title: Intraoperative blood loss during different stages of scoliosis surgery: A prospective study.
abstract: BACKGROUND
  There are a number of reasons for intraoperative blood loss during scoliosis surgery based on the type of approach, type of disease, osteopenia, and patient blood profile. However, no studies have investigated bleeding patterns according to the stage of the operation. The objective of this prospective study was to identify intraoperative bleeding patterns in different stages of scoliosis surgery.
  
  
  METHODS
  We prospectively analyzed the estimated blood loss (EBL) and operation time over four stages of scoliosis surgery in 44 patients. The patients were divided into three groups: adolescent idiopathic (group 1), spastic neuromuscular (group 2) and paralytic neuromuscular (group 3). The per-level EBL and operation times of the groups were compared on a stage-by-stage basis. The bone marrow density (BMD) of each patient was also obtained, and the relationship between per-level EBL and BMD was compared using regression analysis.
  
  
  RESULTS
  Per-level operation time was similar across all groups during surgical stage (p > 0.05). Per-level EBL was also similar during the dissection and bone-grafting states (p > 0.05). However, during the screw insertion stage, the per-level EBL was significantly higher in groups 2 and 3 compared to group 1 (p < 0.05). In the correction stage, per-level EBL was highest in group 3 (followed in order by groups 2 and 1) (p < 0.05). Preoperative BMD indicated that group 3 had the lowest bone quality, followed by groups 2 and 1 (in order), but the preoperative blood indices were similar in all groups. The differences in bleeding patterns in the screw insertion and correction stages were attributed to the poor bone quality of groups 2 and 3. Group 3 had the lowest bone quality, which caused loosening of the bone-screw interface during the correction stage and led to more bleeding. Patients with a T-score less than -2.5 showed a risk for high per-level EBL that was nine times higher than those with scores greater than -2.5 (p = 0.003).
  
  
  CONCLUSIONS
  We investigated the blood loss patterns during different stages of scoliosis surgery. Patients with poor BMD showed a risk of blood loss nine times higher than those with good BMD.
authors.affiliation: Scoliosis Research Institute, Department of Orthopedics, Korea University Guro Hospital, Seoul, Korea. spine@korea.ac.kr.
authors.forename: Hitesh N
authors.initials: HN
authors.lastname: Modi
authors.forename: Seung-Woo
authors.initials: SW
authors.lastname: Suh
authors.forename: Jae-Young
authors.initials: JY
authors.lastname: Hong
authors.forename: Sang-Heon
authors.initials: SH
authors.lastname: Song
authors.forename: Jae-Hyuk
authors.initials: JH
authors.lastname: Yang