Study design: Retrospective case control study.
Objective: To evaluate the use of the Lenke and King classification systems in the surgical treatment of main thoracic adolescent idiopathic scoliosis (AIS), with a specific focus on radiographic and patient reported outcomes.
Summary of background data: There is considerable debate as to whether King or Lenke classification best fulfills the criteria for a useful classification to determine distal fusion level, i.e., is mentally descriptive of the curve being treated, uses reproducible information to provide guidance in determining distal fusion level, is prognostic of patient reported and radiographic outcomes, and has good user reproducibility.
Methods: Patients operated for AIS between 1986 and 2002 with posterior spinal fusion and dual rod posterior instrumentation were retrospectively classified according to the Lenke and King classification systems. Only patients with Lenke type I curves and minimum 2-year follow-up were included. Preoperative and most recent postoperative radiographs were reviewed. The Lenke and King recommended distal fusion levels were calculated for each patient according to criteria obtained from the literature, and were compared to our actual fusion level. Patients were divided into groups based on our actual distal fusion level (i.e., longer, shorter, or in agreement with Lenke and King). The radiographic parameters and SRS 24 outcomes of patients within each group were compared.
Results: Seventy-five patients with Lenke type 1 AIS were included in the study. The distribution of King curve types were: 31 King II curves, 34 King III curves, 9 King IV curves, and 1 double major curve. Our actual distal fusion level was in agreement with the calculated Lenke recommendation in 49% and the King recommendation in 51% of the cases. Difficulties in using the Lenke classification system were identified in up to 59% of the study patients. There were no statistically significant objectives or patient reported (SRS) differences between the groups fused in agreement, longer, or shorter than the calculated Lenke or King recommendations.
Conclusion: At intermediate follow-up, there does not seem to be significant radiographic or patient reported differences whether fusion levels are in agreement, longer, or shorter than those recommended by the Lenke or King classification systems.