Predicting metalwork following posterior fixation of thoracolumbar fractures

OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Elective removal of metalwork following Lisfranc injury fixation: Results of a national consensus survey of practice

No consensus exists regarding whether metalwork should be routinely removed following fixation of a Lisfranc injury. When metalwork is removed, notable variation in the timing of surgery is reported in current literature. With the support of the British Orthopaedic Foot & Ankle Society (BOFAS) and the Orthopaedic Trauma Society (OTS) an online 10-question survey was distributed and completed by a total of 205 consultant surgeons in the UK between April-June 2020. Excluding the 20 consultant responses from a regional pilot survey, 185 responses were used to form the main analysis. Over one third (69/183, 37.7%) of surgeons reported they routinely remove metalwork following Lisfranc injury fixation at a median time of 6 months post fixation (interquartile range 4-10). The two most commonly chosen reasons for removal of metalwork were 'to optimise physiological function' and 'to reduce the risk of broken metalwork and risk of making subsequent surgery more difficult' (55/78 responses, 70.5%). Over two thirds of survey respondents (126/184, 68.5%) expressed interest to participate in a randomised controlled trial to compare outcomes of metalwork retention versus removal following Lisfranc injury fixation. Community clinical equipoise exists nationally regarding routine metalwork removal following Lisfranc injury fixation. Considering the paucity of literature, the current survey supports the development of a randomised controlled trial to establish the risks and benefits of metalwork retention versus removal, and would be of value to foot & ankle and trauma surgeons in the UK.