Multiexpandable cage for minimally invasive posterior lumbar interbody fusion

Jeffrey D Coe,1 James F Zucherman,2 Donald W Kucharzyk,3 Kornelis A Poelstra,4 Larry E Miller,5 Sandeep Kunwar,6 1Silicon Valley Spine Institute, Campbell, 2San Francisco Orthopaedic Surgeons, San Francisco, CA, 3Orthopaedic Pediatric and Spine, Crown Point, IN, 4Department of Surgery, Sacred Heart Hospital on the Emerald Coast, Miramar Beach, FL, 5Miller Scientific Consulting, Inc., Asheville, NC, 6Bell Neuroscience Institute, Washington Hospital Healthcare System, Fremont, CA, USA Abstract: The increasing adoption of minimally invasive techniques for spine surgery in recent years has led to significant advancements in instrumentation for lumbar interbody fusion. Percutaneous pedicle screw fixation is now a mature technology, but the role of expandable cages is still evolving. The capability to deliver a multiexpandable interbody cage with a large footprint through a narrow surgical cannula represents a significant advancement in spinal surgery technology. The purpose of this report is to describe a multiexpandable lumbar interbody fusion cage, including implant characteristics, intended use, surgical technique, preclinical testing, and early clinical experience. Results to date suggest that the multiexpandable cage allows a less invasive approach to posterior/transforaminal lumbar interbody fusion surgery by minimizing iatrogenic risks associated with static or vertically expanding interbody prostheses while providing immediate vertebral height restoration, restoration of anatomic alignment, and excellent early-term clinical results. Keywords: degenerative disc disease, expandable, low back pain, Lun

Fusion mass bone quality after uninstrumented spinal fusion in older patients

Older people are at increased risk of non-union after spinal fusion, but little is known about the factors determining the quality of the fusion mass in this patient group. The aim of this study was to investigate fusion mass bone quality after uninstrumented spinal fusion and to evaluate if it could be improved by additional direct current (DC) electrical stimulation. A multicenter RCT compared 40 and 100 μA DC stimulation with a control group of uninstrumented posterolateral fusion in patients older than 60 years. This report comprised 80 patients who underwent DEXA scanning at the 1 year follow-up. The study population consisted of 29 men with a mean age of 72 years (range 62–85) and 51 women with a mean age of 72 years (range 61–84). All patients underwent DEXA scanning of their fusion mass. Fusion rate was assessed at the 2 year follow-up using thin slice CT scanning. DC electrical stimulation did not improve fusion mass bone quality. Smokers had lower fusion mass BMD (0.447 g/cm2) compared to non-smokers (0.517 g/cm2) (P = 0.086). Women had lower fusion mass BMD (0.460 g/cm2) compared to men (0.552 g/cm2) (P = 0.057). Using linear regression, fusion mass bone quality, measured as BMD, was significantly influenced by gender, age of the patient, bone density of the remaining part of the lumbar spine, amount of bone graft applied and smoking. Fusion rates in this cohort was 34% in the control group and 33 and 43% in the 40 and 100 μA groups, respectively (not significant). Patients classified as fused after 2 years had significant higher fusion mass BMD at 1 year (0.592 vs. 0.466 g/cm2, P = 0.0001). Fusion mass bone quality in older patients depends on several factors. Special attention should be given to women with manifest or borderline osteoporosis. Furthermore, bone graft materials with inductive potential might be considered for this patient population