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182. Catastrophic acute failure of pelvic fixation in adult spinal deformity requiring revision surgery: a multicenter review of incidence, failure mechanisms, and risk factors
Abstract   Peer reviewed

182. Catastrophic acute failure of pelvic fixation in adult spinal deformity requiring revision surgery: a multicenter review of incidence, failure mechanisms, and risk factors

Christopher T. Martin, David W. Polly, Kenneth Holton, Benjamin D. Elder, Jeremy L. Fogelson, Anthony L. Mikula, Christopher Kleck, Evalina L. Burger, David Calabrese, David Ou-Yang, …
The spine journal, Vol.21(9), pp.S92-S92
09/2021
DOI: 10.1016/j.spinee.2021.05.389

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Abstract

BACKGROUND CONTEXT There are few prior reports of acute failures of pelvic instrumentation. PURPOSE To report the incidence and risk factors for an under-reported cause of early revision surgery in adult spinal deformity. STUDY DESIGN/SETTING Multicenter retrospective cohort. METHODS Thirteen academic medical centers performed a retrospective review of 18 months of consecutive adult spinal fusions extending 3 or more levels which included new pelvic screws placed at the time of surgery. Acute pelvic fixation failure was defined as occurring within 6 months of the index surgery and requiring surgical revision. A univariate analysis was conducted to compare those patients with and without failure. In an attempt to control for confounders, a subsequent multivariate analysis was conducted which included all variables from the univariate results with a p>0.1. RESULTS Failure occurred in 38 of 779 cases (5%), and consisted of either slippage of the rods or displacement of the set screws from the screw tulip head, screw shaft fracture, screw loosening, and/or resultant kyphotic fracture of the sacrum. Reported revision strategies utilized placing new pelvic fixation, and/or multiple rod constructs spanning to the pelvis. Two patients revised with <4 rods to the pelvis sustained a second acute failure, but no secondary failures occurred when at least 4 rods were used. In the univariate analysis, the magnitude of surgical correction was higher in the failure cohort (change in lumbar lordosis, and presence of a 3-column osteotomy, each <0.05). A 3-column osteotomy located at the lower lumbar segments between L4-S1, as opposed to correction at higher levels, particularly increased the risk (OR of 2.7, P=0.03). Use of pelvic screws <8.5mm in diameter increased the likelihood of failure (p<0.05). In the multivariate analysis, male gender, increasing BMI, increasing number of levels fused, and increasing preop pelvic incidence were each associated with increased risk of failure (p<0.05 for each). In addition, either a previously solid L5-S1 fusion or the use of an interbody device at L5-S1 at the index surgery significantly decreased the risk of acute pelvic fixation failure (OR of 0.33, p=0.017). CONCLUSIONS Acute catastrophic failures involved large magnitude surgical corrections, particularly those with 3-column osteotomies located from L4-S1, and likely resulted from high mechanical strain on the pelvic instrumentation, with resultant associated rod/screw failure and/or kyphotic sacral fractures. Patients with large magnitude surgical corrections should have anterior structural support placed at the most caudal motion segment, and may benefit from multiple rods connecting to more than 2 pelvic fixation points. If failure occurs, salvage with a minimum of 4 rods and 4 pelvic fixation points can be successful.

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