Retrospective multicenter assessment of rod fracture after anterior column realignment in minimally invasive adult spinal deformity correction

Background Anterior column realignment (ACR) was developed as a minimally invasive method for treating sagittal imbalance. However, rod fracture (RF) rates associated with ACR are not known. Our objective was to assess the rate of and risk factors for RF following ACR in deformity correction surgery. Methods We conducted a retrospective multicenter review of patients with adult spinal deformity (ASD) who underwent ACR for deformity correction. ASD was defined as coronal Cobb angle ≥20°, pelvic incidence–lumbar lordosis >10°, sagittal vertical axis ≥5 cm, pelvic tilt ≥25°, or thoracic kyphosis ≥60°. Inclusion criteria were ASD, age >18 years, use of ACR, and development of RF or full radiographs obtained at least 1 year after surgery that did not demonstrate RF. Results Ninety patients were identified, with mean follow-up of 2.3 ± 1.4 years (age, 64.1 ± 9.4; 54 [60%] women). The most common ACR location was L3/4 (42 cases; 47%). Mean fusion length was 7.5 ± 3.6 levels. Four (4.4%) of 90 patients developed RF within 12 months of surgery. RF occurred adjacent to ACR in all cases; RF was not associated with focal correction ( P = 0.49), rod material ( P = 0.8), degree of correction ( P > 0.07), or interbody at L5/S1 ( P = 0.06). RF was associated with longer fusion constructs in univariate ( P = 0.002) and multivariate ( P =  0.03) analyses. Conclusions RF occurred in 4.4% of patients with ASD who underwent ACR with a minimum of 1-year follow-up. RF was not associated with focal correction but appears to be associated with global correction and extent of fixation.