General Session: Adult Spinal Deformity

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


F. Schwab(1), H. Bao(1), R. Lafage(1), S. Glassman(2), S. Bess(3), B. Harris(4), J. Scheer(5), R. Hart(6), B. Line(3), D. Burton(7), H.J. Kim(1), E. Klineberg(8), T. Protopsaltis(4), C. Ames(9), V. Lafage(1), International Spine Study Group

(1) Hospital for Special Surgery, New York, NY, United States
(2) Norton Leatherman Spine Center, Louisville, KY, United States
(3) Rocky Mountain Scoliosis & Spine, Denver, CO, United States
(4) NYU Hospital for Joint Diseases, New York, NY, United States
(5) Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
(6) OHSU, Portland, OR, United States
(7) The University of Kansas Hospital, Kansas, KS, United States
(8) UC Davis Health System, Sacramento, CA, United States
(9) UCSF, San Francisco, CA, United States


Purpose: The purpose of this study is to investigate whether over-correction of the sagittal plane based on age-specific threshold of ideal alignment is a risk factor for PJK.

Introduction: Age and under-correction have often been cited as risk factors for PJK. Recent ASD studies show that alignment targets are age-specific. This study explores PJK as a function of age-adjusted surgical correction goals.

Methods: ASD patients with fusions to the pelvis were included. Age stratification was defined as young adult (YA< 40yo), middle age (MA: 40-65yo), Elderly (ED>65yo). An ANOVA analysis was carried out to compare the 3 groups in terms of one-year post-operative alignment and one-year offset from age-specific alignment targets.

Results: The cohort consisted of 679 patients (61yo, 77F, BMI=28.1); at 1-year post-op there was a significant decrease in PT (29 to 23⁰), spino-pelvic mismatch [PI-LL] (28 to 5⁰), and SVA (110 to 37mm), and a 45.1% overall incidence of PJK. The stratification by age (YA, n=28; MA, n=389; ED, n=262) revealed an increase in PJK incidence with age: YA=17.9%, MA=43.8%, and ED=50.2% (p< 0.001). Post-operatively, patients who developed PJK had smaller PI-LL mismatches (ED 0.8 vs. 9.8°, MA 3.1 vs. 7.3°), without significant differences in PT or SVA. The analysis of the post-operative offset from age-specific norm revealed that the overall, undifferentiated cohort and the two older sub-groups that developed PJK were over-corrected in terms of PI-LL mismatch versus the norm (All: 2.8 vs. -5.2°, MA:-1 vs. +4°, ED: -11 vs. -2°), as well as SVA versus the norm (All: 7 vs. -10mm, MA: 10 vs. -3mm, ED: -18 vs. -6mm). The coefficients of correlation between the magnitude of the PJK angle and the offsets from age-adjusted objective were 0.320 for PI-LL, 0.114 for PT and 0.136 for SVA.

Conclusions: Overall, this study suggests that patients with PJK were overcorrected versus age-adjusted alignment objectives. Certainly, elderly patients have risks for PJK such as osteoporosis, and other co-morbidities that are difficult to mitigate. On the other hand, optimizing alignment is a variable that can be controlled. This emphasizes the need for surgeons to incorporate age-specific alignment targets into the standard pre-operative planning process.