BACKGROUND: Proximal junctional kyphosis and failure are common complications after adult spinal deformity correction, often leading to reoperation. While global sagittal alignment has been studied extensively, the role of proportional radiographic parameters remains unclear.
METHODS: PubMed, Embase, Web of Science, and the Cochrane Library were searched (2000-2025). Eligible studies included adults undergoing ASD fusion of four or more levels with reported PJK incidence and key sagittal parameters including LDI, lumbar lordosis, TK, sagittal vertical axis, PI, and pelvic tilt. Risk of bias was assessed using the Newcastle-Ottawa Scale. Pooled weighted mean differences with 95% confidence intervals were calculated using fixed-effects models.
RESULTS: Of 1046 records screened, 27 studies were included qualitatively and five studies (802 patients; follow-up 24-72 months) in quantitative synthesis. PJK incidence ranged from 22 to 38%. Patients who developed PJK demonstrated significantly greater postoperative TK (WMD = + 4.9°, p < 0.00001), lower preoperative and postoperative LL (WMD = - 4.5°, p = 0.0002; WMD = - 3.9°, p < 0.0001), higher preoperative SVA (WMD = + 17.2 mm, p < 0.0001), and unexpectedly lower PI (WMD = - 2.4°, p = 0.009). Differences in absolute LDI values, PT, and postoperative SVA were not statistically significant.
CONCLUSIONS: Greater postoperative TK, reduced LL, elevated preoperative SVA, and lower PI were consistently associated with the development of PJK. These findings underscore the importance of pelvic incidence-based alignment strategies, appropriate restoration and distribution of lumbar lordosis, morphology-aware thoracic contouring, and mechanical transition techniques to mitigate junctional failure following adult spinal deformity correction.
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