Multi-Expandable Cages for Minimally Invasive Posterior/Tranforaminal Lumbar Interbody Fusion—A Preliminary Report

Presented at SMISS Annual Forum 2016
By Jeffrey Coe MD
With Donald Kucharzyk DO, Kornelis Poelstra MD, PhD, Joshua Ammerman MD, Sandeep Kunwar MD,

Disclosures: Jeffrey Coe MD Donald Kucharzyk DO B; Life Spine, SeaSpine, Orthofix/Stryker, Medicrea, Biomet/Zimmer, Benvenue, Precision Spine, SurGenTec. C; Life Spine, Orthofix/Stryker, Precision Spine, Zyga, Biomet/Zimmer. F; Precision Spine, Kornelis Poelstra MD, PhD None, Joshua Ammerman MD A; Benvenue Medical., Sandeep Kunwar MD B; Benvenue Medical.,

Introduction

A significant drawback of posterior/transforaminal lumbar interbody fusion (P/TLIF) is the smaller-sized cage (compared to ALIF/LLIF) that must be used because of the narrow access corridor. This shortcoming often limits placement of bone graft, potentially increasing risk of pseudarthrosis or cage subsidence/migration. Furthermore, degenerative conditions such as disc collapse and spondylolisthesis can make insertion of a static posterior cage challenging. 

Aims/Objectives

The purpose of this study is to evaluate early clinical outcomes with a multi-dimensional expandable ~25 mm diameter footprint interbody device (MDE-IBD) that may be placed without impaction via a 6-8 mm cannula. 

Methods

A medical chart review study to evaluate a multi-center series having MDE-IBD P/TLIF was initiated by the authors and is currently ongoing. It was hypothesized that patients would demonstrate decreased pain and improved radiological findings.
All MDE-IBD were placed using minimally-invasive P/TLIF. 

Results

To date, 30 patients (15 males; 30-81 years) with 6 month follow-up are included. Principal diagnoses included spinal stenosis (n=26), spondylolisthesis (n=18), radiculopathy (n=18) and herniated disc (n=13). Eighteen (60%) patients had a single-level procedure while the rest had multiple-level fusion, with the MDE-IBD placed at two levels or in conjunction with other fusion techniques. Complications included one small dural tear without CSF leak which required no repair; no neurologic or other complications were seen. At 6 months, back and leg pain were reduced, with MCID achieved by 90% of patients. In 11 patients with available ODI scores, 7 (64%) were improved >12 points. Radiculopathy was resolved in 21/22 patients and neurologic deficit in 13/17 (+3 improving) patients who presented with these conditions preoperatively. At the first postoperative visit (~2 weeks), 29 MDE-IBD levels showed improvements of 4.8±2.9 mm for average disc height and 4.5±8.7 degrees for local disc angle. Mean (±SD) change at 3 and 6 months, respectively, for average disc height were 4.2±2.7 mm and 5.6±3.5 mm, and for local disc angle were 3.6±3.7 degrees and 3.8±5.0 degrees. Regional lumbar lordosis was preserved (±10°) or improved (>10°) in 24/28 (86%) and 22/25 (88%) patients at 3 and 6 months, respectively. 

Conclusions

A key advantage of a multi-expandable cage is that an anterior-sized cage footprint can be delivered through a narrow posterior surgical corridor. Early experience with MDE-IBD in minimally-invasive P/TLIF is demonstrating encouraging outcomes, including absence of nerve retraction injuries and restoration of disc height and local disc angle along with preservation or restoration of regional lumbar lordosis.