ACCURACY OF USING COMPUTED-TOMOGRAPHY TO IDENTIFY PEDICLE SCREW PLACEMENT IN CADAVERIC HUMAN LUMBAR SPINE

Study Design. Utility of using computed tomography to predict pedicle screw misplacement. Objective. This study defines the sensitivity and specificity of predicting pedicle screw placement by experienced clini cians using a CT scan image. Summary of Background Data. In clinical a nd research settings, the method most commonly used to evaluate pedicl e screws placement has been computed tomography, However, no current l iterature describes the accuracy of this method of evaluating screw pl acement. Method. Cobalt-chrome and titanium alloy pedicle screws of id entical size were placed in six cadaveric human lumbar spine. Wide lam inectomy was performed to allow complete visualization of the pedicles . Three consecutive lumbar levels were instrumented in each spine, giv ing 36 pedicle screw placements to identify. The instrumented spines w ere imaged, and four orthopaedic spine surgeons and a musculoskeletal radiologist were asked to read the images to identify the accuracy of screw placement within the pedicles. Results. The sensitivity rate of identifying a misplaced screw was 67 +/- 6% for cobalt-chrome screws c ompared with 86 +/- 5% for titanium screws (P < 0.005). The specificit y rates of radiographic diagnosis of misplaced pedicle screws were 66 +/- 10% for cobalt-chrome screws and 88 +/- 8% for titanium screws (P < 0.005). Similarly, a statistically significant difference was found in the sensitivity rates of identifying screws placed correctly in the pedicle: 70 +/- 10% for cobalt-chrome screws versus 89 +/- 8% for tit anium screws (P < 0.005). Overall accuracy rates were 68 +/- 7% for co balt chrome screws versus 87 +/- 3% for titanium screws (P < 0.002). C onclusion. Reliance on the computed tomography scan data alone in dete rmining accuracy of pedicle screws can lead to inaccuracies in both cl inical and research conditions.