eTable 3. Specific causes of low back pain that need immediate treatment (red flags).

Disease	Findings	Further evaluation	Treatment
Fracture traumatic pathological osteoporotic	red flags (Table 1) acute or acutely exacerbated position-dependent pain pain and tenderness over spinous processes in some cases, iliocostal syndrome (12 th rib)	Imaging studies: plain films/MRI/CT scintigraphy for pacemaker wearers bone densitometry (T score) Laboratory testing: inflammatory parameters (CBC + CRP) osteoporosis parameters	Conservative: treatment of pain (strong analgesics if needed) basis therapy (osteoporosis) physiotherapy stabilizing, activating corset Surgical: vertebro-/kyphoplasty pedicle-screw-based instrumentation, possibly with ventral interposition (cage, vertebral body replacement) Prevention: regular intake of calcium, vitamin D, and biphosphonates exercise
Massive disc herniation	red flags (Table 1) mutiple radicular deficits bladder/bowel dysfunction saddle anesthesia (cauda equina syndrome)	MRI/CT electrophysiology: EMG, SSEP	Surgical: decompression with: sequestrectomy nucleotomy
Bacterial infection(spondylitis/ spondylodiscitis, epidural or paravertebral abscess)	red flags (Table 1) B symptoms pain swelling signs of instability pain on plantar flexion bed-shaking test (peritoneal irritation) neurologic deficit(s)	inflammatory parameters MRI/CT with contrast medium plain films in two planes biopsy for pathogen identification optional: scintigraphy, echocardiography	The indication for conservative vs. operative treatment (debridement, filling of defects, instrumentation) depends on: neurologic deficits stability abscess formation: intradiscal epidural paravertebral osseous muscular pathogen identification (specific/nonspecific)
Tumor	red flags (Table 1) B symptoms pain swelling signs of instability pain on plantar flexion bed-shaking test (peritoneal irritation) neurologic deficit(s)	Imaging studies - local at first, then staging studies to rule out instability (SINS): entire spinal axis CT of thorax and abdomen scintigraphy Laboratory tests: CBC, ESR, CRP, etc. tumor markers, Karnofsky score Tissue biopsy (CT- or MRI- guided, or open)	Neurologic deficit present: decompression and stabilization (dorsal or dorsoventral depending on overall findings) Neurologic deficit absent: discuss plan in interdisciplinary tumor board Conservative: treatment of pain (strong analgesics if needed) radiotherapy external stabilization (corset)

CBC, complete blood count; CRP, C-reactive protein; CT, computerized tomography; EMG, electromyography; ESR, erythrocyte sedimentation rate; MRI, magnetic resonance imaging; SINS, spinal instability in neoplastic disease; SSEP, somatosensory evoked potentials