Introduction: A minimally-invasive allograft-filled expandable meshed-bag containment system can be used in the lumbar spine for interbody fusion. Although graft subsidence is a key factor in selecting any interbody device, subsidence rate has not yet been reported with this device.
Methods: Consecutive adult patients that underwent 1- or 2-level interbody fusion with at least 1 year of radiographic follow-up were included in this study. Preoperative, postoperative, and final follow-up lumbar radiographs were analyzed to measure disc height at the anterior and posterior margins of the disc space, as well as the neuroforaminal height.
Results: Forty-one patients were identified, with a mean age of 63.4 years (SD ±11.8). A total of 61 levels were treated, with successful fusion observed in 54 levels (88.5%). The mean radiographic follow-up was 24.3 months (SD ±11.2). The mean disc height pre- and postoperatively was 6.9mm (SD ±3.2) and 10.1mm (SD ±2.9, p < 0.001), respectively. The mean disc height at final follow-up was 8.3mm (SD ±2.4). Average disc height subsidence was 1.8mm (SD ±1.7). Overall, average disc height increased by a net 1.3mm (SD ±2.5, p < 0.001). The mean neuroforaminal height pre- and postoperatively was 18.0mm (SD ±3.3) and 20.7mm (SD ±3.6, p < 0.001), respectively. The mean neuroforaminal height at final follow-up was 19.2mm (SD ±3.4). Average neuroforaminal height subsidence was 1.3mm (SD ±3.4). Overall, average neuroforaminal height increased by a net 1.7mm (SD ±2.8, p = 0.004). No significant difference in subsidence was observed between 1- and 2-level surgeries.
Conclusions: An expandable allograft containment system is a feasible alternative for lumbar interbody fusion. Due to its biologic and mechanical characteristics, the surgeon using such constructs should account for an anticipated average 18% loss of interbody height due to subsidence during the bony remodeling/fusion process.
Patient Care: This session will provide spine surgeons with valuable insight into the feasibility and long-term function of a novel interbody device, widening the field of available tools for patients with lumbar degenerative disease.
Learning Objectives: By the conclusion of this session, participants should be able to:
A. Recognize indications for a novel expandable interbody device
B. Anticipate graft subsidence with this device
3) Discuss these possibilities with patients
References: 1. Isaacs RE, Sembrano JN, Tohmeh AG, Group SDS. Two-Year Comparative Outcomes of MIS Lateral and MIS Transforaminal Interbody Fusion in the Treatment of Degenerative Spondylolisthesis: Part II: Radiographic Findings. Spine (Phila Pa 1976). 2016;41 Suppl 8:S133-144.
2. Kim CW, Doerr TM, Luna IY, et al. Minimally Invasive Transforaminal Lumbar Interbody Fusion Using Expandable Technology: A Clinical and Radiographic Analysis of 50 Patients. World neurosurgery. 2016;90:228-235.