Predictive Factors for Proximal Junctional Kyphosis in Long Fusions to the Sacrum in Adult Spinal Deformity.

*University of California, San Francisco, California, USA †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 ††Department of Orthopedic Surgery, Saiseikai Central Hospital, Tokyo, Japan.
Spine (Impact Factor: 2.45). 08/2013; DOI: 10.1097/BRS.0b013e3182a51d43
Source: PubMed

ABSTRACT Study Design. A retrospective studyObjective. 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.Summary of Background Data. The occurrence of PJKmay be related to preoperative and postoperative sagittal parameters. The mechanisms and risk factors for PJK in adultsare not well-defined.Methods. A consecutive patients who underwent long instrumented fusionsurgery (≥6 vertebrae) to the sacrum with a minimum of 2 years follow-up were retrospectively studied.Risk factorsincluded patient factors, surgical factorsand radiographic parameters such as thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic tilt (PT), and pelvic incidence (PI).Results. Ninety consecutive patients (mean age: 64.5 years) met inclusion criteria. Radiographic PJK occurred in 37of the90 (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 proximalextension of the instrumented fusion. Preoperative TK >30°, preoperative proximal junctional angle (PJA) >10°, change in LL >30°,and PI >55° were identified as predictors associated with PJK. Achievement of ideal global sagittal realignment (SVA <50mm, PT <20°,and PI-LL <±10°) protected against the development ofPJK(19% vs. 45%).Amultivariate regression analysisrevealed changesin LL >30° and preoperative TK >30° were the independent risk factors associated with PJK.Conclusion. Fracture at the UIV was the most common mechanism for PJK. Change in LL >30° and preexisting TK >30° were identified as independent risk factors. Optimal postoperative alignment of the spine protectsagainst the development of PJK. A surgical strategy to minimize PJK may include preoperative planning forreconstructions with a goal of optimal postoperative alignment.

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