Predictive factors for proximal junctional kyphosis in long fusions to the sacrum in adult spinal deformity.
METHODS
A retrospective study.


OBJECTIVE
To assess the mechanisms and the independent risk factors associated with proximal junctional kyphosis (PJK) in patients treated surgically for adult spinal deformity with long fusions to the sacrum.


BACKGROUND
The occurrence of PJK may be related to preoperative and postoperative sagittal parameters. The mechanisms and risk factors for PJK in adults are not well defined.


METHODS
Consecutive patients who underwent long instrumented fusion surgery (≥6 vertebrae) to the sacrum with a minimum of 2 years of follow-up were retrospectively studied. Risk factors included patient factors, surgical factors, and radiographical parameters such as thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis, pelvic tilt, and pelvic incidence.


RESULTS
Ninety consecutive patients (mean age, 64.5 yr) met inclusion criteria. Radiographical PJK occurred in 37 of the 90 (41%) patients with a mean follow-up of 2.9 years. The most common mechanism of PJK was fracture at the upper instrumented vertebra (UIV) in 19 (51%) patients. Twelve (13%) patients with PJK were treated surgically with proximal extension of the instrumented fusion. Preoperative TK more than 30°, preoperative proximal junctional angle more than 10°, change in LL more than 30°, and pelvic incidence more than 55° were identified as predictors associated with PJK. Achievement of ideal global sagittal realignment (sagittal vertical axis <50 mm, pelvic tilt <20°, and pelvic incidence-LL <±10°) protected against the development of PJK (19% vs. 45%). A multivariate regression analysis revealed changes in LL more than 30°, and preoperative TK more than 30° were the independent risk factors associated with PJK.


CONCLUSIONS
Fracture at the UIV was the most common mechanism for PJK. Change in LL more than 30° and pre-existing TK more than 30° were identified as independent risk factors. Optimal postoperative alignment of the spine protects against the development of PJK. A surgical strategy to minimize PJK may include preoperative planning for reconstructions with a goal of optimal postoperative alignment.


METHODS
3.
*University of California, San Francisco, CA †Department of Orthopaedic Surgery, Hyogo College of Medicine, Nishinomiya, Japan ‡Department of Neurosurgery, Yonsei University College of Medicine, Seoul, Korea §Department of Orthopedics (Unit III), Christian Medical College, Vellore, India; and ¶Department of Orthopedic Surgery, Saiseikai Central Hospital, Tokyo, Japan.
Keishi
K
Maruo
Yoon
Y
Ha
Shinichi
S
Inoue
Sumant
S
Samuel
Eijiro
E
Okada
Serena S
SS
Hu
Vedat
V
Deviren
Shane
S
Burch
Schairer
S
William
Christopher P
CP
Ames
Praveen V
PV
Mummaneni
Dean
D
Chou
Sigurd H
SH
Berven
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000175:diagnosis / Q000209:etiology* / Q000517:prevention & control; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D018579:Patient Selection; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D011859:Radiography; D012189:Retrospective Studies; D012307:Risk Factors; D012447:Sacrum / Q000000981:diagnostic imaging / Q000601:surgery*; D013123:Spinal Fusion / Q000009:adverse effects* / Q000379:methods; D016896:Treatment Outcome