595 - Revealing Different Compensation Model in Asymptomatic Adults: A Clust...

Oral Posters: Adult Spinal Deformity

Presented by: R. Lafage - View Audio/Video Presentation (Members Only)

Author(s):

H. Bao(1), R. Lafage(2), B. Liabaud(1), J. Elysée(1), G. Poorman(3), C. Jalai(3), P. Passias(3), A. Buckland(3), S. Bess(3), T. Errico(3), M. Gupta(4), H.J. Kim(1), F. Schwab(1), V. Lafage(1)

(1) Hospital for Special Surgery, Spine Service, New York, NY, United States
(2) Spine Service, Hospital for Special Surgery, Spine Service, New York, NY, United States
(3) NYU Langone Medical Center, Spine Division, Department of Orthopaedics, New York, NY, United States
(4) Washington University School of Medicine, Department of Orthopaedic Surgery, St. Louis, MO, United States

Abstract

Purpose: To propose a full-body sagittal profile classification in normal population based on full-body imaging.

Introduction: A comprehensive understanding of normative sagittal profile is necessary for treating adult spinal deformity. Roussouly described four sagittal alignment types based on pelvic incidence, lumbar lordosis and location of lumbar apex. However, the lower limb, an ingredient of compensatory mechanisms, is missing from this classification. Moreover, the population with compensated sagittal alignment is overlooked in the Roussouly classification.

Methods: This is a retrospective single center study of 116 healthy volunteers with full-body X-rays. Sagittal radiographic parameters from cervical region to lower limbs were obtained as well as demographic data. Cluster analysis including all sagittal parameters was at first performed, and then ANOVA was performed between sub-clusters to eliminate the non-significantly different parameter. This loop was repeated until all parameters were significantly different between each sub-cluster.

Results: Three types of full-body sagittal profile were finalized according to cluster analysis with 10 radiographic parameters: Hyperlordosis type (77 subjects), neutral type (28 subjects) and compensated type (11 subjects). From lower limbs to the upper region, radiographic parameters included knee angle, pelvic shift, pelvic angle, pelvic tilt (PT), PI-LL, C7-S1 SVA, T1-pelvic angle (TPA), T1 slope, C2-C7 angle and C2-C7 SVA. In addition, age was significantly different (45.8 years in hyperlordosis type, 57.6 in neutral type and 62.5 in compensated type, p< 0.001). Age-matched subjects were randomly selected with 11 subjects in each type. ANOVA analysis further revealed that all parameters but PT and C2-C7 angle showed significant difference.

Conclusion: The current 3 types of full-body sagittal profile in normal adults included parameters from cervical region to knee, indicating that subjects should be evaluated with full-length imaging. All 3 types exist regardless of age, but the distribution may vary.

Schematic of 3 Full-Body Sagittal Profiles