LAUSR

Sola et al.’s paper is a well-written case report and a clear summary about the technical details of the minimally invasive, percutaneous cement discoplasty (PCD). As a member of the team that originally developed the PCD technique leaded by Peter Pal Varga, I am very happy to see the growing body of evidence supporting the method to help more and more suffering patients. Publication of clinical and basic scientific evidence is crucial in relation to any medical method especially in case of a new treatment possibility— this is the responsibility of the original developers as well as the surgeons who introduce the technique into their practice. Since our first report [1] and detailed technical description [2], a subsequent paper about the effect of PCD on spinal alignment and indirect foraminal decompression has been published by our team [3] and just recently, the results of the first in vitro biomechanical study about PCD was submitted for publication [4]. An independent case series has been also published by Willhuber et al. [5], and the topic has induced a real debate in the spine community [6–8]. In case of a surgical technique, the safety and effectiveness issues are strongly related to the proper indication and the accurate implementation. One of the strengths of Sola’s paper is that they clearly describe the clinical and radiological indication for PCD (long term, significant mechanical low back pain without neurology, resistant to conservative treatment and a significant vacuum sign in the disk space). In our experience, the careful investigation of this latest feature is one of the key elements of the good clinical outcome. Only spinal levels with significant vacuum phenomenon (pneumodisk in Sola’s words) can be treated with PCD technique. In case of a small vacuum sign, when more than half of the disk space is filled with degenerated disk tissue, the risk of early and late complications is high. The aim of the PCD is to stabilize the segment ceasing the vertical instability related to the advanced disk degeneration. We agree with Sola; the presence of vertical instability (he calls it accordion phenomenon i.e., a significant disk height variation between the standing and supine position in the presence of vacuum phenomenon) is the adequate radiological sign for the unstable segment and for the indication of PCD. One other important radiological feature in spinal levels suitable for PCD is the sclerosis of the vertebral endplates which provide solid contact surfaces for the PMMA spacer. Sole et al. give a proper description of the surgical technique with some considerable modification of the originally published one. They emphasized the importance of the proper positioning to improve the sagittal and coronal lumbar alignment, and we strongly agree with this point. The alignment correction what can be achieved with the positioning and can be stabilized with the PCD is one of the factors * Aron Lazary [email protected]