Predictors of hidden blood loss in ankylosing spondylitis patients receiving spinal deformity correction: osteotomy selection, bone density, and preoperative platelets.

PURPOSE: The objective of this study is to examine the factors that contribute to the occurrence of hidden blood loss (HBL) in individuals with ankylosing spondylitis (AS) who undergo posterior correction surgery.

METHODS

From October 2019 to September 2023, 186 patients with AS who were scheduled to have a posterior orthopedic correction surgery were included in our study. The patient's demographics, bone mineral density (BMD), operative time, hospital stay, intraoperative blood loss, blood transfusion volume, type of corrective osteotomies, the number of pedicle screws and fusion segments, drainage volume, correction angle of kyphosis and laboratory examinations, including preoperative hematocrit (HCT) and platelets (PLTpre), and preoperative fibrinogen (Fibpre), were collected retrospectively. The total blood loss (TBL) and HBL were calculated using the Gross equation. The statistical analysis was conducted utilizing SPSS 22.0. Pearson or Spearman correlation analyses were utilized to assess the potential risk factors associated with HBL. To identify the factors that affect HBL, multiple linear regression was utilized.

RESULTS

We reviewed 186 consecutive patients in our study. Potential risk factors of HBL included BMI (P = 0.050), BMD (P = 0.013), operative time (P = 0.002), the number of fusion segments (P = 0.001), the number of pedicle screws (P = 0.033), type of osteotomy (P < 0.001), correction angle (P = 0.005), and PLTpre (P = 0.079). Multiple linear regression analysis showed that BMD (P = 0.032), type of osteotomy (P = 0.019), and PLTpre (P = 0.034) were identified as risk factors for HBL.

CONCLUSION

HBL constitutes a significant proportion of perioperative blood loss in individuals with AS who received posterior correction surgery. BMD, type of osteotomy, and PLTpre are the most important risk factors which determine HBL. Therefore, surgeons should take into account these factors when considering surgical strategies for AS patients.

LEVEL OF EVIDENCE: Level III.