The Incidence of Iliac Screw-Related Complications After Long Fusion Surgery in Patients with Adult Spinal Deformity.

STUDY DESIGN Retrospective study. OBJECTIVE To investigate the long-term clinical outcome and incidence of iliac screw-related complications in patients with adult spinal deformity (ASD). SUMMARY OF BACKGROUND DATA Rigid lumbosacral fixation is crucial to achieve optimal global alignment and successful long-term clinical outcomes. METHODS The data of eligible patients with ASD who underwent spinopelvic fixation using bilateral iliac screws with at least 5-year follow-up periods were retrospectively analyzed. Iliac screw loosening and rod breakage between the S1 and iliac (S1/IL) screws were defined as distal instability (DI). Demographic data, health-related quality of life scores, and spinopelvic parameters in the DI group were compared with those in the non-DI group. Sub-group analyses were performed between the cases with and without alignment change after rod fracture at S1/IL. RESULTS Of the 159 patients, the data of 110 patients (15 men, 95 women; mean age, 67.8 years) were analyzed. The follow-up rate was 69%. Forty-five (41%) patients showed DI (29 cases [26%] in screw loosening, 16 cases [15%] in rod breakage). Eight patients (7.3%) required revision surgery because of iliac screw-related complications. No significant differences were observed in the Oswestry Disability Index and Scoliosis Research Society questionnaire (revised) scores between the DI and non-DI groups. The patients with iliac screw loosening showed significantly greater values of preoperative pelvic incidence, pelvic tilt (PT) and postoperative PT, and T1-pelvic angle. In patients with rod breakage at S1/IL, five patients (31%) who had associated mechanical complications showed an alignment change between pre and post rod breakage. They showed significantly higher and lower rates of high-grade osteotomies and L5/S interbody fusion, respectively. CONCLUSION The incidence rate of iliac screw-related complications was relatively high. However, they had a little effect on sagittal alignment deterioration and there were few cases that required revision surgery.Level of Evidence: 4.