Dual growing rod technique followed for three to eleven years until final fusion - The effect of frequency of lengthening

Study Design. Retrospective case review of children completing dual growing rod treatment at our institutions. Patients had a minimum of 2 years follow-up. Objective. To identify the factors influencing dual growing rod treatment outcome followed to final fusion. Summary of Background Data. Published reports on dual growing rod technique results for early onset scoliosis demonstrate it to be safe and effective in curve correction and maintenance as well as in allowing spinal growth. Methods. Between 1990 and 2003, 13 patients with no previous surgery and noncongenital curves underwent final fusion. All had preoperative curve progression over 10 after unsuccessful nonoperative treatment. There were 10 females and 3 males. Average age was 6.6 +/- 2.9 years at initial surgery. There were 3 idiopathic, 1 nonspine congenital anomaly, and 9 syndromic patients. Analysis included age at initial surgery and final fusion, number and frequency of lengthenings, and complications. Radiographic evaluation included changes in Cobb angle, T1-S1 length, and instrumentation length over the treatment period. Results. Cobb angle improved from 81.0 +/- 23 degrees to 35.8 +/- 15 degrees postinitial and 27.7 +/- 17 degrees after final fusion. Average number of lengthenings was 5.2 +/- 3 at an interval of 9.4 +/- 5 months. T1-S1 length increased from 24.4 +/- 3.4 to 29.3 +/- 3.6 cm postinitial and 35.0 +/- 3.7 cm postfinal fusion. Average growth was 1.46 +/- 0.66 cm/year. Those lengthened at <= 6 months (n = 7; range, 5.5-6.7 months) had a higher annual growth rate of 1.8 cm versus 1.0 cm (P = 0.018) from postinitial to postfinal and significantly greater scoliosis correction (79% vs. 48%, P = 0.007) than those lengthened less frequently (n = 6; range, 9-20 months). Six patients experienced complications: 3 within the treatment period, 2 postfinal, and 1 both during and after treatment. Conclusion. Dual growing rod technique resulted in 5.7 +/- 2.9 cm of spinal growth during a 4.37 +/- 2.4 year treatment period. There was significantly greater growth and correctionachieved in those lengthened more frequently.