A prosthesis is an artificial device designed to replace a missing body part and restore function. The need for a prosthesis can arise through disease, such as diabetes, congenital birth disorders or from trauma. There is a broad range of body parts for which a prosthesis can be made. In the personal injury field the most common prostheses are made to replace upper or lower limbs. These devices should be custom built for the individual, depending on their level of amputation and functional needs. An orthosis is also a custom-made device designed to restore function but it sits alongside a body part rather than replaces it. Orthotics can help maintain stability and enhance function in a residual limb after amputation surgery. Modern prosthetics are of lightweight construction made from titanium, plastics and composites.