397 - Does Pelvic Incidence Increase with Age? - An Analysis of 1625 Adults...

Oral Posters: Adult Spinal Deformity

Presented by: H. Bao - View Audio/Video Presentation (Members Only)


H. Bao(1), B. Liabaud(2), J.J. Varghese(1), R. Lafage(3), B.G. Diebo(2), C.M. Jalai(4), S. Ramchandran(5), G.W. Poorman(5), D.L. Cruz(6), T.J. Errico(5), T.S. Protopsaltis(5), P.G. Passias(5), A.J. Buckland(5), F.J. Schwab(7), V. Lafage(3)

(1) Hospital for Special Surgery, New York, NY, United States
(2) SUNY Downstate Medical Center, Brooklyn, NY, United States
(3) Hospital for Special Surgery, Spine Research, New York, NY, United States
(4) University of Vermont College of Medicine, Burlington, VT, United States
(5) Hospital for Joint Diseases at NYU Langone Medical Center, Department of Orthopaedic Surgery, New York, NY, United States
(6) Temple University Hospital, Philadelphia, PA, United States
(7) Hospital for Special Surgery, Spine Service, New York, NY, United States


Background: Pelvic incidence (PI) has been proposed as the foundation of spinal alignment, determining the orientation of the sacrum, pelvic tilt (PT) and the capacity for compensation. PI has also been shown to be constant once skeletal maturity is achieved. However, recent reports argue that PI increases after 60 years with a strong correlation with age. Due to small sample sizes in prior studies, a large sample sized study should be conducted to clarify the change in PI in the aging population.

Purpose: To investigate if PI increases with age.

Study Design/Setting: Retrospective review of two single-center full-body imaging databases.

Patient Sample: Patient database included subjects who visited a spine surgeon´s office with various spinal degenerative and deformity pathologies, reflecting a sample of the general population; The normative database included healthy adult volunteers.

Outcome Measures: Radiographic parameters including PI, PT, lumbar lordosis (LL), sagittal vertical axis (SVA) were measured on full-body sagittal images.

Methods: Patients with previous spinal surgery and with spondylolisthesis were excluded. Subjects were divided into 6 age subgroups with 10-year intervals (25-34 years, 35-44 years, 45-54 years, 55-64 years, 65-74 years and over 75 years). PI was compared between age subgroups and between genders. Linear regressions were performed to identify factors associated with increased PI in the patient sample, with age, BMI, gender and spinal alignment (evaluated as normal, compensated and decompensated) as independent variables.

Results: There were 1510 symptomatic patients (550 male, 960 female) and 115 asymptomatic subjects. PI averaged 54.1°±14.4 (range 11-105°) in all patients. Comparison of PI between age subgroups revealed a significant difference (p< 0.001). In detail, PI was significantly higher in the 45-54y age group than the 35-44y age group (55.8° vs. 49.7°, p=< 0.001). After 45 years, PI remained unchanged. Between genders, PI was significantly higher in women than men (M: 51.8° vs. F: 55.5°, p< 0.001) and there were significant PI differences between genders after age 45. In the asymptomatic subjects, however, a nonsignificant trend of PI increase was observed (p=0.548), and females had a higher PI than males (p=0.007), especially after 55 years old. In regression analysis of patient samples, age, gender and malalignment were identified as associated factors with R2 of 0.22 (p< 0.001).

Conclusions: PI is higher in female patients and in older patients, especially those over 45 years old. Spinal malalignment also may have a role in increased PI; however, a causal link cannot yet be identified due to lack of longitudinal data. These findings may benefit both surgical decision-making and planning, but should also encourage further investigation.