Interspinous posterior devices: What is the real surgical indication?

Abstract

Interspinous posterior device (IPD) is a term used to identify a relatively recent group of implants used to treat lumbar spinal degenerative disease. This kind of device is classified as part of the group of the dynamic stabilization systems of the spine. The concept of dynamic stabilization has been replaced by that of dynamic neutralization of hypermobility, with the intention of clarifying that the primary aim of this kind of system is not the preservation of the movement, but the dynamic neutralization of the segmental hypermobility which is at the root of the pathological condition. The indications for the implantation of an IPD are spinal stenosis and neurogenic claudication, assuming that its function is the enlargement of the neural foramen and the decompression of the roots forming the cauda equina in the central part of the vertebral canal. In the last 10 years, use of these implants has been very common but to date, no long-term clinical follow-up regarding clinical and radiological aspects are available. The high rate of reoperation, recurrence of symptoms and progression of degenerative changes is evident in the literature. If these devices are effectively a miracle cure for lumbar spinal stenosis, why do the utilization and implantation of IPD remain extremely controversial and should they be investigated further? Excluding the problems related to the high cost of the device, the main problem remains the pathological substrate on which the device is explicit in its action: the degenerative pathology of the spine.

Keywords: Interspinous distraction; Interspinous fusion device; Interspinous posterior device; Minimally invasive surgery; Motion preservation surgery; Spine surgery.

Figure 1

Dynamic X-ray. A: Patient treated for L3-L4 disc herniation (without instability at the dynamic X-rays) with an interspinous posterior device (IPD) implant. The Dynamic X-ray in extension showed a metameric instability at L3-L4 developed 1 year after an IPD implantation; B: Dynamic X-ray in flexion that showed an increase in L3-L4 slipping, developing a I° grade spondylolisthesis, due to the IPD implantation. The patient underwent revision surgery with removal of the IPD, decompressive laminectomy and L3-L4 stabilization with screws and rods.

Figure 2

Dislocation of the L3-L4 interspinous posterior device in a patient with double level implant. The patient underwent revision surgery with removal of both interspinous posterior devices followed by decompression and stabilization with screws and rods.