Takahito Fujimori1, Tracey P Bastrom2, Carrie E Bartley2, Peter O Newton3. 1. Department of Orthopedic Surgery, Rady Children's Hospital, 3030 Children's Way, Suite 410, San Diego, CA 92123, USA; Department of Orthopedic Surgery, Sumitomo Hospital, 5-3-20 Nakanoshima, Kita Ward, Osaka, Osaka Prefecture 530-0005, Japan. 2. Department of Orthopedic Surgery, Rady Children's Hospital, 3030 Children's Way, Suite 410, San Diego, CA 92123, USA. 3. Department of Orthopedic Surgery, Rady Children's Hospital, 3030 Children's Way, Suite 410, San Diego, CA 92123, USA. Electronic address: pnewton@rchsd.org.
Abstract
STUDY DESIGN: Retrospective study. OBJECTIVES: To examine the characteristics of Lenke type 1 curves based on the level of the apical vertebra. SUMMARY OF BACKGROUND DATA: The Lenke classification is the most used system for adolescent idiopathic scoliosis, with approximately 50% of the curves falling into the Lenke 1 curve type category. METHODS: A total of 611 Lenke 1 curves in a prospectively collected multicenter adolescent idiopathic scoliosis study were analyzed. Minimum follow-up was ≥ 2 years. Curves were subdivided into 3 groups according to their apex: the typical Lenke 1 curve group included apices from T7/8 to T10 (511 patients), the proximal group included apices from T4 to T7 (45 patients), and the distal group included apices from T10/11 to T11/12 (50 patients). Preoperative and postoperative radiographic and clinical outcomes were compared among the 3 groups. RESULTS: The proximal and distal groups included significantly more left thoracic curves (proximal: 29%; typical: 1.8%; distal: 19%; p < .01). Flexibility of the main thoracic curve was significantly different among the 3 groups (proximal: 32% ± 17%; typical: 46% ± 18%; distal: 57% ± 18%; p < .001). The distal group included significantly more "A" lumbar modifiers (proximal: 29%; typical: 53%; distal: 96%; p < .01) and had curves characteristics similar to King type 4 curves (L4 tilted to the right: Lenke 1AR). The average lowest instrumented vertebra was significantly lower in the distal group (proximal: T12; typical: L1; distal: L2; p < .01). The proximal group had significantly greater thoracic kyphosis (proximal: 30° ± 18°; typical: 20° ± 13°, distal: 20° ± 10°; p < .001) and more fusion segments (proximal: 10; typical: 9; distal: 9; p < .03). CONCLUSIONS: Curves categorized as Lenke 1 curves were less homogeneous than expected. Using only the Lenke type 1 designation to define a study population may introduce unintended bias to the study design.
STUDY DESIGN: Retrospective study. OBJECTIVES: To examine the characteristics of Lenke type 1 curves based on the level of the apical vertebra. SUMMARY OF BACKGROUND DATA: The Lenke classification is the most used system for adolescent idiopathic scoliosis, with approximately 50% of the curves falling into the Lenke 1 curve type category. METHODS: A total of 611 Lenke 1 curves in a prospectively collected multicenter adolescent idiopathic scoliosis study were analyzed. Minimum follow-up was ≥ 2 years. Curves were subdivided into 3 groups according to their apex: the typical Lenke 1 curve group included apices from T7/8 to T10 (511 patients), the proximal group included apices from T4 to T7 (45 patients), and the distal group included apices from T10/11 to T11/12 (50 patients). Preoperative and postoperative radiographic and clinical outcomes were compared among the 3 groups. RESULTS: The proximal and distal groups included significantly more left thoracic curves (proximal: 29%; typical: 1.8%; distal: 19%; p < .01). Flexibility of the main thoracic curve was significantly different among the 3 groups (proximal: 32% ± 17%; typical: 46% ± 18%; distal: 57% ± 18%; p < .001). The distal group included significantly more "A" lumbar modifiers (proximal: 29%; typical: 53%; distal: 96%; p < .01) and had curves characteristics similar to King type 4 curves (L4 tilted to the right: Lenke 1AR). The average lowest instrumented vertebra was significantly lower in the distal group (proximal: T12; typical: L1; distal: L2; p < .01). The proximal group had significantly greater thoracic kyphosis (proximal: 30° ± 18°; typical: 20° ± 13°, distal: 20° ± 10°; p < .001) and more fusion segments (proximal: 10; typical: 9; distal: 9; p < .03). CONCLUSIONS: Curves categorized as Lenke 1 curves were less homogeneous than expected. Using only the Lenke type 1 designation to define a study population may introduce unintended bias to the study design.