Hip replacement failure

There are two reasons why a hip replacement can fail.

Wear of materials (aseptic loosening)

This is the main cause of revision of a hip prosthesis, especially in the medium and long term and occurs when the prosthesis has failed to fix properly, either because the cement mantle has failed or because there is an absence of adequate bone growth. around the implant when the prostheses are uncemented.

The reason why this loosening occurs depends on many factors. For example, in cementless prostheses, if adequate stability is not achieved when performing Primary Fixation, abnormal micromotion around the implant may occur, which in the long term will cause loosening and cause pain to the patient. For cemented prostheses, the factors that can influence loosening range from an inadequate cementation technique to the wear of the polyethylene with the consequent inflammatory reaction to its particles.

The main symptom that is evident in these patients is the pain that appears when making movements in which the prosthesis is used. When the loosening is severe enough, the pain stops being mechanical and becomes chronic, since it is felt all the time due to the inflammation caused by prosthetic instability. Another important symptom is the sensation of "failures", as if the Osteoarthritis (Osteoarthritis) had returned generating instability. This occurs because as the joint movement capacity decreases, the muscles lose trophism.

Periprosthetic hip infection (septic loosening)

This is one of the prosthesis failures most feared by Joint Surgeons and patients because its treatment is complex, long and has repercussions on the lives of patients. When we perform a partial or total hip replacement we are implanting an inert element crossing the natural protective barrier that is the skin. It harbors bacteria that coexist with us without harming us by remaining on its epidermal surface. In this process of making the surgical wound and implanting the prosthesis, bacteria or fungi can enter that cause the infection of the same. It should be clarified that with any surgical procedure, there is a risk that these types of germs may enter deep down. We take multiple preventive measures so that this does not happen, and maintain a frequency of presentation of this complication as low or lower than the world average, however, it will hardly or never be possible to have total control of the variables that can generate this complication, therefore it will surely never be achieved that in absolutely all cases it can be avoided.

These microorganisms can reach the surface of the implant and create a perfect environment to protect themselves from the immune system and thus create an infection that is impossible to eliminate without removing it in most cases, especially chronic ones, or that are caused by the entry of germs to the joint from infections in other regions of the body and that reach the bloodstream.

Infections are manifested mainly during the immediate postoperative period with pain, inflammation outside the parameters, fever and with material coming out of the surgical wound, even managing to develop septicemia. There is also progressive pain that prevents the patient from progressing in his recovery. With some frequency the patient presents a small round or punctate wound that constantly drains in chronic cases.

There are three types of hip replacement infections:

• Acute infection of hip replacement: It occurs within the first 6 weeks postoperatively. Contamination occurs during surgery. It manifests in the first days with pain, redness of the wound, persistent serous drainage or purulent in some cases.
• Chronic hip replacement infection:It occurs when the infection has been present for more than 6 weeks. Contamination can be originated in the operating room during the first year, however they are usually infections originating in other regions of the body, and the contaminating germ is not so aggressive so the immune system can keep it partially controlled. The patient manifests progressive pain, almost always nocturnal, and there is a loosening of the prosthesis that worsens the symptoms.
• Hematogenous infection of the hip replacement:It can occur at any time. Contamination does not occur in surgery, the prosthesis has usually been working well for some time and there is a rapid onset of pain and fever associated with a distant focus of bacteremia (active infection with dissemination of bacteria to the blood), such as example a dental or skin abscess.

It is generally managed with at least two surgical times, one consists of removing the prosthesis, performing extreme cleaning and debridement of the residual tissues in the joint, and after this, using an implant that consists of bone cement with local release antibiotic, and that provides temporary joint stability called a Spacer. To this is added a management with antibiotics that ideally should be directed to the germ or germs identified for a period that generally ranges from 6 to 12 or more weeks, part of it being hospitalized, the other by oral intake. In the second phase, once infection eradication parameters have been verified, a new reimplantation is carried out. All based on the set of evolution of the pathology and characteristics of each patient, seeking to achieve the best quality of life.

Usually, each procedure that is performed is more complex, has a greater risk of complications, and the functional result is not the same as the first time the prosthesis is received and it has not had any complications. However, in the vast majority of cases a good quality of life is achieved, and a preservation of the limb. In a few cases, the patient may require an amputation of the limb, or a management of the infection with the intake of antibiotics throughout life will be decided, according to each particular case and the specialized concept.

In either case, the only treatment is hip revision surgery. During this surgery, an exploration of the state of the prosthesis and the bone is performed to define the steps to be carried out. It may need to be performed in several surgical stages until the replacement of the prosthesis in the hip.