Asymptomatic Construct Failure after Metastatic Spine Tumor Surgery: A New Entity or a Continuum with Symptomatic Failure?

Abstract

Study Design: Retrospective cohort study.Purpose: To study the incidence, onset, underlying mechanism, clinical course, and factors leading to asymptomatic construct failure(AsCF) after metastatic spinal tumor surgery (MSTS).Overview of Literature: The reported incidence rates for implant and/or construct failure after MSTS are low (1.9%–16%) andbased on clinical presentations and revisions required for symptomatic failures (SFs). AsCF after MSTS has not been reported.Methods: We conducted a retrospective analysis of 288 patients (246 for final analysis) who underwent MSTS between 2005–2015.Data collected were demographics and peri/postoperative clinical and radiological features. Early and late radiological AsCF weredefined as presentation before and after 3 months, respectively.We analyzed patients with AsCF for risk factors and survival durationby performing competing risk regression analyses where AsCF was the event of interest, with SF and death as competing events.Results: We observed AsCF in 41/246 patients (16.7%). The mean time to onset of AsCF after MSTS was 2 months (range, 1–9months). Median survival of patients with AsCF was 20 and 41 months for early and late failures, respectively. Early AsCF accountedfor 80.5% of cases, while late AsCF accounted for 19.5%. The commonest radiologically detectable AsCF mechanismwas angulardeformity (increase in kyphus) in 29 patients. Increasing age (p <0.02) and primary breast (13/41, 31.7%) (p <0.01) tumors were associatedwith higher AsCF rates. There was a non-significant trend towards AsCF in patients with a spinal instability neoplastic score ≥7,instrumentation across junctional regions, and construct lengths of 6–9 levels. None of the patients with AsCF underwent revisionsurgery.Conclusions: AsCF after MSTS is a distinct entity. Most patients with early AsCF did not require intervention. Patients who survivedand maintained ambulation for longer periods had late failure. Increasing age and tumors with a betterprognosis have a higher likelihoodof developing AsCF. AsCF is not necessarily an indication for aggressive/urgent intervention