Proximal Junctional Kyphosis Prevention in Adult Spinal Deformity Surgery: A Technical Review of Tethering and Adjunctive Strategies

BACKGROUND AND OBJECTIVES: Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) remain significant complications after long-segment posterior fusion for adult spinal deformity. Preventive strategies-including tethering, vertebral cement augmentation (VCA), hooks, trajectory modifications, and alignment optimization-have been proposed, but comparative evidence remains heterogeneous. The objective of this narrative review is to synthesize current biomechanical and clinical evidence, prioritize clinically meaningful end points (revision and PJF), and differentiate them from purely radiographic PJK. METHODS: Narrative review of biomechanical and clinical studies (cadaveric, finite-element, retrospective/prospective cohorts, and meta-analyses) evaluating tethering configurations (first/second level above the upper instrumented vertebra, crosslink anchoring), hooks, VCA, screw-trajectory/multilevel sublaminar stabilization, and alignment/frailty-informed selection. Dual screening and data extraction with consensus adjudication and qualitative synthesis were performed due to heterogeneity; no new meta-analysis was conducted. RESULTS: Posterior ligamentous augmentation (sublaminar/weave tethers) demonstrates the most consistent observed reduction in PJK and PJF, with the strongest signals at second level above the upper instrumented vertebra and when combined with age-adjusted alignment and patient-risk optimization. Complications are rare but include the risk of laminar/dural injury, band elongation, and increased implant cost and learning curve. VCA mainly addresses fracture-type PJF in low bone mineral density/elderly patients with device-specific risks; hooks may soften the proximal transition but have mixed clinical results. Biomechanics support moderate tether preload and careful anchor selection; artificial intelligence risk tools remain supplementary pending external validation. Evidence quality is limited by retrospective designs, variable definitions, and short-term to mid-term follow-up. CONCLUSION: Tethering is an effective adjunct-not a stand-alone solution-best used within a multimodal strategy (bone health, frailty, and age-adjusted alignment), with selective application of hooks or VCA based on failure mode risk. Standardized, prospective multicenter studies are necessary to determine long-term durability and comparative effectiveness.