Analysis of Short-Term versus Long-Term Readmission-Free Survival After Metastatic Spine Tumor Surgery.

BACKGROUND: Readmission-free survival (ReAFS) is a novel clinical and quality metric after metastatic spine tumor surgery (MSTS). We believe that factors influencing ReAFS after index MSTS vary based on time. We considered 2 time frames and defined short-term ReAFS as survival without an unplanned hospital readmission up to 90 days and long-term ReAFS as survival without unplanned hospital readmission up to 1 year after MSTS. METHODS: We retrospectively analyzed 266 patients who underwent MSTS between 2005 and 2016. All relevant oncologic, surgical and follow-up data were collected. Multivariate logistic regression analysis was used to analyze prognostic factors associated with higher probability of short-term ReAFS and long-term ReAFS. RESULTS: Multivariate analysis showed that Eastern Cooperative Oncology Group score ≤2 (P = 0.011), preoperative hemoglobin (Hb) level >12 g/dL (P = 0.008), ≤3 comorbidities (P = 0.052), shorter index length of stay ≤10 days (P = 0.007), and absence of neurologic/hematologic complications during index stay (P = 0.015) significantly increased the probability of short-term ReAFS, whereas preoperative Hb level >12 g/dL (P = 0.003) or tumor primaries with advanced treatment modalities such as breast (P = 0.012), hematologic (P = 0.006), prostate (P = 0.004), and renal/thyroid (P = 0.038) as opposed to aggressive lung tumor primaries were associated with significantly higher probability of long-term ReAFS. CONCLUSIONS: Patient and treatment factors predominantly influence ReAFS up to 90 days, whereas primary tumor-related factors alongside general health influence ReAFS beyond 90 days after index MSTS. Awareness of these factors may help oncologists and surgeons optimize treatment planning. The clinical significance of this study will continue to evolve, because we have been witnessing over the past decade that patients are becoming more involved in both their general health and understanding the natural history of the diseases that affect them.

Can Polyether Ether Ketone Dethrone Titanium as the Choice Implant Material for Metastatic Spine Tumor Surgery?

Instrumentation during metastatic spine tumor surgery (MSTS) provides stability to the spinal column in patients with pathologic fracture or iatrogenic instability produced while undergoing extensive decompression. Titanium is the current implant material of choice in MSTS. However, it hinders radiotherapy planning and generates artifacts, with magnetic resonance imaging and computed tomography scans used for postoperative evaluation of tumor recurrence and/or complications. The high modulus of elasticity of titanium (110 GPa) results in stress shielding, which may lead to construct failure at the bone-implant interface. Polyether ether ketone (PEEK), a thermoplastic polymer, is an emerging alternative to titanium for use in MSTS. The modulus of elasticity of PEEK (3.6 GPa) is close to that of cortical bone (17-21 GPa), resulting in minimal stress shielding. Its radiolucent and nonmetallic properties cause minimal interference with magnetic resonance imaging and computed tomography scans. PEEK also causes low-dose perturbation for radiotherapy planning. However, PEEK has reduced bioactivity with bone and lacks sufficient rigidity to be used as rods in MSTS. The reduced bioactivity of PEEK may be addressed by 1) surface modification (introducing porosity or bioactive coating with hydroxyapatite [HA] or titanium) and 2) forming composites with HA/titanium. The mechanical properties of PEEK may be improved by forming composites with HA or carbon fiber. Despite these modifications, all PEEK and PEEK-based implants are difficult to handle and contour intraoperatively. Our review provides a comprehensive overview of PEEK and modified PEEK implants, with a description of their properties and limitations, potentially serving as a basis for their future development and use in MSTS.