Thickness of Subcutaneous Fat as a Proxy for BMI in Non-ambulatory Patients With Neuromuscular Scoliosis Undergoing Posterior Spinal Fusion.

Background: Posterior spinal fusion in neuromuscular scoliosis patients carries a significant risk of postoperative surgical site infection (SSI). Body mass index has been associated with increased risk of surgical site infections, but it is difficult to obtain an accurate height of non-ambulatory children with severe neuromuscular scoliosis. Subcutaneous fat thickness has been associated with increased rates of surgical site infections in other surgeries; however, current literature has not elucidated a relationship between subcutaneous fat thickness and surgical site infections in this patient population.

Methods: A retrospective chart review analyzed non-ambulatory patients with neuromuscular scoliosis who underwent posterior spinal fusion. Patients were stratified into 3 groups (underweight, normal weight, and overweight/obese) based on BMI-for-age percentiles. Subcutaneous fat thickness was measured in both the sagittal and coronal planes at 24 landmarks. Comparisons of categorical data were analyzed using χ2 tests. Logistic regression analysis was used to isolate independent factors associated with surgical site infections.

Results: A total of 109 patients were analyzed. Thirty-four patients were underweight, 55 patients were normal weight, and 20 were overweight/obese. Twelve patients developed surgical site infections, with only 1 of them requiring an unplanned return to the operating room. Patients in the overweight/obese category had an increased risk of surgical site infection when compared with those in the normal weight and underweight categories (P=0.027). Of the 24 measurements taken, subcutaneous fat thickness to total distance from skin ratios at L2 spinous process (P=0.031), L3 spinous process (P=0.42), and averages of L2, L3, and L4 ratios (P=0.028) were all found to be associated with increased risk of surgical site infection.

Conclusion: In this study population of patients with neuromuscular scoliosis who underwent posterior spinal fusion, increased BMI was associated with increased risk of SSI. Furthermore, 3 radiographic measurements of subcutaneous fat thickness associated with a higher risk of surgical site infections were identified. This knowledge could contribute to devising preoperative strategies to mitigate surgical risk and postoperative complications.

Level of evidence: Level III-a retrospective study.