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Fat Thickness as a Risk Factor for Infection in Lumbar Spine Surgery
Abstract:
Body mass index does not account for body mass distribution. This study tested the hypothesis that subcutaneous fat thickness is a better indicator than body mass index of the risk of surgical site infection in lumbar spine procedures performed through a midline posterior approach. Charts were reviewed for previously identified risk factors for surgical site infection (age, diabetes, smoking, obesity, albumin level, multilevel procedures, previous surgery, and operative time) in 149 adult patients who underwent lumbar spine procedures through a midline posterior approach. Subcutaneous fat thickness was measured with a novel automated technique. Regression analysis was used to determine associations between risk factors and fat thickness with surgical site infection. In the study group, 15 surgical site infections occurred (10.1%). Bivariate analysis showed a significant association between surgical site infection and body mass index (P=.01), obesity (P=.02), and fat thickness (P=.002). With multivariate analysis, body mass index and obesity did not show significance, but fat thickness remained significant (P=.026). For every 1-mm thickness of subcutaneous fat there was a 6% (odds ratio, 1.06; 95% confidence interval, 1.02-1.10) increase in the odds of surgical site infection, and patients with fat thickness of greater than 50 mm had a 4-fold increase in the odds of surgical site infection compared with those with fat thickness of less than 50 mm. Body mass index and fat thickness were moderately correlated (r2=0.44). These results confirm the hypothesis that local subcutaneous fat thickness is a better indicator than body mass index of the risk of surgical site infection in lumbar spine procedures. [Orthopedics. 2016; 39(6):e1124-e1128.].
Insights
Subcutaneous fat thickness, not body mass index, better predicts surgical site infection risk in lumbar spine surgery. Increased fat thickness significantly elevates infection odds, highlighting its importance for patient outcomes.
Area of Science:
- Orthopedics
- Surgical Outcomes
- Medical Imaging
Background:
- Body mass index (BMI) is a common metric but does not reflect body fat distribution.
- Surgical site infections (SSIs) are a significant complication in lumbar spine procedures.
- Understanding risk factors for SSIs is crucial for improving patient safety and surgical success.
Purpose of the Study:
- To test the hypothesis that subcutaneous fat thickness is a superior predictor of SSI risk compared to BMI in lumbar spine surgery.
- To investigate the association between local fat thickness and SSI development.
- To compare the predictive value of fat thickness against established SSI risk factors.
Main Methods:
- Retrospective review of 149 adult patients undergoing lumbar spine procedures via a midline posterior approach.
- Analysis of known SSI risk factors including age, diabetes, smoking, obesity, albumin, procedure complexity, and operative time.
- Measurement of subcutaneous fat thickness using a novel automated technique.
Main Results:
- Fifteen SSIs occurred (10.1%) in the study cohort.
- Bivariate analysis revealed significant associations between SSI and BMI, obesity, and fat thickness.
- Multivariate analysis confirmed subcutaneous fat thickness as a significant independent predictor of SSI (P=.026), while BMI and obesity lost significance.
Conclusions:
- Local subcutaneous fat thickness is a more accurate indicator of SSI risk than BMI in lumbar spine surgery.
- Each 1-mm increase in fat thickness correlated with a 6% rise in SSI odds.
- Patients with fat thickness >50 mm faced a fourfold increased risk of SSI compared to those with <50 mm.
