Medially misplaced pedicle screws in patients without neurological deficits following scoliosis surgery: to observe or to remove?

PURPOSE: This study investigated whether pedicle screws medially misplaced into the spinal canal without neurological complications should be removed or not. METHODS: A total of 86 patients with scoliosis that underwent spinal fusion using 988 pedicle screws were retrospectively reviewed after a minimum follow-up of 2 years. The inclusion criteria were: (1) patients without outstanding problems during the insertion of pedicle screws, (2) patients without neurological deficits either intraoperatively or postoperatively, and (3) patients that had all implants removed after bone union upon the request of the patient. Medial perforations were evaluated using immediate postoperative helical CT images and classified into three grades: grade 1 (0-2 mm), grade 2 (2-4 mm), and grade 3 (over 4 mm). All unexpected events were recorded at the time of removal. RESULTS: CT images obtained 2 years postoperatively exhibited neither loosening of screws nor pseudoarthrosis in all patients. CSF leakage from screw holes were recognized in 3 of 87 medially misplaced screws (3.4 %). There was no CSF leakage in grade 1 (35 screws), one CSF leakage (2.5 %) in grade 2 (40 screws), and two (16.7 %) in grade 3 (12 screws). No neurological abnormalities occurred either intraoperatively or postoperatively. CONCLUSION: This study indicated that screws medially misplaced at a distance greater than 2 mm, especially 4 mm, may be a cause of negative effects on the neural structure and should be removed during the early phase of the postoperative period, even among patients without postoperative neurological abnormalities.