Paraplegic patients have defective wound healing for sore below the level of spinal lesion. Defect of vascularization of the healing zone certainly participate to this effect. Therefore, this study want to measure, in a clinical settings, the interface pressure (e.g. the pressure between the patient body and the surface he/she is lying on) to assess the correlation between mechanical stress in term of pressure applied over time and tissue oxygenation which represent micro-vascular function. The aim of this clinical trial is to correlate the variations of pressure intensities and changes in micro-vascularization. The measure are recorded when paraplegic patient came into the hospital for pressure ulcer related surgery. The patient is laying on his/her mattress on top of a flexible pressure mapping device. The micro-vascularization parameters are measured at the area displaying the peak pressure a few minutes after the beginning of the pressure interface recording and one hour later at the same area. The data generated during this monocentric study will help to achieve a better understanding of the relation between pressure and micro-vascularization. In the mid term, it will provide a better and more patient adapted pressure ulcer prevention.