Abstract

Purpose
The purpose of the study was to investigate the effect of obesity on the accuracy of percutaneous pedicle screw placement.
Materials and Methods
We performed a retrospective analysis on the first 89 patients undergoing minimally invasive lumbar fusion with percutaneous pedicle screw placements for the treatment of degenerative lumbar spinal disorder. Based on patient’s body mass index (BMI), patients were divided into 3 groups: group 1 – normal weight (BMI<25, 38 patients, 157 screws); group 2 – overweight (25≤BMI<30, 29 patients, 124 screws); group 3 – obese (BMI≥30, 22 patients, 89 screws). Using postoperative computed tomography (CT) scans, the position of placed screws to the pedicle or anterior body perforation was evaluated using the following grading method: Grade A, completely in the range without pedicle cortex violation; Grade B, pedicle wall violation<2 mm; Grade C, pedicle wall violation 2 to 4 mm; and Grade D, pedicle wall violation>4 mm.
Results
Among the 370 pedicle screws, 308 screws (83%) were perfectly placed within the pedicle. Among the 62 misplaced screws, 45 screws were grade B pedicle breaches (73%, 45/62), and 45 screws were misplaced in lateral direction (73%, 45/62). 36 screws (10%) perforated the anterior vertebral cortex. Twenty eight screws were misplaced in overweight group, 12 screws in obese group, and 22 screws in normal weight group. With the number of screws available, subgroup analysis did not reveal a significant difference in the grade (p=0.10) or the direction (p=0.97) of pedicle breaches among groups.
Conclusion
Our data suggest that obesity does not affect the accuracy of percutaneous pedicle screw placement. We do not hesitate or deny the surgery because of patient’s heavy body habitus, which seems to be a apparent benefit of minimally invasive spinal surgery.

• Keywords: Obesity, Percutaneous pedicle screw placement, Minimal invasive spine surgery, Lumbar spine