onset scoliosis. However, use of dual-growing rod constructs may not be possible, due to patient size and the type, location and severity of the spinal deformity.

The purpose of this study is to: (1) describe the deformities treated with single-growing rod constructs, and (2) report the outcomes of single-growing rods since 2005.

Observational, descriptive case series METHODS: A prospective, multi-center, international database of early-onset scoliosis patients were queried to identify all patients with single traditional growing rods (sTGR) or magnetically-controlled growing rods (sMCGR) since the 2005. Patients were excluded if there were greater than 1 rod or if there was less than 2 years of follow-up postoperatively. Twenty-five patients (13 female, 12 male) were identified from the database query, which satisfied the inclusion and exclusion criteria.

Mean age at index surgery was 4.7 years (1.3 to 9.3 years) and mean follow-up was 4.3 years (2.0 to 10.6 years). Eleven patients were classified as congenital (all mixed-type), six neuromuscular, five idiopathic and three syndromic. Proximal foundations were ribs in 23 patients and pedicle screws in two patients. The distal foundations were the spine in 25 patients and three pelvic S-hooks. All single rods were on the concave side of the deformity. Interpretation of preoperative radiographs determined in 72% (18/25) of cases dual growing rods would be difficult and/or suboptimal due to patient size (longitudinal a/o weight) and/or kyphosis/kyphoscoliosis with severe rotation. Maximal coronal deformity improved 30% (83.9 degrees to 58.6 degrees) at latest follow-up. Maximal kyphosis increased 17% (45.6 degrees to 57.4 degrees). Postoperative length increase: T1-T12, 17.0 mm (4.6 mm/year); T1-S1, 34 mm (9.4 mm/year). Total secondary surgeries for TGRs were 100: 66 lengthenings, 32 revisions, two unknown. 10 MCGRs secondary surgeries occurred in nine patients (seven for maximized actuators and three for foundation migration). At latest follow-up 20 continued with lengthenings (five TGR & 15 MCGR), four underwent definitive fusions, and one completed lengthening (implants retained).

Treatment of severe EOS with single rods demonstrated a 30% coronal correction. T1-S1 length increased at 9.4 mm/year and T1-T12 length at 4.6 mm/year, which are comparable to published reports on dual MCGRs. Single TGRs and MCGRs in EOS can provide acceptable short-term outcomes when dual rods are not deemed appropriate.

The use of single growing rod constructs, in the 4-8 years old patient with EOS, can achieve reasonable short-term radiographic outcomes.