Outcomes and cost-minimization analysis of cement spacers versus expandable cages for posterior-only reconstruction of metastatic spine corpectomies.

BACKGROUND: Reconstruction of the thoracolumbar spine after tumor corpectomy can be accomplished using either an expandable metallic cage (EC) or a polymethylmethacrylate (PMMA) cement spacer. Few studies have compared the relative successes between these two forms of reconstructions in the management of metastatic spine disease (MSD). The purpose of this study was to compare both the outcomes and costs of EC and PMMA spacers in the treatment of MSD. We hypothesized that the rate of complications and revision surgery when using PMMA spacers to reconstruct the spine after corpectomy for MSD would be equivalent to use of an EC, with lower implant and operating room (OR) costs. METHODS: A single surgeon performed 65 vertebral corpectomies for MSD requiring anterior column reconstruction from 2007-2014. Charts were retrospectively reviewed and no patients were excluded. All resections were single-stage resections/reconstructions of the vertebral body through a posterior-only approach. Outcomes evaluated included perioperative complications, intraoperative time, postoperative survival, subsequent reoperations, and changes in radiographic spinal alignment. RESULTS: Thirty-six patients were treated with PMMA spacers; 29 were treated with EC. Baseline age, BMI, comorbidities, and disease severity as measured by Tokuhashi scores were equivalent between treatment groups. The cohorts had no significant differences in operative complications, blood loss, postoperative survival, number of subsequent reoperations, or changes in radiographic alignment. PMMA patients had a significantly shorter mean operative duration (328.6 vs. 241.1 min, P<0.001). Institutional implant cost savings were $4,355 favoring the PMMA cohort ($75 for cement vs. $5,000 for cage). Mean OR time savings were calculated to be $2,001 less for the PMMA cohort. Total cost minimization per PMMA case was thus $6,356, which was robust in 2-way sensitivity analyses varying both implant costs and time costs by 30%. CONCLUSIONS: In the largest series of posterior-only corpectomies for MSD reconstructed with PMMA, PMMA intervertebral spacers provided equivalent stability and longevity to EC, at a fraction of the cost. PMMA showed excellent durability while minimizing costs by $6,356 per case, an important consideration as reimbursement pressures increasingly influence surgical decision making.