• Alan H Daniels, J Mason DePasse, Wesley Durand, D Kojo Hamilton, Peter Passias, Han Jo Kim, Themistocles Protopsaltis, Daniel B C Reid, Virginie LaFage, Justin S Smith, Christopher Shaffrey, Munish Gupta, Eric Klineberg, Frank Schwab, Doug Burton, Shay Bess, Christopher Ames, Robert A Hart, and International Spine Study Group.
• Department of Orthopaedics, Division of Spine Surgery, Alpert Medical School of Brown University, Providence, Rhode Island, USA. Electronic address: alan_daniels@brown.edu.
• World Neurosurg. 2018 Sep 1; 117: e530-e537.

BackgroundRod fracture occurs with delayed fusion or pseudarthrosis after adult spinal deformity (ASD) surgery. Rod fracture after apparent radiographic fusion has not been previously investigated.MethodsPatients with ASD in a multicenter database were assessed for radiographic fusion by a committee of 3 spinal deformity surgeons. Fusions were rated as bilaterally fused (A), unilaterally fused (B), partially fused (C), or not fused (D). Patients with grade A or B fusion and 2-year follow-up were included. Patients with radiographic fusion were evaluated for subsequent rod fracture. Adjusted analyses were conducted with multiple logistic regression, using backwards-variable selection to a threshold of P < 0.2, to assess for associated factors.ResultsOf 402 patients with radiographically apparent solid fusion, 9.5% (38) subsequently suffered a broken rod. On multivariate analysis, greater rates of rod fracture were seen among patients of age group 60-69 years (vs. 18-49), body mass index 30-34 and 35+ (vs. <25), stainless-steel rods (vs. titanium), patients with rods ≤5.5 mm (vs. 6.35 mm), and patients with Charlson score 0 (vs. 3+). Of the 38 patients with rod fractures, 18 (47.4%) presented with worsened pain, and 8 (21.1%) required revision at minimum 2-year follow-up.ConclusionsRod fracture occurred in 9.5% of patients with apparently solid radiographic fusion after ASD surgery. Advanced age, obesity, small diameter rods (5.5 mm), osteotomy, and lower comorbidity burden were significantly associated with rod fracture. Nearly one-half of these patients noted worsening pain, and 21.1% required revision surgery. Instrumentation failure may occur and may be symptomatic even in the setting of apparent fusion on plain radiographs.Copyright © 2018 Elsevier Inc. All rights reserved.

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