A nerve-to-implant distance as a novel predictor for lateral femoral cutaneous nerve injuries after anterior subcutaneous pelvic internal fixation

Although anterior subcutaneous pelvic internal fixation is a valuable tool for the reduction and fixation of unstable pelvic ring injuries, lateral femoral cutaneous nerve irritation by the implant is the most common complication. This study aimed to investigate the association between the nerve-to-implant distance and the postoperative lateral femoral cutaneous nerve symptom. Patients who underwent anterior subcutaneous pelvic internal fixation between 2016 and 2019 were retrospectively analyzed. Lateral femoral cutaneous nerve status was defined as follows: not identified, nerve-to-implant distance <13 mm, and ≥13 mm. The proportion of patients who experienced postoperative nerve disorders was compared using the nerve status. Nerve-to-implant distances were compared using the presence or absence of postoperative lateral femoral cutaneous nerve disorders. The predictive value of a nerve-to-implant distance of 13 mm for postoperative nerve disorders was assessed. Overall, 26 lateral femoral cutaneous nerves were included. Ten patients had postoperative nerve disorders, of which seven had an nerve-to-implant distance <13 mm, while the other three occurred in patients whose nerves were not identified. A nerve-to-implant distance ≥13 mm was significantly associated with a decreased risk of postoperative nerve disorder compared to a nerve-to-implant distance <13 mm (p = 0.017). A nerve-to-implant distance ≥13 mm had a perfect sensitivity (100%) and modest specificity (58.3%). Nerve-to-implant distance was ≥13 mm. Nerve disorders were frequently observed when the nerve-to-implant distance was <13 mm or the nerve was not identified intraoperatively. Efforts to identify the lateral femoral cutaneous nerve may be useful to avoid internal fixation-related nerve disorders.