Symptomatic Construct Failure after Metastatic Spine Tumor Surgery

STUDY DESIGN: Retrospective cohort study. PURPOSE: To evaluate the incidence and presentation of symptomatic failures (SFs) after metastatic spine tumor surgery (MSTS). To identify the associated risk factors. To categorize SFs based on the management in these patients. OVERVIEW OF LITERATURE: Few studies have reported on the incidence (1.9%–16%) and risk factors of SF after MSTS. It is unclear whether all SFs, occurring in MSTS-patients, result in revision surgery. METHODS: We conducted a retrospective analysis on 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 SF were defined as presentation before and after 3 months from index surgery, respectively. Univariate and multivariate models of competing risk regression analysis were designed to determine the risk factors for SF with death as a competing event. RESULTS: We observed 14 SFs (5.7%) in 246 patients; 10 (4.1%) underwent revision surgery. Median survival was 13.4 months. The mean age was 58.8 years (range, 21–87 years); 48.4% were women. The median time to failure was 5 months (range, 1–60 months). Patients with SF were categorized into three groups: (1) SF when the primary implant was revised (n=5, 35.7%); (2) peri-construct progression of disease requiring extension (n=5, 35.7%); and (3) SFs that did not warrant revision (n=4, 28.5%). Four patients (28.5%) presented with early failure. SF commonly occurred at the implant-bone interface (9/14) and all patients had a spinal instability neoplastic score (SINS) >7. Thirteen patients (92.8%) who developed failure had fixation spanning junctional regions. Multivariate competing risk regression showed that preoperative Eastern Cooperative Oncology Group score was a significant risk factor for implant failure (adjusted sub-hazard ratio, 7.0; 95% confidence interval, 1.63–30.07; p<0.0009). CONCLUSIONS: The incidence of SF (5.7%) was low in patients undergoing MSTS although these patients did not undergo spinal fusion. Preoperative ambulators involved a 7 times higher risk of failure than non-ambulators. Preoperative SINS >7 and fixations spanning junctional regions were associated with SF. Majority of construct failures occurred at the implant-bone interface.