Pediatric Spondylolysis

Wiltse Classification of Spondylolysis/Listhesis

1. Dysplastic (Type I):

   • Congenital deficiency of the S1 dome or L5 arch.
   • The facets are often oriented axially/sagittally, allowing slip.
   • Highly associated with Spina Bifida Occulta.
   • High risk of progression to high-grade slip.

2. Isthmic (Type II):

   • The classic stress fracture lesion in the pars.
   • IIA: Lytic stress fracture. The bone fails under tension/shear. This is the common form in athletes.
   • IIB: Elongated pars. The bone "heals" with fibrous tissue that lengthens over time, allowing the body to slip forward. The pars is intact but attenuated.
   • IIC: Acute fracture. A traumatic event triggers the break (Rare).

3. Degenerative (Type III):

   • Adult instability.
   • L4/5 is most common level (vs L5/S1 for isthmic).
   • Due to facet joint and disc degeneration.
   • Rare in pediatric population.

4. Traumatic (Type IV):

   • High energy fracture (MVA, Fall).
   • Often associated with other spinal fractures.

5. Pathologic (Type V):

   • Tumor (Osteoid Osteoma? Metastasis?).
   • Infection (Osteomyelitis).

6. Iatrogenic (Type VI):

   • Post-surgical destabilization.
   • Removal of too much pars/facet during laminectomy.

Wiltse classification is the standard.

Meyerding Classification (Degree of Slip)

For Spondylolisthesis (which often accompanies lysis).

High grade slips (III-V) have significantly different biomechanics and surgical requirements (Dysplastic).

Stages of the Defect

1. Early (Stress Reaction): Marrow edema on MRI, no fracture line on CT.
2. Progressive (Lysis): Incomplete fracture.
3. Terminal (Defect): Complete bony gap.
   • Typically fibrous union.

Fibrous union is stable.

The Mainstay of Treatment

Success Rate: greater than 90%.

1. Rest: Cessation of sport (the "offending agent") for 3-6 months.
2. Analgesia: NSAIDs.
3. Bracing:
   • Boston Overlap Brace (Antilordotic).
   • Role: Symptom control and immobilization?
   • Protocol: Full time for 3-6 months vs Symptomatic wear.
   • Controversy: Does bracing actually heal the defect or just stop pain?
4. Physical Therapy:
   • Hamstring stretching (Crucial).
   • Core strengthening (Abdominals).
   • Pelvic tilt exercises.
   • Williams Flexion Exercises:
     • Pelvic Tilt.
     • Single Knee to Chest.
     • Double Knee to Chest.
     • Partial Sit-ups.
     • Hamstring stretch.
     • Hip Flexor stretch.
     • Squat.
   • Avoid hyperextension exercises (McKenzie) initially. Use flexion bias to open the neural foramen and unload the pars.

Return to sport: When pain-free and full ROM.

Fibrous union is an acceptable outcome.

Surgical Indications

1. Intractable Pain: Failure of 6-12 months of conservative care (Rest + Brace + PT).
2. Progression: Slip greater than 50% (Spondylolisthesis).
3. Neurology: Radiculopathy or deficit.

Note: Surgery for isolated lysis (no slip) is purely for pain relief.

Pars Repair (Buck's / Scott's)

Idea: Reconnect the broken bone without fusing the joint. Preserves motion. Indication: L1-L4 lysis (L5 is hard due to depth), No slip (Grade 0), Healthy disc (MRI).

Techniques:

1. Buck's Repair: Screw directly across the defect (Lag screw).
2. Scott's Wiring: Wire around transverse process to spinous process.
3. Pedicle Screw-Hook: Screw in pedicle, rod/hook on lamina. Compression.

Posterolateral Fusion (PLF)

Indication: L5 lysis (hard to repair directly), Spondylolisthesis, Disc degeneration.

Technique:

• Positioning: Prone on Jackson table to extend hips and lordose spine (reduces slip).
• Approach:
  • Midline: Allows decompression if needed.
  • Wiltse (Paraspinal): Muscle sparing. Direct access to transverse processes for fusion. Less bleeding.
• Instrumentaion:
  • Pedicle screws L5 to S1 (delta formation).
  • Reduction? Controversial. In situ fusion is safer (less nerve risk) but leaves deformity.
• Decortication:
  • Thorough exposure of transverse processes and sacral ala.
  • Decorticate transverse processes.
• Grafting:
  • Bone graft (Autograft/Allograft).
• Motion: Sacrifices L5-S1 motion (which is significant).

Fusion is more reliable than repair but has higher morbidity.