Abstract and Introduction
Study Design: Retrospective cross-sectional study.
Objective: The aim was to describe spinopelvic alignment types by pelvic incidence (PI) and age to compare the Roussouly classification between pediatric and adult populations.
Summary of Background Data: The Roussouly classification was validated for adults. Alignment types may vary during growth.
Materials and Methods: Radiographs of 1706 non pathologic individuals (5–49 yr) were analyzed. Individuals ≤19 years were stratified by chronological age and skeletal maturity (triradiate cartilage, Risser), and compared with adults. Global and spinopelvic alignment parameters were assessed. Roussouly Types 1, 2, 3, 3A (anteverted pelvis), and 4 were determined. The distribution of parameters was analyzed by Bayesian inference. The relationship between PI and age by Roussouly type was modeled by linear regression.
Results: The Sagittal Vertical Axis C7 decreased during growth and was significantly smaller in adults (20–34 yr) (Pr>0.99). Thoracic kyphosis and lumbar lordosis increased during growth and were larger in adults (Pr<0.025). Lordosis increased mainly in the cranial arch (Pr<0.025). PI and pelvic tilt increased during growth and were larger in adults (Pr<0.025). In children and adolescents, PI<45° represented the largest proportion, significantly larger compared with adults (Pr>0.99). Proportions of Roussouly Types 1 and 2 were similar throughout ages. Types 3 and 4 were rarer during the prepubertal period (Pr<0.025). The proportion of Type 3A was significantly higher in children and adolescents (Pr>0.99). Linear regression showed that Type 4 had the largest PI increase with age, with significantly higher curve slope compared with other types (Pr>0.9999). Types 3, 3A and 2 had similar slopes and lowest PI increase with age.
Conclusion: Global and spinopelvic alignment changed during childhood and adolescence, leading to different kyphosis and lordosis distribution compared with adults. Growth-related PI increase influenced Roussouly types with typical predominance of Type 3A in the pediatric population and larger PI increase in Type 4.
Level of Evidence: Level III.
Sagittal alignment of the trunk varies during growth and different physiologic patterns have been clinically described as neutral, sway-back, and leaning-forward positions. Gender-specific differences exist during prepubertal and pubertal growth stages. Similar observations were made on radiographs, where segmental thoracolumbar alignment differed by growth stage, with lower thoracic kyphosis (TK) in girls during peak height velocity. Accurate TK and lumbar lordosis (LL) assessment is essential when treating patients with spinal deformity. In clinical practice, relationships between TK, LL, and spinopelvic alignment parameters may be used for surgical planning in adolescent idiopathic scoliosis.
Proportionate kyphosis and lordosis distribution according to spinopelvic configuration should be considered. As sagittal pelvic width increases during growth, pelvic incidence (PI) augments from childhood to adulthood. These growth-related changes of pelvic anatomy trigger the thoracolumbar shape and global trunk alignment.[6,7] In adults, relationships between PI, LL, and TK are well established. It remains unclear to what extent they can be applied to children and adolescents. Roussouly et al described four alignment types in asymptomatic adults, based on sacral slope (SS), thoracolumbar inflection point, and lumbar apex, the distribution between cranial and caudal arch of LL. This classification was completed by a fifth subtype with typical pelvic anteversion, mainly in younger subjects.
The Roussouly classification has not been validated for children and adolescents, and it remains unclear how proportions of alignment types vary according to gender, PI, and age. We hypothesize that normal variations exist during growth.
The purpose of this observational study was to describe spinopelvic alignment types by age and PI, and to compare the Roussouly classification between pediatric and adult populations without spinal deformity.
Spine. 2022;47(18):1303-1313. © 2022 Lippincott Williams & Wilkins