The correlation between intra-operative estimated blood loss and bone mineral density during minimally invasive posterior lumbar interbody fusion

Abstract

Objective To investigate the correlation between intra-operative estimated blood loss (EBL) and bone mineral density (BMD) during minimally invasive posterior lumbar interbody fusio,n (PLIF).Methods In this retrospective case control study,61 consecutive patients suffering from mono-segment low back disorders were treated by minimally invasive PLIF from 2005 to 2010.The patients' parameters including age,gender,operation time (OT),BMD,EBL,prothrombin time were collected.According to BMD of the lumbar spine,all the patients were divided into two groups: the normal group and the osteopenia group.The differences of the EBL and other parameters between the two groups were analyzed by student's t test and Pearson's Chi-square test.Besides,the correlation between intra-operative EBL and each of the other parameters except for gender were analyzed among all the patients.To detect the relationship between intra-operative EBL and gender,patients were divided by gender and the intra-operative EBL of two groups were examined by student's t test.Finally,a probable model about intra-operative EBL and the other parameters was proposed using stepwise linear regression analysis.Results The average intra-operative EBL of the normal group and the osteopenia group were (346.41±199.53) ml and (552.62±300.21) ml,respectively.The difference was significant.However,the other parameters including post-operative EBL had no significant differences between two groups.A negative correlation between intra-operative EBL and BMD (r=-0.37,P=0.035)and a positive correlation between intra-operative EBL and OT (r=0.34,P=0.008) were found.But none of the other parameters was correlated with intra-operative EBL.The similar result was observed by the stepwise linear regression analysis.Intra-operative EBL was influenced by BMD and OT under the control of this research,and the relationship might be formulated with the equation,EBL=-0.63×BMD+1.46×OT.Conclusion BMD should be considered an important predictor of intra-operative EBL in PLIF. Key words: Lumbar vertebrae; Bone density; Blood loss, surgical; Spinal fusion