title: The incidence of nerve root injury by high-speed drill can be reduced by chilled saline irrigation in a rabbit model.
abstract: OBJECTIVE
  We aimed to evaluate the temperature around the nerve root during drilling of the lamina and to determine whether irrigation during drilling can reduce the chance of nerve root injury.
  
  
  METHODS
  Lumbar nerve roots were exposed to frictional heat by high-speed drilling of the lamina in a live rabbit model, with saline (room temperature (RT) or chilled saline) or without saline (control) irrigation. We measured temperatures surrounding the nerve root and made histological evaluations.
  
  
  RESULTS
  In the control group, the mean temperature around the nerve root was 52.0°C (38.0°C to 75.5°C) after 60 seconds of drilling, and nerve root injuries were found in one out of 13 (7.7%) immediately, three out of 14 (21.4%) at three days, and 11 out of 25 (44.0%) at seven days post-operatively. While the RT group showed a significantly lower temperature around the nerve root compared with the control group (mean 46.5°C; 34.5°C to 66.9°C, p < 0.001), RT saline failed to significantly reduce the incidence of nerve root injury (ten out of 26; 38.5%; odds ratio (OR) 0.96; 95% confidence interval (CI) 0.516 to 1.785; p = 0.563). However, chilled saline irrigation resulted in a significantly lower temperature than the control group (mean 39.0°C; 35.3°C to 52.3°C; p < 0.001) and a lower rate of nerve root injury (two out of 21; 9.5%, OR 0.13; 95% CI 0.02 to 0.703, p = 0.010).
  
  
  CONCLUSIONS
  Frictional heat caused by a high-speed drill can cause histological nerve root injury. Chilled saline irrigation had a more prominent effect than RT in reducing the incidence of the thermal injury during extended drilling. Cite this article:Bone Joint J2017;99-B:554-60.
authors.affiliation: Osaka City University Graduate School of Medicine, 1-5-7, Asahimachi, Abenoku, Osaka 545-8585, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Tamai
authors.affiliation: Osaka City University Graduate School of Medicine, 1-5-7, Asahimachi, Abenoku, Osaka 545-8585, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Suzuki
authors.affiliation: Osaka City University Graduate School of Medicine, 1-5-7, Asahimachi, Abenoku, Osaka 545-8585, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: Osaka City University Graduate School of Medicine, 1-5-7, Asahimachi, Abenoku, Osaka 545-8585, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Akhgar
authors.affiliation: Osaka City University Graduate School of Medicine, 1-5-7, Asahimachi, Abenoku, Osaka 545-8585, Japan.
authors.forename: M S
authors.initials: MS
authors.lastname: Rahmani
authors.affiliation: Osaka City University Graduate School of Medicine, 1-5-7, Asahimachi, Abenoku, Osaka 545-8585, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hayashi
authors.affiliation: Osaka City University Graduate School of Medicine, 1-5-7, Asahimachi, Abenoku, Osaka 545-8585, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ohyama
authors.affiliation: Osaka City University Graduate School of Medicine, 1-5-7, Asahimachi, Abenoku, Osaka 545-8585, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D007036:Hypothermia, Induced / Q000379:methods; D007796:Laminectomy / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods; D008297:Male; D059348:Peripheral Nerve Injuries / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D011817:Rabbits; D066148:Spinal Cord Dorsal Horn / Q000473:pathology / Q000601:surgery*; D013126:Spinal Nerve Roots / Q000293:injuries* / Q000473:pathology; D013696:Temperature; D007507:Therapeutic Irrigation / Q000379:methods*
keywords: C5 plasy; Comorbidity; High speed drill; Irrigation; Nerve root injury; Thermal injury