End Results of Dual Growing Rod Technique Followed for 3 to 11 Years Until Final Fusion: The Effect of Frequency of Lengthening**

Summary: 15 patients underwent final fusion after dual growing rod instrumentation, and were followed for between 4 and 12 years. Primary Cobb angle was improved with initial surgery, maintained throughout treatment, and improved further at final-fusion. Average growth of 1.2cm per year from postinitial surgery through to post-final surgery was achieved. Although not significant, increased yearly growth was seen in those lengthened more frequently.

Purpose: To identify factors influencing the outcome of dual growing rod constructs followed to final fusion.

Methods: Between July 1992 and December 2000 21 patients with early onset scoliosis underwent final fusion following dual growing rod technique. 15 were treated primarily and were included. There were 12 females and 3 males, with an average age of 7+2 years (range 2+1 to 14). There were 3 idiopathic, 3 congenital and 9 syndromic patients, with 9 thoracic and 6 thoracolumbar curves.

Results: Average length of construct was 13.8 levels. Average pre-op Cobb angle was 81.2°, postinitial 39.4°, pre-final 42.5° and following final-fusion 32.5°. The average number of lengthenings was 5.3 at an interval of 9.0 months. The length of T1-S1 increased from 24.4 to 29.2cm following initial surgery, and to 34.4cm post final-fusion, giving an average growth of 1.2cm per year. Excluding congenital patients, those undergoing shorter interval lengthening of 6 months or less (n=7, range 5.5-6.7 months), had a higher annual growth rate of 1.5cm vs. 1.0cm (p=0.06) in those lengthened less frequently (n=6, range 9-20 months). 5 patients experienced complications, 6 in 3 patients within the treatment phase (2 rod breakages, 1 wound granuloma), and 3 in 3 patients post final-fusion (2 construct extensions, 1 pseudarthrosis). There was no neurological deficit, junctional kyphosis or crankshaft phenomenon in this group.

Conclusions: Primary curve Cobb angle was maintained throughout the treatment phase, and improved further following final-fusion, in this group of patients with a variety of etiologies. Dual growing rod technique in early onset scoliosis achieves over 5cm of extra spinal growth in an average of 4.6 years. Whilst not reaching significance, there was greater growth achieved in those lengthened more frequently.

FDA Diclosure Cleared: No ** Tandem Connector