THE MINIMALLY INVASIVE HIP REPLACEMENT
Hip replacement is a major orthopedic surgery which consists in replacing the hip affected by hip osteoarthritis.
The surgery involves the prosthesis of the entire joint, through the implantation of two titanium components which are anchored to the patient’s bone without the aid of cement, as opposed to the knee prosthesis.
There are 3 types of hip prostheses: the total prosthesis, or joint prosthesis, in which both the femur and the acetabulum are replaced; partial prosthesis, or endoprosthesis, in which only the head of the femur is replaced (usually when a fracture of the femoral neck occurs in an elderly patient); the resurfacing prosthesis, in which both the femur and the acetabulum are replaced but the neck of the femur is spared (this is a surgery reserved for selected cases, that is, young and sports patients with advanced osteoarthritis).
In some cases, the hip prosthesis can also be cemented: these are selected patients suffering from severe osteoporosis. The choice of which prosthesis to use depends on the characteristics of the patient and the quality of his bone. Generally in elderly patients and patients with osteoporosis it is preferred to perform cemented prostheses, which have the advantage of immediately fixing the prosthesis to the bone and allowing for an early and complete load. Non-cemented prostheses, on the other hand, are considered biological as they are coated with a material that allows osseointegration by the patient, whose bone envelops and penetrates inside the holes of the prosthetic surface.
The minimally invasive technique in hip replacement
The minimally invasive hip prosthesis provides for a posterolateral access (in reality there are several minimally invasive access routes) with passage through the gluteal muscles, without however dissecting them; only one tendon is sacrificed, the piriformis, which at the end of the surgery is repositioned in its original site with resorbable points. The intervention also provides for the saving of a part of the femoral neck and the use of prostheses with short femoral stems. Thanks to the “Femur-First” technique, it is also possible to obtain satisfactory results by positioning the prosthetic components in such a way that they have an optimal working angle, guaranteeing a longer life of the polyethylene insert and a lower risk of implant dislocation.
Which prosthesis to choose?
The choice of the prosthesis depends on various factors, including the age of the patient and his functional requirements, but above all the geometry of the hip. In fact, there are different types of prostheses that allow you to faithfully reproduce the geometry of that particular patient. In fact, not all hips have the same shape, and each patient has his own geometry: the purpose of each hip prosthesis is to try to reproduce the original anatomy as much as possible.
For this purpose, there are several methods, both for choosing the type of prosthesis and its dimensions. Surely the computer is one of the most evolutionary and precise methods. There is a software called Osirix, which allows you to calculate the geometry of the hip on the basis of the patient’s X-ray, and thanks to a known metal landmark it is able to tell us if the chosen prosthesis reproduces the anatomy and geometry, the final length of the lower limbs and the sizes of the prosthesis.
