Association of diffuse idiopathic skeletal hyperostosis with postoperative outcomes following surgery for degenerative lumbar spine disease.

OBJECTIVE: To determine whether diffuse idiopathic skeletal hyperostosis (DISH), particularly when extending into the lumbar spine (L-DISH), is associated with postoperative outcomes after surgery for degenerative lumbar disease. METHODS: Multiple bibliographic, trial, and Japanese literature databases were searched from inception through June 30, 2026. Comparative DISH or L-DISH studies and within-DISH prognostic or surgical-strategy studies were eligible. Decompression and short-segment interbody fusion evidence were analyzed separately, and overlapping cohorts were resolved for each outcome. Study-specific adjusted estimates were prioritized for inference. Crude risk ratios (RRs) from unadjusted event counts were retained only as secondary, illustrative k = 2 syntheses. Risk of bias was assessed at the result level, and certainty was graded by outcome. RESULTS: Fifteen reports representing 12 independent studies, all retrospective and from Japan, were included. Adjusted study-specific associations for reoperation pointed toward higher risk with DISH/L-DISH after short-segment fusion (hazard ratio [HR], 5.46; 95% confidence interval [CI], 2.25-13.30), mixed lumbar procedures (HR, 2.049; 95% CI, 1.199-3.503), and decompression (HR, 3.37; 95% CI, 1.31-8.69), but effect measures, adjustment sets, and time horizons differed and were not pooled. Secondary crude syntheses contained only 2 cohorts each: decompression RR, 2.50 (95% CI, 1.53-4.08), and fusion RR, 3.93 (95% CI, 2.00-7.70). Modified Hartung-Knapp intervals were 0.10-60.12 and 0.05-310.05, respectively. Radiographic nonunion or pseudarthrosis estimates differed markedly (RR, 12.44; 95% CI, 4.39-35.32; and RR, 1.75; 95% CI, 1.07-2.88) and were not pooled. Certainty was very low. CONCLUSION: Primary adjusted associations and supportive crude observational estimates were directionally consistent with greater reoperation risk, but sparse data, incomplete confounding control, time-dependent outcome handling, and an exclusively Japanese evidence base make the magnitude uncertain and limit transportability. DISH/L-DISH may be regarded as a possible risk marker, not a causal determinant or a basis for a universal operative strategy. PROSPERO NUMBER: CRD420261454437.