Clinical Findings

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  A 54-year-old man presented with left anterior thigh pain and numbness lasting 1 month.

  
  
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  A grade IV weakness of the left quadriceps was identified.

  
  
• 
  

  Sagittal and axial MRI views were taken and identified a slightly upward-migrated disk herniation at the L3-L4 level, which was compressing the thecal sac and the exiting nerve root ( Fig. 18.40A,B ).

  
  
• 
  

  A CT scan also showed a soft disk herniation at the L3-L4 level ( Fig. 18.40C,D ).

Preoperative Plan

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  The skin entry point is selected by drawing various lines as shown in the axial MRI ( Fig. 18.41 ).

  
  
• 
  

  The distance from midline is ~12 cm.

  
  
• 
  

  The skin entry point is the same as the one used in cases of nonmigrated disk herniations, but its trajectory has a caudal to cranial angle.

Surgical Procedures

1. 
   

   Diskography is done after adequate needle positioning ( Fig. 18.42 ).

   
   
2. 
   

   The round-ended working cannula is positioned at the safe triangle. A cranial angle is needed to remove the foraminal upward-migrated disk fragment ( Fig. 18.43 ).