The Results of Selective Anterior Thoracic Fusion for King II / Lenke Type CL Adolescent Idiopathic Scoliosis

Walter A. Morgenstern, MD;
Peter J. Metz–Stavenhagen, MD,
Thomas Seidel, MD;
0laf Hupfer, MD;
Thomas R. Haher, MD;
Andrew A. Merola, MD;

INTRODUCTION:
In order to overcome a high intra– and interobserver reliability, a new classification system for Adolescent Idiopathic Scoliosis (AIS) was presented. The type C (King II) of this system describes pronounced lumbar curves in which the center sacral vertical line (CSVL) lies outside of the lumbar apical vertebra on the concavity of the curve. This retrospective study analyzed the results of a group of patients who received selective ATF for type C curves. The purpose of the study was to analyze the ability of the new classification system to predict the outcome of anterior thoracic fusion in combined AIS type Lenke Cl, and to define predictive parameters revealed in the study.

METHODS:
From 1989 to 1994, 407 patients underwent anterior fusion for scoliotic deformities of different etiologies, 174 of them had anterior thoracic fusion. 21 of them (<19 yo) who had combined AIS with a Risser sign <5, showed the criteria of a Lenke type C curve. 14 patients had a minimum follow–up of 2 yrs. The parameter analysis included coronal and sagittal corrections. Horizontalization of lumbar and thoracic endvertbrae and correction of both curves were measured on preop bending and Cotrel traction films.

RESULTS:
14 female patients (avg 15.4 yo) were followed for an average period of 3.3 yrs. Average correction of the lumbar curve and the thoracic curve were 46.0% (+/–18.5) and 54.7% (+/–16.4) respectively. Patients with preoperative horizontalization on Cotrel traction films of the lumbar endvertebra of less than 6° had an avg. correction of the lumbar curve of 60.1%(+/–8.1) and an avg. loss of correction of 3.6% (+/–14.6), those with more than 5° had 27.2% (+/–9.7) and 19.4%(+/–11.5) respectively. Horizontalization of the thoracic endvertebra of less than 100 on preoperative Cotrel traction films had an avg. correction of the lumbar curve of 62.7% (+/–8.7) and –2.8%(+/–10.4) loss of correction; those with more than 9° had 44.6%(+/–13) and 12.8%(+/–13.6) respectively. Preoperative correction of the thoracic curve on Cotrel traction films of more than 50% had an avg. correction of the lumbar curve of 53.1% (+/–18.3), and loss of lumbar correction was –1.9% (+/–8.9)– less than 50% had 38.9% (+/–15.7) and 22 %(+/–10.7) respectively.

CONCLUSION:
Patients with combined AIS and pronounced lumbar curves (type C) can be treated with selective anterior thoracic fusion. Horizontalization of the thoracic and lumbar endvertebrae as well as correction of the thoracic curve on preoperative Cotrel traction films have an important predictive value for the unfused lumbar curve and are superior to bending films in this context.