Late Results of Selective Thoracic Fusion in Adolescent Idiopathic Scoliosis

Purpose: The main aim of surgical treatment for adolescent idiopathic scoliosis (AIS) is to obtain a balanced spine over pelvis while fusing as few motion segments as possible. The purpose of this study is to evaluate the late results of selective thoracic fusion in AIS King Type II or Lenke Type C curves.

Materials and Method: We have performed selective thoracic fusion in 74 AIS patients between the years of 1990-1998. Average age was 13.8 (10.5-18 years). Instrumentation was posterior in 63, anterior in 11 patients. Posterior spinal instrumentation consisted of hook-rod system (CD) in 34 patients (between 1990- 1996) and pedicle screws in 29 patients (after 1997). Posterior instrumentation and fusion ended distally at the stable vertebra in all patients. Stable and neutral vertebra was the same level in 83% of these patients. Instrumentation and fusion stopped at T12 in 58 patients, at T11 in 4 patients and at L1 in 12 patients. In anterior surgery and instrumentation patients, we have used single rod along with titanium mesh cages for the proximal and distal disc spaces.

Results: The average followup is 9.2 (6-14) years. In patients who were surgically treated by hook-rod instrumentation systems, average thoracic and lumbar curve correction was 36% and 32% respectively. The thoracic and lumbar curve correction rates were 52% and 42% in pedicle screw constructs and 61% and 52% in anterior instrumentation cases. We did not need to extend instrumentation distally or to the lumbar curve in any patients. Although there was no pseudoarthrosis or implant failure we have noted an 11.4% correction loss (compared to the initial correction in the first three months) in patients who were treated by instrumentation consisting of hooks and rod.

We have noted a pseudoarthrosis at T11-T12 level in one of the anterior instrumentation patients and it was repaired by posterior instrumentation of the same levels. In another patient in this group, the most proximal screw was pulled-out and it was again revised by posterior instrumentation of the same levels. We did not confront any complications or correction loss in pedicle screw patient group. Anterior surgery and instrumentation saved 1.2 distal motion segments on average from fusion.

Conclusion: Selective thoracic fusion is a good and reliable surgical treatment option in King Type II or Lenke Type C curves. Results of anterior selective thoracic fusion is better than posterior selective thoracic fusion by hook-rod system. Posterior pedicle screw construct provides results close and comparable to anterior selective thoracic fusion.

Selective thoracic fusion should be performed by pedicle screw-rod constructs either by anterior or posterior surgery.