Model notes: Defaults reflect cohort averages (BMI 27 kg/m², CRP 1.2 mg/L, blood loss 200 mL, no comorbidities). BMI contributes only for units above 25. Logistic regression coefficients: BMI OR 1.07/unit above 25; CRP OR 1.01/mg/L; diabetes type 2 OR 2.08; CHF OR 4.65; prior lumbar surgery OR 1.99; dural tear OR 1.77; blood loss OR 1.01/100 mL. Intercept calibrated to ~3% cohort prevalence. ¹

Surgical complexity — lumbar procedures: ²

Category I — Lumbar microdiscectomy · Lumbar posterior decompression · Lumbar posterior instrumentation (pedicle screws) · Lumbar kyphoplasty · Lumbar vertebroplasty

Category II — Posterior lumbar interbody fusion (PLIF) · Transforaminal lumbar interbody fusion (TLIF) · Sacral-pelvic instrumentation

Category III — Lateral lumbar interbody fusion (LLIF) · Anterior lumbar interbody fusion (ALIF) · Lumbar disc prosthesis · Lumbar hemi-/corpectomy

Farshad M, Aichmair A, Gerber C, Bauer DE. Classification of perioperative complications in spine surgery. The Spine Journal 20 (2020) 730–736. DOI: 10.1016/j.spinee.2019.12.013

A prospective classification framework for perioperative complications in spine surgery, developed to enable standardised reporting and outcome comparison across institutions and procedure types. The system uses four independent axes — therapeutic consequence, neurological impact, procedure complexity, and complication aetiology — which together capture the full clinical weight of any perioperative event. The grading of therapeutic consequence (A–E) was validated against hospital length of stay, showing strongly significant stepwise differences across grades (p<.001).