The Aspen MIS Spinous Process Fusion System

*Tejas Karnati, Edwin Kulubya, Amir Goodarzi and Kee Kim*

### **Abstract**

The primary aim of this chapter will be to present an overview of the functionality and efficacy of the Aspen MIS spinous process fusion system, including a review of recent multicenter randomized data.

**Keywords:** Aspen, spinous process, posterior, lumbar, thoracic, spinal fusion, minimally invasive

### **1. Introduction**

Over the last couple of decades, there has been a growing trend in the use of minimally invasive techniques in spine surgery because of low rates of complications, reduced hospital length of stay, lower estimated blood loss, and minimal soft tissue trauma [1]. With the growing prevalence of low back pain and lumbar degenerative spine disease, spine surgeons have found the need to expand their surgical armamentarium in treating degenerative spondylosis and spondylolisthesis [2]. Current surgical techniques to fuse two vertebral levels include posterolateral fusion, posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), and extreme lateral interbody fusion associated with pedicle-screw fixation/instrumentation [3–7]; however, all these methods have drawbacks, such as increased operative time, risk of serious complications, and increased stiffness of the fused motion segment which may cause pathologic stresses at the adjacent levels [7]. These drawbacks of pedicle screw fixation (PSF) techniques have necessitated surgeons to explore novel and even more minimally invasive methods to achieve comparable levels of stability and fusion rates. Spinous process fixation (SPF)/interspinous process fixation (ISPF) achieved through the use of interspinous fusion devices (IFD) is not as widely used or known in the spine surgical community as PSF. Such devices aim to secure plates to the lateral aspects of two adjacent spinous processes thereby preventing motion at that segment. It is imperative that IFDs are not mistaken for similar other interspinous devices that offer "dynamic stabilization" such as X-STOP or DIAM etc. IFD placement has been successfully applied as an adjunct to posterolateral fusion and anterior fusion techniques and has shown similar rates of stability and fusion rates as PSF and has also been associated with improved or comparable patient-outcome scores [8].

In this chapter, we present the current evidence behind interspinous process fixation/fusion devices. We describe the primary biomechanical evidence and then present a discussion on clinical evidence of some case–control, case-series, and outcome studies. We then discuss the results of a recently completed randomized control trial of the Aspen® MIS Spinous Process Fusion System (Zimmer

Biomet Spine, Westminster, Colorado) and their implications in the use of IFDs in the future. At the end of the chapter, we describe in detail the components of the Aspen® MIS Spinous Process Fusion System and outline the basic surgical technique of placing this IFD successfully.
