Risk Factors of Postoperative Deep Wound Infections in Spinal Instrumentation, Analysis of 869 Cases

Aim: Postoperative deep wound infection is a major and devastating complication of spinal instrumentation. The aim of this study is to determine and evaluate the risk factors of postoperative deep wound infections in spinal instrumentation.

Materials and Methods: The study group includes 29 deep wound infection cases and age, sex, etiology matched 92 control cases among 869 cases with spinal instrumentation between 1989 and 2000. Cases were also grouped as early and late onset infection cases and their matched control groups. Recorded variables were age, sex, etiology, body mass index, year, duration and type of operation, implant material, number of segments involved, paraplegia, duration of preoperative hospitalization, duration of urinary catheter, history of smoking, polytrauma. Possible other factors not available for statistics were given 1 point each and cumulating was computed as a risk factor (diabetes mellitus, massive transfusion, long stay in ICU, pre and post long-lasting wound drainage, etc.). Chi-square, students-t, Mann-Whitney-U, ANOVA tests and logistic regression model were used for statistics.

Results and Conclusion: Logistic regression analysis revealed that the most important risk factors were staged surgery (p=0,005), preoperative hospitalization more than 4 days (p=0,042), polytrauma (p=0,012), paraplegia (p=0,039), having more than 1 point of other possible factors cumulating (p=0,005). Duration of urinary catheters (p=0,007), duration of operation (more than 210 minutes, p=0,022) and segments involved (segments between 4-7, p=0,006) were other risk factors in decreasing importance. Body mass index was a risk factor for adult patients (p=0.024). Staged spinal surgery increased risk of infection 6 times (risk is 10.5 times higher in early onset group), and hospitalization preoperatively more than 4 days increased risk of infection 6 times (risk is 5.3 times higher in early onset group). For late-onset infection group, only duration of urinary catheters and having more than 2 points of other possible factors was found to be important risk factors (p=0,009 and p=0,040 respectively).