Pelvic Fixation in Adult Spinal Deformity: Complications, Controversies, and Future Directions

Study Design: Narrative Review. Objective: Pelvic fixation is a crucial technique in modern adult spinal deformity surgery, yet complications and failure rates remain high. Significant controversy exists regarding the type and number of points of pelvic fixation needed but remains poorly defined. The purpose of this article is to summarize current literature on pelvic fixation techniques, complications, and outcomes, discuss controversies, and suggest future directions. Methods: A literature search was conducted in PubMed for publications written in English with full text available from January 2000 to January 2022 using the following search terms: “spinopelvic fixation”, “sacroiliac fixation”, “iliac screw”, “S2AI screw” and “complications” or “outcomes” together with “adult spinal deformity” and “scoliosis”. Results: Twenty-two articles were identified as describing complications/outcomes comparing pelvic fixation techniques (S2AI vs iliac; n = 6) or as reporting on a single technique (n = 16). The main categories of pelvic fixation complications were mechanical, pseudarthrosis, wound infection, sacroiliac joint pain, and revision. Four studies found lower complication rates for S2AI screws vs iliac screws. Descriptive studies reported high rates of complications for both S2AI and iliac screws. The frequency of complications was as follows: screw fracture 1.9%-9%, screw loosening 2%-65%, L5-S1 pseudarthrosis 6%-23.9%, sacroiliac joint pain 3.2%-52.5%, revision rate 2.4%-50%. Conclusions: Pelvic fixation with either S2AI or iliac screws provides significant stability to constructs that extend to the sacrum. Further study is needed to characterize the number of points of pelvic fixation needed and clarify the role of pelvic fixation in causation or treatment of sacroiliac joint pain.