Utility of patient-specific rod instrumentation in deformity correction: Single institution experience

Introduction: Patient-specific instrumentation is an emerging technology with the promise of a better fit to patient anatomy. With the advent of deformity correction planning software, prefabricated rods can mitigate the need to bend rods in the operating room. Prefabricated rods allow the surgeon to provide a deformity correction closely in line with the surgical plan. Methods: A retrospective chart review was completed, and all patients with Medicrea UNiD rod were included. A minimum of 3 week follow up upright 36-inch lateral radiograph was necessary for analysis. Overall 21 patients had Medicrea UNiD rods placed; four were excluded (one for cervicothoracic fusion, three for incomplete follow up). Pelvic parameters were documented from the preoperative, surgical plan, and postoperative radiographs using Surgimap (Nemaris Inc, NY). The parameters for the rods were based on the surgical plan. Paired t-Tests were used to compare the preoperative, surgical plan, and postoperative pelvic parameters. Results: Average lumbar lordosis, pelvic tilt, sacral slope, and sagittal vertical axis in preoperative radiographs were 35.12°, 24.82°, 28.65°, and 65.65 mm, respectively. In postoperative imaging, lumbar lordosis, pelvic tilt, sacral slope, and sagittal vertical axis were 57.00°, 18.00°, 35.71°, and 21.59 mm, respectively. There was a statistically significant difference in pelvic tilt, sacral slope, lumbar lordosis, and sagittal vertical axis between the preoperative film and surgical plan (p < 0.001), whereas no statistically significant difference was found between the surgical plan and postoperative pelvic parameters (p > 0.05). Conclusions: Cases in which prefabricated rods were utilized demonstrated improved spinopelvic alignment. Additionally, there was no statistical difference between the surgical plan and postoperative imaging in terms of pelvic parameters. Future studies are needed to investigate the possible benefits of prefabricated rods.