[Study of modified subcutaneous lumbar spine index as a predictor for short-term effectiveness in transforaminal...

To explore the value of modified subcutaneous lumbar spine index (MSLSI) as a predictor for short-term effectiveness of transforaminal lumbar interbody fusion (TLIF) in treatment of lumbar degenerative disease (LDD).

Between February 2014 and October 2019, 450 patients who were diagnosed as LDD and received single-segment TLIF were included in the study. Based on the MSLSI measured by preoperative lumbar MRI, the patients were sorted from small to large and divided into three groups ( n=150). The MSLSI of group A was 0.11-0.49, group B was 0.49-0.73, and group C was 0.73-1.88. There was no significance in gender, age, disease duration, diagnosis, surgical segment, and improved Charlson comorbidity index between groups ( P>0.05). There were significant differences in the subcutaneous adipose depth of the L ₄ vertebral body and body mass index (BMI) between groups ( P<0.05). The operation time, intra-operative blood loss, length of incision, drainage tube placement time, drainage volume on the 1st day after operation, drainage volume on the 2nd day after operation, total drainage volume, antibiotic use time after operation, walking exercise time after operation, hospital stay, the incidences of surgical or non-surgical complications in the three groups were compared. Pearson correlation analysis was used to analyze the correlation between MSLSI and BMI, and partial correlation analysis was used to study the relationship between MSLSI, BMI, improved Charlson comorbidity index, subcutaneous adipose depth of the L ₄ vertebral body and complications. The Receiver Operating Characteristic (ROC) curve was used to evaluate the value of SLSI and MSLSI in predicting the occurrence of complications after TLIF in treatment of LDD.

There was no significant difference in operation time, length of incision, antibiotic use time after operation, walking exercise time after operation, drainage tube placement time, drainage volume on the 1st day after operation, drainage volume on the 2nd day after operation, and total drainage volume between groups ( P>0.05). The amount of intra-operative blood loss in group C was higher than that in groups A and B, and the hospital stay was longer than that in group B, with significant differences ( P<0.05). Surgical complications occurred in 22 cases (14.7%), 25 cases (16.7%), and 39 cases (26.0%) of groups A, B, and C, respectively. There was no significant difference in the incidence between groups ( χ ²=0.826, P=0.662). The incidences of nerve root injury and wound aseptic complications in group C were higher than those in groups A and B, and the incidence of nerve root injury in group B was higher than that in group A, with significant differences ( P<0.05). There were 13 cases (8.7%), 7 cases (4.7%), and 11 cases (7.3%) of non-surgical complications in groups A, B, and C, respectively, with no significant difference ( χ ²=2.128, P=0.345). There was no significant difference in the incidences of cardiovascular complications, urinary system complications, central system complications, and respiratory system complications between groups ( P>0.05). There was a correlation between MSLSI and BMI in 450 patients ( r=0.619, P=0.047). Partial correlation analysis showed that MSLSI was related to wound aseptic complications ( r=0.172, P=0.032), but not related to other surgical and non-surgical complications ( P>0.05). There was no correlation between BMI, improved Charlson comorbidity index, subcutaneous adipose depth of the L ₄ vertebral body and surgical and non-surgical complications ( P>0.05). ROC curve analysis showed that the area under ROC curve (AUC) of MSLSI was 0.673 (95%CI 0.546-0.761, P=0.025), and the AUC of SLSI was 0.582 (95%CI 0.472-0.693, P=0.191).

MSLSI can predict the short-term effectiveness of TLIF in treatment of LDD. Patients with high MSLSI suffer more intra-operative blood loss, longer hospital stay, and higher incidence of nerve root injury and postoperative incision complications.