Lumbar micro instability is a diffuse problem mostly in elderly population. Interspinous processes devices (IPDs) have been introduced in the clinical practice for relieving the dynamic compression on the nerve roots due to instability. First-generation IPDs did not achieve bone fusion so their good immediate postoperative results did not last in the long term. More recently, a new version of IPD, Bacfuse®, has been introduced with the aim of achieving postoperative fusion. We started using this new device in 2015. We investigated prospectively the long-term results of a series of 41 patients with small-to-moderate lumbar instability. In 29 of them the IPD was placed as an adjunct to decompressive surgery whilst in 12 patients it was implemented as a stand-alone technique. Immediate post-operative results showed significant clinical improvement in all cases. This improvement was still present in 32 of them at the last follow-up, 2.5 to 4 years following surgery. The dynamics of clinical symptoms did not change after two years of observation, a fact that indicates that no changes are to be expected afterward. Spinal fusion was obtained in more than 2/3 of the patients and not surprisingly was correlated with better clinical results. Excessive body weight appeared to be a negative factor for achieving both spinal fusion and good results. Bacfuse® seems to be a very good surgical tool for patients bearing small to moderate lumbar instability whether or not submitted to direct decompressive surgery.