title: L5 spinal nerve injury caused by misplacement of outwardly-inserted S1 pedicle screws.
abstract: OBJECTIVE
  To evaluate L5 nerve root injuries caused by outwardly misplaced S1 pedicle screws. Pedicle screws remain the criterion standard for fixation of L5-S1 to correct lumbosacral instability. When inserting S1 pedicle screws, it is possible to injure the L5 nerve root if screws are inserted outwardly and the tip of the screw perforates the anterior cortex of the sacrum. Despite this risk, to our knowledge this type of injury has never been reported as a case series.
  
  
  METHODS
  We experienced 2 cases of L5 nerve root injury caused by outwardly-inserted S1 pedicle screws. In both cases, bilateral S1 pedicle screws were inserted outwardly using a free-hand technique, and on one side, screws induced severe pain by impinging on an L5 root. Computed tomography after the selective rootgraphy of the injured nerve showed the nerve compressed laterally by screw threads in Case 1 and crushed between the screw threads and the sacral body in Case 2.
  
  
  RESULTS
  In both cases, leg pain disappeared immediately after the infiltration of the nerve with lidocaine, but symptoms recurred within a few days in Case 1 and within an hour in Case 2. Conservative treatment of three spinal nerve infiltrations was effective in Case 1, but reinsertion of the rogue screw was necessary in Case 2.
  
  
  CONCLUSIONS
  Surgeons should recognize that lateral inclination of S1 pedicle screws can cause L5 nerve root injury, which may require reinsertion of the screw, especially in cases where insertion is difficult because of overlapping surrounding muscle or bony tissue.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Inoue
authors.forename: Gen
authors.initials: G
authors.lastname: Inoue
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Ozawa
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miyagi
authors.forename: Hiroto
authors.initials: H
authors.lastname: Kamoda
authors.forename: Tetsuhiro
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Miyako
authors.initials: M
authors.lastname: Suzuki
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sakuma
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Oikawa
authors.forename: Kazuyo
authors.initials: K
authors.lastname: Yamauchi
authors.forename: Sumihisa
authors.initials: S
authors.lastname: Orita
authors.forename: Masashi
authors.initials: M
authors.lastname: Takaso
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Toyone
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
authors.forename: Seiji
authors.initials: S
authors.lastname: Ohtori
mesh_terms: D000368:Aged; D001863:Bone Screws / Q000009:adverse effects*; D006801:Humans; D008161:Lumbosacral Region / Q000293:injuries*; D008297:Male; D008875:Middle Aged; D012086:Reoperation; D013123:Spinal Fusion / Q000009:adverse effects* / Q000295:instrumentation; D013127:Spinal Nerves / Q000293:injuries*