Comparison of Single and Dual Growing Rod Techniques Followed Through Definitive Surgery

Introduction:The management of young children with severe scoliosis remains controversial. Currently, single and dual rod techniques, with or without a short apical fusion followed by periodic lengthening have been the most common procedures. The results through definitive fusion are uncertain.

Methods: We analyzed the results of single and dual rod instrumentation of 28 patients followed through their definitive fusion. There were a variety of diagnoses: idiopathic (infantile and juvenile) 10, neuromuscular 9, syndromes 7, and congenital 2. All patients were followed for a minimum of two years. We analyzed the age at the insertion of the first growing rod, the Cobb measurements of the initial and pre-definitive scoliosis curvature, the postoperative scoliosis correction after the initial and definitive surgery, the same for kyphosis, percentage of correction, mean intervals between lengthenings, T1 to S1, length as a reflection of spinal growth, the spinal growth year, frontal and sagittal balance, and complications (rod breakage and hook displacement).

Results: There were 3 groups: group 1, 5 patients with a single rod plus a short anterior and posterior apical fusion; group 2, 16 patients with single rod instrumentation; and group 3, 7 patients with dual rod instrumentation. The mean age at initial surgery was similar in each group (7.1, 8.7, and 6.9 years). Mean preoperative initial scoliosis measurements were 85, 61, and 92 degrees, respectively. Patients underwent a mean 3.4, 2.8, and 6.1 lengthenings prior to definitive surgery. This occurred at a mean of 3.9, 3.0, and 3.9 years after initial instrumentation. Mean postoperative scoliosis correction after definitive surgery in each group was 65, 39, and 26 degrees, respectively. The mean postoperative kyphosis was 55, 33, and 42 degrees, respectively. Frontal and sagittal balance was better in the single rod instrumentation groups. Spinal growth was slightly better with dual rod instrumentation: 0.3, 1.1, and 1.5 cm/yrs, respectively. Complications of rod breakage and hook displacement were higher in group 1 (4 patients). Only 2 patients in the single rod and one patient in the dual rod groups had these complications.

Conclusions: Growing rod techniques using single or dual rods are effective in controlling curve progression, providing correction and allowing for some spinal growth. The results of dual rod instrumentation were better than single rod instrumentation. This is due to a stronger construct and more frequent lengthenings. The worst results occurred in those who had a short apical fusion. We feel this should no longer be utilized, as it appears to predispose to stiffening of the curve, crankshaft phenomena, less correction, and increased incidence of complications.