Predicting metalwork following posterior fixation of thoracolumbar fractures.

Abstract

Surgical fusion through posterior instrumentation and pedicle screw placement is a long established method for stabilising traumatic spinal fractures. Post-surgical complications include infection and metal work failure, the most common aetiology of which is pedicle screw fracture. Metal work failure rates vary from 15% to 60%. Research relating to factors which predict metal work failure in post-traumatic thoracolumbar spinal fixation is lacking. This study aimed to identify potential risk factors for metalwork failure in patients who had posterior fixation for traumatic thoracolumbar spine fractures. This retrospective cohort analysis was conducted by interrogating the hospital database for neurosurgical post-traumatic thoracolumbar fixation cases between 2015 and 2018 with at least 2 years follow up. Data was collected through electronic medical notes and PACS. Nineteen different patient factors (gender, age, mechanism of injury, presence of concomitant injury spinal or extra-spinal injury, pedicle cross-sectional area, pedicle cancellous bone density, pedicle total bone density, vertebral body bone density, erector spinae muscle density and lumbar spine subcutaneous fat thickness, Charlson comorbidity index, fracture location, surgical approach, long/short segment fixation, whether decompression was done, whether the index level was fixed, and presence of wound infection) were compared. We identified 92 patients with 97 operations, and 9 cases of metal work failure. Two factors were statistically significantly associated with metal work failure: Post-operative wound infection (p = 0.029) and lumbar spine fat thickness (p = 0.024). The relative risk calculated in patients with a wound infection was 3.76. Lumbar spine fat thickness was on average 11.9 mm greater than patients not experiencing metal work failure. This study has identified two factors associated with increased rates of metal work failure: Post-operative wound infection and lumbar spine fat thickness. When assessing surgical candidates these factors may be incorporated into surgical planning.