Risk evaluation on aorta injury caused by misplacement of thoracic pedicle screws in the treatment of adolescent idiopathic scoliosis / 中华骨科杂志

ABSTRACT

Objective To evaluate the potential risk of aorta injury by simulating different lateral misplacement patterns of thoracic pedicle screws (TPS) in the treatment of adolescent idiopathic scoliosis (AIS).Methods From December 2010 to August 2011,50 AIS patients were admitted to our hospital,including 7 males and 43 females,aged from 13 to 18 years (average,15.3±2.6 years).All patients underwent axial magnetic resonance imaging (MRI) scans from T5 to T12.The left pedicle-aorta (LtP-Ao) angle and distance were measured on the axial MR images by the software of PACS Client.The lateral misplacement of pedicle screw was simulated with variable direction errors (10°,20°,30°) and different lengths of pedicle screw (30 mm,35 mm,40 mm).A total of nine patterns of lateral pedicle screw misplacement were set up,and a warning misplacement was defined as the mimic pedicle screw crossed the aorta.The percentages of warning misplacement were compared in each pattern of lateral pedicle screw misplacement and each level from T5 to T12.Correlation analysis was made between the percentages of warning misplacement and the direction errors as well as length of pedicle screw.Results The mean LtP-Ao angle increased from 34.3°±8.5° at T5 level to 45.7°±4.1° at T7 level,and then gradually decreased to 9.2°±5.6° at T12 level.The mean LtP-Ao distance increased from 28.2±7.3 mm at T5 level to 37.7±6.5 mm at T12 level.The percentages of warning misplacement were positive correlation with the direction errors and length of pedicle screw.The percentage of warning misplacement was higher at the T11 level.Conclusion The potential risk of aorta injury increases with enlarging of direction error and lengthening of thoracic pedicle screw,particularly at the T11 level.