604 - Orientation of the Upper Instrumented Segment Influences Proximal Junc...

Oral Posters: Adult Spinal Deformity

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


R. Lafage(1), B. Line(2), B. Liabaud(1), F. Schwab(1), J. Smith(3), J. Gum(4), C. Ames(5), R. Hostin(6), G. Mundis(7), H.J. Kim(1), S. Bess(8), E. Klineberg(9), V. Lafage(1), International Spine Study Group (ISSG)

(1) Hospital for Special Surgery, Spine Service, New York, NY, United States
(2) Rocky Mountain Hospital For Children Denver, Denver, CO, United States
(3) University of Virginia Medical Center, Department of Neurosurgery, Charlottesville, VA, United States
(4) Norton Leatherman Spine Center, Louisville, KY, United States
(5) San Francisco Medical Center, University of California, Department of Neurosurgery, San Francisco, CA, United States
(6) Baylor Scoliosis Center, Plano, TX, United States
(7) Scripps Clinic Torrey Pines, La Jolla, CA, United States
(8) NYU Langone Medical Center, Spine Division, Department of Orthopaedics, New York, NY, United States
(9) University of California, Davis, Department of Orthopedic Surgery, Sacramento, CA, United States


Introduction and Purpose: Proximal junctional kyphosis (PJK) is common following ASD surgery and limited solutions have proven effective. The final alignment of the upper instrumented vertebral segments has been proposed as a risk factor for PJK, but has not been fully investigated. The hypothesis of this study was the Inclination of the upper instrumented segment of the construct has an impact on proximal junctional kyphosis (PJK)

Methods: This study is a retrospective review of a prospective multicenter database. ASD patients with 2-yr follow-up and fusion to the pelvis were analyzed. Radiographic measurements included pelvic incidence (PI), lumbar lordosis (LL), pelvic tilt (PT), SVA, and 2 UIV parameters: UIV slope (UIV vs horizontal) and inclination of the proximal-end of the construct (best-fit line from UIV to UIV-2 vs vertical, Figure). As a secondary analysis, the UIV parameters were evaluated via a methodology that controlled for the compensatory impact of post-PJK increased PT (PREF). Spino-pelvic and UIV parameters were compared between PJK and noPJK patients and patients evaluated according to the UIV region (UT=upper thoracic, TL=thoracolumbar).

Results: 252 patients (mean age 61.5 yo, 83% F) were included. PJK incidence was 56% at 2-yrs. PJK patients had a greater change in lumbar lordosis (ΔPI-LL) and thoracic kyphosis (ΔTK) than noPJK patients (Table). UT demonstrated no difference in UIV slope for PJK vs. noPJK, however PJK patients had a smaller inclination of the upper instrumented segments within the construct vs. the vertical (11˚ vs. 19˚) and the PREF (33˚ vs. 42˚). Similarly, in the lower thoracic (LT) UIV group, PJK patients had a posterior construct inclination vs. the vertical (-19˚ vs. -13˚) and the PREF (5˚ vs. 10˚).

Conclusions: In this study population, PJK rates exceeded 50% at 2 yrs after ASD surgery. Analysis of the UIV zone revealed that a more posterior construct inclination was present in patients who developed PJK. These results support previous hypotheses suggesting that PJK may develop in response to excessive spinal realignment. Proper rod contouring may reduce the risk of junctional disease. Further investigation of UIV alignment is warranted to reduce junctional pathology.

Comparison PJK vs. non-PJK