Does Thoracic Hypokyphosis Matter in Lenke Type 1 Adolescent Idiopathic Scoliosis?

Abstract

Study DesignWe analyzed a prospective cohort of Lenke 1ABC adolescent idiopathic scoliosis (AIS) patients based on differences in T5–T12 sagittal alignment. ObjectiveOur objective was to determine whether patients with hypokyphotic scoliosis demonstrate unique characteristics in terms of baseline health status and response to surgery. Background SummaryRight thoracic AIS often presents as a hypokyphotic scoliosis, with rotatory deformity resulting in a diminution of the normal thoracic kyphosis. The perceived importance is indicated by the inclusion of a sagittal plane modifier within Lenke’s classification system for AIS and studies examining reduction strategies to restore thoracic kyphosis. MethodsWe grouped patients based on thoracic kyphosis, measured from T5 to T12, as either less than 10° (hypokyphotic) or greater than or equal to 10° (normal/kyphotic). We used Student t test for independent samples to compare continuous variables between the hypokyphotic and normal/kyphotic groups. ResultsThere was a significant difference in age between groups (mean age, 14.9 years in the hypokyphotic group versus 13.4 years in the normal/kyphotic group; p = .007). Differences in baseline health status measures were statistically significant but small. Hypokyphotic patients reported less pain than normal/kyphotic patients, with a mean Scoliosis Research Society (SRS) Pain score of 4.15 versus 4.03 (p = .044), better SRS Mental Domain scores (4.06 vs. 3.92; p = .026), and better SRS Total scores (3.92 vs. 3.83, p = .027). The hypokyphotic group also had better SRS Appearance (3.36 vs. 3.30) and Activity scores (4.20 vs. 4.13), but these differences did not reach statistical significance. ConclusionsThere were no differences in baseline or 2-year postoperative outcome scores in Lenke 1 AIS patients with hypokyphosis compared with patients with normal sagittal alignment. Maintenance of or restoration to normal kyphosis in hypokyphotic patients with Lenke 1 AIS may not improve clinical outcome compared with patients who remain lordotic after surgical correction.