INTRODUCTION: the use of interspinous instrumentation has been increasing in the last decade. However, in spite of the numerous papers seen in relevant scientific publications, there are very few references to an eventual disc height variation in the instrumented segment. OBJECTIVE: to certify eventual changes in disk height after interspinous instrumentation (DIAM - Cousin-Biotech - Medtronic Sofamor Danek Inc©). METHODS: the author evaluated 20 patients with degenerative lumbar disease and the following criteria: age >40 and <80; body mass index <40; pain visual analogue scale >6; Oswestry Inability Index >30; Zung Depression Rating Scale <39; Modified Somatic Perception Questionnaire <15; degenerative bone disease grade 2 and 3 according to Benzel classification and degenerative disk disease grade 3 and 4 according to Pfirmann classification. Using a special formula and a computer image program (Adobe Photoshop 9.0 CS2), side radiograms of the lumbar spine in orthostatic position and with 70% amplification were obtained pre-surgery and two years after surgery. RESULTS: after applying the mentioned formula, the results showed an increased global disk height average 1.53 mm, with a standard deviation of 1.09 mm and p=0.0002. However, there was a large increase (0.45 mm) in posterior disk height (p=0.0002) when compared with anterior measurement (p=0.001) pointing out a slight kyphosing effect related to the instrumentation. CONCLUSIONS: in Benzel grade 2 and 3 and Pfirmann grade 3 and 4 degenerative lumbar disease, the use of an interspinous system seemed to be able to increase disk height and to improve neural canal dimensions.
Spine; Intervertebral disk; Biomechanics; Orthopedic fixation devices; Lumbar vertebrae
