Long-span four-rod salvage revision using existing bilateral dual iliac screw anchors for symptomatic rod fracture after adult spinal deformity surgery: a retrospective case series

Symptomatic rod fracture after long-segment fusion to the pelvis in adult spinal deformity (ASD) remains a clinically important cause of pain and revision surgery. This retrospective case series evaluated the mechanical and radiographic durability of a long-span four-rod salvage revision technique that uses pre-existing bilateral dual iliac screw anchors. Consecutive patients who underwent ASD surgery with fusion to the pelvis at a single university hospital from 2018 to 2025 were screened. Of 225 eligible patients, 24 were excluded because of death within 1 year (n = 2), loss to follow-up within 1 year (n = 18), or other reasons preventing regular radiographic follow-up (n = 4), leaving 201 analyzed patients with at least 1 year of follow-up. Index pelvic fixation consisted of bilateral dual iliac screws in 136 patients, single iliac screws in 34, and S2 alar-iliac screws in 31. The primary analysis focused on 52 unique patients with symptomatic bilateral rod fracture in the bilateral dual iliac screw cohort who were treated with posterior-only rod exchange and long-span four-rod reconstruction using the existing anchors. The mean interval from index surgery to rod fracture in the 52-patient salvage cohort was 1.4 ± 0.8 years. Clinical follow-up after salvage revision averaged 3.2 ± 1.1 years (range, 1.0–6.5 years). All 52 patients had standing radiographs and computed tomography at least 1 year after salvage revision. Subsequent radiographic follow-up remained available in 18, 16, 13, and 5 patients at >= 2, >= 3, >= 4, and >= 5 years, respectively. No recurrent rod fracture was identified on available imaging, and no symptomatic recurrent rod fracture, all-cause reoperation, death, or loss to clinical follow-up was recorded during post-salvage follow-up (0/52 for recurrent rod fracture or re-revision; exact 95% confidence interval, 0.0–6.8%). At final clinical follow-up, all patients were ambulatory and none had documented recurrent low back pain attributable to rod fracture. Computed tomography performed at least 1 year after salvage revision showed fusion at L4/5 in 52 patients and definite lumbosacral fusion at L5-S1 or across the posterior lumbosacral fusion mass in 41 patients; the remaining 11 patients were classified as having indeterminate lumbosacral fusion/nonunion. Screw loosening was observed in 28 patients, but no connector failure or rod deformation occurred. In selected patients with symptomatic bilateral rod fracture and pre-existing bilateral dual iliac screw anchors, long-span four-rod salvage revision was associated with encouraging mid-term mechanical and radiographic durability and favorable basic symptom status. The findings support this technique as a feasible salvage option, but the study does not establish clinical superiority or definitive clinical effectiveness, and longer follow-up with standardized imaging and validated patient-reported outcomes is needed.