The invention relates to a specific immobilisation device for use in rescue services, pre-hospital medical emergencies services and patient transport services, characterised in that it allows the complete "en bloc" immobilisation of the pelvic area and affected lower limb of the patient in cases of femoral neck fracture. The device can also be used - with equal efficiency and effectiveness - as a specific immobilisation device in cases of pelvic fracture, femoral fracture, knee fracture, and fracture of the tibia proximal to the knee. The device comprises the following elements: (i) a rigid guide having a telescopic structure, which allows the pelvic area to be stabilised and the affected lower limb to be aligned perfectly, the lower distal end of the guide having a T-shaped ankle band, thereby completing the immobilising function of the assembly; (ii) a system for securing two padded anatomical bands having a longitudinal multi-tunnel system containing a viscoelastic layer on a rigid laminar endoskeleton, which runs parallel to the limb to be immobilised (and consequently, to the rigid central guide of the device), thus providing vertical rigidity and horizontal flexibility, and which allows the telescopic guide to be secured to the body of the injured person, encircling same, and the pelvic area to be immobilised with both lower limbs en bloc; (iii) a series of straps with quick-action fastening that complete the function of the bands into which they are inserted, allowing both opposite ends to remain duly connected and secured; (iv) an internal mechanism which - by means of manual actuation - facilitates the "mechanical" retraction and extension of the telescopic or mobile element of the guide and the consequent adaptation of the ankle band of the device to the specific anatomy of each injured person, and allows the millimetre-scale traction of the affected lower limb in cases of femoral fracture and fracture of the tibia proximal to the knee.