Spine Surgery
Principles of Spine Surgery
Candidates must understand spinal anatomy, biomechanics (three-column concept by Denis), and pathology (degenerative, traumatic, neoplastic, infectious). Know indications for surgery (neurologic deficit, instability, progressive deformity, intractable pain) and surgical approaches (anterior, posterior, combined).
Key Concepts
- Cervical spine: Jefferson fracture (C1 ring), hangman's fracture (C2 pars), odontoid fracture (types I, II, III). SCIWORA (spinal cord injury without radiographic abnormality) in children. Central cord syndrome (hyperextension in stenotic canal, upper > lower extremity weakness).
- Thoracolumbar spine: Denis three-column model: anterior (anterior longitudinal ligament, anterior annulus, anterior vertebral body), middle (posterior longitudinal ligament, posterior annulus, posterior vertebral body), posterior (posterior elements). Two or more column injury = unstable. TLICS (Thoracolumbar Injury Classification and Severity Score) guides treatment.
- Lumbar spine: Cauda equina syndrome (saddle anesthesia, bowel/bladder dysfunction, bilateral leg pain/weakness) is a surgical emergency. Spondylolisthesis (Meyerding grading). Degenerative disc disease.
- Spinal infection: Pyogenic spondylodiscitis (Staph aureus most common), TB spondylitis (Pott's disease, cold abscess, anterior wedging).
Traps
- Cauda equina: Urgent MRI and decompression within 24-48 hours to prevent permanent deficit.
- Cervical facet dislocation: Unilateral vs bilateral; bilateral is more unstable, often with complete cord injury.
- Odontoid fracture type II: Most common, high nonunion rate; treatment: halo vest or surgery (anterior screw or posterior fusion).
- SCIWORA: MRI may show cord edema; management is conservative with immobilization.
Worked Example
A 70-year-old male with known cervical stenosis falls, hitting his forehead. He has weakness in upper extremities more than lower, and bladder dysfunction. Diagnosis: central cord syndrome. Rule of thumb: Central cord syndrome often occurs with hyperextension in stenotic canal; upper limbs affected more due to lamination of corticospinal tract (arms medial). Early surgery (<24 hours) may improve outcomes, especially if neurological deficit.