Assessment of pedicle screw malposition in uniplanar versus multiplanar spinal deformities in children

BACKGROUND: Spinal deformities can either be uniplanar or multiplanar. The current study aims to compare mal-positioned pedicle screw assessment on radiographs versus CT in children <12 years with multiplanar and uniplanar spinal deformities. METHODS: A cohort of 15 children, mean age 10.1 years, who underwent posterior spinal fusion using free-hand pedicle screw insertion for multiplanar (M) or uniplanar (U) deformities with post-operative radiograph and CT evaluation of 154 screws. The outcome measures included the assessment of malpositions detected on plain radiographs versus CT scans in U and M deformities. The overall breaches in post-operative plain radiographs and CT in each group were compared and analyzed by two independent observers. The mal-positioned screws were graded on extent of cortical breach on CT. Inter and intra-observer variability was calculated with Kappa(k) method. Sensitivity, Specificity and Positive Predictive Value (PPV) and Negative Predictive Value (NPV) were calculated by comparing breaches on radiographs versus CT considered the gold standard. RESULTS: In total,154 pedicle screws were analyzed, 65 in U group and 89 in M group. There were 23 (14.9%) malpositioned screws identified on plain radiographs and 43 (27.9%) on CT (p = 0.008). There were 17/154 (11.03%) Grade 1 breaches, 16/154 (10.38%) Grade 2 breaches and 10/154(6.49%) Grade III breaches. Among the 43 CT breaches, 12/65 (18.46%) were in U group, 31/89 (34.83%) were in M group (p = 0.013).The overall Sensitivity, Specificity and PPV of plain radiographs compared to CT in detecting malpositions were 32.56%, 91.89% and 60.87% respectively. CONCLUSIONS: There was a significant discrepancy in identification of pedicle screw malposition based on plain radiographic versus CT based assessment, more so in multiplanar deformities. The ability to detect a breach on plain radiographs is lesser in multiplanar versus uniplanar deformities.