Chronic Back Pain/Radiculopathy, Post-Operative

Kevin R. Moore, MD

DIFFERENTIAL DIAGNOSIS

Common

Failed Back Surgery Syndrome
Peridural Fibrosis
Intervertebral Disc Herniation, Recurrent
Degenerative Disc Disease
Instability
Post-Laminectomy Spondylolisthesis
Accelerated Degeneration

Less Common

Hardware Failure
Bone Graft Complications
Vertebroplasty Complications
Post-Operative Infection
Scoliosis, Degenerative

Rare but Important

Arachnoiditis, Lumbar
Arachnoiditis Ossificans, Lumbar

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Careful clinical exam will often distinguish radiculopathy from mechanical back pain, enabling a tailored differential list
Carefully consider hardware failure or indolent infection in post-operative implant patients presenting with chronic back pain

Helpful Clues for Common Diagnoses

Failed Back Surgery Syndrome
- Continued low back pain ± radicular pain following lumber spinal surgery
- Myriad etiologies manifest clinically as failed back surgery syndrome (FBSS)
- Look for specific abnormal imaging findings that may be addressed clinically
Peridural Fibrosis
- Scar formation within epidural space following lumbar spinal surgery
- Subset of FBSS
- T1 C+ FS MR imaging increases sensitivity for detecting peridural fibrosis and permits differentiation of fibrosis from disc herniation
Intervertebral Disc Herniation, Recurrent
- Focal extension of disc material beyond endplate margins at previously operated intervertebral disc level
- Subset of FBSS
- T1 C+ FS MR imaging increases sensitivity for detecting peridural fibrosis and permits differentiation of fibrosis from disc herniation
Degenerative Disc Disease
- Generalized and multifactorial process affecting discovertebral unit leading to biomechanical/morphologic alterations
- Imaging diagnosis of degenerative disc disease does not distinguish symptomatic from asymptomatic levels
  - May be asymptomatic or associated with back/neck pain ± radiculopathy
Instability
- Loss of spine motion segment stiffness, where applied force produces greater displacement than normal, producing pain/deformity
- Deformity increases with motion and increases over time
- Any spinal motion segment (comprised of two adjacent vertebrae, disc and connecting spinal ligaments) may be involved
  - Most common at post-operative levels, particularly if posterior elements removed by laminectomy
- AP translation at unstable level may vary from few mm to entire width of vertebral body
Post-Laminectomy Spondylolisthesis
- Loss of spine motion segment stiffness, where applied force produces greater displacement than normal, producing pain/deformity
- AP canal diameter narrows at subluxation level, distinguishing from spondylolysis where the AP canal diameter is increased
Accelerated Degeneration
- Synonyms include spinal “transitional degenerative syndrome” and “accelerated segmental degeneration”
- Degeneration of disc space/facets at level(s) adjacent to spinal fusion 2° to altered biomechanical forces → degenerative disc changes, disc herniation, and/or subluxation
- Identical changes occur at motion segments above or below congenital segmentation anomaly levels

Helpful Clues for Less Common Diagnoses

Hardware Failure
- Mechanical breakdown or malfunction of spinal fusion hardware
- Malposition of spinal fusion hardware without mechanical failure of implant
- Presentation symptoms range from indolent with chronic pain to calamitously with acute pain
Bone Graft Complications
- Abnormal alignment, position, or placement of graft or hardware ± associated neurologic deficit, instability, infection
  - Graft migration, graft displacement, or graft extrusion
- Cervical > thoracic > lumbar
Vertebroplasty Complications
- Complication types include
  - Extravasation of cement into spinal canal, neural foramen, or vertebral venous plexus
  - Pulmonary embolization of cement
  - Vertebral osteomyelitis
  - “Bounce back” fracture adjacent to vertebroplasty level
Post-Operative Infection
- Infectious sequelae following operative procedures
- Most frequently begins in intervertebral disc space => discitis, epidural abscess, subdural abscess, &/or paraspinal abscess
- Look for unexpected abnormal MR enhancement post-spinal surgery imaging
Scoliosis, Degenerative
- “De novo” scoliosis
- Lateral spinal curvature due to degenerative disc and facet disease
- Radiculopathy secondary to foraminal narrowing and nerve root compression
- Usually seen in older patients

Helpful Clues for Rare Diagnoses

Arachnoiditis, Lumbar
- Post-inflammatory adhesion and clumping of cauda equina nerve roots in thecal sac
- Imaging shows either absence of discrete nerve roots (“empty sac”) or peripheral displacement of nerve roots in thecal sac
Arachnoiditis Ossificans, Lumbar
- Intradural ossification associated with post-inflammatory adhesion and clumping of lumbar nerve roots
- Look for focal calcific density on CT or hyperintensity on T1WI and T2WI within lumbar nerve root aggregate