Development and evaluation of a simple CT-based DXA triage score for osteoporosis in candidates for lumbar spine surgery

Retrospective cohort study. Requiring DXA testing before lumbar spine surgery can delay surgical scheduling and time to surgery and may be unnecessary for many candidates. We aimed to develop and evaluate a simple, bedside-calculable score using routinely available preoperative variables to decide, at the time of surgical evaluation, which patients should have a DXA ordered (prioritized) versus which patients may safely defer DXA (DXA triage). In a single-center cohort ( n = 182), osteoporosis was defined according to ISCD site criteria as a T-score ≤ − 2.5 at the lumbar spine, femoral neck, or total hip. Mean L1–L4 HU was derived from preoperative lumbar CT. A 4-item additive score (sex, age, BMI, and mean L1–L4 HU; range 0–15) was constructed using clinically interpretable cutpoints informed by multivariable logistic regression. Discrimination, calibration, and clinical utility were evaluated with bootstrap optimism correction. The cohort had a mean age of 72.3 ± 8.3 years and included 106 women (58.2%). DXA-defined osteoporosis was present in 61/182 (33.5%). Hip-only osteoporosis predominated (44/182, 24.2%), whereas lumbar-involved osteoporosis occurred in 17/182 (9.3%). Mean L1–L4 HU correlated with the DXA lowest site T-score ( r = 0.516, p < 0.001). The point-based score demonstrated strong discrimination for osteoporosis (AUC 0.826), outperforming HU alone (AUC 0.722) and approaching a multivariable FRAX-lite model (age, sex, BMI, HU; AUC 0.810); optimism-corrected AUCs were similar (score 0.827; HU 0.726; FRAX-lite 0.796). Using Score ≥ 4 as a triage rule (order DXA if ≥ 4) selected 130/182 (71.4%) patients for DXA, reducing DXA utilization by 28.6% versus DXA-for-all, with sensitivity 96.7% (59/61) and specificity 41.3%. The two missed cases occurred exclusively in men and represented hip-only osteoporosis. Decision curve analysis supported score-based triage as a practical DXA prioritization strategy across clinically plausible threshold probabilities. A simple CT-enabled 4-item score can support DXA ordering decisions at surgical evaluation, prioritizing DXA for higher-risk patients and reducing unnecessary testing while preserving high sensitivity for DXA-defined osteoporosis. However, DXA should not be deferred when hip-predominant risk is suspected, particularly in men.