title: Lateral Pressure and VAS Pain Score Analysis for the Lateral Lumbar Interbody Fusion Procedure.
abstract: BACKGROUND
  The lateral lumbar interbody fusion (LLIF) procedure is a minimally invasive procedure that has become widely utilized. The LLIF procedure typically involves bending the table to access the disc spaces of interest due to anatomical constraints. It is unknown if this bending process is painful or what pressures are exhibited on the downside part of the body. The goal of the study was to determine whether sex, height, weight, body mass index, bed angle, or positioning relative to the break of the bed affects the downside skin pressures and VAS pain scores in awake volunteers.
  
  
  METHODS
  Fifty-six volunteers were placed in the lateral decubitus position and pressure sensors were placed at the downside part of their anatomy (shoulder, T10 rib , iliac crest, and greater trochanter). The pressures were checked with the iliac crest or greater trochanter at 0, 10, 20, 30, 40 degree bed angles. VAS scores were checked when the iliac crest or greater trochanter were at the maximum bed break angles.
  
  
  RESULTS
  A significant positive association was found between increased bed angle and pressure at all five areas on the downside body locations (p<0.0001). The greatest pressures were located at the iliac crest and greater trochanter when these specific locations were centered over the break of the bed (p<0.0001). When the iliac crest was placed at maximal bed break, each unit increase in BMI increased the VAS pain by 0.13 (p<0.0001)and men had 1.96 (p=0.0009)higher VAS scores then women. When the greater trochanter was placed at the maximal bed break, each unit increase in BMI decreased VAS pain by 0.19 (p<0.0001) and women had 1.55 (p=0.0002)higher VAS pain scores then men.
  
  
  CONCLUSIONS
  In awake volunteers, the pressure at the iliac crest or greater trochanter at the break of the bed increases by increasing the bed angle. Women with a lower BMI had high VAS pain scores when their greater trochanter was at maximal bed break. Men with higher BMI had high VAS pain scores when their iliac crest was at maximal bed break. An awareness of the iliac crest or greater trochanter at the break of the bed should be considered to prevent pain and increased pressure based on the patient's sex and BMI.
authors.affiliation: Northwest Spine Research Foundation, Tualatin, OR.
authors.forename: Robert Louis
authors.initials: RL
authors.lastname: Tatsumi
keywords: lateral lumbar interbody fusion; lumbar pressure analysis; lumbar surgery complications; lumbar visual analog pain scores