Spine surgery is increasingly common for degenerative disease, trauma, infection, and tumors. Imaging of the postoperative spine is often challenging but essential to distinguish expected changes from complications.
📍 Modalities Used
1. X-ray
- Quick, inexpensive
- Evaluates: alignment, hardware position, fusion progress
- Dynamic (flexion–extension) → instability
2. CT
- Best for bone and hardware
- Detects: fusion, hardware loosening/fracture, bony stenosis
- Metal artifact reduction algorithms helpful
3. MRI (Modality of choice for soft tissues)
- Excellent for disc, cord, nerves, marrow, infection
- Metal artifact reduction (MAVRIC, SEMAC) sequences improve quality
- Post-contrast MRI differentiates scar vs recurrent disease
🔎 Normal Postoperative Findings
- Granulation tissue → enhances homogeneously
- Epidural fibrosis → enhancing scar around dura
- Bone graft material → variable signal, matures over time
- Mild postoperative edema and hematoma may be present
🚨 Complications on Imaging
1. Recurrent Disc Herniation vs Postoperative Scar
- Both cause nerve root compression
- Recurrent disc: non-enhancing, T2 hyperintense, mass effect
- Scar tissue: avidly and homogeneously enhances after contrast
2. Hardware Complications
- Malpositioned screws/rods/plates
- Loosening → lucency around screws on CT
- Breakage or migration
3. Infection
- Discitis–osteomyelitis: marrow edema, endplate destruction, disc enhancement
- Epidural/paraspinal abscess: T2 bright, rim-enhancing, mass effect on thecal sac
4. Pseudomeningocele / CSF Leak
- CSF-intensity fluid collection communicating with thecal sac
- May cause headaches, pseudomeningocele mass effect
5. Hematoma / Seroma
- Early postoperative complication
- Variable signal, non-enhancing or thin rim enhancement
- May compress cord/nerve roots
6. Arachnoiditis
- Clumped or adherent nerve roots in the thecal sac
- “Empty thecal sac” or “central conglomeration” appearance
🧠 Teaching Points
- MRI is gold standard for postoperative soft tissue and neural assessment.
- CT is best for hardware and fusion evaluation.
- Always correlate with surgical history, timing, and symptoms.
- Key differentiation: Recurrent disc = no enhancement, Scar = enhances.
